CHEMOSPHERE
·
2022
·
IF 8.943
Xiao Wang,Yanshi Zhang,Yue Zhang,Chunhua Xu
Leaching and chemical reduction are two commonly used methods for Cr(VI)-contaminated soil remediation. Leaching focuses more on leaching Cr(VI) out of the soil. Chemical reduction has the disadvantages of poor fluidity of reductant. Combining these two remediation methods, this study investigated the performance of Cr(VI)-contaminated soil when H 2 O and citric acid were used as eluant separately and sulfidated zero-valent iron (SZVI) as reductant. And based on the properties of Cr(VI) chelated with –COOH to form a complex and the characteristics of –OH anchored to FeS x , citric acid modified SZVI (Cit-SZVI) was prepared. The prepared Cit-SZVI was characterized by SEM-EDS, XPS, XRD to study its surface properties. The transformation of Cr species in soil was explored by BCR sequential extraction. The results indicated Cr(VI) removal by SZVI was significantly promoted when citric acid as eluant compared with H 2 O. With SZVI dosage of 2.0 wt%, 23.1 mg/L Cr(VI) was basically removed within 60 min when citric acid as eluant, while only 60% Cr(VI) was removed when H 2 O as eluant even after 3 h. The k obs of Cit-SZVI was 1.4 times that of SZVI when H 2 O as eluant. The characterization of Cit-SZVI showed that more FeS x was formed on the surface of the Cit-SZVI, and more –OH of citric acid was anchored to FeS x , leaving –COOH available to chelate Cr(VI). Compared with H 2 O as eluant and SZVI/Cit-SZVI as reducing agent, the removal effect of Cr(VI) was the best when citric acid as eluant and SZVI as reducing agent. BCR sequential extraction showed that Cr(VI) was effectually fixed, weak acid extractable Cr proportion decreased significantly and residual Cr proportion increased in the treated soil. The combination of leaching and chemical reduction proposed in this study can greatly enhance the Cr(VI) removal effect in soil, which is important for the remediation of Cr(VI)-contaminated soil.
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高影响因子
SCIENCE OF THE TOTAL ENVIRONMENT
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2022
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IF 10.753
Yuxin Liu,Tianye Wang,Ningning Song,Quanying Wang,Yuqing Wu,Ying Zhang,Hongwen Yu
An efficient, simple, and inexpensive N, S-co-doped hydrochar (SNHC) was synthesized from waste straw by a one-pot hydrothermal process without calcination for the removal of Cr(VI). SNHC demonstrated excellent adsorption performance for Cr(VI) and high stability, achieving a high capacity of 171.33 mg/g (293 K, pH 2) and a capacity retention of 82.73 % after five cycles. The adsorption behavior was determined as a multilayer adsorption process based on chemisorption according to the simulation the results of Freundlich adsorption isotherms and pseudo-second-order models. The characterization of SNHC revealed that graphite N and thiophene S formed by the material were the effective active sites, functioning as electron donors to contribute a significant amount of electrons to reduce Cr(VI) to Cr(III). Therefore, next to electrostatic adsorption and complexation, the synergistic reduction of Cr(VI) by graphite N and thiophene S was the main mechanism for Cr(VI) removal. Additionally, density functional theory calculations indicated a low adsorption energy of thiophene S, which increased the attractive interaction between SNHC and Cr(VI) and played the most important role in reducing Cr(VI). The mechanism of the effect of graphite N and thiophene S on Cr(VI) removal not only offered a comprehensive perspective on the role of N, S co-doped mediation in hydrochar but also provided the basic theory for its practical application.
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WATER AIR AND SOIL POLLUTION
·
2023
·Vol. 234
·期 2
·1-16
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IF 2.9
Kang Yongfeng,Yu Yingyuan,Zhang Bingqian,Fu Jianning,Jiang Xixi,Jia Baiyun,Men Xiaoling,Li Li
Metal–organic frameworks (MOFs) are ideal adsorbents for wastewater treatment and excellent antibacterial agents. In this study, Cu-NH 2 -MOF chitosan composite microspheres were prepared by the in situ method, and the synthesized microspheres solved the disadvantages of poor recoverability of powder adsorbent and complex operation process. Cr(VI) was removed by adsorption, and the microspheres had a good bacteriostatic effect. The synthesized MOF chitosan composite microspheres were systematically characterized. The adsorption kinetics, isotherms, and thermodynamic properties were appraised, and influences of adsorption conditions toward Cr(VI) adsorption were studied. The kinetic study demonstrated that the adsorption of Cr(VI) by CS@Cu-MOF-M conformed to the pseudo-second-order model. The adsorption isotherms fit the Sips model, and the maximum adsorption capacity of CS@Cu-MOF-M for Cr(VI) was 159.25 mg/g under optimal conditions. The thermodynamic result showed that the removal of Cr(VI) was a spontaneous endothermic process. The adsorption rate of CS@Cu-MOF-M was still more than 80% of that of the first one after four cycles of regeneration experiments. The antibacterial activity results showed that MOF chitosan composite microspheres had good antibacterial properties with MIC value of 0.2 mg/mL and MBC value of 1 mg/mL. These results demonstrated that the synthesized CS@Cu-MOF-M had a great potential to treat wastewater containing Cr(VI) and bacterial contamination. Graphical Abstract
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Journal of Environmental Chemical Engineering
·
2022
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IF 7.968
Taotao Qiang,Shaoting Wang,Longfang Ren,Xiaodong Gao
ZIF-8 exhibits poor visible light response and rapid electron-hole recombination. To address these problems, we constructed an N-CQD/ZIF-8 framework by in-situ synthesis method, then prepared a novel Z-scheme heterostructure photocatalyst (Cu 2 O/N-CQD/ZIF-8) by reduction precipitation method for the efficient photocatalytic reduction of Cr(Ⅵ). Cu 2 O/N-CQD/ZIF-8 (with a 10% Cu 2 O loading) had a unique heterostructure and exhibited significantly improved performance for Cr(Ⅵ) photoreduction . This photocatalyst successfully reduced 98.99% of the Cr(Ⅵ) in a pH = 3 solution system, which was 6 times higher than that of ZIF-8. Meantime, due to its stable interfacial adhesion, the reduction efficiency of Cr(Ⅵ) by Cu 2 O/N-CQD/ZIF-8 still reached 97.13% after five cycles. Therefore, Cu 2 O/N-CQD/ZIF-8 exhibited superior photocatalytic activity and recyclability compared with unmodified ZIF-8. The charge transfer path of this Z-scheme heterojunction was verified by free radical trapping experiments and X-ray photoelectron spectroscopy. Moreover, a possible charge transfer mechanism was proposed. N-CQD provided a potential driving force for the construction of the internal Z-scheme charge transfer system. Moreover, the synergistic effect between Cu 2 O and ZIF-8 inhibited the rapid recombination of photogenerated electron-hole pairs. This work provides potential insights for the innovative design of high-performance photocatalysts based on metal-organic frameworks for the restoration of Cr(Ⅵ)-containing wastewater.
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MICROPOROUS AND MESOPOROUS MATERIALS
·
2022
·
IF 5.876
Chao Miao,Shumei Chen,Lixing Liang,Kaixuan Shang,Jing Ouyang
In this paper, we used kaolinite tailings as raw materials to design and prepare ZSM-5 zeolite with “flower ball” morphology. Through the functional design of the material, Cr–Ce/ZSM-5 catalysts were prepared for CO 2 -assisted ethane oxidative dehydrogenation reaction (CO 2 -ODH). The folds and grooves on the surface of the “flower ball” ZSM-5 carrier act as a good anchor site for the loading of the active components, thus better anchoring Cr and Ce metal oxides , and leading to a strong interaction between the active component and the carrier. The 5%Cr–10%Ce/ZSM-5 catalyst exhibited the best catalytic performance, the conversion rate of C 2 H 6 and the selectivity of C 2 H 4 can always maintain the initial 64% and 80% within 30 h stability test at 800 °C. The existence of abundant Cr 6+ species in catalyst strengthens the binding ability of the catalyst and active oxygen species and promotes the formation-gasification process of carbon deposits on surface of the catalyst.
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POLYHEDRON
·
2022
·
IF 2.975
Chunqing Wang,Na Xia,Siming Zhu,Lin Chen,Liang Chen,Zhendong Wang
In this study, α- l -rhamnosidase was immobilized on magnetic Fe 3 O 4 /MIL-101 (Cr) nanoparticles using MIL-101(Cr) as precursor by crosslinking method. The crosslinking agent concentration ratio and crosslinking time were EDC/NHS 1:1 and 2 h, respectively. The immobilized materials were characterized by FT-IR, XRD, SEM and VSM. The saturation magnetization of the prepared magnetic nanoparticles was 46.2 emu/g. The optimum pH and temperature of immobilized enzyme were 6 and 60 °C. The application of immobilized enzyme in the preparation of hesperidin dihydrochalcone glucoside (HMGDC) by hydrolysis of hesperidin dihydrochalcone (HSDDC) was studied. The results showed that immobilized enzyme had better temperature resistance, repeatability and stability than free enzyme. The immobilized enzyme activity was 293.55 U/g, and the recovery was 116.03%. After treatment at 60 °C for 4 days, the enzyme activity remained at 24.6%. The conversion rate of HSDDC reached 93.1%.
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SCIENCE OF THE TOTAL ENVIRONMENT
·
2022
·
IF 10.753
Peiling Han,Jiayin Xie,Xueming Qin,Xinru Yang,Yongsheng Zhao
Micron zero valent iron (mZVI) was an underground remediation material, which had great application potential to replace nano zero valent iron (nZVI) from the perspective of economic and health benefits. However, mZVI was highly prone to gravitational settling, which limited its wide application for in situ remediation of contaminated groundwater. This paper was devoted to develop an efficient and economical groundwater remediation material based on mZVI, which should possess excellent stability, reactivity, and transportability. Thereby xanthan gum (XG) stabilized and Na 2 S 2 O 4 sulfidated mZVI (XG-S-mZVI) was synthesized and characterized with SEM, XRD , XPS , and FTIR techniques. In terms of stability, the adsorbed XG and the dispersed XG worked together to resist the sedimentation of S-mZVI. In terms of reactivity, sulfidation enhanced the electron transfer rate and electron selectivity of XG-S-mZVI, thereby improved the reactivity of XG-S-mZVI. The hexavalent chromium (Cr(VI)) removal rate constant by XG-S-mZVI was determined to be 832.4 times than bare mZVI. In terms of transportability, the transportability of XG-S-mZVI was greatly improved (~80 cm in coarse sand and ~50 cm in medium sand). Straining was the main mechanism of XG-S-mZVI retention in porous media . XG-S-mZVI in situ reactive zone (XG-S-mZVI-IRZ) was only suitable to the media with a grain size larger than 0.25 mm. This study could provide theoretical support and guidance for the implementation of IRZ technology based on mZVI.
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高影响因子
JOURNAL OF COLLOID AND INTERFACE SCIENCE
·
2022
·
IF 9.965
Chenrui Liu,He Xiao,Yun Liu,Dejian Li,Hao He,Xiaohan Huang,Wentao Shen,Zhiyan Yan,Zhi Dang,Runliang Zhu
Improving the separation efficiency and transfer ability of photoinduced electrons/holes in pyrite (FeS 2 )-based photocatalytic materials is significant for the photoreduction of hexavalent chromium (Cr(VI)) but still remains a challenge. Herein, a novel homojunction was prepared through in-situ growth of nickel (Ni) doped FeS 2 nanoparticles on FeS 2 nanobelts (denoted as Ni-FeS 2 /FeS 2 ). Systematical characterizations revealed that Ni doped FeS 2 nanoparticles have been successfully in situ grown along the lattice of FeS 2 nanobelts . Photoreduction experiments demonstrated that the Ni-FeS 2 /FeS 2 homojunction with 2 mmol Ni doping contents (denoted as 2Ni-FeS 2 /FeS 2 ) exhibited the optimum Cr(VI) reduction efficiency among the studied catalysts. Density Functional Theory (DFT) calculated results verified that Ni doping could not only be advantageous for the formation of sulfur vacancies but also modify the band gap and band structure of FeS 2 nanoparticles . Moreover, several doping energy levels caused by Ni doping have also appeared near the Fermi level of FeS 2 nanoparticles . The migration paths of electrons and the existence of internal electric field (IEF) in homojunction were further verified by the calculation of work function . To sum up, the doping energy levels and IEF that produced by homojunction played important roles in accelerating the separation efficiency of its photogenerated carriers.
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SEPARATION AND PURIFICATION TECHNOLOGY
·
2022
·
IF 9.136
Lili Zhang,Bihui An,Haojie Chen,Jingjing Chu,Jinxia Ma,Yimin Fan,Zhiguo Wang
Catalytic membrane technology, as a combination of membrane separation and catalysis, is a high-efficiency and feasible route for wastewater remediation. The controllable synthesis of ultrasmall metal nanoparticles on the membrane to maximize the size effect is a challenging task yet. Herein, the filter paper-based botryoidal nanolignin channel stabilized ultrasmall PdNP membrane (Pd@LNP/FP) was prepared by chemical crosslinking of epichlorohydrin (EPI), the nanolignin (LNP) serves as both reducing and capping agent for the in-situ synthesis of ultrasmall PdNP with enhanced active sites. The mean size of PdNP was effectively tuned from 1.76 to 2.09 nm by varying the LNP loading amount of composite membranes. The botryoidal LNP supported on FP also provides the nanoscale channel to keep reactants on active sites of ultrasmall PdNP to improve the catalytic performance of Pd@LNP E /FP. The complete removal of hazardous Cr(VI) required only 2.5 min using Pd@LNP E /FP membrane, the pseudo-first-order rate constant (k) is 1.2725 min −1 , much higher than that of the Pd@LNP p /FP membrane prepared by physical composite (0.2885 min −1 ). Moreover, the rapid filtration-catalysis removal of Cr(VI) can be achieved by twice filtration, demonstrating the high efficiency and feasibility of Pd@LNP E /FP via synergetic filtration enrichment and catalysis reduction.
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COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
·
2022
·
IF 5.518
Jun Liu,Hui Wang,Meng-Jie Chang,Meng Sun,Zhi-Wei He,Cong-Miao Zhang,Wen-Yao Zhu,Jia-Liang Chen,Hui-Ling Du,Long-Gui Peng,Zhen-Min Luo,Li Zhang
Magnetically separatable CoFe 2 O 4 /BiOCl (CFO/BOC) fibers were facilely prepared by solvothermal growth of BiOCl on hollow electrospun CoFe 2 O 4 nanofibers in a weak reduction ethylene glycol (EG) solvent for visible light photocatalytic degradation of various contaminants. Due to the defect level resulted from the oxygen vacancies (OVs), evident visible light response and enhanced charge transfer are achieved both for the solo BiOCl spheres and nanosheets on the CoFe 2 O 4 fibrous support. The optimum CFO/BOC synthesized at 160 °C with a precursor concentration of 50 mM shows outstanding photocatalytic activity to degrade different pollutants of Rhodamine B (RhB, 92.9%), Norfloxacin (NOR, 75.5%), and Cr(VI) (78.0%) within 2 h under visible light. The CoFe 2 O 4 nanofibers are not pivotal for the photocatalytic process, but mainly contribute to the photocatalysis as magnetic support, ensuring the CFO/BOC no aggregation and easy collection under an external magnet. In contrast, the OVs play an important role in the visible light absorption , reactive oxygen species generation and redox process during the photocatalytic process. In detail, both photosensitization of RhB and species of h + and·O 2 - contribute to the degradation of RhB, while NOR decomposition is accomplished by three species (h + ,·O 2 - ,·OH). In addition, electrons are the main reactive species for the photoreduction of Cr(VI). Compared to current reported CoFe 2 O 4 /BiOI photocatalysts , significant advances for the CFO/BOC are obtained not only for the cheap BiOCl with OVs for the photocatalytic application, but also much clearer investigation of more details of CFO/BOC photocatalysts such as light absorption, charge transfer and active species for the degradation of various pollutants.
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JOURNAL OF HAZARDOUS MATERIALS
·
2021
·
IF 10.588
Hao Wang,Shuai Wang,Shixing Wang,Jiali Tang,Yingbi Chen,Libo Zhang
A new zirconium-based adsorption material (UiO-66-AMP) was prepared by modifying UiO-66-NH 2 with 5-adenosine to effectively remove Pb(II) and Cr(VI) from wastewater. The SEM, EDS, XRS and FT-IR characterization confirmed the successful synthesis of UiO-66-AMP. We conducted a sets of experiments to test the adsorption effectiveness of UiO-66-AMP for Pb(II) and Cr(VI). The maximum adsorption capacity of UiO-66-AMP for Cr(VI) (pH=2) and Pb(II) (pH=4) are 196.60 and 189.69 mg/g, respectively. The adsorption process conforms to the pseudo-second-order and Langmuir models, which indicates that the adsorption is a single-layer chemical process. Gibbs free energy ( ∆G) indicates that the adsorption of Pb(II) is an exothermic reaction , while the adsorption of Cr(VI) is an endothermic reaction . At the same time, the adsorbent maintains excellent adsorption capacity at least after 4 cycles. The good adsorption performance of UiO-66-AMP towards the metal ions was attributed to the surface complexation and electrostatic interactions. Therefore, the new adsorbent has obvious application prospect to remove Pb(II) and Cr(VI) from wastewater.
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COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
·
2022
·
IF 5.518
Li Li,Junjie Chen,Guodong Sheng,Yixin Pan,Xiaojie Guo
In this study, a novel nanocomposite (FeS@h-BN) that FeS nanoparticles anchored onto h-BN nanosheets was synthesized for chromium (Cr(VI)) removal in aqueous solutions and characterized by SEM, TEM , XRD , FTIR, Zeta, and XPS . The effect of removal parameters including initial pH, temperature, FeS@h-BN dosage, the initial concentration of Cr(VI) and contact time were investigated. Experiment results revealed that h-BN as a stabilizer for FeS had good stability and effectively reduced FeS agglomeration. The remarkable performance of removing total Cr in aqueous solution was obtained by effectively converting Cr(VI) to Cr(III) on FeS and simultaneously adsorbing Cr(III) on h-BN. The adsorption capacity of FeS@h-BN for Cr(VI) was extremely sensitive to the pH and the optimum adsorption was 399.72 mg/g at pH of 1.0. In addition, the efficiency of removing Cr(VI) by FeS@h-BN increased with the increase of adsorbent dosage and Cr(VI) concentration, and the efficiency reached 100% at an adsorbent dosage of 0.30 g/L. The pseudo-second-order kinetic model can fully explain the experimental rate data. The mechanism of FeS@h-BN to remove Cr(VI) was adsorption and chemical reduction, of which chemical adsorption was the main one. These results revealed that h-BN as a stabilizer can improve the FeS stability and reactivity for the rapid removal of Cr(VI) contamination in water solution.
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