Highly efficient Al(OH)3/HAp composite adsorbent for the removal of fluoride from drinking water: batch and column studies

IF 5.7 3区环境科学与生态学 Q1 WATER RESOURCES

Applied Water Science Pub Date : 2025-07-05 DOI:10.1007/s13201-025-02467-5

Opoka William, Beteley Tekola Meshesha, Muhajir Mussa, Getachew Dagnew Gebreeyessus, Feleke Zewge

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Abstract

Excess fluoride in water is a significant public health concern, causing illnesses such as arthritis, dental fluorosis and skeletal fluorosis. Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) has shown a promise in fluoride removal through demineralization during which fluoride ions are effectively replaced by hydroxide ions (OH⁻). However, performance issues with applying hydroxyapatite (HAp) remain a challenge. This study assessed the efficacy of aluminum hydroxide/hydroxyapatite (Al(OH)₃/HAp) composite for fluoride removal from drinking water through batch and column experiments. The composite’s functional groups, crystalline phases, surface area, and the point of zero charge (pzc) were characterized, and its performance was evaluated in both batch and continuous experiments. During batch experiments, a 30% Al (OH)₃/HAp ratio exhibited an adsorption capacity of 2.30 mg/g with a fluoride removal efficiency of 92.02%. Kinetic analysis indicated that fluoride adsorption followed a pseudo-second-order model, suggesting chemisorption, while the Redlich–Peterson isotherm confirmed heterogeneous adsorption behavior. Among the tested competing anions, the presence of carbonate ions had the most adverse impact on fluoride removal efficiency. Column experiments using simulated water containing fluoride, bicarbonate and carbonates further demonstrated that an adsorption capacity of 1.28 mg/g was obtained at 15 mL/min flow rate, 10 cm bed depth, and 10 mg/L initial fluoride concentration, with the Clark model best describing the breakthrough data. Breakthrough time decreased with increasing flow rate and initial fluoride concentration but improved with greater bed depth. This study revealed Al(OH)₃/HAp as a cost-effective, efficient adsorbent for fluoride removal, addressing critical challenges in water treatment and providing insights into the adsorption behavior and mechanism of Al(OH)₃/HAp composite for fluoride removal.

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高效Al(OH)3/HAp复合吸附剂去除饮用水中的氟化物：批量和柱式研究

水中过量的氟化物是一个重大的公共卫生问题，会导致关节炎、氟牙症和氟骨症等疾病。羟基磷灰石(Ca10（PO4)6(OH)2）在脱矿过程中氟离子被氢氧根离子（OH−）有效取代，在除氟方面显示出前景。然而，应用羟基磷灰石（HAp）的性能问题仍然是一个挑战。通过批量和柱形实验，评价了氢氧化铝/羟基磷灰石（Al(OH)3/HAp）复合材料去除饮用水中氟化物的效果。表征了复合材料的官能团、晶相、比表面积和零电荷点（pzc），并在间歇和连续实验中对其性能进行了评价。在批量实验中，当Al (OH)3/HAp比为30%时，吸附量为2.30 mg/g，除氟效率为92.02%。动力学分析表明，氟的吸附符合准二级模型，表明是化学吸附，而Redlich-Peterson等温线则证实了非均相吸附行为。在测试的竞争阴离子中，碳酸盐离子的存在对除氟效率的影响最大。采用含氟、碳酸氢盐和碳酸盐模拟水的柱实验进一步表明，在15 mL/min流速、10 cm床深、10 mg/L初始氟浓度下，吸附量为1.28 mg/g， Clark模型最能描述突破数据。突破时间随流量和初始氟浓度的增大而减小，随床层深度的增大而增大。本研究揭示了Al(OH)3/HAp是一种经济高效的除氟吸附剂，解决了水处理中的关键挑战，并为Al(OH)3/HAp复合材料的除氟行为和机理提供了见解。

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