Jin Cheng, Liu Huimin, Kong Xianggui, Yan Hong, Lei Xiaodong
State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, PO Box 98, Beijing 100029, China.
Dalton Trans. 2018 Feb 27;47(9):3093-3101. doi: 10.1039/c7dt03583g.
Phytate intercalated MgAl layered double hydroxide (MgAl-LDH) was prepared by an anion exchange method with the precursor NO containing MgAl-LDH. The final as-synthesized product [MgAl(OH)] (phytateNa) (NO)·mHO (phytate-LDH) has highly selective adsorption ability for some metal ions and can be used to enrich rare earth metal ions in mixed solution, such as Pr and Ce from a mixed solution of them with Pb and Co. At first, phytate-LDH has good adsorption performance for these ions in single metal ion solutions. At low concentration (below 10 mg L), all the capture rates of the four metal ions were more than 97%, for highly toxic Pb it was even up to nearly 100%, and a high capture rate (99.87%) was maintained for Pb at a high concentration (100 mg L). When all the four metal ions are co-existing in aqueous solution, the selectivity order is Pb ≫ Pr ≈ Ce > Co. In a solution containing mixtures of the three metal ions of Pr, Ce, and Co, the selectivity order is Pr ≈ Ce ≫ Co, and in a solution containing mixtures of Pr with Co and Ce with Co, the selectivity orders are Pr ≫ Co and Ce ≫ Co, respectively. The high selectivity and adsorption capacities for Pb, Co, Pr, and Ce result in the efficient removal of Pb and enrichment of the rare earth metal ions Pr and Ce by phytate-LDH. Based on the elemental analysis, it is found that the difference of the adsorption capacities is mainly due to the different coordination number of them with phytate-LDH. With molecular simulation, we believe that the adsorption selectivity is due to the difference of the binding energy between the metal ion and phytate-LDH. Therefore, the phytate-LDH is promising for the enrichment and/or purification of the rare earth metal ions and removal of toxic metal ions from waste water.
采用阴离子交换法，以前驱体含硝酸根的MgAl层状双氢氧化物制备了植酸盐插层MgAl层状双氢氧化物（MgAl-LDH）。最终合成产物[MgAl(OH)] (植酸钠)(硝酸根)·mH₂O（植酸盐-LDH）对某些金属离子具有高度选择性吸附能力，可用于富集混合溶液中的稀土金属离子，如从Pr、Ce与Pb、Co的混合溶液中富集Pr和Ce。首先，植酸盐-LDH在单一金属离子溶液中对这些离子具有良好的吸附性能。在低浓度（低于10 mg/L）时，四种金属离子的捕获率均超过97%，对于剧毒的Pb甚至高达近100%，在高浓度（100 mg/L）时Pb的捕获率仍保持在99.87%。当四种金属离子同时存在于水溶液中时，选择性顺序为Pb ≫ Pr ≈ Ce > Co。在含有Pr、Ce和Co三种金属离子混合物的溶液中，选择性顺序为Pr ≈ Ce ≫ Co，在含有Pr与Co以及Ce与Co混合物的溶液中，选择性顺序分别为Pr ≫ Co和Ce ≫ Co。植酸盐-LDH对Pb、Co、Pr和Ce的高选择性和吸附容量导致其能有效去除Pb并富集稀土金属离子Pr和Ce。基于元素分析，发现吸附容量的差异主要是由于它们与植酸盐-LDH的配位数不同。通过分子模拟，我们认为吸附选择性是由于金属离子与植酸盐-LDH之间结合能的差异。因此，植酸盐-LDH在从废水中富集和/或纯化稀土金属离子以及去除有毒金属离子方面具有广阔前景。
