Hydrometallurgical process for recovering precious metals from a

Details Hydrometallurgical process for recovering precious metals from a Hydrometallurgical process for recovering precious metals from a

1980-03-20

1981-10-06

Ozaki, G.

Specialized metallurgical processes, compositions for use therei

Processes

Electrothermic processes

75101BE, 75118R, 75118P, 75121, 423 24, 423 27, 423510, C22B 1104

Patent

active

042933323

ABSTRACT:
A hydrometallurgical process for recovering precious metals, such as gold, silver, selenium, and tellurium etc. from anode slime has been developed and tested successfully. The process comprises three major unit operations: leaching, liquid-liquid extraction, and reduction. The decopperized anode slime is first leached with nitric acid at an elevated temperature to obtain a leach solution containing at least about 95% by weight of the silver content, 96% by weight of the selenium content and 76% by weight of the tellurium content of the decopperized anode slime. Silver in the nitric acid leach solution is recovered in the form of silver chloride. Subsequent to the recovery of silver chloride, the selenium, tellurium, copper and other impurities-containing solution is denitrated and chlorinated by a liquid-liquid extraction technique. This selenium, tellurium, copper and other impurities-containing chloride solution is treated to separate tellurium from selenium, copper and other impurities by a liquid-liquid extraction technique. Selenium and tellurium are then recovered individually by passing sulfur dioxide through the selenium-containing and tellurium-containing solutions. The nitric acid leach residue is treated with aqua regia to leach gold and other impurities at an elevated temperature for a period of about 1 to 4 hours. The gold-containing solution is sent to separate gold from other impurities by a liquid-liquid extraction technique. Gold with a purity of greater than 99.9% is recovered by introducing a reducing agent to the gold-loaded organic extractant at an elevated temperature for a period of about 2 to 4 hours. This newly developed process is pollution-free, energy-saving, and economic to compare with conventional pyrometallurgical processes.

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