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1.
• UV/VUV/I– induces substantial H2O2 and IO3– formation, but UV/I– does not. • Increasing DO level in water enhances H2O2 and iodate productions. • Increasing pH decreases H2O2 and iodate formation and also photo-oxidation. • The redox potentials of UV/VUV/I– and UV/VUV changes with pH changes. • The treatability of the UV/VUV/I– process was stronger than UV/VUV at pH 11.0. Recently, a photochemical process induced by ultraviolet (UV), vacuum UV (VUV), and iodide (I –) has gained attention for its robust potential for contaminant degradation. However, the mechanisms behind this process remain unclear because both oxidizing and reducing reactants are likely generated. To better understand this process, this study examined the evolutions of hydrogen peroxide (H 2O 2) and iodine species (i.e., iodide, iodate, and triiodide) during the UV/VUV/I – process under varying pH and dissolved oxygen (DO) conditions. Results show that increasing DO in water enhanced H 2O 2 and iodate production, suggesting that high DO favors the formation of oxidizing species. In contrast, increasing pH (from 6.0 to 11.0) resulted in lower H 2O 2 and iodate formation, indicating that there was a decrease of oxidative capacity for the UV/VUV/I – process. In addition, difluoroacetic acid (DFAA) was used as an exemplar contaminant to verify above observations. Although its degradation kinetics did not follow a constant trend as pH increases, the relative importance of mineralization appeared declining, suggesting that there was a redox transition from an oxidizing environment to a reducing environment as pH rises. The treatability of the UV/VUV/I – process was stronger than UV/VUV under pH of 11.0, while UV/VUV process presented a better performance at pH lower than 11.0. 相似文献
2.
MC-LR removal performances under different AOPs were compared systematically. Higher removal efficiency and synergistic effects were obtained by combined process. The acute biotoxicity raised in different degrees after oxidation. ![]() Microcystin-LR attracts attention due to its high toxicity, high concentration and high frequency. The removal characteristics of UV/H 2O 2 and O 3/H 2O 2 advanced oxidation processes and their individual process for MC-LR were investigated and compared in this study. Both the removal efficiencies and rates of MC-LR as well as the biotoxicity of degradation products was analyzed. Results showed that the UV/H 2O 2 process and O 3/H 2O 2 were effective methods to remove MC-LR from water, and they two performed better than UV-, O 3-, H 2O 2-alone processes under the same conditions. The effects of UV intensity, H 2O 2 concentration and O 3 concentration on the removal performance were explored. The synergistic effects between UV and H 2O 2, O 3 and H 2O 2 were observed. UV dosage of 1800 mJ·cm −2 was required to remove 90% of 100 mg·L −1 MC-LR, which amount significantly decreased to 500 mJ·cm −2 when 1.7 mg·L −1 H 2O 2 was added. 0.25 mg·L −1 O 3, or 0.125 mg·L −1 O 3 with 1.7 mg·L −1 H 2O 2 was needed to reach 90% removal efficiency. Furthermore, the biotoxicity results about these UV/H 2O 2, O 3/H 2O 2 and O 3-alone processes all present rising trends with oxidation degree of MC-LR. Biotoxicity of solution, equivalent to 0.01 mg·L −1 Zn 2+, raised to 0.05 mg·L −1 Zn 2+ after UV/H 2O 2 or O 3/H 2O 2 reaction. This phenomenon may be attributed to the aldehydes and ketones with small molecular weight generated during reaction. Advice about the selection of MC-LR removal methods in real cases was provided. 相似文献
3.
In the present study, the decomposition rates of carbon tetrachloride (CCl 4) and 2,4-dichlorophenol (2,4-DCP) in water by the ultraviolet (UV) light irradiation alone and H 2O 2/UV were experimentally investigated. The detailed experimental studies have been conducted for examining treatment capacities of the two different ultraviolet light sources (low and medium pressure Hg arc) in H 2O 2/UV processes. The low or medium UV lamp alone resulted in a 60%–90% decomposition of 2,4-DCP while a slight addition of H 2O 2 resulted in a drastic enhancement of the 2,4-DCP decomposition rate. The decomposition rate of 2,4-DCP with the medium pressure UV lamp alone was about 3–6 times greater than the low pressure UV lamp alone. In the direct photolysis of aqueous CCl 4, the medium pressure UV lamp had advantage over the low pressure UV lamp because the molar extinction coefficient of CCl 4 at shorter wavelength (210–220 nm) is about 20 to 50 times higher than that at 254 nm. However, adding H 2O 2 to the medium pressure UV lamp system rendered a negative oxidation rate because H 2O 2 acted as a UV absorber being competitive with CCl 4 due to negligible reaction between CCl 4 and OH radicals. The results from the present study indicated significant influence of the photochemical properties of the target contaminants on the photochemical treatment characteristics for designing cost-effective UV-based degradation of toxic contaminants. 相似文献
4.
Aqueous solutions of phenol were oxidized by hydrogen peroxide assisted by microwave (MW) irradiation. A simple kinetic model for the overall degradation of phenol in the presence of excess H 2O 2 is proposed in which the degradation rate of phenol is expressed as a linear function of the concentrations of phenol and H 2O 2. A detailed parametric study showed that the degradation rate of phenol increased with increasing [H 2O 2] until saturation was observed. Phenol degradation followed apparent zero-order kinetics under MW radiation or H 2O 2 oxidation. However, after 90 min of irradiation, the observed kinetics shifted to pseudo first order. The overall reaction rates were significantly enhanced in the combined MW/H 2O 2 system, mainly because microwave could accelerate H 2O 2 to generate hydroxyl radical ( ·OH) and other reactive oxygen intermediates. The observed synergetic effects of the MW/H 2O 2 process resulted in an increased in the net reaction rate by a factor of 5.75. When hydrogen peroxide is present in a large stoichiometric excess, the time required to achieve complete mineralization is reduced significantly. 相似文献
5.
● Bimetallic oxide composite catalyst was designed for the urea-based SCR process. ● Surface chemical state and typical microstructure of catalyst was determined. ● Reaction route was improved based on intermediates and active site identification. ● TiO2@Al2O3 presents an obvious promotion for urea hydrolysis. As a promising option to provide gaseous NH 3 for SCR system, catalytic urea hydrolysis has aroused great attention, and improving surface area and activity of catalysis are the crucial issues to be solved for efficient urea hydrolysis. Therefore, a composite metal oxide (TiO 2@Al 2O 3) catalyst was prepared by a simple hydrothermal method, with mesoporous alumina (γ-Al 2O 3) as substrate. The results verify the mesoporous structure and submicron cluster of TiO 2@Al 2O 3, with exposed crystal faces of (101) and (400) for TiO 2 and γ-Al 2O 3, respectively. The electronegativity difference of Ti 4+ and Al 3+ changes the charge distribution scheme around the interface, which provides abundant acid/base sites to boost the urea hydrolysis. Consequently, for an optimal proportioning with nano TiO 2 content at 10 wt.%, the hydrolysis efficiency can reach up to 35.2 % at 100 °C in 2 h, increasing by ~7.1 % than that of the blank experiment. 13C NMR spectrum measurements provide the impossible intermediate species during urea hydrolysis. Theoretical calculations are performed to clarify the efficient H 2O decomposition at the interface of TiO 2@Al 2O 3. The result offers a favorable technology for energy-efficiency urea hydrolysis. 相似文献
6.
A solution of atrazine in a TiO 2 suspension, an endocrine disruptor in natural water, was tentatively treated by microwave-assisted photocatalytic technique. The effects of mannitol, oxygen, humic acid, and hydrogen dioxide on the photodegradation rate were explored. The results could be deduced as follows: the photocatalytic degradation of atrazine fits the pseudo-first-order kinetic well with k = 0.0328 s −1, and ·OH was identified as the dominant reactant. Photodegradation of atrazine was hindered in the presence of humic acid, and the retardation effect increased as the concentration of humic acid increased. H 2O 2 displayed a significant negative influence on atrazine photocatalysis efficiency. Based on intermediates identified with gas chromatography-mass spectrometry (GC-MS) and Liquid chromatography-mass spectrometry (LC-MS/MS) techniques, the main degradation routes of atrazine are proposed. 相似文献
7.
• 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
8.
● Appreciable H2O2 production rate was achieved in MRCs utilizing NH4HCO3 solutions. ● Carbon black outperformed activated carbon as the catalyst for H2O2 production. ● The optimum carbon black loading for H2O2 production on air-cathode was 10 mg/cm2. ● The optimum number of cell pairs was determined to be three. ● A maximum power density of 980 mW/m2 was produced by MRCs with 5 cell pairs. H 2O 2 was produced at an appreciable rate in microbial reverse-electrodialysis cells (MRCs) coupled with thermolytic solutions, which can simultaneously capture waste heat as electrical energy. To determine the optimal cathode and membrane stack configurations for H 2O 2 production, different catalysts, catalyst loadings and numbers of membrane cell pairs were tested. Carbon black (CB) outperformed activated carbon (AC) for H 2O 2 production, although AC showed higher catalytic activity for oxygen reduction. The optimum CB loading was 10 mg/cm 2 in terms of both the H 2O 2 production rate and power production. The optimum number of cell pairs was determined to be three based on a tradeoff between H 2O 2 production and capital costs. A H 2O 2 production rate as high as 0.99 ± 0.10 mmol/(L·h) was achieved with 10 mg/cm 2 CB loading and 3 cell pairs, where the H 2O 2 recovery efficiency was 52 ± 2% and the maximum power density was 780 ± 37 mW/m 2. Increasing the number of cell pairs to five resulted in an increase in maximum power density (980 ± 21 mW/m 2) but showed limited effects on H 2O 2 production. These results indicated that MRCs can be an efficient method for sustainable H 2O 2 production. 相似文献
9.
• 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
10.
• 4-chlorophenol biodegradation could be enhanced in Fe2O3 coupled anaerobic system. • Metabolic activity and electron transport could be improved by Fe2O3 nanoparticles. • Functional microbial communities could be enriched in coupled anaerobic system. • Possible synergistic mechanism involved in enhanced dechlorination was proposed. Fe 2O 3 nanoparticles have been reported to enhance the dechlorination performance of anaerobic systems, but the underlying mechanism has not been clarified. This study evaluated the technical feasibility, system stability, microbial biodiversity and the underlying mechanism involved in a Fe 2O 3 nanoparticle-coupled anaerobic system treating 4-chlorophenol (4-CP) wastewater. The results demonstrated that the 4-CP and total organic carbon (TOC) removal efficiencies in the Fe 2O 3-coupled up-flow anaerobic sludge blanket (UASB) were always higher than 97% and 90% during long-term operation, verifying the long-term stability of the Fe 2O 3-coupled UASB. The 4-CP and TOC removal efficiencies in the coupled UASB increased by 42.9±0.4% and 27.5±0.7% compared to the control UASB system. Adding Fe 2O 3 nanoparticles promoted the enrichment of species involved in dechlorination, fermentation, electron transfer and acetoclastic methanogenesis, and significantly enhanced the extracellular electron transfer ability, electron transport activity and conductivity of anaerobic sludge, leading to enhanced 4-CP biodegradation performance. A possible synergistic mechanism involved in enhanced anaerobic 4-CP biodegradation by Fe 2O 3 nanoparticles was proposed. 相似文献
11.
Antibiotic-resistant bacteria and antibiotic resistance genes are in water bodies. UV/chlorination method is better to remove ARGs than UV or chlorination alone. Research on UV/hydrogen peroxide to eliminate ARGs is forthcoming. UV-based photocatalytic processes are effective to degrade ARGs. ![]() Antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have been recognized as one of the biggest public health issues of the 21st century. Both ARB and ARGs have been determined in water after treatment with conventional disinfectants. Ultraviolet (UV) technology has been seen growth in application to disinfect the water. However, UV method alone is not adequate to degrade ARGs in water. Researchers are investigating the combination of UV with other oxidants (chlorine, hydrogen peroxide (H 2O 2), peroxymonosulfate (PMS), and photocatalysts) to harness the high reactivity of produced reactive species (Cl·, ClO·, Cl 2· −, ·OH, and SO 4· −) in such processes with constituents of cell (e.g., deoxyribonucleic acid (DNA) and its components) in order to increase the degradation efficiency of ARGs. This paper briefly reviews the current status of different UV-based treatments (UV/chlorination, UV/H 2O 2, UV/PMS, and UV-photocatalysis) to degrade ARGs and to control horizontal gene transfer (HGT) in water. The review also provides discussion on the mechanism of degradation of ARGs and application of q-PCR and gel electrophoresis to obtain insights of the fate of ARGs during UV-based treatment processes. 相似文献
12.
• UVA pre-irradiation to TiO2 NPs enhanced its toxicity toward plant A. cepa. • UVA TiO2 NPs increased intracellular ROS, resulting in more cell damage. • Cell death enhanced cell permeability and increased uptake of NPs. • Being highly toxic (EC50 = 0.097 µmol/L), TC did not increase ROS generation. • Even at a low dose, TC enhanced the toxic potential of TiO2 NPs significantly. ![]() Usage of titanium dioxide nanoparticles (TiO 2 NPs) and tetracycline (TC) has increased significantly in the present era. This leads to their release and accumulation in the environment. Both the compounds, individually, can have adverse toxic effects on the plants. Their binary mixtures can increase this degree of damage. The present study aimed to evaluate the toxicity of both the contaminants in individual and binary mixtures in Allium cepa. Further, the toxicity of TiO 2 NPs upon UVA pre-irradiation was also measured. Results showed that UVA pre-irradiated NPs (UVA-TiO 2 NPs) had a significant decrease in cell viability than their non-irradiated counterparts (NI-TiO 2), denoting an increase in photocatalytic activity upon UVA pre-irradiation. Very low concentrations of TC ( EC10 = 0.016 µmol/L) mixed with TiO 2 NPs significantly increased the toxicity for both UVA-TiO 2 and NI-TiO 2 NPs. Intracellular ROS generation was significantly high for UVA-TiO 2 NPs. However, TC did not have any effects on ROS production. Both the compounds exhibited genotoxic potential in A. cepa. Different chromosomal abnormalities like anaphase bridges, telophase bridges, laggard chromosomes, binucleate cells, etc. were observed. The binary mixture of UVA-TiO 2 NPs and TC showed the highest chromosomal aberrations (64.0%±1.26%) than the mixture with NI-TiO 2 or the individual contaminants. This decreased significantly after recovery (46.8%±1.92%), denoting the self-repair processes. This study proved that UVA-TiO 2 NPs were more toxic and could be enhanced further when mixed with a sub-lethal concentration of TC. This work will help to assess the risk of both compounds in the environment. 相似文献
13.
• 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
14.
In this study, palladium-loaded titania nanotubes was fabricated on a titanium plate (Pd/TiO 2NTs/Ti) for efficient electrodechlorination of 2,4-chlorophenol with a mild pH condition. The nature of Pd/TiO 2NTs/Ti electrodes was characterized by field-emission scanning electron microscope (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) techniques. The characterization results indicated the generation of Pd 0 nanoparticles which were evenly dispersed on titania nanotubes arrays on the Pd/TiO 2NTs/Ti surface. An effective degradation efficiency of up to 91% was achieved within 60 min at cathode potential of −0.7 V ( vs. SCE) and initial pH of 5.5. The effects of the applied cathode potential and initial pH on the degradation efficiency were studied. A near neutral condition was more favorable since very low and very high pHs were not conducive to the dechlorination process. Furthermore, the intermediates analysis showed that the Pd/TiO 2NTs/Ti electrode could completely remove chlorine from 2, 4-dichlorophenol since only phenol was detected as the byproduct and the concentration of released chlorine ions indicated near-complete dechlorination. This work presents a good alternative technique for eliminating persistent chlorophenols in polluted wastewater without maintaining strong acidic environment. 相似文献
15.
The effect of ion-doping on TiO 2 nanotubes were investigated to obtain the optimal TiO 2 nanotubes for the effective decomposition of humic acids (HA) through O 3/UV/ion-doped TiO 2 process. The experimental results show that changing the calcination temperature, which changed the weight fractions of the anatase phase, the average crystallite sizes, the Brunauer-Emmett-Teller surface area, and the energy band gap of the catalyst, affected the photocatalytic activity of the catalyst. The ionic radius, valence state, and configuration of the dopant also affected the photocatalytic activity. The photocatalytic activities of the catalysts on HA removal increased when Ag +, Al 3+, Cu 2+, Fe 3+, V 5+, and Zn 2+ were doped into the TiO 2 nanotubes, whereas such activities decreased as a result of Mn 2+- and Ni 2+-doping. In the presence of 1.0 at.% Fe 3+-doped TiO 2 nanotubes calcined at 550°C, the removal efficiency of HA was 80% with a pseudo-first-order rate constant of 0.158 min −1. Fe 3+ in TiO 2 could increase the generation of ·OH, which could remove HA. However, Fe 3+ in water cannot function as a shallow trapping site for electrons or holes. 相似文献
16.
● The concentrations of 61 progesterones in HWW, PFTE, SBTE were evaluated. ● The removal efficiencies of progesterones by PFT and SBT were identified. ● Compared the removal efficiencies of progeste rones in five disinfection processes. Progesterones are ubiquitous in hospital wastewater (HWW) with concentrations much higher than those of estrogens and androgens. To ensure that these water systems are safe to use, disinfection is crucial during HWW treatment by providing “front line” defense against biological contaminations. Here, five disinfection processes, namely, chlorine (Cl 2), chlorine dioxide (ClO 2), ozone (O 3), ultraviolet (UV)), and UV/chlorine (UV/Cl 2), were selected to investigate their removal efficiencies for progesterones in primary filtration and secondary biological treatment effluents. There were 61 natural and synthetic progesterones detected in HWW, with the natural progesterones being the main components with a concentration of 845.51 ng/L and contributing to 75.08% of the total progesterones. The primary filtration treatment presented insignificant removal effects on the progesterones, while the secondary biological treatment significantly reduced the progesterone content by biodegradation. The order of removal efficiencies of total progesterones by different disinfection processes was UV/Cl 2 > Cl 2 > O 3 > ClO 2 > UV. UV/Cl 2 showed the highest removal efficiency against progesterones mainly due to the activation of Cl 2 by ultraviolet (UV) photolysis, which helps open the heterocyclic, aromatic, and phenolic rings, thus accelerating progesterone degradation. In addition, the removal efficiencies of natural progesterones in the five disinfection processes were higher than those of synthetic progesterones (progesterone derivatives, 19-nortestosterone derivatives, and 17α-hydroxyprogesterone derivatives). 相似文献
17.
• Regulation of redox conditions promotes the generation of free radicals on HM. • HM-PFRs can be fractionated into active and inactive types depending on stability. • The newly produced PFRs readily release electrons to oxygen and generate ROS. • PFR-induced ROS mediate the transformation of organic contaminants adsorbed on HM. ![]() The role of humic substance-associated persistent free radicals (PFRs) in the fate of organic contaminants under various redox conditions remains unknown. This study examined the characterization of original metal-free peat humin (HM), and HM treated with varying concentrations of H 2O 2 and L-ascorbic acid (VC) (assigned as H 2O 2-HM and VC-HM). The concentration of PFRs in HM increased with the addition of VC/H 2O 2 at concentrations less than 0.08 M. The evolution of PFRs in HM under different environmental conditions (e.g., oxic/anoxic and humidity) was investigated. Two types of PFRs were detected in HM: a relatively stable radical existed in the original sample, and the other type, which was generated by redox treatments, was relatively unstable. The spin densities of VC/H 2O 2-HM readily returned to the original value under relatively high humidity and oxic conditions. During this process, the HM-associated “unstable” free radicals released an electron to O 2, inducing the formation of reactive oxygen species (ROS, i.e., •OH and •O 2−). The generated ROS promoted the degradation of polycyclic aromatic hydrocarbons based on the radical quenching measurements. The transformation rates followed the order naphthalene>phenanthrene>anthracene>benzo[a]pyrene. Our results provide valuable insight into the HM-induced transformation of organic contaminants under natural conditions. 相似文献
18.
Phenol removal by n/m Fe in the presence of H 2O 2 was highly effective.
Increasing the amounts of n/m Fe and H 2O 2?increased the phenol removal rate.
Phenol removal was decreased with an increase in the concentration of phenol.
The natural pH (6.9) of the solution was highly effective for phenol removal.
The pseudo-first-order kinetics was best fitted for the degradation of phenol.
The study investigates the magnetic separation of Fe from automobile shredder residue (ASR) (<0.25 mm) and its application for phenol degradation in water. The magnetically separated Fe was subjected to an ultrasonically assisted acid treatment, and the degradation of phenol in an aqueous solution using nano/micro-size Fe (n/m Fe) was investigated in an effort to evaluate the possibility of utilizing n/m Fe to remove phenol from wastewater. The prepared n/m Fe was analyzed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The effects of the dosages of n/mFe, pH, concentration of phenol and amount of H 2O 2 on phenol removal were evaluated. The results confirm that the phenol degradation rate was improved with an increase in the dosages of n/mFe and H 2O 2; however, the rate is reduced when the phenol concentration is higher. The degradation of phenol by n/mFe followed the pseudo-first-order kinetics. The value of the reaction rate constant (k) was increased as the amounts of n/m Fe and H 2O 2 increased. Conversely, the value of k was reduced when the concentration of phenol was increased. The probable mechanism behind the degradation of phenol by n/m Fe is the oxidation of phenol through hydroxyl radicals which are produced during the reaction between H 2O 2 and n/m Fe. 相似文献
19.
CNT-TiO2 composite is used to activate PMS under UV-light assistance. Superior performance is due to the enhanced electron-transfer ability of CNT. SO4•−, •OH and 1O2 play key roles in the degradation of organic pollutants. ![]() In this work, a UV-light assisted peroxymonosulfate (PMS) activation system was constructed with the composite catalyst of multi-walled carbon nanotubes (CNT) - titanium dioxide (TiO 2). Under the UV light irradiation, the photoinduced electrons generated from TiO 2 could be continuously transferred to CNT for the activation of PMS to improve the catalytic performance of organic pollutant degradation. Meanwhile, the separation of photoinduced electron-hole pairs could enhance the photocatalysis efficiency. The electron spin resonance spectroscopy (EPR) and quenching experiments confirmed the generation of sulfate radical (SO 4• −), hydroxyl radical (•OH) and singlet oxygen ( 1O 2) in the UV/PMS/20%CNT-TiO 2 system. Almost 100% phenol degradation was observed within 20 min UV-light irradiation. The kinetic reaction rate constant of the UV/PMS/20%CNT-TiO 2 system (0.18 min −1) was 23.7 times higher than that of the PMS/Co 3O 4 system (0.0076 min −1). This higher catalytic performance was ascribed to the introduction of photoinduced electrons, which could enhance the activation of PMS by the transfer of electrons in the UV/PMS/CNT-TiO 2 system. 相似文献
20.
• 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
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