Selective recovery of copper, nickel and zinc from ashes produced from Saccharomyces cerevisiae contaminated biomass used in the treatment of real electroplating effluents

The aim of this work was to seek an environmentally friendly process for recycling metals from biomass-sludges generated in the treatment of industrial wastewaters. This work proposes a hybrid process for selective recovery of copper, nickel and zinc from contaminated biomass of Saccharomyces cerevisiae, used in the bioremediation of electroplating effluents. The developed separation scheme comprised five consecutive steps: (1) incineration of the contaminated biomass; (2) microwave acid (HCl) digestion of the ashes; (3) recovery of copper from the acid solution by electrolysis at controlled potential; (4) recycle of nickel, as nickel hydroxide, by alcalinization of the previous solution at pH 14; (5) recovery of zinc, as zinc hydroxide, by adjusting the pH of the previous solution at 10. This integrated approach allowed recovering each metal with high yielder (>99% for all metals) and purity (99.9%, 92% and 99.4% for copper, nickel and zinc, respectively). The purity of the metals recovered allows selling them in the market or being recycled in the electroplating process without waste generation.