| Reduction of phoxim pesticide residues from grapes by atmospheric pressure non-thermal air plasma activated water Publication date: 5 September 2019 Source: Journal of Hazardous Materials, Volume 377 Author(s): Yongping Zheng, Songjie Wu, Jie Dang, Shifang Wang, Zhengxin Liu, Jing Fang, Ping Han, Jue Zhang AbstractIn this study, we propose a novel strategy, plasma activated water (PAW) to reduce pesticide residues on agricultural products. To validate its feasibility and effectiveness, we employee high-performance liquid chromatography (HPLC) to detect phoxim on grapes. HPLC results suggest that the reduction of phoxim on grapes achieve 73.60% after treated 10 min by PAW prepared 30 min, and the concentration of phoxim decreased significantly (p < 0.05) with the preparation time of PAW. Furthermore, HPLC-MS analysis shows that the reduction effect of phoxim by PAW is dominated by the degradation of phoxim. Combined with analyzing the physicochemical properties of PAW, one possible degradation pathway is proposed under the present experimental conditions, mediated by reactive oxygen and nitrogen species. The acidic environment (pH < 3) and high oxidation capacity (ORP > 500 mV) are suggested to be a benefit to the reduction of phoxim. Besides, the experimental results regarding color, firmness, sugar, vitamin C, and superoxide dismutase of grapes demonstrate that the PAW treatment will not significantly affect the quality of grapes. In conclusion, phoxim pesticide residues on grapes could be effectively reduced by the PAW strategy and without a significant (p < 0.05) effect on grapes quality. Graphical abstract |
| Thermal and pH dual-responsive cellulose microfilament spheres for dye removal in single and binary systems Publication date: 5 September 2019 Source: Journal of Hazardous Materials, Volume 377 Author(s): Yuan Li, Huining Xiao, Yuanfeng Pan, Min Zhang, Yongcan Jin AbstractCellulose microfilaments/poly(N-Isopropylacrylamide-co-acrylic acid) spheres (MPNAA) were prepared via the in-situ synthesis of semi-interpenetrating networks (semi-IPN). The free radical copolymerization of acrylic acid (AA) (for pH-sensitive chain segments) and N-isopropylacrylamide (NIPAM) (for temperature-sensitive chain segments) was conducted in a microwave-reactor in the presence of porous cellulose/microfilament composite spherical beads pre-prepared. The surface morphology and adsorption properties of the as-prepared spheres were systematically characterized. The adsorption behaviors of resulting MPNAA towards dyes, methylene blue (MB) and methyl violet (MV), were pH sensitive; and the optimal adsorption occurred at pH 9. The dynamic adsorption processes could be well fitted with pseudo-second-order kinetic, Elovich and simplified intraparticle diffusion models. Meanwhile, Langmuir, Temkin, Freundlich, and Dubinin-Raduskevich models were used to fit the adsorption isotherms at 25, 40, and 55 °C, respectively. The results indicated that the adsorption capacities of MPNAA towards MB and MV could reach as high as 497.5 and 840.3 mg g−1, respectively, in single systems; and high adsorption capacity was maintain in binary systems with the favorable adsorption of MV. Overall, the semi-IPN MPNAA spheres are promising as novel pH- and temperature-responsive adsorbents, facilitating the controllable adsorption/desorption processes. Graphical abstract |
| Enhancing the performance of soil microbial fuel cells by using a bentonite-Fe and Fe3O4 modified anode Publication date: 5 September 2019 Source: Journal of Hazardous Materials, Volume 377 Author(s): Bao Yu, Yanhong Li, Liu Feng AbstractTo improve the performance of soil microbial fuel cells (SMFCs), Fe3O4 and bentonite-Fe were selected as anode modifiers, and correspondingly, graphite felt (GF), GF + Fe3O4 (GFF), and GF + bentonite-Fe (GFB) anodes were created and applied to the SMFCs system. The stable voltages of SMFCs were 249 mV for GFF and 324 mV for GFB, thus representing an increase by 8.26% (GFF) and 40.87% (GFB) in comparison with those of GF. Moreover, the maximum power density in the modified treatment increased from 10.6 mW·m−2 to 18.28 mW·m−2 (GFF) and 29.98 mW·m−2 (GFB), and the internal resistance was reduced to 395 Ω for GFF and 219 Ω for GFB. The degradation efficiency clearly improved after being modified, especially by bentonite-Fe, and the removal ratios of the total petroleum hydrocarbon (TPH), anthracene, phenanthrene and pyrene reached 31.42%, 36.62%, 32.48% and 26.24%, respectively, after the SMFCs had run for 45 days. Both modifications contributed to the enrichment of electricigens on the anodes; however, there was minimal difference between them, which resulted in a similar microbial community on the modified anodes. The results demonstrated that Fe3O4 and bentonite-Fe could enhance the potential of SMFCs in soil remediation, and bentonite-Fe outperformed Fe3O4. Graphical abstract |
| Atrazine degradation using Fe3O4-sepiolite catalyzed persulfate: Reactivity, mechanism and stability Publication date: 5 September 2019 Source: Journal of Hazardous Materials, Volume 377 Author(s): Ximeng Xu, Weiming Chen, Shaoyan Zong, Xu Ren, Dan Liu AbstractIn this study, with sepiolite as a support, a novel magnetic Fe3O4-sepiolite composite was fabricated by coprecipitation method. The characterization results reveal that the sepiolite support could anchor Fe3O4 nanoparticles with good dispersion. The composite was used as a catalyst to activate persulfate (PS) for atrazine (ATZ) degradation. 71.6% of ATZ and 20.9% of solution TOC could be removed after 60 min with 92 mmol/L of PS ([ATZ]0= 10 mmol/L). Due to the good adsorption capacity of Fe3O4-sepiolite composite toward ATZ, the degradation was considered to be facilitated by an adsorption process, since the adsorbed ATZ can be more easily transported to the active sites and be degraded in situ. Operation factors, including PS dose and solution pH, were investigated and found to be influential for the ATZ removal. The Fe3O4-sepiolite composite maintained its catalytic activity and structural stability with negligible Fe leaching during the recycling batch experiments. The intermediate products were further identified and the possible transformation pathway was then proposed based on the results. The findings of this research promote the application of Fe3O4-sepiolite composite as efficient and recyclable heterogeneous catalyst for organic degradation, and provide insights into the development of alternative catalysts with good adsorptive properties. |
| Auto-ignition behaviors of nitromethane in diluted oxygen in a rapid compression machine: Critical conditions for ignition, ignition delay times measurements, and kinetic modeling interpretation Publication date: 5 September 2019 Source: Journal of Hazardous Materials, Volume 377 Author(s): Meng Yang, Yingtao Wu, Chenglong Tang, Yang Liu, Zuohua Huang AbstractIn this work, the weakest thermodynamic conditions for the auto-ignition of mixtures containing nitromethane were experimentally determined by using the rapid compression machine facility. Results show there is a narrow weak ignition region between ignition and non-ignition. The weak ignition region would disappear with the increase of the EOC (end of compression) pressure and nitromethane concentration. In addition, the ignition delay times for successful auto-ignition for different nitromethane concentrations and equivalence ratio mixtures were measured and compared. Results show that the dependence of nitromethane ignition on the equivalence ratio is weak. Subsequently, the measured ignition delay time data were employed to validate several kinetic models in literature and our previous model shows better agreement with experimental results, as well as other available literature data. Sensitivity analysis for the model reveals the importance of unimolecular decomposition and H-abstraction reactions for the ignition delay times in the temperature range studied herein. Finally, critical conditions for nitromethane ignition under extended conditions that are beyond the ability of the experimental facility were predicted. |
| Transient–state operation of an anoxic biotrickling filter for H2S removal Publication date: 5 September 2019 Source: Journal of Hazardous Materials, Volume 377 Author(s): Ramita Khanongnuch, Francesco Di Capua, Aino-Maija Lakaniemi, Eldon R. Rene, Piet N.L. Lens AbstractThe application of an anoxic biotrickling filter (BTF) for H2S removal from contaminated gas streams is a promising technology for simultaneous H2S and NO3− removal. Three transient–state conditions, i.e. different liquid flow rates, wet–dry bed operations and H2S shock loads, were applied to a laboratory–scale anoxic BTF. In addition, bioaugmentation of the BTF with a H2S removing–strain, Paracoccus MAL 1HM19, to enhance the biomass stability was investigated. Liquid flow rates (120, 60 and 30 L d−1) affected the pH and NO3− removal efficiency (RE) in the liquid phase. Wet–dry bed operations at 2–2 h and 24–24 h reduced the H2S elimination capacity (EC) by 60–80%, while the operations at 1–1 h and 12–12 h had a lower effect on the BTF performance. When the BTF was subjected to H2S shock loads by instantly increasing the gas flow rate (from 60 to 200 L h−1) and H2S inlet concentration (from 112 (± 15) to 947 (± 151) ppmv), the BTF still showed a good H2S RE (>93%, EC of 37.8 g S m–3 h–1). Bioaugmentation with Paracoccus MAL 1HM19 enhanced the oxidation of the accumulated S0 to sulfate in the anoxic BTF. |
| Surface treatment by the Fe(III)/sulfite system for flotation separation of hazardous chlorinated plastics from the mixed waste plastics Publication date: 5 September 2019 Source: Journal of Hazardous Materials, Volume 377 Author(s): Maozhi Luo, Hui Wang, Yingshuang Zhang, Yiwei Zhong, Kangyu Wang AbstractA novel advanced oxidation process by a combination of Fe(III) and sulfite for surface treatment of waste plastic mixtures is proposed. The Fe(III)/sulfite system has been found to enhance hydrophilicity of the mixed waste plastics, including acrylonitrile butadiene styrene (ABS), polystyrene (PS) and polycarbonate (PC), while it has little effect on hazardous polyvinyl chloride (PVC), thus promoting separation of PVC from the mixed waste plastics by flotation. Radical scavenging experiments indicate that sulfate radicals are the main reactive species. Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) results imply the formation of C Graphical abstract |
| Plasma-enhanced steam reforming of different model tar compounds over Ni-based fusion catalysts Publication date: 5 September 2019 Source: Journal of Hazardous Materials, Volume 377 Author(s): Lina Liu, Yawen Liu, Jianwei Song, Shakeel Ahmad, Jie Liang, Yifei Sun AbstractTar formation during biomass gasification is undesirable due to the decreased energy efficiency and increased costs for maintaining downstream equipment. The hybrid non-thermal plasma-catalysis method is considered to be a promising alternative, since it overcomes the disadvantages arising from both catalyst deactivation during catalytic reforming and the formation of undesirable liquid by-products in plasma reforming. SiO2- and ZSM-5-supported Ni-based catalysts with different Ni loadings (0.5, 1, 3, and 5 wt%) were prepared by thermal fusion and applied to the steam reforming of toluene. Different characterizations of fresh and spent catalysts including XRD, H2-TPR, N2 adsorption-desorption, SEM, TEM, XPS and TGA were conducted to show the properties of catalysts. The results indicated that Ni/ZSM-5 exhibited better performance than Ni/SiO2, due to the increased dispersion of Ni particles and the stronger metal-support interaction of Ni/ZSM-5, which was confirmed by the TEM and H2-TPR results. In addition, the performances of the catalysis-only (CatO), plasma-only (PlO), and in-plasma-catalysis (IPC) systems in steam reforming of different model tar compounds including benzene, toluene, furfural, naphthalene, fluorene and pyrene were compared using Ni(5 wt%)/ZSM-5. Obvious synergistic effects between DBD plasma and Ni(5 wt%)/ZSM-5 was observed for syngas production in the IPC system. |
| Sandwich membranes based on PVDF-g-4VP and surface modified graphene oxide for Cu(II) adsorption Publication date: 5 September 2019 Source: Journal of Hazardous Materials, Volume 377 Author(s): Yuexin Guo, Zhiqian Jia, Shuhuan Wang, Yabin Su, Hongcui Ma, Liguang Wang, Wei Meng AbstractUV photo-preactivation/thermally-induced grafting was employed for grafting 4-vinylpyridine (4-VP) on polyvinylidene fluoride (PVDF), and graphene oxide (GO) was modified with 4'-carboxy-2,2':6',2"-terpyridine (CTPy). Then sandwich PVDF-g-4VP/GO-CTPy/polytetrafluoroethylene (PTFE) membrane was fabricated for adsorption of Cu (II) as a model. The membrane formation, static adsorption thermodynamics, kinetics and dynamic adsorption/desorption were studied. The results showed that, the addition of polyethylene glycol (PEG 4000) as porogen can significantly increase the porosity and adsorption capacity of the membranes. The adsorption could be well described by the Langmuir model and pseudo-second-order kinetic model. The breakthrough volume and saturated volume increased with rising GO-CTPy contents. The adsorption capacity of sandwich membranes was much higher than that of mixed matrix membranes. The sandwich membrane also exhibited excellent reusability in dynamic adsorption/desorption cycles, demonstrating great potential in adsorption of trace Cu (II). Graphical abstract |
| Analysis of radially convergent tracer test in a two-zone confined aquifer with vertical dispersion effect: Asymmetrical and symmetrical transports Publication date: 5 September 2019 Source: Journal of Hazardous Materials, Volume 377 Author(s): Ching-Sheng Huang, Chenchen Tong, Wei-Shan Hu, Hund-Der Yeh, Tao Yang AbstractRadially convergent tracer test (RCT) with an extraction well and a tracer injection well is commonly conducted for determining aquifer dispersivity associated with the spreading of contamination plume. A variety of analytical models for RCT have been proposed, but the effects of skin zone and vertical dispersion are rarely explored. In addition, little attention is paid to the validity of those analytical models assuming asymmetrical tracer transport (ATT) as radially symmetrical transport (RST) toward the pumping well. This study develops a new analytical model for RCT subject to the above-mentioned effects in a confined aquifer with a skin zone around the wellbore. The Laplace-domain solution of the model for a continuous or instantaneous input is developed. A finite element solution (FES) for ATT is also developed to verify the Laplace-domain solution based on RST. Results suggest ATT can be regarded as RST in predicting the breakthrough curve (BTC) at the pumping well when four quantitative conditions are met. A lumped dimensionless parameter dominates those two effects on the BTC. Both the FES and Laplace-domain solution agree with monitored concentration data from a field RCT. |
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