title: Theoretical and experimental study of the mechanisms of phosphate removal in the system containing Fe(III)-ions.
abstract: A process-oriented investigation of phosphate removal by ferric salt was carried out in this study. The kinetics of amorphous ferric phosphate (FePO4(s)) formation has been investigated over the pH range of 6.0-8.0 using sulfosalicylic acid as a competitive ligand. The FePO4(s) formation rate constants varied in a narrow range over the pH range examined in this study. And the maximum of (0.90 ± 0.11) × 104L mol-1s-1was obtained at pH 7.5 and the minimum value of (0.05 ± 0.01) × 104L mol-1s-1was obtained at pH 6.0. These values are two orders of magnitude lower than the rate constants for Fe(III) hydrolysis-precipitation, and hence, the extent of FePO4(s) formation when ferric ions are added to aqueous solution is extremely low. Subsequently, the characteristics of the amorphous ferric oxide (AFO) with different ages were investigated, and it was found that the BET surface area, the average pore width, and the charge capacitance were various for different AFO with various ages. Phosphate adsorption by AFO was significantly affected by AFO aging and the manner of adding Fe(III), which was successfully described by a diffuse layer model. By using surface sites concentration obtained, the kinetics constant of AFO aging could be calculated by a functional equation at a certain pH and time. Graphic abstract Description of the precipitation and aging processes for the phosphate removal by Fe(III)-ions.
authors.affiliation: National Engineering Laboratory of Coal-fired Pollutants Emission Reduction, School of Energy and Power Engineering, Shandong University, Jinan, 250100, People's Republic of China. maoyanpeng@sdu.edu.cn.
authors.forename: Yanpengy
authors.initials: Y
authors.lastname: Mao
authors.affiliation: National Engineering Laboratory of Coal-fired Pollutants Emission Reduction, School of Energy and Power Engineering, Shandong University, Jinan, 250100, People's Republic of China.
authors.forename: Shanxiu
authors.initials: S
authors.lastname: Yang
authors.affiliation: School of Environmental Science and Engineering, Shandong University, Jinan, 250100, People's Republic of China.
authors.forename: Qinyan
authors.initials: Q
authors.lastname: Yue
authors.affiliation: National Engineering Laboratory of Coal-fired Pollutants Emission Reduction, School of Energy and Power Engineering, Shandong University, Jinan, 250100, People's Republic of China.
authors.forename: Wenlong
authors.initials: W
authors.lastname: Wang
mesh_terms: D000327:Adsorption; D011232:Chemical Precipitation; D005290:Ferric Compounds / Q000032:analysis / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008962:Models, Theoretical; D010710:Phosphates / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods*
chemical_list: D005290:Ferric Compounds; D010710:Phosphates; D014874:Water Pollutants, Chemical; C000499:ferric oxide; C035885:ferric phosphate
keywords: Adsorption; Fe(III); FePO4; Kinetics; Phosphate; Precipitate aging