LANGMUIR
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2019
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IF 3.683
Yan Xiong,Jie Chen,Ming Duan,Xiang Li,Jun Li,Can Zhang,Shenwen Fang,Rui Liu,Run Zhang
The investigation of adsorption performance at the adsorbent surface can help to reveal the treatment mechanism and improve the treatment efficiency of adsorption technology for heavy metal ions (HMIs). This work developed a methodology to investigate the adsorption behavior of HMI Cr(VI) at the silica surface by confined near-field evanescent wave (CNFEW) measurement. A silica optical fiber (SOF) was used as the adsorption substrate and light waveguide element to integrate both Cr(VI) adsorption and CNFEW production on its surface. According to the sensitive CNFEW response, the adsorption behavior of Cr(VI) was in situ monitored and real-time evaluated. The thermodynamic information of adsorption equilibrium constant (Kads) and adsorption free energy (ΔG) and dynamic information of the apparent adsorption rate (vads) and adsorption time (tads) were obtained through Langmuir isotherm and kinetic fitting, respectively. Different reaction performances between Cr(VI) and adsorption sites were successfully differentiated, evaluated, and characterized. A site-decided-mechanism was therefore presented to describe the surface interaction process for Cr(VI), which including fast adsorption on type I Si–O– site through electrostatic attraction with and slow adsorption on type II Si–OH site through coordinative interaction with ΔGSiOH–Cr(VI)II = −26.18 kJ mol–1. The adsorption mechanism of Cr(VI) at the SOF silica surface was furthermore verified by zeta potential analysis, Fourier transform infrared investigation, and fluorescence imaging. Unlike conventional ex situ or in bulk detection, the present CNFEW-based approach targets the “localized” adsorption of Cr(VI) adsorbed to the solid adsorbent surface. Consequently, our work favorably constructs a surface platform and provides new insights on understanding the adsorption mechanism for HMIs.
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JOURNAL OF ENVIRONMENTAL MANAGEMENT
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2019
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IF 4.865
Yuyan Liu,Saran P. Sohi,Siyuan Liu,Junjie Guan,Jingyao Zhou,Jiawei Chen
To address inorganic and organic contaminants in the environment, economic new adsorbents are required. Here we test magnetic biochar for efficient capture of the typical pollutants Cr(VI) and trichloroethylene (TCE) from solution. We used a simple synthesis using 2M FeCl 3 solution and peanut hull biomass to prepare magnetic ZVI biochar at alternate pyrolysis temperatures between 650 and 800 °C. The physicochemical character of the biochars were assessed using X-ray diffraction (XRD) and the Brunauer-Emmett-Teller (BET) method for surface area. The magnetic ZVI biochars were highly effective in the removal of Cr(VI) and TCE. The most effective magnetic biochar produced at 800 °C was further examined using scanning electron microscopy (SEM), revealing a high and even loading of ZVI. After sorption the same magnetic biochar was examined by X-ray photoelectron spectroscopy (XPS) to ascertain the underlying mechanisms. The dependence of Cr(VI) capture on solution pH was also examined. Our interpretation suggests that when pH < pH zpc (2.5) electrostatic attraction and redox reactions dominated the adsorption of Cr(VI). When pH > pH zpc the removal process was controlled mainly by redox reaction and substitution of chromate anions for hydroxyl ( OH) groups. Capture of TCE in contrast involved hydrophobic partitioning, pore-filling and reductive degradation. Overall our results suggest that simple synthesis of magnetic ZVI biochar could offer an economic and effective option to address water contamination issues.
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APPLIED CATALYSIS B-ENVIRONMENTAL
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2019
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IF 14.229
Ranran Yuan,Cailiang Yue,Jinli Qiu,Fuqiang Liu,Aimin Li
TiO 2 @NH 2 -MIL-88B(Fe) heterostructures (TMFe-x) were successfully synthesized and used in an efficient sunlight-driven reduction towards Cr(VI) in a neutral aqueous media. Further, the prepared TMFe-x heterostructures exhibited higher photocatalytic activity when compared with those exhibited by pure TiO 2 and NH 2 -MIL-88B(Fe) under simulated sunlight irradiation. The optical TiO 2 modification content was determined to be 10 wt.% (TMFe-b), with 98.6% Cr(VI) being converted to Cr(III) within 35 min using ammonium oxalate as the hole scavenger at pH = 7. In neutral conditions, the kinetic rate constant (0.0878 min −1 ) was five times larger than the published values. Additionally, the photocatalytic performance of TMFe-b was maintained and Fe leaching was observed to be negligible after the completion of four reaction cycles. The superior photocatalytic property can be attributed to the high photoelectron-hole separation and migration efficiency. Subsequently, TMFe-b achieved Cr(VI) reduction under neutral conditions by capturing hydrogen from the water molecules or the hole scavengers. The photoelectrons and superoxide radicals were the main active species. Furthermore, TMFe-b was able to efficiently eliminate various pollutants through photocatalytic oxidation and reduction. This study suggests a novel strategy for the preparation of environmentally stable and efficient MOF-based photocatalysts to efficiently eliminate various pollutants. Further, there is a huge potential for the practical application of this technology to water purification .
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JOURNAL OF CHEMICAL AND ENGINEERING DATA
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2019
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IF 2.298
Wenjun Tu,Weiquan Cai,Yihong Jiang,Fanxin Kong,Jiabin Zhou
The rare-earth elements (La, Ce, and Y)-modified SiO2 films for effective Cr(VI) removal from electroplating effluent were synthesized by a convenient sol–gel method successfully. X-ray diffraction, Fourier transform infrared spectra (FT-IR), scanning electron microscope, energy-dispersive system, and X-ray photoelectron spectroscopy (XPS) were applied to characterize their physicochemical properties. The adsorption isotherms showed that the adsorption capacity of SiO2 modified by La3+ (64.43 mg g–1) is the best, followed by Ce3+ (53.45 mg g–1) and Y3+ (47.83 mg g–1) because of the different ion-exchange capacities of La/Ce/Y–(OH), whereas that of SiO2 film without modification is only 38.54 mg g–1. Their adsorption processes could be well depicted by the pseudo-second-order kinetic model. The thermodynamics study showed that the adsorption process of the La/SiO2 film is spontaneous. The adsorption mechanism includes the ion exchange and electrostatic effect. Furthermore, the conversion of Cr(VI) to Cr(III) during the in situ reduction process was verified by both macro (optical photographs) and micro (FT-IR and XPS) levels. Importantly, the La/SiO2 film showed high adsorption selectivity and high removal efficiency of 97.4% toward Cr(VI) from initial concentration of 41.7 mg L–1 to residual concentration of 1.1 mg L–1 in the real electroplating effluent, indicating its potential industrial value for pretreatment of heavy metal wastewater.
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INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
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2019
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IF 4.784
Jian Xia,Xiaojuan Lei,Yuqin Lu,Shilin Liu,Xiaogang Luo
In this work, the coagulation mechanism of the cellulose/metal nanohybrids and the binding mode with Cr (VI) are deeply described. Nanohybrids with 3D porous networks were prepared from cellulose/Fe 2 O 3 -SO 3 H solutions through a simple one-step coagulation process in NaCl aqueous solutions. The structure and properties of nanohybrids were characterized by SEM, EDS, XRD, FTIR, and XPS. The cellulose/metal nanohybrids have a langmuir maximum adsorption capacity of 11.46 mg/g. The dissolved metal nanoparticles could form strong hydrogen bonding with cellulose by breaking the intermolecular hydrogen bonds between the polymer molecules. The porous networks of cellulose/metal nanohybrids provided multiple adsorption sites for Cr 2 O 7 2− anion through Fe O … Cr interactions. The cooperation between cellulose and Fe 2 O 3 -SO 3 H nanoparticles makes the hybrids exhibiting a satisfactory selectivity and affinity for Cr (VI). The cellulose/metal nanohybrids selectively interacted with Cr 2 O 7 2− via Fe atom from Fe 2 O 3 and oxygen atom from SO 3 − groups. The Cr (VI) adsorption occurred via a two-step process, the first of them was the initial adsorption of Cr 2 O 7 2− on cellulose/metal nanohybrids surface, followed by the rearrangement of Cr 2 O 7 2− molecules and the consecutive growth of Cr 2 O 7 2− aggregate layers.
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Catalysts
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2018
·Vol. 8
·期 6
·251
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IF 3.465
Shengyan Pu,Yaqi Hou,Hongyu Chen,Daili Deng,Zeng Yang,Shengyang Xue,Rongxin Zhu,Zenghui Diao,Wei Chu
For the purpose of establishing a simple route to prepare a metal-semiconductor hybrid catalyst efficiently and reduce its cost through precise doping noble metals. In this study, ultra-trace silver doped TiO2photocatalysts were fabricated via a “green” ultrasonic impregnation-assisted photoreduction strategy in an ethanol system, and its photocatalytic performance was systematically investigated by utilizing Cr(VI) as the model contaminant. A schottky energy barrier was constructed in Ag@TiO2, which served as a recombination center and possessed superior photocatalytic activity for Cr(VI) reduction. The obtained catalysts exhibited a significante−/h+separation efficiency which directly led to an obvious photocatalytic property enhancement. Then, the resultant Ag@TiO2(0.06 wt %, 30 min irradiation) showed about 2.5 times the activity as that of commercial P25 NPs for Cr(VI) degradation. Moreover, after five cycles, it still maintained considerably high catalytic ability (62%). This work provides a deep insight into preparation techniques of metal-semiconductor photocatalyst and broadens their application prospect.Keywords:Ag@TiO2;Cr(VI) reduction;in-situ photoreduction;ultrasonic impregnation;ultra-trace silver
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Nanomaterials
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2018
·Vol. 8
·期 11
·937
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IF 3.504
Haiyan Yang,Liang Jiang,Yizhou Li,Guoqing Li,Yepeng Yang,Jiao He,Jiaqiang Wang,Zhiying Yan
In sharp contrast to conventional photosensitization methods in which the organic pigments were often adsorbed, herein we present a study on natural vegetable pigment inserted TiO2aerogel nanocomposites and we directly use red cabbage anthocyanin (RCP) as a structure-directing agent. It was found that pure TiO2aerogel nanocomposite did not exhibit any meaningful activity for photocatalytic reduction of Cr(VI). However, the photocatalytic reduction activity was greatly improved by the RCP inserted TiO2aerogel nanocomposites under visible-light irradiation, which was approximately 2- and 12.3-fold higher than that of TiO2aerogel conventionally photosensitized by RCP and pure TiO2aerogel nanocomposites, respectively. It also exhibited good stability and could be reused at least three times without losing a significant amount of its activity.Keywords:Red cabbage pigment;anthocyanin;TiO2aerogel;photocatalytic activity
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CHEMOSPHERE
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2018
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IF 4.427
Rongrong Zhao,Zuoming Zhou,Xiaodan Zhao,Guohua Jing
A novel amino-functionalized vermiculite (AVT)-supported nanoscale zero-valent iron (AVT-nZVI) was successfully synthesized for Cr(VI) removal from simulated electroplating rinse wastewater. Since the agglomeration and oxidation of nZVI could be weakened and the reaction rate between Cr(VI) and nZVI could be enhanced for the novel AVT-nZVI, an efficient Cr(VI) removal could be achieved. The experimental results showed that 100% of Cr(VI) removal was obtained with AVT-nZVI, whereas only 87.5% was achieved by nZVI after reacting for 60 min with 20.0 mg L −1 Cr(VI) (pH = 5.0). After four cycles, the removal efficiency of Cr(VI) by AVT-nZVI still maintained at above 70%, suggesting that AVT-nZVI exhibited a good performance of reusability. The stability of AVT-nZVI particles was better than nZVI, which was confirmed by the steady-state polarization measurements. Furthermore, the removal of Cr(VI) by AVT-nZVI was proved to be in accordance with the pseudo-second-order adsorption kinetics and Langmuir model. Based on the experiments and characterization, the reaction mechanism of Cr(VI) removal by AVT-nZVI was clarified. The protonated amino groups (-NH 3 + ) on the AVT promoted negative Cr(VI) species to be adsorbed on AVT-nZVI surface. Besides, Cr(VI) was reduced by Fe (0) to Cr(III), which was eventually adsorbed on the surface of AVT-nZVI particles as the Cr(III)-Fe(III) co-precipitates.
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RSC Advances
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2014
·Vol. 4
·期 86
·45920-45929
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IF 3.708
Lisha Tan,Jiang Xu,Xiaoqin Xue,Zimo Lou,Jin Zhu,Shams Ali Baig,Xinhua Xu
Silica-coated magnetite (Fe3O4@SiO2) nanoparticles functionalized with amino, imino and sulfonic groups (Fe3O4@SiO2–mPD/SP) were successfully synthesized via a facile chemical oxidative polymerization of m-phenylenediamine (mPD) and m-sulfophenylenediamine-4-sulfonic acid (SP) monomers, and utilized for selective removal of Pb(II) and Cr(VI) from aqueous solutions. It was revealed by the characterizations that the polymers formed on Fe3O4@SiO2 nanoparticles were the true copolymers with a mPD–SP unit, rather than a mixture of mPD and SP homopolymers. Fe3O4@SiO2–mPD/SP nanocomposites could be easily separated from aqueous solutions within 30 s. The maximum adsorption capacities of Pb(II) (83.23 mg g−1) and Cr(VI) (119.06 mg g−1) on Fe3O4@SiO2–mPD/SP nanocomposites were obtained at the mPD/SP molar ratios of 95 : 5 and 50 : 50, respectively. Moreover, satisfactory selective removal of Pb(II) and Cr(VI) from their mixtures with Cu(II) and Ni(II) ions were exhibited by the Fe3O4@SiO2–mPD/SP (95 : 5) and Fe3O4@SiO2–mPD/SP (50 : 50), respectively. The Pb(II) adsorption equilibrium was reached within 5 min by Fe3O4@SiO2–mPD/SP (95 : 5). The adsorption data of Pb(II) and Cr(VI) were both fitted well to the Freundlich isotherm and followed the pseudo-second-order kinetic model. The adsorption mechanism of Pb(II) and Cr(VI) on Fe3O4@SiO2–mPD/SP nanocomposites included five processes, namely: ion-exchange, complexation adsorption, reduction reaction, electrostatic attraction and physical adsorption. The enhanced adsorption performance of nanoparticle-based magnetic adsorbents for selective removal of heavy metal ions can be achieved with such a copolymerization strategy.
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Environmental Progress & Sustainable Energy
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2013
·Vol. 33
·期 3
·814-823
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IF 0.865
Ruihua Huang,Bingchao Yang,Qian Liu,Yanping Liu
The simultaneous adsorption of phenol and Cr(VI) from aqueous solution onto this activated carbon/chitosan composite was investigated. This composite almost removes phenol and Cr(VI) simultaneously in a pH range of 2–5. The removals of phenol and Cr(VI) reached up to 95% when phenol and Cr(VI) concentrations were less than 50 mg/L and 200 mg/L, respectively. The presence of phenol reduced Cr(VI) adsorption, while the presence of Cr(VI) had no evident effect on phenol adsorption. The adsorption for both Cr(VI) and phenol followed pseudo-second-order kinetics in single or mixedsystems. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 814–823, 2014
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CHEMICAL ENGINEERING JOURNAL
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2016
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IF 5.31
Lei Wang,Changbo Zhang,Feng Gao,Gilles Mailhot,Gang Pan
Algae as an abundant natural biomass, more attention has been paid to explore its potential application in environmental pollutants treatment. This work prepared the algae-TiO 2 /Ag bionano hybrid material by loading algae cells on the ultrafine TiO 2 /Ag chitosan hybrid nanofiber mat. For the first time, the synergistic photocatalytic effect of fresh algae and TiO 2 /Ag nanomaterial was investigated by removal of Cr(VI). The addition of algae significantly improved the photo-removal of Cr(VI) in the system with TiO 2 /Ag hybrid nanomaterial under visible light irradiation. Meanwhile, the photocatalytic mechanism was studied. The photogenerated reactive oxygen species were quantified and the addition of algae apparently decreased the yields of OH to 31.0 μM, while improved the yields of 1 O 2 and O 2 − in the reaction system with TiO 2 /Ag hybrid nanofiber mats. The change of superoxide dismutase activity and malondialdehyde content in algae indicated that TiO 2 /Ag could impose oxidative stress and cause lipid peroxidation in algae cells. During the course of irradiation, algae released substances could act as scavenger for holes, thus inhibited the recombination of hole/electron and enhanced the photocatalytic reduction of Cr(VI) by electrons on TiO 2 surface. Algae was simultaneously photodegraded in the system and the resulting O 2 − , organic free radicals could promote the reduction of Cr(VI). This functional hybrid nanofiber mat was easily recovered and maintained a great photocatalytic activity on the five successive cycles. This algae-photocatalyst hybrid material has promising applications potential in heavy metal removal and organic pollutants treatment.
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JOURNAL OF HAZARDOUS MATERIALS
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2017
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IF 6.065
Sheng Luo,Fan Qin,Yin’an Ming,Huiping Zhao,Yunling Liu,Rong Chen
Hazardous hexavalent chromium removal from wastewater is an urgent issue in industry environmental pollution. In this work, hollow Bi 2 S 3 nanospheres have been successfully synthesized from unique Bi 2 O 3 porous nanospheres via Kirkendall effect through hydrothermal process. It was found that the sulfur source and the initial Bi 2 O 3 templates played key roles in the formation of the uniform morphologies and structures through an anion exchange process. Compared with other Bi 2 S 3 samples, the synthesized hollow Bi 2 S 3 nanospheres exhibited much enhanced photocatalytic ability for Cr(VI) photoreduction. XPS analysis demonstrated that Cr(VI) was reduced to less harmful Cr(III) species over hollow Bi 2 S 3 nanospheres under visible-light irradiation. More importantly, the hollow Bi 2 S 3 nanospheres remained high efficiency and good stability in the recycling Cr(VI) photoreduction, and exhibited remarkable Cr(VI) removal ability in actual electroplating industry wastewater treatment.
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