JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
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2023
·
IF 10.9
Chao Liu,Wen Xiao,Xingyu Liu,Qiang Wang,Jiawei Hu,Siyuan Zhang,Jianguang Xu,Qinfang Zhang,Zhigang Zou
As a highly toxic heavy metal, Cr(VI) reduction by developing high-efficiency photocatalysts is of great significance. Herein, we firstly design few-layer Ti 3 C 2 MXene (FTM) by the hand-operated shaking, showing dual advantages of structural stability and more exposed reactive sites. Then, a refluxed process is performed to fabricate FTM/CaIn 2 S 4 (FTC) composites, where 2D CaIn 2 S 4 (CIS) nanoplates are closely connected with 2D FTM to form Schottky junction. The optimal 1-FTC with the FTM/CIS mass ratio of 1 wt.% exhibits the highest activity toward photocatalytic Cr(VI) reduction under visible light. It is well elucidated that the broadened light absorption range and promoted charge carrier separation rate induced by the introduction of FTM are responsible for improving photocatalytic activity of CIS. During Cr(VI) photoreduction, 1-FTC possesses excellent photo-stability and reusability. The effects of catalyst mass, coexisting ions, water sources and pH values on the Cr(VI) photoreduction efficiency are investigated. Photogenerated • O 2 − and e − are the main radical species accounting for Cr(VI) photoreduction over 1-FTC. The photocatalytic mechanism along with Cr(VI) removal pathway is exploited. This work may provide some insights into constructing FTM-based Schottky junctions for the efficient water purification.
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CHEMICAL ENGINEERING RESEARCH & DESIGN
·
2023
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IF 3.9
Honghui Xiong,Jinglei Liu,Yongjun Zhang,Hao Wang,Enhao Sun
To reduce the coke formation, a novel Al/Si/Cr/Ce composite ceramic coating was prepared on the surface of the Cr 25 Ni 35 Nb alloy substrate by pack cementation. The microstructure, phase composition, surface morphology and element distribution of substrate and coating were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The results reveal that the outer layer of the coating forms a protective layer with a high proportion of AlN and Cr 3 Si and trace amounts of Ce. The inter-diffusion layer is mainly aluminide coating (AlNi and AlFe) and transition layer contains a small amount of AlN. The anti-coking performance of the coating was assessed using naphtha steam cracking. To study coking behavior, the morphology and microstructure of the coke layer were analyzed and characterized by SEM and Laser Micro-Raman Spectrometer. The coke layer on uncoated sample has a higher focal density and is more likely to spall and peel off when subjected to coking experiment. A large number of filamentous and granular cokes appear on the surface of the uncoated sample, whereas only less granular cokes appear on the surface of the coated sample, and the coke on the uncoated sample has a more disordered and amorphous carbon structure. The coating significantly inhibited the growth of filamentous coke and reduced coke accumulation.
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JOURNAL OF APPLIED POLYMER SCIENCE
·
2023
·Vol. 140
·期 25
·e53978
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IF 3
Xiaocan Zhang,Huixiao Ma,Tong Pei,Ruochen Zhang,Yiran Liu
Incorporating phosphotungstic acid (HPW) in proton exchange membranes (PEMs) is an effective way to improve proton conductivity, but its leakage remains a problem. It can be solved by immobilizing acid in membranes to enhance the stability of PEMs. Herein, we proposed a novel sulfonated poly(ether ether ketone) (SPEEK) composite membrane (SPEEK/HPW@MIL) that was prepared by blending amino-modified MIL-101(Cr) to anchor HPW. In this work, HPW was anchored through hydrogen bond to minimize its leakage and enhance the overall compatibility. The incorporation of MIL-101(Cr)-NH 2 also helped lower the swelling ratio and improve the dimensional stability. Compared with pristine SPEEK and SPEEK/MIL membrane, the proton conductivity of the SPEEK/HPW@MIL composite membrane increased by 26% and 14%, respectively. The superior performance recommended a promising conception for anchoring HPW in PEMs.
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CERAMICS INTERNATIONAL
·
2023
·
IF 5.2
Yukun Li,Yongfu Liu,Zhaohua Luo,Zehua Liu,Svenja Hanson,Chengheng Pang,Hui Lin,Haiming Qin,Jun Jiang
Ce/Mn/Cr: Y 3 Al 5 O 12 transparent ceramics with a pure garnet structure and a high color rendering index were prepared by a solid-state reaction method. Mn 2+ and Cr 3+ enhance the emission between 500 and 700 nm and expand the conventional Ce: YAG phosphors spectrum. The Ce 3+ can work both, as activators and sensitizers, and the intense energy transfer from Ce 3+ to Mn 2+ /Cr 3+ is realized through the non-radiative and radiative processes. In the sample with the optimized doping concentration the high color rendering index (CRI) value of 75.3 can be achieved under a 450 nm laser diode excitation. The chromaticity coordinates can be tuned from (0.3125, 0.3232) to (0.2917,0.2851) by varying the doping concentration. With the increasing Mn 2+ /Cr 3+ doping concentration, the lifetime of Ce 3+ , quantum efficiency and luminous efficiency are all gradually decreased. This work effectively offers a scheme for realizing the high color rendering performance of phosphor-converted transparent ceramics in white LEDs/LDs.
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CHEMOSPHERE
·
2023
·
IF 8.8
Yang-xiao-xiao Shi,Jia-qi Cui,Feng Zhang,Ke-wei Li,Jun Jiang,Ren-kou Xu
Hexavalent chromium (Cr(VI)) is a toxic heavy metal and its mobility and bioaccessibility in soils are influenced by soil properties. In this study, the soil pH and organic carbon contents of Ultisol , Alfisol , and Inceptisol were adjusted before they were polluted with 230 mg kg −1 Cr(VI). Alkaline digestion, sequential extraction, and an in vitro experiment were conducted to study the valence state, species, and bioaccessibility of Cr in the soils. The results showed that a high soil pH was not favorable for reduction of Cr(VI); therefore the Cr(VI) and exchangeable Cr contents were positively related to soil pH. Soil organic carbon promoted the reduction of Cr(VI). Almost all Cr(VI) was reduced to Cr(III) when the soil organic carbon content reached 10 g kg −1 . Chromium bioaccessibility in simulated gastric and intestinal phase solutions was influenced by Cr(VI) and Cr(III) adsorption/desorption, dissolution/precipitation, and redox reactions. Chromium bioaccessibility differences between the gastric and intestinal phases were associated with the Cr(VI)/Cr(III) ratio. Acidic conditions and a high organic carbon content promoted the conversion of Cr(VI) to Cr(III). When soil pH was increased from 4.01 to 5.85, Cr(VI) in Alfisol without the addition of humic acid increased from 96.38 to 174.78 mg kg −1 , the exchangeable Cr proportion increased from 9.7% to 22.6%, and Cr bioaccessibility increased from 41.29% to 49.14% in the gastric phase and from 41.32% to 48.24% in the intestinal phase. When the organic carbon content increased from 3.95 to 9.28 g kg −1 in Alfisol, Cr(VI) content decreased from 167.66 to 20.52 mg kg −1 , which led to a decrease in Cr bioaccessibility from 49.15% to 13.8% in the gastric phase and from 45.85% to 7.67% in the intestinal phase. Therefore, acidic conditions and increasing soil organic carbon levels can reduce the health risk posed by Cr in soils.
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International Journal of Electrochemical Science
·
2023
·
IF 1.5
Yuhan Yao,Zhaolin Zhan,Jianxiong Liu,Xiao Wang,Xiaohua Yu,Ju Rong
Response surface methodology (RSM) was used in this study to determine the optimum operating conditions for the reduction of galvanized sheet corrosion using a Cr-free passivation films. Passivation films layer with strong corrosion resistance was formed on the surface of galvanizing which was impregnated in chromium-free passivating agent. Furthermore, the RSM was used to ascertain the main and interactive effects (deviation between the experimental and theoretical values: 0.12%). The coefficient of determination (R 2 ) showed that the RSM approach was appropriate for optimization of the Cr-free passivator. Silane coupling agent, ammonium molybdate, nanosilica, and tannic acid played a key role in changing the corrosion area and potential. The results revealed that, compared with Cr 6+ passivation, Cr-free passivation yielded considerably more homogeneous and smoother surfaces (surface roughness of Cr-free passivation film: 0.54 μm). In addition, the properties of the zinc coating after Cr- free passivation were clearly superior to those of the zinc coating subjected to the conventional Cr 6+ passivation treatment. E corr, current density, and polarization resistance values of this superior coating were -1073 mV, 0.017 A cm -2 , and 989.2 Q, respectively. This study can serve as an experimental and a theoretical guide for the development of Cr-free passivation films.
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SEPARATION AND PURIFICATION TECHNOLOGY
·
2023
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IF 8.6
Jianqing Ma,Nanzhengfang Jia,Huixia Jin,Sijing Yao,Kefeng Zhang,Yin Kai,Wenliang Wu,Yuezhong Wen
The removal of Cr(VI) from wastewater still faces many challenges. This study reports on chitosan-induced synthesis of few-layer MoS 2 /Fe-doped biochar (Mo-Fe 0.5 -CS) with dual applications in Cr(VI) removal. Using chitosan as a soft template, the MoS 2 in the composite had only about 3 layers with an interlayer spacing greater than that of pure MoS 2 , while Fe was embedded in the carbon skeleton in the form of 6-coordination with O/N. The Mo-Fe 0.5 -CS composite showed high affinity for Cr(VI), with rapid adsorption reaching 100% removal within 15 min for a single solution of Cr(VI). It follows the Langmuir isotherm model with a maximum adsorption capacity of up to 180 mg/g. Furthermore, the Mo-Fe 0.5 -CS composite demonstrated catalytic activity for Fenton-like reactions, which allowed for the simultaneous removal of organic pollutants and Cr(VI). In a mixture solution of Cr(VI) and Acid Red 73 (AR73), the removal efficiencies using Mo-Fe 0.5 -CS and H 2 O 2 in 30 min were 99.7% and 96.6%, respectively. The MoS 2 acted as a cocatalyst to improve the reduction of Fe(III), and the catalysis of Cr(VI) also contributed to the removal of AR73 to a certain extent. Even at pH 10, the system was effective due to the 1 O 2 produced in the reaction and the acidic microenvironment constructed by unsaturated S atoms. These findings provide insights into the effective removal and utilization of Cr(VI) in wastewater treatment .
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JOURNAL OF COLLOID AND INTERFACE SCIENCE
·
2023
·
IF 9.9
Chao Liu,Wen Xiao,Guiyun Yu,Qiang Wang,Jiawei Hu,Chenghao Xu,Xinyi Du,Jianguang Xu,Qinfang Zhang,Zhigang Zou
Developing efficient heterojunction photocatalysts that have a high charge carrier separation rate and improved light-harvesting capacity is a crucial step in solving energy crisis and reducing environmental pollution. Herein, we synthesized few-layered Ti 3 C 2 MXene sheets (MXs) by a manual shaking process, and combined with CdIn 2 S 4 (CIS) to construct novel Ti 3 C 2 MXene/CdIn 2 S 4 (MXCIS) Schottky heterojunction through a solvothermal method. The strong interface between two-dimensional (2D) Ti 3 C 2 MXene and 2D CIS nanoplates led to enhanced light-harvesting capacity and promoted charge separation rate. Additionally, the presence of S vacancies on the MXCIS surface helped to trap free electrons. The optimal sample, 5-MXCIS (with 5 wt% MXs loading), exhibited outstanding performance for photocatalytic hydrogen (H 2 ) evolution and Cr(VI) reduction under visible light due to the synergistic effect of enhanced light-harvesting capacity and charge separation rate. The charge transfer kinetics was thoroughly studied using multiple techniques. The reactive species of • O 2 − , • OH and h + were generated in 5-MXCIS system, and e − and • O 2 − radicals were found to be the main contributors to Cr(VI) photoreduction. Based on the characterization results, a possible photocatalytic mechanism for H 2 evolution and Cr(VI) reduction was proposed. On the whole, this work provides new insights into the design of 2D/2D MXene-based Schottky heterojunction photocatalysts for boosting photocatalytic efficiency.
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LANGMUIR
·
2023
·
IF 3.9
Zishen Lin,Fobang Liu,Chunli Zheng,Aibin Zhu,Xiaowei Ma,Yuanzhe Peng,Chi He
Amorphous zero-valent iron (AZVI) has attracted wide attention due to its high-efficiency reduction ability. However, the effect of different EDA/Fe(II) molar ratios on the physicochemical properties of the synthesized AZVI requires further investigation. Herein, series of AZVI samples were prepared by changing the molar ratio of EDA/Fe(II) to 1/1 (AZVI@1), 2/1 (AZVI@2), 3/1 (AZVI@3), and 4/1 (AZVI@4). When the EDA/Fe(II) ratio increased from 0/1 to 3/1, the Fe0 proportion on the AZVI surface increased from 26.0 to 35.2% and the reducing ability was enhanced. As for AZVI@4, the surface was severely oxidized to form a large amount of Fe3O4, and the Fe0 content was only 74.0%. Moreover, the removal ability of Cr(VI) was in the order AZVI@3 > AZVI@2 > AZVI@1 > AZVI@4. The isothermal titration calorimetry results revealed that the increase of the molar ratio of EDA/Fe(II) would lead to the stronger complexation of EDA with Fe(II), which resulted in the gradual decrease of the yield of AZVI@1 to AZVI@4 and the gradual deterioration of water pollution after the synthesis. Therefore, based on the evaluation of all indicators, AZVI@2 was the optimal material, not only because its yield was as high as 88.7% and the secondary water pollution level was low, but most importantly, the removal efficiency of Cr(VI) by AZVI@2 was excellent. Furthermore, the actual Cr(VI) wastewater with the concentration of 14.80 mg/L was treated with AZVI@2, and the removal rate of 97.0% was achieved after only a 30 min reaction. This work clarified the effect of different ratios of EDA/Fe(II) on the physicochemical properties of AZVI, which provided insights for guiding the reasonable synthesis of AZVI and is also conducive to investigating the reaction mechanism of AZVI in Cr(VI) remediation.
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INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
·
2023
·
IF 8.2
Chunzi Xu,Yunlan Xu,Dengjie Zhong,Haixing Chang,Jiaxin Mou,Hui Wang,Hongyu Shen
In order to improve the stability, electrostatic interaction and ion exchange ability of chitosan for Cr (VI) removal, it is an effective strategy to introduce polyvalent metal ions and polymers into chitosan molecular chain through crosslinking. In this paper, Zr 4+ and glutaraldehyde crosslinked polyethyleneimine functionalized chitosan (CGPZ) composite was successfully synthesized and characterized by XRD, SEM, FTIR , BET, and XPS . The results showed that polyethyleneimine was successfully grafted onto chitosan by Schiff base reaction, while the appearance of Zr O and Zr N bonds verified the successful preparation of CGPZ. The monolayer maximum adsorption capacity of Cr(VI) by CGPZ was 593.72 mg g −1 at 298 K and t = 210 min. The removal efficiency of 100 mg L −1 Cr(VI) reached 95.7 %. The thermodynamic, isotherm and kinetic results show that the adsorption process of Cr (VI) by CGPZ is a spontaneous endothermic process controlled by entropy, which accords with Freundlich model and pseudo-second-order kinetic model. The regeneration experiments show that both HCl and NaOH can effectively desorb Cr(III) and Cr(VI) from the adsorbent surface, and the adsorbent has good acid-base resistance and regeneration performance. The removal of Cr(VI) mainly involves electrostatic attraction, ion exchange, reduction and complexation. CGPZ can synergistically adsorb Cr(VI) by electrostatic interaction of -NH 2 /-C=N and ion exchange of Cl − ion in the center of Zr, then reduce Cr(VI) to Cr(III) (45.4 % at pH = 2.0) by the -OH group on its surface, and chelate Cr(III) through COO- and -NH- groups.
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JOURNAL OF CHEMICAL AND ENGINEERING DATA
·
2019
·
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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APPLIED CATALYSIS B-ENVIRONMENTAL
·
2019
·
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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