State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
Water Res. 2016 Oct 1;102:109-116. doi: 10.1016/j.watres.2016.06.030. Epub 2016 Jun 15.
Water decontamination from fluoride is still a challenging task of global concern. Recently, Al-based layered double hydroxides (LDHs) have been extensively studied for specific fluoride adsorption from water. Unfortunately, they cannot be readily applied in scaled-up application due to their ultrafine particles as well as the regeneration issues caused by their poor stability at alkaline pHs. Here, we developed a novel (LDH)-based hybrid adsorbent, i.e., LALDH-201, by impregnating nanocrystalline Li/Al LDHs (LADLH) inside a commercial polystyrene anion exchanger D201. TEM image and XRD spectra of the resultant nanocomposite confirmed that the LDHs particles were nanosized inside the pores of D201 of highly crystalline nature and well-ordered layer structure. After impregnation, the chemical and mechanical stability of LALDH were significantly improved against pH variation, facilitating its application at a wide pH range (3.5-12). Fluoride adsorption onto LALDH-201 was compared to D201 and activated alumina, evidencing the preferable removal fluoride of LALDH-201. Fluoride adsorption onto LALDH-201 followed pseudo-second-order model, with the maximum capacity (62.5 mg/g from the Sips model) much higher than the other two adsorbents. Fixed-bed adsorption run indicated the qualified treatable volume of the fluoride contaminated groundwater (4.1 mg/L initially) with LALDH-201 was about 11 times as much as with the anion exchanger D201 when the breakthrough point was set as 1.5 mg/L. The capacity of LALDH-201 could be effectively refreshed for continuous column operation without observable loss by using the mixed solution of 0.01 M NaOH + 1 M NaCl. The above results suggested that the hybrid adsorbent LALDH-201 is very promising for water defluoridation in scaled-up application.
从氟化物中进行水的净化仍然是一个具有全球关注的挑战性任务。最近，基于铝的层状双氢氧化物（LDHs）已被广泛研究用于从水中特异性吸附氟化物。不幸的是，由于它们的超细微粒以及在碱性 pH 值下稳定性差而导致的再生问题，它们不能轻易地应用于规模化应用。在这里，我们通过在商业聚苯乙烯阴离子交换剂 D201 内部浸渍纳米晶 Li/Al LDHs（LADLH），开发了一种新型（LDH）基混合吸附剂，即 LALDH-201。所得纳米复合材料的 TEM 图像和 XRD 谱图证实，LDHs 颗粒在 D201 的孔内为纳米尺寸，具有高度结晶的性质和有序的层状结构。浸渍后，LALDH 的化学和机械稳定性显著提高，能够在较宽的 pH 范围（3.5-12）下应用。将氟化物吸附到 LALDH-201 上与 D201 和活性氧化铝进行了比较，证明了 LALDH-201 具有更好的去除氟化物的能力。LALDH-201 上的氟化物吸附遵循准二级模型，最大容量（根据 Sips 模型为 62.5 mg/g）远高于其他两种吸附剂。固定床吸附运行表明，当将穿透点设置为 1.5 mg/L 时，LALDH-201 对初始氟浓度为 4.1 mg/L 的受氟污染地下水的可处理体积是阴离子交换剂 D201 的 11 倍。通过使用 0.01 M NaOH+1 M NaCl 的混合溶液，可以有效地刷新 LALDH-201 的容量，以进行连续柱操作，而不会观察到明显的损失。上述结果表明，混合吸附剂 LALDH-201 非常有希望在规模化应用中进行水除氟。
