改性壳聚糖对湘江河水中重金属污染物Cr（Ⅵ）的吸附

利用分子印迹技术和甲基丙烯酸对壳聚糖进行改性，并在改变吸附条件、吸附动力学和吸附等温线的基础上，对湘江样水中Cr（Ⅵ）进行吸附研究。结果表明：X射线衍射谱显示印迹聚合物的结晶能力减弱，但非结晶区面积增加，吸附点位数提高，对Cr（Ⅵ）的吸附容量增大；印迹聚合物对Cr（Ⅵ）的吸附能力随时间的延长而增加，8h后达到饱和，最佳吸附时间是吸附后4～8h，对Cr（Ⅵ）的提取率最大值为33．7％。提取液最佳pH值是4．5～7．5；提取率随着壳聚糖脱乙酰度的增大而增大，吸附效果最好的是90％脱乙酰度壳聚糖。吸附量随着壳聚糖的浓度增加而增加，饱和后对Cr（VI）的提取率变化相对平稳，实验测得最高去除率为98．3％。Cr（Ⅵ）印迹壳聚糖吸附的准一级动力学和二级动力学模型线性相关系数分别是0．9013和0．9875，吸附速率分别为0．0091min-’和7．129g／（mg·min）。Cr（VI）印迹壳聚糖的吸附更符合二级动力学模型，与Langmuir吸附等温线的拟合性比Freundlich吸附等温线的更好，计算得到的最大吸附容量为15．784mg／g，对河水中Cr（Ⅵ）的吸附效果明显。

Adsorption of Cr(VI) by modified chitosan from heavy-metal polluted water of Xiangjiang River,China

Methacrylic acid was used together with a molecular imprinting technique to modify chitosan. In addition, the adsorption kinetics and adsorption isotherms were recorded and the results were analyzed to investigate reparative adsorption for Cr（VI） from the polluted Xiangjiang River water. A comparative X-ray analysis shows that the degree of crystallization in the imprinted polymer was significantly weakened, the area of the non-crystalline region was larger. There were more adsorption sites in the imprinted polymer, and the adsorption capacity towards Cr（VI） was increased. The adsorption capacity of the imprinted polymer towards Cr（VI） increased with time and reaches saturation after 8 h. The optimal adsorption time was 4-8 h after the adsorption starting and the optimal pH value for the solution was in the range of 4.5-7.5. When the chitosan reaches saturation, the adsorption capacity achieves a state of equilibrium, and the maximum Cr（VI） extraction rate reaches 33.7%. Moreover, the adsorption capacity of the imprinted polymer towards Cr（VI） increases with increasing chitosan concentration. In this situation, the Cr（VI） extraction rate shows little variation, and the maximum removal rate can reach 98.3%. Furthermore, the Cr（VI） extraction rate increases with an increase in the degree of deacetylation in the chatoyant and chitosan, with the best adsorption effect corresponding to 90% deacetylation. Fitting the adsorption data to the quasi first- and second-order kinetic models yields correlation coefficients of 0.9013 and 0.9875, respectively. The corresponding rate constants for the two models are 0.0091 min-1 and 7.129 g/（mg.min）, respectively. Hence, the adsorption using Cr（VI）-imprinted chitosan is more consistent with the second-order kinetics. Comparing the data to Freundlich and Langrnuir adsorption isotherms shows that the latter has a better linear fit and a maximum adsorption capacity of 15.784 mg/g.