Treating electroplating residues with thermal plasmas

Abstract

A process for the treatment of sludge containing heavy metals generated in electroplating processes has been developed. The process is based on the use of a plasma system and allows the recovery of some of the metals contained in the sludge, while generating totally inert slags as by-products. Experiments performed for the treatment of zinc-rich residues (20% zinc) showed that zinc can be recovered in the process (metallic or oxide form) while generating both a ferrous slag containing heavy metals and a ceramic type of slag (originated from the silica and calcium oxide contained in the sludge). The two types of slags are inert and produced when treating any type of electroplating residues using the described technology; the slags can be sold to steelmakers (in the case of the metallic slag), used as bedroad fillers (in the case of the ceramic slag), or discarded without risks for the environment. Laboratory-scale tests have been conducted, and a pilot plant that is capable of treating up to 150 kg/h of electroplating residues has been built.