新型高分子絮凝剂对水中Hg2+的去除研究

为提高含汞废水的处理效率及简化处理流程,用化学合成方法将二硫代羧基引入到聚乙烯亚胺中,制备出一种新型高分子絮凝剂聚乙烯亚胺基黄原酸钠(PEX)。考察了絮凝剂投加量、水样初始pH值对PEX去除Hg2+效果的影响,并研究了水样中存在无机阳离子(Na+、Ca2+、Fe3+)、含浊物质时,PEX对Hg2+的捕集性能。结果表明,该絮凝剂对Hg2+具有很好的捕集效果,当PEX投加量为6.6 mg/L时,Hg2+的去除率达到最大值(96.1%)。pH值为2.0~5.0时,PEX对Hg2+的捕集能力随着水样初始pH值的增大而增强,在其等电点pH=3.0时,Hg2+的去除率最低,仅为35.3%。水样中存在一定质量浓度(50 mg/L)Na+、Ca2+、Fe3+时,会促进Hg2+的去除;而含浊物质(77.0NTU)的存在会对Hg2+的去除起一定的抑制作用,加大PEX的投加量,此抑制作用会减弱,而体系中的浊度会明显降低。

Keywords On the removal efficiency of mercury ions from aqueous solution by means of novel macromolecule flocculants

The present paper is dedicated to the study of the removal efficiency of mercury ions from aqueous solution by means of novel macromolecule flocculants.In order to increase the efficiency of treating sewage with mercury ions and simplify its process,we have prepared a novel water-soluble macromolecule flocculant polyethyleneimine-sodium xanthogenate(PEX) by making polyethyleneimine react with CS2 in alkaline medium,a dithiocarboxy group,grafted to polyethyleneimine.Besides,we have also investigated the influence of the flocculant dosage and the initial pH of the solution on the removing efficiency of mercury with mercury-containing sewage sample.In addition,we have also examined the behavior of trapping mercury for the water samples containing mercury as well as inorganic cations(i.e.Na+,Ca2+ and Fe3+ ions) or turbidity-causing substances.The experimental data show that the macromolecule flocculant PEX is endowed with two functions in the experiment: the chelation-precipitation and the flocculation-precipitation.In the mercury-containing water sample,PEX enjoys strong binding power with Hg2+,and therefore,the removal rate of Hg2+ could be made to reach 96.1%,the maximum value,when the dosage of PEX was 6.6 mg/L.But,when the pH range remained between 2.0-5.0,the trapping power for Hg2+ by PEX would increase with the increase of pH value.Moreover,the removal rate of Hg2+ could also reach the lowest value,i.e.35.3% at pH 3.0,which was the isoelectric point of PEX.When the water samples contained both Hg2+ and some inorganic cations,that is,Na+,Ca2+ and Fe3+ ions,the presence of the cations would promote the removal of Hg2+.However,the presence of turbidity-causing substance would delay the removal of Hg2+ to a certain extent,but this effect tended to drop by the increased dosage of PEX,as the turbidity would get reduced evidently in the system.Last of all,when the sewage with Hg2+ was treated by PEX,its advantages would become remarkable,that is,the lower the dosage of PEX,the better the flocculant settlement and the higher removal rate of Hg2+ would be.Therefore,the novel macromolecule flocculants would be expected to be a novel material for treating the sewage with mercury ions.