Sustainable Mining and Metallurgy

The lead anode is obtained by the preliminary refining of crude lead by melting and removing copper by pyrometallurgical method. The electrolytic refining is carried out in the silicofluoric acid system to obtain the precipitated lead and the residual electrode. If the bismuth content in the lead electrolyte and the anode slime washing water is too high, the bismuth grade of the precipitated lead will be effected. In this paper, a method was proposed to remove Bi³⁺ by adding a certain amount of substance A (a sulfide) in the process of lead anode mudding, so that most of the Bi³⁺ in the washing water becomes sulfide and precipitates into the anode mud. The experimental results show that the concentration of Bi³⁺ in washing water can be reduced from 200mg/L to 18mg/L under the conditions of liquid solid ratio of 5∶1, slurrying temperature of 40℃, stirring time of 60min and substance A dosage of 0.5g/L, which will not affect the chemical composition of lead electrolyte, and the qualified rate of lead precipitation will be increased from 60% to 100%.