THE CAPE TECID,TIKOK

Due to equilibrium constraints and the relatively slow kinetics of the cyanidation of gold ores, calcium or potassium cyanide is added to the leaching stage in excess to that required theoretically. This, in many situations, result in large concentrations of free cyanide present in the effluent streams from gold plants. ill vie\y of the toxicity of cyanide and the fact Lhat cyanide is fatal in small dosages, authorities have been forced to tigl1ten up plant discharge regulations. Therefore, it is vital to remove cya..nide from industrial effluent, not only to meet standard requiremems, bm also to recover the cyanide as a means of reducing chemical costs. The aim of this study is to recover, rather than destroy, free cyanide from effluent streams Y~a a metal impregnated carbon-in-column configuration. The first part of the study focused on the mechanism of free cyanide recovery by metal impregnated carbon and the factors influencing the kinetics of the process in a batch reactor. The second part concentrates on the optimisation of such a process m a column configuration, 3...'1d subsequently to recover the cyanide from the carbon. carbon ror free cyanide removal both from a kinetic a.Tl.d equilibrium point of \'iew. Furthermore: the presence of other metal cyanides in solution V:iID free cyanide has a negligible effect on the performaIlce of the metal (silver) impregnated acti\'ated carbon to remo,;;e free cyanide. j\foreover, sca.'1ning electron lTlicrographs re\'ealed distinct differences in appeara..Tlce of metal impregnated carbons, \\'hich ultimately responds differently 10 the removal of free cya.njde