污泥活性炭对染料的吸附动力学研究

Kinetics of adsorption of dyes by sludge activated carbon

以城市污水处理厂脱水污泥作为原料,采用化学活化法(ZnCl2作为活化剂)制得污泥活性炭,全面研究了污泥活性炭对活性艳红K-2BP、酸性大红GR和直接紫N这3种染料的吸附动力学行为.结果表明,污泥活性炭可以有效地吸附染料,实现污泥的资源化;3种染料的平衡吸附量qe均随着染料初始浓度和温度的增大而增大,相同条件下平衡吸附量qe的大小顺序为:酸性大红GR>活性艳红K-2BP>直接紫N;伪二级动力学模型能够很好地描述3种染料在污泥活性炭上的吸附动力学行为;对于活性艳红K-2BP和直接紫N,颗粒内扩散过程是该吸附速率的控制步骤,但不是唯一的速率控制步骤,吸附速率同时还受颗粒外扩散过程的控制,而对于酸性大红GR,颗粒内扩散过程不是吸附速率的控制步骤;污泥活性炭对3种染料的吸附是一个吸热过程,吸附活化能较小,主要为物理吸附过程.

In this paper,sludge activated carbon（SAC） was prepared from municipal wastewater treatment plant sludge using chemical activation （the activation reagent was ZnCl2）,and the kinetics of adsorption of three dyes（Reactive Brilliant Red K-2BP,Acid Scarlet GR,Direct Violet N） by SAC was studied.The results indicate that the SAC can adsorb dyes effectively.The amount of each dye adsorbed at equilibrium（qe） increases with the increase of initial dye concentration or temperature.Using the same conditions,the order of qe of the three dyes is as follows： Acid Scarlet GR〉 Reactive Brilliant Red K-2BP 〉Direct Violet N.The adsorption of each dye by SAC follows the pseudo second-order kinetic model.For Reactive Brilliant Red K-2BP and Direct Violet N,the adsorption rate is not only controlled by intra-particle diffusion but also by extra-particle diffusion.However,for Acid Scarlet GR,intra-particle diffusion is not the rate-controlling step.The adsorption of each dye by SAC,which is an endothermic process,has a small energy of activation,and is mainly a physical adsorption process.