A kitchen waste compost was used to sorb Cr for various times from water containing either Cr(NO 3) 3 or CrO 3 in different concentrations. Scanning electron microscopy (SEM) results show that the composts have been partially oxidized by Cr(VI) during the sorption experiments. X-ray absorption near edge structure (XANES) simulation suggests that about 54.1-61.0% Cr sorbed on the compost is in form of organic Cr(III) through ionic exchange process with the rest being existent as Cr(NO 3) 3 in the Cr(III) sorption case; no Cr(OH) 3 is observed or expected because the solution pH after sorption experiments is ?3.31. However in the Cr(VI) sorption cases, about 18.0-24.9% of the total sorbed Cr is in form of Cr(OH) 3 precipitate due to the Cr(VI) chemical reduction by the compost and a contaminant increase in solution pH to ?5.94. Moreover, organic Cr(III) represents about 51.7-69.0% of the total sorbed Cr, and the rest (6.1-28.5%) is Cr(VI). ? 2005 Elsevier Ltd. All rights reserved.
