A novel solidification technology for heavy metals in electrolytic

manganese residue

Zhong Hong*, Li Changxin, Wang Shuai, Xue Jianrong

College of Chemistry and Chemical Engineering, Central South University, Changsha,

410083

ABSTRACT: Electrolytic manganese residue (EMR) is a potentially harmful

industrial solid waste that comes from the electrolytic manganese industry. As the

landfilling EMR has caused various environmental and storage problems, the

technology for the disposal of EMR has been attracting much attention in the

electrolytic manganese metal industry. In this study, using coal as a reducer, the

thermal decomposition of CaSO4 to produce CaS was carried out in air atmosphere at

different conditions. Results revealed that single-phase CaS was detected in the

product and the optimal synthesis conditions of CaS were as follows: molar ratio of C

and CaSO4 (C/S ratio)=3.0, reaction temperature 1273K and reaction time 2.0h. Under

the optimum conditions, the purity and yield of CaS are up to 94.93% and 95.01%

respectively. Secondly, based on the analysis of leaching characteristics, the EMR

generated in an electrolytic manganese company, situated in western of Hunan

province, China, was CaS immobilized. The optimal conditions for immobilization

process were studied. The results show that the heavy metals in the EMR can be

effectively immobilized under the optimum operation conditions (CaS 15% and

solidification time 3.0h). And the leaching toxicity of the amended EMR can meet the

requirement stipulated in corresponding national standards.

Keywords: Electrolytic manganese residue; calcium sulfide; heavy metal;

solidification

1. Introduction

Electrolytic manganese residue (EMR) is a potentially harmful industrial solid

waste that comes from the electrolytic manganese industry and has rarely been

recycled in large quantities [1]. Since 2000, China has become the largest producer,

consumer and exporter of electrolytic manganese metal (EMM) in the world. China’s

EMM production capacity reached 2.11 million tons [2]. In EMM industry, about 6~9

tons of the solid waste is discharged into the environment per ton of produced EMM

[3]. It is highly questionable if the EMR generated is managed properly. The common

practice in China is collecting the EMR in open sites near the plants. Because EMR

contains some heavy metal elements and compounds, the untreated discharge can

cause serious pollution of surrounding soil and receiving water bodies [4-6]. Heavy

*Corresponding author: Zhong Hong (1961-), Tel.: 0731-88830654, E-mail: zhongh@csu.edu.cn

metals in the EMR are considered as the most hazardous component of the waste

material and the potential toxic effects of these metals on ecological systems have

been the subject of a number of related research efforts [7-9]. It is, therefore, essential

to continuously develop new and advanced technology to solidify the heavy metals in

the EMR.

Phosphogypsum is a waste byproduct from the processing of phosphate rock by

the‘‘wet acid method’’ of fertilizer production, which currently accounts for over 90%

of phosphoric acid production. The main components in phosphogypsum are

CaSO4·2H2O (calcium sulfate dihydrate), CaSO4·1/2H2O (calcium sulfate

hemihydrate) and CaSO4 (calcium sulfate anhydrate) [10,11]. The yield of

phosphogypsum was 4.5~6t per tonphosphoric acid. Every year, more than 30 million

tons of phosphogypsum are generated in China, and less than 10% has been reused

[12,13]. The large amount of phosphogypsum has caused various environmental and

storage problems. Therefore, to achieve a sustainable and environment-friendly

society, it is necessary to develop a new phosphogypsum recycling process. In order

to make full use of the chemical and economic potential of phosphogypsum, reductive

decomposition of CaSO4 with a reducing agent has been studied. So far, the

investigation on reductive decomposition of CaSO4 with H2, C and CO has been

mainly undertaken to generate SO2 for the production of sulfuric acid as well as to

recycle lime (CaO) from phosphogypsum [14,15]. However, there is scanty

information in the literature on reductive decomposition of CaSO4 to CaS, especially

in an air atmosphere. In addition, the decomposition products of CaS can be used in

the process of metal removal from metal-containing wastewater [16]. Therefore, a lot

of work needs to be done to gain a valuable insight into the process of reductive of

CaSO4 to CaS, since CaS can be utilized as a sulfuration agent to solidify the heavy

metals in the EMR.

Given the above, the utilization of phosphogypsum for production of CaS, which

could be subsequently applied in the solidification treatment of EMR, was proposed

in our work. More specifically, an attempt was made to reduce decomposition of

CaSO4 with coal to CaS, which can serve as a solidification agent and a potential

technical assistance for reusing phosphogypsum. Then, the CaS generated from

CaSO4 was used to immobilize heavy metals in the EMR. This study has been carried

out on the elements including Mn, Pb, Zn, Co, Cu, As and Fe, because they are known

for their toxicity and to be present in EMR with sufficiently high concentration. In

addition, X-ray diffraction (XRD) and scanning electron micrograph (SEM) were

used to determine the crystalline phase and morphology of the product synthesized

from CaSO4.

2. Materials and methods

2.1. Material preparation

The CaSO4 used in this study was analytically pure and bought from Aladdin

Industrial Corporation (Shanghai, China). The coal used in the experiment was

obtained from Gansu province; the characteristics were presented in Table 1. The coal

sample was ground and its size range was smaller than 0.147mm. The EMR

investigated in this study was mainly generated in leaching process of the manganese

ore (with part of residue generated in electrolytic cell process) at an electrolytic

manganese company, situated in western of Hunan province, China. The chemical

composition of EMR used in this study is listed in Table 2. The raw slag mainly

consists of Al2O3, SiO2, CaO, MnO and Fe2O3. This chemical composition is fairly

common in EMR produced in China’s EMM industry. Meanwhile, the phase

composition of EMR is shown in Fig. 1 and the phase is very complex in the EMR as

shown by X-ray diffraction (XRD). All experiments were performed using the same

batch of EMR.

Table 1. The characteristics of the coal used in this experiment.

Composition C S ash volatile matter

Content (wt.%) 72.61 0.67 16.59 60.80

Table 2. Major chemical composition of EMR.

Element Na2O MgO Al2O3 SiO2 SO3 K2O CaO MnO Fe2O3 TiO2

Mass(%) 2.70 1.71 12.15 24.60 22.00 2.43 8.59 4.64 7.87 0.41

0 10 20 30 40 50 60 70 80 900

100

200

300

400

500

Inte

nsity

2

1.CaSO4.2H2O

2.SiO2

3.NaAl3(PO4)2(OH)4

4.BaAl3(PO4)(PO3(OH))(OH)6

5.(Mn.Al)3(Si.Al)2O5(OH)4

6.MnSO4.4H2O

1

4

3

61

2

6

1

31

54

1

4 62

5

Fig. 1. XRD pattern of EMR.

2.2. Experimental equipment

The equipment and analysis equipment used in this research were as follows:

muffle furnace (Changsha Changcheng Electric Furnace Factory); Spectrumlab 752s

UV-vis spectroscopy (Shanghai Lengguang Technology Co., Ltd.); X-ray diffraction

(D8 Discover, Bruker, Germany); Field emission scanning electron microscopy

(FE-SEM) (Mira3, Tescan, Czech Republic); ICP-AES (Optima 5300DV,

Perkin-Elmer, USA); pH meter (pHS-3C, Leici, China).

2.3. Synthesis of CaS

The CaSO4 and coal were first mixed in different proportions in a 30ml

ceramic crucible. When the temperature in the muffle furnace was increased from

room temperature to 1173K, the covered ceramic crucible was placed in the middle of

reactor for a certain time. Then, when the products had cooled down, solid products

were collected for further analysis to determine the purity and yield of the CaS. In

order to optimize synthesis conditions, CaS samples were synthesized at different C/S

ratio (2.0~6.0), reaction temperatures (1023~1273K) and reaction times(0.5~5.0h).

After the experiments, the sample residue was collected and CaS content in the

sample was determined using methylene blue spectrophotometric method according

to GB/T 16489-1996. Then, the purity of CaS was calculated by Eq. (1) and the yield

of CaS was calculated by Eq. (2).

100%M

MPurity

Total

CaS (1)

100%72.14n

MYield

4CaSO

CaS

(2)

where MCaS is the mass of CaS in the product after experiment, g；MToatal is the

tatol mass of solid residue after experiment, g; nCaSO4 is the initial molar amount of

CaSO4 in the sample, mol; 72.14 is relative molecular mass of CaS.

In addition, the obtained solid products were analyzed by XRD to investigate the

crystalline phases of as-synthesized CaS.

2.4. Solidification of EMR with CaS

At first, EMR was mixed with water to form EMR slurry and the liquid/solid

(L/S, v/w) ratio was kept at 5.0. Then, a given amount of CaS obtained by the

procedure described in section 2.3 was added into the EMR slurry. The slurry was

stirred for a certain time at room temperature and then allowed to settle for another 10

minutes. Subsequently, the slurry was filtered using a paper filter with a mean pore

size of 0.45µm. The heavy metals concentration and pH value in the filtrate were

measured by ICP and pH meter respectively, as the concentrations of heavy metal and

pH value in the filtrate should be considered due to the potential secondary pollution

to the environment. The filter residue (amended EMR) was dried at a temperature of

378K for 2h, and subjected to leaching toxicity procedure described in section 2.5.

In order to optimize solidification conditions, solidification processes were taken

at different dosages of CaS (5.0%~25.0%) and solidification times (0.5~4.0h).

2.5. Leaching toxicity procedure

Batch leaching test using extraction procedure for leaching toxicity according

to HJ 557-2010 was carried out to investigate the efficiency of CaS to immobilize

heavy metals in the EMR. After 10g of the samples was placed in the polythene

container, 100ml of de-ionized water was added and the container was fixed up and

then vibrated for 8h at room temperature in a horizontal shaker with an oscillating

frequency of 110±10min-1

and the amplitude of 20mm. The samples were allowed to

settle for 16h and then filtered with 0.45 micron cellulose acetate membrane. The

filtrates were acidified with 1ml of HNO3 solution to prevent the metal ion

precipitation and then they were analyzed by inductively coupled plasma atomic

emission spectroscopy (ICP-AES).

3. Results and discussion

3.1. Synthesis of CaS

3.1.1. Effect of molar ratio of C and CaSO4 (C/S ratio)

To investigate the effects of C/S ratio for producing CaS, decomposition tests of

CaSO4 mixed with coal were performed at different C/S ratio in the muffle furnace

when the reaction temperature and reaction time were set at 1223K and 1.0h,

respectively.

Fig. 2 shows the effect of C/S ratio on the CaSO4 reductive decomposition with

coal expressed in terms of purity and yield. It seems from the figure that the C/S ratio

play an important role in the decomposition reaction of CaSO4. As shown in Fig. 2,

the purity and yield presented nearly similar curves along with the different C/S ratio.

The results in Fig. 2 show that as the C/S ratio increased from 2.0 to 3.0, the purity

increased from 37.53% to 64.11%, and reached the maximum amount when the C/S

ratio was 3.0. Afterwards, it decreased with increasing C/S ratio, and reached the

minimum amount of 27.31% at C/S ratio 6.0. Therefore, for the synthesis of CaS from

CaSO4, the optimal C/S ratio was 3.0.

2 3 4 5 620

30

40

50

60

70

80

20

30

40

50

60

70

80

Yie

ld (

%)

Purity

Yield

Pur

ity (

%)

C/S ratio

Fig. 2. Effect of C/S ratio on the synthesis of CaS when the reaction temperature was

1223K and reaction time was 1.0h.

3.1.2. Effect of reaction temperature

The effect of reaction temperature on the decomposition was examined by

varying the reaction temperature from 1023K to 1273K, when the C/S ratio and

reaction time were set at 3.0 and 1.0h, respectively. And the effect of reaction

temperature on the CaSO4 reductive decomposition with coal expressed in terms of

purity and yield was shown in Fig. 3. Obviously, the higher reaction temperature was

favored for the generation of CaS. It was found that the reductive decomposition of

CaSO4 to CaS in the presence of coal was first occurred at temperatures above 1023K

and the purity greater than 0.8 was obtained at a temperature of 1273K. These results

are consistent with the results by the research of Ma et al. [17]. Therefore, the reaction

temperature 1273K was chosen as the optimum condition in the next experiments.

1000 1050 1100 1150 1200 1250 13000

20

40

60

80

100

0

20

40

60

80

100

Yie

ld (

%)

Pur

ity (

%)

Reaction temperature/K

Purity

Yield

Fig. 3. Effect of reaction temperature on the synthesis of CaS when the C/S ratio was

3.0 and reaction time was 1.0h.

3.1.3. Effect of reaction time

The effect of reaction time on the decomposition was examined by varying the

reaction time from 0.5h to 5.0h, when the C/S ratio and reaction temperature were set

at 3.0 and 1223K, respectively. It is seen from the Fig. 4 that the purity and yield are

largely depended on the reaction time. As shown in Fig. 4, the purity and yield follow

the trend that no additional increase in purity and yield value was obtained when the

reaction time was further increased beyond 2.0h. When reaction time was higher than

2.0h, the purity and yield decreased abruptly. Therefore, for the synthesis of CaS from

CaSO4, the optimal reaction time was 2.0h.

0 1 2 3 4 50

20

40

60

80

100

0

20

40

60

80

100

Yie

ld (

%)

Pur

ity

(%)

Reaction time/h

Purity

Yield

Fig. 4. Effect of reaction time on the synthesis of CaS when the C/S ratio was 3.0 and

reaction temperature was 1273K.

3.1.4. XRD analysis

To further determine the composition of the solid products after the reduction of

CaSO4 by coal at different reaction time, the crystalline phases of the solid products

synthesized under C/S ratio=3.0 and reaction temperature 1273K were illustrated by

XRD (Fig. 5). It can be seen in Fig. 5 that when the reaction time is 2.0h, the products

are nearly pure CaS. Both XRD test and purity data mentioned above prove that

CaSO4 is completely decomposed to generate the target product of CaS. With an

increase of the reaction time, the compound intensity of CaSO4 decreased distinctly

and the intensity of CaS increased, which further explained the experimental data

analyzed above. This behavior can be explained by the fact that a longer reaction time

may helpful for gasification of C to CO and then producing CaS.

3.1.5 SEM analysis

The morphology and particle size of the CaS synthesized under optimal

conditions (C/S ratio=3.0, reaction temperature 1273K and reaction time 2.0h) were

observed by FE-SEM (Fig. 6). It clearly shows that only leaf-shaped particles, which

are highly dispersed of small particles of micrometer scale, were observed for the

synthesized CaS. Therefore, as far as could be determined by either X-ray diffraction

(XRD) or scanning electron micrograph (SEM) analysis, the only solid product

formed during the induction period was CaS.

0 10 20 30 40 50 60 70 80 900

1000

2000

3000

Inte

nsi

ty

2

1.CaSO4

2.CaS

1

2

1

2

2

2

2

(a) 0.5h

0 10 20 30 40 50 60 70 80 900

1000

2000

3000

4000

5000

Inte

nsi

ty

2

1.CaSO4

2.CaS

2

2

1

2

2

12

(b) 1h

0 10 20 30 40 50 60 70 80 900

1000

2000

3000

4000

5000

Inte

nsi

ty

2

2.CaS

2

2

2

2

2

2

(c)1.5h

0 10 20 30 40 50 60 70 80 900

1000

2000

3000

4000

5000

Inte

nsi

ty

2

2.CaS

2

2

2

2

2

2

(d) 2h

Fig. 5. XRD pattern of the CaS synthesized at different reaction time when the C/S

ratio was 3.0 and reaction temperature was 1273K.

Fig. 6. FE-SEM images of CaS synthesized under optimal conditions (C/S ratio=3.0,

reaction temperature 1273K and reaction time 2.0h).

3.2. Solidification treatment of EMR with CaS

3.2.1. Effect of dosage of solidification agent

The effect of the dosage of CaS on the immobilization efficiency of the heavy

metals in the EMR was investigated and the results are summarized in Tables 4 and 5.

For this purpose, amounts of CaS between 5 and 25% were taken, while the

solidification time was set at 3.0h.The aim of batch leaching experiment was to

determine the efficiency of CaS to immobilize heavy metals and the required

percentage of CaS to add to EMR.

As seen in Tables 4 and 5, it is clearly shown that the amended EMR samples

showed significant reduction in heavy metals leachability compared to unamended

EMR. The immobilization efficiency increases as more CaS were used. CaS at 15%

(w/w) significantly reduces the extractable heavy metals in leaching toxicity

procedure, which is comparable with that at 20% or 25% (w/w) of CaS. As a

compromise between the immobilization efficiency and amendment cost, 15% CaS

was chosen as the amendment ratio for the next experiments. When EMR mixed with

15% CaS, the concentrations of leached heavy metals were both in the limits

stipulated in GB3838-2002. The immobilization efficiency of heavy metals in the

EMR were both close to 100%. However, as for the untreated EMR, Mn, Pb, Zn and

Fe concentrations exceed the regulatory limit stipulated in GB3838-2002, which was

in the class of high potential risk to the surrounding water bodies such as rivers and

lakes.

Regarding the reaction mechanism, the Eqs.(4)-(8) were considered to take place

[18,19]:

22 SCaCaS (3)

MeSSMe 2-2 (4)

222 Ca(OH)Ca(HS)O2H2CaS (5)

2HSCaCa(HS) 2

2 (6)

HMeSHSMe -2 (7)

In addition, the pH value of the mixture as determined by CaS dosage was shown

in Fig. 7. As seen in Fig. 7, the increasing CaS dosage will induce an increase in the

pH of the amended EMR due to the generation of Ca(OH)2 from CaS according to Eq.

(5). The pH of the amended sludge should be considered, since it was generally

believed that the leachability and bioavailabity of heavy metals from EMR is greatly

depended on pH. It has been concluded that the pH of the EMR has a significant

effect on the immobilization efficiency, which increases with increasing pH. It was

found in Fig. 7 that, pH of the amended EMR reach 9.82 at solidification agent of 15%

which was suitable for land application [20]. The results mentioned above seem to

prove that EMR could be effectively solidified using CaS.

0 5 10 15 20 25

5

6

7

8

9

10

11

pH

Mass ratios of solidification agent to EMR (w/w, %)

Fig. 7. The effect of the dosage of CaS on pH valuein the filtrate.

Table 4 The concentrations of heavy metals in the filtrate obtained in the

solidification process. Mass ratios of

CaS to

EMR(w/w, %)

The concentrations of heavy metal in the filtrate, mg/L

Mn Pb Zn Co Cu As Fe

5 2.04 ND 0.43 ND 0.02 ND 0.69

10 0.65 ND 0.38 ND ND ND 0.14

15 ND ND 0.04 ND ND ND 0.03

20 ND ND ND ND ND ND ND

25 ND ND ND ND ND ND ND

limits* ≤0.1 ≤0.1 ≤2.0 / ≤1.0 ≤0.1 ≤0.3

ND: Not detected (detection limit: 1μg/L);

*Pollution concentration limits stipulated in environmental quality standards for surface water

(GB3838-2002);

/ Not specified by State Environmental Protection Administration of China (SEPA) in GB3838-

2002.

Table 5 Concentration of heavy metals in the leachate of unamended andamended

EMR via leaching toxicity test. Mass ratios of

CaS to EMR

(w/w, %)

The concentration of heavy metals in the leachate, mg/L

Mn Pb Zn Co Cu As Fe

0 359.6 0.11 3.09 5.01 0.23 0.10 0.33

5 4.72 0.05 0.06 ND ND ND 0.06

10 0.24 ND 0.03 ND ND ND 0.03

15 0.05 ND 0.03 ND ND ND 0.02

20 0.02 ND ND ND ND ND ND

25 ND ND ND ND ND ND ND

Limits* ≤0.1 ≤0.1 ≤2.0 / ≤1.0 ≤0.1 ≤0.3

3.2.2. Effect of solidification time

The effect of the solidification time on the immobilization efficiency of the

heavy metals in the EMR was investigated and the results are summarized in Tables 6

and 7. The results in Table 6 show that as the solidification time increased from 0.5 to

4.0h, the concentrations of heavy metals in the filtrate obtained in the solidification

process decreased obviously. When the solidification time reached up to 3.0h, the

concentration of heavy metals in the filtrate can meet the limits provided in the

GB3838-2002. Meanwhile, the leaching tests for amended EMR prepared under

different solidification time are presented in Table 7. Table 7 shows that leaching

levels of heavy metals were significantly reduced in the amended samples. And the

heavy metals concentrations were well below the recommended reporting limit set in

the GB3838-2002, when the solidification time was more than 3.0h. Values below the

reporting limit are considered to be within typical values found in rocks and soils, and

are nonhazardous to humans. On the other hand, Fig. 8 shows the pH in the filtrate as

a function of solidification time. pH value of the filtrate was observed to increase as

the solidification time was increased owing to the gradually hydrolysis of CaS as

shown in Eq. (5).

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

8.4

8.6

8.8

9.0

9.2

9.4

9.6

9.8

10.0

pH

Solidification time/h

Fig. 8. The effect of the solidification time on pH value in the filtrate.

Table 6 The concentrations of heavy metal in the filtrate obtained in the solidification

process.

Solidification

time, h

The concentrations of heavy metal in the filtrate, mg/L

Mn Pb Zn Co Cu As Fe

0.5 199.9 0.05 0.04 0.05 0.102 ND 1.268

1.0 0.40 0.01 ND 0.04 0.05 ND 0.04

2.0 ND 0.006 ND 0.03 ND ND 0.03

3.0 ND ND ND ND ND ND 0.03

4.0 ND ND ND ND ND ND ND

limits* ≤0.1 ≤0.1 ≤2.0 / ≤1.0 ≤0.1 ≤0.3

Table 7 Concentration of heavy metals in the leachate of amended EMR via leaching

toxicity test.

Solidification

time, h

The concentration of heavy metals in the leachate, mg/L

Mn Pb Zn Co Cu As Fe

0.5 9.64 0.06 1.09 2.01 0.09 0.07 0.45

1.0 3.72 0.05 0.36 0.24 ND ND 0.06

2.0 0.24 ND 0.03 ND ND ND 0.03

3.0 0.05 ND 0.03 ND ND ND 0.02

4.0 0.03 ND ND ND ND ND ND

Limits* ≤0.1 ≤0.1 ≤2.0 / ≤1.0 ≤0.1 ≤0.3

4. Conclusions

The synthesis of CaS from CaSO4 and its application as a solidification agent for

EMR immobilization were investigated in this study. In the light of the test results, the

following conclusions could be made:

(1) The reductive decomposition of CaSO4 for producing CaS is affected by C/S

ratio, reaction temperature and reaction time. Results revealed that single-phase CaS

was detected under the optimal synthesis conditions of CaS (C/S ratio=3.0, reaction

temperature 1273K and reaction time 2.0h). And under optimum conditions, the purity

and yield are up to 94.93% and 95.01% respectively.

(2) Mn, Pb, Zn and Fe concentrations exceed the regulatory limit stipulated in

GB3838-2002 via leaching toxicity procedure for the EMR, which was in the class of

high potential risk to the surrounding water bodies such as rivers and lakes.

(3) CaS amendment can effectively immobilize the heavy metals in the EMR.

When the dosage of CaS and solidification time are 15% and 3.0h respectively,

leaching levels of heavy metals in the amended EMR were significantly reduced and

leaching concentrations of the heavy metals for the amended EMR can meet the

requirement stipulated in GB3838-2002.

(4) Although more detailed works need to be done before practical applications

can be realized, we believe that this process would be a key technology that offers

novel solutions to waste management and environmental problems.

Acknowledgements

The authors are grateful for the National Natural Science Foundation of China

(No.21376273), the Major Project of Science and Technology of Hunan Province

(No.2010FJ1011) and the Foundation for Science and Technology Commission

Research Project of Chongqing (No.cstc2012ggB90002) by offering the research

fund.

References

[1] K. Hagelstein, Globally sustainable manganese metal production and use, J.

Environ. Manage. 90 (12) (2009) 3736-3740.

[2] N. Duan, Z. Dan, F. Wang, C.X. Pan, C.B. Zhou, L.H. Jiang, Electrolytic

manganese metal industry experience based China’s new model for cleaner

production promotion, J. Clean. Prod. 19 (17) (2011) 2082-2087.

[3] T.M. Liu, H. Zhong, X.R. Yin, Research of resource utilization of electrolytic

manganese slag, China’s Manganese Industry 30 (2012) 1–6.

[4] C.J. Horng, P.H. Horng, S.C. Lin, J.L. Tsai, S.R. Lin, C.C. Tzeng, Determination

of urinary beryllium, arsenic, and selenium in steel production workers, Biol.

Trace Elem. Res. 88 (3) (2002) 235-246.

[5] N. Hu, J.F. Zheng, D.X. Ding, J. Liu, L.Q. Yang, J. Yin, G.Y. Li, Y.D. Wang, Y.L.

Liu, Metal pollution in Huayuan River in Hunan Province in China by manganese

sulphate waste residue, Bull. Environ. Contam. Toxicol. 83 (4) (2009) 583-590.

[6] N. Duan, W. Fan, C.B. Zhou, C.L. Zhu, H.B. Yu, Analysis of pollution materials

generated from electrolytic manganese industries in China, Resour. Conserv.

Recy. 54 (8) (2010) 506-511.

[7] F.A.B. Canuto, C.A.B. Garcia, J.P.H. Alves, E.A. Passos, Mobility and ecological

risk assessment of trace metals in polluted estuarine sediments using a sequential

extraction scheme, Environ. Monit. Assess. 185 (7) (2013) 6173-6185

[8] S.K. Sundaray, B.B. Nayak, S. Lin, D. Bhattac, Geochemical speciation and risk

assessment of heavy metals in the river estuarine sediments—a case study:

Mahanadi basin, India, J. Hazard. Mater. 186 (2) (2011) 1837-1846.

[9] C. Yan, Q. Li, X. Zhang, G.X. Li, Mobility and ecological risk assessment of

heavy metals in surface sediments of Xiamen Bay and its adjacent areas, China,

Environ. Earth. Sci. 60 (7) (2010) 1469-1479.

[10] J.L.Rei, Cleaner phosphogypsum coal combustion and waste incineration ashes

for application in building materials: a review, Build. Environ. 42 (2) (2006)

1036–1042.

[11] M.Y. Xi, Comprehensive utilization of phosphogypsum, Environ. Sci. Technol.

11 (3) ( 2001) 11–13.

[12] S.C. Zheng, P. Ning, L.P. Ma, X.K. Niu, W. Zhang, Y.H. Chen, Reductive

decomposition of phosphogypsum with high-sulfur-concentration coal to SO2 in

an inert atmosphere, Chem. Eng. Res. Des. 89(12) (2011) 2736-2741.

[13] Z. Xu, H. Chang, J. Wu, The economic benefit and technical difficult problems in

the project of sulfuric acid production from phosphogypsum, Phosphate &

Compound Fertilizer 23 (6) (2008) 63-64.

[14] L.P. Ma, X.K. Niu, J. Hou, S.C. Zheng, W.J. Xu, Reaction mechanism and

influence factors analysis for calcium sulfide generation in the process of

phosphogypsum decomposition,Thermochim. Acta526 (1) (2011) 163-168.

[15] S. Okumura, N. Mihara, K. Kamiya, S. Ozawa , M.S. Onyango, Y. Kojima, H.

Matsuda, Recovery of CaO by reductive decomposition of spent gypsum in a

CO-CO2-N2 atmosphere,Ind.Eng. Chem. Res. 42(24) (2003) 6046-6052.

[16] T. Fukuta, T. Ito,K. Sawada,Y. Kojima, H. Matsuda, K. Yagishita, Improvement

of nickel-precipitation from aqueous nickel solution by sulfuration with sodium

sulfides,J. Chem. Eng. Jpn. 36(4) (2003) 493-498.

[17] L.P. Ma, P. Ning, S.C. Zheng,Reaction mechanism and kinetic analysis of the

decomposition of phosphogypsum via a solid-state reaction, Ind. Eng. Chem. Res.

49(8) (2010) 3597-3602.

[18] B.M. Kim, P.A. Amodeo, Calcium sulfide process for treatment of metal‐

containing wastes, Environ. Prog. 2(3) (1983) 175-180.

[19] N. Mihara, K. Soya, D. Kuchar, T. Fukuta, H. Matsuda, Utilizationof

calciumsulfidederivedfrom waste gypsum board for metal-containing wastewater

treatment, Global NEST 10 (1) (2008) 101-107.

[20] Z. Liang, X.J. Peng, Z.K. Luan, Immobilization of Cd, Zn and Pb in sewage

sludge using red mud, Environ. Earth. Sci. 66 (5) (2012) 1321-1328.

电解锰渣中重金属的固化新技术

钟宏*，李昌新，王帅，薛建荣

中南大学化学化工学院，湖南长沙，410083

摘要：电解锰渣是电解金属锰生产过程中产生的浸出渣，其中含有大量重金属，

引发了大量的环境问题。本文采用煤为还原剂，将硫酸钙还原制备硫化钙焙砂，

研究了还原剂中 C 元素与硫酸钙的摩尔比（C/S）、反应温度、反应时间对硫化

钙焙砂纯度和收率影响。结果表明：当 C/S=2.5，反应温度为 1273K，反应时间

为 2.0h 时，硫化钙焙砂中硫化钙纯度和收率分别可达 94.93%和 95.01%。以湘西

某电解锰厂的电解锰渣为原料，在分析其浸出特性的基础上，研究固化工艺对电

解锰渣中重金属离子浸出率的影响，结果表明，利用硫化钙焙砂能有效地固定锰

渣中的重金属，固化体浸出液中的重金属浓度明显降低。当硫化钙焙砂用量为电

解锰渣质量的 15%；固化反应时间为 3.0h 时，电解锰渣中的锰、铅、锌、钴、

铜、砷、铁的固化率均接近 100%，固化后电解锰渣的浸出毒性符合相关国家标

准。