铝污泥负载水合氧化铁-壳聚糖吸附水中Ni(Ⅱ)的研究

Adsorption of Ni(Ⅱ)in Water by Aluminum Sludge Loaded with Hydrous Ferric Oxides and Chitosan

采用铁盐和壳聚糖(CS)对铝污泥(AlS)进行改性,制得了铝污泥负载水合氧化铁-壳聚糖复合吸附剂(AlS-HFO-CS),用该吸附剂对Ni(Ⅱ)进行吸附实验,研究了溶液pH值、温度、吸附时间以及竞争离子对吸附过程的影响。利用XRD、FTIR和SEM技术表征了吸附剂的形貌并探讨AIS-HFO-CS对Ni(Ⅱ)的吸附机理。结果表明:水合氧化铁和壳聚糖能成功负载在铝污泥上;Ni(Ⅱ)的吸附量随溶液pH的增大而增大,不考虑沉淀作用,最优吸附pH为5~6,吸附平衡时间为4 h;Freundlich、Langmuir模型对AlS-HFO-CS吸附Ni(Ⅱ)的拟合效果相近,说明对Ni(Ⅱ)的吸附可能同时涉及多层物理吸附和单层化学吸附;吸附过程更符合拟一级动力学模型,颗粒内扩散模型拟合结果显示内扩散和边界层扩散共同控制吸附速率;整个吸附过程是吸热且自发进行的,并且存在着竞争性,吸附剂对Ni(Ⅱ)的吸附易受Cr(Ⅵ)和Cu(Ⅱ)的影响。

Aluminum sludge(AlS)was modified with hydrous ferric oxides(HFO)and chitosan(CS)to prepare compound adsorbent AlS-HFO-CS,which was used to adsorb Ni(Ⅱ).The effects of pH,temperature,adsorption equilibrium time and competing ions on the adsorption of AlS-HFO-CS were studied.The morphology of the adsorbent was characterized by XRD,FTIR and SEM methods and the adsorption mechanism of Ni(Ⅱ)was discussed.The results showed hydrous ferric oxides and chitosan can be successfully loaded on aluminum sludge.The adsorption capacity of Ni(Ⅱ)increases with the increase of pH.Without considering the precipitation,the optimal adsorption pH is 5—6.The adsorption equilibrium time is 4 h.The Langmuir and Freundlich models have similar fitting effects on the adsorption of Ni(Ⅱ)by AlS-HFO-CS.The adsorption process may involve both single-layer chemical adsorption and multi-layer physical adsorption.The kinetics of the adsorption process is more in line with the pseudo-first order kinetics.The fitting results of the intra-particle diffusion model show that the intra-particle diffusion and boundary layer diffusion control the adsorption rate together.The adsorption is a spontaneous and endothermic process.There is competition in the adsorption process.The adsorption of Ni(Ⅱ)by the adsorbent is affected by Cr(Ⅵ)and Cu(Ⅱ).