吸附温度对MgAl金属氧化物微观结构和吸附Cr(VI)性能的影响

Effect of Temperature on Microstructure and Cr(VI) Adsorption Capacity of MgAl Metal Oxides

研究了MgAl水滑石（LDH）焙烧产物（LDO）对Cr（VI）的吸附性能。考察了吸附温度对LDO吸附性能的影响,研究了吸附过程的热力学和动力学行为。结合XRD和FT-IR表征,阐明其吸附机理。结果表明,CrO42– 已成功插入水滑石层间,适当提高吸附温度有利于LDO恢复LDH晶相。在20－60℃范围内,随吸附温度升高,LDO对Cr（VI）吸附量增大,50－60℃时,Cr（VI）吸附量为91 mg/g。Cr（VI）的吸附平衡数据符合Langmuir模型方程,ΔGo为负值说明吸附过程为自发过程,ΔSo和ΔHo为为正值表明吸附为熵增的吸热过程。吸附动力学符合伪二级动力学模型，LDO的吸附活化能为20．04kJ／mol，表现为扩散控制的活性化学吸附过程。

The adsorption properties of Cr（VI） on the double oxides （LDO） from calcined MgA1 hydrotalcites （LDH） were investigated. The effect of temperature on the adsorption performances of the LDO was studied, and the adsorption kinetics and thermodynamics were studied at different adsorption temperatures, The samples were characterized by XRD and FT-IR to clarify the adsorption mechanism. The results indicated that CrO42- had intercalated into the interlayer structures of Mg-Al hydrotalcites. Moderately increasing temperature was beneficial for the reconstruction of LDH crystalline structure from LDO. In the temperature range of 20℃-60℃, adsorption capacity of the LDO was increased with temperature rising, it reached 91 mg/g in the temperature range from 50℃ to 60℃. The experimental data were well fit to the Langmuir equation. The negative values of ΔGo indicated that the adsorption process was spontaneous, and positive values of ΔSo and ΔHo showed the endothermic and entropy-increasing nature of the process. The adsorption was consistent with the pseudo-second order kinetic model The active energy value was 20.04 kJ/mol, which implying that the internal diffusion was the rate-determining step in the chemical adsorption.