Environmental Science-Processes & Impacts
·
2020
·Vol. 23
·期 1
·109-116
·
IF 3.238
Ziyu Zhao,Quan Chen,Hao Li,Di Lang,Meixuan Wu,Dandan Zhou,Bo Pan,Baoshan Xing
Environmentally persistent free radicals (EPFRs) have drawn increasing attention. It is reported that EPFR formation is dependent on the presence of transition metals; however the size of the metal particles is ignored. In this study, we hypothesized that transition metals in smaller particle sizes could more efficiently promote the generation of EPFRs and thus have higher risks. Nanosized hematite (nanoHMT) and microsized hematite (microHMT) were studied and compared. We monitored the degradation of catechol and the generation of EPFRs under both dark and ultraviolet light conditions. Catechol degradation was inhibited in the presence of hematite in the dark, with more significant inhibition by nanoHMT. However, under ultraviolet light, catechol degradation was promoted by hematite, with more significant promotion by nanoHMT. The yield of free radicals in the nanoHMT system was always higher than that in the microHMT system. More dimers were detected in the nanoHMT system, which may have played an important role in stabilizing free radicals. More trivalent Fe was converted to divalent Fe in the nanoHMT system than in the microHMT system. The relatively more active sites for the catechol interaction promoted EPFR generation. These results highlighted that size-dependent reactions should be well considered when predicting the environmental behavior and risks of organic contaminants.
研究领域:
环境科学
·
化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Environmental Science-Nano
·
2024
·
IF 5.8
Chaorong Chen,Haiyang Xian,Jing Liu,Qingze Chen,Xiaoliang Liang,Runliang Zhu,Michael F. Hochella
Photochemical and adsorptive reactions occurring at the mineral–water interface are of great importance in controlling the fate and transport of contaminants in nature, but the effects of the mineral surface structure on the interplay of these two processes and the underlying mechanisms remain largely unknown. In this work, two different structurally well-defined hematite nanocrystals were employed to explore the coupled photoreduction and immobilization of Cr(VI) on various facets of hematite under light irradiation. Compared with hematite quasi-nanocubes (HNCs) exposing only {012} facets, hematite nanoplates (HNPs) with exposed {001} and {113} facets exhibited higher immobilization ability for Cr(VI) under light irradiation, indicating that the coupled process of photoreduction and adsorption of Cr(VI) strongly relied on the particularly exposed facets of hematite. X-ray photoelectron spectroscopy measurements indicated that the removed Cr(VI) from solution was mainly immobilized on hematite surfaces in the form of Cr(III) (the reduced products of Cr(VI)). Transmission electron microscopy and electron energy-loss spectroscopy results revealed that the accumulation of Cr species was predominantly on the {113} facets of HNPs and the {012} facets of HNCs. Theoretical calculations show that the work function difference between the {113} and {001} facets was directly linked with the effective separation of photogenerated electron–hole pairs in HNPs, which is beneficial for the reduction of Cr(VI). The results of desorption experiments indicate that the coupling of photoreduction and adsorption processes significantly promotes the long-term immobilization of Cr species and effectively reduces their environmental risks (the desorption of Cr(VI) from the HNP and HNC samples decreased from 35.9% and 33.5% to 0.3% and 1.7%, respectively). Overall, the exposed facets can significantly affect the electron transfer properties of hematite as well as the binding affinity for Cr species, thereby governing the reduction and immobilization behavior of Cr(VI) on various facets of hematite. These results advance our understanding of the speciation and immobilization of redox-sensitive contaminants at the surfaces of semiconducting minerals in nature.
研究领域:
环境科学
·
表面化学
✓ 已验证
产品关联
DOI
高影响因子
WATER RESEARCH
·
2022
·
IF 13.4
Liping Fang,Baolin Gao,Fangbai Li,Kai Liu,Jialin Chi
The incorporation of secondary metal atoms into iron oxyhydroxides may regulate the surface chemistry of mediating electron transfer (ET) and, therefore, the biogeochemical pollutant processes such as arsenic (As) in the subsurface and soils. The influence of incorporating two typical metals (Cu and Zn) into a specific {001} hematite facet on O 2 activation by surface-bound Fe(II) was addressed. The results showed that Cu-incorporated hematite enhances As(III) oxidation in the presence of Fe(II) under oxic conditions and increases with increasing Cu content. Conversely, Zn incorporation leads to the opposite trend. The As(III) oxidation induced by surface-bound Fe(II) is positively related to the Fe(II) content and is favorable under acidic conditions. Reactive oxygen species (ROS), such as superoxide (·O 2− ) and H 2 O 2 , predominantly contribute to As(III) oxidation as a result of 1-electron transfer from bound Fe(II) to surface O 2 on hematite and radical propagation. Electrochemical analysis demonstrates that Cu incorporation significantly lower the oxidation potential of Fe(II) on hematite, whereas Zn led to a higher reaction potential for Fe(II) oxidation. Subsequently, distinct surface reactivities of hematite for the activation of O 2 to form ROS by surface-bound Fe(II) are evidenced by metal incorporation. Our study provides a new understanding of the changes in the surface chemistry of iron oxyhydroxides because of incorporating metals (Zn and Cu), and therefore impact the biogeochemical processes of pollutants in soils and subsurface environments.
研究领域:
环境科学
·
土壤化学
·
地球化学
✓ 已验证
DOI
高影响因子
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
·
2012
·Vol. 20
·期 1
·31-38
·
IF 2.651
Wang Yajie,Xu Jing,Zhao Yan,Zhang Lin,Xiao Mei,Wu Feng
Iron and arsenic have been found to coexist in a water environment and the fate of arsenite in the aquatic system is influenced by iron. Goethite is a form of iron hydroxide, which is commonly found in sediments. In previous studies, we have used iron complexes to degrade organic pollutants. Results have shown that some organic pollutants could be totally degraded by iron complexes and our work indicated that iron might cause conversion of arsenic when irradiated. This work attempts to investigate the conversion of arsenite [As(III)] using natural goethite, as the iron source, to quantify the effect of various factors on photooxidation. We also consider the possible mechanism for photooxidation of As(III) using a suspension of natural goethite. The As(III) concentration variation under illumination was compared with the one in the dark to quantify the contribution of light to As(III) oxidation to As(V) in goethite suspended solution. The experiments under N 2 and air atmosphere confirmed the participation of dissolved oxygen. The photooxidation efficiency of As(III) under different conditions was compared to determine the effect of different environmental factors such as pH value, goethite concentration, and humic acid concentration on the photooxidation reaction. In the solution containing 100 μg L −1 arsenite and 0.1 g L −1 suspended goethite at pH 3.0, nearly 80 % of As(III) was photooxidized after irradiation by a 250-W metal halogen lamp ( λ ≥ 313 nm) after 6 h. The effects of initial pH and goethite concentration and humic acid concentration were all examined. The results show that the greatest efficiency of photooxidation of As(III) was at pH 3.0. The extent of photooxidation decreased with increasing goethite concentration and fell sharply in the presence of humic acid under the conditions in this work. Although about 80 % of As(III) was photooxidized after irradiation by a 250-W halogen lamp at pH 3.0 in the presence of goethite suspension, photooxidation was also affected by factors such as pH, concentration of goethite, and presence of humic acid. The scavenger experiments showed that the HO• radical and photogenerated hole are the predominant oxidants in this system responsible for 87.1 % oxidation of As(III), while HO
• 2
/O
•− 2
is responsible for 12.9 % oxidation of As(III).
研究领域:
环境科学
·
化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Journal of Cleaner Production
·
2021
·
IF 9.297
Yun Li,Haotian Xue,Pekka Taskinen,Ari Jokilaakso,Chaobo Tang,Wei Jin,Minna Rämä,Yongming Chen,Shenghai Yang
In view of the issues of low efficiency and environmental pollution existing in current antimony production, this work proposes an innovative and cleaner process to extract antimony from stibnite concentrate and co-treat goethite residues. The mechanisms of antimony extraction and zinc, iron, sulfur conservation was thermodynamically and experimentally investigated. The results show that iron- and zinc-bearing components in the goethite residue firstly reacted and releasing Fe x O y and ZnO, then stibnite (Sb 2 S 3 ) quickly converted to senarmontite (Sb 2 O 3 ) in the presence of Fe x O y and ZnO. Intermediate Sb 2 O 3 was subsequently reduced to metallic Sb. Bench-scale experiments of antimony extraction from stibnite concentrate with goethite residue as sulfur-fixing agent validated that 85.7% of Sb was directly recovered as crude antimony bullion, only around 7.4% antimony volatilized to fume. Pb, As, Au, and Ag tended to also be co-enriched in the bullion. 97.4% of sulfur, 88.8% of zinc and 86.1% of iron were recovered and fixed simultaneously. Sulfur in Sb 2 S 3 , iron and zinc contained in goethite residues was conserved in matte as marketable Fe 2 Zn 3 S 5 , FeS, and ZnS, instead of forming gaseous SO 2 . This novel process is a promising recycling and co-treatment alternative for various secondary iron- and zinc-containing materials.
研究领域:
冶金学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY
·
2020
·Vol. 324
·期 2
·715-729
·
IF 1.137
Wei Hongfu,Dong Faqin,Chen Mulan,Zhang Wei,He Miao,Liu Mingxue
As jarosite and oxalic acid are ubiquitous in nature, we investigated a remediation technology for uranium-contaminated site by photoinduced reduction coupled with adsorption of jarosite. Jarosite exhibited excellent adsorption properties for uranium, with a highest adsorption capacity 453.98 mg g −1 . With the presence of oxalic acid, U(VI) was removed at a reduction ratio of 30.71% under irradiation. It may be that oxalic acid promoted the reduction of Fe(III) to Fe(II) in jarosite, and then Fe(II) reduced U(VI) to U(IV). The results confirmed the applicability of the remediation by adsorption using jarosite and light-induced reduction.
研究领域:
环境科学
·
生物化学
✓ 已验证
产品关联
DOI
高影响因子
SCIENCE OF THE TOTAL ENVIRONMENT
·
2022
·
IF 10.753
Jiayi Xu,Hanpei Yang,Jun Hou,Lingzhan Miao,Jun Wu
Ferrihydrite (Fh) often coexists with organic matter (i.e., humic acid (HA)) in the environment; however, its impacts on the transformation of hexavalent chromium (Cr(VI)) is poorly understood during the sulfidation of Fh. Upon exposed to 2 mM sulfide for 12 h, the total amount of Fe(II) (Fe( II ) tot , 0.78 mM) in treatments with HA (300 mg HA/L) was higher than that (0.67 mM) in treatments without HA, since HA could enhance the solubility of Fe(II). After then, the Cr(VI) was reduced by sulfidated Fh. Aqueous Cr(VI) concentration (Cr( VI ) aq ) declined from 0.67 to 0.43 mM with the increase of HA concentration from 0 to 400 mg/L, which was partly ascribed to the inhibition of surface passivation by HA. Moreover, the increase in Fe(II) during the sulfidation of Fh also exerted a strong impact on the transformation of Cr(VI) subsequently. In addition of HA, batch experiments suggested that EDTA could also promote the formation of Fe(II) (Fe( II ) tot , 0.80 mM), rendering a lower Cr( VI ) aq (0.59 mM) in EDTA-300 treatments. This study further demonstrated that HA played an important role in the transformation of Cr(VI), hence providing a theoretical basis for in-situ remediation of Cr(VI) in the future.
研究领域:
环境科学
·
化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHEMOSPHERE
·
2022
·
IF 8.943
Yongqiang Yang,Xiongfei Rao,Qingling Fu,Xin Zhang,Jieyu Gao,Xiang Wan,Jun Zhu,Guoyong Huang,Hongqing Hu
Organic acids usually compete the immobilization of As by iron (hydro)oxides, but their oxidizing effects are ignored. Therefore, the gallic acid (GA) with strong redox activity was chosen to investigate the influence of arsenite [As(III)] oxidation on As immobilization by ferrihydrite . Our results found that the As amount adsorbed on ferrihydrite decreased with the pH rising from 5 to 9 in the presence of GA, and the adsorption amount (28.8 g kg −1 ) at pH 9 was 45.1% lower than that in the absence of GA. Meanwhile, the As adsorption amounts in treatments of GA addition before As (Fh-GA-As(III)) were significantly lower than that in their corresponding simultaneous addition (Fh-As(III)/GA). The proportions of As(V)/As total on ferrihydrite and in equilibrium suspension were increased as the pH increased in the presence of GA, and the highest oxidation efficiency of As(III) by GA at pH 9 was 90.3%, which was mainly due to the contribution of hydrogen peroxide (H 2 O 2 , 52.6%) and semiquinone radicals (SQ − , 27.1%). In general, the oxidation and competition adsorption of As by GA inhibited the As immobilization by ferrihydrite, and the oxidation of As(III) by GA was strongly dependent on pH, while H 2 O 2 and SQ − were demonstrated as the main oxidant at pH 9.
研究领域:
环境科学
·
土壤学
✓ 已验证
DOI
高影响因子
Environmental Science-Nano
·
2024
·
IF 5.8
Shengnan Zhang,Lingyi Li,Junxue Li,Wei Cheng
Hematite displays diverse crystal structures and often coexists with Fe(II), both of which are crucial in controlling the fate and mobility of Cr(VI). However, the mechanisms underlying Cr(VI) removal in the presence of Fe(II) on various hematite facets remain elusive. This study aims to elucidate the facet-dependent reactivity of hematite nanocrystals in conjunction with Fe(II) for the removal of Cr(VI) from aqueous solutions. Hematite nanoplates (HNPs), predominantly composed of {001} facets, and nanorods (HNRs), exposing both {001} and {110} facets, were synthesized and characterized. Their Cr(VI) removal capabilities were evaluated in hematite–Cr(VI) and hematite–Fe(II)–Cr(VI) systems, as well as the Fe(II)–Cr(VI) system. The adsorption of Fe(II) and Cr(VI) on hematite surfaces was highly dependent on the crystal facets and pH, with HNRs demonstrating superior Cr(VI) adsorption over HNPs, especially under acidic conditions. Neutral pH favored Fe(II)–Cr(VI) redox reactions and Fe(II) adsorption. The hematite–Fe(II) couple displayed a synergistic effect in removing Cr(VI) under acidic conditions, which was not observed under neutral conditions. The presence of Fe(II) notably enhanced Cr(VI) adsorption onto hematite, and bound Fe(II) facilitated electron transfer, accelerating Cr(VI) reduction. HNRs–Fe(II) exhibited higher Cr(VI) removal efficiency than HNPs–Fe(II) due to their lower free corrosion potential and improved electron transport properties. This research underscores the potential of facet engineering in optimizing hematite nanocrystals for environmental remediation, specifically in Cr(VI)-contaminated environments.
研究领域:
环境科学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
NANOTECHNOLOGY
·
2017
·Vol. 28
·期 39
·394003
·
IF 3.44
Tao Fang,Yongsheng Guo,Songhua Cai,Ningsi Zhang,Yingfei Hu,Shiying Zhang,Zhaosheng Li,Zhigang Zou
Many metal-oxide candidates for photoelectrochemical water splitting exhibit localized small polaron carrier conduction. Especially hematite (α-Fe2O3) photoanodes often suffer from low carrier mobility, which causes the serious bulk electron-hole recombination and greatly limits their PEC performances. In this study, the charge separation efficiency of hematite was enhanced greatly by coating an ultrathin p-type LaFeO3 overlayer. Compared to the hematite photoanodes, the solar water splitting photocurrent of the Fe2O3/LaFeO3 n–p junction exhibits a 90% increase at 1.23 V versus the reversible hydrogen electrode, due to enlarging the band bending and expanding the depletion layer.
研究领域:
材料科学
·
光电化学
✓ 已验证
DOI
高影响因子
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY
·
2019
·Vol. 19
·期 6
·3437-3446
·
IF 1.093
Niu Yakun,Zhou Yi,Niu Ping,Shen Haiyan,Ma Ying
Ti doped hematite photoanodes have been intensively investigated due to their excellent activity for photoelectrochemical water oxidation. However, little attention has been paid to the doping effect on the photocurrent onset potential of hematite and the underlying mechanism. In this
paper, Ti doped hematite nanorod arrays were successfully prepared through a facile treatment of hematite with TiCl3 solution. The photocurrent of the Ti doped hematite photoanode increases by three times, and its onset potential shifts more positively as compared with that of the
undoped one. Electrochemical analyses were employed to unravel the mechanism of anodic shift of the onset potential. Cyclic voltammograms and electrochemical impedance spectra confirmed that more surface states were formed in Ti doped hematite than the undoped one. As a result, lower activity
towards oxygen evolution reaction (OER) and increased electron–hole recombination after light on/off in low potential region were observed in Ti doped hematite. It is concluded that these doping induced surface states may be a hindrance to charge transfer and the onset potential of Ti
doped hematite shifts anodically.
研究领域:
材料科学
·
电化学
✓ 已验证
DOI
高影响因子
Minerals
·
2024
·Vol. 14
·期 12
·1255
·
IF 2.2
Chenglong Du,Jiang Yu,Guangyi Liu
Iron ore is the main raw material of the iron and steel metallurgy industry, but quartz in iron ore reduces metallurgical efficiency and increases metallurgical costs. Therefore, iron ore desiliconization by flotation plays an important role in the iron and steel metallurgy industry. In this study, 4-tert-butyl-catechol (TBC) was designed as a collector to directly float out hematite from quartz. The micro-flotation tests demonstrated that under pH ~9.0, 1 × 10−5mol·L−1TBC recovered 98% hematite from its mixture with quartz, while the recovery of quartz was only about 17%. Zeta potential and contact angle results inferred that the adsorption affinity of TBC toward hematite was greater than that to quartz. The results of FTIR and XPS inferred that TBC adsorbed on the Fe3+sites of hematite interfaced via the O atom of its two adjacent hydroxyl groups to form a stable five-membered chelating ring at pH 9.0. This study offered new research insight on the development of novel collectors for hematite flotation through bionics technology.
研究领域:
矿物加工工程
·
材料科学与工程
✓ 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）