RECOVERY OF HEAVY METALS BY SELECTIVE PRECIPITATION

The present disclosure provides a process for selectively separating a first heavy metal such as copper from a liquid medium containing at least the first heavy metal in dissolved form, by: (a) contacting the liquid medium with a solid sulfide of a second heavy metal such as zinc, said sulfide of the second heavy metal having a solubility which is higher than the solubility of the sulfide of the first heavy metal, in a first reactor, to produce a precipitate of a sulfide of the first heavy metal and a solution containing second heavy metal; (b) separating the precipitate of the first heavy metal sulfide from the solution containing the second heavy metal; (c) contacting the solution of the second heavy metal with a source of sulfide produced by biological conversion of a sulfur compound, in a second reactor, to produce a precipitate of a sulfide of the second heavy metal and a treated solution; and (d) returning at least part of the precipitate of the sulfide of the second heavy metal to step (a). The first and second heavy metals may each be more than one and the biological conversion is especially carried out in the second reactor.