Behaviour of anode impurities in copper electrorefining. Effect of bismuth, arsenic, antimony and oxygen in copper anode.

Abstract

The effect of anode bismuth level and of concentrations of dissolved oxygen and bismuth ions in copper electrolyte were investigated to understand the formation mechanism of anode slime layer and its influence toward passivation behaviour. The metallic granular forms of bismuth were found in the anode at the lower bismuth content. However, the higher bismuth content of anode exhibited a hairy or meshes-like shape. The bismuth dissolved preferentially during electrolysis and the anode surface after electrolysis became excessively uneven. The slimes were classified into the adhering and the falling types. The amount of falling slimes was about 90% of total slime formed and it mainly consisted of copper powder mechanically separated from anode. On the other hand, the adhering slimes consisted of copper powder, Bi2 03 and Bi2 (SO4)3. The copper powder in the adhering slimes was the fine particles formed by the disproportionation reaction of Cu+ ions. Bi2 (SO4)3 in the slimes were precipitated by the supersaturation of dissolved Bi 3+ ions and observed in the inside of grain boundary. Under the electrolytic condition of high current density and in the case of the addition of Bi3+ ions into electrolyte, layer of needle-like precipitates of Bi2 (SO4)3 was observed on the adhering slime. This slime layer caused the anode to passivate sensitively. When Bi, As and Sb impurities were coexisted in the copper anode, the composition of the resulting anode slime was Bi2 03 , BiAsO4 and SbAsO4.

Purification of Industrial Copper Electrolyte from Bismuth Impurity

“…Many refineries utilize anode doping and electrolyte additions. For example, arsenic is used in refineries as the primary control technique for Bi and Sb [1,[20][21][22]. There are several studies on using the various types of substances with an adsorbing effect on selected pollutants, including Bi.…”

Copper Refining Electrolyte and Slime Processing - Emerging Techniques

“…The various metallic (viz., Ag, Pb, Sn, Fe, Ni, Co, Zn, etc) and non-metallic (viz., O < 1%, S, As, Sb, Bi, Se, Te) impurities in the cast anodes are present as solid solutions in the copper metal matrix and/or as inclusions in the copper metal grain boundaries, however, the quantification of their association and carriers are difficult due to the anode mineralogical complexities being influenced by the variation of the feed and/or smelting to anode casting processes [32][33][34]43,[63][64][65]. While the inert or noble (Au, Ag, Pt, Pd, Sn, Pb, Ba, Se, Te) and most of partial or less soluble impurities (Cu, Ni, Co, As, Sb, Bi) settle as anode slime/sludge [30,32,[66][67][68][69][70][71], other soluble impurities, particularly the minor elements or group VA/15 (GVAEs or Q: As, Sb and Bi), VIA/16 as A2Z (A = Cu, Ag; Z: Se, Te) [61,69] and Mt (viz., Fe, Co, Ni, Zn) co-dissolved with Cu(II), build up in the copper refining electrolyte (CRE) which need monitoring [72,73] and control as far as possible to prevent the formation of suspended or floating slimes (viz., As, Sb, Bi) [11,[74][75][76][77], contamination of the cathodes [28,58,78] and passivation of the anodes (Ni, Pb, Sb, Bi) [20,23,24,79,80] before bleeding for spent CRE reprocessing [25,26,[81][82][83][84]. While th...…”

“…The reducing electrolyte conditions favour impurity control and slime formation (viz., Ag, Se, Te, Sb), but oxidizing conditions are unfavourable for Cu-ER and slime precipitation-settling viz., QAsO4 and QSbO4.xH2O. The anode slimes were classified into the minor adhering type (Sb(V), Bi2O3 and layer of needle-like precipitates of Bi2(SO4)3) which caused the anode to passivate sensitively and mostly the falling type (fine particles of Cu-powder due to Cu+ disproportionation, 1-dimentional Bi2O3, 2-dimentional/plate like BiAsO4 and SbAsO4) [80]. Both Sb(III) and Bi(III) partly remain undissolved and report to the anode slime (due to association with As, Pb and Sn or surface coating by Ag2Se1-xTex) and rest dissolve during Cu-ER, but extensively re-precipitate as As-Sb oxide, As-Sb-Bi oxide, (Sb,Bi)AsO4 [43] and (As,Bi)SbO4.…”