A process for treating very dilute solutions containing ecologically noxious heavy metal ions, in which the solutions are made acceptable for return to the environment, and the typically valuable heavy metal present in the solution is recovered at an economic profit. The dilute solution is flowed through an ion exchange resin, as a cross-linked polystyrene having quaternary ammonium functional groups which hold the heavy metal ions, allowing an ecologically benign effluent to return to the environment or the water to be re-used in industrial processing. Typically, an alkali metal halide is subsequently placed in contact with the resin to recover the heavy metal ion for subsequent reduction to a solid.