ACS Omega
·
2020
·
IF 2.87
Linlin Du,Peng Gao,Yide Meng,Yuanli Liu,Shangwang Le,Chuanbai Yu
Pyrrole (Py) is easily agglomerated during the polymerization process, affecting its performance. In this paper, polypyrrole/monodispersed latex sphere (PPy/MLS) composites were prepared using in-situ polymerization for the adsorption of hexavalent chromium (Cr(VI)). The specific surface area of PPy/MLS (39.30 m2/g) was increased relative to that of PPy (24.82 m2/g), thus providing more effective adsorption sites. In addition, the adsorption properties of Cr(VI) under different conditions, including Py content, pH of the aqueous solution, and PPy/MLS dosage, were investigated to reveal the adsorption mechanism. The results showed that PPy/MLS possessed high Cr(VI) adsorption capacities when the Py content was 50 wt %. The maximum adsorption capacity was 343.64 mg/g at pH 2.0 and 25 °C. Remarkably, the adsorbents exhibited an excellent removal rate of Cr(VI) after three cycles of adsorption–desorption (over 99%), suggesting that the adsorbents had exceptional recyclability. Furthermore, the adsorption process followed quasi-second-order kinetics and Langmuir isothermal adsorption model. The high adsorption performance, sustainability, and cost-efficiency make this adsorbent a promising candidate for large-scale Cr(VI) contaminant removal.
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WATER AIR AND SOIL POLLUTION
·
2020
·Vol. 231
·期 5
·1-10
·
IF 1.9
Wang Ning,Zhang Feiyan,Mei Qiufeng,Wu Ronglan,Wang Wei
The harm of chromium pollution to the environment has caused a widespread concern; hexavalent chromium is a toxic, cancerogenic, and genetically mutagenic contaminant to the human body; by contrast, trivalent chromium is almost non-toxic to the human body; therefore, it is a feasible method to reduce hexavalent chromium to trivalent chromium. Photocatalysis is a new environmentally friendly and harmless technology, which can transform pollutants into non-toxic or less toxic products. In this study, we synthesized TiO 2 /rGO/CuO ternary nanocomposites to treat hexavalent chromium pollution under visible light. Under optimal conditions, the photoreduction efficiency of 100 ppm hexavalent chromium solution could reach 100% in 80 min. The photoreduction rate of hexavalent chromium is 29.4 times than that of pure TiO 2 . The photocatalytic property of CuO in TG2C8 nanocomposites is attributed to accelerate the separation of electrons and holes and the efficient electron transfer through the rGO framework. We believe that TiO 2 /rGO/CuO composites have great potential in wastewater treatment.
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Journal of Environmental Chemical Engineering
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2021
·
IF 5.909
Xian Zeng,Yuchen Wang,Xinyi He,Caocong Liu,Xi Wang,Xinpeng Wang
Being one of the most toxic pollutants commonly present in wastewater as soluble hexavalent chromium (Cr(VI)) specie, its concomitant adsorption and chemical reduction to relatively insoluble and less poisonous Cr(III) would be an effective strategy for remediation of Cr-polluted water. As such, a novel MXene-polyelectrolyte nanocomposite was typically synthesized for enhanced Cr(VI) removal. In detail, we applied polyethylenimine (PEI) to modify the Ti 3 C 2 T x surfaces and synthesized Ti 3 C 2 T x /PEI nanocomposites. The as-prepared composites were characterized by various methods such as SEM-EDX, N 2 sorption-desorption isotherm, XRD, FTIR, and XPS. Further, the Ti 3 C 2 T x /PEI was used to adsorb Cr(VI) for clarifying the kinetics, isotherms, and the effects of solution pH and coexisting ions on Cr(VI) removal by batch experiments. Our results show that coating of Ti 3 C 2 T x nanosheets with PEI regulates surface charge of the as-synthesized adsorbent and creates it with a three-dimensional network, allowing the fast electrostatic adsorption of Cr(VI) anions to positively charged surface over wide pH range of 1–10 and promoting to achieve improved removal capacity maximum up to 186.5 mg/g. The Cr(VI) adsorption data were well fitted by the pseudo-second-order kinetic and Langmuir isotherm models. In addition, Ti 3 C 2 T x /PEI also exhibits excellent selectivity for Cr(VI) anions over competing ones such as NO 3 − , Cl − , ClO 4 − , and SO 4 2− . Time-dependent reaction routes of Ti 3 C 2 T x /PEI nanocomposite toward Cr(VI) was studied by XPS, which confirmed the slow reduction of all sorbed Cr(VI) to Cr(III) in the dozens of hours and final in-situ Cr(III) immobilization, clarifying the sorption-reduction mechanism for Cr(VI) elimination. All these results suggest that Ti 3 C 2 T x /PEI nanocomposite prepared by reported surface-modification approach available for developing other functionalized adsorbents, may be a potential candidate for decontamination of Cr(VI)-polluted wastewater.
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TALANTA
·
2021
·
IF 6.057
Hui-Min Zhai,Bin Ji,Shan-Shan Tian,Fang Fang,Shuang Zhao,Zhi-Yong Wu
This work presents a new method of Cr speciation analysis based on micro sample pretreatment with a paper-based analytical device (PAD). By using electrokinetic separation and stacking on the PAD, Cr (VI) and Cr (III) can be separated and the recovered to achieve speciation analysis without have to be subjected to subtraction treatment. The separation and recovery properties of Cr (VI) and Cr (III) were characterized and optimized by UV–Vis spectrophotometry , with which the LOQ of 19.0 μg L −1 and 28.7 μg L −1 , and the recoveries of 88–108% and 90–110%, were obtained for Cr (VI) and Cr (III), respectively. In addition, direct analysis of Cr (VI)/Cr (III) from an electroplating wastewater sample was also demonstrated with this method combined with atomic spectroscopy (GF-AAS and ICP-OES). This sample pretreatment method is fast, cheap and easy to be used. Combined with the high sensitivity and elemental selectivity of atomic spectroscopy and mass spectrometry, this PAD sample pretreatment method could be a compensation to their lack in speciation discrimination, and may play an important role in the speciation analysis of Cr.
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Water Science and Engineering
·
2021
·
IF 0
Li Yin,Na Mi,You-ru Yao,Jing Li,Yong Zhang,Shao-gui Yang,Huan He,Xin Hu,Shi-yin Li,Li-xiao Ni
Ferrous sulfide (FeS) nanoparticles constitute an effective hexavalent chromium (Cr(VI)) treatment reagent. However, FeS nanoparticles aggregate easily, significantly limiting their engineering applicability. To overcome this shortcoming and further improve Cr(VI) removal efficiency, this study used tannic acid (TA) to modify FeS nanoparticles. The results demonstrated that TA-modified FeS nanoparticles, TA-nano-FeS, had a significantly reduced tendency to agglomerate, and maintained particle diameters of 10–100 nm, which were much shorter than diameters of FeS nanoparticles. In addition, TA-nano-FeS could combine the surface-active functional groups of TA. The maximum removal capacity of TA-nano-FeS was 381.04 mg/g, which was 2.92 and 1.83 times higher than those of TA and nano-FeS, respectively. Furthermore, the acidic condition was more beneficial for Cr(VI) removal, and the coexisting cations (Ca 2+ and Mg 2+ ) slightly decreased the removal efficiency of Cr(VI). Adsorption, reduction, and co-precipitation were the removal mechanisms, and the reaction products included FeCr 2 O 4 , Cr 2 O 3 , Fe 2 O 3 , Cr(OH) 3 , and S 8 . The results provided valuable information for the practical application of TA-nano-FeS in Cr(VI) removal.
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JOURNAL OF HAZARDOUS MATERIALS
·
2021
·
IF 10.588
Renji Zheng,Jing Li,Runliang Zhu,Ranhao Wang,Xuezhen Feng,Zhijie Chen,Wenfei Wei,Dazhong Yang,Hong Chen
Wastewater with complex compositions of both heavy metals and organic pollutants is of critical environmental and socioeconomic threat worldwide, which urgently requires feasible remediation technologies to target this challenge. In this study, natural chalcopyrite (CuFeS 2 , NCP), the most abundant copper-based mineral in the Earth's crust , has been discovered to be a heterogeneous catalyst that can activate peroxydisulfate (PDS) for the simultaneous degradation of organic pollutant Rhodamine B (RhB) and reduction of hexavalent chromium (Cr(VI)). Batch experimental results indicate that both RhB and Cr(VI) could be simultaneously removed under a near-neutral condition in NCP/PDS combined system. The radicals SO 4 •− and • OH generated from PDS activation are the main oxidative species detected by electron paramagnetic resonance (EPR) spectroscopy. SO 4 •− acted as a predominant role in RhB degradation, while Cr(VI) reduction is mainly attributed to the oxidization of S 2− and S 2 2− species on NCP surface, as well as the photoreduction performance of NCP, which could be enhanced by the intermediates generated from RhB degradation. Density functional theory (DFT) calculation results disclose that Fe is the critical catalytic site for PDS activation. This work demonstrates a user-friendly strategy for remediation of complex wastewater containing both heavy metal and organic pollutants by combining photoreduction and advanced oxidation processes (AOPs) with natural minerals. It paves a way for wastewater treatment by utilizing low-cost natural abundant minerals as catalysts.
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SENSORS AND ACTUATORS B-CHEMICAL
·
2021
·
IF 7.46
Cuijuan Wang,Ming Shang,Haiyan Wei,Mengping Zhang,Wei Zou,Xiao Meng,Wenwen Chen,Hua Shao,Yongchao Lai
Hexavalent chromium (Cr(VI)), a highly toxic heavy metal ion , poses a serious threat to human health, and the demand of rapid detection still on-going. Herein, we propose a surface-enhanced Raman spectroscopy (SERS)-based method for rapid and cost-effective quantification of Cr(VI) in aqueous solutions with direct signal of Cr(VI) rather than indirect signals of Raman reporter molecules exploited in previous studies. This method demonstrates high sensitivity (the detection limit of 0.72 ppb), high reproducibility (the batch-to-batch variation was less than 10 %), and excellent selectivity. The results of this proposed method are fairly in good agreement (R 2 = 0.991) with those of the UV colorimetric method promulgated by the United States Environmental Protection Agency (USEPA). We demonstrated the potential of our novel method for practical application in determining Cr(VI) concentrations in drinking and environmental water samples, in which adequate recovery, and high interference resistance were observed. This method has the advantages of being faster and suitable for on-site inspection as no pretreatment process is required and the equipment is portable. The excellent performance promises a great prospective toward a rapid, reliable, and on-site detection for Cr(VI).
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FUEL PROCESSING TECHNOLOGY
·
2021
·
IF 7.033
Yilun Sun,Meng Huang,Jingpeng Li,Zhiyuan Wang,Jianxin Zhou
The coke in the coils has a serious impact on the long-term and stable operation of the ethylene plant . Inhibiting coking of the cracking furnace is an important issue. In this paper, the Cr/CeO 2 coatings were prepared on the surface of 310S stainless steel by high-velocity oxygen-fuel (HVOF) spraying. The anti-coking performances of the bare 310S specimen and the Cr/CeO 2 coatings were tested by using the pyrolysis of naphtha . The results show that the coating with the thickness of 10–15 μm and a very small number of pores was built up by the obviously deformed splats and the coating/substrate interface is jagged bond. The white area on the surface of Cr/CeO 2 coatings mainly includes CeO 2 . However, the gray area is made of Cr or Cr 2 O 3 . Compared with the bare 310S specimen, the coking inhibition rates of coatings are 48.7%, 58.9%, 76.1% and 88.9% when the ratio of Cr and CeO 2 powder is 19:1, 9:1, 4:1 and 3:2, respectively. With increasing the relative ratio of CeO 2 , more white areas without coke are exposed. The CeO 2 surface can not only inhibit catalytic coking, but also promote the reaction of water vapor and coke.
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PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
·
2019
·Vol. 216
·期 22
·1900379
·
IF 1.606
Liang Ma,Xuejuan Shi,Xiaoxiao Zhang,Shunjun Dong,Lili Li
Core–shell-structured cellulose acetate–polycaprolactone/chitosan (CA–PCL/CS) nanofibers with excellent removal performance of hexavalent chromium (Cr(VI)) are developed by coaxial electrospinning. The effect of core-to-shell ratio on adsorption capability is studied. The results show that all core–shell-structured fibers possess higher adsorption capability and good durability in acidic environment compared with the CS powder adsorbent. CA–PCL/CS fibers with core-to-shell ratio of 0.442 have a maximum adsorption capability of 126 mg g −1 at room temperature. The adsorption kinetics reveals that chemisorption serves as the rate-determining step by notable electron transfer, share, or exchange between adsorbents and adsorbates. The adsorption equilibrium data of the core–shell-structured CA–PCL/CS fiber adsorbents are all well described by the Freundlich isotherm model, indicating the multilayer adsorption process. Herein, it is highlighted that the core–shell-structured CA–PCL/CS nanofibers have a promising prospect in removing Cr(VI) ions from waste water.
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TALANTA
·
2019
·
IF 4.916
Hui-Min Zhai,Ting Zhou,Fang Fang,Zhi-Yong Wu
In this work, a paper-based analytical device (PAD) for sensitive speciation detection of chromium (Cr) by smartphone camera was introduced. In anion electrokinetic stacking mode, Cr (VI) in the form of CrO4 2− was firstly enriched into a narrow band on a paper fluidic channel, and then the band was visualized by 1,5-diphenylcarbazide (DPC). Colorimetric detection of Cr (VI) was based on the gray intensity of stacking bands. Detection of Cr (III) was achieved by subtraction of the detection results of Cr (VI) before and after the sample was oxidized. Under optimized conditions, the detection limit of Cr (VI) and Cr (III) of 0.20 μM (~10.4 μg L −1 ) and 0.30 μM (~14.6 μg L −1 ) were achieved with a linear response in the range of 0.67–5.00 μM and 0.93–6.00 μM, respectively. The detection performance of PAD is close to that obtained by desktop spectrophotometry , thanks to the online stacking effect. Meanwhile, this PAD also exhibited a good selectivity over coexisting cations and anions, thanks to the charge selectivity of the stacking mode and the selective visualization reaction of DPC. Speciation detection of Cr from tap water, river water, surface water, and electroplating wastewater was demonstrated. This work shows the potential of PADs for on-site detection of Cr (VI) in environmental water samples.
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ENVIRONMENTAL SCIENCE & TECHNOLOGY
·
2019
·
IF 7.149
Yue Hu,Xing Peng,Zhihui Ai,Falong Jia,Lizhi Zhang
In this study, we report that liquid nitrogen treatment is a promising zero-valent iron activation method that does not remove the iron oxide shell; this can improve the apparent Cr(VI) removal rate constant of zero-valent iron by about 4–120 times, depending on the particle sizes and the suppliers of zero-valent iron. It was found that liquid nitrogen, with its low temperature of 77 K, could crack the iron oxide shell of zero-valent iron to produce abundant fractures because of the different thermal expansion coefficients of iron oxide and iron. These fractures provided suitable mass transfer channels for the inward transfer of water/oxygen molecules to the iron core and the subsequent in situ generation of Fe(II) for the reduction of Cr(VI) to Cr(III). More importantly, systematic characterizations confirmed the generation of an Fe(III)/Cr(III)/Cr(VI) composite on the surface of zero-valent iron during the removal, suggesting its environmental benignancy. This study provides a novel physical zero-valent iron activation method, sheds light on the importance of the iron oxide shell of zero-valent iron on Cr(VI) removal, and clarifies the intrinsic Cr(VI) removal mechanism of zero-valent iron.
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BIORESOURCE TECHNOLOGY
·
2018
·
IF 5.807
Chaofan Zheng,Huaili Zheng,Yongjuan Wang,Yili Wang,Wenqi Qu,Qiang An,Yongzhi Liu
Novel adsorbents, poly([2-(methacryloxy)ethyl]trimethylammonium chloride) modified magnetic chitosan particles (DMCPs), were synthesized via free radical polymerization and applied to adsorb Cr(VI) from aqueous solution. The effects of pH (2–11), Cr(VI) concentration (10–200 mg/L) and contact time (0–420 min) on the adsorption performance were evaluated. The results showed that the adsorption capacity of DMCPs was much larger than that of magnetic chitosan particles (MCPs) in the examined pH range and decreased with Cl − concentration increasing, indicating that electrostatic interaction and ion exchange are the governing mechanisms of Cr(VI) adsorption by DMCPs. The Langmuir isotherm model and pseudo-second-order kinetic model fitted the experimental data well. The maximum adsorption capacity of DMCPs is 153.85 mg/g. Besides, Cr(VI)-loaded DMCPs could be easily separated and efficiently regenerated. Therefore, DMCPs are promising candidates for Cr(VI) adsorption owing to their excellent performance in a wide pH range, easy separation and good reusability.
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