In this study, the design of experiments is used to study and model the time of passivation in copper electrorefining as a function of the charge of melting furnace through the preparation of copper casting anodes. As a result of optimization for the proposed optimized anodes, the charge percent values of concentrate (Co), refinery scrap (RS), and non-refinery scrap (NRS) were proposed equals to 69.1, 0.574 and 30.32 (wt.%), respectively. Experimental data confirmed the enhanced passivation time of the proposed anode was 6520 s. Also, it was observed that the molar ratio of As/(Bi+Sb) and Ag/(Se+Te) are the key factors in passivation time. Finally, the relation of passivation time (seconds) with the charge of melting furnace is proposed as : t (s)= -3728.98 × Co + 4640.00 × RS + 3141.00 × NRS + 17763.27 × Co × RS + 25547.65 × Co × NRS -1758.00 × RS × NRS. Moreover, adding of As ingot in casting anodes as a dose dependent of non-refinery scrap portion in the input charge of the melting unit can effectively prolong the time of passivation.
The cyanide process, as the most common approach in the recovery of gold by hydrometallurgical, suffers from its high toxicity to the environment. The effect of practical parameters, viz., temperature, time, concentration, mechanical activation, and the stirring rate, was investigated using a combination of H 2 O 2 , BmimHSO 4 , and thiourea as green solvent to recover the gold from anode copper slime in an electrorefining plant. The leaching kinetics of Au in the selected slime was also investigated. The results showed that leaching reaches 93.48% after 20 h in the activated sample for 10 h at the temperature of 313.15 K and solvent including 60% (v/v) BmimHSO 4 , 50 g/L thiourea, 1/15 g/ml pulp density, 25 g/L H 2 O 2 , and an agitation speed of 400 rpm. Moreover, the leaching of Au follows the shrinkage particle model, and the diffusion of a solvent through the leaching product was the administrated mechanism. The proposed green solvent can also dissolve gold effectively and is an excellent candidate to replace harmful cyanide-based solvents.
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