Electroflotation for groundwater decontamination

An electroflotation device was built using a platinum-clad columbium screen as anode, and a stainless steel screen as cathode. A rock salt solution was used as the electrolyte, generating hypochlorite to oxidize cyanide, and hydroxides to form metal hydroxide precipitates which were carried to the top of the electroflotation device by the rising gas bubbles. The device was used successfully to remove Ni, Zn, Pb, Cu/CN in a polluted groundwater obtained from directly under a contaminated site, meeting the pretreatment standards of the pollutants for the local POWT sewer system. The cost of an electroflotation device plus a sand filter compares favorably with a conventional treatment system using cyanide oxidation/alkaline precipitation/polymer-aided clarification. (C) 1997 Elsevier Science B.V.