改性膨润土对刚果红的吸附动力学及热力学研究

制备了十六烷基三甲基溴化铵(CTAB)改性膨润土,利用红外光谱和XRD对其结构进行了表征,考察了投加量和pH值对吸附性能的影响.结果表明: CTAB能插入膨润土层间;当投加量为4 g/L,pH值为4时,去除率最高达97.15%.改性膨润土对刚果红的吸附符合准二级动力学方程和Langmuir等温吸附方程,由吸附热力学方程计算得到的吸附焓变(ΔH)<0,吸附自由能变(ΔG)<0,吸附熵变(ΔS)<0,表明吸附为放热和熵减少的自发过程.

Kinetics and Thermodynamics Study on Congo Red Adsorption by CTAB Modified Bentonite

The modified bentonite was prepared using bentonite modified with cetyltrimethyl ammonium bromide (CTAB).The structure of this modified bentonite was characterized by fourier transform infrared spectra (FTIR) and XRD.The effects of the dosage and pH value on the adsorption of Congo red from water were studied.The thermodynamics and kinetics of Congo red adsorption on the modified bentonite was stuied also.It is shown that the CTAB could be inserted into the interlayer of bentonite with the removal rate as high as 97.15% when the dosage is 4 g/L and pH is 4.The adsorption process of Congo red on the modified bentonite followed the pseudo-second order kinetic equation and the adsorption behavior fited with the Langmuir sorption isotherm equation.The results of thermodynamic analysis are:enthalpy (ΔH)< 0,Gibbs free energy (ΔG)<0,and entropy (ΔS)<0,which suggest that the sorption is an exothermic, spontaneous and decreasing entropy process.