壳聚糖/CTAB复合改性膨润土对活性红X-3B的吸附

Adsorption of reactive red X-3B on chitosan/CTAB modified bentonite

以壳聚糖和十六烷基三甲基溴化铵(CTAB)为改性剂,制备了复合改性膨润土,并利用傅里叶红外光谱仪(FTIR)和X射线衍射(XRD)对其进行表征,研究了该改性膨润土对活性红X-3B的吸附效果.结果表明:壳聚糖能插入CTAB改性膨润土层间;当复合改性膨润土投加量为5 g·L^(-1),pH为3时,其对活性红X-3B的去除率可达99.15%;吸附过程符合拟二级动力学方程;吸附行为适于用Langmuir吸附等温方程描述.由吸附热力学方程计算得到,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.复合改性膨润土稳定性受搅拌时间和温度的影响不明显,pH较低(pH<3)时稳定性会降低.通过Zeta电位分析认为,静电作用为吸附的主要机理.经过6次吸附/再生后,改性膨润土对活性红X-3B的去除率仍在60%以上,表明复合改性膨润土具有较好的重复利用性.研究表明,该复合改性膨润土是一种对水体中活性红X-3B具有良好吸附能力的吸附剂.

In this study,the composite modified bentonite was prepared by using chitosan and cetyltrimethyl ammonium bromide（ CTAB） as modifier,and the structure was characterized by using Fourier transform infrared spectrum and X-ray diffraction（ XRD）. The adsorption of the modified bentonite on reactive red X-3B was investigated. The results indicate that the chitosan can insert into the interlayer of CTAB modified bentonite. The adsorptive efficiency reached 99.15% when the dosage of modified bentonite was 5 g·L^-1at pH 3. The sorption process followed the pseudo-second order kinetic equation. The adsorption behavior was fitted well with the Langmuir sorption isotherm equation. The results of thermodynamic analysis were as follows：enthalpy（ ΔH） 〈0,Gibbs free energy（ ΔG） 〈0,and entropy（ ΔS） 〈0,which suggested that the sorption was an exothermic,spontaneous and decreasing entropy process. Stirring time and temperature had little effect on the stability of composite modified bentonite,but the stability could be reduced at lower pH（ pH〈3）.The electrostatic interaction was considered to be the main mechanism for the adsorption. The adsorptive percentage was above 60% after 6times adsorption / regeneration,which indicated that the composite modified bentonite had good reuse potential. It is indicated that composite modified bentonite was a good adsorbent for reactive red X-3B.