This paper is adresses on treatment of sulphuric acid waste solutions obtained during the conventional copper metallurgical activities. Mother liquor is a part of this solutions and it is generated during the regeneration process of copper bleed solution. Copper, nickel and sulphuric acid are the main components and the other registered impurities are: As, Se, Fe, Sb, Zn, Bi, Pb, Cl ions. Aim to copper removing from the mother liquor, the decopperization process on the industrial scale equipment, is investigated. Investigation was done using the rectangular insoluble lead anodes alloyed with 6 wt.% of antimony at current value of 13 000 A, identical to the current in a commercial copper refinery plant. A few parameters as so as: current, cell voltage, electrolyte temperature, electrolyte flow rate, level of electrolyte, were monitored during the test. Comparing the values of copper content in the solution before and after the decopperization of copper, it was found that it decreased of about 80 wt. % of the initial value. Chemical characterization of the sludge obtained on cathode has shown that it is a material with copper content of about 90 wt. %

Gvozdenović, Milica

Jonović, R.

Jugović, Branimir

Marković, Radmila

Stevanović, Jasmina

Digital Repository of the Institute of Technical Sciences of SASA

Slovak Society of Chemical Engineering
Institute of Chemical and Environmental Engineering
Slovak University of Technology in Bratislava
PROCEEDINGS
39th International Conference of Slovak Society of Chemical Engineering
Hotel Hutník
Tatranské Matliare, Slovakia
May 21–25, 2012
Editor: prof. J. Markoš
ISBN: 978-80-89475-04-9, EAN: 9788089475049
Markovic, R., Stevanovic, J., Gvozdenovic, M., Jugovic, B., Jonovic, R.: Decopperization process of waste
solutions from conventional copper electrolysis, Editor: Markoš, J., In Proceedings of the 39th Interna-
tional Conference of Slovak Society of Chemical Engineering, Tatranské Matliare, Slovakia, 292–297,
2012.
DECOPPERIZATION PROCESS OF WASTE SOLUTIONS FROM 
CONVENTIONAL COPPER ELECTROLYSIS 
 
R. Marković1, J. Stevanović2, M. Gvozdenović3, B. Jugović4, R.Jonović1 
 
1MMI, Mining and Metallurgy Institute Bor, 19210 Bor, Serbia 
2ICTM, Institute of Electrochemistry, University of Belgrade, 11000 Belgrade, Serbia 
3Faculty of Technology and Metallurgy, University of Belgrade, 11000 Belgrade, Serbia 
4ITS-Serbian Academy of Science and Arts, 11000 Belgrade, Serbia 
 
 
Key words: decopperization, mother liquor, waste solution, sludge 
 
ABSTRACT 
 
This paper is adresses on treatment of sulphuric acid waste solutions obtained during the 
conventional copper metallurgical activities. Mother liquor is a part of this solutions and it is 
generated during the regeneration process of copper bleed solution.  Copper, nickel and sulphuric 
acid are the main components and the other registered impurities are: As, Se, Fe, Sb, Zn, Bi, Pb, 
Cl ions. Aim to copper removing from the mother liquor, the decopperization process on the 
industrial scale equipment, is investigated. Investigation was done using the rectangular 
insoluble lead anodes alloyed with 6 wt.% of antimony at current value of 13 000 A,  identical to 
the current in a commercial copper refinery plant. A few parameters as so as: current, cell 
voltage, electrolyte temperature, electrolyte flow rate, level of electrolyte, were monitored during 
the test. Comparing the values of copper content in the solution before and after the 
decopperization of copper, it was found that it decreased of about 80 wt. % of the initial value. 
Chemical characterization of the sludge obtained on cathode has shown that it is a material with 
copper content of about 90 wt. %..  
 
1. INTRODUCTION 
Practically, all human societies depend on the availability and possibility to use the various 
natural resources. Extraction of copper minerals that is primarily based on mining and 
metallurgy, in order to obtain the basic and precious metal has a long history in the territory of 
Western Balkan (1). Also, the fact that thanks to the quantities of confirmed mining reserves of 
700 million tons, as so as the reserves of Au and other precious metals, the mining and 
metallurgical activities at this site could be expected in the future. 
A series of copper mining and metallurgical activities begins with mining of copper bearing ore 
and ends with the production of cathode copper, causes the serious environmental pollutions in 
this area such as contamination of soil, groundwater and local waterways, the Danube River, air.  
Mother liquor is a part of the waste solution from the conventional copper electrolysis that is 
generated during the regeneration process of copper bleed solutions. Copper concentration limit 
in the mother liquor was in range of values from 9 to 22 g dm-3 and H2SO4 in range from 323 to 
489 g dm-3.  
The main problem related to the processing of waste solution is to find the appropriate 
technology that will be applied before the release of solutions in local waterways. In recent 
years, the alternative to chemical precipitation process is the electrochemical and 
39th International Conference of SSCHE
May 21–25, 2012, Tatranske´ Matliare, Slovakia Po-Tu-4, 201.pdf
292
hydrometallurgical processes. Electrochemical processes of metal removal from waste solutions 
are the special interest of researchers in the last decade [2-4]. 
In this work, the mother liquor generated during the regeneration process of copper bleed 
solutions obtained in the conventional process of copper electrolysis are electrochemically 
treated using the insoluble anodes. Alloying plates of lead with antimony was used as insoluble 
anode aimed to increase the hardness of alloy, reduce corrosion, improve conductivity and 
reduce the anodic polarization, a preventive effect on preventing the formation of PbO [5,6]. 
 
2. EXPERIMENTAL PART 
 
2.1.1 Equipment parts 
 
Electrolytic copper decopperization from mother liquor was carried out on the industrial scale 
plant, located in conventional Tank House, whose parts are: 
a) Collecting tank - working volume is 8 m3 
b) Electrolytic cell –the number of cells is 4 pieces in two groups and the cell volume with the 
electrodes is ∼ 15 m3 
c) Commercial tank - the working volume is about 24 m3 
d) Head tank - working volume is about 0.5 m3  
e) Chemical pump - capacity is 45 m3/h,  
f) Plate heat exchanger  
g) Piping system  
g) Sludge tank - the maximum working capacity is about 3.83 m3 and the minimum is 
approximately 0.34 m3. 
 
2.1.2. Technological procedure 
 
After the electrodes, cathode sheet from the cathode copper and rolled lead sheet with 6 wt. % Sb 
as anode, were put in the cells, interracial electrode distance of 100 mm was controlled. Rakes 
and cranes in the Tank House are used to put in the insoluble anodes in the cells, cell voltage was 
measured before the cells were connecting with current source with working current of 13000 A 
and determined the chemical composition of the solution. Mother liquor is transported from 
collecting tank into commercial tank, by gravitational pipeline system. Supplying of the cells 
with the solution is above, using pump and distribution systems, and the overrun of solution from 
the cell was over the overflow box. The circulation of solution was ~ 2.5 cell volume changes 
per hour. After circulation system stabilization, the cells have been included in the electrical 
circuit. The technological parameters are controlled during decopperization process, the solution 
working temperature was 55-60 oC, and calculated value for process duration was 400 min. Plate 
heat exchanger was used for solution heating and piping system was used for mother liquid 
transport from the collection tank to the commercial tank.  Solution volume that was transported 
is regulated by automatic valve. Decopperized solution is discharged from the cell by opening 
the electrolyte plug, located at the suitable height from the cell bottom and using return pipeline 
transported into the commercial tank. Pulp of copper sludge is discharged by opening the slime 
plug, located on the cell bottom and with pipeline for slime, transported into sludge tank. 
Analysis of copper and sulfuric acid was performed each hour. The process was stopped at the 
moment of occurrence the toxic gas - AsH3, by interrupting the circuit. The working volume 
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293
solution of ∼ 24 m3 was circulated for about thirty minutes aim to unification the composition 
and sampling for chemical analysis. Toxic emissions that occur during the process are high. 
During the process, the appearance of arsine (AsH3) was qualitatively examined by 5 % solution 
of mercuric chloride. Volume of solution was not corrected during the process but only at the 
end. The water evaporation from the cell surface was about 2 kg m -2h-1. 
 
Table 1. Technological parameters of mother liquor decopperization process 
Working process characteristics 
First cells group, Ia/b cell Second cells group, IIa/b cell 
Cathode number  34 pcs. Cathode number,  31 pcs. 
Total cathode surface 53.2 m2 Total cathode surface 48.5 m2 
Cathode current density 244.36 A m-2 Cathode current density 268.04 A m-2 
Anode surface for 35 pcs. 47.88  m2 Anode surface for 32 pcs. 42.41 m2 
Cell volume with electrodes 3.85 m3 Cell volume with electrodes 3.86 m3 
Measurement during the decopperization process 
First cells group, Ia/b cell Second cells group, IIa/b cell 
Average cell voltage, I a cell 2.53 V Average cell voltage, II a cell 2.66 V 
Average cell voltage, I b cell 2.6 V Average cell voltage, II b cell 2.63 V 
Average solution temperature  58 oC Average solution temperature  58.5 oC 
 
3. RESULTS AND DISCUSSION 
 
3.1. Electrolytic decopperization of mother liquor 
 
The waste solutions that were collected at the facility for the regeneration of copper electrolyte 
are: 
 -  water generated in places where the industrial water uses (water pump seal, vacuum pumps 
refrigeration, washing floors, washing unit, filter washing, overflow of cooling tower) 
- water obtained during  evaporation – acid condensate  
- waste copper electrolyte – mother liquor 
Waste copper electrolyte – mother liquor, that remains after the copper sulfate production, is the 
only from the waste solution with a certain amount of copper, sulfuric acid, and harmful and 
hazardous substances so that these solutions have to previously purified to quality limits 
corresponding to the current legislation prior to discharge into the local waterways [7]. Copper 
concentration limit in the mother liquor was in range of values from 9 to 22 g dm-3 and H2SO4 in 
range from 323 to 489 g dm-3. Solution density at the beginning of the process is 1.28 g cm-3. 
Results of chemical characterization of mother liquor before and after decopperization process 
are present in Table 2. The results present the average composition of the solution followed by a 
period of 5 years. 
 
Table 2. Chemical characterization of mother liquor before and after decopperization process 
Components Concentration initial, g dm-3 final,  g dm-3 
Cu 13.14 2.68 
H2SO4 432.36 440.09 
Ni 3.07 3.36 
39th International Conference of SSCHE
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294
Fe 0.82 0.65 
As 0.8 0.56 
Cl- 0.053 0.084 
Zn 0.049 0.044 
Sb 0.04 0.039 
Te 0.029 0.018 
Sn 0.009 0.009 
Bi 0.0085 0.0022 
Pb 0.0012 0.0012 
Se 0.002 0.001 
 
Electrolysis of copper using insoluble anodes could be described as the deposition of copper 
from the copper electrolyte due to the direct current passage.  
During the decopperization process, the following reactions take place on the electrodes: 
 Cathode: Cu2+ + SO42-+2e = Cu + SO42-       (1) 
 Anode: 2OH-= ½ O2 + 2H+ + 2e        (2) 
During the process, oxygen is separated at the anode and the excess hydrogen ions remain in the 
solution and react with sulfate ions that in the anode space come with the help of direct current, 
with result in the generation of sulfuric acid. This means, that the separation of each equivalent 
of copper deposited on the cathode, creating the equivalent of sulfuric acid and releases the 
equivalent of oxygen at the anode, due to the reaction: 
 (Cu2+ + SO42-) + H2O = Cuo + 2H++ SO42- + ½ O2      (3) 
 
Table 3. Measurements after mother liquor decopperization process 
Duration of experiment, h 6.66 
Deposit character 
Cathode sheet is covered with 
black slime, which is 
removable 
Cu content in copper sludge, wt. % 91.17 
Solution density, g cm-3 1.27 
Cathode current efficiency based on the 
analysis of electrolytes, % ∼ 60 
Consumption of ampere hours, Ah 346320 
The specific power consumption, kWh/tCu 3513 
 
During the decopperization with insoluble anodes (Pb +6 wt. % Sb), copper concentration is 
constantly decreasing, and H2SO4 increases. Copper is deposited to the cathode sheet, all the 
time in the area of limiting diffusion current deposition. According to this fact, cathode deposit is 
in a powder form with a possibility of self shaking. Parallel with the reaction of copper 
deposition, the copper concentration in the working solution decreases and the reaction of 
hydrogen evolution is carried out [8,9,10,11]. Arsenic from the electrolyte in the presence of 
hydrogen chemically reacts to form toxic gas arsine (AsH3). Achieved effects of treatment the 
mother liquor using insoluble anodes are: reducing of copper concentration is up to level of 
nickel concentration (12) and production of cathode powder deposit that falls from the cathode 
surface during the decopperization process on the bottom of the cells.  
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Physical and chemical characterization of the obtained cathode deposit- sludge is shown in Table 
4. 
 
Table 4. Chemical and physical characterization of cathode deposit –sludge 
Chemical characterization Physical characterization 
Element Content, wt. % Particle size, µm Wt. % 
Cu 91.17 +250 13.64 
Pb 0.31 - 250+75 50.24 
As 0.18 - 75+45 16.4 
Se 0.15 - 45 18.6 
Sb 0.075   
Si 0.031   
Fe 0.019   
Te 0.014 Apparent density, g cm-3 2.46 
 
The results of X-ray analysis showed that the elemental copper and cuprites are present in the 
sample of copper sludge sample. Duration of decopperization process and limiting copper 
concentrations in solution were conditioned by the appearance of arsine (AsH3) at working area. 
Qualitatively, the presence of arsine was observed from the beginning of the process by reaction 
with a solution of HgCl2 and by analysis of solution on Cu and H2SO4 is controlled the 
decopperization degree of mother liquor. The decreasing of Cu concentration is resulted in 
increased hydrogen evolution at the cathode; arsine occurrence was the reason for the process 
interruption.  
Based on data on the initial and final Cu concentration as well as solution working volume, was 
calculated the decopperization degree of the mother liquor which amounts to 80 wt. %. 
Calculation of the cathode current efficiency, which was based on differences of copper 
concentration in solution, provided the values of about 60 %. 
Analysis of copper sludge composition indicates a high copper content and low content of 
accompanying elements. 
   
4. CONCLUSION 
 
During the process of electrolytic decopperization the mother liquor, the copper sludge with 
copper content over 90 wt. % was obtained. Based on data on the initial and final Cu 
concentration, as well as solution working volume, was calculated the decopperization degree of 
the mother liquor which amounts to 80 wt. %. Calculation of the cathode current efficiency, 
which was based on differences of copper concentration in solution, provided the values of about 
60 %. Copper sludge and decopperized solution could be used for further chemical treatment in 
the aim to copper and nickel salts production. 
 
Acknowledgment 
This work is financially supported by the Ministry of Science, Republic of Serbia: “The Impact 
of Mining Waste from RTB Bor on the Pollution of Surrounding Waterways with the Proposal of 
Measures and Procedures for Reduction the Harmful Effects on The Environment”, No. TR 
37001. 
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5.REFERENCES 
[1] Mining and Environment in the Western Balkans, May 3, 2010; ENVSEC Initiative at CSD 
18 in New York, ENVSEC, Editor: Christina Stuhlberger 2010., 43-51;  
[2] K. Juttner, U. Galla, H. Schmieder, Electrochemical Approaches to the Environmental 
Problems in the Process Industry, Electrochemica Acta, (2000) Vol.45, 2575–2594. 
[3] J. Dziewonski, et al., Development and Testing Electrochemical Methods for Treating Metal 
Salts, Cyanides and Organic Compounds in Waste Streams, Waste Management, (1998) Vol.18,  
[4] L. Janssen, L.Koene, The Role of Electrochemistry and Electrochemical Technology in 
Environmental Protection, Chemical Engineering Journal, (2002) Vol.85, 137-146. 
[5] R.Marković, S.Dragulović, V.Trujić, Deccoperization of Metallurgical Waste Water from 
Copper Minning and Smelting Complex Bor, European Metallurgical Conference EMC 2007, 
June, 11-14, Disseldorf, Germany, 403-416 
[6] T.Marsden, and J.Jickling, The Next Generation of Permanent Cathode and Lead Anode 
Technology, Hydrometallurgy Conference 2009, The Southern African Institute of Mining and 
Metallurgy, 249-256. 
[7] Low on water – Official Register of the Republic of Serbia, 1989  
[8] J.Stevanović, S.Gojković, M.Obradović, A.Despić and V.Nakić, Hidrogen evolution at Zn-Ni 
alloys, Electrochim. Acta, 43 (1998) 705 -718. 
[9] V. Marinović, J. Stevanović, B. Jugović, M.Maksimović, Hydrogen evolution on Ni/WC 
composite coatings, J.Appl. Electrochem, 36 ( 2006) 1005-1009. 
[10] R. Marković, B. Friedrich, J. Stevanović, B. Jegdić, Electrochemical Behavior of Copper 
with Non-Standard Impurities Content, Journal of Engineering Annals, vol 7, issue 4, (2009) 47-
50. 
[11] R. Marković. B. Friedrich. J. Stajić–Trošić. B. Jordović. B. Jugović. M. Gvozdenović. J. 
Stevanović. "Behaviour of non-standard composition copper bearing anodes from the copper  
refining process". Journal of Hazardous Materials 182 (2010) 55–63 
[12] S. Kumari, A. Agrawal, D. Bagchi, V. Kumar, B. D. Pandey, ¨Synthesis of copper 
metal/salts from copper bleed solution of a copper plant¨, Mineral Processing & Extractive 
Metall. Rev., 27: 159–175, 2006 
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Decopperization process of waste solutions from conventional copper electrolysis

Jonović, Radojka

TechnoRep

Slovak Society of Chemical EngineeringInstitute of Chemical and Environmental EngineeringSlovak University of Technology in BratislavaPROCEEDINGS39th International Conference of Slovak Society of Chemical EngineeringHotel HutníkTatranské Matliare, SlovakiaMay 21–25, 2012Editor: prof. J. MarkošISBN: 978-80-89475-04-9, EAN: 9788089475049Markovic, R., Stevanovic, J., Gvozdenovic, M., Jugovic, B., Jonovic, R.: Decopperization process of wastesolutions from conventional copper electrolysis, Editor: Markoš, J., In Proceedings of the 39th Interna-tional Conference of Slovak Society of Chemical Engineering, Tatranské Matliare, Slovakia, 292–297,2012.DECOPPERIZATION PROCESS OF WASTE SOLUTIONS FROM CONVENTIONAL COPPER ELECTROLYSIS  R. Marković1, J. Stevanović2, M. Gvozdenović3, B. Jugović4, R.Jonović1  1MMI, Mining and Metallurgy Institute Bor, 19210 Bor, Serbia 2ICTM, Institute of Electrochemistry, University of Belgrade, 11000 Belgrade, Serbia 3Faculty of Technology and Metallurgy, University of Belgrade, 11000 Belgrade, Serbia 4ITS-Serbian Academy of Science and Arts, 11000 Belgrade, Serbia   Key words: decopperization, mother liquor, waste solution, sludge  ABSTRACT  This paper is adresses on treatment of sulphuric acid waste solutions obtained during the conventional copper metallurgical activities. Mother liquor is a part of this solutions and it is generated during the regeneration process of copper bleed solution.  Copper, nickel and sulphuric acid are the main components and the other registered impurities are: As, Se, Fe, Sb, Zn, Bi, Pb, Cl ions. Aim to copper removing from the mother liquor, the decopperization process on the industrial scale equipment, is investigated. Investigation was done using the rectangular insoluble lead anodes alloyed with 6 wt.% of antimony at current value of 13 000 A,  identical to the current in a commercial copper refinery plant. A few parameters as so as: current, cell voltage, electrolyte temperature, electrolyte flow rate, level of electrolyte, were monitored during the test. Comparing the values of copper content in the solution before and after the decopperization of copper, it was found that it decreased of about 80 wt. % of the initial value. Chemical characterization of the sludge obtained on cathode has shown that it is a material with copper content of about 90 wt. %..   1. INTRODUCTION Practically, all human societies depend on the availability and possibility to use the various natural resources. Extraction of copper minerals that is primarily based on mining and metallurgy, in order to obtain the basic and precious metal has a long history in the territory of Western Balkan (1). Also, the fact that thanks to the quantities of confirmed mining reserves of 700 million tons, as so as the reserves of Au and other precious metals, the mining and metallurgical activities at this site could be expected in the future. A series of copper mining and metallurgical activities begins with mining of copper bearing ore and ends with the production of cathode copper, causes the serious environmental pollutions in this area such as contamination of soil, groundwater and local waterways, the Danube River, air.  Mother liquor is a part of the waste solution from the conventional copper electrolysis that is generated during the regeneration process of copper bleed solutions. Copper concentration limit in the mother liquor was in range of values from 9 to 22 g dm-3 and H2SO4 in range from 323 to 489 g dm-3.  The main problem related to the processing of waste solution is to find the appropriate technology that will be applied before the release of solutions in local waterways. In recent years, the alternative to chemical precipitation process is the electrochemical and 39th International Conference of SSCHEMay 21–25, 2012, Tatranské Matliare, Slovakia Po-Tu-4, 201.pdf292hydrometallurgical processes. Electrochemical processes of metal removal from waste solutions are the special interest of researchers in the last decade [2-4]. In this work, the mother liquor generated during the regeneration process of copper bleed solutions obtained in the conventional process of copper electrolysis are electrochemically treated using the insoluble anodes. Alloying plates of lead with antimony was used as insoluble anode aimed to increase the hardness of alloy, reduce corrosion, improve conductivity and reduce the anodic polarization, a preventive effect on preventing the formation of PbO [5,6].  2. EXPERIMENTAL PART  2.1.1 Equipment parts  Electrolytic copper decopperization from mother liquor was carried out on the industrial scale plant, located in conventional Tank House, whose parts are: a) Collecting tank - working volume is 8 m3 b) Electrolytic cell –the number of cells is 4 pieces in two groups and the cell volume with the electrodes is ∼ 15 m3 c) Commercial tank - the working volume is about 24 m3 d) Head tank - working volume is about 0.5 m3  e) Chemical pump - capacity is 45 m3/h,  f) Plate heat exchanger  g) Piping system  g) Sludge tank - the maximum working capacity is about 3.83 m3 and the minimum is approximately 0.34 m3.  2.1.2. Technological procedure  After the electrodes, cathode sheet from the cathode copper and rolled lead sheet with 6 wt. % Sb as anode, were put in the cells, interracial electrode distance of 100 mm was controlled. Rakes and cranes in the Tank House are used to put in the insoluble anodes in the cells, cell voltage was measured before the cells were connecting with current source with working current of 13000 A and determined the chemical composition of the solution. Mother liquor is transported from collecting tank into commercial tank, by gravitational pipeline system. Supplying of the cells with the solution is above, using pump and distribution systems, and the overrun of solution from the cell was over the overflow box. The circulation of solution was ~ 2.5 cell volume changes per hour. After circulation system stabilization, the cells have been included in the electrical circuit. The technological parameters are controlled during decopperization process, the solution working temperature was 55-60 oC, and calculated value for process duration was 400 min. Plate heat exchanger was used for solution heating and piping system was used for mother liquid transport from the collection tank to the commercial tank.  Solution volume that was transported is regulated by automatic valve. Decopperized solution is discharged from the cell by opening the electrolyte plug, located at the suitable height from the cell bottom and using return pipeline transported into the commercial tank. Pulp of copper sludge is discharged by opening the slime plug, located on the cell bottom and with pipeline for slime, transported into sludge tank. Analysis of copper and sulfuric acid was performed each hour. The process was stopped at the moment of occurrence the toxic gas - AsH3, by interrupting the circuit. The working volume 39th International Conference of SSCHEMay 21–25, 2012, Tatranské Matliare, Slovakia Po-Tu-4, 201.pdf293solution of ∼ 24 m3 was circulated for about thirty minutes aim to unification the composition and sampling for chemical analysis. Toxic emissions that occur during the process are high. During the process, the appearance of arsine (AsH3) was qualitatively examined by 5 % solution of mercuric chloride. Volume of solution was not corrected during the process but only at the end. The water evaporation from the cell surface was about 2 kg m -2h-1.  Table 1. Technological parameters of mother liquor decopperization process Working process characteristics First cells group, Ia/b cell Second cells group, IIa/b cell Cathode number  34 pcs. Cathode number,  31 pcs. Total cathode surface 53.2 m2 Total cathode surface 48.5 m2 Cathode current density 244.36 A m-2 Cathode current density 268.04 A m-2 Anode surface for 35 pcs. 47.88  m2 Anode surface for 32 pcs. 42.41 m2 Cell volume with electrodes 3.85 m3 Cell volume with electrodes 3.86 m3 Measurement during the decopperization process First cells group, Ia/b cell Second cells group, IIa/b cell Average cell voltage, I a cell 2.53 V Average cell voltage, II a cell 2.66 V Average cell voltage, I b cell 2.6 V Average cell voltage, II b cell 2.63 V Average solution temperature  58 oC Average solution temperature  58.5 oC  3. RESULTS AND DISCUSSION  3.1. Electrolytic decopperization of mother liquor  The waste solutions that were collected at the facility for the regeneration of copper electrolyte are:  -  water generated in places where the industrial water uses (water pump seal, vacuum pumps refrigeration, washing floors, washing unit, filter washing, overflow of cooling tower) - water obtained during  evaporation – acid condensate  - waste copper electrolyte – mother liquor Waste copper electrolyte – mother liquor, that remains after the copper sulfate production, is the only from the waste solution with a certain amount of copper, sulfuric acid, and harmful and hazardous substances so that these solutions have to previously purified to quality limits corresponding to the current legislation prior to discharge into the local waterways [7]. Copper concentration limit in the mother liquor was in range of values from 9 to 22 g dm-3 and H2SO4 in range from 323 to 489 g dm-3. Solution density at the beginning of the process is 1.28 g cm-3. Results of chemical characterization of mother liquor before and after decopperization process are present in Table 2. The results present the average composition of the solution followed by a period of 5 years.  Table 2. Chemical characterization of mother liquor before and after decopperization process Components Concentration initial, g dm-3 final,  g dm-3 Cu 13.14 2.68 H2SO4 432.36 440.09 Ni 3.07 3.36 39th International Conference of SSCHEMay 21–25, 2012, Tatranské Matliare, Slovakia Po-Tu-4, 201.pdf294Fe 0.82 0.65 As 0.8 0.56 Cl- 0.053 0.084 Zn 0.049 0.044 Sb 0.04 0.039 Te 0.029 0.018 Sn 0.009 0.009 Bi 0.0085 0.0022 Pb 0.0012 0.0012 Se 0.002 0.001  Electrolysis of copper using insoluble anodes could be described as the deposition of copper from the copper electrolyte due to the direct current passage.  During the decopperization process, the following reactions take place on the electrodes:  Cathode: Cu2+ + SO42-+2e = Cu + SO42-       (1)  Anode: 2OH-= ½ O2 + 2H+ + 2e        (2) During the process, oxygen is separated at the anode and the excess hydrogen ions remain in the solution and react with sulfate ions that in the anode space come with the help of direct current, with result in the generation of sulfuric acid. This means, that the separation of each equivalent of copper deposited on the cathode, creating the equivalent of sulfuric acid and releases the equivalent of oxygen at the anode, due to the reaction:  (Cu2+ + SO42-) + H2O = Cuo + 2H++ SO42- + ½ O2      (3)  Table 3. Measurements after mother liquor decopperization process Duration of experiment, h 6.66 Deposit character Cathode sheet is covered with black slime, which is removable Cu content in copper sludge, wt. % 91.17 Solution density, g cm-3 1.27 Cathode current efficiency based on the analysis of electrolytes, % ∼ 60 Consumption of ampere hours, Ah 346320 The specific power consumption, kWh/tCu 3513  During the decopperization with insoluble anodes (Pb +6 wt. % Sb), copper concentration is constantly decreasing, and H2SO4 increases. Copper is deposited to the cathode sheet, all the time in the area of limiting diffusion current deposition. According to this fact, cathode deposit is in a powder form with a possibility of self shaking. Parallel with the reaction of copper deposition, the copper concentration in the working solution decreases and the reaction of hydrogen evolution is carried out [8,9,10,11]. Arsenic from the electrolyte in the presence of hydrogen chemically reacts to form toxic gas arsine (AsH3). Achieved effects of treatment the mother liquor using insoluble anodes are: reducing of copper concentration is up to level of nickel concentration (12) and production of cathode powder deposit that falls from the cathode surface during the decopperization process on the bottom of the cells.  39th International Conference of SSCHEMay 21–25, 2012, Tatranské Matliare, Slovakia Po-Tu-4, 201.pdf295Physical and chemical characterization of the obtained cathode deposit- sludge is shown in Table 4.  Table 4. Chemical and physical characterization of cathode deposit –sludge Chemical characterization Physical characterization Element Content, wt. % Particle size, µm Wt. % Cu 91.17 +250 13.64 Pb 0.31 - 250+75 50.24 As 0.18 - 75+45 16.4 Se 0.15 - 45 18.6 Sb 0.075   Si 0.031   Fe 0.019   Te 0.014 Apparent density, g cm-3 2.46  The results of X-ray analysis showed that the elemental copper and cuprites are present in the sample of copper sludge sample. Duration of decopperization process and limiting copper concentrations in solution were conditioned by the appearance of arsine (AsH3) at working area. Qualitatively, the presence of arsine was observed from the beginning of the process by reaction with a solution of HgCl2 and by analysis of solution on Cu and H2SO4 is controlled the decopperization degree of mother liquor. The decreasing of Cu concentration is resulted in increased hydrogen evolution at the cathode; arsine occurrence was the reason for the process interruption.  Based on data on the initial and final Cu concentration as well as solution working volume, was calculated the decopperization degree of the mother liquor which amounts to 80 wt. %. Calculation of the cathode current efficiency, which was based on differences of copper concentration in solution, provided the values of about 60 %. Analysis of copper sludge composition indicates a high copper content and low content of accompanying elements.    4. CONCLUSION  During the process of electrolytic decopperization the mother liquor, the copper sludge with copper content over 90 wt. % was obtained. Based on data on the initial and final Cu concentration, as well as solution working volume, was calculated the decopperization degree of the mother liquor which amounts to 80 wt. %. Calculation of the cathode current efficiency, which was based on differences of copper concentration in solution, provided the values of about 60 %. Copper sludge and decopperized solution could be used for further chemical treatment in the aim to copper and nickel salts production.  Acknowledgment This work is financially supported by the Ministry of Science, Republic of Serbia: “The Impact of Mining Waste from RTB Bor on the Pollution of Surrounding Waterways with the Proposal of Measures and Procedures for Reduction the Harmful Effects on The Environment”, No. TR 37001. 39th International Conference of SSCHEMay 21–25, 2012, Tatranské Matliare, Slovakia Po-Tu-4, 201.pdf296  5.REFERENCES [1] Mining and Environment in the Western Balkans, May 3, 2010; ENVSEC Initiative at CSD 18 in New York, ENVSEC, Editor: Christina Stuhlberger 2010., 43-51;  [2] K. Juttner, U. Galla, H. Schmieder, Electrochemical Approaches to the Environmental Problems in the Process Industry, Electrochemica Acta, (2000) Vol.45, 2575–2594. [3] J. Dziewonski, et al., Development and Testing Electrochemical Methods for Treating Metal Salts, Cyanides and Organic Compounds in Waste Streams, Waste Management, (1998) Vol.18,  [4] L. Janssen, L.Koene, The Role of Electrochemistry and Electrochemical Technology in Environmental Protection, Chemical Engineering Journal, (2002) Vol.85, 137-146. [5] R.Marković, S.Dragulović, V.Trujić, Deccoperization of Metallurgical Waste Water from Copper Minning and Smelting Complex Bor, European Metallurgical Conference EMC 2007, June, 11-14, Disseldorf, Germany, 403-416 [6] T.Marsden, and J.Jickling, The Next Generation of Permanent Cathode and Lead Anode Technology, Hydrometallurgy Conference 2009, The Southern African Institute of Mining and Metallurgy, 249-256. [7] Low on water – Official Register of the Republic of Serbia, 1989  [8] J.Stevanović, S.Gojković, M.Obradović, A.Despić and V.Nakić, Hidrogen evolution at Zn-Ni alloys, Electrochim. Acta, 43 (1998) 705 -718. [9] V. Marinović, J. Stevanović, B. Jugović, M.Maksimović, Hydrogen evolution on Ni/WC composite coatings, J.Appl. Electrochem, 36 ( 2006) 1005-1009. [10] R. Marković, B. Friedrich, J. Stevanović, B. Jegdić, Electrochemical Behavior of Copper with Non-Standard Impurities Content, Journal of Engineering Annals, vol 7, issue 4, (2009) 47-50. [11] R. Marković. B. Friedrich. J. Stajić–Trošić. B. Jordović. B. Jugović. M. Gvozdenović. J. Stevanović. "Behaviour of non-standard composition copper bearing anodes from the copper  refining process". Journal of Hazardous Materials 182 (2010) 55–63 [12] S. Kumari, A. Agrawal, D. Bagchi, V. Kumar, B. D. Pandey, ¨Synthesis of copper metal/salts from copper bleed solution of a copper plant¨, Mineral Processing & Extractive Metall. Rev., 27: 159–175, 2006 39th International Conference of SSCHEMay 21–25, 2012, Tatranské Matliare, Slovakia Po-Tu-4, 201.pdf297

English

Stevanović, Jasmina S.

Gvozdenović, Milica M.

Serbian Academy of Science and Arts Digital Archive (DAIS)

Slovak Society of Chemical EngineeringInstitute of Chemical and Environmental EngineeringSlovak University of Technology in BratislavaPROCEEDINGS39th International Conference of Slovak Society of Chemical EngineeringHotel HutníkTatranské Matliare, SlovakiaMay 21–25, 2012Editor: prof. J. MarkošISBN: 978-80-89475-04-9, EAN: 9788089475049Markovic, R., Stevanovic, J., Gvozdenovic, M., Jugovic, B., Jonovic, R.: Decopperization process of wastesolutions from conventional copper electrolysis, Editor: Markoš, J., In Proceedings of the 39th Interna-tional Conference of Slovak Society of Chemical Engineering, Tatranské Matliare, Slovakia, 292–297,2012.DECOPPERIZATION PROCESS OF WASTE SOLUTIONS FROM CONVENTIONAL COPPER ELECTROLYSIS  R. Marković1, J. Stevanović2, M. Gvozdenović3, B. Jugović4, R.Jonović1  1MMI, Mining and Metallurgy Institute Bor, 19210 Bor, Serbia 2ICTM, Institute of Electrochemistry, University of Belgrade, 11000 Belgrade, Serbia 3Faculty of Technology and Metallurgy, University of Belgrade, 11000 Belgrade, Serbia 4ITS-Serbian Academy of Science and Arts, 11000 Belgrade, Serbia   Key words: decopperization, mother liquor, waste solution, sludge  ABSTRACT  This paper is adresses on treatment of sulphuric acid waste solutions obtained during the conventional copper metallurgical activities. Mother liquor is a part of this solutions and it is generated during the regeneration process of copper bleed solution.  Copper, nickel and sulphuric acid are the main components and the other registered impurities are: As, Se, Fe, Sb, Zn, Bi, Pb, Cl ions. Aim to copper removing from the mother liquor, the decopperization process on the industrial scale equipment, is investigated. Investigation was done using the rectangular insoluble lead anodes alloyed with 6 wt.% of antimony at current value of 13 000 A,  identical to the current in a commercial copper refinery plant. A few parameters as so as: current, cell voltage, electrolyte temperature, electrolyte flow rate, level of electrolyte, were monitored during the test. Comparing the values of copper content in the solution before and after the decopperization of copper, it was found that it decreased of about 80 wt. % of the initial value. Chemical characterization of the sludge obtained on cathode has shown that it is a material with copper content of about 90 wt. %..   1. INTRODUCTION Practically, all human societies depend on the availability and possibility to use the various natural resources. Extraction of copper minerals that is primarily based on mining and metallurgy, in order to obtain the basic and precious metal has a long history in the territory of Western Balkan (1). Also, the fact that thanks to the quantities of confirmed mining reserves of 700 million tons, as so as the reserves of Au and other precious metals, the mining and metallurgical activities at this site could be expected in the future. A series of copper mining and metallurgical activities begins with mining of copper bearing ore and ends with the production of cathode copper, causes the serious environmental pollutions in this area such as contamination of soil, groundwater and local waterways, the Danube River, air.  Mother liquor is a part of the waste solution from the conventional copper electrolysis that is generated during the regeneration process of copper bleed solutions. Copper concentration limit in the mother liquor was in range of values from 9 to 22 g dm-3 and H2SO4 in range from 323 to 489 g dm-3.  The main problem related to the processing of waste solution is to find the appropriate technology that will be applied before the release of solutions in local waterways. In recent years, the alternative to chemical precipitation process is the electrochemical and 39th International Conference of SSCHEMay 21–25, 2012, Tatranske´ Matliare, Slovakia Po-Tu-4, 201.pdf292hydrometallurgical processes. Electrochemical processes of metal removal from waste solutions are the special interest of researchers in the last decade [2-4]. In this work, the mother liquor generated during the regeneration process of copper bleed solutions obtained in the conventional process of copper electrolysis are electrochemically treated using the insoluble anodes. Alloying plates of lead with antimony was used as insoluble anode aimed to increase the hardness of alloy, reduce corrosion, improve conductivity and reduce the anodic polarization, a preventive effect on preventing the formation of PbO [5,6].  2. EXPERIMENTAL PART  2.1.1 Equipment parts  Electrolytic copper decopperization from mother liquor was carried out on the industrial scale plant, located in conventional Tank House, whose parts are: a) Collecting tank - working volume is 8 m3 b) Electrolytic cell –the number of cells is 4 pieces in two groups and the cell volume with the electrodes is ∼ 15 m3 c) Commercial tank - the working volume is about 24 m3 d) Head tank - working volume is about 0.5 m3  e) Chemical pump - capacity is 45 m3/h,  f) Plate heat exchanger  g) Piping system  g) Sludge tank - the maximum working capacity is about 3.83 m3 and the minimum is approximately 0.34 m3.  2.1.2. Technological procedure  After the electrodes, cathode sheet from the cathode copper and rolled lead sheet with 6 wt. % Sb as anode, were put in the cells, interracial electrode distance of 100 mm was controlled. Rakes and cranes in the Tank House are used to put in the insoluble anodes in the cells, cell voltage was measured before the cells were connecting with current source with working current of 13000 A and determined the chemical composition of the solution. Mother liquor is transported from collecting tank into commercial tank, by gravitational pipeline system. Supplying of the cells with the solution is above, using pump and distribution systems, and the overrun of solution from the cell was over the overflow box. The circulation of solution was ~ 2.5 cell volume changes per hour. After circulation system stabilization, the cells have been included in the electrical circuit. The technological parameters are controlled during decopperization process, the solution working temperature was 55-60 oC, and calculated value for process duration was 400 min. Plate heat exchanger was used for solution heating and piping system was used for mother liquid transport from the collection tank to the commercial tank.  Solution volume that was transported is regulated by automatic valve. Decopperized solution is discharged from the cell by opening the electrolyte plug, located at the suitable height from the cell bottom and using return pipeline transported into the commercial tank. Pulp of copper sludge is discharged by opening the slime plug, located on the cell bottom and with pipeline for slime, transported into sludge tank. Analysis of copper and sulfuric acid was performed each hour. The process was stopped at the moment of occurrence the toxic gas - AsH3, by interrupting the circuit. The working volume 39th International Conference of SSCHEMay 21–25, 2012, Tatranske´ Matliare, Slovakia Po-Tu-4, 201.pdf293solution of ∼ 24 m3 was circulated for about thirty minutes aim to unification the composition and sampling for chemical analysis. Toxic emissions that occur during the process are high. During the process, the appearance of arsine (AsH3) was qualitatively examined by 5 % solution of mercuric chloride. Volume of solution was not corrected during the process but only at the end. The water evaporation from the cell surface was about 2 kg m -2h-1.  Table 1. Technological parameters of mother liquor decopperization process Working process characteristics First cells group, Ia/b cell Second cells group, IIa/b cell Cathode number  34 pcs. Cathode number,  31 pcs. Total cathode surface 53.2 m2 Total cathode surface 48.5 m2 Cathode current density 244.36 A m-2 Cathode current density 268.04 A m-2 Anode surface for 35 pcs. 47.88  m2 Anode surface for 32 pcs. 42.41 m2 Cell volume with electrodes 3.85 m3 Cell volume with electrodes 3.86 m3 Measurement during the decopperization process First cells group, Ia/b cell Second cells group, IIa/b cell Average cell voltage, I a cell 2.53 V Average cell voltage, II a cell 2.66 V Average cell voltage, I b cell 2.6 V Average cell voltage, II b cell 2.63 V Average solution temperature  58 oC Average solution temperature  58.5 oC  3. RESULTS AND DISCUSSION  3.1. Electrolytic decopperization of mother liquor  The waste solutions that were collected at the facility for the regeneration of copper electrolyte are:  -  water generated in places where the industrial water uses (water pump seal, vacuum pumps refrigeration, washing floors, washing unit, filter washing, overflow of cooling tower) - water obtained during  evaporation – acid condensate  - waste copper electrolyte – mother liquor Waste copper electrolyte – mother liquor, that remains after the copper sulfate production, is the only from the waste solution with a certain amount of copper, sulfuric acid, and harmful and hazardous substances so that these solutions have to previously purified to quality limits corresponding to the current legislation prior to discharge into the local waterways [7]. Copper concentration limit in the mother liquor was in range of values from 9 to 22 g dm-3 and H2SO4 in range from 323 to 489 g dm-3. Solution density at the beginning of the process is 1.28 g cm-3. Results of chemical characterization of mother liquor before and after decopperization process are present in Table 2. The results present the average composition of the solution followed by a period of 5 years.  Table 2. Chemical characterization of mother liquor before and after decopperization process Components Concentration initial, g dm-3 final,  g dm-3 Cu 13.14 2.68 H2SO4 432.36 440.09 Ni 3.07 3.36 39th International Conference of SSCHEMay 21–25, 2012, Tatranske´ Matliare, Slovakia Po-Tu-4, 201.pdf294Fe 0.82 0.65 As 0.8 0.56 Cl- 0.053 0.084 Zn 0.049 0.044 Sb 0.04 0.039 Te 0.029 0.018 Sn 0.009 0.009 Bi 0.0085 0.0022 Pb 0.0012 0.0012 Se 0.002 0.001  Electrolysis of copper using insoluble anodes could be described as the deposition of copper from the copper electrolyte due to the direct current passage.  During the decopperization process, the following reactions take place on the electrodes:  Cathode: Cu2+ + SO42-+2e = Cu + SO42-       (1)  Anode: 2OH-= ½ O2 + 2H+ + 2e        (2) During the process, oxygen is separated at the anode and the excess hydrogen ions remain in the solution and react with sulfate ions that in the anode space come with the help of direct current, with result in the generation of sulfuric acid. This means, that the separation of each equivalent of copper deposited on the cathode, creating the equivalent of sulfuric acid and releases the equivalent of oxygen at the anode, due to the reaction:  (Cu2+ + SO42-) + H2O = Cuo + 2H++ SO42- + ½ O2      (3)  Table 3. Measurements after mother liquor decopperization process Duration of experiment, h 6.66 Deposit character Cathode sheet is covered with black slime, which is removable Cu content in copper sludge, wt. % 91.17 Solution density, g cm-3 1.27 Cathode current efficiency based on the analysis of electrolytes, % ∼ 60 Consumption of ampere hours, Ah 346320 The specific power consumption, kWh/tCu 3513  During the decopperization with insoluble anodes (Pb +6 wt. % Sb), copper concentration is constantly decreasing, and H2SO4 increases. Copper is deposited to the cathode sheet, all the time in the area of limiting diffusion current deposition. According to this fact, cathode deposit is in a powder form with a possibility of self shaking. Parallel with the reaction of copper deposition, the copper concentration in the working solution decreases and the reaction of hydrogen evolution is carried out [8,9,10,11]. Arsenic from the electrolyte in the presence of hydrogen chemically reacts to form toxic gas arsine (AsH3). Achieved effects of treatment the mother liquor using insoluble anodes are: reducing of copper concentration is up to level of nickel concentration (12) and production of cathode powder deposit that falls from the cathode surface during the decopperization process on the bottom of the cells.  39th International Conference of SSCHEMay 21–25, 2012, Tatranske´ Matliare, Slovakia Po-Tu-4, 201.pdf295Physical and chemical characterization of the obtained cathode deposit- sludge is shown in Table 4.  Table 4. Chemical and physical characterization of cathode deposit –sludge Chemical characterization Physical characterization Element Content, wt. % Particle size, µm Wt. % Cu 91.17 +250 13.64 Pb 0.31 - 250+75 50.24 As 0.18 - 75+45 16.4 Se 0.15 - 45 18.6 Sb 0.075   Si 0.031   Fe 0.019   Te 0.014 Apparent density, g cm-3 2.46  The results of X-ray analysis showed that the elemental copper and cuprites are present in the sample of copper sludge sample. Duration of decopperization process and limiting copper concentrations in solution were conditioned by the appearance of arsine (AsH3) at working area. Qualitatively, the presence of arsine was observed from the beginning of the process by reaction with a solution of HgCl2 and by analysis of solution on Cu and H2SO4 is controlled the decopperization degree of mother liquor. The decreasing of Cu concentration is resulted in increased hydrogen evolution at the cathode; arsine occurrence was the reason for the process interruption.  Based on data on the initial and final Cu concentration as well as solution working volume, was calculated the decopperization degree of the mother liquor which amounts to 80 wt. %. Calculation of the cathode current efficiency, which was based on differences of copper concentration in solution, provided the values of about 60 %. Analysis of copper sludge composition indicates a high copper content and low content of accompanying elements.    4. CONCLUSION  During the process of electrolytic decopperization the mother liquor, the copper sludge with copper content over 90 wt. % was obtained. Based on data on the initial and final Cu concentration, as well as solution working volume, was calculated the decopperization degree of the mother liquor which amounts to 80 wt. %. Calculation of the cathode current efficiency, which was based on differences of copper concentration in solution, provided the values of about 60 %. Copper sludge and decopperized solution could be used for further chemical treatment in the aim to copper and nickel salts production.  Acknowledgment This work is financially supported by the Ministry of Science, Republic of Serbia: “The Impact of Mining Waste from RTB Bor on the Pollution of Surrounding Waterways with the Proposal of Measures and Procedures for Reduction the Harmful Effects on The Environment”, No. TR 37001. 39th International Conference of SSCHEMay 21–25, 2012, Tatranske´ Matliare, Slovakia Po-Tu-4, 201.pdf296  5.REFERENCES [1] Mining and Environment in the Western Balkans, May 3, 2010; ENVSEC Initiative at CSD 18 in New York, ENVSEC, Editor: Christina Stuhlberger 2010., 43-51;  [2] K. Juttner, U. Galla, H. Schmieder, Electrochemical Approaches to the Environmental Problems in the Process Industry, Electrochemica Acta, (2000) Vol.45, 2575–2594. [3] J. Dziewonski, et al., Development and Testing Electrochemical Methods for Treating Metal Salts, Cyanides and Organic Compounds in Waste Streams, Waste Management, (1998) Vol.18,  [4] L. Janssen, L.Koene, The Role of Electrochemistry and Electrochemical Technology in Environmental Protection, Chemical Engineering Journal, (2002) Vol.85, 137-146. [5] R.Marković, S.Dragulović, V.Trujić, Deccoperization of Metallurgical Waste Water from Copper Minning and Smelting Complex Bor, European Metallurgical Conference EMC 2007, June, 11-14, Disseldorf, Germany, 403-416 [6] T.Marsden, and J.Jickling, The Next Generation of Permanent Cathode and Lead Anode Technology, Hydrometallurgy Conference 2009, The Southern African Institute of Mining and Metallurgy, 249-256. [7] Low on water – Official Register of the Republic of Serbia, 1989  [8] J.Stevanović, S.Gojković, M.Obradović, A.Despić and V.Nakić, Hidrogen evolution at Zn-Ni alloys, Electrochim. Acta, 43 (1998) 705 -718. [9] V. Marinović, J. Stevanović, B. Jugović, M.Maksimović, Hydrogen evolution on Ni/WC composite coatings, J.Appl. Electrochem, 36 ( 2006) 1005-1009. [10] R. Marković, B. Friedrich, J. Stevanović, B. Jegdić, Electrochemical Behavior of Copper with Non-Standard Impurities Content, Journal of Engineering Annals, vol 7, issue 4, (2009) 47-50. [11] R. Marković. B. Friedrich. J. Stajić–Trošić. B. Jordović. B. Jugović. M. Gvozdenović. J. Stevanović. "Behaviour of non-standard composition copper bearing anodes from the copper  refining process". Journal of Hazardous Materials 182 (2010) 55–63 [12] S. Kumari, A. Agrawal, D. Bagchi, V. Kumar, B. D. Pandey, ¨Synthesis of copper metal/salts from copper bleed solution of a copper plant¨, Mineral Processing & Extractive Metall. Rev., 27: 159–175, 2006 39th International Conference of SSCHEMay 21–25, 2012, Tatranske´ Matliare, Slovakia Po-Tu-4, 201.pdf297

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Decopperization process of waste solutions from conventional copper electrolysis

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