ICP-MS研究黄河河曲段表层沉积物对Pb(Ⅱ)和Cr(Ⅵ)的吸附-解吸特性

摘要

表层沉积物易于富集和释放水中重金属,是污染水体中重金属的源和汇,研究表明黄河河曲段水体中Pb和Cr重金属污染严重.以电感耦合等离子体质谱(ICP-MS)为检测手段,研究了在优化实验条件下,黄河河曲段表层沉积物对Pb(Ⅱ)和Cr(Ⅵ)的吸附特性和解吸特性.结果表明:黄河河曲段沉积物对Pb(Ⅱ)和Cr(Ⅵ)具有较强的吸附作用,在吸附初始5 min时吸附率均达到98％以上,且是自发的吸热过程(△G＜0,△H＞0).动力学实验显示,两种离子的吸附过程均符合准二级吸附动力学.等温吸附方程拟合发现,Pb(Ⅱ)的吸附符合Langmuir模型,而Cr(Ⅵ)的吸附符合Freundlich模型.解吸过程符合Elovich方程,且受pH的影响较大.Pb(Ⅱ)和Cr(Ⅵ)二元体系竞争效应研究表明,Pb(Ⅱ)的吸附率大于Cr(Ⅵ),且均低于单离子吸附率.扫描电子显微镜(SEM)和孔径及比表面积分析显示,黄河河曲段表层沉积物表面结构不规则,且具有相对较高比表面积.该研究揭示了Pb(Ⅱ)和Cr(Ⅵ)在黄河河曲段沉积物上的吸附-解吸行为,对评估沉积物污染风险和污染修复、掌握重金属离子与沉积物之间的作用机理具有一定指导意义.%Surface sediments,as the source and sink of heavy metals in polluted water,are easy to enrich and release heavy metals in water environment.In fact,the water of Hequ section of the Yellow River was polluted by Pb and Cr.In this paper,the adsorption and desorption characteristics of Pb(Ⅱ) and Cr(Ⅵ) onto the surface sediments of Hequ section of the Yellow River were investigated by using inductively coupled plasma mass spectrometry (ICP-MS) under the optimized experimental conditions.The results showed that the sediments had strong adsorption effects to Pb(Ⅱ) and Cr(Ⅵ) with endothermic and spontaneous process (△G＜0,△H＞0) with the adsorption rates reaching more than 98％ in the initial 5 min.Kinetic experiments showed that the adsorptions of Pb(Ⅱ) and Cr(Ⅵ) were in accordance with the pseudo-second-order kinetics.The isothermal adsorption equations revealed that the adsorption of Pb(Ⅱ) was consistent with the Langmuir model,while the adsorption of Cr (Ⅶ) followed the Freundlich model.The desorption processes kept to the Elovich equation,which was influenced chiefly by pH.The competitive adsorption of Pb(Ⅱ) and Cr(Ⅵ) showed that the adsorption rate of Pb(Ⅱ) was greater than that of Cr (Ⅶ),while both of them were lower than the single ion adsorption rate.Scanning electron microscopy (SEM),pore size and specific surface area analysis showed that the sediments of Hequ section of the Yellow River had an irregular surface structure and a relatively high specific surface area.This paper displayed the adsorption-desorption behaviors of Pb(Ⅱ) and Cr(Ⅵ) onto the sediments of Hequ section of the Yellow River,which has guiding significance for sediment pollution assessment,pollution remediation and mastering the mechanism of heavy metals onto the sediments.