GB1327525A - Elimination of floating slime during electrolytic refining of copper - Google Patents

Abstract

1327525 Electro-refining copper BOLIDEN AB 25 May 1971 [28 May 1970 (3)] 16913/71 Heading C7B Cu anodes containing more than 200g/ton of Sb and/or more than 100g/ton of Bi are electrorefined in an electrolyte in which the quantities of trivalent As, pentavalent As and pentavalent Sb are regulated so that in the steady state the contents of As (III) and As (V) exceed 1 and 2g/l respectively and the quantity of Sb (V) is less than 0À05g/l, to eliminate floating slime during electro-deposition of cathode Cu. The quantity of As (III) may be maintained by continually adding As 2 O 3 e. g. to a withdrawn part stream of electrolyte which is then recirculated, or by charging to the electrolyte in the form of As alloyed in the anodes. To regulate the ratio between As (III) and As (V), As (V) is reduced to As (III) by adding SO 2 gas to a withdrawn portion of the electrolyte which is then returned. The formation of floating slime and anode passivation may be both avoided by periodically reversing the current for periods of 1-15% of the total electrolysis period. The electrolyte may comprise an aqueous solution of 35-50g/l Cu (as CuSO 4 ) and 150-250 g/l H 2 SO 4 , with glue, a thiocarbamide and lignosulphonic acid. To prevent formation of Sb(V), the electrolyte may be covered with plastic bodies or cloth or oil. During electrolysis, crystalline Sb(OH) 2 AsO 4 and BiAsO 4 precipitate.