Quantitative analysis on the redox conversion mechanism of Cr(VI) and As(III) by iron carbide based biochar composites
Quantitative analysis on the redox conversion mechanism of Cr(VI) and As(III) by iron carbide based biochar composites
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碳化铁基生物炭复合材料对 Cr(VI) 和 As(III) 氧化还原转化机理的定量分析
DOI：
10.1016/j.cej.2022.137417
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发表时间：
2022
影响因子：
15.1
通讯作者：
Rongliang Qiu
中科院分区：
文献类型：
--
作者：
Nan Zhao;Xiaofei Tan;Juan Xiong;Nan Chen;Jia Gao;Rui Wang;Xixiang Yang;Weihua Zhang;Weixian Zhang;Rongliang Qiu
·Fe促进了Cr（VI）和As（III）的氧化还原转化。Fe占Cr（VI）和As（III）去除量的18.9%~47.4%和98.1%~99.4%。·Cr（VI）被C-OH基团吸附，As（III）与γ-FeOOH键合。·Fe 0、Fe 2+、H和O基团对Cr（VI）的还原有促进作用。··OH、·O2 −、1 O2和Fe（OH）3是As（III）氧化的主要机制。铁基材料已被广泛应用于去除废水中的Cr（VI）和As（III），但对其去除机理和功能缺乏定量的了解。本研究制备了Fe含量分别为19.7%、24.0%和26.5%的三种碳化铁基生物炭复合材料（Fe3C@BC-A、Fe3C@BC-B和Fe3C@BC-C），用于去除Cr（VI）和As（III）。Cr（VI）和As（III）的去除率随着Fe投加量的增加而增加。Fe含量最高的Fe3C@BC-C对Cr（VI）和As（III）的还原和氧化能力最强。X射线吸收近边结构分析表明，Cr（VI）还原生成FeCr2O4、（CrxFe1-x）（OH）3、Cr3+、Cr（OH）3和Cr2O3，而AsO43-是As（III）的氧化产物。酸洗实验结果表明，Fe分别占Cr（VI）和As（III）去除量的18.9%~47.4%和98.1%~99.4%。傅里叶变换红外光谱和X射线光电子能谱（XPS）分析表明，Cr（VI）被吸附在生物炭的OH基团上，而As（III）则被吸附在反应后的Fe3C颗粒的γ-FeOOH上.淬灭实验、电子自旋共振分析和XPS表明，Fe 0、Fe 2+、原子H和含O基团对Cr（VI）的还原起作用，而·OH、·O2 −、1 O2和Fe（OH）3对As（III）的氧化起作用。该定量机理有助于更好地理解Fe/C复合材料去除Cr（VI）和As（III）的机理，其结果可指导Fe/C复合材料去除氧化还原活性污染物的进一步制备和应用。
• Fe enhanced the redox conversion of Cr(VI) and As(III). • Fe accounted for 18.9%–47.4% and 98.1%–99.4% of the removed Cr(VI) and As(III). • Cr(VI) was adsorbed by the C-OH groups, and As(III) was bonded to γ-FeOOH. • Fe 0 , Fe 2+ , H, and O-containing groups contributed to the reduction of Cr(VI). • • OH, • O 2 − , 1 O 2 , and Fe(OH) 3 were responsible for the oxidation of As(III). Fe-based materials have been widely used for removing Cr(VI) and As(III) in wastewater, however, the quantitative understanding of their removal mechanism and functions of Fe is lacking. In this study, three types of iron carbide based biochar composites (Fe 3 C@BC-A, Fe 3 C@BC-B, and Fe 3 C@BC-C) with different Fe dosages of 19.7%, 24.0%, and 26.5%, respectively, were prepared for Cr(VI) and As(III) removal. The removal of Cr(VI) and As(III) was found to increase as the Fe dosage increased. Fe 3 C@BC-C with the highest Fe content showed the greatest reduction and oxidation capacities for Cr(VI) and As(III). X-ray absorption near-edge structure analysis indicated that the reduction of Cr(VI) afforded FeCr 2 O 4 , (Cr x Fe 1-x )(OH) 3 , Cr 3+ , Cr(OH) 3 , and Cr 2 O 3 , whereas AsO 4 3- was the oxidation product of As(III). Results of a pickling experiment revealed that Fe accounted for 18.9%–47.4% and 98.1%–99.4% of the removed Cr(VI) and As(III), respectively. The adsorption mechanism revealed by Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy (XPS) suggested that Cr(VI) was adsorbed by the OH groups of biochar, whereas As(III) was bonded to γ-FeOOH of the reacted Fe 3 C particles. The quenching experiment, electron spin resonance analysis, and XPS suggested that Fe 0 , Fe 2+ , atomic H, and O-containing groups contributed to the reduction of Cr(VI), while • OH, • O 2 − , 1 O 2 , and Fe(OH) 3 were responsible for the oxidation of As(III). The quantitative mechanisms contributed to an improved understanding for the removal of Cr(VI) and As(III) by Fe/C composites, and the results may guide further preparation and application of Fe/C composites for redox-active contaminants removal.