Abstract:

A new absorbent for the removal of fluoride from drinking water was prepared by using lanthanum loaded chitosan beads crosslinked with ethylene glycol diglycidyl ether (EGDE)replacing glutaraldehyde (GLA).Static and dynamic adsorption of fluoride onto absorbents (CEB-La)was investigated, respectively. The effects of various physico-chemical parameters were studied. The results of static experiment showed that the optimal adsorption conditions were pH7. 0， water temperature 50℃, contact time 60 min, and oscillation frequency 120 r·min^-1. Treating the water containing F^- of 10 mg·L^-1 with CEB-La under this condition, the defluoridation rate was up to 92.9% and the residual concentration of F^- was 0.71 mg·L^-1, lower than 1.0 mg·L^-1. Furthermore, the adsorption isotherm could be described by the Langmuir and Freundlich models and the maximum adsorption capacity for F^- was 25.7 mg·g^-1. Sorption dynamics study revealed that the pseudo-second-order equation was suitable to describe the kinetics process of fluoride ions sorption onto the adsorbent. The used adsorbents could be regenerated by chelating with lanthanum after soaking in 0.5 mol·L^-1 of sodium hydroxide for 6 h. The removal efficiencies of F^- were related to the co-existing anions. In particular, the presence of CO^{2 -}₃ and HCO^-₃ led to a markedly decreased adsorption capacity of CEB-La for F^-. The results of dynamic experiment demonstrated that CEB-La was suitable for treating drinking water containing F^- of 2—15 mg· L^-1 when the volumetric flow rate was 3 ml·min^-1. Column kinetics were described by the Thomas model and the dynamic adsorption capacity was 3.67 mg·g^-1. Therefore, the absorbent is easy to regenerate, of low-cost, and has superior defluoridation properties, showing that it is a potential material for F^- removal in practice.

摘要：

利用乙二醇二缩水甘油醚(EGDE)替代戊二醛对壳聚糖微球进行交联，然后负载稀土镧离子La(Ⅲ)，制备得到新型的除氟剂（CEB-La）。研究了CEB-La对F^-的静态和动态吸附性能。静态吸附实验结果表明：该除氟剂的静态吸附条件为pH7.0、温度50℃、吸附时间60 min、振荡频率120 r·min^-1；当CEB-La用量3 g·L^-1时，对浓度10 mg·L^-1含氟水的除氟率可达92.9%；CEB-La对F^-的吸附过程符合Langmuir和Freundlich吸附等温线，饱和吸附容量为25.7 mg·g^-1；拟二级动力学方程能较好地描述CEB-La对F^-的吸附动力学过程；CEB-La吸附饱和后，经NaOH溶液处理后再与镧离子螯合，可有效再生；共存阴离子特别是CO ^{2   -}₃       和HCO^-₃对CEB-La的除氟性能有不利影响。动态吸附实验结果表明：进水流量3 ml·min^-1时，CEB-La适于处理F^-浓度2～15 mg·L^-1的含氟水；利用Thomas模型可较好地描述CEB-La对F^-的动态吸附特征，动态饱和吸附容量为3.67 mg·g^-1。因此，CEB-La的除氟性能优越，再生方法简单，使用成本较低，具有较好的应用前景。