Journal of Environmental Sciences
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2014
·
IF 1.922
Wei Yao,Pinhua Rao,Irene M.C. Lo,Wenqi Zhang,Wenrui Zheng
Pollutants that exist in anionic species are issues of concern in water treatment . Compared to cationic pollutants, the removal of anionic pollutants by adsorption is more difficult because most adsorbents carry predominantly negative charges in neutral and alkaline environments . In this study, a cross-linked chitosan derivative with quaternary ammonium and magnetic properties (QM-chitosan) was prepared and employed to remove chromium(VI) and phosphorus(V) (Cr(VI) and P(V)) from aqueous environments. The QM-chitosan was characterized by Fourier transform infrared spectrometry (FT-IR), thermogravimetric analysis (TGA), energy dispersive X-ray (SEM-EDX) and zeta potential . Batch experiments show that QM-chitosan can effectively remove Cr(VI) and P(V), and the main mechanism was believed to be electrostatic interaction. A pseudosecond-order model was fitted to describe the kinetic processes of Cr(VI) and P(V) removal. The adsorption isotherms of both Cr(VI) and P(V) on the QM-chitosan were well fitted by the Langmuir isotherm equation. The saturated adsorption capacity of P(V) (2.783 mmol/g) was found to be higher than that of Cr(VI) (2.323 mmol/g), resulting from the size of the H 2 PO 4 − ions being smaller than that of the HCrO 4 − ions. However, the theoretical calculation and experimental results showed that QM-chitosan had a stronger affinity for Cr(VI) than P(V). The adsorption–desorption of the QM-chitosan was evaluated, and high regeneration rates were demonstrated.
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COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
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2015
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IF 2.752
Xiaokun Wang,Yingqin Wei,Shasha Wang,Lingxin Chen
In this work, a simple “red-to-blue” colorimetric method for highly sensitive and selective determination of Cr (III) and Cr (VI) was presented, which was based on the aggregation of Tween 20-stabilized gold nanoparticles (Tween 20-Au NPs). This strategy relied upon the distance-dependent optical properties of gold nanoparticles (Au NPs), strong chelating between Cr (III) and citrate, and the reduction of Cr (VI) to Cr (III) by ascorbic acid (AA). Cr (III) could chelate with citrate to form a stable Cr (III)-citrate complex and thereby induce the aggregation of Tween 20-Au NPs. Thus, the sensing of Cr (III) and Cr (VI) based on aggregation of Au NPs was developed with the color of the Au NPs changing from red to blue, which was readily seen by the naked eye. The color change and surface plasmon resonance (SPR) absorption were used to monitor Cr (III) and Cr (VI) levels. Under the optimal assay conditions, good linear relationship was obtained, and the detection limit of Cr (III) and Cr (VI) were 0.016 μM and 0.009 μM in standard aqueous solution, respectively. Furthermore, the colorimetric method exhibited a good selectivity over other metal ions and was successfully applied to detect Cr (III) and Cr (VI) in real water samples.
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JOURNAL OF COLLOID AND INTERFACE SCIENCE
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2013
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IF 3.172
Guangfang Li,Fan Qin,Runming Wang,Shengqiang Xiao,Hongzhe Sun,Rong Chen
A facile microwave irradiation method has been successfully developed for the controllable fabrication of BiOX (X = Cl, Br, I) nanostructures in mannitol solution. The morphology and size of BiOX nanostructures could be readily tailored by adjusting the amount of halide, reaction precursor, and mannitol concentration. Mannitol molecule acts as both a capping agent and a cohesive agent in the formation of BiOX nanostructures. A possible two-stage formation mechanism was discussed based on the morphology evolution of BiOI nanostructures obtained in mannitol solution with different concentrations. The as-synthesized BiOX nanostructures exhibit much higher photocatalytic activities than that of commercial TiO 2 . In particular, flower-like BiOX hierarchical nanostructures display the best photocatalytic performance, which is mainly ascribed to their unique hierarchical structure, high BET surface area, and large band gap. Moreover, BiOX nanostructures also demonstrate superior Cr(VI) removal capacity. The Cr(VI) adsorption behavior was also analyzed by the Langmuir and Freundlich adsorption isotherms.
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CATALYSIS COMMUNICATIONS
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2015
·
IF 3.699
Yong Liu,Shao-Yi Jia,Song-Hai Wu,Ping-Li Li,Chun-Jiang Liu,Yi-Ming Xu,Feng-Xiang Qin
Highly dispersed metallic nanoparticles immobilizing inside the pores of MIL-101(Cr) were prepared using double solvent method (DSM). The particle size of Au, Ag, Pd, and AuPd NPs were 2.9 ± 0.7 nm, 1.9 ± 0.6 nm, 2.1 ± 0.6 nm and 2.8 ± 0.7 nm, respectively. The catalytic activity determined by the reduction of p-nitrophenol by NaBH 4 to p-aminophenol of Pd and AuPd prepared by DSM is 9.6 and 8.3 times higher than that of Pd and AuPd prepared by conventional impregnation method. The structure and activity of the catalysts prepared by DSM have no significant changes after three cycles.
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INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
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2013
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IF 2.206
Zhiqiao He,Qiaolan Cai,Ming Wu,Yuanqiao Shi,Huiying Fang,Lingdan Li,Jiancheng Chen,Jianmeng Chen,Shuang Song
In the present work, reduction of Cr(VI) induced by UV–visible light in aqueous solution was investigated. The aqueous medium contained TiO2 nanosheets and no additional reducing agents or hole scavengers. A hydrothermal method was used to synthesize fluorinated TiO2 nanostructures with various percentages of exposed {001} facets and initial F/Ti ratios. Fluorine-free TiO2 nanosheets were obtained by washing the TiO2 samples with NaOH solution. The surface fluorination facilitates the adsorption process by increasing the number of surface OH groups generated. Moreover, fluorination efficiently inhibits the recombination of photogenerated electron–hole pairs. The {001} facets have an indirect role in the photocatalytic reduction of Cr(VI) because oxidative dissolution of H2O occurring on {001} facets and Cr(VI) reduction occurring on {101} facets are simultaneous reactions. The optimal ratio of exposed {001} to {101} was found to be ∼72:18.
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JOURNAL OF THE ELECTROCHEMICAL SOCIETY
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2014
·Vol. 161
·期 9
·H573
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IF 2.859
Yong Kong,Ting Zhou,Yong Qin,Yongxin Tao,Yong Wei
Graphene plays a decisive role in the electrocatalytic copolymerization of aniline and m-aminophenol. The electrochemical activity of the obtained copolymer has an improved pH dependence compared with polyaniline. The results of Fourier transform infrared spectroscopy, electrochemical quartz crystal microbalance, atomic force microscope, and ultraviolet-visible spectroscopy reveal the ion exchange behaviors of the copolymer, indicating that it could be a potential candidate for the effective electrochemical removal of toxic Cr(VI) from industrial wastewater.
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RSC Advances
·
2016
·Vol. 6
·期 32
·27039-27046
·
IF 3.289
Honglin Yao,Qianqian Ding,Hongjian Zhou,Zhenfu Zhao,Gang Liu,Guozhong Wang
In this study, mesoporous amino-group functionalised iron/silica hollow spheres (Fe/SiO2–NH2 HSs) were successfully developed as a magnetic absorbent for the highly effective removal of Cr(VI) ions. The Fe/SiO2–NH2 HSs were synthesized using monodispersed silica colloids as a chemical template, followed by a one-pot hydrothermal treatment, hydrogen reduction and surface modification with an amino silane coupling agent. The Fe/SiO2–NH2 HSs have a diameter of ca. 950 nm and a shell thickness of ca. 60 nm, and the surfaces were composed of Fe and SiO2 units with amino functional groups. Meanwhile, the ferromagnetic property endowed them with easy recyclability for practical applications. The Fe/SiO2–NH2 HSs exhibited significantly improved ability to remove pollutant Cr(VI) and methyl orange. The removal percentage of Cr(VI) (8 mg L−1) could reach 98.3% in just 5 min using Fe/SiO2–NH2 HSs; however, only 10% of Cr(VI) were removed using the unmodified samples. XPS analysis suggested that the removal of Cr(VI) was attributed to the adsorption and reduction synergistic process of the Fe/SiO2–NH2 HSs. During the process, an electrostatic attraction occurred between the positively charged amino-groups and the negatively charged pollutant species in the aqueous solution, and adsorbed Cr(VI) ions were reduced to Cr(III) species by the iron of Fe/SiO2–NH2 HSs.
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CHEMICAL ENGINEERING JOURNAL
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2017
·
IF 6.216
Si-Hai Zhang,Mei-Feng Wu,Ting-Ting Tang,Qiu-Ju Xing,Cai-Qing Peng,Fei Li,Hui Liu,Xu-Biao Luo,Jian-Ping Zou,Xiao-Bo Min,Jin-Ming Luo
In this study, nanoscale zero-valent iron (nZVI) with a considerably high surface area (182.97 m 2 ·g −1 ) and featured morphology of chain structure has been synthesized and well characterized. The as-prepared nZVI on can totally remove Cr(VI) under anoxic condition after 20 min reaction, whereas only 43% of Cr(VI) was removed after 60 min reaction under oxic condition. Noteworthily, the nZVI exhibits excellent removal capacity of Cr(VI) (123.85 mg/g) and fast removal rate (0.017 g·mg −1 ·min −1 ), much better than those reported in the literatures except for that reported by Li et al. (2008) [1] . Experimental results have confirmed that only FeCr 2 O 4 with low compactness was generated under anoxic and acidic conditions in the new process. And it is evident that the formation of the passivation layer which contains oxides and hydroxides (or (oxy)hydroxides) of iron and chromium were well hindered. Furthermore, the as-prepared nZVI has shown fast removal of traced Cr(VI) from the Cr-spiked drinking water or actual Cr-contaminated lake water. Accordingly, we proposed a new reaction process of Cr(VI) reduction by nZVI under anoxic condition. And we firstly make clear the detailed process of Cr(VI) removal by the as-prepared nZVI via X-ray photoelectron spectrometer (XPS) analysis in time scale. Meanwhile, the excellent Cr(VI) removal performance of the as-prepared nZVI could be attributed to (i) the high surface area, (ii) large quantity of active sites of nZVI, and (iii) fast electron transfer from the nZVI/FeCr 2 O 4 to Cr(VI). The present work not only provides the potential materials for the application to the rapid and high-efficient removal of Cr(VI) from aqueous solution, but also proposed a new avenue for hindering the passivation of Fe 0 . And a detailed mechanism of the Cr(VI) removal by nZVI was proposed for the first time.
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SENSORS AND ACTUATORS B-CHEMICAL
·
2016
·
IF 4.758
Wan Wang,Hua Bai,Haiyu Li,Qing Lv,Qing Zhang,Ning Bao
Fabrication of disposable gold working electrodes in bulk is desirable for their extensive application in electrochemical detection . In this paper the gold film electrodes were prepared by sputtering the gold film with the thickness of ∼12 nm on the double sided conductive carbon tape. The gold film coated carbon tape could be used like stickers with small square pieces and attached on ITO glass for fabrication of disposable gold film electrodes. The electrochemical responses of the gold film modified electrodes on Cr(VI) in acidic solutions were similar to previous gold electrodes, suggesting the similar mechanism as before. Cr(VI) could be determined by the amperometric method with the detection limit of 0.7 μg L −1 (0.013 μM), which was significantly improved compared with previously reported disposable gold-based electrodes. The batch-by-batch (n = 20) reproducibility of the fabricated electrodes was 7.3% at 50 μg L −1 and 3.8% at 5.0 mg L −1 , respectively. The disposable electrodes could be applied to quantify Cr(VI) in real samples including plastics, tap water and lake water with results in agreement with those obtained with HPLC-ICP-MS. This study provides a simple and effective alternative for preparation of disposable gold film electrodes.
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APPLIED SURFACE SCIENCE
·
2016
·
IF 3.15
Yuanfeng Pan,Pingxiong Cai,Madjid Farmahini-Farahani,Yiduo Li,Xiaobang Hou,Huining Xiao
Pentaerythritol (PER) was esterified with 2-bromoisobutyryl bromide to synthesize a four-arm initiator 4Br-PER for atom transfer radical polymerization (ATRP). Star-shaped copolymers (P(AM- co -DMAEMA) 4 , CSP) were prepared via ATRP using dimethyl aminoethyl methacrylate (DMAEMA) and acrylamide (AM) as comonomers, while Br-PER and CuBr/2,2′-bipyridine (BPY) as the initiator and the catalyst, respectively. The resulting four-arm initiator and star-shaped polymer (CSP) were characterized with FT-IR, 1 H NMR and Ubbelohde viscometry. Alkaline clay (AC) was immobilized with CSPs to yield amino groups, and the cationic star polymer-immobilized alkaline clay (CSP-AC) was applied to remove Cr(VI) from the aqueous solution in batch experiments. Various influencing factors, including pH, contact time and immobilization amount of CSP on adsorption capacity of CSP-AC for Cr(VI) were also investigated. The results demonstrated that Cr(VI) adsorption was highly pH dependent. The optimized pH value was 4.0. The adsorption isotherms of the adsorbent fit the Langmuir model well, with the maximum adsorption capacity of 137.9 mg/g at 30 °C. The material should be a promising adsorbent for Cr(VI) removal, with the advantages of high adsorption capacity.
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Frontiers in Microbiology
·
2016
·
IF 4.165
Han Rui,Li Fangbai,Liu Tongxu,Li Xiaomin,Wu Yundang,Wang Ying,Chen Dandan
It is widely recognized that the outer membrane c-type cytochromes (OM c-Cyts) of metal-reducing bacteria play a key role in microbial metal reduction processes. However, the in situ redox status of OM c-Cyts during microbial metal reduction processes remain poorly understood. In this study, diffuse-transmission UV/Vis spectroscopy is used to investigate the in situ spectral reaction of Cr(VI) reduction by c-Cyts in intact Shewanella oneidensis MR-1 cells under different incubation conditions. The reduced c-Cyts decreased transiently at the beginning and then recovered gradually over time. The Cr(VI) reduction rates decreased with increasing initial Cr(VI) concentrations, and Cr(III) was identified as a reduced product. The presence of Cr(III) substantially inhibited Cr(VI) reduction and the recovery of reduced c-Cyts, indicating that Cr(III) might inhibit cell growth. Cr(VI) reduction rates increased with increasing cell density. The highest Cr(VI) reduction rate and fastest recovery of c-Cyts were obtained at pH 7.0 and 30∘C, with sodium lactate serving as an electron donor. The presence of O2 strongly inhibited Cr(VI) reduction, suggesting that O2 might compete with Cr(VI) as an electron acceptor in cells. This study provides a case of directly examining in vivo reaction properties of an outer-membrane enzyme during microbial metal reduction processes under non-invasive physiological conditions.
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RSC Advances
·
2016
·Vol. 6
·期 98
·95469-95475
·
IF 3.289
Lingli Bu,Jingdong Peng,Huanjun Peng,Shaopu Liu,Huan Xiao,Dan Liu,Ziyu Pan,Yu Chen,Fang Chen,Yan He
Chromium(VI) is proved to be highly carcinogenic and mutagenic, thus sensitive and rapid sensors for monitoring Cr(VI) are in urgent demand. In this work, a facile fluorescent assay for the sensitive and selective detection of Cr(VI) was proposed based on static quenching combined with inner filter effect (IFE) using phosphate functionalized carbon dots (PCDs) as nanoprobes. A good linear quenching was observed in the range of 1.0–400 μM with a detection limit of 0.24 μM (σ/S = 3) under the optimized conditions. The nanoprobe was employed for detecting Cr(VI) in real water samples including river water and tap water with satisfactory recovery. Moreover, with the addition of Cr(VI), the color changes of PCDs can be easily observed by the naked eye under a UV lamp. Based on this, Cr(VI) test papers were fabricated for spot quick detection of Cr(VI).
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