The co-precipitation of copper and zinc with lead jarosite

Abstract

The formation of lead jarosite, Pb 0.5Fe 3(SO 4) 2(OH) 6, in the presence of dissolved copper and/or zinc results in a significant substitution of these metals in the jarosite phase; the co-precipitation is most pronounced in sulphate media but also occurs, to a lesser degree, in chloride solutions. The copper and/or zinc substitute for iron, and under extreme conditions the product approaches beaverite, Pb(Cu,Zn)Fe 2(SO 4) 2(OH) 6, in structure and composition. The extent of co-precipitation increases sharply with increasing concentrations of dissolved CuSO 4 or ZnSO 4 and slightly with either an increasing stoichiometric ratio of PbSO 4/Fe 3+ or increasing ionic strength. The co-precipitation of copper or zinc is not significantly affected by acid concentration although the yield of product declines with increasing concentration of H 2SO 4. The extent of reaction is relatively insensitive to reaction temperatures in the range 130–180°C and to reaction times in excess of 2 h. Copper is strongly co-precipitated in preference to zinc from solutions containing both metals. Other divalent base metals such as Co, Ni and Mn are also co-precipitated with lead jarosite although not to the same degree as copper or zinc.