Phosphate removal performances of layered double hydroxides (LDH) embedded polyvinyl alcohol / lanthanum alginate hydrogels
Phosphate removal performances of layered double hydroxides (LDH) embedded polyvinyl alcohol / lanthanum alginate hydrogels
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DOI：
10.1016/j.cej.2021.132754
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发表时间：
2021-10-07
影响因子：
15.1
通讯作者：
Liu, Qian
中科院分区：
文献类型：
--
作者：
Feng, Lihua;Zhang, Qian;Liu, Qian
镧改性化合物和层状双氢氧化物（LDH）是很有前途的磷酸盐吸附剂。然而，纳米级LDH的分离具有挑战性，并且常规的固定化方法削弱了吸附性能。利用金属离子与磷酸盐之间的亲和性，采用原位交联法制备了聚乙烯醇/金属离子海藻酸钠（PS-M-LDH）水凝胶小球，并将其与不同的金属离子（M）溶液进行交联，以提高聚乙烯醇/金属离子海藻酸钠水凝胶小球的除磷效果。通过筛选，La交联的PS-M-LDH（PS-La-LDH）具有较好的磷酸盐吸附性能。进一步研究了PS-La-LDH水凝胶对磷酸盐的吸附行为。结果表明，PS-La-LDH水凝胶对磷酸根的吸附符合准二级动力学模型和Freundlich模型。PS-La-LDH的最大吸附容量为34.2mg P/g，折合LDH当量为91.2mg P/g LDH，是纯LDH粉末（58.0mg P/g LDH）的1.6倍。PS-La-LDH对磷酸盐的去除在类似于8的pH 3的宽范围内表现良好。PS-La-LDH对磷酸根具有选择性吸附，且存在竞争性阴离子（Cl-、NO3-和SO 42-）。当SO 42-浓度增加到2882 mg/L时，PS-La-LDH水凝胶对磷酸盐的吸附量仅下降了16.57%。SEM、XRD、FTIR和XPS结果表明，静电作用、配体交换和离子交换共同促进了磷酸盐的吸附。
Lanthanum modified compounds and Layered double hydroxides (LDH) are promising adsorbents for phosphate. However, the nano-scale LDH is challenging to separate, and conventional immobilization methods weaken the adsorption performance. With the affinity between metal ions and phosphate, polyvinyl alcohol/metal ions sodium alginate (PS-M-LDH) hydrogel beads for the improvement of phosphate removal were prepared by in situ crosslinking with different metal ion (M) solutions. Through screening, the PS-M-LDH crosslinked by La (PS-La-LDH) has the preferable phosphate adsorption performance. The phosphate adsorption behavior of PS-La-LDH hydrogel was further investigated. Results showed that the adsorption process of phosphate by PS-La-LDH hydrogel was in accordance with the pseudo-second-order kinetic model and Freundlich model. The maximum experimental adsorption capacity of PS-La-LDH was 34.2 mg P/g, converting to an equivalent LDH of 91.2 mg P/g LDH, which was 1.6 times of pristine LDH powder (58.0 mg P/g LDH). The removal of phosphate by PS-La-LDH performed well at a wide range of pH 3 similar to 8. PS-La-LDH showed selective adsorption to phosphate with the existence of competing anions (Cl-, NO3-, and SO42-). The phosphate adsorption by PS-La-LDH hydrogel only reduced 16.57 % when the concentration of SO42- was increased to 2882 mg/L. SEM, XRD, FTIR, and XPS results showed that the electrostatic interaction, ligand exchange, and ion exchange jointly facilitated the adsorption of phosphate.