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What are the methods and steps of crude silver electrorefining process?


       Silver electrolysis process belongs to redox reaction. At the same time, the positive silver ions in the solution are driven by the electric field and move to the cathode continuously. After reaching the cathode, the electrons are reduced to silver. Silver electrolysis is the whole process in which silver is converted from anode to ion and reduced to metal at cathode.
At present, most of the electrolyzers used in the large-scale silver electrorefining industry are crawler type horizontal electrolyzers, also known as ship type electrolyzers. The advantages of this type of trough are high degree of automation, continuous automatic silver powder production, no need to stop the trough, low labor intensity, suitable for large-scale production. However, the current density of this kind of electrolyzer is relatively small (generally 250-350a / m2), the electrolysis speed is relatively low, the electrolyte occupied in the equipment is relatively large, and the capital occupied is large and the turnover is slow.
        In addition, in the severe situation of national environmental protection, the waste gas treatment in the process needs to be reasonable and perfect. In the production of gold and silver extracted from gold mud, it is usually through several steps, such as removing impurities by nitric acid, dissolving gold in aqua regia, reducing sodium sulfite and so on. However, in the above process, a large number of yellow smoke (flue gas containing nitrogen oxides) and other acidic flue gas (HCl / SO2) will be produced, which is not only harmful to the environment Environmental pollution, but also carries a serious loss of precious metals. In recent years, with the enhancement of people’s awareness of environmental protection and under the supervision of environmental law enforcement units, how to make the acid gas discharge up to the standard is a difficult problem for the production units.
        The silver electrolytic refining process specifically includes the following steps:
(1) Preparation of silver nitrate solution: put silver material into enamel reactor to react with nitric acid, filter, and vacuum filter, and pump silver nitrate solution to silver nitrate high storage tank for standby;
(2) Silver precipitation reaction: slowly add flake alkali into the filtered silver nitrate solution in step (1), stop when the internal pH value of the reaction system reaches 14, continue to stir for 18-22min, vacuum filter, and pump the filtrate into the waste liquid storage tank;
(3) Preparing silver electrolyte: adding the silver hydroxide obtained in step (2) into the electrolyte purification reactor, adding waste electrolyte into the purification reactor until the pH of the system is 5-6, filtering, and adding appropriate amount of pure water and nitric acid into the filtrate to obtain silver electrolyte;
(4) Silver electrolytic refining: hang the anode plate and cathode plate on the anode and cathode respectively, and then put them into the silver electrolyte prepared in the step for electrolysis for 18-22h to get silver powder. Test and wash the silver powder to neutral, then dry it, and send it to the ingot workshop for ingot casting and label printing.

 


Post time: Apr-14-2021