Nano-Hydroxyapatite Encapsulated inside an Anion Exchanger for Efficient Defluoridation of Neutral and Weakly Alkaline Water,ACS ES&T Engineering

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Nano-Hydroxyapatite Encapsulated inside an Anion Exchanger for Efficient Defluoridation of Neutral and Weakly Alkaline Water
ACS ES&T Engineering ( IF 7.4 ) Pub Date : 2020-10-01 , DOI: 10.1021/acsestengg.0c00005
Hui Qiu ₁ , Meichen Ye ₁ , Ming-Dao Zhang ₁ , Xiaolin Zhang ₂ , Yuan Zhao ₁ , Jianghua Yu ₁

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The efficient removal of fluoride from weakly alkaline groundwater still remains a great challenge, owing to the high hydration energy of fluoride. Herein, we conducted in situ precipitation of nanosized hydroxyapatite (nano-HAP) inside a polystyrene anion exchanger D201. The resultant HAP@D201 exhibited almost constant defluoridation efficiency in a wide pH range, especially much higher F^– removal efficiency under neutral and weakly alkaline conditions (pH 7–10) than currently available materials. XPS, XRD, and ¹⁹F MAS NMR analysis demonstrated that the pH-insensitive defluoridation performance of HAP@D201 was mainly attributed to lattice replacement between the hydroxide ions inside nano-HAP and fluoride in solution, owing to the similar ionic radius of fluoride (1.33 Å) with the hydroxide ion (1.37 Å). The ubiquitous anions like sulfate, chloride, nitrate, and bicarbonate posed negligible effects on the defluoridation performance of HAP@D201, because of the larger ionic radius than for hydroxide ion. Moreover, the HAP@D201 column was capable of successively producing 160, 108, and 92 bed volume (BV) clean water ([F] < 1.5 mg/L) from synthetic water at pH 5.0, 8.0, and 9.0, respectively, 2.5 times more than commercial defluorination material. After adsorption, the exhausted HAP@D201 could be fully refreshed by alkaline solution and retained constant defluoridation efficiency in 10 cyclic column adsorption-regeneration runs.

中文翻译：

纳米羟基磷灰石包裹在阴离子交换剂中，用于中性和弱碱性水的有效脱氟

由于氟化物的高水合能，从弱碱性地下水中有效去除氟化物仍然是一个巨大的挑战。本文中，我们在聚苯乙烯阴离子交换剂D201内进行了纳米羟基磷灰石（nano-HAP）的原位沉淀。将所得HAP @ D201在宽的pH范围内表现出几乎恒定脱氟效率，尤其是高得多的˚F ^-比目前可得的材料中性和弱碱性条件（pH 7-10）下去除效率。XPS，XRD和¹⁹F MAS NMR分析表明，HAP @ D201对pH值不敏感的脱氟性能主要归因于纳米HAP内的氢氧根离子与溶液中的氟之间的晶格置换，这是因为氟的离子半径（1.33Å）与氢氧化物相似离子（1.37Å）。由于离子半径比氢氧根离子大，因此硫酸根，氯离子，硝酸根和碳酸氢根等普遍存在的阴离子对HAP @ D201的脱氟性能影响可忽略不计。此外，HAP @ D201色谱柱能够分别从pH 5.0、8.0和9.0、2.5的合成水中连续生产160、108和92床体积（BV）的净水（[F] <1.5 mg / L）。是商用脱氟材料的三倍。吸附后

更新日期：2020-10-01

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