ABSTRACT

In this paper, the effect of different crystal forms of Al₂O₃ on fluoride removal was studied. All crystal forms of Al₂O₃ were based on the same boehmite precursor and were obtained using a hydrothermal and calcination method. γ-Al₂O₃ had higher fluoride removal performance (52.15 mg/g) compared with θ-Al₂O₃ and α-Al₂O₃. Density functional theory (DFT) calculations confirmed that fluoride removal was greatest for γ-Al₂O₃, followed by θ-Al₂O₃ and α-Al₂O₃, and γ-Al₂O₃ possessed the strongest fluoride binding energy (–3.93 eV). The typical adsorption behaviour was consistent with the Langmuir model and pseudo-second-order model, indicating chemical and monolayer adsorption. Different metal ions were used to modify γ-Al₂O₃, and lanthanum had the best effect. Lanthanum oxide was shown to play an important role in fluoride removal. The best La/Al doping ratio was 20 At%. The adsorption process of the composite was also consistent with chemical and monolayer adsorption. When the La/Al doping rate was 20%, the adsorption capacity reached 94.64 mg/g. Compared with γ-Al₂O₃ (1.39 × 10⁻⁷ m/s), the adsorption rate of 20La-Al₂O₃ was 3.93 × 10⁻⁷ m/s according to the mass transfer model. Furthermore, DFT was used to provide insight into the adsorption mechanism, which was mainly driven by electrostatic attraction and ion exchange.

摘要

本文研究了Al ₂ O ₃不同晶型对除氟效果的影响。Al ₂ O ₃的所有晶型均基于相同的勃姆石前体，并使用水热法和煅烧法获得。_{与θ-Al 2} O ₃和α-Al ₂ O _3相比， γ - Al ₂ O ₃具有更高的除氟性能（52.15 mg/g）。密度泛函理论 (DFT) 计算证实γ -Al ₂ O ₃的氟化物去除率最高，其次是 θ-Al ₂ O₃和α-Al ₂ O ₃和γ - Al ₂ O ₃具有最强的氟化物结合能（–3.93 eV）。典型的吸附行为与朗缪尔模型和准二级模型一致，表明化学吸附和单层吸附。使用不同的金属离子修饰γ - Al ₂ O ₃, 镧的效果最好。氧化镧被证明在氟化物去除中起重要作用。最佳的 La/Al 掺杂比为 20 At%。复合材料的吸附过程也与化学和单层吸附一致。当La/Al掺杂率为20%时，吸附量达到94.64 mg/g。 根据传质模型，与γ -Al ₂ O ₃ (1.39 × 10 ^-7  m/s)相比，20La-Al ₂ O ₃的吸附率为3.93 × 10 ^{-7 m/s。}此外，DFT 用于深入了解吸附机制，吸附机制主要由静电吸引和离子交换驱动。