title: Characterization of Cr(VI) removal from aqueous solutions by a surplus agricultural waste--rice straw.
abstract: The removal of Cr(VI) from aqueous solution by rice straw, a surplus agricultural byproduct was investigated. The optimal pH was 2.0 and Cr(VI) removal rate increased with decreased Cr(VI) concentration and with increased temperature. Decrease in straw particle size led to an increase in Cr(VI) removal. Equilibrium was achieved in about 48 h under standard conditions, and Cr(III), which appeared in the solution and remained stable thereafter, indicating that both reduction and adsorption played a part in the Cr(VI) removal. The increase of the solution pH suggested that protons were needed for the Cr(VI) removal. A relatively high level of NO(3)(-) notably restrained the reduction of Cr(VI) to Cr(III), while high level of SO(4)(2-) supported it. The promotion of the tartaric acid modified rice straw (TARS) and the slight inhibition of the esterified rice straw (ERS) on Cr(VI) removal indicated that carboxyl groups present on the biomass played an important role in chromium remediation even though were not fully responsible for it. Isotherm tests showed that equilibrium sorption data were better represented by Langmuir model and the sorption capacity of rice straw was found to be 3.15 mg/g.
authors.affiliation: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Gao
authors.forename: Yunguo
authors.initials: Y
authors.lastname: Liu
authors.forename: Guangming
authors.initials: G
authors.lastname: Zeng
authors.forename: Weihua
authors.initials: W
authors.lastname: Xu
authors.forename: Ting
authors.initials: T
authors.lastname: Li
authors.forename: Wenbin
authors.initials: W
authors.lastname: Xia
mesh_terms: D000327:Adsorption; D001673:Biodegradation, Environmental; D002274:Carcinogens, Environmental / Q000737:chemistry / Q000302:isolation & purification*; D002857:Chromium / Q000737:chemistry / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D012275:Oryza; D013696:Temperature; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*; D014873:Water Pollutants / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
chemical_list: D002274:Carcinogens, Environmental; D014873:Water Pollutants; D002857:Chromium