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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.
• 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
3.
• The MCNZVI is prepared as an interesting material for PS activation. • Graphitized carbon shells facilitate electron transfer from Fe0. • The MCNZVI exhibits excellent performance to degrade RB5 by 1O2. • The MCNZVI has high stability and reusability in the oxidation system. High-efficiency and cost-effective catalysts with available strategies for persulfate (PS) activation are critical for the complete mineralization of organic contaminants in the environmental remediation and protection fields. A nanoscale zero-valent iron-embedded modified mesoporous carbon (MCNZVI) with a core-shell structure is synthesized using the hydrothermal synthesis method and high-temperature pyrolysis. The results showed that nZVI could be impregnated within mesoporous carbon frameworks with a comparatively high graphitization degree, rich nitrogen doping content, and a large surface area and pore volume. This material was used as a persulfate activator for the oxidation removal of Reactive Black 5 (RB5). The effects of the material dosage, PS concentration, pH, and some inorganic anions (i.e., Cl −, SO 42−) on RB5 degradation were then investigated. The highest degradation efficiency (97.3%) of RB5 was achieved via PS (20 mmol/L) activation by the MCNZVI (0.5 g/L). The pseudo-first-order kinetics ( k = 2.11 × 10 −2 min −1) in the MCNZVI/PS (0.5 g/L, 20 mmol/L) was greater than 100 times than that in the MCNZVI and PS. The reactive oxygen species (ROS), including 1O 2, SO 4·−, HO ·, and ·O 2−, were generated by PS activation with the MCNZVI. Singlet oxygen was demonstrated to be the primary ROS responsible for the RB5 degradation. The MCNZVI could be reused and regenerated for recycling. This work provides new insights into PS activation to remove organic contamination. 相似文献
4.
• 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
5.
• Ascomycota was the predominant phylum in sanitary landfill fungal communities. • Saprophytic fungi may be of special importance in landfill ecology. • Both richness and diversity of fungal community were lower in leachate than refuse. • Physical habitat partly contributed to the geographic variance of fungal community. • NO3− was considered the most significant abiotic factor shaping fungal community. ![]() Land filling is the main method to dispose municipal solid waste in China. During the decomposition of organic waste in landfills, fungi play an important role in organic carbon degradation and nitrogen cycling. However, fungal composition and potential functions in landfill have not yet been characterized. In this study, refuse and leachate samples with different areas and depths were taken from a large sanitary landfill in Beijing to identify fungal communities in landfills. In high-throughput sequencing of ITS region, 474 operational taxonomic units (OTUs) were obtained from landfill samples with a cutoff level of 3% and a sequencing depth of 19962. The results indicates that Ascomycota, with the average relative abundance of 84.9%, was the predominant phylum in landfill fungal communities. At the genus level, Family Hypocreaceae unclassified (15.7%), Fusarium (9.9%) and Aspergillus (8.3%) were the most abundant fungi found in the landfill and most of them are of saprotrophic lifestyle, which plays a big role in nutrient cycling in ecosystem. Fungi existed both in landfilled refuse and leachate while both the richness and evenness of fungal communities were higher in the former. In addition, fungal communities in landfilled refuse presented geographic variances, which could be partly attributed to physical habitat properties (pH, dissolved organic carbon, volatile solid, NH 4+, NO 2− and NO 3−), while NO 3− was considered the most significant factor ( p<0.05) in shaping fungal community. 相似文献
6.
• 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
7.
•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
8.
• Complete CT degradation was achieved by employing HA to CP/Fe(II)/FA process. • Quantitative detection of Fe(II) regeneration and HO• production was investigated. • Benzoic acid outcompeted FA for the reaction with HO•. • CO2•− was the dominant reductive radical for CT removal. • Effects of solution matrix on CT removal were conducted. ![]() Hydroxyl radicals (HO•) show low reactivity with perchlorinated hydrocarbons, such as carbon tetrachloride (CT), in conventional Fenton reactions, therefore, the generation of reductive radicals has attracted increasing attention. This study investigated the enhancement of CT degradation by the synergistic effects of hydroxylamine (HA) and formic acid (FA) (initial [CT] = 0.13 mmol/L) in a Fe(II) activated calcium peroxide (CP) Fenton process. CT degradation increased from 56.6% to 99.9% with the addition of 0.78 mmol/L HA to the CP/Fe(II)/FA/CT process in a molar ratio of 12/6/12/1. The results also showed that the presence of HA enhanced the regeneration of Fe(II) from Fe(III), and the production of HO• increased one-fold when employing benzoic acid as the HO• probe. Additionally, FA slightly improves the production of HO•. A study of the mechanism confirmed that the carbon dioxide radical (CO 2• −), a strong reductant generated by the reaction between FA and HO•, was the dominant radical responsible for CT degradation. Almost complete CT dechlorination was achieved in the process. The presence of humic acid and chloride ion slightly decreased CT removal, while high doses of bicarbonate and high pH inhibited CT degradation. This study helps us to better understand the synergistic roles of FA and HA for HO• and CO 2• − generation and the removal of perchlorinated hydrocarbons in modified Fenton systems. 相似文献
9.
• 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
10.
• Microbes enhance denitrification under varying DO concentrations and SIF dosages. • Abiotic nitrate reduction rates are proportional to SIF age and dosage. • Over 80% of the simultaneously loaded NO3−-N and PO43− is removed biologically. ![]() This study focuses on identifying the factors under which mixed microbial seeds assist bio-chemical denitrification when Scrap Iron Filings (SIF) are used as electron donors and adsorbents in low C/N ratio waters. Batch studies were conducted in abiotic and biotic reactors containing fresh and aged SIF under different dissolved oxygen concentrations with NO 3−-N and/or PO 43- influent(s) and their nitrate/phosphate removal and by-product formations were studied. Batch reactors were seeded with a homogenized mixed microbial inoculum procured from natural sludges which were enriched over 6 months under denitrifying conditions in the presence of SIF. Results indicated that when influent containing 40 mg/L of NO 3−-N was treated with 5 g SIF, 79.9% nitrate reduction was observed in 8 days abiotically and 100% removal was accomplished in 20 days when the reactor was seeded. Both abiotic and seeded reactors removed more than 92% PO 43− under high DO conditions in 12 days. Abiotic and biochemical removal of NO 3−-N and abiotic removal of PO 43− were higher under independent NO 3−-N/PO 43− loading, while 99% PO 43- was removed biochemically under combined NO 3−-N and PO 43− loading. This study furthers the understandings of nitrate and phosphate removal in Zero Valent Iron (ZVI) assisted mixed microbial systems to encourage the application of SIF-supported bio-chemical processes in the simultaneous removals of these pollutants. 相似文献
11.
• 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
12.
• 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
13.
• Nano zero-valent manganese (nZVMn, Mn0) is synthesized via borohydrides reduction. • Mn0 combined with persulfate/hypochlorite is effective for Tl removal at pH 6-12. • Mn0 can activate persulfate to form hydroxyl and sulfate radicals. • Oxidation-induced precipitation and surface complexation contribute to Tl removal. • Combined Mn0-oxidants process is promising in the environmental field. ![]() Nano zero-valent manganese (nZVMn, Mn 0) was prepared through a borohydride reduction method and coupled with different oxidants (persulfate (S 2O 82−), hypochlorite (ClO −), or hydrogen peroxide (H 2O 2)) to remove thallium (Tl) from wastewater. The surface of Mn 0 was readily oxidized to form a core-shell composite (MnO x@Mn 0), which consists of Mn 0 as the inner core and MnO x (MnO, Mn 2O 3, and Mn 3O 4) as the outer layer. When Mn 0 was added alone, effective Tl(I) removal was achieved at high pH levels (>12). The Mn 0-H 2O 2 system was only effective in Tl(I) removal at high pH (>12), while the Mn 0-S 2O 82− or Mn 0-ClO − system had excellent Tl(I) removal (>96%) over a broad pH range (4–12). The Mn 0-S 2O 82− oxidation system provided the best resistance to interference from an external organic matrix. The isotherm of Tl(I) removal through the Mn 0-S 2O 82− system followed the Freundlich model. The Mn 0 nanomaterials can activate persulfate to produce sulfate radicals and hydroxyl radicals. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy suggested that oxidation-induced precipitation, surface adsorption, and electrostatic attraction are the main mechanisms for Tl(I) removal resulting from the combination of Mn 0 and oxidants. Mn 0 coupled with S 2O 82−/ClO − is a novel and effective technique for Tl(I) removal, and its application in other fields is worthy of further investigation. 相似文献
14.
• Humification evolution was identified with non-destructive characterization method. • Humification process from precursors to fulvic and humic acid was confirmed. • MnO2 alone had limited oxidation ability to form HA. • MnO2 played a key role as a catalyst to transform FA to HA in the presence of O2. • MnO2 could affect the structure of the humification products. ![]() Abiotic humification is important in the formation and evolution of organic matter in soil and compost maturing processes. However, the roles of metal oxides in abiotic humification reactions under micro-aerobic remain ambiguous. The aim of this study was to use non-destructive measurement methods to investigate the role of MnO 2 in the evolution of humic substances (HSs) during oxidative polymerization of polyphenol-amino acid. Our results suggested a synergistic effect between MnO 2 and O 2 in promoting the polymerization reaction and identified that MnO 2 alone had a limited ability in accelerating the transformation of fulvic acid (FA) to humic acid (HA), whereas O 2 was the key factor in the process. Two-dimensional correlation spectroscopy (2D-COS) showed that the evolution in the UV-vis spectra followed the order of 475–525 nm>300–400 nm>240–280 nm in the humification process, indicating the formation of simple organic matter followed by FA and then HA. 13C nuclear magnetic resonance ( 13C NMR) analysis revealed that the products under both air and N 2 conditions in the presence of MnO 2 had greater amounts of aromatic-C than in the absence of MnO 2, demonstrating that MnO 2 affected the structure of the humification products. The results of this study provided new insights into the theory of abiotic humification. 相似文献
15.
• Forward osmosis (FO) coupled with chemical softening for CCI ROC minimization • Effective removal of scale precursor ions by lime-soda ash softening • Enhanced water recovery from 54% to 86% by mitigation of FO membrane scaling • High-purity CaCO3 was recovered from the softening sludge • Membrane cleaning efficiency of 88.5% was obtained by EDTA for softened ROC ![]() Reverse osmosis (RO) is frequently used for water reclamation from treated wastewater or desalination plants. The RO concentrate (ROC) produced from the coal chemical industry (CCI) generally contains refractory organic pollutants and extremely high-concentration inorganic salts with a dissolved solids content of more than 20 g/L contributed by inorganic ions, such as Na +, Ca 2+, Mg 2+, Cl −, and SO 42−. To address this issue, in this study, we focused on coupling forward osmosis (FO) with chemical softening (FO-CS) for the volume minimization of CCI ROC and the recovery of valuable resources in the form of CaCO 3. In the case of the real raw CCI ROC, softening treatment by lime-soda ash was shown to effectively remove Ca 2+/Ba 2+ (>98.5%) and Mg 2+/Sr 2+/Si (>80%), as well as significantly mitigate membrane scaling during FO. The softened ROC and raw ROC corresponded to a maximum water recovery of 86% and 54%, respectively. During cyclic FO tests (4 × 10 h), a 27% decline in the water flux was observed for raw ROC, whereas only 4% was observed for softened ROC. The cleaning efficiency using EDTA was also found to be considerably higher for softened ROC (88.5%) than that for raw ROC (49.0%). In addition, CaCO 3 (92.2% purity) was recovered from the softening sludge with an average yield of 5.6 kg/m 3 treated ROC. This study provides a proof-of-concept demonstration of the FO-CS coupling process for ROC volume minimization and valuable resources recovery, which makes the treatment of CCI ROC more efficient and more economical. 相似文献
16.
Complete CT degradation was achieved by SPC/Fe(II)/FA system.Formic acid established the reductive circumstance by producing CO2·–.CO2·– was the dominant active species responsible for CT degradation.CT degradation was favorable in the pH range from 3.0 to 9.0.SPC/Fe(II)/FA system may be suitable for CT remediation in contaminated groundwater. ![]() The performance of sodium percarbonate (SPC) activated with ferrous ion (Fe(II)) with the addition of formic acid (FA) to stimulate the degradation of carbon tetrachloride (CT) was investigated. Results showed that CT could be entirely reduced within 15 min in the system at a variety of SPC/Fe(II)/FA/CT molar ratios in experimental level. Scavenging tests indicated that carbon dioxide radical anion (CO2· –) was the dominant reactive oxygen species responsible for CT degradation. CT degradation rate, to a large extent, increased with increasing dosages of chemical agents and the optimal molar ratio of SPC/Fe(II)/FA/CT was set as 60/60/60/1. The initial concentration of CT can hardly affect the CT removal, while CT degradation was favorable in the pH range of 3.0–9.0, but apparently inhibited at pH 12. Cl – and HCO 3– of high concentration showed negative impact on CT removal. Cl – released from CT was detected and the results confirmed nearly complete mineralization of CT. CT degradation was proposed by reductive C-Cl bond splitting. This study demonstrated that SPC activated with Fe(II) with the addition of FA may be promising technique for CT remediation in contaminated groundwater. 相似文献
17.
• SMX was mainly degraded by hydrolysis, isoxazole oxidation and double-bond addition. • Isoxazole oxidation and bond addition products were formed by direct ozonation. • Hydroxylated products were produced by indirect oxidation. • NOM mainly affected the degradation of SMX by consuming •OH rather than O3. • Inhibitory effect of NOM on SMX removal was related to the components’ aromaticity. ![]() Sulfamethoxazole (SMX) is commonly detected in wastewater and cannot be completely decomposed during conventional treatment processes. Ozone (O 3) is often used in water treatment. This study explored the influence of natural organic matters (NOM) in secondary effluent of a sewage treatment plant on the ozonation pathways of SMX. The changes in NOM components during ozonation were also analyzed. SMX was primarily degraded by hydrolysis, isoxazole-ring opening, and double-bond addition, whereas hydroxylation was not the principal route given the low maximum abundances of the hydroxylated products, with m/z of 269 and 287. The hydroxylation process occurred mainly through indirect oxidation because the maximum abundances of the products reduced by about 70% after the radical quencher was added, whereas isoxazole-ring opening and double-bond addition processes mainly depended on direct oxidation, which was unaffected by the quencher. NOM mainly affected the degradation of micropollutants by consuming •OH rather than O 3 molecules, resulting in the 63%–85% decrease in indirect oxidation products. The NOM in the effluent were also degraded simultaneously during ozonation, and the components with larger aromaticity were more likely degraded through direct oxidation. The dependences of the three main components of NOM in the effluent on indirect oxidation followed the sequence: humic-like substances>fluvic-like substances>protein-like substances. This study reveals the ozonation mechanism of SMX in secondary effluent and provides a theoretical basis for the control of SMX and its degradation products in actual water treatment. 相似文献
18.
• 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
19.
• H. venusta TJPU05 showed excellent HN-AD ability at high salinity. • Successful expression of AMO, HAO, NAR and NIR confirmed the HN-AD ability of TJPU05. • H. venusta TJPU05 could tolerate high salt and high nitrogen environment. • H. venusta TJPU05 is a promising candidate for the bio-treatment of AW. A novel salt-tolerant heterotrophic nitrification and aerobic denitrification (HN-AD) bacterium was isolated and identified as Halomonas venusta TJPU05 ( H. venusta TJPU05). The nitrogen removal performance of H. venusta TJPU05 in simulated water (SW) with sole or mixed nitrogen sources and in actual wastewater (AW) with high concentration of salt and nitrogen was investigated. The results showed that 86.12% of NH 4+-N, 95.68% of NO 3–-N, 100% of NO 2–-N and 84.57% of total nitrogen (TN) could be removed from SW with sole nitrogen sources within 24 h at the utmost. H. venusta TJPU05 could maximally remove 84.06% of NH 4+-N, 92.33% of NO 3–-N, 92.9% of NO 2–-N and 77.73% of TN from SW with mixed nitrogen source when the salinity was above 8%. The application of H. venusta TJPU05 in treating AW with high salt and high ammonia nitrogen led to removal efficiencies of 50.96%, 47.28% and 43.19% for NH 4+-N, NO 3–-N and TN respectively without any optimization. Furthermore, the activities of nitrogen removal–related enzymes of the strain were also investigated. The successful detection of high level activities of ammonia oxygenase (AMO), hydroxylamine oxidase (HAO), nitrate reductase (NAR) and nitrite reductase (NIR) enzymes under high salinity condition further proved the HN-AD and salt-tolerance capacity of H. venusta TJPU05. These results demonstrated that the H. venusta TJPU05 has great potential in treating high-salinity nitrogenous wastewater. 相似文献
20.
• Cu0.15-ACF performs the best for H2S and PH3 simultaneous removal. • 550°C and 90°C are separately calcination and reaction temperatures. • The reason why Cu0.15/ACF shows better performance was found. • The accumulation of H2PO4− and SO42−(H2O)6 is the deactivation cause of Cu0.15/ACF. Poisonous gases, such as H 2S and PH 3, produced by industrial production harm humans and damage the environment. In this study, H 2S and PH 3 were simultaneously removed at low temperature by modified activated carbon fiber (ACF) catalysts. We have considered the active metal type, content, precursor, calcination, and reaction temperature. Experimental results exhibited that ACF could best perform by loading 15% Cu from nitrate. The optimized calcination temperature and reaction temperature separately were 550°C and 90°C. Under these conditions, the most removal capacity could reach 69.7 mg/g and 132.1 mg/g, respectively. Characterization results showed that moderate calcination temperature (550°C) is suitable for the formation of the copper element on the surface of ACF, lower or higher temperature will generate more cuprous oxide. Although both can exhibit catalytic activity, the role of the copper element is significantly greater. Due to the exceptional dispersibility of copper (oxide), the ACF can still maintain the advantages of larger specific surface area and pore volume after loading copper, which is the main reason for better performance of related catalysts. Finally, increasing the copper loading amount can significantly increase the crystallinity and particle size of copper (oxide) on the ACF, thereby improving its catalytic performance. In situ IR found that the reason for the deactivation of the catalyst should be the accumulation of generated H 2PO 4− and SO 42−(H 2O) 6 which could poison the catalyst. 相似文献
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