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1.
Understanding the trends in PM 2.5 levels is essential for formulating clean air plans. This paper analyzes PM 2.5 data from various published sources for the years 2000 to 2010 in the Pearl River Delta Economic Zone (PRDEZ). The long-term variation in PM 2.5 mass concentration is analyzed. Results show that PM 2.5, organic carbon (OC), elemental carbon (EC), and SO42− show a similar trend, increasing before 2005 and then decreasing slightly. The annual average PM 2.5 concentration ranges from 49.1 μg·m −3 in 2000 to 64.3 μg·m −3 in 2010, with a peak of 84.1 μg·m −3 in 2004. None of these 11 years meets the new National Ambient Air Quality standard (NAAQS) for PM 2.5 (35 μg·m −3). Overall average concentrations of OC, EC, and SO42− are 13.0, 6.5, and 11.8 μg·m −3, respectively. NO3− and NH4+ respectively have concentrations of 1.5 μg·m −3 and 2.9 μg·m −3 in 2000 and 6.4 μg·m −3 and 5.3 μg·m −3 in 2010, with a statistically significant average annual trend of+ 0.2 μg·m −3·yr −1 and+ 0.1 μg·m −3·yr −1. In certain geographic regions, OC and EC contribute most of the PM 2.5, while in other regions secondary water-soluble ions are more important. In general, OC and SO42− are the dominant components of PM 2.5, contributing 20.6% and 18.6%, respectively. These results provide, for the first time, a better understanding of the long-term PM 2.5 characteristics and trends, on a species-by-species basis, in the PRDEZ. The results indicate that PM 2.5 abatement needs to prioritize secondary species. 相似文献
2.
Volatile organic compounds (VOCs) and carbonyl compounds were measured both indoors and outdoors in 50 residences of Beijing in heating (December, 2011) and non-heating seasons (April/May, 2012). SUMMA canisters for VOCs and diffusive samplers for carbonyl compounds were deployed for 24 h at each site, and 94 compounds were quantified. Formaldehyde, acetone and acetaldehyde were the most abundant carbonyl compounds both indoors and outdoors with indoor median concentrations being 32.1, 21.7 and 15.3 μg·m −3, respectively. Ethane (17.6 μg·m −3), toluene (14.4 μg·m −3), propane (11.2 μg·m −3), ethene (8.40 μg·m −3), n-butane (6.87 μg·m −3), and benzene (5.95 μg·m −3) showed the high median concentrations in indoor air. Dichloromethane, p-dichlorobenzene (p-DCB) and toluene exhibited extremely high levels in some residences, which were related with a number of indoor emission sources. Moreover, isoprene, p-dichlorobenzene and carbonyls showed median indoor/outdoor (I/O) ratios larger than 3, indicating their indoor sources were prevailing. Chlorinated compounds like CFCs were mainly from outdoor sources for their I/O ratios being less than 1. In addition, indoor concentrations between two sampling seasons varied with different compounds. Carbonyl compounds and some chlorinated compounds had higher concentrations in the non-heating season, while alkanes, alkenes, aromatic compounds showed an increase in the heating season. Indoor concentration of VOCs and carbonyls were influenced by locations, interior decorations and indoor activities, however the specific sources for indoor VOCs and carbonyls could not be easily identified. The findings obtained in this study would significantly enhance our understandings on the prevalent and abundant species of VOCs as well as their concentrations and sources in Beijing residences. 相似文献
3.
• 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
4.
Slightly acidic solutions are a practical means of removing ammonia from air
Scrubbed NH 3 accumulates in solution as NH 4+ and should be an excellent fertilizer
Increased air velocity decreased NH 3 removal and increased NH 4+ collection
Previous research on wet scrubbers has only studied highly acidic scrubbing solutions because of their high ammonia capture efficiencies; however, the high acidity created practical problems. Lower acidity solutions would reduce corrosion, maintenance, and cost; however, designers may need to use strategies for increasing scrubber effectiveness, such as using lower air velocities. The objective of this study was to determine if a spray scrubber with slightly acidic and higher pH scrubbing solution (pH from 2 to 8) could effectively remove NH 3 from NH 3 laden air (such as animal building exhaust air), and also collect this valuable resource for later use as a fertilizer. A bench-scale spray wet scrubber treated 20 ppmv NH 3/air mixture in a countercurrent contact chamber. First, the solution pH was varied from 2 to 8 while maintaining constant air velocity at 1.3 m·s −1. Next, air velocity was increased (2 and 3 m·s −1) while solution pH remained constant at pH6. At 1.3 m·s −1, NH 3 removal efficiencies ranged between 49.0% (pH8) and 84.3% (pH2). This study has shown that slightly acidic scrubbing solutions are a practical means of removing ammonia from air especially if the scrubber is designed to increase collisions between solution droplets and NH 3 molecules. The NH 3 removed from the air was held in solution as NH 4+ and accumulates over time so the solution should be an excellent fertilizer. 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.
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
7.
Selective catalytic reduction (SCR) of NO x with NH 3 is an effective technique to remove NO x from stationary sources, such as coal-fired power plant and industrial boilers. Some of elements in the fly ash deactivate the catalyst due to strong chemisorptions on the active sites. The poisons may act by simply blocking active sites or alter the adsorption behaviors of reactants and products by an electronic interaction. This review is mainly focused on the chemical poisoning on V 2O 5-based catalysts, environmental-benign catalysts and low temperature catalysts. Several common poisons including alkali/alkaline earth metals, SO 2 and heavy metals etc. are referred and their poisoning mechanisms on catalysts are discussed. The regeneration methods of poisoned catalysts and the development of poison-resistance catalysts are also compared and analyzed. Finally, future research directions in developing poisoning resistance catalysts and facile efficient regeneration methods for SCR catalysts are proposed. 相似文献
8.
The aim of this study was to identify the intermediates in clofibric acid degradation under various advanced oxidation processes, namely ultraviolet (UV), UV/H 2O 2, vacuum ultraviolet (VUV), VUV/H 2O 2, and solar/TiO 2 processes, as well as to assess the toxicity of these intermediates. Eleven intermediates have been detected by gas chromatography-mass spectrometer, most of which were reported for the first time to our best knowledge. Combining the evolution of the dissolved organic carbon, Cl - and specific ultraviolet absorption at 254 nm, it could be deduced that cleavage of aromatic ring followed by dechlorination was the mechanism in solar/TiO 2 process, while dechlorination happened first and accumulation of aromatic intermediates occurred in the other processes. Different transformation pathways were proposed for UV-, VUV-assisted and solar/TiO 2 processes, respectively. The acute toxicity was evaluated by means of Photobacterium phosphoreum T 3 spp. bioassay. It was believed that aromatic intermediates increased the toxicity and the ring-opening pathway in solar/TiO 2 process could relieve the toxicity. 相似文献
9.
• 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
10.
•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
11.
• A new pulsed switching peroxi-coagulation (PSPC) system was developed. • The ECT for 2,4-D removal in the PSPC was lower than that in the EF. • The iron consumption for 2,4-D removal in the PSPC was lower than that in the PC. ![]() The aim of this study was to develop a new pulsed switching peroxi-coagulation system to control hydroxyl radical (?OH) production and to enhance 2,4-Dichlorophenoxyacetic acid (2,4-D) degradation. The system was constructed with a sacrifice iron anode, a Pt anode, and a gas diffusion cathode. Production of H 2O 2 and Fe 2+ was controlled separately by time delayers with different pulsed switching frequencies. Under current densities of 5.0 mA/cm 2 (H 2O 2) and 0.5 mA/cm 2 (Fe 2+), the ?OH production was optimized with the pulsed switching frequency of 1.0 s (H 2O 2):0.3 s (Fe 2+) and the ratio of H 2O 2 to Fe 2+ molar concentrations of 6.6. Under the optimal condition, 2,4-D with an initial concentration of 500 mg/L was completely removed in the system within 240 min. The energy consumption for the 2,4-D removal in the system was much lower than that in the electro-Fenton process (68±6 vs. 136±10 kWh/kg TOC). The iron consumption in the system was ~20 times as low as that in the peroxi-coagulation process (196±20 vs. 3940±400 mg/L) within 240 min. The system should be a promising peroxi-coagulation method for organic pollutants removal in wastewater. 相似文献
12.
• 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
13.
? The Cu–Ni/γ-Al 2O 3 catalyst was prepared to study HCN hydrolysis
? On catalyst calcined at 400°C, the HCN removal efficiency reaches a maximum.
? HCN removal is the highest at 480 min at a H 2 O/HCN volume ratio of 150
? The presence of CO facilitates HCN hydrolysis and increases NH 3 production.
? O 2 increases the HCN removal and NO x production but decreases NH 3 production
GRAPHIC ABSTRACT
To decompose efficiently hydrogen cyanide (HCN) in exhaust gas, g-Al 2O 3-supported bimetallic-based Cu–Ni catalyst was prepared by incipient-wetness impregnation method. The effects of the calcination temperature, H 2O/HCN volume ratio, reaction temperature, and the presence of CO or O 2 on the HCN removal efficiency on the Cu–Ni/g-Al 2O 3 catalyst were investigated. To examine further the efficiency of HCN hydrolysis, degradation products were analyzed. The results indicate that the HCN removal efficiency increases and then decreases with increasing calcination temperature and H 2O/HCN volume ratio. On catalyst calcined at 400°C, the efficiency reaches a maximum close to 99% at 480 min at a H 2O/HCN volume ratio of 150. The HCN removal efficiency increases with increasing reaction temperature within the range of 100°C–500°C and reaches a maximum at 500°C. This trend may be attributed to the endothermicity of HCN hydrolysis; increasing the temperature favors HCN hydrolysis. However, the removal efficiencies increases very few at 500°C compared with that at 400°C. To conserve energy in industrial operations, 400°C is deemed as the optimal reaction temperature. The presence of CO facilitates HCN hydrolysis andincreases NH 3 production. O 2 substantially increases the HCN removal efficiency and NO x production but decreases NH 3 production. 相似文献
14.
• 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
15.
• 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
16.
• 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
17.
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
18.
• PANI/Ti(OH)n(4–n)+ exhibited excellent adsorption capacity and reusability. • Adsorption sites of Cr(VI) were hydroxyl, amino/imino group and benzene rings. • Sb(V) was adsorbed mainly through hydrogen bonds and Ti-O-Sb. • The formation of Cr-O-Sb in dual system demonstrated the synergistic adsorption. • PANI/TiO2 was a potential widely-applied adsorbent and worth further exploring. Removal of chromium (Cr) and antimony (Sb) from aquatic environments is crucial due to their bioaccumulation, high mobility and strong toxicity. In this work, a composite adsorbent consisting of Ti(OH) n(4–n)+ and polyaniline (PANI) was designed and successfully synthesized by a simple and eco-friendly method for the uptake of Cr(VI) and Sb(V). The synthetic PANI/TiO 2 composites exhibited excellent adsorption capacities for Cr(VI) and Sb(V) (394.43 mg/g for Cr(VI) and 48.54 mg/g for Sb(V)), wide pH applicability and remarkable reusability. The adsorption of Cr(VI) oxyanions mainly involved electrostatic attraction, hydrogen bonding and anion-π interactions. Based on X-ray photoelectron spectroscopy and FT-IR analysis, the adsorption sites were shown to be hydroxyl groups, amino/imino groups and benzene rings. Sb(V) was adsorbed mainly through hydrogen bonds and surface complexation to form Ti-O-Sb complexes. The formation of Cr-O-Sb in the dual system demonstrated the synergistic adsorption of Cr(VI) and Sb(V). More importantly, because of the different adsorption sites, the adsorption of Cr(VI) and Sb(V) occurred independently and was enhanced to some extent in the dual system. The results suggested that PANI/TiO 2 is a promising prospect for practical wastewater treatment in the removal of Cr(VI) and Sb(V) from wastewater owing to its availability, wide applicability and great reusability. 相似文献
19.
• 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
20.
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
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