Magnetically Double-Shelled Layered Double Oxide (LDO)/LDO/γ-Fe2O3 Composite for Highly Efficient Removal of Congo Red and Chromium(VI)
Magnetically Double-Shelled Layered Double Oxide (LDO)/LDO/γ-Fe2O3 Composite for Highly Efficient Removal of Congo Red and Chromium(VI)
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DOI：
10.1021/acs.iecr.1c04699
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发表时间：
2022-03
期刊：
影响因子：
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通讯作者：
Zhu Wei;Yejia Zhang;Ting Fan;Yanjun Lin;Hui Zhang
中科院分区：
文献类型：
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作者：
Zhu Wei;Yejia Zhang;Ting Fan;Yanjun Lin;Hui Zhang
采用低成本的两步共沉淀法和适当的煅烧工艺制备了新型双壳结构的核壳型磁性复合材料MgFexAl-LDO/LDO/γ-Fe 2 O3（x= 0，0.1和0.5）。该复合材料由两层LDO纳米片（约80 × 10 nm）在球形γ-Fe_2O_3表面上垂直接力生长而成。 LDO壳层的厚度约为220 ~ 260 nm，提供了大量的有效吸附位点和许多由相邻LDO纳米片组成的开放通道。所有复合材料对刚果红（CR）和Cr（VI）均表现出良好的吸附性能。其中，MgAl-LDO/LDO/γ-Fe 2 O3的吸附容量最大（qmax= 123.4 mg g-1），这是由于具有大Brunauer-Emmett-Teller面积的双壳形态（219 m2 g-1）、正LDO壳层与Cr（VI）含氧阴离子之间的静电吸引以及吸附耦合还原，吸附的Cr（VI）被水合金属离子的羟基还原为Cr（III），并通过“记忆效应”重构为层状双氢氧化物层。MgAl-LDO/LDO/γ-Fe 2 O3和MgFe 0.1Al-LDO/LDO/γ-Fe 2 O3对CR的吸附效率非常高，qmax值非常接近（分别为3980和3832 mg g-1）。前者归因于其大的SBET和强的LDO壳层与CR阴离子的静电相互作用，而后者（99 m2 g-1）仍归因于少量Fe ~（3+）物种对CR的络合作用。MgAl-LDO/LDO/γ-Fe_2O_3复合材料经外加磁铁吸附后，可方便地从水溶液中分离回收。第四循环效率高达84%，具有良好的应用前景。
Novel double-shelled core-shell-type magnetic composites MgFexAl-LDO/LDO/γ-Fe2O3(x= 0, 0.1, and 0.5) were synthesized by a cost-effective two-step coprecipitation method followed by proper calcination. The composites are constructed by two layers of LDO nanosheets (∼80 × 10 nm) which shows vertically oriented relay growth on the surface of spherical γ-Fe2O3. The thickness of LDO shells isca.220 ∼ 260 nm, providing a large number of effective adsorption sites and numerous open channels composed of adjacent LDO nanosheets. All the composites show excellent adsorption capacities for Congo Red (CR) and Cr(VI). Especially, the MgAl-LDO/LDO/γ-Fe2O3exhibits the maximum adsorption capacity (qmax= 123.4 mg g–1) for Cr(VI), which is due to the double-shelled morphology with a large Brunauer–Emmett–Teller area (219 m2g–1), the electrostatic attraction between the positive LDO shells and Cr(VI) oxyanions, and the adsorption-coupled reduction, with the adsorbed Cr(VI) anion reduced to Cr(III) by hydroxyl groups of the hydrated metal ions and reconstructed into layer double hydroxide layers by the “memory effect”. The MgAl-LDO/LDO/γ-Fe2O3and MgFe0.1Al-LDO/LDO/γ-Fe2O3show extraordinary adsorption efficiency for CR with very closeqmaxvalues (3980 and 3832 mg g–1, respectively). The former can be attributed to its large SBETand strong LDO shells─CR anion electrostatic interaction, while the latter (99 m2g–1) can still be ascribed to the complexing function of a small amount of Fe3+species to CR. The MgAl-LDO/LDO/γ-Fe2O3composite can be conveniently separated and recovered from the aqueous solution after adsorption by an external magnet. The fourth cycle efficiency of up to 84% implies a promising application prospect.