焙烧态镁铝铁类水滑石对磷酸根离子的吸附

Adsorption of phosphate by calcined Mg-Al-Fe layered double hydroxides

用共沉淀法制备了镁铝铁三元类水滑石(LDH),在不同温度下对其焙烧4 h,得到焙烧态类水滑石(CLDH).采用XRD、FT-IR对材料进行分析,研究其对水中磷酸根的吸附性能和机制.结果表明,铁的掺杂量过大会破坏类水滑石的层状结构,且随着铁含量的增大,类水滑石对磷酸根的吸附量逐渐减小.当Mg/Al/Fe物质的量之比为2∶0.9∶0.1,在300℃下焙烧时,CLDH吸附磷酸根能力最好,吸附容量约27.03 mg.g-1,为焙烧前的1.32倍.在pH 4—11范围内,在竞争离子存在的条件下,CLDH-0.1-300都能表现出较好的吸附性能,对实际废水中的磷也有较强的吸附能力.CLDH-0.1-300对磷酸根的吸附符合二级反应动力学模型,吸附等温线符合Langmuir等温式.用浓度为0.5 mol.L-1的NaOH溶液可以对吸附磷酸根后的类水滑石CLDH-0.1-300实现解吸再生,"吸附-再生-再吸附"循环3次后吸附容量仍接近初始值的60%.

A series of MgAlFe layered double hydroxides（LDH）were synthesized by a coprecipitation method and were calcined at different temperatures for 4 h to prepare calcined layered double hydroxides（CLDH）.The samples were characterized by XRD and FT-IR to investigate the performance and mechanism of phosphate adsorption.The results showed that the layered structure was destroyed with excessive iron and increased Fe loading led to the decrease of the sorption efficiency.CLDH-0.1-300 with Mg/Al/Fe molar ratio of 2 ∶ 0.9 ∶ 0.1 and calcined at 300 ℃ had the highest phosphate adsorption capacity.The maximum sorption capacity reached 27.03 mg · g-1,which was 32% higher than the uncalcined material.CLDH-0.1-300 showed excellent performance in phosphate adsorption from the solution with co-existing anions in a pH range of 4—11.Moreover,CLDH-0.1-300 exhibited remarkable adsorption capacity for phosphate in wastewater samples.The adsorption kinetics and the adsorption isotherm followed pseudo second-order model and the Langmuir model respectively.The adsorbed phosphate was desorbed from CLDH-0.1-300 effectively with 0.5 mol · L-1 NaOH solution to regenerate adsorbent and the adsorption capacity was still close to 60% of the initial value after three cycles of the adsorption-regeneration-adsorption.