Recovery of Chromium from Plating Wastes

Abstract

Recovery of chromium from a plating sludge is discussed. The process consists of two parts: roasting the sludge with sodium carbonate (Na2CO3) and calcium oxide (CaO), followed by leaching. The optimal parameters for roasting are a temperature range of 950 to 1000°C and Na2CO3 and CaO contents of 2.4 and 2.8 mol per mole of chromium oxide (Cr2O3) respectively. Demineralized water is recommended for the leaching of sodium chromate (Na2CrO4) from the agglomerate formed during roasting. The leached water is recycled through a strongly acidic cation exchanger followed by a weakly basic anion exchanger. A solution of chromate or chromic acid having a concentration up to 60 kg Cr/m3 is obtained.

Characterization of stainless steel pickling bath sludge and its solidification/stabilization

“…Chromium concentration up to 130,000 mg/kg has been reported [8,9]. Among many forms of chromium, Cr(VI) is the most important one because of its toxicity, solubility, and mobility characteristics [7,8,10].…”

“…Chromium concentration up to 130,000 mg/kg has been reported [8,9]. Among many forms of chromium, Cr(VI) is the most important one because of its toxicity, solubility, and mobility characteristics [7,8,10]. Most treatment methods had aimed to reduce the leaching of chromium to meet the toxicity characteristics leaching procedure (TCLP) extraction limit of less than 5 mg/l because of the complexity of chromium chemistry [11,12].…”