Graduate School of Environmental Studies, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan.
Graduate School of Environmental Studies, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan.
J Environ Manage. 2015 Jun 1;156:252-6. doi: 10.1016/j.jenvman.2015.03.043. Epub 2015 Apr 11.
Mg-Al oxide obtained by the thermal decomposition of Mg-Al layered double hydroxide (LDH) intercalated with CO3(2-) (CO3·Mg-Al LDH) was found to take up fluoride from aqueous solution. Fluoride was removed by rehydration of Mg-Al oxide accompanied by combination with F(-). Using five times the stoichiometric quantity of Mg-Al oxide, the residual concentration of F was decreased from 100 to 6.3 mg/L in 480 min, which was below the effluent standard in Japan (8 mg/L). Removal of F(-) can be represented by pseudo-second-order reaction kinetics. The apparent rate constants at 10 °C, 30 °C, and 60 °C were 2.3 × 10(-3), 2.2 × 10(-2), and 2.5 × 10(-1) g mmol(-1) min(-1), respectively. The apparent activation energy was 73.3 kJ mol(-1). The rate-determining step for F removal by Mg-Al oxide was consistent with chemical adsorption involving intercalation of F(-) into the reconstructed Mg-Al LDH due to electrostatic attraction. The adsorption of F by Mg-Al oxide follows a Langmuir-type adsorption. The values of the maximum adsorption and the equilibrium adsorption constant were 3.0 mmol g(-1) and 1.1 × 10(3), respectively, for Mg-Al oxide. The F(-) in the F·Mg-Al LDH thus produced was found to be anion-exchanged with CO3(2-) in solution. The Mg-Al oxide after regeneration treatment had excellent properties for removal of F in aqueous solution. In conclusion, the results of this study indicated that Mg-Al oxide has potential for use in recycling to remove F in aqueous solution.
由 CO3(2-)（CO3·Mg-Al LDH）插层的 Mg-Al 层状双氢氧化物（LDH）热分解得到的 Mg-Al 氧化物被发现能够从水溶液中吸收氟化物。通过 Mg-Al 氧化物的再水合以及与 F(-)结合，氟化物被去除。使用五倍于化学计量的 Mg-Al 氧化物，在 480 分钟内，残余氟浓度从 100 降至 6.3 mg/L，低于日本的排放标准（8 mg/L）。F(-)的去除可以用伪二级反应动力学来表示。在 10°C、30°C 和 60°C 下的表观速率常数分别为 2.3×10(-3)、2.2×10(-2)和 2.5×10(-1) g mmol(-1) min(-1)。表观活化能为 73.3 kJ mol(-1)。Mg-Al 氧化物去除 F 的速率决定步骤与化学吸附一致，涉及 F(-)通过静电吸引插入重构的 Mg-Al LDH。Mg-Al 氧化物对 F 的吸附遵循 Langmuir 型吸附。Mg-Al 氧化物的最大吸附量和平衡吸附常数分别为 3.0 mmol g(-1)和 1.1×10(3)。因此，在 F·Mg-Al LDH 中吸附的 F(-)被发现与溶液中的 CO3(2-)发生阴离子交换。经过再生处理的 Mg-Al 氧化物在水溶液中去除 F 具有优异的性能。总之，本研究结果表明，Mg-Al 氧化物在水溶液中去除 F 的回收利用中具有潜力。
