The influence of copper on the effect of certain surfactants during the cementation of cadmium by suspended zinc particles

Abstract

The influence of copper on the effect of nonylphenolpolyethylene glycol (D1), dinaphthylmethane-4,4′-disulphonic acid (D2) and polyethylene glycol with molecular weight 400 (D3) during cadmium–zinc dust cementation was investigated. The behaviour of D1, D2 and D3 was determined by comparing the results obtained with and without surfactant. It was found that in the presence of copper D1 improves, but D2 and D3 inhibit cadmium cementation. The presence of copper substantially changes the effect of D1 and D3 which becomes opposite to the effect of these surfactants in the absence of copper. The addition of copper has no effect on the influence of D2. SEM study of cementation products indicates a change of deposit structure in the presence of copper. The addition of copper causes the formation of coarser deposits. Morphology of cementation products changes from a completely compact layer in the presence of D1 to a porous layer in the presence of both copper and D1 which corresponds to the cementation kinetics results. The addition of copper enhances dendrite formation in the presence of D2 and contributes to the formation of clusters in the presence of D3. Dendrite formation in the presence of D2 probably increases hydrogen evolution which inhibits cadmium deposition. The addition of D1 to the zinc sulphate solution containing copper and cadmium increases co-deposition of these impurities during the cementation by suspended zinc particles.