掺锰水铁矿-壳聚糖珠对As（Ⅲ）的吸附及影响因素

Adsorption of As(Ⅲ) by Manganese-doped Ferrihydrite-Chitosan Beads and Its Influencing Factors

文章研究了掺锰水铁矿-壳聚糖珠状材料对As(Ⅲ)的吸附及其影响因素。材料制备时的干燥方法影响其结构和吸附性能。冻干的珠状材料内有大量的大孔和介孔,50℃真空干燥的珠状材料的孔相对较小,而25℃自然风干的珠状材料内则无明显孔结构。珠状材料对As(Ⅲ)的最大吸附量与比表面积的顺序相同,为冻干壳聚糖珠>真空干燥壳聚糖珠>风干壳聚糖珠。冻干壳聚糖珠吸附材料的吸附量是风干壳聚糖珠的2倍。随着p H的上升吸附量逐渐降低;共存阴离子H2PO4^-和SiO3^2-能显著抑制吸附剂对As(Ⅲ)的吸附能力。冻干壳聚糖珠对As(Ⅲ)的吸附符合准二级动力学模型和Langmuir等温线模型。经过3次再生后复合材料的吸附量仍有初始吸附量的88%左右,显示了良好重复使用性。XPS分析显示吸附材料中的Mn(Ⅳ)能氧化As(Ⅲ)为As(Ⅴ),从而明显提高壳聚糖珠对As(Ⅲ)的吸附性。

Adsorption of As(Ⅲ) by manganese-doped ferrihydrite-chitosan beads and its influencing factors are studied.The drying method in material preparation process affects its structure and adsorption performance. There are a lot of macroporous and mesoporous in the freeze-dried beads, and the holes of the vacuum-dried beads are relatively small, while there is no obvious porous structure in the natural air-dried beads at 25 ℃. The maximum adsorption capacity to As(Ⅲ) and specific surface area of chitosan beads follow the same order: freeze-dried chitosan beads > vacuum-dried chitosan beads > air-dried chitosan beads. The adsorption capacity of freeze-dried chitosan beads is twice as much as that of air-dried chitosan beads.With the increase of pH, the adsorption capacity decreases gradually;coexisting anions H2PO4^- and SiO3^2- can significantly inhibit the adsorption capacity of adsorbents for As(Ⅲ). The adsorption of As(Ⅲ) by freeze-dried chitosan beads conforms to quasi-second-order kinetic model and Langmuir isotherm model. After three times of regeneration, the adsorption capacity of the composite is still about 88% of the original adsorption capacity, which shows good reusability. XPS analysis showed that Mn(Ⅳ) in the adsorbent could oxidize As(Ⅲ) to As(Ⅴ), thus significantly improving the adsorption of As(Ⅲ) on chitosan beads.