污泥基活性炭去除水中重金属离子效能与动力学研究

以城市污泥为主要原料制备了污泥基活性炭(SAC),考察了其对重金属离子的吸附去除效能和吸附动力学规律.并选择了2种商品活性炭(煤质炭,MAC和椰壳炭,YAC)作为对比,以初始浓度为50mg/L的Cu(II),Pb(II),Cd(II),Cr(VI)4种重金属离子为去除对象,分别进行了3种活性炭的表面理化性质分析及其对4种重金属离子的吸附试验.结果表明,SAC的比表面积和微孔容积仅为YAC和MAC的1/3~1/2,吸附速率也相对较慢,但其对Cu(II),Pb(II),Cr(VI),Cd(II)的平衡吸附量却远大于2种商品活性炭,分别为9.9,8.9,8.2,5.4mg/g,说明SAC表面的高酸性基团含量对重金属离子的吸附起到了关键作用;Langmuir与Freundlich吸附等温模型均能较好地拟合SAC对Cu(II)和Pb(II)的吸附,SAC对Cr(VI)的吸附过程更符合Langmuir模型,而SAC对于Cd(II)的吸附过程用Langmuir与Freundlich两个模型均不能较好地拟合,说明SAC表面缺少能够与Cd(II)发生反应的结合位点.

Efficiency and kinetics of heavy metal removal from water by sludge-based activated carbon

This study investigated the efficiency and kinetics of adsorptive removal of heavy metals by sludge-based activated carbon (SAC) prepared from municipal sludge. Surface physicochemical properties of SAC and its adsorption capacities for four heavy metals, i.e., Cu(II), Pb(II), Cr(VI) and Cd(II), with an initial concentration of 50 mg/L were analyzed in comparison with two types of commercial activated carbon: coal-based activated carbon (MAC) and coconut shell-based activated carbon (YAC). The results showed that specific surface area and micropore volume of SAC were only 1/3~1/2 of those for either MAC or YAC. Adsorption of the four heavy metals onto SAC was relatively slower than that onto MAC or YAC. However, the equilibrium adsorption capacities of SAC for Cu(II), Pb(II), Cr(VI) and Cd(II) were 9.9, 8.9, 8.2 and 5.4 mg/g, respectively, being much greater than those of the two commercial adsorbents. This revealed that the SAC surface with rich acidic functional groups played a crucial role in the adsorption of heavy metals. The adsorption of Cu(II) and Pb(II) onto SAC had a close agreement with both Langmuir and Freundlich models and the adsorption of Cr(VI) agreed better with Langmuir models. In terms of the adsorption of Cd(II), neither of the models described the isotherms satisfactorily, suggesting that the quantity of binding sites for Cd(II) on the surface of SAC was small.