Electroextraction of heavy metals from wastewater for the protection of natural water bodies from pollution
The most promising methods of eluates recycling are electrolysis and electrodialysis. It is possible to obtain metals and purified regeneration solutions for repeated regeneration in case of application of electrochemical methods. The processes of electrolysis of solutions of cadmium and zinc sulfat...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
PC Technology Center
2018-02-01
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| Series: | Eastern-European Journal of Enterprise Technologies |
| Subjects: | |
| Online Access: | http://journals.uran.ua/eejet/article/view/123929 |
| Summary: | The most promising methods of eluates recycling are electrolysis and electrodialysis. It is possible to obtain metals and purified regeneration solutions for repeated regeneration in case of application of electrochemical methods. The processes of electrolysis of solutions of cadmium and zinc sulfates and chlorides in electrolysers of different types were explored, the influence of conditions of electrolysis on effectiveness of extraction and separation of metals, obtaining inorganic acids for repeated usage in regeneration processes was determined.
Single- and double-chamber electrolysers, in which cathode was made of stainless steel and titanium anode was covered with ruthenium oxide, were used. Cathodic and anodic areas in double-chamber electrolysers were separated by the anion exchange membrane MA-41.
Solution of cadmium sulfate or of zinc sulfate was found in the cathodic chamber in double-chamber electrolysers. Solution of sulfuric acid with concentration of 50 mg-equiv./dm3 was in the anodic chamber.
It is recommended to carry out electrolysis for two hours when using a single-chamber electrolyser at a voltage of 5 V with the purpose of removing cadmium from sulfuric acid solution and reusing regeneration solution of sulfuric acid. Almost complete removal of cadmium ions and concentration of sulfuric acid in anolyte is achieved in case of using a double-chamber electrolyser. However, in terms of power saving, release of cadmium should be performed in single-chamber electrolysers.
However, it is recommended to perform zinc removal from eluates in double-chamber electrolysers. In this case, zinc ions are almost completely removed within four hours at voltage of 25 V. The maximum current efficiency is 42‒80 %.
Conditions of separation of zinc and cadmium in the eluate are associated with acidity of the solutions. A stage-by-stage removal of metals – cadmium followed by zinc, is observed during electrolysis of the mixture of cadmium and zinc chlorides in a single-chamber electrolyser. Current efficiency of metals is 30–68 %. In the case of electrolysis of a mixture of zinc and cadmium sulfates, only cadmium (В=100 %) is removed from the solution, while zinc ions completely remain in solution. Zinc is released only at the transfer of the electrolyte to a double-chamber electrolyser |
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| ISSN: | 1729-3774 1729-4061 |