SEPARATION AND PURIFICATION TECHNOLOGY
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2022
·
IF 9.136
Wenbin Gao,Yan Tan,Binhai Wu,Yuzhen Chen,Zhan Hu,Yifan Wang,Yujiao Wen,Zhi Zhou,Nan Zhou
Quinclorac (QNC) and Cr(VI), are common contaminants in surface waters, posing serious hazard to human and ecological health. Nano FeS, an effective catalyst that has excellent redox properties, is susceptible to over-oxidation and agglomeration problems, which impede its practical application. Herein, nano-Fe 1−x S was modified by stable iron oxide (Fe 3 O 4 ) and biochar (BC AA /Fe 1−x S/Fe 3 O 4 ), which presented the core (Fe 1−x S) shell (Fe 3 O 4 )-like structure uniformly dispersed on BC AA surface. The composite overcame the disadvantages of nano-Fe 1−x S and achieved high removal efficiency of 100% and 99.98% for QNC and Cr(VI), respectively. Based on XPS analysis, Fe(II) content was reduced from 53.3% to 34.2% and S(II) content from 13.0% to 6.5%. Fe(II) species in the composite were the main active substance for QNC degradation and Cr(VI) reduction, and S(II) species also indirectly provided electrons to promote Fe 2+ /Fe 3+ cycling. Then, we identified the intermediates of QNC and active radicals • OH or SO 4 •− in the system to suggest possible degradation pathways. We further discovered no mutual interference between QNC and Cr(VI) and proposed the possible mechanism for simultaneous removal that QNC degradation by radical attack and Cr(VI) reduction by electrons.
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SEPARATION AND PURIFICATION TECHNOLOGY
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2022
·
IF 9.136
Shengli Zhang,Wei Li,Menglin Li,Tong Lin,Kai Su,Hongwei Yang,Junmin Chen
In the present study, a novel PEI-modified Juncus effuses (PEI-JE) adsorbent was prepared based on the natural 3D network structure of JE via a simple and environmental-friendly method with the help of the ethanol/aqueous solution. SEM, EDS, ATR-FTIR and XPS were performed to reveal the physical and chemical structure of the PEI-JE. The Cr(VI) removal by the PEI-JE was investigated by bath adsorption experiments. Results showed that the developed PEI-JE exhibited the same 3D network structure as the JE, which not only was easy to separate from aqueous solution but also can expose more active sites and facilitate mass transfer. The optimal pH for Cr(VI) adsorption on the PEI-JE was 3, and adsorption equilibrium time was related to initial Cr(VI) concentrations. The adsorption kinetic obeyed pseudo-second-order kinetic model, and the adsorption isotherm showed the best fit with Freundlich model. The calculated maximum adsorption capacity was 268.93 mg/g at 25℃. Coexisting ions including Na + , K + , Al 3+ , H 2 PO 4 − , Cl − , NO 3 – had no remarkable effect on Cr(VI) adsorption, but the presence of SO 4 2− , HCO 3 – and CO 3 2– caused the efficiency losses of 10.9%, 41% and 66%, respectively. After 10 cycles of adsorption/desorption, Cr(VI) removal rate on the PEI-JE almost kept unchanged, demonstrating that the PEI-JE possessed good reusability. Mechanism study suggested that Cr(VI) removal was involved in a three-step reaction, namely electrostatic adsorption, redox and complexation. Film diffusion was the rate-limiting step and chemical adsorption was the main mechanism. The Cr(VI) adsorbed on the PEI-JE surface was completely reduced to Cr(III), demonstrating that PEI-JE is useful for Cr (VI) removal and detoxification.
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CHEMOSPHERE
·
2022
·
IF 8.943
Wenxian Chen,Xiangwei Xu,Jinping Cui,Zhenyang Zhou,Yuyuan Yao
Developing novel bifunctional materials to high efficiently degrade organic pollutants and eliminate hexavalent chromium (Cr (VI)) is significantly desired in the wastewater treatment field. The porous boron nitride (p-BN) was fabricated by a two-stage calcination strategy and was innovatively employed to support zero-valent iron (ZVI), achieving the bifunctional material (p-BN@ZVI) to degrade carbamazepine (CBZ) and eliminate Cr (VI). p-BN@ZVI could degrade more than 98% CBZ in 6 min with the high apparent first-order constant (k obs ) of 0.536 min −1 , almost 5 times higher than that of the ZVI/PMS system and outperformed most previous reported ZVI supported catalysts, which was mainly ascribed to the fact that the introduction of p-BN with high surface area (793.97 m 2 /g) improved the dispersion of ZVI and exposed more active sites. Quenching tests coupled with electron paramagnetic resonance (EPR) suggested that •OH was the major reactive oxygen species with a contribution of 71.6%. Notably, the p-BN@ZVI/PMS system expressed low activation energy of 8.23 kJ/mol and reached a 65.69% TOC degradation in 20 min even at 0 °C. p-BN@ZVI possessed remarkable storage stability and could still degrade 92.3% CBZ despite three-month storage. More interestingly, p-BN@ZVI was capable to eliminate 98.1% of 50 mg/L Cr (VI) within 5 min through adsorption and reduction, where nearly 80% Cr (VI) was transformed to Cr (III), and exhibited the maximum Cr (VI) elimination capacity of 349 mg/g. This study provides new insights into the efficient organic contaminants degradation and Cr (VI) elimination in the treatment of wastewater.
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JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
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2022
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IF 6.76
Hongyu Zhang,Ling Chen,Baogang Xu,Ping Yang
The strong band-to-band visible light absorption obtained by changing the bandgap of photocatalysts is desirable but challenging for TiO 2 . In this paper, a mechanochemical pre-reaction and subsequent heat-treatment process were used to create TiO 2 /g-C 3 N 4 heterojunctions. Acid-treated H 2 Ti 3 O 7 nanobelts and superior thin g-C 3 N 4 nanosheets (CN) were ground evenly and further heat-treated to grow rhombic TiO 2 in situ on the nanosheets. The heterojunctions exhibited a band gap with the absorption in visible light region. Heterojunction formation effective tunes the surface and electronic structures of the composite, resulting in significant decrease of bandgap. g-C 3 N 4 -based heterojunctions (5TCN) exhibited excellent H 2 generation (4991 μmol/g/h) and NO removal. In contrast, a TiO 2 -based composite (95TCN) revealed efficient photo reduction of Cr(Ⅵ) which was 2 times of that of TiO 2 sample and 22 times of that of CN. The photochemical reaction mechanism of TiO 2 and g-C 3 N 4 -based composites was discussed with the ratio of TiO 2 and g-C 3 N 4 . The excellent performance is ascribed to single crystal rhombic TiO 2 nanoparticles grown in situ on g-C 3 N 4 to form well-developed heterojunctions which accelerate the carrier transfer. These results inspire the electronic structure engineering of photocatalysts to improve visible light absorption and provide a magic strategy for excellent photochemical activities.
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Biomass Conversion and Biorefinery
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2022
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IF 4.05
Chen Dong,Chen Shanshuai,He Liang,Guan Qingqing,Miao Rongrong
Porous biochar was prepared from agricultural and forestry wastes to remove Cr(VI) in sewage, which solved the problem of water pollution and realized the reuse of wastes. Herein, in this work, the bagasse pith residues after alkali pre-extraction have been used as the raw material for preparing porous biochars ( BPR -BC), which could be further used for efficiently purifying the simulated Cr(VI) wastewater. The results showed that the as-prepared biochars had an ultra-high specific surface area of 2745.7 m 3 /g and Cr(VI) removal capacity of 185.07 mg/g. The kinetic and isotherms studies were best described by pseudo-second-order model and Langmuir adsorption isotherm model, respectively. The thermodynamic studies showed that the adsorption process was endothermic and spontaneous. Furthermore, based on the concept of “waste to waste,” the Cr-contained waste adsorbent by doping Cu has been converted into a bagasse pith residues biochar supported Copper-Chromium catalyst (Cu-CrOx/ BPR -BC) for further hydrogenation of furfural. The catalytic experimental result showed that the furfural 1 can be selectively converted into furfuryl alcohol (FOL) and difurfuryl ether (DEF) catalyzed by the prepared Cu-CrOx/ BPR -BC catalyst, provided a new idea for the further utilization of Cr(VI) containing adsorbents.
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ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
·
2022
·Vol. 29
·期 26
·40041-40052
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IF 5.19
Luo Qin,Huang Xiaofeng,Deng Qiulin,Zhao Xueyuan,Liao Huiwei,Deng Hongquan,Dong Faqin,Zhang Tao,Shi Lianjun,Jiang Jinlong
The photocatalytic properties of Zn/Co zeolite imidazolate frameworks (ZIF-ZnCo) prepared by various Zn/Co ratio are of significantly diversity due to the morphology structure of the ZIF-ZnCo. Thereinto, the prepared ZIF-ZnCO-8:1 is excellent capability by virtue of its 3D cross-shaped structure. Spectral test results show that as-prepared novel 3D cross-shaped ZIF-ZnCo has a lower recombination rate of electron and hole pairs than the lamellar and dodecahedral, thus improving the photocatalytic ability. The photocatalytic ability of 3D cross-shaped ZIF-ZnCo was carefully investigated for removing mixed solution of Congo Red (CR) and Cr(VI). The photocatalytic reduction ability of 3D cross-shaped ZIF-ZnCo was 22% higher than ZIF-8 for Cr(VI). Meanwhile, CR was altogether removed at dark processing and Cr(VI) was removed 70% after dark processing 120 min and photocatalytic 240 min. Therefore, the high adsorption and photocatalytic capacity denote the potential application of 3D cross-shaped ZIF-ZnCo. Graphical abstract
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CHEMICAL ENGINEERING JOURNAL
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2022
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IF 16.744
Chen Wang,Mingjie Huang,Wei Lou,Wei Xiang,Tao Zhou,Juan Mao,Feixiang Zan,Xiaohui Wu
In-situ removal of Cr(VI) by metallic (oxides) materials is generally limited by rapid loss of surface active sites, especially in neutral water/wastewater circumstances co-existing organic ligands impurity. This study has firstly demonstrated that synthesized magnetic electron-rich copper-iron oxides composites (Cu 2 O-Fe 3 O 4 ) could successfully achieve amazingly efficient reductive immobilization of Cr(VI) induced by common citric ligand (Cit). As Cr(VI) reduced heterogeneously on the composites, immobilization of the generated Cr(III) was almost synchronous via a “spatially-separated” way and correlated linearly with simultaneous dissolved Cu. DFT calculations indicated more appropriate adsorption energy of Cit in realizing its preferential coordination on Fe 3 O 4component surface and Cr(VI) adsorption on Cu 2 O component , as compared to oxalic, tartaric and EDTA ligands. The complexed Cit (Cit≡Fe 3 O 4component ) would promote internal electron transfer from Fe 3 O 4component to Cu 2 O component then adsorbed Cr(VI), causing a highly improved electron efficiency of 72.25%. Most importantly, acting as a regulator of the continuously synchronous reduction and immobilization, Cit≡Fe 3 O 4component would tendentiously chelate newborn Cu(II) at Cu 2 O component surface to release bulk Cu 2+ -Cit complexes, refreshing the reduction sites as well as favoring the Cr(III) immobilization of great stability at the exposed sites of Fe 3 O 4component . This study has revealed that specific impurity ligands can stimulate and tune effective reductive immobilization of heavy metal oxyanions by electron-rich materials under near-neutral conditions, providing a new method towards the efficient treatment of Cr(VI) contaminated wastewaters.
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JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
·
2023
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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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SEPARATION AND PURIFICATION TECHNOLOGY
·
2023
·
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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Polymers
·
2021
·Vol. 13
·期 21
·3788
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IF 4.329
Hua Zeng,Zhiyuan Hu,Chang Peng,Lei Deng,Suchun Liu
Due to its lethal effect on the human body and other creatures, Cr(VI) ions have attained widespread public attention, and an effective adsorbent for removing Cr(VI) ions is vital. Chitosan (CS)/cellulose nanocrystals grafted with carbon dots (CNCD) composite hydrogel with strong sorption ability and sensitive detection ability for Cr(VI) was formed. The cellulose nanocrystals (CN) offered a natural skeleton for assembling 3D porous structures, and then improved the sorption ability for Cr(VI); moreover, carbon dots (CD) acted as a fluorescent probe for Cr(VI) and provided Cr(VI) adsorption sites. With a maximum adsorption capacity of 217.8 mg/g, the CS/CNCD composite hydrogel exhibited efficient adsorption properties. Meanwhile, with a detection limit of 0.04 μg/L, this hydrogel was used for selective and quantitative detection of Cr(VI). The determination of Cr(VI) was based on the inner filter effect (IFE) and static quenching. This hydrogel retained its effective adsorption ability even after four repeated regenerations. Furthermore, the economic feasibility of the CS/CNCD composite hydrogel over activated carbon was confirmed using cost analysis. This study provided one new method for producing low-cost adsorbents with effective sorption and sensitive detection for Cr(VI).Keywords:chitosan;cellulose nanocrystals;carbon dots;adsorption;hexavalent chromium
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Catalysis Science & Technology
·
2021
·Vol. 11
·期 24
·7963-7972
·
IF 6.119
Anyu Liu,Jianqiang Hu,Jiale He,Xinyue Huang,Na Hu,Yuqin Li,Qingling Huang,Shien Guo,Xin Liu,Zhen Yang,Yong Zhou,Zhigang Zou
O-doped g-C3N4/In2S3 hierarchical heterostructures with a direct Z-scheme mechanism were devised and constructed simply via loading In2S3 nanoflakes on the surface of O-doped g-C3N4 (OCN) hierarchical structures, in situ, employing pre-obtained OCN (prepared by condensation of oxalic acid and urea) and indium(III) dimethyldithiocarbamate (In(dedc)3) as precursors. Analyses of the energy band structure, density functional theory (DFT) computations and DMPO-ESR spin-trapping experiments demonstrate that the formation of a perfect heterointerface with a staggered alignment of band edges between OCN and In2S3 (IS), owing to their close contact, enables photoexcited carriers to migrate via a Z-scheme route, which can maintain the higher reduction and oxidation capability of electrons and holes, respectively. Furthermore, the Z-scheme OCN/IS heterostructures efficaciously facilitate the separation of photogenerated electrons and holes, as demonstrated using PL spectra, transient photocurrent densities and electrochemical impedance spectra (EIS). These lead to the enhanced photocatalytic activity towards reducing Cr(VI) into Cr(III). Besides, the integration of OCN with IS can enhance the responsiveness to visible light based on the results of UV-vis DRS, thereby inducing the formation of more electrons and holes,and also contributing to the improvement of the photocatalytic activity for Cr(VI) reduction. In consequence, all the pre-prepared OCN/IS hybrids possess markedly improved photocatalytic activities for Cr(VI) reduction, relative to pure OCN and pristine IS under visible light (λ > 420 nm) illumination. With the increase in the In(dedc)3 to OCN mass ratio (R), the photocatalytic activities of these OCN/IS hybrids increase first and then decrease. The sample with an optimum R of 0.9 (OCN/IS-0.9) can remove nearly 100% of Cr(VI) after 40 min of illumination, being superior to most of g-C3N4-based and IS-based photocatalysts. Its reaction rate constant for Cr(VI) photoreduction (0.08947 min−1) is 56.7 fold and 8.8 fold higher than that of pure OCN (0.00155 min−1) and pristine IS (0.00913 min−1), respectively. This work affords a deep understanding on designing preeminent Z-scheme photocatalysts towards the degradation of Cr(VI) under visible-light irradiation.
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CERAMICS INTERNATIONAL
·
2023
·
IF 5.2
Kai Xuan,Taiguang Li,Yongmei Hao
Adequate separation of photogenerated carriers plays an important role in the photocatalytic degradation of pollutants. Here, a noble-free spatially separated photocatalyst rGO-CdS-MnO x (GCM) has been designed for removing environmental pollutants efficiently. rGO and MnO x are employed as the collectors of photoinduced electrons and holes, respectively. Under light irradiation, the electrons and holes motivated by CdS can directionally transfer to the rGO and MnO x , leading to the exposure of both reduction and oxidation surfaces, thereby enhancing the photocatalytic activity. Our results demonstrated that GCM-30 can remove 86.56 % of carbamazepine and 95.83 % of tetracycline hydrochloride within 30 min and 15 min, respectively, and 95.49 % of Cr (VI) within 21 min. Our work demonstrates that this dual functional photocatalyst may provide new strategies for the spatially separated photocatalysts for removing environmental pollutants.
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