XAS study of chromium recoverable from plating sludge

Because global natural metal resources are depleting, this study aim to examine the chemical feasibility of recovering chromium as Cr(VI) from a Cr(OH)3-containing plating sludge through a co-heating procedure of the plating sludge with a incinerator fly ash that is rich in calcium hydroxide. The critical step in the process of recovering Cr from plating sludge would be to convert the water-insoluble Cr(OH)3 into water-soluble Cr(VI). Results from Cr K-edge X-ray absorption near edge spectrum (XANES) suggest that majority of the Cr is in the form of CaCrO4 after the co-heating procedure of plating sludge and the incinerator fly ash at different temperatures. Heating the mixture of the plating sludge and the incinerator fly ash results in an oxidation of Cr(OH)3 that is basically water insoluble to Cr(VI) which is water soluble, consequently more Cr(VI) can be extracted with water and recovered from the heated mixture than from the non-heated plating sludge.