(60p) Heavy Metals Remediation Via Cyclic Electrowinning/Precipitation (CEP)

This paper describes a Cyclic Electrowinning/Precipitation (CEP) System, that has been developed for the removal heavy metals (e.g., Cu(II), Ni(II), Cd(II), Pb(II)) from aqueous waste streams or leachates originating from contaminated sources such as Brownfields or Superfund sites. The novelty of this automated system lies in its coupling of metal reduction by electrowinning with in-process precipitation/redissolution to produce a programmable cyclic process that can be matched to varying metal mixture compositions and concentrations. The precipitation/redissolution part of the process addresses two important issues: it (1) concentrates the metal ions in solution so that the electrowinning steps operate at high current efficiencies; and (2) reduces metal ion concentrations in the final effluent water to very low concentrations. In the current system a spouted particulate electrode (SPE) is used to circulate conductive particles that serve as cathode surfaces for metal reduction. This process removes and concentrates dilute metal ions onto the conductive particle surfaces, producing an extremely large volume reduction from the original wastewater. Although the main objective of the CEP system is remediation, the potential for recovery of single purified metals for recycling also exists. Specific experimental results concerning the performance of this system are presented.