research article adsorption removal of environmental

Research ArticleAdsorption Removal of Environmental Hormones ofDimethyl Phthalate Using Novel Magnetic Adsorbent

Chia-Chi Chang,1 Jyi-Yeong Tseng,1 Dar-Ren Ji,1 Chun-Yu Chiu,2

De-Sheng Lu,1 Ching-Yuan Chang,1,3 Min-Hao Yuan,1,4 Chiung-Fen Chang,5

Chyow-San Chiou,6 Yi-Hung Chen,4 and Je-Lueng Shie6

1Graduate Institute of Environmental Engineering, National Taiwan University, Taipei 106, Taiwan2Department of Cosmetic Science and Application, Lan-Yang Institute of Technology, Yilan 261, Taiwan3Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan4Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, Taipei 106, Taiwan5Department of Environmental Science and Engineering, Tunghai University, Taichung 407, Taiwan6Department of Environmental Engineering, National I-Lan University, Yilan 260, Taiwan

Correspondence should be addressed to Ching-Yuan Chang; [email protected]

Received 13 January 2015; Accepted 16 June 2015

Academic Editor: Zulin Zhang

Copyright © 2015 Chia-Chi Chang et al. This is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properlycited.

Magnetic polyvinyl alcohol adsorbent M-PVAL was employed to remove and concentrate dimethyl phthalate DMP. The M-PVALwas prepared after sequential syntheses of magnetic Fe

3O4(M) and polyvinyl acetate (M-PVAC). The saturated magnetizations of

M, M-PVAC, andM-PVAL are 57.2, 26.0, and 43.2 emu g−1 with superparamagnetism, respectively.The average size of M-PVAL bynumber is 0.75 𝜇m in micro size. Adsorption experiments include three cases: (1) adjustment of initial pH (pH

0) of solution to 5,

(2) no adjustment of pH0with value in 6.04–6.64, and (3) adjusted pH

0= 7.The corresponding saturated amounts of adsorption of

unimolecular layer of Langmuir isotherm are 4.01, 5.21, and 4.22mg g−1, respectively. Values of heterogeneity factor of Freundlichisotherm are 2.59, 2.19, and 2.59 which are greater than 1, revealing the favorable adsorption of DMP/M-PVAL system. Valuesof adsorption activation energy per mole of Dubinin-Radushkevich isotherm are, respectively, of low values of 7.04, 6.48, and7.19 kJmol−1, indicating the natural occurring of the adsorption process studied. The tiny size of adsorbent makes the adsorptiontake place easily while its superparamagnetism is beneficial for the separation and recovery of micro adsorbent from liquid byapplying magnetic field after completion of adsorption.

1. Introduction

Emerging contaminants (ECs), such as hormones, havespread in various environmental media due to wide use ofmaterials or products containing these substances or com-pounds. Most of these contaminants were discharged intoaquatic environments [1–16].The ECs were also found in sed-iments [1, 6, 8, 17, 18], soil [8, 9, 19], air [20, 21], waste [19], andbiota [1, 22, 23].There has been a great ongoing concern, evenat trace levels, on their potential, adverse effects on humanhealth and ecological systems affecting biological and cellmechanisms [1, 3, 9, 11–13, 15, 24]. Among the environmental

hormones encountered, phthalate acid esters or phthalateesters (PAEs) have drawn much attention [18, 20, 21, 25–30].

PAEs are derivatives of phthalate acid. They have beenapplied for the manufacturing of polyvinyl chloride (PVC),polypropylene (PP), polyethylene (PE), and polystyrene (PS)and used as plasticizer, binder, and coating and printing ink[21, 27]. Due to their endocrine disruption effects, manycountries have either regulated the upper limiting concentra-tion or restricted the use of PAEs in plastic toys.The contam-inated sources include plastics factories, industrial and dom-estic wastewater treatment plants, landfills, reviver sediment,and sewage sludge [18, 20, 25, 27–30]. The solubility of PAEs

Hindawi Publishing Corporatione Scientific World JournalVolume 2015, Article ID 903706, 8 pageshttp://dx.doi.org/10.1155/2015/903706

2 The Scientific World Journal

in water is low. Among the commonly used PAEs, dimethylphthalate (DMP) has the solubility in water of 4000mg L−1or 0.4% [31], which is comparatively higher than most ofother PAEs such as di-ethyl phthalate (DEP) (1080mg L−1),di-hexyl phthalate (DHP) (slightly soluble with 0.05% or500mg L−1 max), di-n-butyl phthalate (DBP) (13mg L−1),benzyl butyl phthalate (BBP) (2.69mg L−1), di-(2-ethylhexyl) phthalate (DEHP) (0.3mg L−1), di-iso-nonyl phtha-late (DINP) (<0.01mg L−1), di-cyclohexyl phthalate (DCHP)(negligible solubility), di-n-octyl phthalate (DNOP) (waterinsoluble), and di-iso-decyl phthalate (DIDP) (water insol-uble). Thus, DMP was chosen as a model compound for theremediation of contaminated aquatic water and the treatmentof waste water.

The natural attenuation mechanisms which includechemical breakdown, biodegradation, and photolysis candecompose the PAEs [25]. The halftimes vary from days toyears, depending on the environment especially the temper-ature and the properties of PAEs such as structure and lengthof functional groups. However, it takes a long time. Thus,many techniques have been used to treat the PAEs-containingwater and waste, including physical treatments of adsorption[32, 33] and membrane processes such as ultrafiltration,nanofiltration, and reverse osmosis [34–38], biodegradationby microorganisms [25], and chemical processes of base-catalyzed hydrolysis, ultraviolet (UV) radiation, ozonation,combined UV radiation/ozonation, catalytic ozonation, andcombinedUV/catalytic ozonation [25, 26, 39, 40]. Among theabove said methods, adsorption can effectively remove thePAEs from the solution with PAEs concentrated on the solidadsorbents. The adsorption has been also applied to otheremerging contaminants [41, 42]. The exhausted adsorbentsare regenerated for reuse. The treatment of waste regener-ation solution containing high-concentration PAEs is thenfollowed. It is usually carried out by the destruction processessuch as biological and chemical treatments noted above. Con-cerning the improvement of adsorption rate, proper surfacearea, and easy recovery of adsorbent, adsorption using novelmagnetic micro-nano size magnetic adsorbents has beendeveloped and employed for the removal of inorganic pol-lutants [43–46]. This study applied the micro size magneticpolyvinyl alcohol (M-PVAL) for the adsorption removal oforganic DMP.

2. Experimental

2.1. Chemicals. The main chemicals used to synthesize themicro size adsorbents of magnetic polyvinyl alcohol M-PVAL include the following: iron(III) chloride-6-hydrate(FeCl3⋅6H2O, 99%), iron(II) tetrahydrate (FeCl

2⋅4H2O,

99%), and ammonium hydroxide (NH3, 25%) from Merck

KGaA (Darmstadt, Germany), oleic acid (CH(CH2)7COOH,

extra pure reagent) and polyvinyl alcohol ((CHCH2OH)𝑛,99+%) fromNacalai Tesque, Inc. (Kyoto, Japan), vinyl acetate(CH3COOCHCH

2, 99+%) and divinyl benzene (C

10H10,

80%) from Sigma-Aldrich, Inc. (Steinheim, Germany), ben-zoyl peroxide (C

6H5CO, 99%, Jia Hwa Chemical, Co., Ltd.,

Taipei, Taiwan), and methylene blue (Loba Chemie Pvt. Ltd.,

Mumbai, India). The emerging contaminant of dimethylphthalate DMP (C

10H10O4, 99.5%) was supplied by Hayashi

Pure Chemical Industries Ltd. (Osaka, Japan).

2.2. Methods and Analyses

2.2.1. Preparation of Micro Size M-PVAL. Magnetic Fe3O4

(M) was prepared by chemical coprecipitation method. Fer-rous chloride and ferric chloride were firstly dissolved usingdistilled water at 85∘C in nitrogen environment. It followedthe addition of aqueous ammonia to form the magnetic sus-pension of precipitated Fe

3O4. Oleic acid acting as a disper-

sion agent was immediately and slowly fed into the suspen-sion liquid until the appearance of clear supernatant liquid.This thus yielded the magnetite M. It was then synthesizedto formmagnetic polyvinyl acetate (M-PVAC) by suspensionpolymerization. For performing this, PVAL was dissolved viadistilled water at 60∘C in nitrogen environment to providebackground solution for polymerization. After addition ofmagnetite M, VAC, and divinyl benzene, the suspensionpolymerization proceeded at 70∘C for about 6 h and thencooled to 25∘C, forming M-PVAC. Washing with deionizedwater, its surface was modified by alcoholysis to produce apolymer adsorbent of magnetic polyvinyl alcohol M-PVAL.In alcoholysis, M-PVACwas suspended inmethanol solutionfor 6 h to obtain M-PVAL. Detailed description of the aboveprocedures can be found in Tseng et al. [45].

2.2.2. Isothermal Adsorption. DMP solutions with variousconcentrations were prepared. 0.1 g M-PVAL adsorbent wasadded into each 50mL DMP solution filled in 125mL flask.The initial pH value (pH

0) of solution was adjusted to desired

value using HCl or NaOH.The adsorptions with various ini-tial DMP concentrations were conducted in a constant-bathshaker. A blank solution without M-PVAL adsorbent wastested along each batch of adsorptions.

After the adsorption of 8 h, a magnet was attached benea-th the flask to adhere theM-PVAL adsorbent.The pH value ofsolution was measured. The magnetic separated solution waswithdrawn using syringe and filteredwith 0.22 𝜇mfilter. 2mLfiltrate was collected for the measurement of concentration.

2.2.3. Analyses. The magnetizations of Fe3O4, M-PVAC,

and M-PVAL were measured by superconducting quantuminterference device (SQUID) (model MPMS7, QuantumDesign Inc., San Diego, CA). The Brunauer-Emmett-Teller(BET) surface area and particle size distribution of sampleswere determined by Perkin Elmer’s Micromeritics ASAP2000 (Perkin Elmer, Norcross, GA) and laser particle sizeanalyzer (model LS 23 Fluid Module, Beckman CoulterInc., Fullerton, CA), respectively. The surface structure andfunctional group of solids were analyzed using scanningelectron microscope (SEM) (model JEOL-5610, JEOL Ltd.,Tokyo, Japan) and Fourier-transform infrared spectrome-ter (FTIR) (model FTS-40, BIO-RAD Inc., Hercules, CA),respectively. A zeta potential meter (model Nano-Z, MalvernInc., Worcestershire, UK) was employed to identify thezeta potentials of samples. The concentration of DMP was

The Scientific World Journal 3

−60−50−40−30−20−10

0102030405060

−20 −16 −12 −8 −4 0 4 8 12 16 20Magnetic field (kOe)

Mag

netiz

atio

n (e

mu g

−1)

Figure 1: Magnetization curves of various magnetic particles.I, ◻, and △: Fe

3O4, PVAL: [CH2CH(OH)]𝑛, and PVAC:

[CH2CH(OCOCH3)]𝑛.

measured using UV-spectrophotometer (model UV mini-1240, Shimazu, Kyoto, Japan).

3. Results and Discussion

3.1. Characteristics of Micro Size M-PVAL. Figure 1 illustratesthe magnetization versus magnetic field of Fe

3O4, M-PVAC,

andM-PVAL. All three particles exhibit magnetization at thepresence of magnetic field while they possess no magnetiza-tion in the absence of externally appliedmagnetic field, show-ing the unique characteristics of superparamagnetism. Thisproperty offers the advantages for using the fresh solid adsor-bent to adsorb the solute species in the absence of magneticfield and for removing the exhausted adsorbent from solutionby magnetic separation for subsequent regeneration. Thesaturation magnetizations of Fe

3O4, M-PVAC, and M-PVAL

are 57.2, 26.0, and 43.2 emu g−1, respectively. The saturationmagnetizations of Fe

3O4and M-PVAC are close to those of

Chang et al. [43] of 56.45 emu g−1 and of Tseng et al. [45] of25 emu g−1, respectively. The reduction of saturation magne-tizations ofM-PVACandM-PVAL compared to that of Fe

3O4

with relative magnitudes of 45.45% and 75.52%, respectively,is due to the coating of polymer matter onto Fe

3O4. The

functional group of –OCOCH3of M-PVAC is modified to

–OH of M-PVAL, resulting in less organics contained in M-PVAL.Thus, for the same amount of magnetic adsorbent, thecontent of Fe

3O4in M-PVAL is higher than that in M-PVAC,

possessing a comparatively higher saturation magnetization.The success of synthesis of M-PVAL with functional

group of –OH can be further justified by the peak of adsorp-tion (inverse of transmittance) at 3400 cm−1in FTIR diagrampresented in Figure 2. The peak at 1266 cm−1 also reveals thebinding of C–O. The same characteristics of nonmagneticpolyvinyl alcohol were also reported by Kaczmarek et al. [47]and Majumdar and Adhikari [48].

Figure 3 depicts the particle size distribution of M-PVALin terms of number. The number mean diameter (𝑑PNA) andnumber median diameter (𝑑PNM) are 0.75 and 0.589𝜇m,

0

5

10

15

20

25

30

35

40

40010001600220028003400

3400

4000

Tran

smitt

ance

(%)

Wavenumber (cm−1)

1266

Figure 2: FTIR diagram of M-PVAL.

Table 1: Some major physical characteristics of M-PVAL.

Adsorbent:M-PVAL

Densityanalysis

Bulk density, 𝜌𝑃(g cm−3) 2.40

True density, 𝜌𝑆(g cm−3) 2.49

Particle porosity, 𝜀𝑃

a 0.03

Surfaceareab,c

Surface area by BETanalysis (𝐴

𝐵)

(m2 g−1)73.1

Constant of BETequation (𝐾

𝐵)

(—)63

Particlediameterd(𝜇m)

Average particlediameter by number 0.75

aCalculated using 1 − (𝜌𝑃/𝜌𝑆).bBET surface area was analyzed using ASAP2000, Micromeritics.cSurface area estimated using Langmuir equation (𝐴L) is about102.42m2 g−1.dAnalyzed using LS 23 Fluid Module, Beckman Coulter.

respectively.Most of theM-PVAL particles have size less than1 𝜇m.

The major physical characteristics of M-PVAL are sum-marized in Table 1. The particle porosity 𝜀

𝑃is 0.03, indicating

themicro sizeM-PVAL is essentially nonporous.This ensuresthat the pore diffusion is negligible in adsorption process.

3.2. Isothermal Adsorption of DMP. Langmuir, Freundlich,and D-R isotherms were tested to examine the adsorptionsof DMP on M-PVAL for three cases, namely, Cases 1 and3 with initial pH

0adjusted at 5 and 7 and Case 2 without

adjustment of pH0with pH value in 6.04–6.64, respectively.

At equilibrium, the pH values for the three cases with pH0=

5, 6.04–6.64, and 7 increase to about 7.36–7.87, 6.9–8.05, and7.42–8.39, respectively. This is consistent with the adsorptionof slightly acidic DMP by base M-PVAL, which exhibitspH of 9.1 and zeta potential of −35.6mv when dispersed indeionized (DI) water as illustrated in Figure 4. The values of


Table 2: Values of isotherm parameters and correlation coefficients (𝑟2)a with different initial pH values.

pH0

b Langmuir isotherm Freundlich isotherm Dubinin-Radushkevich isotherm𝑞L (mg g−1) 𝐾L (m

3 g−1) 𝑟L2𝑘F ((mg g−1)(gm−3)−1/𝑛F) 𝑛F 𝑟F

2𝐵D (mol2 J−2) 𝐸D (kJmol−1) 𝑞

𝑚D (mg g−1) 𝑟D2

5c 4.01 0.12 0.97 0.80 2.59 0.92 1.00 × 10−8 7.04 3.8 0.916.04–6.64c 5.21 0.056 0.94 0.60 2.19 0.97 1.19 × 10−8 6.48 3.84 0.907c 4.22 0.15 0.95 0.95 2.59 0.81 0.96 × 10−8 7.19 4.32 0.85a𝑟L2, 𝑟F2, and 𝑟D

2 are correlation coefficients by means of fitting the experimental data to Langmuir, Freundlich, and Dubinin-Radushkevich isotherms,respectively.bThe ranges of the equilibrium concentrations of the experiments performed are 0.61–92.9, 0.82–91.1, and 0.52–91.3mg L−1 for pH0 of 5, 6.04–6.64, and 7,respectively.cThe final pH values of solutions at the end of experiments were about 7.36–7.87, 6.9–8.05, and 7.42–8.39 for pH0 = 5, 6.04–6.64, and 7, respectively.

0123456789

101112131415

Num

ber (

%)

0 1 2 3 4 5 6 7 8 9 10Particle diameter (𝜇m)

(a)

0102030405060708090

100

0 1 2 3 4 5 6 7 8 9 10

Cum

ulat

ive n

umbe

r (%

)

Particle diameter (𝜇m)

(b)

Figure 3: The relationship between (a) differential number % of M-PVAL and 𝑑𝑃and (b) cumulative number % and 𝑑

𝑃.

−50

−40

−30

−20

−10

0

10

20

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14pH

Zeta

pot

entia

l (m

V)

Figure 4: Zeta potentials of M-PVAL at various pH values. I and△: pH values of aqueous solutions containing M-PVAL are (1)controlled with addition of HCl or NaOH and (2) not controlled.

isotherm parameters of corresponding isotherms are listed inTable 2.

The Langmuir isotherm deduces the values of unimolec-ular layer 𝑞L of 4.01, 5.21, and 4.22 g kg−1 for Cases 1, 2, and3, respectively, indicating minor effect of adjustment of pH

0

on the saturation capacity 𝑞L with Case 2without adjustmentof pH

0yielding higher value. The adsorption equilibrium

constants 𝐾L exhibit difference with Cases 1 and 2 withadjustment of pH

0giving higher values. The cause might be

due to the effects of adjustment addition of HCl or NaOH onthe adsorption. The balance of decrease of 𝑞L while increase

of 𝐾L by the adjustment of pH0results in the close adsorp-

tion behaviors for the three cases as depicted in Figures 5, 6,and 7. The 𝑟-squares of model fittings as shown in Figure 8are greater than 0.94, indicating good agreement. The resultsthus suggest performing the adsorption without adjustmentof pH

0.

The heterogeneity factors 𝑛F of Freundlich isotherm obt-ained for the three cases are 2.59, 2.19, and 2.59, respectively.All these values are greater than 1, revealing that the adsorp-tion of the noted DMP/M-PVAL systems is favorable. The𝑘F values are about 0.6–0.95 (mg g−1)(gm−3)−1/𝑛F .The fittingsof Freundlich isotherm as illustrated in Figure 9 are fairlysatisfactory with 𝑟-square higher than 0.81, which, however,is not as good as those of Langmuir isotherm. The goodfitting of Langmuir isotherm for the adsorbent M-PVALmaybe further justified by noting that the M-PVAL is tiny withnumber average particle size of 0.75 𝜇m which exhibits fastadsorption rate with low diffusion resistance thus in favor ofthe formation of thin monolayer.

Applying D-R isotherm for the three cases gives the sat-uration adsorption capacity 𝑞

𝑚D of 3.8, 3.84, and 4.32 g kg−1,respectively. The values are comparable to those of 𝑞L of 4.01,5.21, and 4.22 g kg−1 adopting Langmuir isotherm, furthersupporting the validity of Langmuir isotherm. The adsorp-tion activation energies permole ofD-R isotherm𝐸D are 7.04,6.48, and 7.19 kJmol−1, respectively. The 𝑟-squares of fittingsof D-R isotherm presented in Figure 10 are higher than 0.85,showing fair agreement. The obtained values of 𝐸D of 6.48–7.19 kJmol−1 are lower than those of 8–16 kJmol−1 reported


0

1

2

3

4

5

6

0 20 40 60 80 100

qe

(mg g

−1)

Ce (mg L−1)

Figure 5: The simulations of Langmuir isotherm (—), Freundlichisotherm (- ⋅ -), and D-R isotherm (---) for adsorption of DMP onM-PVAL with pH

0= 5. Final pH = 7.36–7.87. I: experimental data.

0

1

2

3

4

5

6

0 20 40 60 80 100

qe

(mg g

−1)

Ce (mg L−1)

Figure 6: The simulations of Langmuir isotherm (—), Freundlichisotherm (-⋅-), andD-R isotherm (---) for adsorption of DMPonM-PVAL. pH

0= 6.04–6.64. Final pH = 6.9–8.05. I: experimental data.

by Ozcan et al. for the adsorption of ion-exchange form [49].The low values of𝐸D thus support that the adsorption processof DMP/M-PVAL in this study proceeds naturally.

The above results indicate that the equilibrium of DMP/M-PVAL exhibits saturation value. Further, among the threeisotherms examined, the Langmuir isotherm shows the bestagreement and thus is more appropriate to describe theadsorption equilibrium of DMP/M-PVAL system.

4. Conclusions

Some major conclusions may be drawn from the adsorptionremoval of DMP using superparamagnetic micro size adsor-bent of M-PVAL examined in this study as follows:

(1) Fe3O4, M-PVAC, and M-PVAL solid particles pre-

pared possess superparamagnetism with saturationmagnetizations of 57.2, 26.0, and 43.2 emu g−1, respec-tively.Themagnetic particle withmore organic adsor-bent content has lower magnetization.

(2) The M-PVAL can adsorb the DMP under the condi-tion without externally applied magnetic field, whilethe exhausted saturatedM-PVAL can bemagnetically

0

1

2

3

4

5

6

0 20 40 60 80 100

qe

(mg g

−1)

Ce (mg L−1)

∗

Figure 7: The simulations of Langmuir isotherm (—), Freundlichisotherm (- ⋅ -), and D-R isotherm (---) for adsorption of DMP onM-PVAL with pH

0= 7. Final pH = 7.42–8.39. I: experimental data.

×, ∗, and +: 𝑞𝑒versus 𝐶

𝑒with 𝐶

0= 9.55, 40.0, and 102.4mg L−1.

0

5

10

15

20

25

30

0 10 20 30 40 50 60 70 80 90 100Ce (mg L−1)

Ceqe−1

y = 0.2368x + 1.535, r2 = 0.9575y = 0.249x + 2.0227, r2 = 0.9796

y = 0.1917x + 3.3874, r2 = 0.9465

Figure 8: Adsorption of DMP on M-PVAL employing Langmuirisotherm. Cases with pH

0= 5, 6.04–6.64, and 7 are expressed as ◻

(--): 𝑦 = 0.249𝑥 + 2.20227, I (- ⋅ -): 𝑦 = 0.1917𝑥 + 3.3874, and △(—): 𝑦 = 0.2368𝑥 + 1.535.

−1

−0.5

0

0.5

1

1.5

2

−1 0 1 2 3 4 5

ln(q

e)

ln(Ce)

y = 0.3855x − 0.0448, r2 = 0.8158

y = 0.3857x − 0.2154, r2 = 0.9279

y = 0.4555x − 0.4964, r2 = 0.9763

Figure 9: Adsorption of DMP on M-PVAL employing Freundlichisotherm. Cases with pH

0= 5, 6.04–6.64, and 7 are expressed as ◻

(--): 𝑦 = 0.3857𝑥 − 0.2145, I (- ⋅ -): 𝑦 = 0.4555𝑥 − 0.4964, and △(—): 𝑦 = 0.3855𝑥 − 0.0448.


−7−6−5−4−3−2−1

0

(RTln(1 + Ce−1))2

ln(q

e)

0.0E + 00 0.5E + 08 1.0E + 08 1.5E + 08 2.0E + 08 2.5E + 08

y = −9.650E − 09x − 3.804E + 00, r2 = 8.497E − 01

y = −1.007E − 08x − 3.934E + 00, r2 = 9.085E − 01y = −1.189E − 08x − 3.921E + 00, r2 = 9.019E − 01

Figure 10: Adsorption of DMP on M-PVAL employing Dubinin-Radushkevich isotherm. Cases with pH

0= 5, 6.04–6.64, and 7 are

expressed as◻ (--):𝑦 = −1.007𝐸−08𝑥−3.934,I (-⋅-):𝑦 = −1.189𝐸−08𝑥 − 3.921, and△ (—): 𝑦 = −9.950𝐸 − 09𝑥 − 3.804.

separated from the treated liquid for the regenerationby applying externally magnetic field.

(3) Langmuir, Freundlich, and Dubinin-Radushkevich(D-R) isotherms were tested to describe the equilib-rium of DMP/M-PVAL for three cases: (1) adjustinginitial pH (pH

0) at 5, (2) no adjustment of pH with

pH0= 6.04–6.64, and (3) adjustment of pH

0at 7, indi-

cating that Langmuir isotherm offers the best fittingwith good agreement.

(4) The unimolecular layer 𝑞L of Langmuir isotherm is4.01, 5.21, and 4.22mg g−1, respectively, for the threecases examined, suggesting no adjustment of pH

0for

practical application.(5) For the three cases investigated, the adoption of Fre-

undlich isotherm gives heterogeneity factor 𝑛F of 2.59,2.19, and 2.59, respectively, indicating that the saidadsorption is favorable with 𝑛F greater than 1.

(6) The adsorption activation energies per mole 𝐸D of D-R isotherm deduced are, respectively, of low values of7.04, 6.48, and 7.19 kJmol−1 for the three cases studied,supporting the natural occurrence of the adsorptionof DMP/M-PVAL system.

Abbreviations

𝐴𝐵: Surface area by BET analysis

(m2 g−1)𝐴L: Surface area estimated using

Langmuir eq. (m2 g−1)𝐵D: D-R isotherm constant (mol2 J−2)BBP: Benzyl butyl phthalateBET: Brunauer-Emmett-Teller𝐶: Adsorbate concentration in the

liquid phase (gm−3 or mmol L−1)𝐶𝑒: Adsorbate concentration in the

liquid phase at equilibrium (gm−3or mmol L−1)

D-R: Dubinin-RadushkevichD-R isotherm: 𝑞

𝑒= 𝑞𝑚D exp(−𝐵D𝐸

2

𝑃)

DBP: Di-n-butyl phthalateDCHP: Di-cyclohexyl phthalateDEHP: Di-(2-ethyl hexyl) phthalateDEP: Di-ethyl phthalateDHP: Di-hexyl phthalateDIDP: Di-iso-decyl phthalateDINP: Di-iso-nonyl phthalateDMP: Dimethyl phthalateDNOP: Di-n-octyl phthalate𝑑𝑃: Particle diameter𝑑PNA: Number mean diameter𝑑PNM: Number median diameter𝐸D: Adsorption activation energy per

mole of D-R isotherm (kJmol−1),= 1/(2𝐵D)

0.5

𝐸𝑃: Polanyi potential (Jmol−1),

= 𝑅𝑇 ln(1 + 𝐶−1𝑒)

ECs: Emerging contaminantsFTIR: Fourier-transform infrared

spectrometerFreundlich isotherm: 𝑞

𝑒= 𝑘F𝐶

1/𝑛F𝑒

𝐾𝐵: Constant of BET equation (—)𝐾L: Equilibrium constant of Langmuir

isotherm (m3 g−1)𝑘F: Constant of Freundlich isotherm

((mg g−1)(gm−3)−1/𝑛F)Langmuir isotherm: 𝑞

𝑒= 𝑞L𝐾L𝐶𝑒/(1 + 𝐾L𝐶𝑒)

M: Magnetic Fe3O4

M-PVAC: Magnetic polyvinyl acetateM-PVAL: Magnetic polyvinyl alcohol𝑛F: Heterogeneity factor of Freundlich

isotherm (—)PAEs: Phthalate acid esters or phthalate

estersPE: PolyethylenePP: PolypropylenePS: PolystyrenePVC: Polyvinyl chloridepH0: Initial pH value𝑞: Adsorbate concentration in solid

phase (mg g−1 or g kg−1 ormmol g−1)

𝑞𝑒: Adsorbate concentration in solid

phase at equilibrium (mg g−1 org kg−1 or mmol g−1)

𝑞L: Unimolecular layer of Langmuirisotherm (mg g−1 or g kg−1)

𝑞𝑚D: D-R isotherm constant denoting

saturation adsorption capacity(mg g−1 or mmol g−1)

𝑅: Universal gas constant(8.314 Jmol−1 K−1)

𝑟2

L, 𝑟2

F, and 𝑟2

D: Correlation coefficients by meansof fitting the experimental data toLangmuir, Freundlich, and D-Risotherms, respectively


SEM: Scanning electron microscopeSQUID: Superconducting quantum

interference device𝑇: Absolute temperature (K)UV: Ultraviolet.

Greek

𝜀𝑃: Adsorbent porosity𝜌𝑃: Apparent particle density (kgm−3)𝜌𝑠: True particle density (kgm−3)𝜌𝑤: Density of water (kgm−3).

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper.

Acknowledgment

The authors are grateful for the financial support from Min-istry of Science and Technology (formerly the National Sci-ence Council) of Taiwan.

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