胡敏酸-针铁矿复合胶体对Pb2+的吸附特征

摘要

采用批平衡试验法,研究了胡敏酸-针铁矿复合胶体对Pb2-的等温吸附特征及pH值、离子强度、温度及共存Cd2-对复合胶体吸附Pb+的影响.结果表明:在相同离子强度和温度条件下,pH值升高,最大吸附量(Smax)和吸附平衡常数(k)均增大,有利于吸附反应的进行.等温吸附方程以Langmuir方程拟合效果最好.当Pb2+平衡浓度为124.7mg/L时,吸附量增幅最大,达35mg/g.复合胶体对pb2+的吸附动力学方程以Elovich方程拟合效果最好.pH值增大,平衡吸附速率提高.在相同pH值和离子强度条件下,温度升高,最大吸附量、吸附平衡常数、自由能变△G°的绝对值均增加,表明升高温度有利于吸附反应的进行.在相同温度和pH值条件下,复合胶体对Pb2-的吸附量随着离子强度的增加而增加.当存在Cd2+时,复合胶体对Pb2+的吸附量有所降低,但Cd2+对Pb2+竞争吸附影响不大.%Through batch equilibrium experiment, the isothermal adsorption characteristics of divalent lead (Pb2+) on complex colloid of humic acid and goethite including the influences of pH, ion strengths (IS), temperature and the co-ion Cd2+ were all investigated. The results showed that under same conditions of IS and temperature, the maximum adsorption amount (Smax) and adsorption equilibrium constant (k) both increased with pH increasing, indicating that the increase of pH enhanced adsorption process. Meanwhile, the isotherm process was best fitted by Langmuir equation.While Pb2+ equilibrium concentration was 124.7mg/L, the increasing degree of adsorption was greatest, up to 35mg/g. In addition, for complex colloid, Elovich equation was best for fitting Pb2+ adsorption kinetic process, involving equilibrium adsorption rate increasing with pH increasing. At constant pH and IS, increasing temperature, Smax. k and absolute value of free energy change (△G0) all increasing, suggesting increasing temperature was liable to promote adsorption reaction. Furthermore, the adsorption of complex colloid for Pb2+ also increased with increasing IS while temperature and pH were same. However, while Cd2+ coexisted, the whole complex colloid showed a slight decreasing trend for Pb2+ adsorption, but the competitive effect of Cd2t for Pb2+ adsorption was not significantly observed.