稻秸对Pb2+的吸附特性

为探讨稻秸对废水中Pb2+的吸附特性,通过静态试验研究了吸附时间、离子浓度、吸附剂用量、初始pH和温度对稻秸吸附Pb2+的影响,并分析了其吸附动力学、等温吸附平衡及热力学特征.结果表明:稻秸吸附Pb2+的过程进行得很快,60 min时去除率达到85.64%,其吸附动力学过程以准二级动力学方程拟合效果最好;吸附等温线符合Langmuir和Freundlich等温吸附模型,其中以Freundlich模型为最优,与吸附强度有关的常数在2～10之间,吸附容易发生,而使用Langmuir模型拟合最大吸附量的理论值可达13.67 mg/g;随着稻秸投加量的增加,Pb2+的去除率逐渐增加,单位吸附量逐渐减小;溶液初始pH对稻秸吸附Pb2+的影响较大,pH在4～6时去除率可达92%以上;稻秸对Pb2+的吸附受温度影响较小,吸附过程具有自发性、放热性和熵增特性.

Adsorption Characteristics of Pb2+on Rice Straw

To explore the adsorption characteristics of Pb2+on rice straw,the effects of environmental factors including adsorption time,initial concentration of metal ions,rice straw dosage,initial pH and temperature on metal biosorption were studied.In addition,the relevant equilibrium,kinetics and thermodynamics were discussed.The results showed that the adsorption of Pb2+ on rice straw was a very fast process which could be expressed well by the pseudo-second-order equation.The removal rate of Pb2+ was up to 85.64% at 60 minutes.The adsorption isotherms were in good agreement with the Langmuir and Freundlich models,though the latter was better.The maximum adsorption capacity for Pb2+ reached 13.67 mg/g using the Langmuir model.With the increase of rice straw dosage,the removal rate of Pb2+ increased.The pH had a prominent effect on the adsorption of Pb2+;the removal rate reached over 92% when the pH was between 4 and 6.Temperature had no significant effect on the adsorption of Pb2+.Thermodynamic analysis showed that the adsorption process was spontaneous,exothermic and entropy increasing.