钛柱撑蒙脱石对镍离子和锰离子的吸附机理

Adsorption Mechanism of Titanium pillared Montmorillonite for Nickel and Manganese Ions

摘要:

以钠基蒙脱石(Na-MMT)、钛酸四丁酯作基质材料，通过溶胶-凝胶法制备了钛柱撑蒙脱石(Ti-MMT)。利用XRD、FTIR及SEM对Ti-MMT进行了表征，考察了不同吸附条件对Ti-MMT吸附Ni2+和Mn2+的影响，并重点分析水溶液pH对Zeta电位及吸附的影响，探究了Ti-MMT吸附Ni2+和Mn2+的机理。结果表明：Ti-MMT具有较大的晶面间距(d001=2.94 nm)；pH对吸附Ni2+与Mn2+有较大影响，去除率随初始pH增加而提高。在pH=7，初始质量浓度为50 mg/L，Ti-MMT投加量分别为5和9 g/L时，Ni2+在318 K下吸附120 min，吸附量可达9.46 mg/g，去除率可达94.59%，Mn2+在328 K下吸附180 min，吸附量可达4.82 mg/g，去除率可达86.73%。此外，Ti-MMT对两种离子的吸附都更符合Temkin等温吸附模型及拟二级动力学模型，吸附过程受液膜扩散、颗粒内扩散等环节控制，且以离子交换的化学吸附为主。热力学分析表明Ti-MMT对Ni2+的吸附属于自发吸热熵增过程，而Mn2+属于吸热熵增的非自发过程。

Abstract:

Titanium pillared montmorillonite (Ti-MMT) was prepared by sol-gel method using sodium montmorillonite (Na-MMT) and tetrabutyl titanate as matrix materials. The Ti-MMT were characterized by XRD, FTIR and SEM. Then, the effects of different adsorption conditions on the adsorption of Ni2+ and Mn2+ on Ti-MMT were investigated, and the effect of pH on Zeta potential and adsorption was emphatically analyzed. The mechanism of Ti-MMT adsorption of Ni2+ and Mn2+ was investigated. The results show that Ti-MMT has a large interplanar spacing (d001=2.94 nm); pH has a great influence on adsorption, and the removal rate of Ni2+ and Mn2+ increases with the increase of initial pH. At pH=7, the dosage of Ti-MMT is 5 g/L, the initial mass concentration of Ni2+ is 50 mg/L, and the adsorption time is 120 min at 318 K, Ni2+ adsorption capacity can reach 9.46 mg/g, and the removal rate can reach 94.59%. At pH=7, the dosage of Ti-MMT is 9 g/L, the initial mass concentration of Mn2+ is 50 mg/L, and the adsorption time is 180 min at 318 K, Mn2+ adsorption capacity can reach 4.82 mg/g, and the removal rate can reach 86.73%. In addition, Ti-MMT adsorption of both ions is more consistent with Temkin isotherm adsorption, and the pseudo-second-order kinetics model. The adsorption process is controlled by liquid membrane diffusion and intra-particle diffusion, and ion exchange chemisorption is dominant. Thermodynamic analysis shows that the adsorption of Ni2+ by Ti-MMT belongs to the process of spontaneous endothermic entropy increase, while Mn2+ belongs to the non-spontaneous process of increasing endothermic entropy.