Thermal plasma in-flight treatment of electroplating sludge

The thermal plasma inflight processing of electroplating sludge was investigated. Elimination of the heavy metals chromium, nickel, copper, and zinc from the sludge and conversion of the residual sludge into inert slag were achieved. The thermal plasma inflight treatment of the sludge was accomplished with various plasma gas compositions and different specific energies. Heavy metals in the form of ferrite/chromite [(Ni,Zn,Fe)(Fe,Cr)₂O₄] were identified by X-ray diffraction. DC plasma experiments revealed that N ₂-O₂ plasma yielded the highest elimination rate of heavy metals for the given experimental conditions. The influence of the heat transfer rate on the elimination rate of heavy metals was investigated by comparing results from DC and RF plasma experiments. Except for Ni, leaching of heavy metals from deposits prepared by H₂ plasma treatment was minimal