Adsorption behavior of condensed phosphate on aluminum hydroxide

作     者：GUAN Xiao-hong CHEN Guang-hao SHANG Chii 

作者机构：School of Municipal and Environmental Engineering Harbin Institute of Technology Harbin 150090 China Department of Civil Engineering Hong Kong University of Science and Technology Hong Kong China 

出 版 物：《Journal of Environmental Sciences》 (环境科学学报（英文版）)

年 卷 期：2007年第19卷第3期

页      面：312-318页

核心收录：

学科分类：08[工学] 0815[工学-水利工程] 

主　　题：activation energy aluminum hydroxide condensed phosphate eutrophication surface charge 

摘      要：Sodium pyrophosphate （pyro-P, Na4P2OT）, sodium tripolyphosphate （tripoly-P, Na3P3O10）, and sodium hexametaphosphate （meta-P, （NaPO3）6） were selected as the model compounds of condensed phosphate to investigate the adsorption behavior of condensed phosphate on aluminum hydroxide. The adsorption was found to be endothermic and divisible into two stages： （1） fast adsorption within 1 h; and （2） slow adsorption between 1 and 24 h. The modified Freundlich model simulated the fast adsorption stage well; the slow adsorption stage was described well by the first-order kinetics. The activation energies of pyro-P, tripoly-P, and meta-P adsorption on aluminum hydroxide were determined to be 20.2, 22.8 and 10.9 kJ/mol P adsorbed, respectively, in the fast adsorption stage and to be 66.3, 53.5 and 72.5 kJ/mol P adsorbed, respectively, in the slow adsorption stage. The adsorption increased the negative charge of the aluminum hydroxide surface. Transmission electron microscopy and energy dispersive X-ray analysis analyses provided evidence that the adsorption was not uniform on the surface and that the small crystals contributed more to the fast adsorption than the normal sites did. The results from X-ray fluorescence spectrometry and X-ray photoelectron spectroscopy tests also revealed the uneven adsorption of condensed phosphate as a function of the penetration depth. More condensed phosphates were adsorbed on the outer surface of aluminum hydroxide than in its inner parts.