CHEMICAL ENGINEERING JOURNAL
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2019
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IF 8.355
Zhi-Hui Huang,Zhi-Yong Ji,Ying-Ying Zhao,Jie Liu,Fei Li,Jun-Sheng Yuan
Both thermal and alkali are effective means of persulfate (PS) activation, and the synergistic effect of them should achieve a great degradation result. It is evaluated for treating coal chemistry industry wastewater because the by-product produced in the process is sulfate, which is pre-existing in the wastewater. With thermal and alkali synergistic activation, the application of the response surface method revealed the effects of temperature, pH and concentration of persulfate on the degradation ratio of 2-methoxyphenol (MOP, a typical contaminant in coal chemical industry wastewater) and their interactions. The results showed that the degradation rate of the contaminant was temperature and pH dependent, while chloride (Cl − ) and sulfate (SO 4 2− ) ions had no obvious negative effect. The degradation ratio could be enhanced with higher activation temperature and pH (7–12). The faster degradation could be achieved by thermal-alkali synergistic activation, and the degradation ratio of 88.4% and 93.8% could be achieved at pH = 12 within 10 min and 20 min, respectively. Electron spin resonance (ESR) spectra and free radical scavenging experiments indicated that MOP degradation was achieved by the oxidation of both sulfate radical (SO 4 − ) and hydroxyl radical ( OH) at pH = 6, and only by OH at pH = 12. In addition, the radical reaction was intense under thermal-alkali synergistic activation of PS, while the quenching reaction was ineffective.
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Journal of the Taiwan Institute of Chemical Engineers
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2019
·
IF 3.834
Pengchao Xie,Yujia Zou,Shan Jiang,Zongping Wang,Jingwen Wang,Li Zhang,Siyang Yue,Xiaonan Feng
Good degradation of β -blocker propranolol (PrP) in the VUV/UV 254 system was achieved in both pure water and realistic water. Both hydroxyl radical (HO • ) and UV 254 photolysis have been evidenced to contribute to PrP degradation in the VUV/UV 254 system. A kinetic model by including both HO • and UV 254 photolysis was successfully applied to predict the observed rate constant ( k obs ) of PrP degradation in the VUV/UV 254 system under different conditions. Elevating initial PrP concentration would reduce the steady-state concentration of HO • , as a result to decreasing the k obs of PrP degradation. While elevating reaction temperature can significantly accelerate PrP degradation. The degradation of PrP in the VUV/UV 254 system was little affected by the variation of reaction pH. HCO 3 − /CO 3 2− , humic acid (HA) and Cl − significantly inhibit PrP degradation in the VUV/UV 254 system. The PrP degradation pathways initiated with hydroxylation and cleavage of side chain were proposed. Although some intermediate products containing higher acute toxicity than PrP were produced in the initial phase of PrP degradation, they could be further oxidized to low toxic products in the system. This study provides that VUV/UV 254 would be a good advanced oxidation process for the treatment of β -blockers in aquatic environment.
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CHEMICAL ENGINEERING JOURNAL
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2019
·
IF 8.355
Qingning Wang,Mingyue Liu,Hongying Zhao,Ying Chen,Fan Xiao,Wenhai Chu,Guohua Zhao
A synergic electrochemical process between cathodic electro-Fenton and anodic oxidation was proposed for efficient degradation of perfluorooctanoic acid (PFOA) in this work. The electron-transfer ability and hydroxyl radicals ( OH) concentration are the key parameters for the PFOA degradation efficiency. Boron-doped diamond (BDD) anode exhibited the highest anodic oxidation ability compared to platinum and carbon stick. The integrated FeMn-doped carbon aerogel was fabricated as cathode for in-situ enhancing the generation of OH. The X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) indicated the main composition of cathode is Fe 0 and MnO. The Fe in the integrated cathode favors the electro-catalytic ability of oxygen reduction reaction (ORR), while MnO enhances the selectivity of 2-electron ORR with H 2 O 2 as main product. The electroformed H 2 O 2 would be onsite catalytic decomposition with Fe II and Mn II as Fenton catalysts for in-situ generating OH radicals. The optimal cathode with Fe/10Mn weight ratio can generate the highest concentration of OH. The catalytic degradation efficiency in this synergic electro-catalysis process with BDD as anode and Fe10MnC as cathode reached nearly 97% PFOA removal and 93% TOC removal after 4 h, suggesting the prominent synergic combination of cathodic electro-Fenton and anodic oxidation. The amount of intermediates C 6 F 13 COO − was decreased while others including C 5 F 11 COO − , C 4 F 9 COO − , C 3 F 7 COO − , C 2 F 5 COO − , CF 3 COO − were increased with increasing electro-catalysis time. The NEXAFS analysis of F in solution and cathode surface further confirmed the continuously synergic electro-catalysis between anodic and cathodic electro-Fenton oxidation.
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CHEMICAL ENGINEERING JOURNAL
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2019
·
IF 8.355
Runren Jiang,Guanghua Lu,Zhenhua Yan,Donghai Wu,Ranran Zhou,Xuhui Bao
The development of a novel Z-scheme system with a high separation efficiency of the charge carriers for remarkably enhanced photocatalytic activity is highly desirable. Herein, a carbon quantum dot-modified SnNb 2 O 6 /BiOCl (CQD-SNO/BOC) Z-scheme system, in which the CQDs acted as a bridge for the charge carriers, was successfully synthesized. As expected, the CQDs acted as a bridge for the charge carriers that could separate and accumulate electrons from SnNb 2 O 6 and holes from BiOCl by promoting the transfer of the photoinduced charge carriers, which enabled the BiOCl holes to maintain their high oxidation capability. Additionally, the CQDs not only endowed the SNO/BOC Z-scheme system with a large specific surface area that provided a greater number of active sites but also noticeably improved its visible light absorption capacity. Therefore, the CQD-SNO/BOC Z-scheme system showed an improved photocatalytic performance for the degradation of benzocaine (BC), which was over 20 times, 10 times and 2 times greater than those of BiOCl, SnNb 2 O 6 and SNO/BOC Z-scheme systems, respectively. In addition, the effects of catalyst concentration, pH value, different anions, and humic acid (HA) concentration on the photodegradation of BC were investigated in depth. Simultaneously, a four-stage pathway for the degradation of BC was proposed based on the degradation products that were identified, and the accuracy of this pathway was further verified based on biotoxicity assessments and toxicity predictions of the products. According to the ESR spectra and active species trapping experiments, a mechanism for the CQD-SNO/BOC Z-scheme system was proposed, in which the CQD bridge accelerated charge transfer. Based on these results, the CQD-modified Z-scheme system could be an efficient and promising photocatalyst for the degradation of PPCPs in water.
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CHEMOSPHERE
·
2019
·
IF 5.108
Xin Liu,Baoling Yuan,Jing Zou,Lingbin Wu,Lin Dai,Hongfang Ma,Kai Li,Jun Ma
The activation of persulfate by Fe(II) coupled with hydroxylamine (the HA/Fe(II)/PS system) was highly effective for the degradation of refractory organic contaminants under acidic pH conditions. However, owing to the precipitation of ferric hydroxide and/or the slow reduction from Fe(III) to Fe(II), the HA/Fe(II)/PS system was invalid under neutral and alkaline pH conditions. In this study, it was observed that the degradation of acid orange 7 (AO7) was strongly enhanced over the wide pH range of 2–9 when trace Cu(II) (0.5–5 μM) was spiked into the HA/Fe(II)/PS system. It was evident that Cu(I) was generated via the reduction of Cu(II) by HA in the bimetallic system at both pH 3 and pH 8, and the steady concentration of Fe(II) in the bimetallic system was much higher than that in the HA/Fe(II)/PS system due to the rapid reaction between Fe(III) and Cu(I). Quenching experiments using tert-butyl alcohol, methanol and sodium bromide as the scavengers and electron spin resonance experiments confirmed that the primary reactive species responsible for AO7 degradation were sulfate radical at both pH 3 and pH 8, rather than hydroxyl radical and Cu(III). Nevertheless, sulfate radical was mainly produced by Fe(II)-activated PS at pH 3, while both Cu(I) and Fe(II) made important contributions to the generation of sulfate radical at pH 8. The bimetallic system was also highly effective in degrading other organic contaminants, such as phenol, diclofenac, reactive red 2 and orange G. This study might provide a promising idea based on Fe(II)-activated PS for degrading organic contaminants over a wide pH range.
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APPLIED CATALYSIS B-ENVIRONMENTAL
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2019
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IF 14.229
Weifang Zhang,Feng Liu,Yonggang Sun,Jing Zhang,Zhengping Hao
Multiple heavy-metal ions (e.g. Cr(VI) and As(III)) normally co-exist in acid wastewater, making the wastewater treatment complicated. Herein, the synergistic redox conversion and removal of Cr(VI)/As(III) were effectively achieved by applying iron(III) cross-linking alginate hydrogel beads (Fe-SA) as photocatalyst under simulated sunlight. Results show that not only 100% of the Cr(VI)/As(III) redox conversion was obtained in 150 min at pH 3.0, but also the removal efficiency of the transformed products (Cr(III) and As(V)) was greatly enhanced to above 80% in a wide pH range of 3–7. The CO 2 − radicals, produced by the ligand to metal charge transfer (LMCT) excitations on Fe-SA, together with the phtocatalysis-generated Fe(II), was responsible for the Cr(VI) reduction. Meanwhile, OH originating from CO 2 − mainly contributed to the As(III) oxidation, as confirmed by electron paramagnetic resonance and the by-product of CO 2 . Moreover, Fe-SA composite presented excellent reusability and performance in treatment of Cr(VI)/As(III) in real waters.
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Catalysis Science & Technology
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2019
·Vol. 9
·期 16
·4365-4373
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IF 5.726
Shiyuan Gao,Haoran Zhou,Yannan Xia,Xiudan Liu,Yuyuan Yao,Wentao Wang,Haixiang Chen
The development of efficient and environment-benign catalytic materials to activate peroxymonosulfate (PMS) for refractory pollutant removal has been considered as an attractive yet challenging topic in the field of wastewater treatment. Herein, carbon fiber-assisted iron carbide (Fe3C@CFs) was innovatively prepared by a hydrothermal and calcination method. Fe3C@CFs could activate PMS and remove the pollutant Acid Red 1 (AR1) up to 97.3%, and even the rate constant was 12.4 times higher than that of Fe3C. The leaching of iron ions was only 0.002 ppm, which was extremely lower than the European standard. Furthermore, Fe3C@CFs still exhibited a favorable catalytic performance after 4 cycles. The catalytic mechanism was investigated by a hybrid method of various radical scavengers combined with electron spin resonance, suggesting that 1O2 served as the main reaction oxidation species rather than ˙OH or SO4˙− during the catalytic process, different from most of the reported radical paths for activating PMS. In addition, Fe3C@CFs possessed wide pH adaptability (3–10) and relatively low activation energy (24.47 kJ mol−1) for AR1 removal. These findings pave a promising avenue to develop highly efficient and eco-friendly catalytic materials for environmental remediation.
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CHEMOSPHERE
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2019
·
IF 5.108
Pengchao Xie,Yujia Zou,Shan Jiang,Jingwen Wang,Li Zhang,Zongping Wang,Siyang Yue,Xiaonan Feng
Degradation of imipramine (IMI) in the VUV system (VUV 185 + UV 254 ) was firstly evaluated in this study. Both HO • oxidation and UV 254 direct photolysis accounted for IMI degradation. The quantum yields of UV 254 direct photolysis of deprotonated and protonated IMI were 1.31 × 10 − 2 and 3.31 × 10 − 3 , respectively, resulting in the higher degradation efficiency of IMI at basic condition. Increasing the initial IMI concentration lowered the degradation efficiency of IMI. While elevating reaction temperature significantly improved IMI degradation efficiency through the promotion of both the quantum yields of HO • and the UV 254 direct photolysis rate. The apparent activation energy was calculated to be about 26.6 kJ mol −1 . Negative-linear relationships between the k obs of IMI degradation and the concentrations of HCO 3 − /CO 3 2− , NOM and Cl − were obtained. The degradation pathways were proposed that cleavage of side chain and hydroxylation of iminodibenzyl and methyl groups were considered as the initial steps for IMI degradation in the VUV system. Although some high toxic intermediate products would be produced, they can be further transformed to other lower toxic products. The good degradation efficiency of IMI under realistic water matrices further suggests that the VUV system would be a good method to degrade IMI in aquatic environment.
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JOURNAL OF HAZARDOUS MATERIALS
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2019
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IF 7.65
Wenlei Qin,Xiangjuan Yuan,Lei Sun,Zhimin Qiang,Dongsheng Xia
The decontamination of prometon (PMT) by ozone/hydroxylamine hydrochloride (O 3 /HAC) was systematically investigated in this study with focus on the degradation mechanism and kinetics. Experimental results revealed that there was an enhancement of PMT degradation efficiency by 42.1% and the pseudo-first-order rate constant by more than 5.7 times in O 3 /HAC process under low HAC dosage (5 mg L −1 ) after 3 min in comparison with O 3 alone. The second-order rate constant of PMT with hydroxyl radical ( • OH) was determined to be (1.84 ± 0.1) × 10 9 M −1 s −1 and 7.80 × 10 9 M −1 s −1 via competition kinetics and • OH steady-state hypothesis, respectively. The PMT removal in O 3 /HAC process was highly pH-dependent and the optimum degradation performance was achieved under pH 5.0. In addition, • OH and singlet oxygen were identified as the primary reactive oxygen radicals in O 3 /HAC process. Meanwhile, eleven transformation products of PMT were identified and possible degradation mechanisms were proposed. Moreover, a kinetic model based on chemical kinetics and steady-state hypothesis was developed and modified to predict the PMT abatement in O 3 /HAC process. The results demonstrated that the O 3 /HAC process provided a promising alternative for refractory organic pollutants decontamination in water treatment.
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CHEMOSPHERE
·
2019
·
IF 5.108
Ruijie Xie,Gaoyuan Liu,Dingping Liu,Shimin Liang,Dongxue Lei,Hanying Dong,Haibao Huang,Dennis Y.C. Leung
The traditional treatment processes for volatile organic compounds (VOCs) removal generally suffered several disadvantages, such as secondary air-pollutants. To overcome these issues, wet scrubber coupled with heterogeneous UV/Fenton was developed for gaseous VOCs (i.e. toluene) removal. ZSM-5 supported iron oxide (Fe/ZSM-5) was prepared as a multifunctional catalyst for activation of H 2 O 2 and enhancement of gas-liquid mass transfer. Toluene was removed efficiently by this coupled process with the removal efficiency of 85% during 120 min. Many intermediates were detected in the solution by GC-MS while no intermediates were observed in the outlet gas, suggesting that wet scrubber coupled with heterogeneous UV/Fenton could significantly reduce secondary air pollutants . The possible mechanism of toluene oxidation was proposed including the physical adsorption by Fe/ZSM-5 and OH oxidation. This study provides an environmentally benign and highly efficient chemical scrubbing process for gaseous VOCs removal.
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JOURNAL OF HAZARDOUS MATERIALS
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2019
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IF 7.65
Mingyu Wei,Xiaowen Shi,Ling Xiao,Haifei Zhang
Polyimide-modified carbon nanotubes (PI/CNTs) were synthesized via a solvent-free thermal method and used as a metal-free catalyst to activate peroxymonosulfate for organic contaminant degradation without light irradiation. The characterization results suggested that PI was loaded onto the surface of CNTs . The catalytic ability of the PI/CNTs was strongly correlated with the content of PI in the catalysts. The PI/CNTs (22% of PI) showed the highest catalytic efficiency for organic pollutant degradation at room temperature. The degradation efficiency of acid orange 7 (AO7) dye was significantly enhanced to 98.9% within 15 min, compared to the efficiency of 2.2% exhibited by pure PI. The radical quenching tests and electron paramagnetic resonance spectrometry proved that singlet oxygen, instead of hydroxyl radicals or sulfate radicals, played a dominant role during the catalytic oxidation of AO7. The influences of operation parameters including temperature and catalyst amount were investigated. The PI/CNTs metal-free catalyst exhibited high catalytic activity under a broad range of pH values. The recycling study of four repeated reactions demonstrated good stability of the PI/CNTs. This work provided a promising metal-free catalyst for degradation of organic pollutants in aqueous solutions, contributing to the development of green materials for sustainable remediation.
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Materials Research Express
·
2019
·Vol. 6
·期 9
·0950c3
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IF 1.449
Qianzhu Mu,Yanfeng Sun,Aiying Guo,Xiazhao Yu,Xiaoyue Xu,Aijun Cai,Xiuping Wang
A series of Fe3O4–TiO2 composites were successfully synthesized using Chlorella pyrenoidosa as a bio-template. C. pyrenoidosa is not only a promising bio-template for obtaining Fe3O4 and TiO2 nanoparticles (NPs) but is also a natural dye sensitizer source that improves the photocatalytic activity of the TiO2 NPs under visible light. The bandgap energy of Fe3O4–TiO2 is narrower than that of TiO2 due to the coupling between the Fe3O4 and TiO2 NPs. The coupling and dye-sensitization lead to the rapid separation and suppressed recombination of electron-hole pairs in Fe3O4–TiO2, which enhances the photocatalytic activity of TiO2 under visible light. The photocatalytic activity of the as-prepared composites was evaluated by degrading a rhodamine B (RhB) aqueous solution under visible-light irradiation. Fe3O4–TiO2 exhibits a high degradation efficiency for RhB, and can be withdrawn from solution easily using an external magnetic field.
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