title: Removal of Cr(VI) from low-temperature micro-polluted surface water by tannic acid immobilized powdered activated carbon.
abstract: In this study, food-grade tannic acid-immobilized powdered activated carbon (TA-PAC) was prepared, and adsorption of Cr(VI) (0.500 mg/L) onto TA-PAC as a function of pH, contact time, adsorption capacities and adsorption isotherms at 280 K was investigated. The results indicated that the immobilization process introduced abundant acid functional groups. The adsorption capacity of TA-PAC was found to be pH-dependent, and the optimal pH value was found to be 4.0. The equilibrium time was 240 min for TA-PAC. Adsorption data for total chromium were modeled using both two-parameter and three-parameter isotherm models. Freundlich and linear forms of three-parameter models yielded the best results for all of the data. Desorption studies of immobilized material suggested that the immobilization of food-grade tannic acid is steady. The adsorption mechanism of Cr(VI) on TA-PAC was assumed to be a comprehensive process consisting of surface reduction of Cr(VI), esterification between catechol and chromate, and ion exchange.
authors.affiliation: School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, PR China. hitlwg@126.com
authors.forename: Weiguang
authors.initials: W
authors.lastname: Li
authors.forename: Xujin
authors.initials: X
authors.lastname: Gong
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.forename: Duoying
authors.initials: D
authors.lastname: Zhang
authors.forename: Hainan
authors.initials: H
authors.lastname: Gong
mesh_terms: D002244:Carbon / Q000737:chemistry*; D002857:Chromium / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D008962:Models, Theoretical; D011208:Powders; D013634:Tannins / Q000737:chemistry*; D013816:Thermodynamics; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*
chemical_list: D011208:Powders; D013634:Tannins; D014874:Water Pollutants, Chemical; D002857:Chromium; D002244:Carbon