Abstract Removal of selenium from caustic solution by adsorption with Ca Al Layered Double Hydroxides (Ca Al LDHs) was proposed. Ca Al LDHs with a hexagonal platelet structure were successfully synthetized by co-precipitation. 94% of Se(VI) was removed at 30 °C for 30 min with NaOH concentration of 1 mol·L−1 and adsorbent dosage of 40 g·L−1. Temperature played an important role in Se(VI) removal. At low temperature (30 °C–70 °C), Ca Al LDHs underwent an anion exchange with Se(VI) to form Ca4Al2O6SeO4(H2O)10, with the d-spacing expanding from 7.95 A to 10.15 A. When increasing temperature above 80 °C, Ca4Al2O6SeO4(H2O)10 began to decomposed to Ca3Al2O6(H2O)6 and Ca(OH)2, resulting in SeO42− into the liquor. Kinetic data were well fitted to pseudo-second-order model, indicating Se(VI) removal process was controlled by the chemisorption. The adsorption isotherms were in good agreement with Langmuir isotherm model, suggesting Se(VI) removal was a monolayer adsorption. The maximum adsorption capacity was calculated to be 138.76 mg·g−1 at 30 °C. Desorption and regeneration results indicated that Ca Al LDHs can be reused at least three times without significantly reducing its absorption capacity for Se(VI).

中文翻译：

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钙铝层状双氢氧化物吸附去除苛性碱溶液中的硒

摘要 提出了通过钙铝层状双氢氧化物 (Ca Al LDHs) 吸附去除苛性碱溶液中的硒。通过共沉淀成功合成了具有六边形片晶结构的 Ca Al LDHs。在NaOH浓度为1 mol·L-1和吸附剂用量为40 g·L-1的条件下，30°C下30分钟去除94%的Se(VI)。温度在 Se(VI) 去除中起重要作用。在低温 (30 °C–70 °C) 下，Ca Al LDHs 与 Se(VI) 进行阴离子交换，形成 Ca4Al2O6SeO4(H2O)10，d 间距从 7.95 A 扩大到 10.15 A。 80 °C，Ca4Al2O6SeO4(H2O)10 开始分解为 Ca3Al2O6(H2O)6 和 Ca(OH)2，导致 SeO42− 进入溶液。动力学数据很好地拟合了伪二阶模型，表明 Se(VI) 去除过程受化学吸附控制。吸附等温线与朗缪尔等温线模型非常吻合，表明 Se(VI) 去除是单层吸附。在 30 °C 下计算出的最大吸附容量为 138.76 mg·g-1。解吸和再生结果表明，Ca Al LDHs 可以重复使用至少 3 次，而不会显着降低其对 Se(VI) 的吸收能力。