共查询到20条相似文献,搜索用时 31 毫秒
1.
• BiVO4/Fe3O4/rGO has excellent photocatalytic activity under solar light radiation. • It can be easily separated and collected from water in an external magnetic field. • BiVO4/Fe3O4/0.5% rGO exhibited the highest RhB removal efficiency of over 99%. • Hole (h+) and superoxide radical (O2•−) dominate RhB photo-decomposition process. • The reusability of this composite was confirmed by five successive recycling runs. Fabrication of easily recyclable photocatalyst with excellent photocatalytic activity for degradation of organic pollutants in wastewater is highly desirable for practical application. In this study, a novel ternary magnetic photocatalyst BiVO 4/Fe 3O 4/reduced graphene oxide (BiVO 4/Fe 3O 4/rGO) was synthesized via a facile hydrothermal strategy. The BiVO 4/Fe 3O 4 with 0.5 wt% of rGO (BiVO 4/Fe 3O 4/0.5% rGO) exhibited superior activity, degrading greater than 99% Rhodamine B (RhB) after 120 min solar light radiation. The surface morphology and chemical composition of BiVO 4/Fe 3O 4/rGO were studied by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. The free radicals scavenging experiments demonstrated that hole (h +) and superoxide radical (O 2•−) were the dominant species for RhB degradation over BiVO 4/Fe 3O 4/rGO under solar light. The reusability of this composite catalyst was also investigated after five successive runs under an external magnetic field. The BiVO 4/Fe 3O 4/rGO composite was easily separated, and the recycled catalyst retained high photocatalytic activity. This study demonstrates that catalyst BiVO 4/Fe 3O 4/rGO possessed high dye removal efficiency in water treatment with excellent recyclability from water after use. The current study provides a possibility for more practical and sustainable photocatalytic process. 相似文献
2.
• Size and shape-dependent MnFe2O4 NPs were prepared via a facile method. • Ligand-exchange chemistry was used to prepare the hydrophilic MnFe2O4 NPs. • The catalytic properties of MnFe2O4 NPs toward dye degradation were fully studied. • The catalytic activities of MnFe2O4 NPs followed Michaelis–Menten behavior. • All the MnFe2O4 NPs exhibit selective degradation to different dyes. The magnetic nanoparticles that are easy to recycle have tremendous potential as a suitable catalyst for environmental toxic dye pollutant degradation. Rationally engineering shapes and tailoring the size of nanocatalysts are regarded as an effective manner for enhancing performances. Herein, we successfully synthesized three kinds of MnFe 2O 4 NPs with distinctive sizes and shapes as catalysts for reductive degradation of methylene blue, rhodamine 6G, rhodamine B, and methylene orange. It was found that the catalytic activities were dependent on the size and shape of the MnFe 2O 4 NPs and highly related to the surface-to-volume ratio and atom arrangements. Besides, all these nanocatalysts exhibit selectivity to different organic dyes, which is beneficial for their practical application in dye pollutant treatment. Furthermore, the MnFe 2O 4 NPs could be readily recovered by a magnet and reused more than ten times without appreciable loss of activity. The size and shape effects of MnFe 2O 4 nanoparticles demonstrated in this work not only accelerate further understanding the nature of nanocatalysts but also contribute to the precise design of nanoparticles catalyst for pollutant degradation. 相似文献
3.
• Strong metal-support interaction exists on Pt/Fe3O4 catalysts. • Pt metal particles facilitate the formation of oxygen vacancies on Fe3O4. • Fe3O4 supports enhance the strength of CO adsorption on Pt metal particles. ![]() The self-inhibition behavior due to CO poisoning on Pt metal particles strongly impairs the performance of CO oxidation. It is an effective method to use reducible metal oxides for supporting Pt metal particles to avoid self-inhibition and to improve catalytic performance. In this work, we used in situ reductions of chloroplatinic acid on commercial Fe 3O 4 powder to prepare heterogeneous-structured Pt/Fe 3O 4 catalysts in the solution of ethylene glycol. The heterogeneous Pt/Fe 3O 4 catalysts achieved a better catalytic performance of CO oxidation compared with the Fe 3O 4 powder. The temperatures of 50% and 90% CO conversion were achieved above 260°C and 290°C at Pt/Fe 3O 4, respectively. However, they are accomplished on Fe 3O 4 at temperatures higher than 310°C. XRD, XPS, and H 2-TPR results confirmed that the metallic Pt atoms have a strong synergistic interaction with the Fe 3O 4 supports. TGA results and transient DRIFTS results proved that the Pt metal particles facilitate the release of lattice oxygen and the formation of oxygen vacancies on Fe 3O 4. The combined results of O 2-TPD and DRIFTS indicated that the activation step of oxygen molecules at surface oxygen vacancies could potentially be the rate-determining step of the catalytic CO oxidation at Pt/Fe 3O 4 catalysts. The reaction pathway involves a Pt-assisted Mars-van Krevelen (MvK) mechanism. 相似文献
4.
• Nano Fe2O3 and N-doped graphene was prepared via a one-step ball milling method. • The maximum power density of Fe-N-G in MFC was 390% of that of pristine graphite. • Active sites like nano Fe2O3, pyridinic N and Fe-N groups were formed in Fe-N-G. • The improvement of Fe-N-G was due to full exposure of active sites on graphene. ![]() Developing high activity, low-cost and long durability catalysts for oxygen reduction reaction is of great significance for the practical application of microbial fuel cells. The full exposure of active sites in catalysts can enhance catalytic activity dramatically. Here, novel Fe-N-doped graphene is successfully synthesized via a one-step in situ ball milling method. Pristine graphite, ball milling graphene, N-doped graphene and Fe-N-doped graphene are applied in air cathodes, and enhanced performance is observed in microbial fuel cells with graphene-based catalysts. Particularly, Fe-N-doped graphene achieves the highest oxygen reduction reaction activity, with a maximum power density of 1380±20 mW/m 2 in microbial fuel cells and a current density of 23.8 A/m 2 at –0.16 V in electrochemical tests, which are comparable to commercial Pt and 390% and 640% of those of pristine graphite. An investigation of the material characteristics reveals that the superior performance of Fe-N-doped graphene results from the full exposure of Fe 2O 3 nanoparticles, pyrrolic N, pyridinic N and excellent Fe-N-G active sites on the graphene matrix. This work not only suggests the strategy of maximally exposing active sites to optimize the potential of catalysts but also provides promising catalysts for the use of microbial fuel cells in sustainable energy generation. 相似文献
5.
• Bi2O3 cannot directly activate PMS. • Bi2O3 loading increased the specific surface area and conductivity of CoOOH. • Larger specific surface area provided more active sites for PMS activation. • Faster electron transfer rate promoted the generation of reactive oxygen species. • 1O2 was identified as dominant ROS in the CoOOH@Bi2O3/PMS system. ![]() Cobalt oxyhydroxide (CoOOH) has been turned out to be a high-efficiency catalyst for peroxymonosulfate (PMS) activation. In this study, CoOOH was loaded on bismuth oxide (Bi 2O 3) using a facile chemical precipitation process to improve its catalytic activity and stability. The result showed that the catalytic performance on the 2,4-dichlorophenol (2,4-DCP) degradation was significantly enhanced with only 11 wt% Bi 2O 3 loading. The degradation rate in the CoOOH@Bi 2O 3/PMS system (0.2011 min −1) was nearly 6.0 times higher than that in the CoOOH/PMS system (0.0337 min −1). Furthermore, CoOOH@Bi 2O 3 displayed better stability with less Co ions leaching (16.4% lower than CoOOH) in the PMS system. These phenomena were attributed to the Bi 2O 3 loading which significantly increased the conductivity and specific surface area of the CoOOH@Bi 2O 3 composite. Faster electron transfer facilitated the redox reaction of Co (III) / Co (II) and thus was more favorable for reactive oxygen species (ROS) generation. Meanwhile, larger specific surface area furnished more active sites for PMS activation. More importantly, there were both non-radical ( 1O 2) and radicals (SO 4−•, O 2−•, and OH•) in the CoOOH@Bi 2O 3/PMS system and 1O 2 was the dominant one. In general, this study provided a simple and practical strategy to enhance the catalytic activity and stability of cobalt oxyhydroxide in the PMS system. 相似文献
6.
• Cu and Cr can be mostly incorporated into CuFexAlyCr2−x−yO4 with a spinel structure. • Spinel phase is the most crucial structure for Cu and Cr co-stabilization. • Compared to Al, Fe and Cr are easier to be incorporated into the spinel structure. • ‘Waste-to-resource’ by thermal process at attainable temperatures can be achieved. Chromium slag usually contains various heavy metals, making its safe treatment difficult. Glass-ceramic sintering has been applied to resolve this issue and emerged as an effective method for metal immobilization by incorporating heavy metals into stable crystal structures. Currently, there is limited knowledge about the reaction pathways adopted by multiple heavy metals and the co-stabilization functions of the crystal structure. To study the Cu/Cr co-stabilization mechanisms during thermal treatment, a simulated system was prepared using a mixture with a molar ratio of Al 2O 3:Fe 2O 3:Cr 2O 3:CuO= 1:1:1:3. The samples were sintered at temperatures 600–1300°C followed by intensive analysis of phase constitutions and microstructure development. A spinel phase (CuFe xAl yCr 2−x−yO 4) started to generate at 700°C and the incorporation of Cu/Cr into the spinel largely complete at 900°C, although the spinel peak intensity continued increasing slightly at temperatures above 900°C. Fe 2O 3/Cr 2O 3 was more easily incorporated into the spinel at lower temperatures, while more Al 2O 3 was gradually incorporated into the spinel at higher temperatures. Additionally, sintered sample microstructures became more condensed and smoother with increased sintering temperature. Cu / Cr leachability substantially decreased after Cu/Cr incorporation into the spinel phase at elevated temperatures. At 600°C, the leached ratios for Cu and Cr were 6.28% and 0.65%, respectively. When sintering temperature was increased to 1300°C, the leached ratios for all metal components in the system were below 0.2%. This study proposes a sustainable method for managing Cu/Cr co-exist slag at reasonable temperatures. 相似文献
7.
• A V2O5/TiO2 granular catalyst for simultaneous removal of NO and chlorobenzene. • Catalyst synthesized by vanadyl acetylacetonate showed good activity and stability. • The kinetic model was established and the synergetic activity was predicted. • Both chlorobenzene oxidation and SCR of NO follow pseudo-first-order kinetics. • The work is of much value to design of multi-pollutants emission control system. ![]() The synergetic abatement of multi-pollutants is one of the development trends of flue gas pollution control technology, which is still in the initial stage and facing many challenges. We developed a V 2O 5/TiO 2 granular catalyst and established the kinetic model for the simultaneous removal of NO and chlorobenzene (i.e., an important precursor of dioxins). The granular catalyst synthesized using vanadyl acetylacetonate precursor showed good synergistic catalytic performance and stability. Although the SCR reaction of NO and the oxidation reaction of chlorobenzene mutually inhibited, the reaction order of each reaction was not considerably affected, and the pseudo-first-order reaction kinetics was still followed. The performance prediction of this work is of much value to the understanding and reasonable design of a catalytic system for multi-pollutants (i.e., NO and dioxins) emission control. 相似文献
8.
• Real ML-GFW with high salinity and high organics was degraded by O3/H2O2 process. • Successful optimization of operation conditions was attained using RSM based on CCD. • Single-factor experiments in advance ensured optimal experimental conditions. • The satisfactory removal efficiency of TOC was achieved in spite of high salinity. • The initial pH plays the most significant role in the degradation of ML-GFW. ![]() The present study reports the use of the O 3/H 2O 2 process in the pretreatment of the mother liquor of gas field wastewater (ML-GFW), obtained from the multi-effect distillation treatment of the gas field wastewater. The range of optimal operation conditions was obtained by single-factor experiments. Response surface methodology (RSM) based on the central composite design (CCD) was used for the optimization procedure. A regression model with Total organic carbon (TOC) removal efficiency as the response value was established ( R2 = 0.9865). The three key factors were arranged according to their significance as: pH>H 2O 2 dosage>ozone flow rate. The model predicted that the best operation conditions could be obtained at a pH of 10.9, an ozone flow rate of 0.8 L/min, and H 2O 2 dosage of 6.2 mL. The dosing ratio of ozone was calculated to be 9.84 mg O 3/mg TOC. The maximum removal efficiency predicted was 75.9%, while the measured value was 72.3%. The relative deviation was found to be in an acceptable range. The ozone utilization and free radical quenching experiments showed that the addition of H 2O 2 promoted the decomposition of ozone to produce hydroxyl radicals (·OH). This also improved the ozone utilization efficiency. Gas chromatography-mass spectrometry (GC-MS) analysis showed that most of the organic matters in ML-GFW were degraded, while some residuals needed further treatment. This study provided the data and the necessary technical supports for further research on the treatment of ML-GFW. 相似文献
9.
• Cu2O NPs/H2O2 Fenton process was intensified by membrane dispersion. • DMAc removal was enhanced to 98% for initial DMAc of 14000 mg/L. • Analyzed time-resolved degradation pathway of DMAc under ·OH attack. ![]() High-concentration industrial wastewater containing N, N-dimethylacetamide (DMAc) from polymeric membrane manufacturer was degraded in Cu 2O NPs/H 2O 2 Fenton process. In the membrane-assisted Fenton process DMAc removal rate was up to 98% with 120 min which was increased by 23% over the batch reactor. It was found that ·OH quench time was extended by 20 min and the maximum ·OH productivity was notably 88.7% higher at 40 min. The degradation reaction rate constant was enhanced by 2.2 times with membrane dispersion ( k = 0.0349 min −1). DMAc initial concentration ( C0) and H 2O 2 flux ( Jp) had major influence on mass transfer and kinetics, meanwhile, membrane pore size ( rp) and length ( Lm) also affected the reaction rate. The intensified radical yield, fast mass transfer and nanoparticles high activity all contributed to improve pollutant degradation efficiency. Time-resolved DMAc degradation pathway was analyzed as hydroxylation, demethylation and oxidation leading to the final products of CO 2, H 2O and NO 3− (rather than NH 3 from biodegradation). Continuous process was operated in the dual-membrane configuration with in situ reaction and separation. After five cycling tests, DMAc removal was all above 95% for the initial [DMAc] 0 = 14,000 mg/L in wastewater and stability of the catalyst and the membrane maintained well. 相似文献
10.
• Bi doping in TiO2 enhanced the separation of photo-generated electron-hole. • The performance of photocatalytic degradation of MC-LR was improved. • Coexisting substances have no influence on algal removal performance. • The key reactive oxygen species were h+ and •OH in the photocatalytic process. The increase in occurrence and severity of cyanobacteria blooms is causing increasing concern; moreover, human and animal health is affected by the toxic effects of Microcystin-LR released into the water. In this paper, a floating photocatalyst for the photocatalytic inactivation of the harmful algae Microcystis aeruginosa ( M. aeruginosa) was prepared using a simple sol-gel method, i.e., coating g-C 3N 4 coupled with Bi-doped TiO 2 on Al 2O 3-modified expanded perlite (CBTA for short). The impact of different molar ratios of Bi/Ti on CBTA was considered. The results indicated that Bi doping in TiO 2 inhibited photogenerated electron-hole pair recombination. With 6 h of visible light illumination, 75.9% of M. aeruginosa (initial concentration= 2.7 × 10 6 cells/L) and 83.7% of Microcystin-LR (initial concentration= 100 μg/L) could be removed with the addition of 2 g/L CBTA-1% (i.e., Bi/Ti molar ratio= 1%). The key reactive oxygen species (ROSs) in the photocatalytic inactivation process are h + and •OH. The induction of the Bi 4+/Bi 3+ species by the incorporation of Bi could narrow the bandgap of TiO 2, trap electrons, and enhance the stability of CBTA-1% in the solutions with coexisting environmental substances. 相似文献
11.
• A novel and multi-functional clay-based oil spill remediation system was constructed. • TiO2@PAL functions as a particulate dispersant to break oil slick into tiny droplets. • Effective dispersion leads to the direct contact of TiO2 with oil pollutes directly. • TiO2 loaded on PAL exhibits efficient photodegradation for oil pollutants. • TiO2@PAL shows a typical dispersion-photocatalysis synergistic remediation. ![]() Removing spilled oil from the water surface is critically important given that oil spill accidents are a common occurrence. In this study, TiO 2@Palygorskite composite prepared by a simple coprecipitation method was used for oil spill remediation via a dispersion-photodegradation synergy. Diesel could be efficiently dispersed into small oil droplets by TiO 2@Palygorskite. These dispersed droplets had an average diameter of 20–30 mm and exhibited good time stability. The tight adsorption of TiO 2@Palygorskite on the surface of the droplets was observed in fluorescence and SEM images. As a particulate dispersant, the direct contact of TiO 2@Palygorskite with oil pollutants effectively enhanced the photodegradation efficiency of TiO 2 for oil. During the photodegradation process, •O 2−and •OH were detected by ESR and radical trapping experiments. The photodegradation efficiency of diesel by TiO 2@Palygorskite was enhanced by about 5 times compared with pure TiO 2 under simulated sunlight irradiation. The establishment of this new dispersion-photodegradation synergistic remediation system provides a new direction for the development of marine oil spill remediation. 相似文献
12.
• A novel Z-scheme Si-SnO2-TiOx with SnO2 as electron mediator is first constructed. • Transparent and conductive SnO2 can pass light through and promote charge transport. • VO from SnO2 and TiOx improve photoelectrochemical performances. • Efficient photocatalytic degradations originate from the Z scheme construction. ![]() Z-scheme photocatalysts, with strong redox ability, have a great potential for pollutants degradation. However, it is challenging to construct efficient Z-scheme photocatalysts because of their poor interfacial charge separation. Herein, by employing transparent and conductive SnO 2 as electron mediator to pass light through and promote interfacial charge transportation, a novel Z-scheme photocatalyst Si-SnO 2-TiO x (1<x<2) was constructed. The Z-scheme photocatalyst displayed an order of magnitude higher photocurrent density and a 4-fold increase in open-circuit potential compared to those of Si. Moreover, the onset potential shifted negatively for approximately 2.2 V. Benefiting from these advantages, this Z-scheme Si-SnO 2-TiO x exhibited efficient photocatalytic performance toward phenol degradation and mineralization. 75% of the phenol was degraded without bias potential and 70% of the TOC was removed during phenol degradation. Other typical pollutants such as bisphenol A and atrazine could also be degraded without bias potential. Introducing a transparent and conductive electron mediator to construct Z-scheme photocatalyst gives a new sight to the improvement of photocatalytic performance in Z scheme. 相似文献
13.
• Eco-friendly IONPs were synthesized through solvothermal method. • IONPs show very high removal efficiency for CeO2 NPs i.e. 688 mg/g. • Removal was >90% in all synthetic and real water samples. • >80% recovery of CeO2 NPs through sonication confirms reusability of IONPs. ![]() Increasing applications of metal oxide nanoparticles and their release in the natural environment is a serious concern due to their toxic nature. Therefore, it is essential to have eco-friendly solutions for the remediation of toxic metal oxides in an aqueous environment. In the present study, eco-friendly Iron Oxide Nanoparticles (IONPs) are synthesized using solvothermal technique and successfully characterized using scanning and transmission electron microscopy (SEM and TEM respectively) and powder X-Ray diffraction (PXRD). These IONPs were further utilized for the remediation of toxic metal oxide nanoparticle, i.e., CeO 2. Sorption experiments were also performed in complex aqueous solutions and real water samples to check its applicability in the natural environment. Reusability study was performed to show cost-effectiveness. Results show that these 200 nm-sized spherical IONPs, as revealed by SEM and TEM analysis, were magnetite (Fe 3O 4) and contained short-range crystallinity as confirmed from XRD spectra. Sorption experiments show that the composite follows the pseudo-second-order kinetic model. Further R2>0.99 for Langmuir sorption isotherm suggests chemisorption as probable removal mechanism with monolayer sorption of CeO 2 NPs on IONP. More than 80% recovery of adsorbed CeO 2 NPs through ultrasonication and magnetic separation of reaction precipitate confirms reusability of IONPs. Obtained removal % of CeO 2 in various synthetic and real water samples was>90% signifying that IONPs are candidate adsorbent for the removal and recovery of toxic metal oxide nanoparticles from contaminated environmental water samples. 相似文献
14.
•CeOx/GF-EP process had the better degradation efficiency than GF-EP process. •CeOx/GF-EP process had the flexible application in the pH range from 5.0 to 9.0. •CeOx could enhance surface hydrophilicity and reduce the charge-transfer resistance. •The interfacial electron transfer process was revealed. E-peroxone (EP) was one of the most attractive AOPs for removing refractory organic compounds from water, but the high energy consumption for in situ generating H 2O 2 and its low reaction efficiency for activating O 3 under acidic conditions made the obstacles for its practical application. In this study, cerium oxide was loaded on the surface of graphite felt (GF) by the hydrothermal method to construct the efficient electrode (CeO x/GF) for mineralizing carbamazepine (CBZ) via EP process. CeO x/GF was an efficient cathode, which led to 69.4% TOC removal in CeO x/GF-EP process with current intensity of 10 mA in 60 min. Moreover, CeO x/GF had the flexible application in the pH range from 5.0 to 9.0, TOC removal had no obvious decline with decrease of pH. Comparative characterizations showed that CeO x could enhance surface hydrophilicity and reduce the charge-transfer resistance of GF. About 5.4 mg/L H 2O 2 generated in CeO x/GF-EP process, which was 2.1 times as that in GF-EP process. The greater ozone utility was also found in CeO x/GF-EP process. More O 3 was activated into hydroxyl radicals, which accounted for the mineralization of CBZ. An interfacial electron transfer process was revealed, which involved the function of oxygen vacancies and Ce 3+/Ce 4+ redox cycle. CeO x/GF had the good recycling property in fifth times’ use. 相似文献
15.
• UV/O3 process had higher TAIC mineralization rate than O3 process. • Four possible degradation pathways were proposed during TAIC degradation. • pH impacted oxidation processes with pH of 9 achieving maximum efficiency. • CO32– negatively impacted TAIC degradation while HCO3– not. • Cl– can be radicals scavenger only at high concentration (over 500 mg/L Cl–). ![]() Triallyl isocyanurate (TAIC, C 12H 15N 3O 3) has featured in wastewater treatment as a refractory organic compound due to the significant production capability and negative environmental impact. TAIC degradation was enhanced when an ozone(O 3)/ultraviolet(UV) process was applied compared with the application of an independent O 3 process. Although 99% of TAIC could be degraded in 5 min during both processes, the O 3/UV process had a 70%mineralization rate that was much higher than that of the independent O 3 process (9%) in 30 min. Four possible degradation pathways were proposed based on the organic compounds of intermediate products identified during TAIC degradation through the application of independent O 3 and O 3/UV processes. pH impacted both the direct and indirect oxidation processes. Acidic and alkaline conditions preferred direct and indirect reactions respectively, with a pH of 9 achieving maximum Total Organic Carbon (TOC) removal. Both CO 32– and HCO 3– decreased TOC removal, however only CO 32– negatively impacted TAIC degradation. Effects of Cl – as a radical scavenger became more marked only at high concentrations (over 500 mg/L Cl –). Particulate and suspended matter could hinder the transmission of ultraviolet light and reduce the production of HO· accordingly. 相似文献
16.
• UASB reactor can work efficiently with high COD/SO42- ratios when SDBS exists. • Outcome of the competition between SRB and MPA was affected by SDBS. • Presence of SDBS makes methanogens with H2/CO2 as a substrate dominant. • Microbial diversity decreases in the presence of SDBS. In this study, the effects of organic sulfur on anaerobic biological processes were investigated by operating two up-flow anaerobic sludge blanket (UASB) reactors with sodium dodecylbenzene sulfonate (SDBS) as a representative of organic sulfur. The results indicated that the specific methanogenic activity (SMA) and chemical oxygen demand (COD) removal efficiency of R2 (with SDBS added) were higher than those of R1 (without SDBS) when the COD/SO 42− ratio was above 5.0. However, when the COD/SO 42− ratio was lower than 5.0, the sulfate reduction efficiency of R2 was higher than that of R1. These results and the observed SDBS transformation efficiency in anaerobic reactors indicate that low concentrations of SDBS accelerate methane production and the continuous accumulation of SDBS does not weaken the reduction of sulfate. Similarly, the calculated electron flux for a COD/SO 42− ratio of 1.0 indicates that the utilization intensity of electrons by sulfate-reducing bacteria (SRB) in R2 was 36.48% higher than that of SRB in R1 and exceeded that of methane-producing archaea (MPA) under identical working conditions. Moreover, the addition of SDBS in R2 made sulfidogenesis the dominant reaction at low COD/SO 42−, and Methanobacterium and Methanobrevibacter with H 2/CO 2 as the substrate and Desulfomicrobium were the dominant MPA and SRB, respectively. However, methanogenesis was still the dominant reaction in R1, and Methanosaeta with acetic acid as the substrate and Desulfovibrio were the dominant MPA and SRB, respectively. 相似文献
17.
• Gas diffusion electrode (GDE) is a suitable setup for practical water treatment. • Electrochemical H2O2 production is an economically competitive technology. • High current efficiency of H2O2 production was obtained with GDE at 5–400 mA/cm2. • GDE maintained high stability for H2O2 production for ~1000 h. • Electro-generation of H2O2 enhances ibuprofen removal in an E-peroxone process. ![]() This study evaluated the feasibility of electrochemical hydrogen peroxide (H 2O 2) production with gas diffusion electrode (GDE) for decentralized water treatment. Carbon black-polytetrafluoroethylene GDEs were prepared and tested in a continuous flow electrochemical cell for H 2O 2 production from oxygen reduction. Results showed that because of the effective oxygen transfer in GDEs, the electrode maintained high apparent current efficiencies (ACEs,>80%) for H 2O 2 production over a wide current density range of 5–400 mA/cm 2, and H 2O 2 production rates as high as ~202 mg/h/cm 2 could be obtained. Long-term stability test showed that the GDE maintained high ACEs (>85%) and low energy consumption (<10 kWh/kg H 2O 2) for H 2O 2 production for 42 d (~1000 h). However, the ACEs then decreased to ~70% in the following 4 days because water flooding of GDE pores considerably impeded oxygen transport at the late stage of the trial. Based on an electrode lifetime of 46 days, the overall cost for H 2O 2 production was estimated to be ~0.88 $/kg H 2O 2, including an electricity cost of 0.61 $/kg and an electrode capital cost of 0.27 $/kg. With a 9 cm 2 GDE and 40 mA/cm 2 current density, ~2–4 mg/L of H 2O 2 could be produced on site for the electro-peroxone treatment of a 1.2 m 3/d groundwater flow, which considerably enhanced ibuprofen abatement compared with ozonation alone (~43%–59% vs. 7%). These findings suggest that electrochemical H 2O 2 production with GDEs holds great promise for the development of compact treatment technologies for decentralized water treatment at a household and community level. 相似文献
18.
• Nano CaO2 is evaluated as a remediation agent for 2,4-DCP contaminated groundwater. • 2,4-DCP degradation mechanism by different Fe2+ concentration was proposed. • 2,4-DCP was not degraded in the system for solution pH>10. • The 2,4-DCP degradation area is inconsistent with the nano CaO2 distribution area. This study evaluates the applicability of nano-sized calcium peroxide (CaO 2) as a source of H 2O 2 to remediate 2,4-dichlorophenol (2,4-DCP) contaminated groundwater via the advanced oxidation process (AOP). First, the effect and mechanism of 2,4-DCP degradation by CaO 2 at different Fe concentrations were studied (Fenton reaction). We found that at high Fe concentrations, 2,4-DCP almost completely degrades via primarily the oxidation of •OH within 5 h. At low Fe concentrations, the degradation rate of 2,4-DCP decreased rapidly. The main mechanism was the combined action of •OH and O 2•−. Without Fe, the 2,4-DCP degradation reached 13.6% in 213 h, primarily via the heterogeneous reaction on the surface of CaO 2. Besides, 2,4-DCP degradation was significantly affected by solution pH. When the solution pH was>10, the degradation was almost completely inhibited. Thus, we adopted a two-dimensional water tank experiment to study the remediation efficiency CaO 2 on the water sample. We noticed that the degradation took place mainly in regions of pH<10 (i.e., CaO 2 distribution area), both upstream and downstream of the tank. After 28 days of treatment, the average 2,4-DCP degradation level was ≈36.5%. Given the inadequacy of the results, we recommend that groundwater remediation using nano CaO 2: (1) a buffer solution should be added to retard the rapid increase in pH, and (2) the nano CaO 2 should be injected copiously in batches to reduce CaO 2 deposition. 相似文献
19.
• The coupling of oxidants with ZVI overcome the impedance of ZVI passive layer. • ZVI/oxidants system achieved fast and long-effective removal of contaminants. • Multiple mechanisms are involved in contaminants removal by ZVI/oxidant system. • ZVI/Oxidants did not change the reducing property of ORP in the fixed-bed system. ![]() Zero-valent iron (ZVI) technology has recently gained significant interest in the efficient sequestration of a wide variety of contaminants. However, surface passivation of ZVI because of its intrinsic passive layer would lead to the inferior reactivity of ZVI and its lower efficacy in contaminant removal. Therefore, to activate the ZVI surface cheaply, continuously, and efficiently is an important challenge that ZVI technology must overcome before its wide-scale application. To date, several physical and chemical approaches have been extensively applied to increase the reactivity of the ZVI surface toward the elimination of broad-spectrum pollutants. Nevertheless, these techniques have several limitations such as low efficacy, narrow working pH, eco-toxicity, and high installation cost. The objective of this mini-review paper is to identify the critical role of oxygen in determining the reactivity of ZVI toward contaminant removal. Subsequently, the effect of three typical oxidants (H 2O 2, KMnO 4, and NaClO) on broad-spectrum contaminants removal by ZVI has been documented and discussed. The reaction mechanism and sequestration efficacies of the ZVI/oxidant system were evaluated and reviewed. The technical basis of the ZVI/oxidant approach is based on the half-reaction of the cathodic reduction of the oxidants. The oxidants commonly used in the water treatment industry, i.e., NaClO, O 3, and H 2O 2, can be served as an ideal coupling electron receptor. With the combination of these oxidants, the surface corrosion of ZVI can be continuously driven. The ZVI/oxidants technology has been compared with other conventional technologies and conclusions have been drawn. 相似文献
20.
• Mechanism of DCM disproportionation over mesoporous TiO2 was studied. • DCM was completely eliminated at 350℃ under 1 vol.% humidity. • Anatase (001) was the key for disproportionation. • A competitive oxidation route co-existed with disproportionation. • Disproportionation was favored at low temperature. ![]() Mesoporous TiO 2 was synthesized via nonhydrolytic template-mediated sol-gel route. Catalytic degradation performance upon dichloromethane over as-prepared mesoporous TiO 2, pure anatase and rutile were investigated respectively. Disproportionation took place over as-made mesoporous TiO 2 and pure anatase under the presence of water. The mechanism of disproportionation was studied by in situ FTIR. The interaction between chloromethoxy species and bridge coordinated methylenes was the key step of disproportionation. Formate species and methoxy groups would be formed and further turned into carbon monoxide and methyl chloride. Anatase (001) played an important role for disproportionation in that water could be dissociated into surface hydroxyl groups on such structure. As a result, the consumed hydroxyl groups would be replenished. In addition, there was another competitive oxidation route governed by free hydroxyl radicals. In this route, chloromethoxy groups would be oxidized into formate species by hydroxyl radicals transfering from the surface of TiO 2. The latter route would be more favorable at higher temperature. 相似文献
|