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Nitrate Removal via Formate Radical-induced Photochemical Process
摘要： Removal of excess nitrate is critical to balance the nitrogen cycle in aquatic systems. This study investigated a novel denitrification process by tailoring photochemistry of nitrate with formate. Under UV light irradiation, short-lived radicals (i.e., HO·, NO2· and CO3·-) generated from nitrate photolysis partially oxidized formate to highly reductive formate radical (CO2·-). CO2·- further reduced nitrogen intermediates generated during photochemical denitrification (mainly NO·, HNO, and N2O) to gas-phase nitrogen (i.e., N2O and N2). The degradation kinetics of total dissolved nitrogen was mainly controlled by the photolysis rates of nitrate and nitrite. The distribution of final products was controlled by the reaction between CO2·- and N2O. To achieve a simultaneous and complete removal of dissolved nitrogen (i.e., nitrate, nitrite, and ammonia) and organic carbon, the formate-to-nitrate stoichiometry was determined as 3.1 ± 0.2 at neutral pH in deionized water. Solution pH impacted the removal rates of nitrate and nitrite, but not that of total dissolved nitrogen or formate. The presence of dissolved organic matter at levels similar to groundwater had a negligible impact on the photochemical denitrification process. A high denitrification efficiency was also achieved in a synthetic groundwater matrix. Outcome from this study provides a potential denitrification technology for decentralized water treatment and reuse facilities to abate nitrate in local water resources.
关键词： denitrification,water treatment,nitrate removal,photochemical process,formate radical
更新于2025-09-10 09:29:36
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Synthesis and characterization of CuZnO@GO nanocomposites and their enhanced antibacterial activity with visible light
摘要： Copper and zinc composite oxide (CuZnO) was synthesized successfully via a sol–gel method and modi?ed by silane coupling agent to prepare CuZnO@graphene oxide (CuZnO@GO) nanocomposites, with CuZnO nanoparticles (NPs) distributed on the GO nanosheets. The structural properties of prepared CuZnO@GO nanocomposites were studied by FT-IR and XRD techniques. SEM and TEM analysis showed the spherical morphology of CuZnO NPs with a diameter of 20–40 nm. The optical properties of synthesized products were estimated through UV–Vis DRS and PL spectroscopy, which suggested that CuZnO@GO nanocomposites had a widened absorption range from UV to visible region and a lower photogenerated carrier recombination rate than that of pure CuZnO NPs. The antibacterial mechanism of CuZnO@GO nanocomposites was investigated using gram-negative bacteria Escherichia coli and gram-positive bacteria Staphylococcus aureus as two model microorganisms. The antibacterial properties of CuZnO@GO nanocomposites on mixed bacteria were researched in the cooling water system. The results showed that when adding CuZnO@GO nanocomposites to E. coli or S. aureus suspension, the protein leakage after 20 h was 10.5 times or 8.3 times higher than that in the blank experiment. Furthermore, the antibacterial activity of CuZnO@GO nanocomposites in presence of visible light was found to be signi?cantly enhanced as compared with control. Under visible light irradiation, the antibacterial rate of CuZnO@GO nanocomposites in circulating cooling water reached 99.09% when the mass fraction of GO was 17.5%, and more than 90% of bacteria were inactivated by 100 mg L?1 CuZnO@GO nanocomposites in 60 min after four recycled runs.
关键词： Water treatment,CuZnO@GO nanocomposites,Visible light,Photocatalytic antibacterial activity,Antibacterial mechanism
更新于2025-09-10 09:29:36
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Central Composite Design (CCD) Optimized Synthesis of Fe3O4@SiO2@AgCl/Ag/Ag2S as a Novel Magnetic Nano-Photocatalyst for Catalytic Degradation of Organic Pollutants
摘要： In this study, we formulated and synthesized an efficient visible light-active magnetic nano-photocatalyst, Fe3O4@SiO2@AgCl/Ag/Ag2S, to decompose methyl orange (MO) as a model organic pollutant. XRD, SEM, TEM, EDS, DRS, and VSM analyses were used to characterize the developed magnetic nano-photocatalyst. Moreover, central composite design (CCD) modeling, which is based on response surface methodology (RSM) modeling, is utilized to optimize the synthetic and operating conditions to maximize the photocataytic performance. The CCD-optimized values for molar ratio of AgCl to Fe3O4, molar ratio of Ag2S to Fe3O4, and the photocatalyst dosage are found to be 0.8, 0.27, and 1.27 g/L, respectively. The developed Fe3O4@SiO2@AgCl/Ag/Ag2S nano-photocatalyst shows a superior photocatalytic activity in decomposition of MO, degrading around 90% and 99% of MO in 30 min and one hour, respectively, under visible light illumination, at which the predicted values are in a good agreement with the experimental values (R2=0.971 and Adj-R2=0.945). Meanwhile, the morphological, physicochemical, and magnetic properties of the developed nano-photocatalyst are largely retained over ten successive cycles of photocatalytic reactions, and no significant decline in the photocatalytic activity is observed.
关键词： Magnetic Nano-Photocatalyst,Central Composite Design (CCD),Organic Pollutant,AgCl/Ag/Ag2S,Water Treatment
更新于2025-09-10 09:29:36
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Visible photodegradation of ibuprofen and 2,4-D in simulated waste water using sustainable metal free-hybrids based on carbon nitride and biochar
摘要： Rational designing of metal-free carbon nitride based photocatalysts can lead to an excellent optical response and a higher photocatalytic activity driven by visible and solar light. This combines green photocatalytic technology with greener materials prepared by facile approaches for environmental remediation. Herein we report utilization of star photocatalyst g-C3N4 (CN) to form highly efficient hetero-assemblies along with acidified g-C3N4 (ACN), polyaniline (PANI), reduced graphene oxide (RGO) and biochar. By use of these organic semiconductors we synthesize g-C3N4/ACN/RGO@Biochar (GARB), g-C3N4/PANI/RGO@Biochar (GPRB) and ACN/PANI/RGO@Biochar (APRB) nano-assemblies with different optical response and band edge positions for a better charge flow and reduced recombination of carriers. These synthesized catalysts were used for visible light powered degradation of 2,4-Dichlorophenoxy acetic acid (2,4-D) and ibuprofen (IBN). APRB performs the best and degrades 99.7% and 98.4% of 2,4-D and IBN (20 mg L?1) under Xe lamp exposure in 50 min and retention of high activity in natural sunlight. Optical analysis, photoelectrochemical response and radical quenching studies show both hydroxyl and superoxide radical anions as major reactive species and a Z-scheme photocatalytic mechanism. RGO acts as an electron mediator and protects higher positioned bands of PANI and ACN in APRB for a remarkable photocatalytic activity for a metal free material. The degradation pathway was analyzed by LC-MS analysis and 42% and 40% total organic carbon was removed in 2 h for 2,4-D and IBN degradation respectively. The toxicity of degraded products was analyzed by analyzing viability of human peripheral blood cells with retaining of 99.1% cells.
关键词： Water treatment,Carbon nitride,Nano-assemblies,Environmental detoxification,Biochar: pharmaceutical effluents,Photocatalysis
更新于2025-09-10 09:29:36
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Alveolar TiO2-β-SiC photocatalytic composite foams with tunable properties for water treatment
摘要： New alveolar TiO2-β-SiC photocatalytic composite foams gathering within a ready-to-use media, the TiO2 active phase and the β-SiC alveolar foam structure have been prepared through a Shape Memory Synthesis (SMS) replica method. They have been obtained by incorporating TiO2 powders inside the infiltration slurry used for transforming the pre-shaped polyurethane foam into its corresponding carbide. The photocatalytic composite foams contained 16 wt. % and 24 wt. % of TiO2, most of them being available for the reaction by being located in the external layer of the foam rather than dispersed within the foam matrix, so that no further post-synthesis immobilization process was needed for coating the foam with TiO2 active phase. The adsorption behaviour of the TiO2-β-SiC composite foams towards the Diuron pollutant in water was tuned by applying a final calcination treatment to the as-synthesized foams within the 400-700 °C range, that allowed to tune the amount of residual unreacted carbon within the foams, while allowing the formation of small TiO2 crystallites via the selective oxidation of TiC carbide, and thanks to the β-SiC resistance to oxidation. The TiO2-β-SiC composite foams calcined at 700 °C outperformed a reference β-SiC supported foam TiO2 catalyst in terms of diuron degradation, while the reference foam remained more efficient in terms of mineralization rate.
关键词： water treatment,photocatalysis,Shape Memory Synthesis replica method,adsorption properties,TiO2-β-SiC composite foam
更新于2025-09-10 09:29:36
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Decorating (001) Dominant Anatase TiO2 Nanoflakes Array with Uniform WO3 Clusters for Enhanced Photoelectrochemical Water Decontamination
摘要： A facile two-step chemical bath deposition (CBD) method has been developed for the preparation of uniformly crystalline anatase WO3/TiO2 array on FTO substrate. The synthesis starts from the hydrothermal growth of TiO2 array in a homogenous HCl aqueous solution containing stabilized titanium isopropoxide, NH4F and acetylacetone (AcAc). Electron microscopy and the XRD analysis suggest the addition of AcAc chelating agent can facilitate the preferential growth of anatase (001) facets that are interconnected and vertically aligned. While (101) dominant TiO2 bipyramid array may form without AcAc. The subsequent decoration of WO3 clusters on TiO2 array is achieved by post-depositing TiO2 array in (NH4)2WO4 aqueous solution followed with a calcination at 450 oC, the resultant WO3/TiO2 array shows a significantly elevated photocurrent performances owing to the high separation efficiency of charge carriers. The enhanced photoelectrocatalytic properties are explained by the efficient charge carrier separation at the heterojunction between WO3 and TiO2. A faster photoelectrochemical degradation of methylene under simulated sunlight further demonstrates the potential usefulness of WO3/TiO2 arrayed photoelectrocatalyst in solar-driven environmental purification and solar fuel synthesis.
关键词： hydrothermal process,WO3,water treatment,TiO2,semiconductor photoelectrocatalysis
更新于2025-09-10 09:29:36
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Photoelectrocatalytic decolorization of azo dyes with nano-composite oxide layers of ZnO nanorods decorated with Ag nanoparticles.
摘要： Photoelectrocatalysis provides an excellent frame for the application of photocatalytic nanostructured materials on easy recoverable supports. This study reports the two-step synthesis of hierarchically nanostructured ZnO/Ag composite photoelectrodes. Wutzite ZnO was selectively electronucleated as spheroidal seeds on fluor doped tin oxide substrates and nanodecorated with Ag nanoclusters under electrochemical control. Hirearchically organized nanorods were selectively chemically grown on the plane (002) perpendicular to the substrate from ZnO/Ag seeds. Solutions emulating dye effluents with the usual contents of 0.1 M of NaCl and a model azo dye (Methyl Orange) were decolorized using ZnO/Ag nanorods in different treatments. Photocatalysis attained discrete decolorizations of 8% whereas photoelectrocatalysis completely decolorized solutions after 60 min. The influence of the metal/semiconductor interface (ZnO/Ag) as introduced Schottky barrier is studied demonstrating a four-fold enhancement on decolorization kinetics respect bare ZnO nanorods. The influence of the seed growth control on the final photoelectrocatalytic response is reported to control the hierarchical organization of nanorods. This resulted in different decolorization kinetics as result of the differences on the efficient use of the delivered photons conditioned by the photoelectrode structure.
关键词： photocatalysis,photocathode,nano-coating,electrochemical water treatment,Metallic/semiconductor composite photocatalysts
更新于2025-09-10 09:29:36
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Modification of kaolinite from Pará/Brazil region applied in the anionic dye photocatalytic discoloration
摘要： The incorporation of titanium oxide and other transition metals on the surface of different materials has been shown to be a promising strategy to improve the efficiency of photocatalytic processes aiming at the decontamination of aqueous systems caused by persistent organic contaminants such as dyes. The objective of this work was to evaluate the catalytic properties of nanocomposites based on the kaolinite (Kaol) with TiO2 incorporated, obtained from the sol-gel method, used in discoloration of the coomasie brilliant blue dye (CBB) in aqueous solution. The nanocomposites were prepared from the reaction of titanium tetraisopropoxide with purified natural kaolinite and calcined at different temperatures. The samples were characterized by the XRD, FTIR, SEM-XED, BET-BJH and diffuse reflectance spectroscopy techniques, which demonstrated the structure, crystalline pattern, as well as the incorporation of titanium in the clay structure, changes caused by modification in morphology, texture and energy gap. The photocatalytic tests were performed using 5 × 10?5 mol L?1, 1.0 and 1.5 g L?1 concentration, respectively, to the CBB dye solution and to the synthesized materials. Among the nanocomposites, the sample calcined at 300 °C, KaolBT-300, presented the best photocatalytic performance. The addition of the H2O2 oxidant to the solution containing KaolBT-300 at the concentration of 1.5 g L?1 increased the discoloration percentage to 97.31% of the CBB solution dye after 120 min of irradiation. The discoloration kinetics of the CBB dye obeys the pseudo-first-order velocity law. Finally, the reuse of the KaolBT-300 sample in three consecutive cycles of photocatalysis demonstrated a significant adhesion stability of the TiO2 particles on the clay surface, indicating that it can be used in advanced oxidative processes for the degradation of organic pollutants.
关键词： Natural clay,Sol-gel synthesis,Heterogeneous catalysis,Titanium oxide,Water treatment,Dye
更新于2025-09-10 09:29:36
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Environmental impact analysis applied to solar pasteurization systems
摘要： In many under-developed regions of the world, most people live in rural villages, where the electrical grid is often not available and traditional potabilization systems would be too expensive and technologically too complex to be implemented. Thus every year, millions of people in the world die due to diseases related to water contamination. Solar Pasteurization Systems represents a promising alternative to address such problems, as they can thermally disinfect water employing solar energy alone, without using fossil fuels or electrical grid connection. Evaluating the cradle-to-grave environmental footprint of Solar Pasteurization Systems, and in general of technologies aimed at producing safe drinking water, represents an issue of major importance. This is relevant because an effective solution has to be, at the same time, environmentally and locally sustainable for a given geographical context. In this work, a complete Life Cycle Assessment and Exergo-environmental analysis are performed in order to calculate and compare the eco-profiles of two Solar Pasteurization technologies: a Natural Circulation and a Thermostatic Valve System. Results show that Natural Circulations Systems are generally more environmentally sustainable (0.30 mPt/l) than the Thermostatic Valve System (0.83 mPt/l) thanks to the higher productivity of treated water. A sensitivity analysis is performed to investigate the dependency of the model systems from different operational and environmental conditions, at different installation sites, i.e. Somalia, Brazil and Italy. The main difference is represented by the productivity of the systems. In all cases the solar collector array is the main item responsible for environmental burdens, impacting for almost 45% of the total score. The analysis also shows that the use of solar energy in Pasteurization is important to avoid direct emissions and to lower the global environmental impact connected with thermal energy production compared to the eco-profiles of other widely diffused pasteurization technologies based on the combustion of fossil fuels or biomass that can be used to provide the same function (in general higher than 1.2 mPt/l). Moreover, with the aim of qualitatively assessing the benefit associated with the potential implementation of solar pasteurization systems, an improvement of the sanitary conditions is envisioned, especially in under-developed countries where, definitively, a large scale diffusion would be recommended.
关键词： Solar Pasteurization,Solar Energy,Life Cycle Assessment,Exergo-environmental analysis,Water Disinfection,Water Treatment
更新于2025-09-09 09:28:46
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One-Pot Synthesis of Magnesium Aminoclay–Iron Oxide Nanocomposites for Improved Photo-Fenton Catalytic Performance
摘要： Fe3O4 nanoparticles (NPs) have been widely used in photo-Fenton catalysis applications for water/waste water treatment. Their drawbacks, however, continue to limit their potential. In the present study, we synthesized magnesium aminoclay–iron oxide [MgAC–Fe3O4] nanocomposites in DI water solution by treated them under 4% H2/Ar for 3 hours in a 500 (cid:3)C furnace. Obtained X-ray diffraction (XRD) patterns con?rmed that the growth of the Fe3O4 NPs in the amorphous MgAC; also, scanning electron microscopy (SEM) images indicated that the MgAC–Fe3O4 nanocomposites were in an aggregated form of 170 ± 117 nm average-diameter. MgAC[0.7 g]–Fe3O4 nanocomposite exhibited the best photo-Fenton catalysis with methylene blue (MB) was completely removed from the treatment solution at a constant rate of 0.0083 (min?1(cid:2) on the batch scale. This performance was 13.83 times better than that of commercial Fe3O4. On the pilot scale (100 L), MgAC[0.7 g]–Fe3O4 nanocomposite took 12 hours to completely removed MB from tap water. The mechanism of the high photo-Fenton catalysis was attributed to the higher rate adsorption of MgAC as well as Brunauer-Emmett-Teller (BET) surface area.
关键词： Catalysis,Water/Waste Water Treatment,Fe3O4,Photo-Fenton,Aminoclay,Nanocomposite
更新于2025-09-09 09:28:46