title: Removal of hexavalent chromium from acidic aqueous solutions using rice straw-derived carbon.
abstract: This study evaluates the removal of Cr(VI) from water by carbon derived from the burning of rice straw. Rice straw was burned in the air to obtain rice carbon (RC), and then the removal of Cr(VI) by RC was investigated under various pHs and ionic strengths. After the experiments, the oxidation state of Cr bound to RC was analyzed using X-ray photoelectron spectroscopy, which revealed that Cr bound to RC was predominately in the trivalent form. The results showed that upon reacting with RC, Cr(VI) was reduced to Cr(III), which was either adsorbed on RC or released back into solution. The extent and rate of Cr(VI) removal increased with decreasing solution pH because the Cr(VI) adsorption and the subsequent reduction of adsorbed Cr(VI) to Cr(III) both occur preferentially at low pH. The minimal effect of ionic strength on the rates of Cr(VI) removal and Cr(III) adsorption indicated specific interactions between Cr(VI)/Cr(III) and their surface binding sites on RC. These results suggest that rice straw-based carbon may be effectively used at low pH as a substitute for activated carbon for the treatment of Cr(VI) contaminated water.
authors.affiliation: Department of Soil and Environmental Sciences, National Chung Hsing University, Taichung 40227, Taiwan.
authors.forename: Nai-Hua
authors.initials: NH
authors.lastname: Hsu
authors.forename: Shan-Li
authors.initials: SL
authors.lastname: Wang
authors.forename: Yi-Huei
authors.initials: YH
authors.lastname: Liao
authors.forename: Shiuh-Tsuen
authors.initials: ST
authors.lastname: Huang
authors.forename: Yu-Min
authors.initials: YM
authors.lastname: Tzou
authors.forename: Yuh-Ming
authors.initials: YM
authors.lastname: Huang
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry*; D002857:Chromium / Q000737:chemistry / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D012275:Oryza; D010100:Oxygen / Q000737:chemistry; D012996:Solutions; D013052:Spectrometry, X-Ray Emission / Q000379:methods; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*; D014965:X-Rays
chemical_list: D012996:Solutions; D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion; D002244:Carbon; D010100:Oxygen