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I HC QUC GIA H NI
I HC KHOA HC T NHIN
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PHM TH DINH
NGHIN CU BIN TNH PH PHM T CY AY
LM VT LIU X L MT S KIM LOI N O C
LUN V HC S KHOA HC
H Ni 2015
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I HC QUC GIA H NI
I HC KHOA HC T NHIN
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Phm Th Dinh
NGHIN CU BIN TNH PH PHM T CY AY
LM VT LIU X L MT S KIM LOI N O C
: K thut mi trng
: 60520320
LUN VN TH S KHOA HC
NGI HNG DN KHOA HC: PGS.TS. QUANG HUY
H NI 2015
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L I CM
Li u tin, vi lng bit n v s knh trng su sc, ti xin chn thnh
cm n PGS.TS. Quang Huy, B mn Cng ngh Mi trng, Khoa Mi trng,
Trng i hc Khoa hc T nhin giao ti v trc tip hng dn, tn tnh
gip ti trong sut qu trnh thc hin lun vn. Cm n thy rt tm huyt
ch dn v gp ti hon thnh lun vn ny.
Ti xin chn thnh cm n cc thy c thuc B mn Cng ngh mi trng,
B mn Th nhng v mi trng t, Khoa Mi trng, Trng i hc Khoa
hc T nhin, i hc Quc gia H Ni to mi iu kin thun li ti c th
hc tp v lm vic trong sut thi gian nghin cu.
Ti xin cm n ti ThS. Bi Trung Thnh, Trung tm Nghin cu cng ngh
x l mi trng, B Quc phng cng tc trong qu trnh thc hin ti.
Ti cng xin gi li cm n ti gia nh, bn b lun quan tm ng vin v
ng gp kin gip ti trong sut qu trnh hon thin lun vn.
Xin chn thnh cm n!
H Ni, thng nm 2015
Hc vin
Phm Th Dinh
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MC LC
LI C N ............................................................................................................. i
DANH MC BNG ................................................................................................. iv
DANH MC HNH NH ........................................................................................ iv
DANH MC CH VIT TT................................................................................ vii
M U ..................................................................................................................... 1
Chng 1 TNG QUAN ....................................................................................... 3
1.1. X l kim loi n tro c bng vt liu c ngun gc thc vt ............... 3
1.1.1. Hin trng nhim kim loi nng trong nc ................................................. 3
1.1.2. X l kim loi nng trong nc bng sinh khi thc vt ................................. 5
1.2. c im sinh hc ca c a ........................................................................ 22
1.3. Tnh hnh sn xut a tr to t gii ......................................................... 23
1.4. Cc mi trng ca c a v sn phm t a ........................... 25
1.5. Tim s dng ph phm c a l m vt liu x l nhim mi trng
.......................................................................................................................... 27
Chng 2 - I V PH PHP HI CU ...................... 30
2.1. i tng nghin cu......................................................................................... 30
2.2. P p p i cu .................................................................................... 30
2.2.1. Phng php bin tnh vt liu ....................................................................... 30
2.2.2. Xc nh c tnh c bn ca vt liu ............................................................. 34
2.2.3. Kho st kh nng hp ph ion kim loi nng ca vt liu bin tnh........ 36
Chng 3 - KT QU NGHIN CU V THO LUN ................................. 37
3.1. c t c bn ca bt t a ....................................................................... 37
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3.1.1. c im hnh thi b mt ca bt thn ay .................................................. 37
3.1.2. c im cu trc ca bt thn ay ............................................................... 38
3.1.3. c im lin kt, nhm chc ......................................................................... 39
3.2. Quy trnh bin tnh to vt liu amidoxime ha t bt t a ....................... 40
3.2.1. X l bng dung dch NaOH ........................................................................... 40
3.2.2. ng trng hp ghp acrylonitrile ln bt thn ay bng h khi mo natri
bisunphit/amoni pesunphat (SB/APS) ............................................................ 45
3.2.3. Phn ng amidoxime ho ................................................................................ 52
3.3. c tnh ca vt li bin tnh ....................................................................... 56
3.4. Kh x l kim loi nng (Cu2+
, Zn2+
, Ni2+
) ca vt li bin tnh ....... 60
3.4.1. Xc nh gi tr pH x l ................................................................................. 60
3.4.2. Xc nh cc h s hp ph ca vt liu bin tnh vi cc ion KLN ......... 60
3.4.3. Xc nh thi gian lu ti u cho qu trnh x l ion KLN (Zn2+
, Ni2+
, Cu2+
)
bng vt liu bin tnh ............................................................................... 65
KT LUN V KHUYN NGH ......................................................................... 67
TI LIU THAM KHO ...................................................................................... 69
PH LC ................................................................................................................. 76
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DA H MC B
Bng 1. N kim loi n tro c thi ca mt s c s sn xut ............... 4
Bng 2. Di tc , s t v s l a t ca tnh Long An ....................... 24
Bng 3. Di tc , s t v s l a c ca tnh Long An ..................... 25
Bng 4. Thnh ph di dng c trong cc b phn ca c a ......................... 26
Bng 5. ng ca cc iu kin phn n kh p AN l bt thn
a ................................................................................................................ 33
B 6. P p p xc nh mt s tnh cht vt l, ha hc ca vt liu .......... 35
Bng 7. Kt qu xc d lng hp ph ca vt liu ..................................... 61
Bng 8. Cc h s hp ph ng nhit ca vt liu vi Zn2+
, Ni2+
v Cu2+
.............. 63
DA H MC H H H
H 1. c ph hy enzym ca kim loi nng ..................................................... 3
Hnh 2. Cu trc vch t bo v mt ct ngang vi si ................................................. 6
Hnh 3. Cu trc ca phn t cellulose ....................................................................... 7
Hnh 4. Cu trc phn cp ca cellulose ..................................................................... 7
Hnh 5. Vng tinh th v v v nh hnh ca cellulose ......................................... 8
Hnh 6. Cu trc ha hc ca cc hp cht chnh ca hemicellulose ......................... 9
Hnh 7. Cu trc ha hc ca lignin .......................................................................... 10
Hnh 8. Phn ng este ha gia cellulose v axit xitric ............................................ 17
H 9. S cc p p p bin tnh polyme .................................................... 18
Hnh 10. Cc nhm chc ghp ni vo cellulose to vt liu c nhi c tnh tt.......21
H 11. a (Hibisc s a abi s) ................................................................. 23
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Hnh 12. T trng sn xut a tr t gii ............................................................ 24
Hnh 13. V tr cc nh nhiu x c tr ca cellulose I (a) v cellulose II (b)
trong ph nhiu x tia X ............................................................................ 31
Hnh 14. nh SEM b mt bt t a ................................................................... 37
Hnh 15. Ph nhiu x tia X ca bt t a ........................................................... 38
Hnh 16. Ph hp th hng ngoi ca bt t a .................................................. 39
Hnh 17. ng ca n NaOH n khi lng cn li v m lng
cellulose trong bt t a ....................................................................... 40
Hnh 18. Ph nhiu x tia X ca bt t a ba u v x l cc n dung
dch NaOH khc nhau ................................................................................ 41
Hnh 19. S bi i ch s tinh th ca cellulose trong bt t a k i x l vi
dung dch NaOH cc n khc nhau ............................................... 42
Hnh 20. Ph hp th hng ngoi ca bt t a ba u v x l cc n
NaOH khc nhau ........................................................................................ 43
Hnh 21. ng ca t l SB/APS n kh p AN l bt t a .... 46
Hnh 22. ng ca tng n h k i m o n kh p ca AN ln
bt t a ................................................................................................ 48
Hnh 23. ng ca t l khi l AN/a n kh p AN ln bt
t a ...................................................................................................... 49
Hnh 24. ng ca thi gian phn n kh p AN l bt thn
a .............................................................................................................. 50
Hnh 25. ng ca nhit n kh p AN l bt t a ............ 51
Hnh 26. ng ca n NH2OH.HCl ....................................................... 52
Hnh 27. ng ca nhit phn ng ............................................................. 53
Hnh 28. ng ca thi gian phn ng ............................................................ 54
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Hnh 29. Quy trnh bin tnh to vt liu amidoxime ha t bt t a ............... 55
H 30. c im hnh thi b mt ca bt t a ba (a), a x l bng
NaOH 15% (b), a p AN (c) v vt li bin tnh (d) .............. 56
Hnh 31. Ph hp th hng ngoi ca bt t a ba u (a), sau x l NaOH
15% (b) v ghp AN (c) ............................................................................. 57
Hnh 32. Ph hp th hng ngoi ca vt liu .......................................................... 58
Hnh 33. Th zeta ca bt t a ba u, sau x l NaOH 15% v vt liu ....... 59
H 34. in tch m b mt ca vt li bin tnh cc pH khc nhau ................. 60
H 35. P tr p ph ng nhit Freundlich (a) v Langmuir (b) ca vt
liu vi Zn2+
, Ni2+
v Cu2+
......................................................................... 62
Hnh 36. Phn ng to phc gia vt liu amidoxime ha v ion Cu2+
................... 64
Hnh 37. Cc phn ng to thnh vt liu amidoxime ha v phn ng to phc gia
vt liu vi cc ion KLN ............................................................................ 64
Hnh 38. Phc cht gia hai nhm chc amidoxime v ion KLN ............................ 65
Hnh 39. Hiu sut x l kim loi (Zn2+
, Ni2+
, Cu2+
) theo thi gian ca vt liu ..... 66
file:///J:/MAST%20DINH/Mast%20-%20Dinh%20-%2012.1.16.%20final%20%20m,.doc%23_Toc440369513
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DA H MC CH VI
AAS : P p p p tch ph hp th nguyn t
AN : Acrylonitrile
FTIR : P p p p tc p hp th hng ngoi
KLN : Kim loi nng
PAN : Polyacrylonitrile
R/L : T l rn/lng
SEM : Knh hi vi in t qut
TCVN : Tiu chun Vit Nam
v/p : Vng/pht
X-ray : P p p iu x tia X
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M U
Qu trnh cng nghip a t a tr thnh nhn t tch cc i vi
pht trin kinh t x hi ca t c. Tuy nhin, bn cnh nhng li ch m n
mang li, s ia t cc ot ng cng nghip cn sn sinh rt nhiu cc cht thi
c c t cao, tc ng tiu cc n sc khe co i v h sinh thi.
Kim loi nng (KLN) v nhng hp cht ca c c bit cc
cht c tn ti l d i tro mi trng v c kh tc l tro c t sinh
vt. dng vt, chng c th l cc nguyn t vi lng rt cn thit c o c t con
i. Tuy nhin, khi n cao, cc ion KLN li c t c, c th gy ri ro
l d i co i v h sinh thi. Nh tc ng cp tnh do KLN t ng biu
hin nhanh khi tip xc v t ng gy t t n h h hp, tim p nhanh,
suy thn v thm ch gy t vong. Khi nhim v o c th, KLN tch t trong cc m
v gy ra nhng bi i.
C nhi p p p x l c thi cha KLN p p p kt ta
ha hc, trao i io , in ha, hp ph sinh hc, c p p p u c
c im v phm vi ng dng khc nhau. Tuy nhin, cc cng ngh ny yu
cu phi b sung ha cht nn gy nhim th cp hoc gi thnh cao. V vy, vic
lm cp thit l tm ra p p p x l hiu qu v kinh t .
Vic nghin cu s dng cc vt liu t i x l KLN tro c rt
c quan tm trn th gii. l ng nghin cu nhm to ra p p p x
l in, thn thin vi mi trng v b sung t ha cht v gi thnh ph hp.
Vit Nam l mt c c t trng sn xut nng nghip cao, lng ph phm d
tha trong qu trnh ch bin cc sn phm nng nghip l rt ln. Cc ph phm
t ng b b li, thm c l t ngay ti rung gy hu qu nghim tr n
mi trng v n cc v nhn sinh x hi khc.
Vit Nam, khng c nhiu nghin cu v ti ch ph phm nng nghip,
tro c p phm t c a to ra vt liu x l KLN tro c.
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p v o ng nghin cu tim , ti c n v thc hi ti Nghin cu
bin tnh ph phm t cy ay lm vt liu x l mt s kim loi nng trong nc.
ti c tin hnh vi cc mc c bin tnh ph phm t c a x
l mt s ion KLN (Cu2+
, Ni2+
, Zn2+
) tro c. Ni dung nghin cu tp trung
vo mt s v sau:
- Kho st cc yu t nh hng n qu trnh bin tnh bt g thn cy
ay theo phng php amidoxime ha,
- Kho st cc c tnh c bn ca bt thn ay v vt liu bin tnh,
- nh gi kh nng x l KLN (Cu2+, Ni2+, Zn2+) trong nc ca vt liu
bin tnh.
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Chng 1 QUA
1.1. X l kim loi nng trong nc bng vt liu c ngun gc thc vt
1.1.1. Hin trng nhim kim loi nng trong nc
Thut ng kim loi nng ch nhng nguyn t kim loi c t trng l 5
g/cm3. Kim loinng tn ti tro c c ngun gc t nhin v nhn to. Theo
ngun gc t nhin, kim loi n i v o tro c do qu trnh phong ha. Bn
cnh qu trnh t nhin, hot ng ca co i p mt ph k gy
nn nhim kim loi n . Tro , c thi t cc k d c, l , s
dng phn bn ha hc, thuc bo v thc vt trong nng nghip, hot ng khai
k o , c thi cng nghip l nhng ngun gy nhim c . c bit, tnh
trng nhim KLN do c thi cc ngnh cng nghip a l mt v mi
trng trn th gii. Cc kim loi ng (Cu), niken (Ni), ch (Pb), thy ngn
(Hg), crom (Cr) v km (Zn) l nhng kim loi t c c tro c thi.
Kim loi nng khng phn hy sinh hc, k c khi dng nguyn t t do
im cho sinh vt sng khi dng cation do kh n kt vi
cc chui cacbon ngn. Mt s kim loi n c tm th tro c t v thit
yu vi sc khe ca co i st, km, ma a , ng, ... Tuy nhin, mc
tha cc nguyn t thit yu ny c th nguy hi i sng sinh vt. Cc kim loi
n t ng tch t tro c, t, trm tch v sinh vt; gy nhim mi trng,
i sng ca cc loi sinh vt v sc khe co i.
V mt sinh ha, cc kim loi nng c i lc vi cc nhm -SH- v nhm -
SCH3- ca cc e z m tro c t (Hnh 1). V th cc enzym b mt hot tnh v
lm cn tr qu trnh tng hp protein ca c t .
Hnh 1. C ch ph hy enzym ca kim loi nng
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Bng 1. Nng kim loi nng trong nc thi ca mt s c s sn xut [4]
TT K hiu mu Ni
(mg/L)
Zn
(mg/L)
Cu
(mg/L)
Cr(III)
(mg/L)
Cr(VI)
(mg/L)
Pb
(mg/L)
Fe
(mg/L)
1 N1 5,9 7,2 61,2 68,1 71,5 109,5 - 2282,4 24300,0 0,8 1,9 121,1 159,1
3 N2 - 38,5 - - - - -
4 N4 16,9 - 1,89 - - 0,3 0,75
5 N5 73,4 75,5 - - - - - -
6 N6 - 131 - - 2,24 9,8 1,5
7 N7 21,23 12,54 - 116,2 42,4 12,5 -
8 N8 2,29 64,64 - 18,7 - 3,2 -
9 N9 8,17 10,52 - - - - -
10 N10 - 76,5 - - 15,98 - 40,21
QCVN 40:2011/BTNMT ct B 0,5 3 2 1 0,1 0,5 5
Ghi ch:
N1: Cng ty TNHH KYB Vit Nam, c thi b m (12/10/2009)
N2: Cng ty TNHH sn xut ph t t xe m VAP H Y , c
thi trc h thng x l (7/12/2004)
N3: Cng ty OMIC Hi D , c thi c a x l (22/11/2006)
N4: Khu cng nghip Ni B i, c thi ti cng chung (9/11/2005)
N5: Cng ty TNHH Khi H , c thi cng chung (27/9/2003)
N6: s m T Q a x T a T , H T , H Ni (28/10/2003)
N7: s m Tr V Hng x Thanh Thy, H Ty, H Ni (28/10/2003)
N8: Lng St, Hi D , c thi sau cng on ra m (11/11/2003)
N9: Cng ty m i S T , c thi m km (24/3/2003)
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Cc lng ngh ia c c k , c, m, ti ch v ch tc kim loi c lng
c thi khng l , li cha nhiu kim loi n Z , Fe, r, Ni,...
N cc kim loi n 2+
, Pb2+,
As2+
, Cd2+
, Hg2+
tro c h Thanh
Nhn v h Trc Bch, H Ni vt TCVN 6774:2000 v Cht l c - Cht
l c ngt bo v i sng thy sinh [5].
ng v cc hp cht ca c c c coi l cht c i vi ng vt,
c bit l vi c. i vi thc vt, c coi l nguyn t c bn cn thit cho
s pht trin ca cy tr tro mt s trng hp n li l nhn t c
khi n tro c kho 0,1 m /L. i vi c t i, n ng trong
c ung kho 3 m /L c t vi m v s ng thc qun, nn ma,
thn kinh co git, mch yu, [6].
Km tn ti tro c dng ha tan s rt nguy him n sc khe con
i. Khi ng c km s b a bng, mch chm, co git. i vi cc loi thy
sinh, n Zn2+
bng 0,3 mg/L s gy cht mt s lo i c c ngt [4].
N Ni2+
cao t p i, mi v x . N im c Ni2+
cp tnh
a u, chng mt, bu v a c, kh th, tiu chy, ph thn, vim
da, [4]
c p g php ph bi x l kim loi n l p p p i ma,
trao i io , in phn, kt ta, sinh hc, hp ph bng than hot tnh, Hu ht
cc p p p c c i p cao v t ng c hiu qu khi n ion kim
loi thp. P p p p ph loi b cc ion kim loi tro c c xem l
p p p iu qu cao v chi ph thp [36]. Cc cht hp ph c th l khong
cht, cht h c oc c ngun gc sinh hc.
1.1.2. X l kim loi nng trong nc bng sinh khi thc vt
1.1.2.1. c im ca nguyn liu sinh khi thc vt
Sinh khi thc vt (vt liu lignocellulose) l polyme cacbo irat phc tp,
c thnh phn chnh l cellulose, lignin v hemicellulose [23]. Vt liu
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lignocellulose c th tm thy trong cht thi nng nghip, nng nghip v cng
nghip m ca, b ma, giy vn, c, thn v l cy, v tru, ng, ...
Lignocellulose l phn chnh hnh thnh nn vch t bo thc vt. Lin kt gia
cellulose, hemicellulose v lignin qua lin kt este v ete lm cho sinh khi c tnh
bn vng [31]. Cc vi si cellulose c bao quanh bi hemicellulose to thnh
mt m li m, m khong khng gian tr c lp y bng lignin (Hnh 2).
Hnh 2. Cu trc vch t bo v mt ct ngang vi si
Cc thnh phn ca sinh khi khc nhau ty thuc v o cc lo i v iu kin
mi trng sng. Thnh phn trung bnh tnh theo tr lng ca ba polyme sinh
hc sa : cellulose (30-50%), hemicellulose (19-45%) v lignin (15-35%) [31].
Cellulose l hp cht h c c c t c cu to (C6H10O5)n v l mt
polyme mch thng ng nht gm cc phn t glucose lin kt vi
nhau bi lin kt -1,4-glicozit v lin kt hydro ni phn t v gia cc phn t
[34]. Mi v lp li trong cellulose cha hai phn t anhydroglucose (AGU).
Mi v lp li c mt nhm hydroxyl (OH) chnh cc v tr cacbon 6 (C6) v
hai nhm hydroxyl th cp ti v tr 2 v 3. v lp li th hai xoay 180o
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trong mt phng (Hnh 3). Cellulose c nhi m a c hydrox l t ta
tro c do lin kt ni phn t v lin phn t mnh.
Hnh 3. Cu trc ca phn t cellulose
trng hp ca cellulose l 300 - 1700 vi si g; 800 - 10000 vi cotton,
si thc vt v cn ph thuc vo cellulose gc a q a x l [23].
Hnh 4. Cu trc phn cp ca cellulose
Cc si cellulose nm thnh t bo thc vt v c to nn bi cc vi si
(Hnh 4). Cc b vi si cha 30 - 40 mch cellulose t eo cc ng khc nhau v
c hnh thnh bi cc i phn t cellulose dng tm [33]. Cc mch cellulose
c lin kt vi nhau nh lin kt hydro v lin kt Van Der Waals. Do thiu
chui bn hoc chui nhnh, cellulose l mt polyme bn tinh th, cha c pha tinh
th v p a v nh hnh [28] (Hnh 5). Lin kt hydro gia cc chui cellulose v
lc Van Der Waals gia cc phn t glucose d n s hnh thnh vng tinh th.
Trong vng tinh th, cc phn t cellulose lin kt cht ch vi nhau, vng ny kh
b tn cng bi enzym c a c t. Ch c cc mch cellulose trn b mt cc
vi si l d dng tip xc vi ha cht. Do , p n ng thy phn ca cellulose l
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rt thp [31]. N c li, tro v v nh hnh, cellulose lin kt khng cht vi
nhau nn d b tn cng [14]. t k p n ng ca cellulose, cc vng
tinh th ca cellulose c c chuyn sang d v nh hnh. Vi mc c ,
mt s qu trnh thy phn b p p p a c c nghin cu.
Vng v nh hnh
Vng tinh th
Hnh 5. Vng tinh th v vng v nh hnh ca cellulose
Cellulose c hai dng tinh th l cellulose I v cellulose II [28]. Cellulose I
c cc chui cellulose sp xp song song vi nhau, trong khi cc chui cellulose II
i song vi nhau. Cc d v nh hnh ca cellulose l dng III v dng IV.
Cellulose I t ng c trong cellulose t nhin. Trong cellulose I c hai loi lin kt
hydro: lin kt hydro ni phn t v gia cc phn t [28]. Lin kt hydro ni phn
t gm hai loi: O-2-HO-6 c di lin kt l 2,707 v O-3-HO-5 c di
lin kt l 2,802 . Lin kt hydro lin phn t gia C6-OH v C3 (O6 - HO3) c
di lin kt 2,874 [49]. Cu trc ny rt bn nhit v c th c chuyn sang
cc dng cellulose khc [28, 14]. Cu trc tinh th ca cellulose I c th chuyn
sang dng cellulose II thng qua qu trnh x l bng kim.
Hemicellulose l mt polysaccarit c tnh cht ha hc khc nhau gia cc
loi thc vt, c hnh thnh bi pentose (xylose, rhamnose v arabinose), hexose
(glucose, manose v glactose) v cc axit uronic (4-Omethyl-glucuronic, v
galacturonic) [34]. Xylan polyme l loi polyme ph bin nht trong hemicellulose.
Hemicellulose bao hm cc lin kt (1-4) khng phn nhnh ca xylan hoc
mannan, chui xon c li kt (1-3), chui p li kt (1-4)
galactoglucomannan (Hnh 6). Kt qu hnh thnh chui polyme phn nhnh m
ch yu gm cc mo ome m cacbo (x lose) v ng su cacbon
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(glucose). Hemicellulose khng c cu trc tinh th, cu trc phn nhnh cao v c
cc nhm axetyl kt ni cc chui polyme vi nhau [23].
a) Xylan
b) Glucomannan
Hnh 6. Cu trc ha hc ca cc hp cht chnh ca hemicellulose
Hemicellulose k a ta tro c nhit thp. Tuy nhin, qu
trnh thy phn ca cao so vi cellulose [23]. Hemicellulose tan nhi
trong dung dch axit. H m lng hemicellulose trong g mm v g cng khc nhau
k. Hemicellulose lm gim kh tip cn cellulose, do , cn phi tch
ti thiu 50% hemicellulose t k ca cellulose [34]. So vi cellulose,
hemicellulose d dng b thy phn trong axit long, kim hoc e z m. Do nhy
nhit cao, qu trnh thy phn hemicellulose to ra cc sn phm ph khng mong
mu f furan v hydroxymetyl fufuran.
Lignin l mt hp cht c cu trc phn t phc tp cha polyme lin kt
ngang ca cc p p e olic, c bit l p-coumaryl ancol, coniferyl ancol,
sinapyl ancol (Hnh 7).
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Hnh 7. Cu trc ha hc ca lignin
Li i c vai tr mt mng bo v tnh thm ca t bo v c n s
xm nhp ca vi khun. V c bn, cc loi thc vt g mm cha m lng lignin
cao so vi cc loi sinh khi thc vt k c, do q tr tc cellulose t
thc vt g mm t k k so vi cc sinh khi k c. Do , loi b
lignin cn phi thc hin cellulose v hemicellulose c tip xc vi dung
dch x l [31].
Vt liu lignocellulose l ngun ti nguyn ti to, c th s dng trc tip
hoc gin tip sn xut cc kh sinh hc hoc cht ha hc, vt liu x l [3].
Mt cht hp ph c coi l c chi ph thp nu n phong ph trong t nhin v l
ph phm nng nghip, cng nghip [47]. Ngun cht thi t sinh khi thc vt c
gi tr kinh t thp. Tuy nhin, cc ng dng ca ngun ti nguyn ny b hn ch
bi lin kt cht ch gia ba thnh phn chnh ca thnh t bo l cellulose,
hemicellulose, lignin.
-
11
1.1.2.2. s ca p p p
Ph phm nng nghip t ng gm cc thnh phn cellulose, hemicellulose,
lignin, lipid, protein, cc loi , ti bt, c, hidrocacbon, tro. Nhng
vt liu ny c kh p ph kim loi nng nh cu trc nhiu l xp v thnh
phn gm cc nhm chc hot ng [3]. Cc nhm chc trong sinh khi bao gm
nhm axetamido, cacbonyl, phenolic, khung polysaccarit, amin, sunphua hydryl,
cacboxyl, ru v este [19]. Cc nhm ny to i lc v to phc vi ion KLN. Mt
s vt liu hp ph lin kt khng chn lc, c th lin kt vi nhiu ion KLN.
Trong khi, cc vt liu khc lin kt chn lc ion KLN ph thuc vo thnh phn
ha hc ca chng. Cc ph phm x da, tru, b ma, l c c , c d
x, t c , thn cy chui, v tr , t c ,... c nghin cu
nhm pht hin kh tc kim loi n tro c.
Trao i io l c c quan tr i vi qu trnh x l ion KLN bng thn
c o c tm thy trong nghin c c b [25]. Sau khi hp ph Cu2+
,
Ni2+
, Pb2+
v Cd2+
, kt qu phn tch cho thy cation Ca2+
, Mg2+
, K+
v H+
c
tch ra khi vt liu c t l g t vi ion kim loi c x l. iu
ny chng t cc ion KLN t a t v tr ca cc cation khc trong vt liu.
P tr p n trao i io sa :
S M2/n + Me2+
S Me + (2/n) Mn+
(1)
Tro , S l v tr lin kt, Mn+
i din cho ion K+, Mg
2+, Ca
2+ v Me
2+
i din cho cc ion KLN.
C d x cha phn h c c yu l lignin, cellulose v mt s nhm
chc phn cc [52]. Nhng nhm chc ny c kh trao i cation hoc to
lin kt ha hc. Phn ng hp ph trao i gia Cu v sinh khi d x c th
biu di t eo p tr sa :
2(TF)- + Cu
2+ Cu(TF)2 (2)
2H(TF) + Cu2+
Cu(TF)2 + 2H+ (3)
-
12
Tro , (TF)- v (TF) l nhng v tr phn cc c th t tc vi cc ion
kim loi trn b mt vt liu t sinh khi d x.
Ion KLN tn ti mt s dng trong dung dc e2+
, MeOH+,
Me(OH)2, Cc ion kim loi tn ti trong dung dch axit cc dng cation.
Trng hp , c c ch y l trao i ion. Ti pH cao, cc ion kim loi s kt
ta, do , iai o , c c hp ph b mt chim t . c c c ny
c th hin qua cc p tr sa [10]:
2(R-COH) + Me2+
(R-CO)2Me + 2H+ (4)
R-COH + MeOH+ R-COMeOH + H
+ (5)
2R-COH + Me(OH)2 (R-COH)2Me(OH)2 (6)
Tro , R l cc gc trong vt liu.
N c , c c hp ph ion KLN bng ph phm nng nghip da trn
phn ng ha hc gia cc nhm chc trn b mt cht hp ph v ion kim loi.
Phn trao i cation v phn ng to phc vi ion kim loi l ch yu. Bn
cnh , cc c c xy ra km theo bao gm hp ph b mt, khuch tn, kt ta.
im ca vic s dng ph phm nng nghip x l c thi bao
gm k thut in, kh p ph tt, hp ph chn lc ion kim loi nng,
chi ph thp, tnh sn c v d dng ti sinh. Tuy nhin, vic p dng cc cht thi
t sinh khi thc vt c a c x l c th mang li mt s v l m t
OD, BOD c TO tro c do s ha tan ca cc cht h c d ha tan
trong thc vt [47]. S ia t OD, BOD v TOC ca c c th gy ra s suy
gim oxi tro c, d e da i sng th si . Do , vt liu c
ngun gc thc vt c c x l trc khi hp ph kim loi nng.
1.1.2.3. Mt s p p p iu ch vt liu t sinh khi thc vt
Trong nh m , vic s dng ph phm nng nghip c c
bit quan tm, nhiu nghin c c tin hnh nhm tm ra p p p c n
cc ph phm ny thnh vt liu c ch. Tro , ng nghin cu s dng ph
-
13
phm nng nghip lm vt liu x l KLN tro c l mt trong nh ng c
tim ng dng nht.
Sinh khi thc vt c cellulose c a bin tnh c kh p ph
kim loi nng thp v tnh cht vt l khng nh. khc phc nh im hn
ch ca sinh khi t , cc p p p bi t c p d nng cao hiu
qu x l KLN. Mt s nhm p p p c s dng nhiu nht c phn loi
sa : p p p vt l (xay v nghin, nhit); p p p a c (bin tnh
bng kim, axit, tc nhn oxi ha, dung mi h c); p p p si c; t hp
ca p p p vt l v p p p a c (qu trnh t thy phn, oxi ha
t).
P p p si c c p d phn hy mt phn vt liu
lignocellulose bng cch s dng cc vi sinh vt phn hy lignin v hemicellulose
m v vi khun. im ca p p p l tin hnh d dng v tn t
lng. Tuy nhin, qu trnh phn hy sinh hc din ra chm v cn p dng
t m cc p p p vt l, ha hc k c p p p i c c. Cc
p php vt l in, chiu x, nhit c c p d bi i
tnh cht ca sinh khi thc vt. P p p i l m t din tch b mt v
gim tinh th ca cellulose. P p p c iu x nhm ph v cc lin kt
hidro trong cu trc tinh th ca cellulose b lng bc x. Tuy nhin,
p p p cu phi cung cp lng l . c p p p a c
s dng cc cht ha hc bin tnh vt liu. Mc c ca p p p l
th p emicell lose, li i ng thi t m lng cellulose trong sinh khi
thc vt. P p p bin tnh kt hp p p p vt l v p p p a
hc t c p d v c coi l p p p tt nht.
Hai p p p bin tnh sinh khi thc vt thnh vt liu t c p
dng v nghin c l p p p c to than hot t v p p p bin tnh
b mt.
-
14
a) Ch to than hot tnh
Than hot t c s dng rng ri trong x l cc cht nhim h c v
cc ion kim loi n thp. Cacbon trong thc vt c chuyn ha thnh
cacbon hot ha nhit cao. Than hot tnh c thnh phn ch yu l cacbon
(85-90%), cn li l cc hp cht v c dng tro (5-15%). Than hot tnh c cu
trc l xp. Din tch b mt trong cc l xp chim phn ln tng din tch b mt
ca cacbon [12].
Cht thi nng nghip l ngun nguyn li p o p sn xut than hot
t do c m lng tro thp v cng ph hp [24]. Do , bin tnh cc cht
thi nng nghip thnh than hot tnh l mt gii php gii quyt v mi trng
v gim chi ph ch to than hot tnh. Than hot t c ch to t cht thi rn
nng nghip m ca, c t thi cao l , li ng, b ma, tr , x da,
c s d loi b KLN v x l cht thi dt nhum tro c [12]. Than
hot tnh ch to t ph ph phm nng nghip c hiu qu kinh t cao trong x l
c thi do ngun nguyn liu di do, gi thnh r.
b) Bin tnh ha hc
Mc tiu quan trng ca bin tnh bng cc cht ha hc l to ra b mt m
in hoc i tc d trn b mt ca vt liu [44]. iu ny lm cho
kh p t keo tt v iu ch c tnh b mt ca vt liu.
Cc chui cellulose cha mt nhm hydroxyl chnh v hai nhm hydroxyl
th cp. Cc nhm chc hot c gn vo cc nhm hydroxyl bng cc cht
ha hc [18]. c p p p bin tnh ha hc chnh bao gm: este ha bng axit
h c, oxi a bng cc tc nhn oxi ha, thy phn bng dung dch kim v ghp
cc monome ln sinh khi thc vt. c p p p bin tnh sinh khi thc vt
c th tc c cc hp cht h c a ta v cao iu qu to phc vi
KLN [36]. Lignin c cha nhiu nhm chc drox l t do, nhm metoxyl,
nhm cacbonyl v ni i, do , c t tham gia cc phn oxi a l m t
mch cacbon to thnh axit bo v v t m. c d lignin c kh bn nhit
-
15
tt, nng chy nhit 140 - 160 , d b s im b do tia t oi.
V t m trc k i c to vt li c p i x l si loi b li i .
Hemicellulose c c trc c v , o i ra c mt t t ti v
ti t ca cellulose. V v , d b t p tro d dc axit, d b trc l
k i si tro d dc kim lo , d p p m, c k t p di
tc d ca vi k v l m s im b it ca vt li , t c t c c
km, k b . Bin tnh ha hc khng nhng loi b lignin, hemicellulose m
cn lm gim m lng tinh cellulose tinh th v t xp ca b mt vt liu.
c iu nghin cu v p p p bin tnh vt liu bng cch s dng cc
tc nhn bin tnh k c a cc d dch kim (NaOH, Ca(OH)2, Na2CO3),
cc axit v c (H l, H2SO4, HNO3), cc axit h c (axit tartaric, axit xitric) hay
cc hp cht h c (meta ol, focmalde t), cc tc nhn oxi ha (H2O2, phn ng
Fe to ) x l cc cht h c a ta , mu v hp ph kim loi nng trong
c. Tc nhn bin tnh l m t t ot ng ca b mt vt liu do gn thm
cc nhm chc c kh kt hp vi kim loi nng, loi b cc cht h c d
ha tan c sn trong vt liu.
Bin tnh bng dung dch axit v c
Bin tnh bng dung dch axit l qu trnh ph v cu trc bn vng ca vt
liu lignocellulose. Ion H+ ph v lin kt ni phn t v lin kt gia cc phn t
vi nhau gia cellulose, hemicellulose, lignin trong sinh khi [31]. c axit c
H2SO4, HCl, H3PO4 v HNO3 c p d thy phn sinh khi. Cc nhm
hydroxyl trn cellulose vai tr q a trng v kh trao i ion ca vt liu
lignocellulose. Bn thn nhm ny ny c kh trao i yu v lin kt OH
phn cc khng mnh. Nhiu bin php bi t c cng b oxi a cc
nhm hydroxyl thnh cc nhm chc axit hoc sunfo ha bng axit sunfuric [3].
Tuy nhin, cht thi t qu trnh bin tnh bng axit c c x l do c t c
hi, m . Hu ht cc p p p bin tnh sinh khi thc vt b axit v c
u s dng dung dc axit lo axit H2SO4, HCl v HNO3. Cc axit long c
hiu qu v mt c i p v mi trng. Nhn chung, axit long (H2SO4 < 4%)
-
16
c th ha tan hu ht hemicellulose [31]. Dung dch axit H2SO4 lo l m t tc
phn ng thy phn cellulose. Axit m c l tc nhn oxi ha mnh cho qu
trnh thy phn cellulose c t m v p i thu hi. M ca c x
l bng HCl loi b c 92,4% Cu2+
pH 5, tro k i m ca c loi b c
47% [36]. Tuy nhin, trong mt s trng hp, x l v tru bng HCl li lm gim
kh p ph Cd2+
so vi v tru khng x l b axit. hp ph cc
KLN, b mt cc vt liu hp ph phi ma in tch m. Mc d bin tnh bng
axit lm gim m lng cht h c ca vt liu hp ph v t xp b
mt tc i d vi cc ion H+ c l m cn tr qu trnh hp ph. Khi v tru
c x l bng HCl, cc v tr hp ph trn b mt vt li c proton ha.
Bin tnh bng dung dch kim
Trong thnh phn si thc vt v g c cellulose, hemicellulose, lignin l cc
thnh phn ng l n tnh cht ca si. c c c ca q tr bi
tnh b kim l p v c trc li i tro si k i, l m t mc p
ca cellulose v hemicellulose c o cc bc x l tip t eo. Q tr t p
b d dc kim d d x ra ( it di 140 ) so vi cc p p p
bi t k c [31]. xp ca vt li t l sa k i d dc kim p v cc
li kt c o, to t m i ca axit cacbox lic v r . Vt li c bi t
b d dc kim c b mt m i do cc io H+ trong cc nhm hydroxyl,
cacboxyl, ... c s tr b mt vt li c tc ra tr a io OH- trong
d dc . i l im ca p p p bi t vt li b d dc
kim so vi cc p p p k c. Nhn chung, cc d dc NaOH v a(OH)2,
NH4OH t c s d c o q tr t p b kim.
Bin tnh bng axit hu c
Cc axit h c c tc dng este ha cellulose, g c d l r v v
c hot ha bng axit xitric u c mt s ia t k kh
loi b cc ion kim loi tro c [3]. Axit xitric u tin s chuyn thnh dng
anhydric, tip theo l phn ng este ha xy ra gia axit anhydric v cc nhm
-
17
hydroxyl ca cellulose. Ti v tr phn v x t hin hai nhm chc axit
(t axit xitric) c kh trao i ion. N t it hoc ko di thi gian
phn ng, qu trnh este ha c th tip tc x ra i vi cc nhm axit cn li ca
axit xitric lm gim kh trao i ion.
Hnh 8. Phn ng este ha gia cellulose v axit xitric
Nghin cu v qu trnh este ha bt li ng bng axit xitric cho thy, sau
khi este ha, din tch b mt ca cht hp ph t k [3]. Lng oxi c
tm thy trong vt li t cao do iu nhm oxi a c gn trn b mt vt
li , in hnh l nhm cacboxyl, phenolic v lactonic.
Bin tnh bng dung mi hu c
Bin tnh bng dung mi h c loi b lignin, hemicellulose ra khi vt liu
bng cch solvat ha, ha tan cc mnh v ca lignin, hemicellulose. Cc polyme
lignin d dng tan trong dung mi h c. Qu trnh solvat a c thc hin bi
cc lc gia cc phn t li kt hydro, lc ion-lng cc, lc lng cc, lc
lng cc-lng cc gy ra [36]. c d mi c s d bin tnh vt liu
-
18
c ngun gc thc vt t ng c nhit si thp meta ol, eta ol, axeton,
etylen glycol, etyl axetat. Ion OH- trong ancol s ph v lin kt axit-este trong
lignin, hemicellulose. H a, bin tnh bng dung mi h c c l m cellulose
tr l , do im lng cellulose tinh th. T i , p p p k
kh thi v mt kinh t v i i phi thu hi dung mi h c.
Bin tnh bng tc nhn oxi ha
Mt s tc nhn oxi a t c d bin tnh sinh khi thc vt
thnh vt liu hp ph bao gm ozon, hydropeoxit (H2O2), clo, H l, H lO, Cc
tc nhn oxi ha tham gia vo qu trnh ha tan lignin bng cch ph v cu trc
vng ca lignin. T t ng, tc nhn oxi a c s d h tr cho bin
tnh bng kim. Tro iu kin pH > 12, gc ( O2*) hnh thnh v m v t m
[31]. Lignin, hemicellulose b ha tan thnh axit cacboxylic (axit formic, axit
oxalic, axit axetic); tro k i , cellulose h k b phn hy.
Bin tnh sinh khi thc vt bng phn ng ng trng hp ghp
Hnh 9. S cc phng php bin tnh polyme
-
19
Mt s p p p bi i cc thuc tnh ca polyme bao gm pha
trn (blending), ghp (graft) v che ph (curing) [13]. Hn hp ca hai hay nhiu
monome c pha trn vt l vi a c c cc tnh cht cn thit l qu
trnh pha trn. Ghp l mt p p p tro monome c lin kt cng ha
tr vo chui polyme. Che ph l qu trnh bao ph ca mt lp p t ln mt
chui polyme bng cc lc vt l.
Q tr ng trng hp l qu trnh trng hp hai hay nhiu monome m
sn phm polyme sinh ra c cc mt xch monome sp xp ngu nhin (copolyme
ngu nhin), sp xp l p i n hoc cc mt xch monome khc nhau to
t cc on mch khc nhau trn polyme (copolyme khi) hoc polyme c
nhnh to ra t monome khc loi vi mch chnh (copolyme ghp). Khi trng hp
mt loi mo ome to nn mc v o mt loi polyme c sn, qu
trnh ny gi l ng trng hp ghp, sn phm ca qu trnh l copolyme ghp.
ng trng hp p l p p p t c s dng rng r i bin tnh
ha hc cc polyme t nhin v polyme tng hp. Phn ng trng hp ghp l
mt p p p t c s d bin tnh b mt pol me v t a i cc
thuc tnh vt l hoc ha hc ca polyme. Cc chui b c lin kt cng ha tr
vi trc pol me c hnh mt cht ng trng hp (copolyme). C hai loi
chnh ca p p p p ni l ghp ni vi mt mo ome v p ni vi
mt hn hp ca hai hay nhiu monome. Ghp ni vi mt mo ome t ng xy ra
trong mt bc duy nht, trong khi ghp ni vi hn hp monome c th xy ra
vic ghp ni tun t hoc ng thi hai monome.
P p p ng trng hp ghp cc monome khc nhau ln cellulose hoc
vt liu lignocellulose c p d x l c nhim mu, kim loi nng.
Bin tnh vt liu lignocellulose t nhin bng phn ng trng hp ghp cc
monome c cha nhm vinyl ci thi c mt s c im ca vt liu th
m v ca vt liu, tnh khng thm c, nh nhit, i, trao
i ion, hn ch s xm nhp ca cc vi sinh vt [29]. Qu trnh ghp cc monome
vinyl ln cellulose hoc vt liu lignocellulose t ng bao gm ba bc, (1) cc v
-
20
tr hot ng trn b mt pol me c si ra, (2) cc mo ome c thm vo phn
ng, (3) mo ome c ghp vo vt liu. Cc v tr hot ng trn mch cellulose
c to ra bi phn k i m o bng ha cht hoc bc x.
Phn ng trng hp ln cellulose ch y c thc hin trong mi
tr c v mi tr k ng nht. Tro c, cc vn v nh hnh
ca cellulose tr l , mch cellulose tr nn d tip cn, cc monome khuch
tn vo cc vng ny v ghp ln mch. Do , t iu qu ghp, vt li c
l m tr trc khi ghp hoc thc hin phn p tro mi trng c kh
l m cellulose tr l . K i tr p p l cellulose trong mi
tr k t, k tip c cc c t do tr cellulose v nhm
vi l l mt t am s q a tr xc i q p. c d, cellulose l mt
pol me t , t i , s i di ca cc v ti t v cc li kt dro
ia cc p t l m im k tip c [28]. Tro c, s tr ia
cc ti t ca cellulose x ra c l v v , v l m t
i q p. P tr p p x ra tt tr v v
ca cellulose do k tip c d d ca v . t i q p c
t t t l cellulose/mo ome, l m tr cellulose trc k i p , oc
ti p p tro mi tr l m tr cellulose. c p
php zn ha, oxi ha, bin tnh vi dung dch kim, c, ami c p d
ci thin kh tip cn ca cellulose. t , k tip c a k
p ca cellulose t k i m l ti t im, m l v
t . Tro q tr x l kim, cellulose c tr v trt t c trc b p
v. trc ti t ca cc c i cellulose so so ba c sp xp li
t cc c i i so so , do t cellulose II [48]. t i, m
l cellulose v t , li i , hemicellulose c c tc ra k i vt
li .
Ty thuc v o cc mo ome c ghp ln vt liu, cc thuc tnh ca sn
phm ghp s khc nhau. Nhn chung, cc nhm chc ph bi c s dng trong
p mo ome c th hin trn hnh 10 [44].
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21
Hnh 10. Cc nhm chc ghp ni vo cellulose to vt liu c nhiu c tnh tt [44]
B cc ng trng hp ghp ni cc monome, cc nhm chc mi c
to ra trn b mt vt liu. Tro , acrylonitrile l m mo ome c s dng
ph bin. Vt liu cellulose c ghp vi acrylonitrile v cc monome khc c
d x l cc ion kim loi nng Cd2+
, Cu2+
, Zn2+
, Cr2+
tro c [44]. Kt qu
cho thy, sn phm ghp nng cao kh li kt vi cc ion kim loi n
cellulose ba u, kh li kt ph thuc vo ion kim loi v c tnh ca vt
liu ghp.
Qu trnh ghp c th c thc hi tro mi tr ng nht hoc
k ng nht. K i ng trng hp ghp din ra tro mi tr k ng
nht, phn c tin hnh bi tc k i m o p hp [44].
-
22
tng hp copolyme ghp ta c th d cc p p p: ng trng hp
gc t do, ng trng hp ion v mt s p p p k c. Cc k thut k i m o
cho qu trnh ghp bao gm ha cht, tia x, quang ha, plasma v ghp enzym.
Tro , k thut k i m o bng ha cht l p p p t c p dng
do chi ph thp v t c hi. Vai tr ca cht k i m o l rt quan trng v n quyt
nh cch thc ghp. Tro trng hp p t eo c c gc t do, cc h khi
mo khc a eri (IV) amo i itrat ( AN), m i pesunphat, tc nhn oxi
ha Fenton (Fe(II)-H2O2), KMnO4-axit oxalic, natri bisunphit/pesunphat l nhng
cht k i m o c s dng v nghin cu. So vi cc q tr k i m o k c,
k i m o t eo c c gc t do c im l c th tin hnh nhit phng v
t c hi.
1.2. c im sinh hc ca cy ay [7, 8]
a c tn khoa hc l Hibiscus cannabinus, thuc chi Hibiscus, h
Malvaceae (h Cm Qu), c khong 40 - 50 loi phn b khp vng nhit i v
cn nhit i. S a l loi si c sn xut v s dng nhiu th hai sau si
cotton. a p t trin tt trn t bi bi, t laterite, t vi vi cp ht t
ct tht n st tht, t kh vi pH t 5,5 - 6,5. a c t pht trin t 1,5 - 4,5
m, t c ng knh khong 1 - 2 cm. l loi cy ngn ngy, cho hoa ti 4
t trc khi ra ht vo cui t i ma. a p t trin kh hu nng v m
t vi khong nhit t 24 n 37C hoc c th cao . l loi cy kh
nhy vi nhit v nh sng nn n cn mt thi im thch hp gieo ht v
thu hoch. iu ki l tng th c th thu hoch sau 100 - 120 ngy k t ngy
gieo ht.
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23
Hnh 11. Cy ay (Hibiscus Cannabinus)
T c a bao m 2 dng si: si o i c gi l lp v libe v chim
khong 40% tr lng cht kh ca thn; si bn trong c mu tr c gi l
si t v c im khong 60% tr lng kh ca thn. Si t a rt chc, t
vi si g loi chc c s d sn xut cc loi giy khc nhau. Phn
th c a c o bt c x si ng , ng knh ln, t l di/r t x
si bt g cng. Thnh phn ha hc chnh ca c a bao m: cellulose (43 -
46%), pentozan (11 - 16%), lignin (21 - 29%) v tro (1,6 - 2,6%).
1.3. Tnh hnh sn xut ay trn ton th gii [7, 8]
i trng ngy cng nhim ch yu do s khai thc qu mc ti nguyn
thin nhin cng s bng n ca th trng sn phm tng hp, nguyn vt liu ti
sinh d c ch nhi cc quc gia pht tri v a p t trin. Si ay
tr nn quan trng bi cc c tnh ha hc vt l c t t i mi trng.
v Bangladesh l cc quc gia c s l a chim n trn 85%
ca ton th gii. Trung Quc, Myanmar v Nepal c trng v sn xut a . c
quc gia sn xut vi din tch nh l Vit Nam, Thi Lan, Indonexia v
Campuchia (Hnh 12).
-
24
Hnh 12. T trng sn xut ay trn th gii
Vit Nam, din tch tr a ln nht l v o m 1987 vi quy m
31.956 ha v s lng 57.576 tn si t. N c , din tch v s l a c
x ng gim trong 3 thp k qua. Hi a , c a c trng ch yu ti Long
An. Di tc , s t v s l a t v a c Lo A c th hin
trong bng 2 v 3.
Bng 2. Din tch, nng sut v sn lng ay t ca tnh Long An
m Din tch
(ha)
ng sut ay t
(tn/ha)
Sn lng ay t
(tn)
2007 8.616 1,70 14,647
2008 1.708 2,01 3,433
2009 1.188 2,16 2,566
2010 2.799,4 1,91 5,347
2011 3.330 1,87 6,227
-
25
Bng 3. Din tch, nng sut v sn lng ay cy ca tnh Long An
m Din tch
(ha)
ng sut ay cy
(tn/ha)
Sn lng ay cy
(tn)
2007 185,0 24,8 4.588
2010 127,5 40,0 5.100
2011 106,4 35,0 3.724
1.4. Cc nh hng mi trng ca cy ay v sn phm t ay [8]
a c k ng ha kh CO2, loi kh nh knh chnh gy nn bi i
kh hu. Ging cc loi c k c, a c s dng CO2 to ng. Trong 120
ngy ca k a a p t trin, mt ha cy tr a c t hp th khong 15 tn
CO2 t kh quyn v gii phng khong 11 tn oxi v cc cht khc. Cc nghin cu
c c o t y rng t l ng ho CO2 a l cao so vi cc loi cy khc
nhiu ln.
c tc mi trng ca sn xut a l t i so vi vic sn xut
si tng hp. N i tr a s dng s lng t cc loi phn bn ha hc v
thuc dit c. N s t a khong 5 - 10 tn cht kh mi m t. Khong 1 tn
cht kh t l c a tr li t v khong 3 tn r v c tro t. Cy a
ip t cng cht h c tro t do l rng tro ma si trng v ci thin
l di d tro t. a t c trng lun canh vi c l t c
k c o v cc loi cc, rau qu, ht c du, tt c s p thuc va
phi hoc nhiu vo cht di d c tro t, t ng khng tr li cho
t, ngoi tr tro trng hp cc cy h , a . P p p l ca
khng ch l m t sn xut nng nghip, m cn duy tr mc ph nhiu ca t
ch yu l thng qua phn hy ca l rng v cht thi h c t a .
a l mt cy tr m t och t nht mi m mt l . a l
mt loi cy l x, pht trin nhanh khi mt kho 4 t tr t . iu
-
26
c a l iu sut sinh hc ca si a l cao iu so vi cc cy ly
g, v do vic s dng si a t a c o d sn xut bt giy s lm
gim chi ph sn xut n mt mc l . N c s lm gim nhu cu cht cy
ph rng.
Trong nng nghip tr a , vic s dng phn bn, thuc tr su v thuc
dit c/thuc dit nm l hn ch. Mc dng phn ha hc cho tr c a l
t 7 - 53 kg cht di dng cho mi ha. S lng phn bn s dng nh ti mc
ng c th c coi l k k. C l r a rng khong 5 - 6
tn l cy trn mt hecta. Mi cy a c k ong 100 - 120 l, do ip im bc
i c t t. R a d i c k m x do ip di c n dinh
dng v lun canh cy tr k ai t c s t cao . L c rng sau khi thu
hoch rt i di dng, l ngun phn bn cho v ma tip theo.
Bng 4. Thnh phn dinh dng c trong cc b phn ca cy ay
B phn it (%) Pht pho (%) Kali (%)
L 2,85 3,60 0,85 1,20 2,50 3,10
Thn 0,17 0,25 0,21 0,28 0,50 0,82
R 0,35 0,46 0,35 0,46 1,50 1,80
Ni chung phn h c l ngun phn bn ch yu trong qu trnh gieo trng
a s lng nh cc loi phn bn ha hc c t c s dng. Tuy
nhin, hu ht cc thuc tr su, n c s d , c loi b trong qu
ngm, sn xut si a . Thuc tr su s dng trong nng nghip a c c tnh
l 0,5 kg/ a, t vi 0,25 kg ca thuc tr su trn tn sn phm.
Q tr m a v cht thi: a c ngm trong c 2 - 3 tun, qu
trnh tn ti vi sinh vt phn h a . Nc thi t qu trnh ny rt giu cht
di dng thc vt c t h c, it, p t pho, kali, st v canxi. Khi lng
ln cht thi t a c th c ti ch tr li lm phn h c.
-
27
T c a l p n cn li sau khi tch si, trong khi si a c i tr
t mi ln th ph t a c coi l mt cht thi nng nghip. T l khi
lng ca g t a so vi si l 2,5:1. G t a c im khong 40% ca tng
khi l c a . c tnh mi m lng cht thi th a ca khong
4 triu tn v Bangladesh l khong 3 triu tn.
T a c a m lng cellulose, hemicellulose v lignin cao l lt l
40, 35 v 23%. V vy, n l mt ngun nguyn liu tim sn xut bt giy.
T a l mt trong nhng nguyn liu lignocellulose thay th cc nguyn liu
truyn thng trong sn xut bt giy Ba lades . c cc i cu tn dng
t a l m t a ci cho nhiu ngnh cng nghip, sn xut cc ha cht v cc
nhin liu lng. Tuy nhin, phn ln th a c s dng lm nhiu liu v lm
hng ro nng thn. Kho 80% t a c s dng lm nhin li
nu ti cc h ia nng thn, ch yu v Bangladesh. Vit Nam,
t a sa k i tc si t ng b thi b, s t c dng lm cht t, hng ro.
1.5. Tim nng s dng ph phm cy ay lm vt liu x l nhim mi
trng
Trong nh m , vic s dng vt liu l cht thi nng nghip
hoc nhng vt thc vt t c gi tr kinh t c c bit quan tm. Nhiu nghin
c c tin hnh nhm bi i cc cht thi nng nghip thnh vt liu x l
mi trng.
Si c a l si cellulose t nhin ph bin trn th gii; c bit, do tnh
cht vt l, ha hc v cu trc tt. c rt nhiu nghin cu bin tnh si c a
thnh vt liu x l c nhim mu, kim loi nng. Tuy nhin, ph ph phm
ca qu trnh tr a v sn xut si a li l mt v mi tr . c tnh,
mi m t tr a to ra 5 - 10 tn tr lng kh bao gm c si v thn cy.
Khong 1 tn cht k c tr li t dng l, khong 3 tn r v c tro t
[46]. Lng cht thi rn t qu trnh sn xut a l k, bao gm cc si a
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28
h , l v t c a . Do , p t trin mt chi lc qun l hiu qu cc cht
thi p t si l iu cn thit.
T c a l mt vt liu lignocellulose, do , c t ti ch thnh vt
liu trong x l c thi, loi b kim loi nng, mu v cc cht h c. Tuy
nhin, nghin cu v s dng cht thi t a mt cht hp ph cn hn ch,
c bit l ng d t a x l kim loi n tro c.
Kh hp ph thuc nhum ca t a c c nghin cu [46].
Than hot t c iu ch t t a c k p ph mu tt. T a
loi b c ti a 81,7% xanh methylen so vi 61% khi s dng than hot tnh
dng bt v 40% khi s dng than hot tnh dng vin. Tuy nhin, hiu qu loi b
BOD (33,3%) v COD (13,8%) l thp so vi x l bng than hot tnh dng
vin.
Bt t a c chng minh l mt vt liu c c kh x l phm
mu c v Rhodamin B tro c [21]. Qu trnh hp ph xy ra khi pH
khong 7 v nhit khng ng nhi n kh p ph. D lng
hp ph ti a ca bt t a i vi c l 35,7 m / v i vi
Rhodamine B l 87,7 mg/g. Hp ph x ra a v t trng thi cn bng ban
u trong vng 60 pht. Bt t a c c nghin c x l phenol trong
c [9]. Vi n p e ol ba u l 40 ppm trong 100 mL, pH dung dch bng
10; 3 a x l c 68% phenol.
nng cao kh p ph, bt t a c nghin cu ch to thnh
than hot tnh [37]. Ch to than hot tnh t t a bng cch s dng hai
p p p vt l v ha hc. T a c hot ha bng ZnCl2 t eo p
php ha hc v i c t eo p p p vt l loi b thuc nhum Brilliant
Gree tro c. Din tch b mt ca than hot t iu ch b p p p
ha hc l 2.304 m2/ v p p p vt l l 730 m
2/ . D lng hp ph cc
i ca than hot t iu ch b p p p a c l 480 m / v p
php vt l l 182 mg/g. Than hot tnh t t a c hot ha bng axit H3PO4
-
29
x l As (III) v As (IV) tro c [26]. Din tch b mt ca than hot tnh l
1.910 m2/ v d lng hp ph cc i l 399 mg/g.
P p p bi t ng trng hp ghp nhm amidoxime c chng
mi l p p p ph hp bin tnh vt li c m lng cellulose ln v
hiu qu x l kim loi n tro c cao. Tuy nhin, hin nay, cc cng trnh
nghin cu bi t t a b p p p ng trng hp p x l kim
loi nng cn rt t.
-
30
Chng 2 - I V PH PHP HI CU
2.1. i tng nghin cu
T c a sa k i tch si c thu thp ti x Nam Thng, huyn Tin
Hi, tnh Thi Bnh. Thn cy a c ra sch vi c ct, sy kh 105C v
nghin thnh dng bt kc t c < 0,5 mm, c bo qun trong hp plastic.
Cc m c nhn to cha c lp cc ion kim loi nng (Zn2+
, Ni2+
, Cu2+
)
cc n k c a c pha long t dung dch gc chun c n 1000
mg/L.
2.2. Phng php nghin cu
2.2.1. Phng php bin tnh vt liu
2.2.1.1. X l b d dc NaOH
T a c ra ba ln vi c ct, s k n khi l k i
sau c nghin thnh dng bt kc t c < 0,5 mm. Sn phm t c
c bo qun trong hp plastic. Bt a c x l bng dung dch NaOH (5-
25%) vi t l bt a /d dch l 1/50 (g/mL), trong 60 pht 25C, lc vi tc
150 vng/pht. Sau khi x l bng dung dch NaOH, m c lc loi b
NaOH d v ra vi c ct n pH trung tnh. Phn cht r t c tip tc
c sy 60C k i l k i. N NaOH x l tt t c
i t q a m l v c s ti t ca cellulose tro bt t a
sa x l.
c i x c tr ca cellulose I l (101), (101-), (002) cc v tr
14,6 , 16,1 v 22,5 (2); xelulozo II l (101), (101-), (002) cc v tr 12 , 20 ,
22 (2) [16] (Hnh 13). V tr cc i x c t dao k i
q a i tr c 2.
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31
Hnh 13. V tr cc nh nhiu x c trng ca cellulose I (a) v cellulose II (b)
trong ph nhiu x tia X
T eo p p p Se al [45], c s ti t ( rI) c t t eo c t c
1 (vi cellulose I) v c t c 2 (khi cellulose I c sa d cellulose II).
CrI = ((I002 Iam)/I002) x 100 (1)
CrI = ((I101- - Iam)/I101-) x 100 (2)
Tro , I002 l c ti a ca ti t i x (002) i vi
cellulose I, I101- l c ti a i x (101
-) i vi cellulose II. Iam l
c t p t m ia 2 i x (002) v (101-) i vi cellulose I;
ia 2 i x (101-) v (101) i vi cellulose II. Iam l c v tr 2
= 18.0 vi cellulose I v 2 = 16.0 i vi cellulose II.
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32
2.2.1.2. tr p ghp acrylonitrile ln bt thn a
Bt t a sa k i bi t b NaOH c tr p p
acrylonitrile (AN) ln cellulose. Ly 1 g bt a x l NaOH vo bnh c
trn lp si i l . Tip t eo, 100 mL c t k i m o NaHSO3/(NH4)2S2O8
c b sung vo bnh, sc kh N2 v k tro 30 p t. P c i
c it 40 - 70C b m k t ia it. Sa t m AN, k
vi tc 300 v/p trong t i ia 120 - 210 pht. P tr p c
kt t c b cc c o k k v o b p v l m l b . Thm vo
bnh 100 mL d dc eta ol loi b AN d, t i kt ta s p m, loi
b cc m i; p c t r c lc q a i lc, sa ra li b etanol v
c ct (3 l ). S p m c s k 60C k i l k i. S
p m bao m polyme ca AN (polyacrylonitrile) v bt t a p AN.
S p m p c ra v i l vi N,N-dimetylfocmamit loi b
polyacrylonitrile. t r t c sa k i lc c l m k k i l k
i v i li k i l s p m.
Cc yu t n phn ng trng hp ghp AN ln bt a
c kho st bao gm: n cht k i m o, t l khi l AN/t a , it
v thi gian phn ng. ng ca cc iu ki c i t q a t
l ghp v hiu sut ghp, t tm ra iu kin ti c o mi yu t.
T l ghp (%G), hiu sut p (%E) c tnh theo cc cng thc 3 v 4
[15].
T l ghp (%G) = [(W1 W0)/W0] x 100% (3)
Hiu sut ghp (%E) = [(W1 W0)/W2] x 100% (4)
Tro , W0, W1 l lt l khi lng ca bt a c a p v sa k i
ghp AN. W2 l khi l AN ba u.
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33
Cc th nghim kho st cc yu t n kh p
acrylonitrile ln bt t a c ti c lp, c tnh k tha (kt qu ca
th nghim trc l iu ki thc hin th nghim sau) v th hin trong bng 5.
Bng 5. nh hng ca cc iu kin phn ng n kh nng ghp AN ln bt thn ay
TT Th nghim B tr th nghim
1
ng t l
[SB/APS]
(CM/CM)
mbt t a = 1 g, Vt = 100 mL, [APS] = 0,2 mol/L,
2h, 60C, VAN = 5 mL (99,9%),
[SB] = 0; 0,05; 0,1; 0,15 hoc 0,2 mol/L
2
ng ca nng
h k i m o [I],
[I] = [SB] + [APS]
mbt t a = 1 g, Vt = 100 mL, 2h, 60C, VAN = 5 mL
[I] = 0,035; 0,0875; 0,175; 0,35; 0,525 hoc 0,7
mol/L
3 ng ca t l
AN/a
mbt t a = 1 g, Vt = 100 mL, [APS] = 0,2 mol/L,
[SB] = 0,15 mol/L, 2h, 60C,
A /ay (g/g) = 1,62; 3,24; 4,05; 4,86; 6,48 hoc 8,1
4 ng ca thi
gian phn ng
mbt t a = 1 g, Vt = 100 mL, [APS] = 0,2 mol/L,
[SB] = 0,15 mol/L, 60 , AN/a = 4,86 (t
vi 6 ml AN);
hi gian = 2; 2,5; 3 hoc 3,5 gi
5 ng ca nhit
phn ng
mbt t a = 1 g, Vt = 100 mL, [APS] = 0,2 mol/L,
[SB] = 0,15 mol/L, 2,5 i; VAN = 6 mL;
AN/a = 4,86;
T = 40, 50, 60 hoc 70C
Ch thch: SB l natri bisunphit, APS l amoni pesunphat, Vt l tng th tch
(mL), AN l acrylonitrile, VAN l th tch acrylonitrile (mL), I l h k i m o
SB/APS.
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34
2.2.1.3. Amidoxime a s p m p acr lonitrile
1 g c t r t c sau khi ghp acrylonitrile c amidoxime a b
NH2OH.HCl (2,5 - 15%) trong p dung dc met a ol : c (v : v = 1 : 1)
sao c o t t tc d dc b 50 ml. pH ca d dc c i c
k o t 9 10 b m i Na2CO3. P it 25 - 80C trong t i
gian 30 - 360 pht, k vi tc 300 v/p. Sa p , lc q a i lc loi
b p d dc v ra s p m t c 3 l vi c ct pH tr t ,
s k k i l k i.
Cc yu t n phn ng amidoxime ha sn phm ghp PAN
bao gm: n NH2OH.HCl, nhit phn ng, thi gian phn ng. Da vo
m lng t it i iu qu ca qu trnh amidoxime [11]. S bin
thin ca m lng t it biu th cho s t a i ca nhm amidoxime trong
vt liu.
nh hng ca nng NH2OH.HCl: 1 g sn phm p c phn ng
vi dung dch NH2OH.HCl cc n khc nhau (2,5; 5; 7,5; 10; 12,5 hoc 15
%) 25C trong 120 pht. Sa p , li tm tc p c t r , ra li b
c ct pH tr t , s k k i l k i v xc m
l ito.
nh hng ca nhit phn ng: 1 s p m p c p vi
d dc NH2OH.HCl n ti xc nh th nghim trc, trong khong
thi gian 120 pht. Nhit phn t a i 25, 30, 40, 50, 60, 70 hoc 80C.
nh hng ca thi gian phn ng: 1 s p m p c tip xc vi
d dc NH2OH.HCl n ti v nhit ti hai th nghim trc.
Thi gian phn t a i t 30, 60, 120, 180, 240, 300 hoc 360 pht.
2.2.2. Xc nh c tnh c bn ca vt liu
Vt liu hp ph c xc c im vt l v ha hc c bn, chi tit
cc p p p c trnh by trong bng 6.
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35
Bng 6. Phng php xc nh mt s tnh cht vt l, ha hc ca vt liu
Tnh cht Phng php phn tch Thit b phn tch
c im hnh thi Knh hi vi in t qut JSM 5410LV, hng Joel
c im cu trc Nhiu x tia X Bruker-AXS D5005,
Sieme s, c
in tch b mt P tc in di Mtek PCD 05, hng
BTG, c
c im lin kt,
nhm chc
Quang ph hp th hng
ngoi (FTIR)
Nicolet iS5 FTIR
Spectrometer, hng
Thermo Scientific, M
- Phng php nh lng cellulose [1]
P p p lng cellulose da trn tnh cht bn ca cellulose i
vi tc dng ca axit mnh v kim mnh, khng b phn h di tc dng ca
axit yu. Cc cht khc c trong vt liu ligniocellulose hemicellulose, lignin,
tinh bt, amin, cc axit bo,... t bn trong dung dch axit v kim nn b oxi ha v
phn gii, sa ta v o d dch sau khi x l nguyn liu.
P p p lng cellulose c ti sa : c xc 1-
2 am t a k c o v o b tam ic 500 mL, b sung vo bnh 200 mL dung
dch NaOH 0,5%. Lp si o l tro 30 p t k t lc si. Lc
cht rn qua giy lc hoc ly tm. Ra cht r t c vi dung dch NaOH 0,5%
nng. Tip tc cho cn tc dng vi 10 mL H l 10%. T m v o 10 mL d
dch natri hypoclorit tng git mt, va cho va khu . yn trong 5 pht ri
lc qua giy lc thu cht rn. Cho cht rn tip tc tc dng vi NaOH 0,5%
nhit 40o . yn vi pht v lc cht rn. Lm lp li 2 ln na t c
cellulose trng. Sau cng, ra sch cellulose t c b c si. Sy kh v
cn tr lng cellulose.
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36
H m lng cellulose trong t a c tnh theo cng thc:
X (%) = (a.100)/m (5)
Tro : a l tr lng cellulose (g)
m l tr lng m t a ( )
2.2.3. Kho st kh nng hp ph ion kim loi nng ca vt liu bin tnh
- nh hng ca pH: xc thng qua bi i m i b mt ca vt
li sa k i bi t ti cc i tr pH k c a . Gi tr pH t c p p i t p
i tr pH kt ta cc cc io kim loi v t im axit t si tro
c sa k i x l.
- Xc nh cc h s hp ph ca vt liu bin tnh vi cc ion KLN
Ti t im p p cc io kim loi Cu2+
, Zn2+
hoc Ni2+
b 100 m vt li bi t trong 100 mL dun dc c a cc io kim loi vi
ba l 0, 20, 40, 60, 80 oc 100 m /L. T im c ti
25C, pH d dc b 6 (pH k o st c tro t im trc), lc vi tc
100 v /p t tro v 1 i v m 24 i. c lc xc
io kim loi c li tro d dc sa c b p p b m q ang
p p t t AAS (S imadz , N t B ).
- Xc nh thi gian lu ti u cho qu trnh x l ion KLN (Zn2+, Ni2+,
Cu2+
) vi vt liu bin tnh
Cn 250 mg vt liu vo 250 mL dung dch cha Zn2+
, Ni2+
hoc Cu2+
c
n (Qimax x 250mg) / 250mL = Q
imax (mg/L) vi Q
imax (m / ) l d lng
hp ph cc i ca vt liu vi Zn2+
, Ni2+
hoc Cu2+
. M c lc tc 100
v/p theo thi gian. Sau mi khong thi gian cch nhau 1 gi, dung dch cha vt
li c lc u v ly ra 25 mL sao cho mt vt liu tromg dung dch cn li
v ly ra l bng nhau. Dung dch l ra c lc v phn tch KLN bng my
quang ph hp th nguyn t AAS (S imadz , N t B ).
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37
Chng 3 - K QU HI CU V HO LU
3.1. c tnh c bn ca bt thn ay
Bt t a l vt liu lignocellulose, cha mt m lng cellulose
k. Cellulose trong bt t a l c i polyme chnh, nhm (-OH) trn phn t
cellulose vai tr q a trng trong lin kt vi nhm nitrile ca monome
acrylonitrile ln bt t a . Do , cc c t c bn ca t a bao m c
im hnh thi b mt, cu trc cellulose, cc nhm chc b mt trn bt t a
c c kho st trc khi tin hnh bin tnh ha hc.
3.1.1. c im hnh thi b mt ca bt thn ay
Bt t a c d v kc t c k ng nht. Kt qu phn tch
trn knh hi vi in t qut (SEM) cho thy dy cc mnh bt t a khong
5 m. B mt ca bt t a ba u c cc mng bm nh dng vy (Hnh 14).
i t t khi quan st thy trong bt g ca cc sinh khi khc [32].
(a) nh chp p i 1000 ln (b) nh chp p i 2500 ln
Hnh 14. nh SEM b mt bt thn ay
-
38
3.1.2. c im cu trc ca bt thn ay
Thnh phn ca bt t a bao m c vng v nh hnh v vng tinh
th. Tro lignin, hemicellulose, pectin l nhng hp cht v nh hnh ch yu;
tro k i cellulose ng thi tn ti c hai d v nh hnh v tinh th. Dng
v nh hnh trong cellulose khi dng sinh khi ba u l dng tinh th cellulose
I [48, 50]. Kt qu nhiu x tia X (Hnh 15) cho thy kt qu t ng vi cc
nghin cu v cc sinh khi thc vt khc. c nh nhiu x c tr ca dng
cellulose I xut hin v tr c 2 l 22,52o
(002); 16,01 (101-) v 15,11 (101). Ch
s tinh th ca cellulose trong bt t a c i tr l 55,76 %. N v , mt
na lng cellulose tro t a tn ti dng tinh th. Tro k i , p
php bin tnh ha hc c hiu qu i vi v v nh hnh v d tip c
so vi vng tinh th. Do , bt t a cn phi x l ph v cu trc tinh th,
t t l v v nh hnh.
Hnh 15. Ph nhiu x tia X ca bt thn ay
-
39
3.1.3. c im lin kt, nhm chc
Kt qu phn tch ph hp th hng ngoi i vi bt t a cho thy, b
mt ca bt t a cho thy bao gm cc nhm v lin kt ch yu l (OH),
C=O, C=C, CC, CH. Cc nh hp th s sng 3.350 cm-1
biu th dao ng
ca nhm (OH). Nhm ny c th tn ti trong lin kt (OH) lin phn t, ni
phn t ca cellulose, hemicellulose, lignin; lin kt hydro trong nhm cacboxyl.
Tro k i , nh hp th s sng 1.739 cm-1
th hin s tn ti ca lin kt C=O
trong nhm cacboxyl. Lin kt CO ti v tr v t m ca lignin xut hin s
sng 1.250 cm-1
. Vch ph s sng xut hin s sng 1.598 cm-1
th hin dao
ng dn ca lin kt C=C trong cc axit bo.
Hnh 16. Ph hp th hng ngoi ca bt thn ay
Nhn chung, qua ph hp th hng ngoi c th thy, b mt ca bt t a
cha cc nhm chc in hnh l nhm hydroxyl, nhm cacboxyl. Cc nhm chc
ny c vai tr quan tr tro p p p bi t ng trng hp ghp, trong
c bit quan trng l nhm hydroxyl trong polyme cellulose.
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40
3.2. Quy trnh bin tnh to vt liu amidoxime ha t bt thn ay
3.2.1. X l bng dung dch NaOH
3.2.1.1. Lm giu cellulose trong bt t a
X l bt t ay bng dung dch NaOH nhm loi b cc cht h c d b
thy phn, c th to thnh cc cht h c tro c l lignin, hemicellulose,
amin, axit h c. Bt t a sa x l c m lng cellulose-polyme mch
chnh t , ip c o phn ng trng hp ghp vi AN c thun li.
ng ca n dung dch NaOH x l n khi lng bt t a
a c li v s bi i m lng cellulose trong bt t a c th hin trn
hnh 17.
Hnh 17. nh hng ca nng NaOH n khi lng cn li v hm lng
cellulose trong bt thn ay
K i t NaOH, qu trnh thy phn cc cht lignin, hemicellulose,
axit bo,... din ra cng mnh nn khi l a c li gim. iu ny d n
m lng cellulose trong bt t a c t k i t NaOH. Khi
lng bt t a c li gim nhanh khi n NaOH t n 5 v 10% so vi
bt t a ba u do qu trnh ha tan ph v nh hnh din ra mnh. Tuy
-
41
nhin, khi tip tc t NaOH th khi lng bt t a im khng
nhiu v g do m lng ph v nh hnh trong bt t a l
gii hn.
Qu trnh x l bng NaOH thc cht l qu trnh lm giu cellulose lm
nguyn liu cho cc bc nghin cu bin tnh tip theo. khong n NaOH
t 10% tr ln, m lng cellulose t mc cao v g nh.
3.2.1.2. Xc nh ch s tinh th ca cellulose trong bt t a bng ph nhiu x
tia X
Qu trnh x l b NaOH ng thi l m t a i cu trc ca cellulose
trong bt th a . P nhiu x tia X ca bt t a t v bt t a x l
bng dung dch NaOH cc n k c a c th hin trn hnh 18.
Hnh 18. Ph nhiu x tia X ca bt thn ay ban u v x l cc nng dung
dch NaOH khc nhau
C th thy rng, bt t a ba u C0 v bt t a c x l vi
dung dch NaOH cc n 5% v 10% l C5 v C10 dng cellulose I vi cc
nh nhiu x v tr c 2 l kho 22,5 n 22,7 v cc nh nhiu x v tr
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42
14 n 16. Khi n NaOH t n 15%, xut hi ai nh nh nhiu x
v tr c 2 l 20,1 v 12,2. l cc nh nh nhiu x c tr ca cellulose
II. iu ny chng t rng qu trnh x l bng dung dch NaOH lm chuyn dang
cu trc ca cellulose I sang cellulose II. Cc nh nhiu x c tr ca cellulose
II c x t hin cc m a x l vi dung dch NaOH 20 v 25% (C20 v
C25).
Ch s tinh th c tnh ton theo cng thc v 1 v 2 (mc 2.2.1.1), s ph
thuc ca ch s tinh th vo n NaOH c th hin trn hnh 19.
Hnh 19. S bin i ch s tinh th ca cellulose trong bt thn ay khi x l vi
dung dch NaOH cc nng khc nhau
Ch s tinh th ca bt t a t l 16,72% so vi th a ba u sau
khi x l vi NaOH 5%. Tuy nhin, khi n NaOH t l t c s tinh th
li gim d v t gi tr ti thiu 45,45% ti n NaOH l 15%. Sa , c
s tinh th t khi n NaOH t l 20% v t gi tr nh. iu
ny c th gii thch do ba qu trnh xy ra khi x l bng kim: bt t a tr
n, ph v vng tinh th v hnh thnh mng tinh th mi. n NaOH thp,
lng NaOH v mt NaOH nh, k ph v mng tinh th cellulose vi
cu trc c bao bc bi hemicellulose v lignin. Ch c v v nh hnh v
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43
vng tinh th b mt trong cu trc cellulose c th phn ng vi kim. N vy,
vng khng gian gia cc mch polyme cellulose khng ln nn cc si c kh
sp xp li cu trc [48]. Do , c s tinh th ca t a t k i
NaOH nh. K i t NaOH ln 15%, cu trc cellulose t trng thi
tr nhiu nht, iu ny lm cho NaOH d dng tip xc vi cc vng tinh
th ca cellulose v ph v cu trc tinh th d n CrI gim k. Tuy nhin,
kh tip xc vi cellulose ca NaOH gim do t nht ca dung dch
NaOH n cao [48], do , c s tinh th vn ln.
T cc kt qu thc nghim nu trn, c th thy rng n NaOH 15% l
n thch hp nht lm gim cc vng kt tinh trn cellulose c l m
t m lng cellulose trong bt t a .
3.2.1.3. c im lin kt v nhm chc b mt
Ph hp th hng ngoi ca bt t a t v sa k i x l bng NaOH
cc n khc a c th hin trn hnh 20.
Hnh 20. Ph hp th hng ngoi ca bt thn ay ban u v x l cc nng
NaOH khc nhau
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44
Kt qu cho thy, lin kt hydro trong nhm hydroxyl (OH) dao ng xut
hin di ph t 3.000 - 3.600 cm-1. nh hp th ca nhm (OH) gim dn khi
n NaOH t l do m OH p n ng vi Na+. S suy gim nhm (OH)
c th do qu trnh thy phn cc cht km b axit bo, emicell lose, li i
trn b mt bt t a . c li kt hydro ni phn t O2-H---O6, O3-H---O5 v
lin kt hydro lin phn t O6-H---O3 tro cell lose I t ng xut hin di ph
t ng l 3.455 - 3.410, 3.375 - 3.340 v 3.310 - 3.230 cm-1
. Ph hp th hng
ngoi ca bt t a ba u v x l cc n dung dch NaOH thp (5, 10
%), nhm (OH) xut hin s sng 3.350 cm-1
; tuy nhin, khi x l cc n
NaOH cao (15, 20, 25%), nhm OH xut hin s sng 3.447 cm-1 c tr c o
lin kt O2-H---O6 tro cell lose II. iu ny chng t rng, cu trc tinh th ca
cell lose I c n sang dng cellulose II sau khi x l bng NaOH.
nh hp th s sng 1.739 cm-1
quan st thy trong bt t a ba u
v mt i sa k i x l bng kim tt c cc n NaOH trong nghin cu.
iu ny l do nhm cacboxyl b thy phn sau khi x l bng kim, qu trnh ny
c gi l este ha [32]. S suy gim c ca nhm C=O s sng 1.655
cm-1
khi x l bng kim ch ra rng hemicellulose b loi b sau khi x l kim.
nh hp th v tr s sng 1.250 cm-1
hin th cho lin kt C-O ti v tr
v t m ca lignin trong bt t a c im i k sau khi x l bng
kim. nh hp th v tr 897 cm-1
chuyn sang v tr 894 cm-1
. S sng 897 cm-1
trong lin kt -glucozit trong cu trc cellulose I v s sng 894 cm-1
trong cu
trc cellulose II [50]. S t a i ny l do glucose quay quanh lin kt glucosidic
lm cho cu trc cellulose I chuyn sang dng II.
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45
3.2.2. ng trng hp ghp acrylonitrile ln bt thn ay bng h khi mo natri
bisunphit/amoni pesunphat (SB/APS)
3.2.2.1. c ca p tr p p acr lonitrile b k i m o
natri bisunphit/amoni pesunphat
Phn ng trng hp ghp AN bng h k i m o oxi a k SB/APS
da tr c c gc t do. Gc t do c to thnh t phn ng ca h k i m o,
sa cc gc ny tip tc phn ng vi nhm OH trn mch cellulose hnh
thnh cc gc cao phn t. Cc gc cao phn t ny tip tc khi xng phn ng
ng trng hp ghp AN ln mch cellulose. Phn ng trng hp polyacrylonitrile
(PAN) c di ra ng thi vi phn ng trng hp ghp.
Gc t do SO4-*
c to ra t phn ng gia natri bisunphat v amoni
pesunphat t eo p tr 7 [43].
H2O + HSO3- + 2S2O8
2- 3HSO4
- + 2SO4
-* (7)
SO4-*
+ H2O HSO4- + HO
* (8)
Gc SO4-*
s tip tc phn ng vi cc nhm hydroxyl trn mch cellulose
[40] hnh thnh cc gc cao phn t trn cellulose (Cell OH) (p tr 9)
v gc t do M* (p tr 10).
SO4-*
+ Cell OH HSO4- + Cell O
* (9)
M + SO4-*
M* + SO4
2- (10)
Cc gc cao phn t ny tip tc khi xng phn ng ng trng hp ghp
monome ln mch cellulose v phn t PAN t eo c c sau:
Cell O* + M Cell OM
* (11)
Cell OM* + M Cell OMM
* (12)
Cell OM*n-1 + M Cell OMn
* (13)
Cell OM*n + Cell OM
*n sn phm ghp (14)
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46
Phn ng trng hp PAN din ra song song vi phn ng trng hp
p, c c phn ng trng hp AN sa :
M* + M MM
* (15)
Mn-1* + M Mn
* (16)
Mn* + Cell-OH Cell-O
* + MnH (17)
Mn* + Mm
* Mn+m (18)
P p p ng trng hp ghp c k i m o bng h oxi ha kh, cc
gc t do phn c to ra t phn ng ha hc. Do , cc u t n
cht k i m o, monome, thi gian, nhit l nhng yu t ng
trc tip n hiu sut qu trnh ghp.
3.2.2.2. ng ca t l cc cht k i m o
Hnh 21 th hin ng ca t l cc cht k i m o SB/APS (CM/CM)
n t l ghp v hiu sut ghp. N SB t a i t 0 n 0,2 mol/L, n
APS c nh n 0,2 mol/L. Kt qu cho thy, t l ghp (G%) t cao nht l
13,13% v hiu sut p t 3,24% khi t l SB/APS l 0,75.
Hnh 21. nh hng ca t l SB/APS n kh nng ghp AN ln bt thn ay
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47
t l thp , SB k phn ng vi APS to thnh gc
t do d n t l ghp v hiu sut ghp thp. T l ghp t l k iu
k i t SB. T l ghp t 2,51% khi h k i m o ch c APS v t l
t 2,55% khi t l SB/APS l 0,25. iu ny chng t rng; khi n SB thp,
phn k i m o c y do APS vai tr c . K i c cung cp nhit
, ion pesunphat trong APS c th to thnh gc t do t eo p tr sa :
S2O82-
2SO4-*
(19)
SO4-*
+ H2O HSO4- + HO
* (20)
Khi t l SB/APS t l 0,5 p n k i m o to thnh nhiu gc t do
d n t l ghp t l 3,83% v t gi tr cao nht l 13,13% khi t l ny
l 0,75. T eo p tr 7, t l cn bng ha hc ca phn ng to gc t do
gia SB v APS l 0,5.
T l SB/APS tip tc t l 1 t G (%) v E (%) im do cc gc t do
to thnh t phn ng k i m o to ra ln d n phn ng trng hp PAN cnh
tranh vi phn ng trng hp ghp, cc gc t do M* ca AN phn ng vi
nhau lm gim hiu qu phn ng ghp. Trong phn ng ghp nhm vinyl ln
g/cellulose, HO* c kh p n i SO4
-*. Tuy nhin, khi t l SB/APS
cao, gc t do b trit ti t eo cc p tr (21) (23) [43].
SO4-*
+ H2O HSO4- + HO
* (21)
2SO4-*
+ HSO3- 2HSO4
- + SO4
2- + H
+ (22)
2HO* + HSO3
- SO4
2- + H2O + H
+ (23)
3.2.2.3. ca k i m o SB/APS
T l SB/APS = 0,75 c la ch nghin cu ng ca tng nng
h k i m o n kh p. Tng n h k i m o [I] = [SB] + [APS].
Hnh 22 th hin s ph thuc ca t l ghp v hiu sut ghp vo n h k i
mo I. iu ny ph hp vi l thuyt Smith-Ewart d o rng tc ca phn
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48
ng trng hp ph thuc vo hai bin, n k i m o v cht c hot
b mt.
Hnh 22. nh hng ca tng nng h khi mo n kh nng ghp ca AN ln
bt thn ay
Ba , k i t h k i m o, t l ghp v hiu sut p t ,
sa im dn. Kh p tt nht t c khi tng n k i m o l
0,35 mol/L vi t l ghp l 13,13% v hiu sut ghp l 3,24%. S ia t ca t
l ghp v hiu sut ghp l cc gc t do c to t t k i h k i
m o t v cc c ny c s phn ng vi mch cellulose. Khi n h
k i m o t 0,35 mol/L, cc gc t do pesunphat t l ; do ,
khi xng phn ng trng hp AN, phn ng ny cnh tranh vi phn ng
trng hp ghp do cng tiu th AN v gc pesunphat.
3.2.2.4. ca t l acrylonitrile/a
T l khi l AN/a l yu t quan trng quyt nh hiu qu qu trnh
ghp. ng ca t l AN/a c th hin trn hnh 23.
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49
Hnh 23. nh hng ca t l khi lng AN/ay n kh nng ghp AN ln bt
thn ay
K i t t l khi lng AN/a t 1,62 (t ng vi 2 mL c) ln 4,05
(t ng vi 5 mL AN c) th t l ghp t t 3,59 n 13,13%. Hiu sut
ghp c s t a i k k. Khi t l AN/a t l n 4,86 (t ng
vi 6 mL AN c) th kh p t l rt nhanh, t l ghp t cao nht l
88,63% v hiu sut ghp l 18,24%. iu ny l do lng AN t l m t kh
tip xc ca AN vo mch cellulose tr t a , d t k p
AN vo cc gc t do trn mch cellulose. H a, n AN cao cn lm cho
bt t a tr , to iu kin cho s khuc t cc mo ome AN do l m
t iu qu ghp [17]. Tuy nhin, t l ghp v hiu sut ghp li c x ng
gim nhanh khi tip tc t t l AN/a q 4,86. i c gii thch l do
s cnh tranh gia phn ng trng hp AN v phn ng trng hp ghp. Khi
n AN trong dung dch phn ng cao th phn ng trng hp AN chim t
[30].
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50
3.2.2.5. ca t i ia p
Kt qu ng ca thi ia n kh p c th hin trn hnh
24. C th thy, kh p t a k i t i gian phn t t 2 n
2,5h; t gi tr t l ghp v hiu sut ghp ti a l lt l 131,36% v 27,03%
2,5h. Tuy nhin, sau 2,5h th kh p c x im c th l do s ha
tan mt phn sn phm ghp khi tip xc trong thi gian di nhit cao 60C [17].
Do , t i gian phn hiu qu ghp ti l 2,5 .
Hnh 24. nh hng ca thi gian phn ng n kh nng ghp AN ln bt thn ay
3.2.2.6. ca it p
Nhit l mt trong nhng thng s quan trng quyt ng hc ca
qu trnh ghp. Kt qu cho thy, t l ghp v hiu sut p t k i t it
t 40 60 , sa im dn khi nhit t l n 70C. T l ghp v hiu
sut ghp cao nht t c khi nhit phn ng 60C l lt bng 131,36% v
27,03%. N vy, nhit ti c o p n p AN l t a l 60 .
Nhit cao l m t k va c m ca cc phn t v cellulose d n s
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51
gia t cc c t do tr cell lose v do t cng kh p AN l
cellulose. Mt khc, hiu sut ca phn k i m o t l k i t it .
Hnh 25. nh hng ca nhit n kh nng ghp AN ln bt thn ay
Tuy nhin, t l ghp v hiu sut ghp li gim nu tip tc t it
ln 70C c th do phn k i m o si ra mt lng ln cc gc t do trong
mt v thi gian. Kt qu l, cc gc t do trn b mt cellulose d tip xc vi
nhau lm mt cc gc t do theo cc phn ng ngt mch. Mt khc, khi nhit
t , li ng ca cc gc t do s t v d dng tip xc vi nhau [40]. Xu
c c quan st thy trong cc nghin c t t [17,29]. Mt
nghin cu c cng b [43] tin hnh kho st ng thi t l ghp v hiu
sut hnh thnh PAN, kt qu ch ra rng, nhit 40-60C, phn ng trng
hp ghp chim t . Tuy nhin, nhit cao (70 ) t p n ng trng
hp AN li chim t . Do , it ti ca phn ng trng hp ghp
AN ln bt t a l 60 .
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52
N vy, hiu qu ca phn ng trng hp p AN l t a cao
nht khi: n natri bisunphit, 0,15 mol/L; n amoni pesunphat, 0,2 mol/L;
t l khi lng AN/bt t a , 4,86:1 g/g; thi gian, 2,5h; nhit , 60C.
3.2.3. Phn ng amidoxime ho
3.2.3.1. ca NH2OH.HCl
Sau phn ng trng hp ghp AN ln bt t a , m l it (%)
t t 0,18% trong bt t a c a bi t l n 3,18%. Sn phm ng
trng hp p c tip tc phn ng amidoxime vi hydroxylamin
hydroclorid cc n khc nhau. Khi n NH2OH.H l t trong khong
t 2,5 n 10%, m l it tro vt li t l k chng t m lng
nhm amidoxime trong vt li t l . iu ny l do cc nhm nitrile (CN)
trn b mt vt liu c s phn ng vi NH2OH tro mi trng kim to
thnh nhm amidoxime (C(NH2)=NOH).
Hnh 26. nh hng ca nng NH2OH.HCl
K i t n NH2OH.H l t l t 10 15% t m l it
t k k; t 8,35% 10%, 8,43% 12,5% v 8,54% 15%. N vy,
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53
n NH2OH.HCl 10% l n m phn ng to thnh nhm amidoxime t
trng thi . Do , c chn thc hin cc th nghim tip
theo.
3.2.3.2. ca it p
Hnh 27. nh hng ca nhit phn ng
ng ca nhit n kh amidoxime a c th hin trn
hnh 27. Kt qu cho th , m lng nit t a k i it phn t
trong khong t 25 l 60 v t ti a l 10,47% 60C, chng t m lng
nhm amidoxime trong vt li t a k i it t . T i , k i
nhit l cao l 60 t m l it li gim. iu ny c th do nhit
cao lm phn ly cc nhm nitrile trn b mt bt t a , d n lm gim v
tr hot ng ca phn ng chuy i. X t t c c quan st thy
trong nghin cu ca c cng b [20].
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54
3.2.3.3. ca t i ia p
Thi gian phn ng amidoxime c t a i t 30 n 360 pht v gi cc
thng s nhit c nh 60C v n NH2OH.HCl l 10% i nh
ng ca thi ia n phn ng chuyn ha nhm nitrile thnh nhm amidoxime.
Hnh 28. nh hng ca thi gian phn ng
Kt qu nghin cu cho th , m l it c m lng nhm
amidoxime trong vt li t a k i t i gian phn t n 120 pht. Khi
tip tc t t i gian ln 180 v 240 pht t m l it t c m v t n
nh khi thi gian phn l 240 p t. Lng amidoxime c to thnh ln
tro iai o u ca phn ng l do s lng nhm nitrile c sn trn b mt
t a c o c chuyn ha thnh amidoxime. N k i t g thi gian phn
ng, s lng cc nhm nitrile im rt nhiu d n hiu sut phn ng thay
i khng nhi . N vy, thi gian bo ha ca phn ng amidoxime l 240 pht.
T cc kt qu ti a cc bc tro p p p bin tnh to vt liu
amidoxime ha t bt t a , s quy trnh bin tnh vt li c th hin trn
hnh 29.
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55
R/L = 1: 50 (g/mL)
- R/L = 1:50 (g/mL)
- pH = 9 10
T l AN/a = 4,86
(g/g)
R/L = 1: 100
(g/mL)
Bt t a
NaOH 15% - Thi gian: 1 gi
- Tc lc: 150 v/p
- Lc, ra sc n pH = 7
Bt t a x l NaOH Hn hp
NaHSO3/(NH4)2S2O8
[NaHSO3] = 0,15 mol/L
[(NH4)2S2O8] = 0,2 mol/L
- Sc kh N2
- Nhit 60C
- Thi gian: 30 pht
- Gdyhuieg dsuds
ncmcssd
-
Hn hp 1
- Sc kh N2
- Nhit : 60C
- Thi gian: 2,5 gi
- Vn tc khuy: 300 v/p
Hn hp 2
Etanol,
N,N -dimethylfocmamit - Ra, lc
- Sy kh 60C
Sn phm ghp
Vt li bin tnh
NH2OH.HCl 10% - Nhit : 60C
- Thi gian: 240 pht
- Vn tc khuy: 300 v/p
- Lc v sy kh 60C
Acrylonitrile 99,9%
Hnh 29. Quy trnh bin tnh to vt liu amidoxime ha t bt thn ay
-
56
3.3. c tnh ca vt liu bin tnh
a. b.
c. d.
Hnh 30. c im hnh thi b mt ca bt thn ay ban u (a), ay x l bng
NaOH 15% (b), ay ghp AN (c) v vt liu bin tnh (d)
c im hnh thi b mt ca bt t a ba u, sau khi x l vi NaOH
15%, ghp AN v vt li bin tnh c th hin trn hnh 30.
M a sa x l b NaOH c c loi b cc cht h c l m c o
b mt tr nn nh v c cc r . Sa k i amoxime ha, b mt bt t a tr
nn dy v xp so vi bt thn a ba u v x l bng dung dch NaOH.
-
57
Ph FTIR ca t a ba u, sau khi x l bng dung dch NaOH 15%,
ghp AN v vt liu bin tnh c th hin trn hnh 31, 32.
Hnh 31. Ph hp th hng ngoi ca bt thn ay ban u (a), sau x l NaOH
15% (b) v ghp AN (c)
Cc lin kt v nhm chc trong bt t a ba u, x l bng dung dch
NaOH, ng trng hp ghp AN v vt li bin tnh c xc nh bng ph
hp th hng ngoi. So snh ph bt t a sa k i x l NaOH (Hnh 31b), ph
bt t a sa k i p AN x t hi nh hp th v tr 2.260 cm-1
, biu th
cho s ko c ca lin kt N. Sa k i amidoxime a, ba nh hp th xut
hin v tr 2.260, 1.660 v 910 cm-1
t ng vi cc lin kt N, =N v N
OH do phn ng ca hydroxylamin vi nhm nitrile c th hi di p
trnh sau [38]:
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58
(24)
ng thi, s suy gim c hp th ti v tr s sng 2.260 cm-1
trong
ph ca vt liu (Hnh 32) so vi ph bt t a sa k i p AN (H 31c)
chng t mt phn nhm nitrile t am ia v o p n ng amidoxime ha. Ph
hng ngoi ca vt liu xut hi nh hp th khong s sng 3.423 cm-1
v c
c ln th hin lin kt hydro trong nhm hydroxyl (OH) hoc lin kt NH
trong nhm (NH2).
Hnh 32. Ph hp th hng ngoi ca vt liu
-
59
c im in tch b mt ca bt t a ba u, sau khi x l bng
dung dch NaOH 15% v vt li c th hin trn hnh 33 v hnh 34. Kt qu
cho thy, qu trnh x l bng kim lm cho b mt t a m i so vi
t a ba . iu ny l cn thit nng cao hiu qu phn ng trng
hp ghp AN [44]. S lng nhm (OH) c kh tip c t l sa p n
ng v lm cho b mt m i . K i pH c t t m (OH) trn b mt
vt liu gii phng ra ion H+ trung ha kim, d n b mt vt li m in
k i pH t l [41].
Hnh 33. Th zeta ca bt thn ay ban u, sau x l NaOH 15% v vt liu
Vt li bin tnh c b mt m i so vi bt thn a x l NaOH
v bt thn a ba u. Chng t rng, vt li bin tnh c ghp vo cc
nhm (OH) l m t m in. Th zeta ca vt liu gim a k i pH t a i
t 2 n 6; khi pH > 6, th zeta gim chm v g k im k i t pH t
10 11. T t t zeta, s l in tch m b mt (cmole(-)
/kg) cng
ln khi gi tr pH cng cao (Hnh 34).
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60
Hnh 34. in tch m b mt ca vt liu bin tnh cc pH khc nhau
3.4. Kh nng x l kim loi nng (Cu2+
, Zn2+
, Ni2+) ca vt liu bin tnh
3.4.1. Xc nh gi tr pH x l
N trnh by ph c tnh ca vt li bin tnh, vt liu c b mt
m in, gi tr pH c cao t pH c m in. Ti pH 6, m in ca b
mt kh l v k i t pH t m in b mt gim khng nhi . T i ,
loi b ng ca qu trnh kt ta cc ion kim loi, pH 6 l gi tr pH ph hp
i k p ph KLN ca vt liu. Do , i tr pH 6 c ch
thc hin cc th nghim i k x l ion kim loi
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