Catalytic effect of silver on arsenic-containing copper sulfide dissolution in acidic solution

Catalytic effects of silver on the dissolution of arsenic-containing copper sulfides such as enargite in acidic media were investigated. Leaching experiments showed that silver increased the enargite dissolution rate, and that the dissolution behavior was potential-dependent. The addition of silver ions and silver sulfide greatly enhanced enargite dissolution. Such behavior can be explained based on the following reaction model: enargite dissolution is enhanced by silver as the silver ions remove the hydrogen sulfide produced during enargite reduction, giving the more amenable copper sulfide. Thermodynamic calculations suggested that the addition of silver ions and controlling the potential would maintain a high enargite dissolution rate. Leaching experiments were therefore performed with the addition of silver sulfide and potential control using an automatic titration apparatus. Experimental results showed that a combination of these two factors gave high enargite dissolution; i.e., 75% copper was dissolved in 24 h at 0.750-0.850 V vs. the standard hydrogen electrode at 303 K.