Mechanistic insights into adsorption and reduction of hexavalent chromium from water using magnetic biochar composite: Key roles of Fe3O4 and persistent free radicals
Mechanistic insights into adsorption and reduction of hexavalent chromium from water using magnetic biochar composite: Key roles of Fe3O4 and persistent free radicals
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使用磁性生物炭复合材料吸附和还原水中六价铬的机理见解：Fe3O4 和持久自由基的关键作用
DOI：
10.1016/j.envpol.2018.08.093
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发表时间：
2018
影响因子：
8.9
通讯作者：
John C. Crittenden
中科院分区：
文献类型：
--
作者：
Delai Zhong;Yanrong Zhang;Linling Wang;Jing Chen;Yi Jiang;Daniel C.W. Tsang;Zezhou Zhao;Shupeng Ren;Zhenhua Liu;John C. Crittenden
磁性生物炭（MBC）已被用于去除水中的六价铬（Cr（VI）），但MBC中Fe 3 O 4和持久性自由基（PFR）在去除Cr（VI）中的作用研究较少。本文以固态FeSO 4和稻壳为原料，采用微波共热解法制备MBC，并将其用于去除水中的Cr（VI）。与稻壳生物炭（BC）相比，MBC对Cr（VI）的吸附和还原效率分别提高了3.2倍和11.7倍，因此MBC的Cr（VI）去除率（84.3%）和平衡吸附容量（8.35 mg g−1）均高于BC（26.5%和2.63 mg g−1）。多重表征结果表明，MBC的高Cr（VI）去除性能主要归因于多孔和石墨化MBC中活性Fe 3 O 4和碳中心PFR的存在。Fe 3 O 4不仅通过其Fe（II）和Fe（III）的八配位为Cr（VI）提供了活性化学吸附/还原位点，而且还促进了生成比碳中心PFR更活性的供电子碳中心PFR，从而还原Cr（VI）。Fe 3 O 4的存在还使MBC的BET表面积增加了36.7 m2 g − 1，孔体积增加了0.043 cm 2 g − 1，促进了Cr（VI）的去除。Fe_3 O_4和碳中心的PFR分别占总Cr（III）生成量的81.8%和18.2%。此外，初始溶液的pH值是负责确定的Cr（VI）的吸附和还原的相对意义。这项研究提供了新的见解铬（VI）去除水中的MBC的机制。
Magnetic biochar (MBC) has been used to remove hexavalent chromium (Cr(VI)) from water, but the roles of Fe3O4and persistent free radicals (PFRs) in MBC in Cr(VI) removal are still less investigated. In this work, the MBC synthesized by microwave co-pyrolysis of solid-state FeSO4and rice husk was employed to remove Cr(VI) from water. In comparison to the rice husk biochar (BC), the MBC exhibits the 3.2- and 11.7-fold higher adsorption and reduction efficiency of Cr(VI), resulting in the higher Cr(VI) removal efficiency (84.3%) and equilibrium adsorption capacity of MBC (8.35 mg g−1) than that (26.5% and 2.63 mg g−1) of BC. Multiple characterization results revealed that the high Cr(VI) removal performance of MBC was mainly attributed to the presence of active Fe3O4and carbon-centered PFRs in the porous and graphitic MBC. The Fe3O4not only provided active chemisorption/reduction sites for Cr(VI) via its Fe(II)octand Fe(III)octcoordination, but also facilitated the generation of more active electron donating carbon-centered PFRs than carbon-centered PFRs with an oxygen atom in the graphitic structure to reduce Cr(VI). The presence of Fe3O4also elevated 36.7 m2g−1of BET-surface area and 0.043 cm2g−1of pore volume of MBC, promoting the Cr(VI) removal. The Fe3O4and carbon-centered PFRs contributed to ∼81.8% and ∼18.2% of total Cr(III) generation, respectively. In addition, the initial solution pH was responsible for determining the relative significance of Cr(VI) adsorption and reduction. This study provides new insights into the mechanisms of Cr(VI) removal from water by the MBC.