不同来源太湖沉积物粒径分布及其对Cu的吸附特征

摘要

以不同来源的太湖沉积物为研究对象,利用Mastersizer 2000型激光粒度分析仪测定沉积物的粒度组成,利用筛析法和吸管法对不同来源沉积物进行分级,测定不同粒径沉积物中Cu含量及不同粒径沉积物对Cu2+的饱和吸附量,研究沉积物对水溶液中Cu(Ⅱ)的吸附特性,从粒径分级和动力学角度探讨了太湖沉积物对Cu的吸附机理.结果表明:太湖沉积物粒径范围在0.002～0.1 mm,其颗粒组成以粉砂级与粘粒级为主,养殖区沉积物小粒径比例较高,小于0.05 mm粒径沉积物的比例为82.45％；吸附实验研究表明,粒径小于0.005 mm和0.005～0.01 mm沉积物中Cu含量较高,且此粒径沉积物对Cu(Ⅱ)的吸附量最大；吸附动力学研究表明,沉积物的吸附过程分为快反应和慢反应两个阶段,且吸附过程以表面吸附为主,伪二级动力学方程对动力学曲线拟合较好,其R2值达0.999以上.吸附热力学的研究结果表明:Freundlich方程比较适合描述沉积物对Cu2+的吸附等温线,其R2大于0.99,对照区、养殖区和生活污水区沉积物对Cu( Ⅱ)的最大吸附量分别为229.20,249.98,261.20 mg·kg-1,方程式中的强度因子1/n不适合描述沉积物与重金属离子的结合能力.%Sediments from different sources were sampled from Taihu Lake located Huzhou area in Zhejiang Province. Particle size test, particle-size grading and the copper content in different particle-size sediment were measured by Mastersizer 2000 laser particle size analyzer to study the absorption capacity of copper. The adsorption kinetics of Cu2+ on the sediment samples of Taihu Lake and the equilibrium adsorption of the different size sediment samples were studied by isothermal adsorption experiment. The adsorption mechanism was discussed by the particle size grading and the kinetic. The results showed that the size of Taihu Lake was ranged from 2 to 100 μm, and the sediments consisted of sand and clay-based powder. The copper content and the absorption capacity of Cu2+ were different in the different particle size sediment samples. Sediments with small size had strong adsorption ability. The copper content in particle-size which was less than 0.01mm was the highest in our study. The particle-size of 0.1 ~ lmm had the strongest copper adsorption capacity. The adsorption reaction could be divided into fast reaction stage and slow reaction stage and the adsorption process followed by surface adsorption. The adsorption kinetics followed a pseudo-second-order model (R2>0.999). The adsorption date fitted well into the Freundlich adsorption isotherm (R2>0.99). The maximum adsorption capacity of Cu2+ were 232, 278, 287 mg·kg-1 and the parameter 1/n was not suitable for the description of bonding capacity of heavy metal and sediments.