ENVIRONMENTAL RESEARCH
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2019
·
IF 5.026
Misganaw Alemu Zeleke,Dong-Hau Kuo
The oxy-sulfide based V 2 O 5 @(In,Ga) 2 (O,S) 3 nanocomposite catalyst, at different weight percentages of V 2 O 5 , was successfully synthesized via a simplistic procedural route for the detoxification of hazardous Cr(VI). The two pure catalysts were intimately allied and used for visible light-driven reduction of hazardous Cr(VI). The nanocomposite catalysts were characterized to observe the effects of V 2 O 5 on crystal phase, morphology, light absorption , catalytic activity , and electrical properties. Compared to all, 40% V 2 O 5 loaded nanocomposite catalyst, designated as VOS-2, exhibited the best-reducing capability. It completely reduced toxic Cr(VI) at 2 min under visible light illumination. From the kinetics, it was found that the rate constant of the nanocomposite catalyst was improved by a factor of 3.6 compared to the host nanoflower catalyst. The plausible mechanism of charge transfer process across the interfacial region indicates the diminished recombination probability of photogenerated charge carriers. Therefore, the nanocomposite catalyst is promising for enhanced reduction of Cr(VI) in the Cr-based industrial activities, which is significantly relevant for environmental remediation.
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ACS Sustainable Chemistry & Engineering
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2019
·
IF 6.97
Yangmei Ren,Lan Mei,Yingchun Gu,Na Zhao,Yuelong Wang,Rangrang Fan,Aiping Tong,Haifeng Chen,Hui Yang,Bo Han,Gang Guo
Poly(lactic acid) (PLA) stereocomplex crystallite (SC)-based electrospun nanofibers were fabricated via annealing the as-spun membranes at 100 °C for 1 h. The heat-treated nanofibers exhibit enhanced mechanical properties and thermal resistance due to the existence of SCs, which restricts the lactide chain mobility. The formation of SCs increases the intermolecular forces between l-lactide and d-lactide segments, resulting in almost 2 times higher tensile strength (8.52 ± 0.29 MPa) and 3 times higher Young’s modulus (285.48 ± 1.19 MPa) than that of the untreated membranes, which is benefitting for wider applications. Additionally, a green absorbent named HTA synthesized from tannic acid and hexamethylenediamine was introduced into the nanofibers, giving the membrane richer functions. Based on the abundant reactive functional groups on the surface, small pore size and large surface area-to-volume ratio of the nanofibers, the HTA containing membranes exhibited excellent performance in adsorbing heavy metal ions and inhibiting bacterial growth. This bifunctional membrane showed reusability for 4 cycles with retaining good removal capability of Cr(VI) and antibacterial effects. Furthermore, Cr(VI) was found to be adsorbed and converted to less toxic Cr(III) during the adsorption process, and bacteria, such as Escherichia coli and Staphylococcus aureus, were captured and broken on the surface of the nanofibers. In this study, we focused on a novel eco-friendly bifunctional SC-based PLA nanofiber to repeatedly adsorb metal ions and capture bacteria, and thus it is expected to have potential in various fields in the future.
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SEPARATION AND PURIFICATION TECHNOLOGY
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2019
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IF 5.107
Yaoqiang Wang,Ziheng Cui,Gang Xiao,Yilin Zhao,Yu Jin,Zishuai Wang,Haijia Su,Tianwei Tan
To study the applicability and mechanism of the visible-light-driven photo-reduction of Cr(VI) is important since it will elucidate the chromium cycle in natural circumstances, and since this reduction reaction is important in treating wastewater contaminated by Cr(VI). Herein, we conducted an in-depth mechanism study for this process using formic acid as electron donor. The positive dependence of the Cr(VI) conversion on the incident light intensity and the good match between the apparent quantum yield (0.0039–0.39%) and the light absorption spectrum (550–365 nm) suggests a light-induced mechanism. The light-induced charge transfer occurs through the ligand-to-metal charge transfer state of the complex which forms between one dichromate molecule and two formic acid molecules through symmetrical or asymmetrical configuration as demonstrated by DFT simulation. EPR analysis further proves that this reaction occurs through a stepwise process with Cr(V) and Cr(IV) as the intermediates. The practical use of this photochemical procedure with broad electron donor scope and wide pH, reaction temperature, and initial Cr(VI) concentration ranges, is proven by the application potential evaluation. The efficient reduction of Cr(VI) by formic acid under sunlight further proves the applicability of this photochemical procedure for the treatment of Cr(VI) contaminated wastewater. Development of the present study into both the treatment of Cr(VI) contaminated wastewater, and other visible-light-driven photo-redox reactions between metals and organics are the subject of further research and results can be expected in the near future.
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Arabian Journal of Chemistry
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2020
·
IF 4.762
Zefeng Yu,Weifeng Song,Jiayao Li,Qiuhua Li
In this paper, a metakaolin-based mesoporous geopolymer (GP-CTAB) was used as adsorbent for Cu(II) and Cr(VI) through a novel and simple synthetic route using cetyltrimethylammonium bromide (CTAB) as an organic modifier. The application of GP-CTAB for the simultaneous removal of metal anions and cations in aqueous solution was studied for the first time. The results of X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Brunauer, Emmett and Teller (BET), and Barrett, Joyner, and Halenda (BJH) methods indicate that GP-CTAB is still geopolymer even in the presence of quaternary ammonium salt cations. The material was tested to simultaneously adsorb Cu(II) and Cr(VI) from an aqueous solution. The results show that GP-CTAB can adsorb anions simultaneously without sacrificing the adsorption properties of heavy metal cations, which is superior to conventional geopolymers. The maximum theoretical adsorption capacity of GP-CTAB for Cu(II) and Cr(VI) was 108.2 mg/g and 95.3 mg/g in the binary system, respectively. It was also found that the presence of Cu(II) in the solution promoted the adsorption of Cr(VI). Given this characteristic of GP-CTAB, it has shown great application prospects in the prevention and control of heavy metal pollution.
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CHEMICAL ENGINEERING JOURNAL
·
2018
·
IF 6.735
Shixia Chen,Yifeng Huang,Xinxin Han,Zeliang Wu,Cen Lai,Jun Wang,Qiang Deng,Zheling Zeng,Shuguang Deng
Layered double hydroxides (LDHs) are currently attracting intense research interests as pollutant adsorbent due to its low cost, non-toxicity, structure amenability and anion exchange capability. Herein, 3-dimensional (3D) flower-like Ni/Al LDH were prepared to decorate H 3 PO 4 activated biomass-derived porous carbons (PAB) via a facile and green hydrothermal method. The as-synthesized nanocomposites (Ni/Al@PAB) displayed favorable removal performance towards both Cr(VI) and methyl orange (MO) from aqueous solution due to the inherited excellent Cr(VI) removal ability from PAB and MO removal ability from Ni/Al LDH. In single-component removal system, the maximum adsorption capacity of 271.5 and 412.8 mg/g for Cr(VI) and MO were achieved on Ni/Al@PAB, respectively. Remarkably, the removal capacity of Cr(VI) and MO both increased in the Cr(VI) MO binary system due to the synergistic effect including, (i) additional adsorption sites of N-containing groups from MO, (ii) electrostatic interactions by the reduced Cr(III), and (iii) mutual thermal compensation in the binary system. This work paved the way for designing novel LDHs-decorated porous carbon adsorbents and revealed that the acicular Ni/Al LDH decorated PAB could be applied as efficient and simultaneous adsorbent for coexisting toxic pollutants situations.
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INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
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2018
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IF 3.909
A.M. Omer,R.E. Khalifa,Zhaohong Hu,Hong Zhang,Chao Liu,Xiao-kun Ouyang
In this study, an innovative adsorbent based on tetraethylenepentamine (TEPA) functionalized alginate (Alg) beads (TEPA-Alg) was developed for the adsorptive removal of Cr (VI) from aqueous solutions. Chemical modification of alginate surface was carried out using p-benzoquinone (PBQ) as a coupling agent followed by functionalization with TEPA. The prepared functionalized beads were characterized using FTIR, TGA, SEM, and XPS tools. Results showed that the ion exchange capacity (IEC) significantly increased from 6.34 to 10.32 m eq g −1 with increasing TEPA concentration up to 0.05 M. Furthermore, removal (%) of Cr (VI) increased gradually from 38 to 86% with rising TEPA concentration from 0.0125 M to 0.05 M. While only 22% was recorded using native alginate beads. The gained equilibrium data were fitted to Langmuir isotherm model with maximum adsorption capacity ~ 77 mg/g and the adsorption kinetics were well-expressed by pseudo-first-order model. Reusability studies showed good adsorption properties after 5 consecutive cycles. Results achieved by this study imply that the prepared functionalized TEPA-Alg beads could be efficiently utilized for the removing Cr (VI) ions from their aqueous solutions.
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Frontiers in Chemistry
·
2018
·
IF 4.155
Wei Yanke,Mei Lefu,Li Rui,Liu Meng,Lv Guocheng,Weng Jianle,Liao Libing,Li Zhaohui,Lu Lin
Hexavalent chromium species, Cr(VI), which can activate teratogenic processes, disturb DNA synthesis and induce mutagenic changes resulting in malignant tumors. The detection and quantification of Cr(VI) is very necessary. One of the rapid and simple methods for contaminant analysis is fluorescence detection using organic dye molecules. Its application is limited owing to concentration quenching due to aggregation of fluorescent molecules. In this study, we successfully intercalated 7-amino-4-methylcoumarin (AMC) into the interlayer space of montmorillonite (MMT), significantly inhibited fluorescence quenching. Due to enhanced fluorescence property, the composite was fabricated into a film with chitosan to detect Cr(VI) in water. Cr(VI) can be detected in aqueous solution by instruments excellent, ranging from 0.005 to 100 mM with a detection limit of 5 μM.
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DALTON TRANSACTIONS
·
2015
·Vol. 45
·期 20
·8347-8354
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IF 4.197
Chen Dong,Genhua Wu,Zhuqing Wang,Wenzhi Ren,Yujie Zhang,Zheyu Shen,Tianhua Li,Aiguo Wu
A colorimetric assay is proposed for the selective detection of Cr(III) and Cr(VI) via the aggregation-induced color change of gallic acid capped gold nanoparticles (GA-AuNPs). The AuNPs are characterized using UV-vis spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS) and Fourier-transform infrared spectrometry (FT-IR). To detect Cr(III) and Cr(VI) coexisting in a sample, citrate and thiosulfate were applied to mask Cr(VI) for the detection of Cr(III), and ethylenediaminetetraacetic acid disodium salt (EDTA) was applied to mask Cr(III) for the detection of Cr(VI). At optimized experimental conditions, the selectivity of these AuNPs-based detection systems is excellent for Cr(III) and/or Cr(VI) compared with other types of metal ions. The limit of detections (LODs) of a mixture of Cr(III) and Cr(VI), Cr(III) and Cr(VI) by eye vision are 1.5, 1.5 and 2 μM, respectively, and those by UV-vis spectroscopy are 0.05, 0.1 and 0.1 μM, respectively. The minimum detectable concentrations for Cr(III) or Cr(VI) are all below the guideline value set by the US Environmental Protection Agency (EPA). The applicability of the AuNPs-based colorimetric sensor is also validated by the detection of Cr(III) and Cr(VI) in electroplating wastewater and real water samples with high recoveries.
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FIBERS AND POLYMERS
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2014
·Vol. 15
·期 7
·1364-1368
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IF 1.113
Chen Zaina,Feng Xiaoxiao,Han Danmin,Wang Liting,Cao Weipen,Shao Linjun
Porous polyacrylonitrile (PAN) fiber mat was prepared by electrospinning PAN in N,N -dimethylformide solution with poly(methyl methacrylate) (PMMA) as pore-forming agent. Then, the porous PAN fiber mat was chemical modified by the tetraethylenepentamine to acquire aminated porous polyacrylonitrile (APPAN) fiber mat. Common aminated PAN fiber mat was also prepared for comparison. The surface morphologies of the APPAN and PAN fiber mat were characterized by scanning electron microscopy (SEM) and the corresponding specific surface areas were also measured. FT-IR/ATR spectra of the APPAN and PAN fiber mat were recorded for analysis of the surface chemical structures. The Cr(VI) absorption results demonstrated that the porous structure in the fiber could obviously increase the absorption capacity of the fiber mat.
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LANGMUIR
·
2017
·
IF 3.833
Dongfang Wang,Guilong Zhang,Linglin Zhou,Min Wang,Dongqing Cai,Zhengyan Wu
A novel magnetic nanocomposite was synthesized using graphene oxide (GO), polyethylenimine (PEI), and Fe3O4 to removal hexavalent chromium (Cr(VI)) from water and soil. Therein, GO was functionalized with plenty of −NH2 by the modification of PEI through an amidation reaction, and the resulting GO/PEI reacted with FeSO4·7H2O and NaBH4 to obtain RGO/PEI/Fe3O4 (the optimal one is designated as ORPF) through an oxidation–reduction reaction. ORPF could effectively adsorb Cr(VI) through electrostatic attraction, and the adsorbed Cr(VI) ions were partially reduced to trivalent chromium (Cr(III)) with low toxicity by RGO (π electron). Afterward, the resulting ORPF-Cr could be conveniently removed from water with a magnet, achieving the maximum Cr(VI) removal capacity of 266.6 mg/g. Importantly, ORPF, once carried by sponge particles, could efficiently remove Cr(VI) from soil, and the resulting mixture could be facilely collected with a magnet on a filter net. Besides, the leaching experiment suggested that, when supported by filter paper, ORPF was able to decrease the number of leached Cr(VI) ions and meanwhile reduce them to Cr(III). This work provides a promising approach to remediate Cr(VI)-contaminated water and soil using a nanocomposite, which has a huge number of application prospects.
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Scientific Reports
·
2017
·Vol. 7
·期 1
·1-11
·
IF 4.259
Laipan Minwang,Fu Haoyang,Zhu Runliang,Sun Luyi,Zhu Jianxi,He Hongping
Recycling solid waste as functional materials is important for both environmental remediation and resource recycling. This study attempts to recycle spent Cu/Fe layered double hydroxide (Cu/Fe-LDH) which is generated from the adsorption of dyes by converting to Cr(VI) reductant and porous carbon material. Results showed that the obtained reductant was mainly composed of Fe 0 and Cu 0 , and exhibited good reductive activity toward Cr(VI). The species of Fe 0 , Fe 2+ , Cu 0 , and Cu + all favored the reduction of Cr(VI) according to X-ray photoelectron spectroscopy analysis. During Cr(VI) removal, solution pH could increase to neutral which caused the metal ions to precipitate near completion. On the other hand, the spent Cu/Fe-LDH could be employed to produce porous carbon materials, and the generated waste metals solution herein could be reused for LDH synthesis. Specific surface areas of the obtained carbon materials varied from 141.3–744.2 m 2 /g with changes in adsorbed amount of dyes on the LDH. This study illustrates that all the components of wastes can be useful resources, offering a simple recycling approach for similar organic-inorganic solid wastes. This work also enlightens us that designing a proper initial product is crucial to make waste recycling simpler.
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RESEARCH ON CHEMICAL INTERMEDIATES
·
2017
·Vol. 43
·期 9
·5217-5228
·
IF 1.369
Qin Na,Jing Kaiqiang,Chen Rui,Xiong Jinhua,Liang Ruowen,Li Zhaohui,Wu Ling
Abstract SnS 2 /SnO 2 nanocomposites have been successfully prepared via a hydrothermal method using electrospun SnO 2 nanotubes as both substrates and reactants. The ratios of the nanocomposites are controlled by varying the concentration of thioacetamide during the solvothermal synthesis processes. The as-prepared SnS 2 /SnO 2 nanocomposites exhibit considerable improvement on the photocatalytic activities for the reduction of aqueous Cr(VI) under visible light irradiation. Their photoactivities are also much higher than that of SnS 2 nanoplates and a physical mixture of SnO 2 and SnS 2 . In particular, the SnS 2 /SnO 2 -B sample exhibits the highest photocatalytic activity. After visible light irradiation for 60 min, the reduction rate has reached about 100%. The photoelectrochemical analyses further show that the high photocatalytic activity of the SnS 2 /SnO 2 -B sample can be ascribed to the unique structural features and the intimate interfacial contact between SnS 2 and SnO 2 , which is more effective separation of the photo-generated carriers. Graphical Abstract
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