蒙脱石-壳聚糖复合物对磷吸附性能的研究

Phosphate adsorption by composites of chitosan-saturated montmorillonite

为探究蒙脱石-壳聚糖复合物对水体中磷(P)的吸附性能和应用前景,将壳聚糖加载于蒙脱石,通过X射线衍射仪和傅立叶变换红外光谱表征该复合物结构,并通过静态吸附实验研究其对磷的吸附行为。结果表明,饱和吸附的壳聚糖能插层蒙脱石层间形成复合物;随pH从2增加到6,P在复合物上的吸附量增加,并在pH 6时达到最大吸附量16.15 mg·g^(-1),随着pH继续增加至9,吸附量减少至9.05 mg·g^(-1);P在复合物上约3 h达到吸附平衡,动力学吸附结果拟合准二阶方程较好,说明化学吸附为速率控制阶段;复合物对P的吸附为自发放热反应,在20~40℃范围内随温度上升,吸附量减少;等温吸附拟合Langmuir方程最佳,拟合最大吸附量为16.36 mg·g^(-1),pH 6条件下,复合物对P的吸附为均质吸附。该研究结果说明蒙脱石-壳聚糖复合物具有吸附P的应用价值。

The montmorillonite-chitosan composite had attracted wide interest because this ＂green＂ and low-cost natural material can meet many requirements of adsorbents. The composite has been used for removal of potential toxic elements, yet its adsorption of phosphate needs further study. Chitosan-saturated montmorillonite was characterized and used as an adsorbent for the removal of phosphate from an aqueous medium in this study. The results showed the adsorbed chitosan intercalated into the interlayer of the montmorillonite, and the adsorbed phosphate on the composite increased with increasing pH from 2 to 6, reaching its maximal amount of 16.15 mg·g^-1at pH 6. However, the adsorbed amount decreased with increasing pH from 6 to 9, and the phosphate adsorption reached equilibrium at about 3 h. The pseudo-second-order equation better fit the data than the other models did, indicating chemisorption might be the rate controlling step. The adsorption was spontaneous, feasible, and exothermic. The isotherm adsorption was best fitted by the Langmuir model, and the theoretical adsorption capacity was 16.36 mg·g^-1. These results could provide scientific basis for the application of the chitosan-montmorillonite composite in the removal of phosphate from aqueous media.