砷在新疆奎屯河沉积物上的吸附及有机酸对吸附的影响

Adsorption of arsenic on the sediments of Kuitun River in Xinjiang and the effects of organic acids on adsorption

有机酸作为沉积物中常见有机质,对地下水砷迁移行为具有重要影响。本研究考察了砷在新疆奎屯河流域沉积物主要成分上的吸附,并分析了有机酸对砷在针铁矿上吸附的影响。通过XRD表征及沉积物元素含量测定,发现该地区沉积物主要成分为碳酸钙、石英砂、磷酸铝和针铁矿,其中针铁矿对砷吸附的贡献最大。进一步考察常见有机酸(冰乙酸、丙二酸、丁二酸、戊二酸和柠檬酸)对砷在针铁矿上吸附的影响,结果显示,有机酸会抑制砷的吸附,且抑制作用与有机酸的结构具有相关性——随羧基数量增加和碳链长度减小,有机酸对砷吸附的抑制作用更为显著,其中,柠檬酸对砷吸附的抑制作用最显著。砷吸附过程符合准二级动力学及Freundlich吸附模型。红外光谱表征结果表明,柠檬酸和砷在针铁矿表面存在竞争吸附;Zeta电位测定结果表明,柠檬酸在针铁矿表面形成了带负电的络合物。

As a common organic matter in sediments,organic acids have important impacts on the migration behavior of arsenic in groundwater. We investigated the adsorption of arsenic on the main components of sediments in the Kuitun River Basin,Xinjiang,and examined the effects of organic acids on the adsorption of arsenic on goethite. Through XRD characterization and sediment element concentration measurement,we found that the main components of sediments in this area were calcium carbonate,quartz sand,aluminum phosphate,and goethite,with goethite contributing the most to arsenic adsorption. We further investigated the effects of common organic acids( glacial acetic acid,malonic acid,succinic acid,glutaric acid,and citric acid) on the adsorption of arsenic on goethite. The results showed that organic acids inhibited the adsorption of arsenic,with the inhibitory effect being related to the structure of the organic acids. As the increases of the number of carboxyl groups and the decreases of the length of the carbon chain,the inhibitory effect of organic acids on arsenic adsorption was more significant. Citric acid had the strongest effect on arsenic adsorption. The arsenic adsorption process conformed to the pseudo-second-order kinetics and Freundlich adsorption model. The results of infrared spectroscopy showed that citric acid and arsenic had competitive adsorption on the surface of goethite. The results of Zeta potential measurement showed that citric acid formed a negatively charged complex on the surface of goethite.