SEPARATION AND PURIFICATION TECHNOLOGY
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2022
·
IF 9.136
Wenbin Gao,Yan Tan,Binhai Wu,Yuzhen Chen,Zhan Hu,Yifan Wang,Yujiao Wen,Zhi Zhou,Nan Zhou
Quinclorac (QNC) and Cr(VI), are common contaminants in surface waters, posing serious hazard to human and ecological health. Nano FeS, an effective catalyst that has excellent redox properties, is susceptible to over-oxidation and agglomeration problems, which impede its practical application. Herein, nano-Fe 1−x S was modified by stable iron oxide (Fe 3 O 4 ) and biochar (BC AA /Fe 1−x S/Fe 3 O 4 ), which presented the core (Fe 1−x S) shell (Fe 3 O 4 )-like structure uniformly dispersed on BC AA surface. The composite overcame the disadvantages of nano-Fe 1−x S and achieved high removal efficiency of 100% and 99.98% for QNC and Cr(VI), respectively. Based on XPS analysis, Fe(II) content was reduced from 53.3% to 34.2% and S(II) content from 13.0% to 6.5%. Fe(II) species in the composite were the main active substance for QNC degradation and Cr(VI) reduction, and S(II) species also indirectly provided electrons to promote Fe 2+ /Fe 3+ cycling. Then, we identified the intermediates of QNC and active radicals • OH or SO 4 •− in the system to suggest possible degradation pathways. We further discovered no mutual interference between QNC and Cr(VI) and proposed the possible mechanism for simultaneous removal that QNC degradation by radical attack and Cr(VI) reduction by electrons.
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LUMINESCENCE
·
2021
·Vol. 37
·期 1
·72-81
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IF 2.464
Haonan Zhao,Junfeng Zhang,Xiaolian Lin,Huihui Li,Qinhe Pan
Cr(VI) is a type of dangerous effluent that has caused great harm to human health and the environment. Recognition and perception of Cr(VI) by artificial receptors has attracted extensive attention. A novel fluorescent chemical sensor based on the 5,7-dihydroxyflavone skeleton was designed and synthesized for the selective recognition of Cr(VI). As confirmed by fluorescence technology, the fluorescent probe 4-dimethylaminobenzyl chrysin ester–Zn (DBC–Zn) showed high sensitivity and selectivity for dichromate and a fast response (less than 30 sec) recognition. The fluorescence intensity of DBC–Zn varies linearly with the concentration of Cr(VI) in the range 0.1–1 μM. The detection limit of Cr 2 O 7 2− by DBC–Zn is 2.3 nM, which is far lower than the national safe drinking water standard stipulated by the US Environmental Protection Agency (1.9 μM). The quenching mechanism of the probe can be attributed to the interaction of the dynamic quenching effect and the fluorescence internal filtration effect. In addition, the probe has good stability in both neutral and alkaline environments, and the accuracy of quantitative analysis of Cr 2 O 7 2− in lake water or tap water is more than 80%. The test paper based on DBC–Zn can effectively detect Cr 2 O 7 2− at the concentration of 100 ppb. This shows that the probe has a certain practical application value.
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Catalysts
·
2021
·Vol. 11
·期 10
·1186
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IF 4.146
Yarui Wang,Wanchao Yu,Fanglan Geng,Lixia Zhao,Yawei Wang
The coexistence of pollutants presents a great challenge to the implementation of photocatalysts. In this work, a novel MIL-101(Fe)/TiO2composite prepared by in situ growth of MIL-101(Fe) on TiO2was developed for the synergetic oxidation of MC-LR and Cr(VI) reduction. The heterojunction material shows elevated photocatalytic behavior under ultraviolet compared with the unary pollutant system. Furthermore, quenching experiments and electron spin resonance confirm that the enhanced photodegradation behavior is related to the synergistic effect between the photocatalytic reduction and oxidation process, in which MC-LR consumes the holes and Cr(VI) captures electrons, followed by efficient charge separation through the conventional double-transfer mechanism between MIL-101(Fe) and TiO2. This investigation provides a deeper understanding of the construction of MOFs/semiconductor heterojunctions for the pollutants removal in multi-component contaminants system.Keywords:TiO2@MOF photocatalyst;Cr(VI);microcystin-LR;synergetic removal
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Polymers
·
2021
·Vol. 13
·期 21
·3788
·
IF 4.329
Hua Zeng,Zhiyuan Hu,Chang Peng,Lei Deng,Suchun Liu
Due to its lethal effect on the human body and other creatures, Cr(VI) ions have attained widespread public attention, and an effective adsorbent for removing Cr(VI) ions is vital. Chitosan (CS)/cellulose nanocrystals grafted with carbon dots (CNCD) composite hydrogel with strong sorption ability and sensitive detection ability for Cr(VI) was formed. The cellulose nanocrystals (CN) offered a natural skeleton for assembling 3D porous structures, and then improved the sorption ability for Cr(VI); moreover, carbon dots (CD) acted as a fluorescent probe for Cr(VI) and provided Cr(VI) adsorption sites. With a maximum adsorption capacity of 217.8 mg/g, the CS/CNCD composite hydrogel exhibited efficient adsorption properties. Meanwhile, with a detection limit of 0.04 μg/L, this hydrogel was used for selective and quantitative detection of Cr(VI). The determination of Cr(VI) was based on the inner filter effect (IFE) and static quenching. This hydrogel retained its effective adsorption ability even after four repeated regenerations. Furthermore, the economic feasibility of the CS/CNCD composite hydrogel over activated carbon was confirmed using cost analysis. This study provided one new method for producing low-cost adsorbents with effective sorption and sensitive detection for Cr(VI).Keywords:chitosan;cellulose nanocrystals;carbon dots;adsorption;hexavalent chromium
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Catalysis Science & Technology
·
2021
·Vol. 11
·期 24
·7963-7972
·
IF 6.119
Anyu Liu,Jianqiang Hu,Jiale He,Xinyue Huang,Na Hu,Yuqin Li,Qingling Huang,Shien Guo,Xin Liu,Zhen Yang,Yong Zhou,Zhigang Zou
O-doped g-C3N4/In2S3 hierarchical heterostructures with a direct Z-scheme mechanism were devised and constructed simply via loading In2S3 nanoflakes on the surface of O-doped g-C3N4 (OCN) hierarchical structures, in situ, employing pre-obtained OCN (prepared by condensation of oxalic acid and urea) and indium(III) dimethyldithiocarbamate (In(dedc)3) as precursors. Analyses of the energy band structure, density functional theory (DFT) computations and DMPO-ESR spin-trapping experiments demonstrate that the formation of a perfect heterointerface with a staggered alignment of band edges between OCN and In2S3 (IS), owing to their close contact, enables photoexcited carriers to migrate via a Z-scheme route, which can maintain the higher reduction and oxidation capability of electrons and holes, respectively. Furthermore, the Z-scheme OCN/IS heterostructures efficaciously facilitate the separation of photogenerated electrons and holes, as demonstrated using PL spectra, transient photocurrent densities and electrochemical impedance spectra (EIS). These lead to the enhanced photocatalytic activity towards reducing Cr(VI) into Cr(III). Besides, the integration of OCN with IS can enhance the responsiveness to visible light based on the results of UV-vis DRS, thereby inducing the formation of more electrons and holes,and also contributing to the improvement of the photocatalytic activity for Cr(VI) reduction. In consequence, all the pre-prepared OCN/IS hybrids possess markedly improved photocatalytic activities for Cr(VI) reduction, relative to pure OCN and pristine IS under visible light (λ > 420 nm) illumination. With the increase in the In(dedc)3 to OCN mass ratio (R), the photocatalytic activities of these OCN/IS hybrids increase first and then decrease. The sample with an optimum R of 0.9 (OCN/IS-0.9) can remove nearly 100% of Cr(VI) after 40 min of illumination, being superior to most of g-C3N4-based and IS-based photocatalysts. Its reaction rate constant for Cr(VI) photoreduction (0.08947 min−1) is 56.7 fold and 8.8 fold higher than that of pure OCN (0.00155 min−1) and pristine IS (0.00913 min−1), respectively. This work affords a deep understanding on designing preeminent Z-scheme photocatalysts towards the degradation of Cr(VI) under visible-light irradiation.
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Journal of Cleaner Production
·
2021
·
IF 9.297
Liji Bai,Xiujuan Su,Jinpeng Feng,Shaojian Ma
In this study, a sugarcane bagasse biochar/nano-iron oxide composite was prepared via a one-pot pyrolysis method by using the sugarcane bagasse-based solid waste and microwave as the raw material and energy source, respectively. The developed composite was characterized by BET, XRD , FT-IR and TEM and was applied for the removal of Cr (VI) from water. The composite was observed to be mainly composed of amorphous carbon , Fe 3 O 4 and Fe 2 O 3 . The iron oxides were uniformly embedded on the surface of the carbon layer by van der Waals force . The sugarcane bagasse-based biochar/nano-iron oxide composite material exhibited an optimal Cr (VI) adsorption capacity of 55 mg/g under the experimental conditions specified in this study. The Cr (VI) adsorption mechanism of the Fe 2 O 3 /Fe 3 O 4 /WBC composite was explained through FTIR, XPS, charge transfer analyses, and density functional theory calculations (DFT). The deposition of Cr (VI) on the surface of the composite was attributed to electrostatic interaction, redox reactions and complexation between the Fe 2 O 3 /Fe 3 O 4 /WBC composite and Cr (VI) contained in the solution.
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Journal of Environmental Sciences
·
2021
·
IF 5.565
Ruolin Cao,Shiqing Liu,Xinyu Yang,Chunfeng Wang,Yanbin Wang,Wanfeng Wang,Yunqing Pi
Although widely used in permeation reaction barrier (PRB) for strengthening the removal of various heavy metals, zero-valent iron (ZVI) is limited by various inherent drawbacks, such as easy passivation and poor electron transfer . As a solution, a synergistic system with PRB and electrokinetics (PRB-EK) was established and applied for the efficient removal of Cr(VI)-contaminated groundwater. As the filling material of PRB, ZVI/Fe 3 O 4 /activated carbon (ZVI/Fe 3 O 4 /AC) composites were synthesized by ball milling and thermal treatment. A series of continuous flow column experiments and batch tests was conducted to evaluate the removal efficiency of Cr(VI). Results showed that the removal efficiency of Cr(VI) remained above 93% even when the bed volume (BV) reached 2000 under the operational parameters (iron/AC mass ratio, 2:1; current, 5 mA). The mechanism of Cr(VI) removal by the PRB-EK system was revealed through field emission scanning electron microscopy images, X-ray diffraction, X-ray photoelectron spectroscopy, Fe 2+ concentration, and redox potential (E h ) values. The key in Cr(VI) reduction was the Fe 2+ /Fe 3+ cycle driven by the surface microelectrolysis of the composites. The application of an externally supplied weak direct current maintained the redox process by enhancing the electron transfer capability of the system, thereby prolonging the column lifetime. Cr(VI) chemical speciation was determined through sequential extraction, verifying the stability and safety of the system. These findings provide a scientific basis for PRB design and the in-situ remediation of Cr(VI)-contaminated groundwater.
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JOURNAL OF HAZARDOUS MATERIALS
·
2021
·
IF 10.588
Meilin Liu,Taotao Li,Cheng Zhang,Yu Zheng,Chenqing Wu,Jian Zhang,Kui Zhang,Zhongping Zhang
In this work, amino-functionalized mesoporous silica nanospheres (NH 2 -mSiO 2 ) anchored with carbon dots (CDs) have been designed to construct an outstanding fluorescent sensor for heavy metal detection. Uniform mSiO 2 was chosen to provide an optically transparent scaffold for immobilizing CDs. With the help of amino group modification on the surface of silica, benzene-1,4-diboronic acid (BA) was used as raw material to load CDs in the pores of mSiO 2 by one-step solvothermal method. The proposed nanohybrid can solve the problem of aggregation-induced fluorescence quenching, leading to bright blue emission at 450 nm. Meanwhile, the fluorescence of NH 2 -mSiO 2 @CDs showed high sensitivity to Cr(VI) in acetic acid buffer solution (pH = 4) with detection limit as low as 5 nM by inner filter effect (IFE) and electrostatic interaction (EI). The proposed method can also be extended to other CDs-based detection systems for chemical/biological sensors.
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Journal of Central South University
·
2021
·Vol. 28
·期 6
·1652-1664
·
IF 1.716
Jiang Chun-lu,Wang Rui,Chen Xing,Zheng Liu-gen,Cheng Hua
Chitosan-coated fly ash (CWF) was prepared by the acid leaching-coating method. Chitosan and fly ash were crosslinked in the solution of acetic acid and sulfuric acid. The microstructure of CWF was conducted by scanning electron microscope (SEM) and X-ray diffraction (XRD). The removal of Cr(VI) from water by CWF was studied by adsorption experiments. The composite prepared by the experiment developed a pore structure and a crystal structure similar to SiO 2 and chitosan chain-like coating was formed on the surface of fly ash. The new modified material has larger surface roughness, specific surface area and more adsorption channels. The Cr(VI) was enriched in modified materials by electrostatic adsorption between CrO 4 2− , CrO 7 2− and —NH 3 + group and surface acid functional groups. The movement of Cr(VI) in solution is a diffusion process from the main body of the liquid phase to the surface of the liquid film.
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高影响因子
APPLIED CLAY SCIENCE
·
2020
·
IF 4.605
Zhenyuan Li,Zhidong Pan,Yanmin Wang
A ternary nanocomposite integrating polyethyleneimine (PEI), magnetite (Fe 3 O 4 ) nanoparticles , and illite/smectite clay nanoflakes (denoted as PEI-MI/S) was prepared via a mechanochemical route in a high-energy density stirred bead mill. The ternary PEI-MI/S nanocomposite was determined by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry , scanning electron microscopy, transmission electron microscopy , vibrating sample magnetometry and X-ray photoelectron spectroscopy, respectively. The results show that ternary PEI-MI/S nanocomposite can be prepared in the presence of intense grinding , which can graft a more amount of PEI rather than that prepared in the absence of grinding. The compressive and shear stresses in intense grinding can disperse Fe 3 O 4 nanoparticles and exfoliate/destruct I/S clay nanoflakes. Also, the mechanochemical effect facilitates the hydrogen bond and electrostatic interaction between PEI and magnetic I/S, and the crosslink reaction between PEI and glutaraldehyde in grinding, resulting in a more grafting amount of PEI. Ternary PEI-MI/S nanocomposite was applied for the removal of hexavalent chromium (Cr(VI)) anions in aqueous solution. The effect of parameters (i.e., pH value, adsorption time, temperature, and initial concentration of Cr(VI) anions) on the adsorption performance was investigated. It is indicated that the adsorption of Cr(VI) anions onto PEI-MI/S nanocomposite be related to the adsorption/reduction process. Ternary magnetic PEI-MI/S nanocomposite with a saturated magnetization (Ms) of 14.7 emu/g facilitates the magnetic separation and reusability . The regenerated ternary PEI-MI/S nanocomposite can maintain 71.43% of initial activity for adsorption of Cr(VI) anions after 6 cycles.
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JOURNAL OF COLLOID AND INTERFACE SCIENCE
·
2020
·
IF 7.489
Zhiyun Kong,Yajie Du,Junfu Wei,Huan Zhang,Longwei Fan
Removing hexavalent chromium (Cr(VI)) from aqueous solution is strategically important. A novel and selective adsorbent was synthesized using a high electron beam irradiation pre-grafting and post-surface ion imprinting method using Cr(VI) and polypropylene (PP) fibers as the template and substrates, respectively. The results obtained using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TG) indicated that the prepared sorbent was successfully synthesized. At the same time, the adsorption performances were studied through batch experiments. The results exhibited rapid adsorption kinetics, a wide working pH range, and excellent selectivity and regeneration. The equilibrium adsorption was achieved within 30 min, the maximum sorption capacity of Cr(VI)-IIPs was 156.5 mg g −1 and partition coefficients (PC) was 0.591 mg g −1 uM −1 at 400 mg L −1 initial concentration and 298 K. The relative selectivity coefficients of the ion-imprinted polymer (IIP) for Cr 2 O 7 2− /HPO 4 2− and Cr 2 O 7 2− /NO 3 − were 36.7 and 39.9, respectively. In addition, the prepared sorbent has a negligible loss in adsorption capacity after five cycles. IIP has good application prospects in the selective removal of Cr(VI) ions.
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JOURNAL OF HAZARDOUS MATERIALS
·
2020
·
IF 9.038
Guangda Yu,Fenglian Fu,Chujia Ye,Bing Tang
The mobility of Cr(VI) in the environment is affected by the transformation of ferrihydrite (Fh) and ferrihydrite-humic acid co-precipitates (Fh-HA). However, the impacts of Fe(II)-induced transformation of Fh and Fh-HA on the mobility, speciation and partitioning of associated Cr(VI) remain unclear. In this study, the behaviors of adsorbed Cr(VI) during Fh and Fh-HA aging at 70 °C for 9 days (pH 0 = 3.0 and 7.0) in the absence and presence of Fe(II) were studied. Results revealed that the main speciation of Cr(VI) after transformation was non-desorbable Cr and its formation involved the following pathways. Firstly, Fe(II) (0.2 and 2.0 mM) induced the transformation of Fh-HA to hematite and goethite, promoting the structural incorporation of adsorbed Cr into hematite and goethite via complexation. Secondly, under neutral condition (pH 0 = 7.0), the low concentration of Fe(II) (0.2 mM) could not reduce completely Cr(VI) to Cr(III) and thus residual Cr(VI) was incorporated into the Cr(III)-Fe(III) co-precipitates. Thirdly, coprecipitated humic acid not only reduced Cr(VI) to Cr(III) via polysaccharide, but also formed complexes with incorporated Cr through carboxylic groups to sequester Cr. Our results demonstrate that Fe(II)-induced transformation of Fh-HA exerts major influences on associated Cr(VI) speciation and partitioning.
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