CHEMICAL GEOLOGY
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2022
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IF 4.685
Liyan Deng,Fu Liu,Zecong Ding,Yuzhen Liang,Zhenqing Shi
Fe(II)-bearing clay minerals are abundant in soils and are critical to control the fate of the highly toxic hexavalent chromium (Cr(VI)). Even though the reduction of Cr(VI) by Fe(II)-bearing clay minerals has been extensively studied, the effect of the commonly co-existing natural organic matter (NOM) on this process is poorly understood. This study aimed to understand the kinetics of Cr(VI) reduction by a typical Fe(II)-bearing clay mineral (i.e., reduced nontronite (rNAu-2)) in the presence of Suwannee River NOM and to unveil the possible mechanisms. Cr(VI) reduction experiments were conducted with different NOM concentrations in a range of 0 to 100 mg C L −1 under circumneutral pH. The time-course aqueous-phase measurements and solid-phase characterizations were performed with a combination of wet chemical methods, transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses. The results demonstrated that NOM inhibited Cr(VI) reduction overall, mainly due to the decrease of Cr(VI) sorption on rNAu-2 by mineral-bound NOM. Besides the predominant solid Cr(III) species, soluble and mobile Cr(III) complexes were formed during reduction. Interestingly, the reduction rate ( k ) decreased with the increase of NOM concentration from 0 to 20 mg C L −1 , but kept increasing when the concentration of NOM increased from 30 to 100 mg C L −1 . The contrary pattern is due to the increasing promotion effects that offset the inhibitory effect caused by competitive sorption between Cr(VI) and NOM. The promotion effects may include weakening the mineral passivation by forming stable aqueous NOM-Cr(III) complexes, accelerating the electron transfer rate by dissolving rNAu-2, and donating electrons through NOM-Fe(II/III) complexes and/or NOM-Cr(V) complexes. This study extends our knowledge of Cr(VI) reduction by clay minerals in organic matter-rich soils and sediments and has important implication for understanding the transport and long-term behavior of Cr in the environment.
研究领域:
环境科学
·
土壤学
✓ 已验证
DOI
高影响因子
JOURNAL OF ENVIRONMENTAL MANAGEMENT
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2021
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IF 6.789
Zixuan Zhang,Jingfang Li,Yunliang Zhao,Tong Wen,Tingting Zhang,Shaoxian Song
In this work, the iron-containing smectite nontronite (NNT) was artificially prepared by hydrothermal process and used as a heterogeneous catalyst to activate bisulfite (BS) for degradation of tetracycline (TC). Two NNT samples with different iron content (NNT1 and NNT2) were characterized by XRD, FTIR, XPS and SEM-EDS analysis. Under dark condition, the TC removal rates of NNT1/BS and NNT2/BS reached about 91.7% and 95.5% respectively at 60 min. Due to the heterogeneous catalysis of structural Fe(III), the NNT catalysts showed great catalytic activity and low iron leaching at the pH range 3.0–7.5. In addition, NNT particles were also stable and reusable in activating BS for TC removal. According to the EPR and radical quenching experiments, it could be proved that the precursor radical • SO 3 ˉ was first generated in NNT/BS system, then • SO 4 ˉ and • OH were the active species that played a role in TC degradation . The synthetic NNT clay is a promising Fe-based catalyst for treatment of TC wastewater thanks to its high activity, good stability and effective reusability .
研究领域:
环境科学
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催化化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Journal of Environmental Sciences
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2022
·
IF 6.796
Hao-Jie Cui,Yaqi Ning,Cong Wu,Wei Peng,Dong Cheng,Lichu Yin,Weijun Zhou,Wenjuan Liao
It has been documented that organic contaminants can be degraded by hydroxyl radicals (•OH) produced by the activation of H 2 O 2 by Fe(II)-bearing clay. However, the interfacial electron transfer reactions between structural Fe(II) and H 2 O 2 for •OH generation and its effects on contaminant remediation are unclear. In this study, we first investigated the relation between •OH generation sites and sulfamethoxazole (SMX) degradation by activating H 2 O 2 using nontronite with different reduction extents. SMX (5.2–16.9 µmol/L) degradation first increased and then decreased with an increase in the reduction extent of nontronite from 22% to 62%, while the •OH production increased continually. Passivization treatment of edge sites and structural variation results revealed that interfacial electron transfer reactions between Fe(II) and H 2 O 2 occur at both the edge and basal plane. The enhancement on basal plane interfacial electron transfer reactions in a high reduction extent rNAu-2 leads to the enhancement on utilization efficiencies of structural Fe(II) and H 2 O 2 for •OH generation. However, the •OH produced at the basal planes is less efficient in oxidizing SMX than that of at edge sites. Oxidation of SMX could be sustainable in the H 2 O 2 /rNAu-2 system through chemically reduction. The results of this study show the importance role of •OH generation sites on antibiotic degradation and provide guidance and potential strategies for antibiotic degradation by Fe(II)-bearing clay minerals in H 2 O 2 -based treatments.
研究领域:
环境科学
·
污染修复
✓ 已验证
产品关联
DOI
PubMed
高影响因子
GEOCHIMICA ET COSMOCHIMICA ACTA
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2018
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IF 4.69
Songhu Yuan,Xixiang Liu,Wenjuan Liao,Peng Zhang,Xiaoming Wang,Man Tong
Production of hydroxyl radicals ( OH) has been recently revealed upon oxygenation of sediments in redox-dynamic subsurface environments. In particular, Fe(II)-bearing clay minerals are the major sediment components contributing to OH production upon oxygenation, and the produced OH can oxidize contaminants and inactivate bacteria. Whereas, the mechanisms of OH production from oxygenation of Fe(II)-bearing clay minerals remain elusive. The objectives of this study were to identify the structural variation of Fe(II) entities during the oxidation of Fe(II)-bearing clay minerals by O 2 , and to unravel the mechanisms of electron transfer within the mineral structure and from mineral to O 2 for OH production. Nontronite (NAu-2, 23% Fe) which was chemically reduced to 54.5% Fe(II) in total Fe was used as a model Fe(II)-bearing clay mineral. Production of OH and oxidation of Fe(II) were measured during the oxidation of reduced NAu-2 by O 2 . A wide spectrum of spectroscopic techniques, including Fourier transform infrared spectroscopy (FTIR), Fe K-edge X-ray absorption spectroscopy (XAS), Mössbauer spectra, and X-ray photoelectron spectroscopy (XPS), were employed to explore the structural variation of Fe(II) entities in NAu-2 and the electron transfer within NAu-2 and from NAu-2 to O 2 . For 180 min oxidation of 1 g/L reduced NAu-2, a biphasic OH production was observed, being quick within the initial 15 min and slow afterwards. Production of OH correlates well with oxidation of Fe(II) in the reduced NAu-2. Within the initial 15 min, trioctahedral Fe(II)-Fe(II)-Fe(II) entities and edge Fe(II) in the reduced NAu-2 were preferentially and quickly oxidized, and electrons from the interior Fe(II)-Fe(II)-Fe(II) entities were most likely ejected from the basal siloxane plane to O 2 . Meanwhile, trioctahedral Fe(II)-Fe(II)-Fe(II) entities were mainly transformed to dioctahedral Fe(II)-Fe(II) entities. When the time of oxygenation was longer than 15 min, dioctahedral Al-Fe(II), Fe(II)-Fe(II) and Fe(II)-Fe(III) entities were slowly oxidized, and the interior electrons were transported through Fe(II)-O-Fe(III) linkages to edges and then ejected to O 2 . In the slow stage of oxidation, electrons from interior Fe(II) accumulated towards the near surface layers and fueled the regeneration of edge Fe(II) for OH production. In both stages, one-electron transfer mechanism with the involvement of O 2 − and H 2 O 2 applies for OH production from the oxidation of structural Fe(II) by O 2 . The mechanisms unraveled in this study advance the understanding of reactive oxygen species (ROS) production and structural Fe variation when Fe(II)-bearing clay minerals are oxygenated in redox-dynamic systems.
研究领域:
环境科学
·
矿物学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）