褐煤对汞和砷的吸附行为研究

为了研制用于含汞和含砷废水处理的新型高效材料,以褐煤作为吸附剂,研究了褐煤对汞和砷的吸附行为.首先进行了批量实验来论证接触时间对吸附性能的影响.数据采用准一级和准二级动力学方程进行拟合.并采用langmuir吸附等温线和Freundlich吸附等温线拟合了不同浓度Hg2+和As3+的吸附数据,并对吸附机理进行了探讨.同时也探讨了褐煤投加量和pH值对吸附效果的影响.结果 表明,褐煤对汞和砷的吸附动力学方程拟合结果符合准二级动力学模型(R2=0.9992,0.9991),数据与准二级模型很好的匹配说明Hg2+和As3+在褐煤上的吸附过程为化学吸附,Freundlich吸附模型(R2=0.9648,0.9814)可以更好地描述褐煤对汞和砷的吸附过程.褐煤对汞和砷的去除效果均随褐煤投加量的增大而明显增加,然后逐渐趋于平稳.在相同投加量时,褐煤对砷的去除效果好于对汞的去除效果,随pH值增大,吸附量增加,可能是因为酸性溶液中,H+与Hg2+和As3+互相排斥,阻碍Hg2+和As3+在溶液中的快速扩散.褐煤吸附汞和砷前后的SEM分析结果表明,吸附前褐煤表面凹凸不平,很粗糙,表面布满孔隙,这一结构特别有利于对重金属离子的吸附,褐煤饱和吸附后,其表面小孔已被填满.

Study on adsorption behavior of mercury and arsenic on lignite

In order to study a new type of high-efficient material for treating mercury and arsenic-containing wastewater, the adsorption behavior of mercury and arsenic on Lignite was studied. The batch experiment of the effect of contact time on adsorption performance was carried out. The data were fitted by quasi-first-order and quasi-second-order dynamic equations.The adsorption data of Hg_²⁺and As_³⁺with different concentrations were fitted by Langmuir and Freundlich isotherms and the adsorption mechanism was discussed. The effects of the dosage of lignite (0.1,0.2,0.3,0.4,0.5 g) and pH( 2,3,4,5,6 and 7) on the adsorption of Lignite were also discussed. The results show that the adsorption kinetic equation of Hg_²⁺ and As_³⁺ on lignite accords with the quasi-second-order kinetic model (R_²=0.9992,0.9991), and the data match well with the quasi-second-order model, which shows that the adsorption process of Hg_²⁺ and As_³⁺ on lignite is chemical adsorption, the adsorption process of mercury and arsenic by lignite is more consistent with Freundlich adsorption model (R_²=0.9648,0.9814), and the amount of adsorption increases with the increase of temperature. This is because the process is dominated by chemical adsorption, and the increase of temperature is favorable for the adsorption, however, the adsorption on the outer surface of lignite and the inner surface of macropore is close to saturation, and the adsorption amount remains unchanged. The removal efficiency of mercury and arsenic by lignite increased obviously with the