黑碳吸附汞砷铅镉离子的研究

Sorption of Hg^(2+),As^(3+),Pb^(2+) and Cd^(2+) by Black Carbon

由玉米秸秆燃烧物提取黑碳,测定了黑碳阳离子交换量,研究了黑碳对汞(Hg2+)、砷(As3+)、铅(Pb2+)和镉(Cd2+)离子的等温吸附、吸附及解吸动力学特征。结果表明,黑碳阳离子交换量为0.15cmol·kg-1,远低于矿物和腐植酸。黑碳对Hg2+、As3+、Pb2+和Cd2+的等温吸附是非线性表面吸附,可用Langmiur方程拟合;黑碳对Pb2+最大吸附量远大于对Hg2+、As3+和Cd2+的;黑碳对Hg2+、As3+、Pb2+和Cd2+吸附约5h达平衡;吸附动力学过程包括吸附快反应阶段和慢反应阶段,可用动力学一级方程和双常数速率方程描述;黑碳对Hg2+、As3+、Pb2+和Cd2+吸附速率、吸附亲和力和最大吸附量有:Pb2+>As3+>Hg2+>Cd2+;黑碳吸附的Hg2+、As3+、Pb2+和Cd2+易解吸,30min内洗脱率高达85%以上。

To study the possible influence on the removal behavior of heavy metal ions caused by black carbon（BC）, the BC was derived from corn-residue field burns, the cation exchange capacity（CEC）of BC was determined, the sorption isotherm and sorption-desorption kinetics of Hg^2＋, As^2＋, Pb^2＋ and Cd^2＋ on BC was studied. The CEC of BC was 0.15 cmol· kg^-1 and much lower than those of clay minerals and humic acids. The sorption on BC was mainly nonlinear surface adsorption. The Langmiur equation fitted the sorption data very well, the maximum sorption capacities of Pb^2＋ on BC was much larger than those of Hg^2＋, As^3＋ and Cd^2＋. The sorption equilibrium of Hg^2＋, As^2＋, Pb^2＋ and Cd^2＋ on BC almost reached in 5 hours. The sorption kinetics included the initial fast phase and the final slow phase. The first-order kinetic reaction and double constant rate equation could describe the sorption kinetics well. The sorption rate, affinity and maximum sorption capacities followed the sequence： Hg^2＋, As^2＋, Pb^2＋ and Cd^2＋. The adsorbed Hg^2＋, As^2＋, Pb^2＋ and Cd^2＋ on BE was desorbed easily with the desorption rate larger than 85% in 30 minutes.