Environmental Geochemistry Group, Department of Geology, Panjab University, Chandigarh, India.
Water Environ Res. 2022 Nov;94(11):e10804. doi: 10.1002/wer.10804.
Fluoride deficiency and toxicity severely affect a large population globally. Hence, a low-cost geosorbent is in demand to overcome fluorosis hazards where in situ retardation is prioritized over pilot-scale waste water treatment. This study reports the fluoride removal potential of MgFe-type layered double hydroxide (HT-LDH) and its calcined form at 500 and 800°C for their usability for treatment of polluted streams, ponds, wells, and hot spring water. Rapid uptake with >33% removal in 24 h was found by the adsorptive method, whereas the co-precipitation process removed >16 mg/L (>83%) in 1 h. The efficiency was further enhanced upon calcination at 500°C with >95% removal up to five times regeneration, unlike that at 800°C. It was demonstrated that multilayer sorption onto heterogeneous surface sites is majorly controlled by surface adsorptive and ion exchange mechanisms. Acidic pH, low aqueous , and temperature >25°C favored greater uptake, whereas competitive anions slightly enhanced its potential in the order in adsorptive removal. In the co-precipitation process, competing anions slightly hindered retention, whereas high temperature and low aqueous led to greater retention. No F-bearing solid phases were evidenced upon its retention, except lowering the HT-LDH crystallinity and rearrangement of surface functional groups. The fluoride contents of natural water were lowered drastically up to 77% in 60 min upon precipitation of HT-LDH by maintaining alkalinity and a di-/trivalent cationic ratio of 2.0. PRACTITIONER POINTS: F^- uptake is rapid on heterogeneous surface sites with multilayer sorption mechanism Greater F^- removed by coprecipitation technique compared with adsorptive pathway Acidic medium and temperature >25°C favor greater F^- retention NO_3^-+PO_l4^(3-) slightly enhanced F^- uptake by adsorption but lowered in coprecipitation Formation of LDH from natural waters lowered F^- content up to <77.
氟化物缺乏和毒性严重影响全球大量人口。因此，需要一种低成本的地球吸附剂来克服氟中毒危害，优先考虑原位阻滞而不是中试规模的废水处理。本研究报告了 MgFe 型层状双氢氧化物（HT-LDH）及其在 500 和 800°C 下煅烧形式的氟去除潜力，以评估其在处理受污染溪流、池塘、水井和温泉水方面的可用性。吸附法发现，在 24 小时内快速吸收可去除超过 33%的氟，而共沉淀法在 1 小时内可去除超过 16mg/L（>83%）。在 500°C 下煅烧时，效率进一步提高，可重复使用五次，去除率超过 95%，而在 800°C 下则不然。结果表明，多层吸附主要受表面吸附和离子交换机制控制。酸性 pH 值、低水 、温度 >25°C 有利于更大的吸收，而竞争阴离子在吸附去除中按 的顺序略微提高了其潜力。在共沉淀过程中，竞争阴离子略微阻碍了 的保留，而高温和低水 导致 保留量增加。除了降低 HT-LDH 结晶度和表面官能团重排外，没有证据表明在保留过程中有含氟固体相。通过保持碱度和二价/三价阳离子比为 2.0，将 HT-LDH 沉淀到天然水中，可将氟含量在 60 分钟内急剧降低至 77%。
