Mechanism of Precipitate Removal of Antimony and Bismuth Impurities from Copper Electrolyte by Arsenic

Abstract

This paper investigates the mechanism of removal of Sb and Bi from copper electrolyte under the function of arsenic. The precipitation reactions were carried out from a synthetic electrolyte containing 185g/L sulfuric acid and 45g/LCu2+ in the presence of As (III, V), Sb(III, V) and Bi(III) under the temperature 65°C and stirring rate of 300r/min. The structure, morphology and component of the precipitate were clarified by methods of chemical analysis, SEM, XRD, TEM, EDAX and IR spectroscopy. A kind of white precipitate has irregular shape and mainly consists of As, Sb, Bi and O elements forms in this electrolyte. The characteristic bands in the IR spectra of the precipitate are O-H, As-OH, As-O-Sb, Sb-OY (Y=As, Sb, Bi), and O-As-O. The precipitate is a mixture of microcrystalline of (Sb,As)2O3, BiSb2O7, SbAsO4 and amorphous phases by XRD and electronic diffraction. The removal rate of Sb and Bi reaches 43% and 64%, respectively from copper electrolytes by a 4g/L arsenic solution owing to these precipitate.

Copper Refining Electrolyte and Slime Processing - Emerging Techniques

“…In order to control the purity of deposited cathode copper during refining, the solution is discarded as copper bleed stream (CBS) which contains high level of Cu(II) >40 g/l, Ni(II) > 15 g/l and H2SO4 > 200 g/l along with other impurities viz, Fe, As, Sb, Bi, etc. However, the volume of the bleed vary with the operational conditions and refineries [25,59,113,133] viz., 1% anode impurities/10% bleed/month. Various methods are employed to recover the valuable metals depending on the composition of the CBS.…”

“…However, during Cu-ER, while As dissolves extensively in the electrolyte at 2-22 g/l and <4% precipitates as As-Sb and As-Sb-Bi oxides in addition to (Cu,Sn,Sb,Bi)AsO4, Pb5(AsO4)3(OH,Cl) and an oxidate phase mainly Cu-Ag-As-S-O [7]. The Sb and Bi impurities are partly report to the anode slime (favoured by Pb, As, Se, Te which need to be recycled [6]) and the rest dissolved along with Cu(II) from the anode in the electrolyte and gradually accumulate in the Cu-ER electrolyte, which results in a variety of intolerable problems, such as anode passivation, cathodes contamination and floating slime formation [2,[6][7]18,20,[25][26][130][131][132][133]. High level of As in the electrolyte precipitate Sb and Bi impurities as As-Sb-Bi oxide and (Sb,Bi)AsO4 [6,7,18,27,117,134].…”

“…High level of As in the electrolyte precipitate Sb and Bi impurities as As-Sb-Bi oxide and (Sb,Bi)AsO4 [6,7,18,27,117,134]. Therefore, the removal of As, Sb and Bi impurities has become a key problem faced by copper smelting-refining plants in the world [6,10,133].…”

“…These ionic and neutral species easily interact with each other to form arsenate, antimonate and other insoluble compounds forming solid solutions either autogeneously or rapidly by homogeneous reactions, native seed addition, or heterogeneous surfaces [6,14,136,[139][140][141][142]. The floating slimes [117] are formed away from the anode as solid solutions of (Sb,Bi)AsO4 (0.35-1.34 g2/l2 at 65oC [143]), (As,Bi)SbO4.xH2O [6,74,[130][131][132][133] and/or Sb(OH)2.Sb(OH)6 which need control [117].…”

“…Homogeneous Precipitation: A part of the As(III,V), Sb(III,V) and Bi(III) impurities can spontaneously precipitate from the electrolyte to the anode mud (slimes, sludge or residue) during Cu-ER [25][26][27]117,[130][131][132][133][134][202][203][204]. Meanwhile, hydrometallurgical electrolytes purification technologies based hetero-geneous precipitation reactions with M(II) [18] (viz., Ba, Sr, Sn, Pb [27]) and homo-geneous co-precipitation reactions among As(III,V), Sb(III,V) and Bi(III) impurities in the bath have been utilized in the copper smelting industry [21,[25][26][27]117,134,136], however, until now the purification mechanisms have not been fully understood [130][131][132][133]. The slow arsenate and/or antimonate formed from As(V) and/or Sb(V), Q(III) (Q = As, Sb and Bi) are the main reasons of Sb(III,V) and Bi(III) removal by As(III,V) [27,74,117,134] and Sb(III,V).…”