铁氧化物改性坡缕石粘土对Cr(Ⅵ)的吸附性能

The adsorption of chromium (Ⅵ) on iron oxide-modified palygorskite clay

以铁氧化物对坡缕石粘土进行包覆改性,通过静态吸附实验研究了改性坡缕石吸附Cr(Ⅵ)的特性,探讨了吸附的动力学特征、吸附平衡、热力学参数和吸附机理。结果显示,改性坡缕石对Cr(Ⅵ)的吸附随溶液初始pH值的升高显著减弱,在初始pH值为4.0时,吸附90 min可达平衡,吸附过程能较好地符合pseudo-second-order动力学方程,速率常数k2随温度的升高增大,表观活化能为18.90 kJ/mol;吸附平衡能较好地符合Langmuir方程,吸附过程吸热,ΔH为28.29 kJ/mol,ΔG为-25～-20 kJ/mol,是物理吸附和化学吸附并存的过程。

The palygorskite clay coated with iron oxide was prepared as the adsorbent and the adsorption properties and mechanisms of adsorbing Cr （Ⅵ） were investigated,with a discussion on the adsorption kinetics and thermodynamic characteristics.The results demonstrate that the adsorption function of Cr （Ⅵ） on modified palygorskite decreases significantly with increasing pH.The equilibrium can be reached in about 90 minutes and the adsorption processes seem to follow pseudo-second-order equation most effectively at an optimum pH of 4.0,the rate constant increases with the rise of temperature and the adsorption activation energy is 18.90 kJ/mol.Adsorption isotherms fit Langmuir equation fairly well,the adsorption enthalpy is 28.29 kJ/mol and the adsorption Gibbs free energy changes are in the range of-25 ～-20 kJ/mol.The adsorption process is endothermic and spontaneous,with the coexistence of physical adsorption and chemical adsorption.