文章基本信息

标题：Phosphate Sorption Speciation and Precipitation Mechanisms on Amorphous Aluminum Hydroxide
本地全文：下载
作者：Xiaoming Wang ; Brian L. Phillips , Jean-François Boily , Yongfeng Hu , Zhen Hu , Peng Yang , Xionghan Feng , Wenqian Xu ; Mengqiang Zhu 等
期刊名称：Soil Systems
电子版ISSN：2571-8789
出版年度：2019
卷号：3
期号：1
页码：20-36
DOI：10.3390/soilsystems3010020
出版社：MDPI AG
摘要：Aluminum (Al) oxides are important adsorbents for phosphate in soils and sediments, and significantly limit Phosphate (P) mobility and bioavailability, but the speciation of surface-adsorbed phosphate on Al oxides remains poorly understood. Here, phosphate sorption speciation on amorphous Al hydroxide (AAH) was determined under pH 3–8 and P concentration of 0.03 mM–15 mM using various spectroscopic approaches, and phosphate precipitation mechanisms were discussed as well. AAH exhibits an extremely high phosphate sorption capacity, increasing from 3.80 mmol/g at pH 7 to 4.63 mmol/g at pH 3. Regardless of reaction pH, with increasing P sorption loading, the sorption mechanism transits from bidentate binuclear (BB) surface complexation with dP-Al of 3.12 Å to surface precipitation of analogous amorphous AlPO4 (AAP), possibly with ternary complexes, such as (≡Al-O)2-PO2-Al, as intermediate products. Additionally, the percentage of precipitated phosphate occurring in AAP linearly and positively correlates with P sorption loading. Compared to phosphate reaction with ferrihydrite, phosphate adsorbs and precipitates more readily on AAH due to the higher solubility product (Ksp) of AAH. The formation of AAP particles involves AlIII release, which is promoted by phosphate adsorption, and its subsequent precipitation with phosphate at AAH surfaces or in the bulk solution.
关键词：phosphate; speciation; sorption; precipitation; Al hydroxide phosphate ; speciation ; sorption ; precipitation ; Al hydroxide