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TiO2-SiO2 thin films were created on Corning glass substrates using a simple method. Nine layers of SiO2 were deposited; later, several layers of TiO2 were deposited, and their influence was studied. Raman spectroscopy, high resolution transmission electron spectroscopy (HRTEM), an X-ray diffractometer (XRD), ultraviolet-visible spectroscopy (UV-Vis), a scanning electron microscope (SEM), and atomic force microscopy (AFM) were used to describe the sample's shape, size, composition, and optical characteristics. Photocatalysis was realized through an experiment involving the deterioration of methylene blue (MB) solution exposed to UV-Vis radiation. With the increase of TiO2 layers, the photocatalytic activity (PA) of the thin films showed an increasing trend, and the maximum degradation efficiency of MB by TiO2-SiO2 was 98%, which was significantly higher than that obtained by SiO2 thin films. It was found that an anatase structure was formed at a calcination temperature of 550 °C; phases of brookite or rutile were not observed. Each nanoparticle's size was 13–18 nm. Due to photo-excitation occurring in both the SiO2 and the TiO2, deep UV light (λ = 232 nm) had to be used as a light source to increase photocatalytic activity. [ABSTRACT FROM AUTHOR]

• Three metal–organic frameworks of Copper and Cerium prepared via solvothermal method. • Copper and Cerium frameworks gave 289 and 375 mmol/hour.gram of hydrogen, respectively. • Copper-doped Cerium framework yielded 465 mlmol/hour.gram of hydrogen. • This structure showed the most effective charge separation during photo-activity. • Copper-doped Cerium framework maintained stable hydrogen output over ten reuse cycles. Increased dependence on fossil fuels as energy sources strongly contributes in both global warming and environmental pollution, leading to serious impacts on human-beings and societies. Therefore, shift from hydrocarbon-based energy to alternative green, sustainable and renewable sources of energy has been globally stimulated in past decades. In an agreement with this context, hydrogen is counted as one of these sources which has been paid strong attention recently due to its high energy content and no harmful emissions. Consequently, this study introduces production of clean green hydrogen through the process of photocatalytic water splitting which is a cost-effective route and releases zero emissions. A series of copper/ or cerium based metal–organic frameworks were successfully prepared via one-pot solvothermal technique and were presented as three novel photocatalysts for hydrogen production from water. The photocatalytic performances of these structures were investigated under visible light irradiation, revealing the highest activity for copper doped cerium metal–organic framework. It exhibited a maximum pure hydrogen productivity of 465 mmol per hour/ gram which was much higher than those the detected productivity by copper and cerium metal–organic frameworks (289 and 375 mmol per hour/ gram respectively). Heterojunction between the two central metals as well as effective charge separation in copper doped cerium metal–organic framework are reasons of its superiority in hydrogen evolution exploit, compared to the other two structures. The recyclability of copper doped cerium metal–organic framework demonstrated high reliability since it showed nearly stable yields of hydrogen over ten cycles of photocatalytic reuse. Therefore, the presented binary metals organic framework establishes new platform for photocatalysts in process of hydrogen production through water splitting. [ABSTRACT FROM AUTHOR]

Background & Objective: Antibiotics are considered among the pollutants in water environments with stable effects. This study aimed to investigate the efficiency of photocatalytic process using core–shell TiO2 under ultraviolet radiation for the removal of Cefixime antibiotic from aqueous solutions. Materials and methods: This study was conducted in an experimental-laboratory scale. The effect of factors such as pH (5, 6, 7, 8 and 9), initial concentrations of Cefixime (2-10 mg/L) and concentrations of catalyst (0.5-5 g/L) was surveyed. Sample volume for every step of the experiments was 1000 ml. A batch stainless steel 3L photo catalytic reactor was designed. The synthesized catalyst was characterized by SEM ، XRD and VSM Methods. Results: Physical characteristics of the Fe3O4/SiO2/TiO2 revealed that the catalyst particles had the average size of 10 nm. The photocatalytic degradation of Cefixime with UV+ Fe3O4/SiO2/TiO2 in the optimal condition was 100% (pH =6, retention time= 25 min, Cefixime concenteration= 2 mg/L catalyst dosage= 4 g/L). Synthetic models showed that the process of photocatalytic removal of Cefixime followed the first-order model. Conclusion: The results of this study suggested that UV+ Fe3O4/SiO2/TiO2 process is very effective method for the complete removal of Cefixime antibiotic from aqueous solutions.

Highly efficient catalytic technologies are urgently needed to remove pharmaceutical pollutants from water. In this work, the preparation, characterization, and photocatalytic performance of an earth‐abundant Ni‐based heterogeneous catalyst featuring highly dispersed Ni species over nanosheets of carbon nitride are reported. The absence of any metallic nickel phase has been confirmed by spectrometric analyses, unveiling the NiN environment for the metal centers and attaining synergistic interfacial carrier transfer via NNiN coordination. By combining advanced characterizations with kinetic investigations, it is demonstrated that these newly formed isolated single atoms of Ni act as a bridge, facilitating faster electron transfer, increasing the charge density on Ni, and reducing the photocarrier transfer barrier. Compared to literature precedents, this substantially enhances the degradation of gemfibrozil, a model pharmaceutical pollutant found in wastewater, reducing the formation of toxic benzenic byproducts during photooxidation. This effect, which is not observed over conventional nanoparticle‐based materials, discriminates the role of single‐atom and nanoparticle‐based catalysis during degradation of pollutants. This work opens new avenues in designing selective and earth‐abundant photocatalysts for advanced oxidation processes, showing the importance of atom coordination to control the surface and catalytic properties of single‐atom materials. [ABSTRACT FROM AUTHOR]

The metformin, is an emerging contaminant and one of the most consumed drugs in the world that has a high power of endocrine disruption across species in the ecosystem. The focus of this study was to determine the best photocatalytic processes through the study of TiO2‐based photocatalytic, photo–Fenton and photo–ferrioxalate reactions for the metformin removal. The experimental results demonstrated that a high removal of metformin is obtained using TiO2‐based photocatalytic (97 %), followed by photo–Fenton (66%) and photo–ferrioxalate (41%). The zero‐order rate constant (k) for TiO2‐based photocatalytic, photo–Fenton and photo–ferrioxalate reaction was 2.36, 1.95 and 1.92 mg/L.min, respectively. The metformin was transformed into NH4+‐N, NO2−‐N and NO3−‐N. According to results obtained, the proposed Box–Behnken experimental design can be used in photocatalytic processes to obtain the optimum conditions of the significant variables (H2O2 concentration, catalytic concentration, pH and reaction time) for removal of metformin in a few runs. [ABSTRACT FROM AUTHOR]

ZnO/Fe2O3/Clinoptilolite photocatalyst was synthesized through sol–gel method. The photocatalyst was characterized by XRD, XRF, EDX, FE-SEM, FT-IR, BET and UV–VIS DRS analyses. According to the XRD, FT-IR, and EDX results, the presence of ZnO and Fe2O3 was confirmed on the clinoptilolite surface. Based on the XRF results, the molar ratio of Fe3+/ZnO in the photocatalyst was obtained as 0.06. The FE-SEM results confirmed stabilization of ZnO/Fe2O3 on the clinoptilolite surface. Based on the BET results, the surface area and pore volume for the photocatalyst were obtained as 291.35 m2/g and 0.23 cm3/g, respectively. According to the UV–VIS DRS results, the band gap energy of the photocatalyst was measured as 3.38 eV. The performance of the synthesized photocatalyst in degrading metronidazole from contaminated water, as one of the most widely used antibiotics in pharmaceutical industries, was evaluated by response surface methodology. Operational factors including pH (4–10), metronidazole concentration (1–100 mg/l), irradiation time (45–180 min), photocatalyst concentration (0.5–2 g/l), and H2O2 concentration (25–100 mg/l) were investigated. The optimal values of the factors in degrading 99% of the contaminant were as follows: irradiation time = 90 min, photocatalyst concentration = 1 g/l, pH = 10, H2O2 concentration = 40 mg/l, and MNZ concentration = 60 mg/l. [ABSTRACT FROM AUTHOR]

The photoreforming of glucose has been studied over TiO 2 photocatalyst with different photoreactors, focusing on the effect of the reaction conditions: temperature, pressure, catalyst and substrate concentration. The effect of pressure was particularly significant, decreasing hydrogen evolution rate, but improving the conversion of the substrate. Furthermore, pressure moderately higher than ambient allowed to operate at high temperature (80 °C), boosting hydrogen productivity. Most experiments were carried out on glucose photoreforming, but, for the first time, the photoconversion of levulinic acid was investigated, as an interesting product of biomass hydrolysis under harsh conditions. Levulinic acid led to the production of ethane and ethylene in gas phase, interpreted according to a preliminary hypothesis of the photoconversion mechanism. High hydrogen productivity was achieved, in most cases higher than the literature benchmark. • Photoreforming of glucose tested under unconventional operating conditions. • Effect of different cocatalysts on titania revealed high activity for low Pt loading. • Tested levulinic acid, formic acid and glucose substrates as models for biomass hydrolysis. [ABSTRACT FROM AUTHOR]

Abstract Furfural is a toxic chemical compound that is widely applied as a solvent in a great many of industries, and it can cause many problems to the human beings and environment. Various methods of removing furfural from the wastewaters have been studied. AOPs methods are utilized for the elimination of a vast majority of the pollutants due to their high efficiency as well as for their lack of creating secondary contamination. Therefore, the present study aims at comparing the efficiency of UV/ZrO2 and UV/H2O2/ZrO2 photocatalytic processes in removing furfural from aqueous solutions. The solution’s initial pH, furfural’s concentration, zirconium catalyst dosage and time were investigated as the parameters influencing the removal efficiency by the two foresaid processes, and the effect of H2O2 addition in various concentrations into UV/H2O2/ZrO2 process was also evaluated. Spectrophotometer device was employed to assay the concentration of the residual furfural. The results indicated that the pH of the environment, the amount of the nanoparticle and H2O2 input concentration largely influence the furfural omission. The optimal condition for the removal of furfural in UV/ZrO2 process in an initial concentration of 20 mg/L, a pH equal to 3, a catalyst dose of 0.25 g/L during a period of 60-min time was 81.6%, and it was 99% for UV/H2O2/ZrO2 process in a pH equal to 7 with the addition of H2O2 for a concentration of 0.75 mL/L under the same conditions. Generally, it can be concluded that UV/H2O2/ZrO2 and UV/ZrO2 photocatalytic processes can effectively be applied to remove furfural from the aqueous solutions, especially in lower concentrations.

The application of TiO2 as a slurry catalyst for the degradation of contaminants of emerging concern (CEC) in liquid effluents has some drawbacks due to the difficulties in the catalyst reutilization. Thus, sophisticated and expensive separation methods are required after the reaction step. Alternatively, several types of materials have been used to support powder catalysts, so that fixed or fluidized bed reactors may be used. In this context, the objective of this work is to systematize and analyze the results of research inherent to the application of ceramic materials as support of TiO2 in the photocatalytic CEC removal from liquid effluents. Firstly, an overview is given about the treatment processes able to degrade CEC. In particular, the photocatalysts supported in ceramic materials are analyzed, namely the immobilization techniques applied to support TiO2 in these materials. Finally, a critical review of the literature dedicated to photocatalysis with supported TiO2 is presented, where the performance of the catalyst is considered as well as the main drivers and barriers for implementing this process. A focal point in the future is to investigate the possibility of depurating effluents and promote water reuse in safe conditions, and the supported TiO2 in ceramic materials may play a role in this scope.

Abstract: The severe energy crisis and environmental issues have led to an increase in research on the development of sustainable energy. Atomically thin 2D multinary nanosheets with tunable components show advantages for producing sustainable energy via photo, electrocatalysis processes. Here, recent progress of atomically thin 2D multinary nanosheets from the design, synthesis, tuning, and sustainable energy production via photo, electrocatalysis processes is summarized. The regulating strategies such as alloying, doping, vacancy engineering, pores construction, surface modification, and heterojunction are summarized, focusing on how to optimize the catalytic performance of atomically thin 2D multinary nanosheets. In addition, advancements in versatile energy‐related photo, electrocatalytic applications in the areas of oxygen evolution, oxygen reduction, hydrogen evolution, CO2 reduction, and nitrogen fixation are discussed. Finally, existing challenges and future research directions in this promising field are presented. [ABSTRACT FROM AUTHOR]

The aim of the present work was to experimentally evaluate an alternative advanced wastewater treatment system, which combines the action of photocatalytic oxidation with ceramic membrane filtration. Experiments were carried out using laboratory scale TiO2/UV photocatalytic reactor and tubular ceramic microfiltration (CMF) system to treat the secondary effluent (SE). A 100-nm pore size CMF membrane was investigated in cross flow mode under constant transmembrane pressure of 20 kPa. The results show that specific flux decline of CMF membrane with and without TiO2/UV photocatalytic treatment was 30 and 50%, respectively, after 60 min of filtration. Data evaluation revealed that the adsorption of organic compounds onto the TiO2 particles was dependent on the pH of the suspension and was considerably higher at low pH. The liquid chromatography-organic carbon detector (LC-OCD) technique was used to characterise the dissolved organic matter (DOM) present in the SE and was monitored following photocatalysis and CMF. The results showed that there was no removal of biopolymers and slight removal of humics, building blocks and the other oxidation by-products after TiO2/UV photocatalytic treatment. This result suggested that the various ions present in the SE act as scavengers, which considerably decrease the efficiency of the photocatalytic oxidation reactions. On the other hand, the CMF was effective for removing 50% of biopolymers with no further removal of other organic components after photocatalytic treatment. Thus, the quantity of biopolymers in SE has an apparent correlation with the filterability of water samples in CMF. [ABSTRACT FROM AUTHOR]

Leachate is one of the major problems of municipal waste landfills. Landfills produce a dark black colored liquid with high levels of chemical oxygen demand (COD) and heavy metals and low biochemical oxygen demand (BOD)/COD ratio. The objectives of this study were to evaluate the effectiveness of an electrochemical process using graphite and platinum electrodes and photocatalytic properties of titanium dioxide nanoparticles stabilized on bentonite at different reaction times for removal of chromium and organic materials from leachate. Equipment used in the electrochemical reactor included an anode electrode plate, a commercial platinum electrode and a graphite cathode. We also evaluated the impact of electrical current density (1–4 A/m²), reaction time (1–8 h), concentration of catalyst (1–4 g/L) and UV radiation intensity (3–8 UV lamps). The results showed that the removal efficiency increased with increasing reaction time, current density, intensity of UV radiation and dose of catalyst. Moreover, biodegradability (BOD/COD ratio) was improved. Based on the results, this electrochemical pretreatment process can remove organics materials, heavy metals, reduce organic load and increase wastewater biodegradability. Thus, it can be used as an efficient option for treating sewage and preventing environment pollution. [ABSTRACT FROM AUTHOR]

Using the first principle density function theory, based on the stabilized Pt/TiO 2 (001) structure, the adsorptions and reactions of the substances that may be involved in the reactions have been calculated. The most possible reaction path and reaction mechanism are obtained by the analysis of the adsorption energies and formation energies in reaction. The results indicate that the OH − plays an important role in the HCHO degradation process. The reaction can be expressed as HCHO + 2OH − → HCOOH + H 2 O and HCOOH + 2OH − → CO 2 + 2H 2 O, which is carried out continuously with a large heat release. [ABSTRACT FROM AUTHOR]

Normal 0 false false false EN-US X-NONE AR-SA MicrosoftInternetExplorer4 Background and Objectives: Aniline has been used in different processes of chemical industries, however due to its side effects on the environment, several methods have been considered for its removal. In this study, we evaluated the performance of photocatalytic process using ZnO nanoparticles (nZnO) and ultraviolet (UV) irradiation for removal of Aniline from a synthetic effluent.Materials and Methods: A 5L photocatalytic reactor made from Plexiglas, which the UV lamp (20w) installed in the center of that (inside a quartz jacket), was designed and nZnO (0.2-0.5 g/l) was being added into synthetic effluent with Aniline concentration of 250 ppm. After retention times of 30, 60, and 90 min, samples were centrifuged and supernatant was filtered using a 0.2 µ PTFE filter. The liquid-liquid method and Gas Chromatography instrument was used for extraction and analysis respectively.Results: Results showed that the photocatalytic process of nZnO+UV could effectively remove Aniline from effluent. Increasing trend in the removal efficiency of Aniline using nZnO = 0.5 g/l was slower in comparison with other nZnO concentrations and the ANOVA analysis shows no significant difference between removal efficiency of Aniline in different concentrations of nZnO. The most removal efficiency of Aniline (76.3%) was observed in alkaline pH, retention time of 90 min and nZnO of 0.5 g/l. Conclusion: It could be concluded that the photocatalytic process of nZnO+UV could be suitable technique for Aniline removal from effluents. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Arial; mso-bidi-theme-font:minor-bidi;}

Background and purpose: Aniline is widely used as raw material in many chemical industries. The aim of this study was to survey the photocatalytic degradation of aniline using magnesium oxide nanoparticles from aqueous solutions. Materials and methods: An experimental study was carried out in a 2 L volume batch reactor. Various parameters such as pH (3-11), dose of nanoparticles (0.1-1), contact time (15-120 min), initial aniline concentration (5-250 mg/L) and irradiation source power (8, 15 and 30 W) were investigated. The concentration of residual aniline was measured by UV spectrophotometer at λmax of 198 nm. Results: The results showed that photocatalytic process of nMgO+UV could effectively remove aniline from effluent. The optimal solution pH and dose of nanoparticles for 8 W, 15 W and 30 W UVA lamp were 7.0 and 0.6 g/L, 7 and 0.4 g/L, and 7 and 0.4 g/L, respectively. In 30 min optimum contact time the photocatalytic degradation efficiency decreased when the concentration of aniline was increased. In optimum conditions (5 mg/L of aniline and 30 min reaction time) the aniline removal efficiency was 90.63 % and COD removal was 87.02%. Conclusion: The photocatalytic process of nMgO+UV can be used as a suitable technique for aniline removal from aqueous solutions. [ABSTRACT FROM AUTHOR]

In this study, photocatalytic (photo-Fenton and H2O2/UV) and dark Fenton processes were used to remove ethylenethiourea (ETU) from water. The experiments were conducted in a photo-reactor with an 80 W mercury vapor lamp. The mineralization of ETU was determined by total organic carbon analysis, and ETU degradation was qualitatively monitored by the reduction of UV absorbance at 232 nm. A higher mineralization efficiency was obtained by using the photo-peroxidation process (UV/H2O2). Approximately 77% of ETU was mineralized within 120 min of the reaction using [H2O2]0= 400 mg L−1. The photo-Fenton process mineralized 70% of the ETU with [H2O2]0= 800 mg L−1and [Fe2+] = 400 mg L−1, and there is evidence that hydrogen peroxide was the limiting reagent in the reaction because it was rapidly consumed. Moreover, increasing the concentration of H2O2from 800 mg L−1to 1200 mg L−1did not enhance the degradation of ETU. Kinetics studies revealed that the pseudo-second-order model best fit the experimental conditions. Thekvalues for the UV/H2O2and photo-Fenton processes were determined to be 6.2 × 10−4mg L−1min−1and 7.7 × 10−4mg L−1min−1, respectively. The mineralization of ETU in the absence of hydrogen peroxide has led to the conclusion that ETU transformation products are susceptible to photolysis by UV light. These are promising results for further research. The processes that were investigated can be used to remove pesticide metabolites from drinking water sources and wastewater in developing countries. [ABSTRACT FROM AUTHOR]

Background and purpose: Cyanide (CN-) is of dangerous pollutants in the environment from industries such as electroplating, mining and paint entering into environment. The present study aimed to review the efficiency of cyanide removal by zirconia photocatalytic process with and without hydrogen peroxide (H2O2). Materials and methods: This was an applied-fundamental study and was conducted in Environmental Health Research Center. After constructing photoreactor, by changing variables nanoparticle dosage (0.25-4 g/l), pH (4-11), H2O2 amount (0.1-1 ml), cyanide concentration (2.5-75 mg/l) and exposure time (5-90 min), efficiency of the photocatalytic processes was studied with zirconia ZrO2 and H2O2 in the cyanide removal. Experiments were followed on real wastewater samples. 200 synthetic samples and 20 real samples were tested. Results: The maximum cyanide removal (2.5 mg/l) was about 96% by UV/ZrO2/H2O2 process under optimal conditions (0.75 g/L nanoparticles, 0.5ml H2O2 and pH = 8). Removal of cyanide (20 mg/l) by the UV/ZrO2/H2O2 was, 35, 38.75, 55, 56, 59, 61.25, 65, 71.5, 81 and 88.5%, respectively in 5-90 minutes. The efficiency of cyanide removal with UV/ZrO2/H2O2 process decreased from 95.6% to 50.4% in 2.5 to 75 mg/l of cyanide. The maximum cyanide removal (2.5 mg/l) was approximately 85.6% by UV/ZrO2 process under the optimal conditions (0.75 g/l nanoparticles and pH = 4). UV/ZrO2 process efficiency in the cyanide removal decreased from 85.6% to 36.4% in 2.5-75 mg/L of cyanide. The maximum cyanide removal from real wastewater was 54.08% and 72.8% with UV/ZrO2 and UV/ZrO2/H2O2 processes, respectively. Conclusion: Increasing nanoparticle, exposure time and reducing pH increased UV/ZrO2 process efficiency. Increasing cyanide concentration decreased efficiency of the both processes. Increasing H2O2 to optimum dosage (0.5 ml/100 ml CN) increased UV/ZrO2/H2O2 process efficiency, but higher levels of H2O2 decreased the process efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Studies involving the TiO2-assisted photodegradation of organic substances report that the processes are photocatalytic in nature. Yet, no evidence exists confirming such assertions. Previously, we examined the usage of relative photonic efficiencies [N. Serpone, G. Sauve, R. Koch, H. Tahiri, P. Pichat, P. Piccinini, E. Pelizzetti, H. Hidaka, J. Photochem. Photobiol. A: Chem. 94 (1996) 191; N. Serpone, J. Photochem. Photobiol. A: Chem. 104 (1997) 1] and quantum yields Φ [N. Serpone, R. Terzian, D. Lawless, P. Kennepohl, G. Sauve, J. Photochem. Photobiol. A: Chem. 73 (1993) 11] to systematize discrepant claims about process efficiencies. An experimental protocol is now available [N. Serpone, A. Salinaro, Pure Appl. Chem. 71 (1999) 303] to measure true Φ in heterogeneous media. Photoinduced reduction of O2 and photooxidation of H2 occurring on oxidized and reduced surfaces of ZrO2 were recently examined [A.V. Emeline, G.N. Kuzmin, L.L. Basov, N. Serpone, J. Photochem. Photobiol. A: Chem. 174 (2005) 214] to probe the spectral variations of the photoactivity and photo-selectivity of ZrO2 by determining Φ for the two redox reactions at various wavelengths of photoexcitation (200< λ <400nm). Irradiation of ZrO2 in the intrinsic absorption region (λ <260nm) led predominantly to photoreduction of O2, whereas photooxidation of H2 predominated on irradiation in the extrinsic spectral region (260< λ <360nm). A difficult task in heterogeneous catalysis and photocatalysis is determination of the actual number of active sites, an issue that has heretofore been elusive to assess the (photo)catalytic activity of a given material in heterogeneous solid–liquid and solid–gas (photo)catalysis. A kinetic description of the three turnover quantities, viz., turnover number (TON), turnover rate (TOR) and turnover frequency (TOF) has been described [N. Serpone, A. Salinaro, A.V. Emeline, V.K. Ryabchuk, J. Photochem. Photobiol. A: Chem. 130 (2000) 83], concluding that turnover quantities are conceptually distinct, with TON and TOR requiring knowledge of the number of active sites on the (photo)catalyst''s surface. Apparently, turnovers depend on the nature of the active state of the catalyst and how it is described. The number of surface-active sites on the ZrO2 particle surface have been determined quantitatively (∼1016 active centers) through thermoprogrammed desorption spectroscopy, affording an estimate of TONs for the photooxidation of H2 (TON>14.5) and photoreduction of O2 (TON>6.6) on ZrO2 and demonstrating for the first time that a photoreaction occurring on the surface of a metal oxide is truly photocatalytic [A.V. Emeline, A.V. Panasuk, N. Sheremetyeva, N. Serpone, J. Phys. Chem. B 109 (2005) 2785]. Photocoloration of a metal oxide such as ZrO2 (process of photoinduced formation of Zr3+, F- and V-type color centers) during a surface photochemical reaction was also used to assess whether a reaction is photocatalytic. Our study on the influence of simple photoreactions involving the photoreduction of O2, photooxidation of H2, photooxidation of H2 by adsorbed O2, and photoinduced transformation of NH3 and CO2 on the photocoloration of ZrO2 concluded that photoreactions involving NH3 and CO2 are non-photocatalytic processes, in contrast to the photooxidation of H2 which is photocatalytic [A.V. Emeline, G.V. Kataeva, A.V. Panasuk, V.K. Ryabchuk, N.V. Sheremetyeva, N. Serpone, J. Phys. Chem. B 109 (2005) 5175]. In this article, we describe the criteria and conditions by which a photoreaction taking place on the surface of a solid can be said to be photocatalytic by considering both a chemical approach and a physical approach. [Copyright &y& Elsevier]

The increasing use of the Earth's natural resources has generated increasing disposal of waste products and contamination of the environment. Many of these products are organic chemicals. Characteristic examples of waste products in the atmosphere, hydrosphere and soil are insecticides, herbicides and pesticides used to protect crops, accidental leakages and spills, and the continual discharge of waste by products in effluent streams from petrochemical and essential industries. To purify these contaminated atmospheres, hydrosphere and soil a procedure and process has been developing with minimal specific consumption energy from a renewable energy source. This paper will provide a survey and analysis of the parameters, thermal efficiency and conversion energy in the use of solar energy in the photochemical and photocatalytic degradation processes of organic effluents. As a consequence of the use of solar energy in the degradation of these effluents, a conceptual solution of a technical-technological and photocatalytic process is given for effluents which are located in watercourses and soil in Yugoslavia. [ABSTRACT FROM AUTHOR]

General aspects and perspectives of heterogeneous photocatalysis for the treatment of polluted aqueous effluents are presented. Some experimental results obtained by using various configurations of photocatalytic membrane reactors (PMRs) are reported. The configurations studied were: (i) irradiation of the cell containing the membrane, with three sub-cases: (i1) catalyst deposited on the membrane; (i2) catalyst in suspension, confined by means of the membrane; (i3) entrapment of the photocatalyst in a PSF membrane; (ii) irradiation of the re-circulation tank and catalyst in suspension confined by means of the membrane. In the case “(i)”, a preliminary investigation of membrane stability under UV irradiation was carried out. PMR characterization in photodegradation tests was mainly carried out in a recycle batch membrane reactor and, in some cases, in a continuous membrane reactor.The comparison between the first set of results, where the membrane was used only as a support for the photocatalyst, and the newest ones, where the adsorption of the pollutant on the membrane and membrane rejection play an important role in the global reactor performance, showed interesting perspectives and synergy for coupling photocatalysis and membranes. Furthermore, the configuration where the re-circulation tank was irradiated and the catalyst was used in suspension, appeared to be the most interesting for industrial applications. For example, in reactor optimization, high irradiation efficiency, high membrane permeate flowrate and selectivity can be obtained by sizing separately the “photocatalytic system” and the “membrane system” and taking advantage of all the best research results for each system. [Copyright &y& Elsevier]

• First comprehensive systematic review and meta -analysis on degradation of pesticides in aqueous solutions. • Recent applications in photocatalytic processes were discussed. • 137 and 22 studies were eligible for review and meta -analysis respectively. • From the pooled data, the degradation efficiency varied between 90.3 and 96.69%. Extensive use of pesticides and their slow degradation have resulted in contamination of environment, which inflicts damages on the ecosystem and human health. The presence of pesticides in aqueous media is of a global concern. Photocatalytic processes have gained a lot of attention over the last decades with regard to degradation of pesticides. This study is aimed at reviewing the most relevant reports on the application of the photocatalytic process involved in the degradation of pesticides in aqueous solutions. Moreover, the effects of influential variables such as catalyst amount, pH, concentration of pesticides, light intensity and contact time were discussed in detail. Within this study, three subgroups of pesticides were reviewed, namely insecticides, herbicides and fungicides. Meta-analysis was also conducted by the random-effects model. In addition, statistical analyses were accomplished by the R software. After the screening process, 22 articles were found to be suitable in the meta -analysis. Results of meta -analysis proved that the photocatalytic processes could remove pesticides with an average acceptable degradation efficiency of 93.36%. The average pooled percent of photocatalytic processes for the degradation of insecticides, herbicides and fungicides was 93.35 (95% CI: 89.89–96.81), 90.73 (95% CI: 80.44–101.02) and 100 (95% CI: 98.12–101.88), respectively. The results of the Begg's test (z = 0.4903, P = 0.6239) indicated that no bias regarding the potential publication was detected. Finally, it was demonstrated that photocatalytic processes are highly appropriate for the degradation of pesticides from aqueous solutions. [ABSTRACT FROM AUTHOR]

The removal of pharmaceuticals from wastewater is critical due to their considerable risk on ecosystems and human health. Additionally, they are resistant to conventional chemical and biological remediation methods. Two-dimensional nanomaterials are a promising approach to face this challenge due to their combination of high surface areas, high electrical conductivities, and partially optical transparency. This review discusses the state-of-the-art concerning their use as adsorbents, oxidation catalysts or photocatalysts, and electrochemical catalysts for water treatment purposes. The bibliographic search bases upon academic databases including articles published until August 2021. Regarding adsorption, high removal capacities (>200 mg g−1) and short equilibrium times (<30 min) are reported for molybdenum disulfide, metal-organic frameworks, MXenes, and graphene oxide/magnetite nanocomposites, attributed to a strong adsorbate-adsorbent chemical interaction. Concerning photocatalysis, MXenes and carbon nitride heterostructures show enhanced charge carriers separation, favoring the generation of reactive oxygen species to degrade most pharmaceuticals. Peroxymonosulfate activation via pure or photo-assisted catalytic oxidation is promising to completely degrade many compounds in less than 30 min. Future work should be focused on the exploration of greener synthesis methods, regeneration, and recycling at the end-of-life of two-dimensional materials towards their successful large-scale production and application. [ABSTRACT FROM AUTHOR]

The application of TiO2 as a slurry catalyst for the degradation of contaminants of emerging concern (CEC) in liquid effluents has some drawbacks due to the difficulties in the catalyst reutilization. Thus, sophisticated and expensive separation methods are required after the reaction step. Alternatively, several types of materials have been used to support powder catalysts, so that fixed or fluidized bed reactors may be used. In this context, the objective of this work is to systematize and analyze the results of research inherent to the application of ceramic materials as support of TiO2 in the photocatalytic CEC removal from liquid effluents. Firstly, an overview is given about the treatment processes able to degrade CEC. In particular, the photocatalysts supported in ceramic materials are analyzed, namely the immobilization techniques applied to support TiO2 in these materials. Finally, a critical review of the literature dedicated to photocatalysis with supported TiO2 is presented, where the performance of the catalyst is considered as well as the main drivers and barriers for implementing this process. A focal point in the future is to investigate the possibility of depurating effluents and promote water reuse in safe conditions, and the supported TiO2 in ceramic materials may play a role in this scope. [ABSTRACT FROM AUTHOR]

• Simultaneous coupling of photocatalysis and biotransformation in water was reviewed. • Synergistic performance was summarized for oxidation and reduction of pollutants. • Key factors affecting decontamination performance in coupled processes were analyzed. • Interaction mechanisms between photocatalysts and microorganisms were elucidated. Decontamination of water polluted with recalcitrant chemicals, such as phenolic and aromatic substances, for which conventional wastewater treatment processes are largely not effective, remains a major challenge all over the world. The simultaneous combination of photocatalytic and biological processes in a single system, either with or without the support of porous carriers, exhibits superior synergistic performance for removing refractory contaminants with the advantages of both photocatalysis and biotransformation. This promising emerging alternative, defined as simultaneous coupling here, has attracted increased attention and has been substantially developed over the last five years. To our best knowledge, this is the first critical review systematically focusing on the simultaneous coupling of photocatalytic and biological processes in enhancing decontamination of recalcitrants from water. The current review includes not only the synergy for pollutant oxidation/reduction removal and corresponding key factors affecting coupled systems, but also the underlying mechanisms of two different couplings in the interaction view of photocatalytic and biological responses. Last but not least, the challenges and opportunities faced by the coupling are pointed out. This review can provide useful information on the design and application of the synergistic coupling of chemical and biological processes for efficient and complete decontamination of recalcitrant compounds in water. [ABSTRACT FROM AUTHOR]

• Homogenous and heterogeneous photochemical decomposition of PFCs in contaminated water are reviewed. • Photo-oxidative, photo-reductive and metal-ion-mediated photo-redox homogenous processes are discussed. • Various photocatalysts in heterogeneous processes in terms of the instinct properties promoting PFOA decomposition are outlined. • Key perspectives for the photocatalytic removal of PFCs to promote its practical application in PFCs removal are summarized. Perfluorochemicals (PFCs) are a set of chemicals containing C-F bonds, which are concerned due to their bioaccumulation property, persistent and toxicological properties. Photocatalytic approaches have been widely studied for the effective removal of PFCs due to the mild operation conditions. This review aims to provide a comprehensive and up-to-date summary on the homogenous and heterogeneous photocatalytic processes for PFCs removal. Specifically, the homogenous photocatalytic methods for remediating PFCs are firstly discussed, including generation of hydrated electrons (e aq ‒) and its performance and mechanisms for photo-reductive destruction of PFCs, the active species responsible for photo-oxidative degradation of PFCs and the corresponding mechanisms, and metal-ion-mediated (Fe(III) mainly used) processes for the remediation of PFCs. The influences of molecular structures of PFCs and water matrix, such as dissolved oxygen, humic acid, nitrate, chloride on the homogenous photocatalytic degradation of PFCs are also discussed. For heterogeneous photocatalytic processes, various semiconductor photocatalysts used for the decomposition of perfluorooctanoic acid (PFOA) are then discussed in terms of their specific properties benefiting photocatalytic performances. The preparation methods for optimizing the performance of photocatalysts are also overviewed. Moreover, the photo-oxidative and photo-reductive pathways are summarized for remediating PFOA in the presences of different semiconductor photocatalysts, including active species responsible for the degradation. We finally put forward several key perspectives for the photocatalytic removal of PFCs to promote its practical application in PFCs-containing wastewater treatment, including the treatment of PFCs degradation products such as fluoride ion, and the development of noble-metal free photocatalysts that could efficiently remove PFCs under solar light irradiation. Image, graphical abstract [ABSTRACT FROM AUTHOR]

ZnO/Fe 2 O 3 /Clinoptilolite photocatalyst was synthesized through sol-gel method. The photocatalyst was characterized by XRD, XRF, EDX, FE-SEM, FT-IR, BET and UV-VIS DRS analyses. According to the XRD, FT-IR, and EDX results, the presence of ZnO and Fe 2 O 3 was confirmed on the clinoptilolite surface. Based on the XRF results, the molar ratio of Fe 3+ /ZnO in the photocatalyst was obtained as 0.06. The FE-SEM results confirmed stabilization of ZnO/Fe 2 O 3 on the clinoptilolite surface. Based on the BET results, the surface area and pore volume for the photocatalyst were obtained as 291.35 m 2 /g and 0.23 cm 3 /g, respectively. According to the UV-VIS DRS results, the band gap energy of the photocatalyst was measured as 3.38 eV. The performance of the synthesized photocatalyst in degrading metronidazole from contaminated water, as one of the most widely used antibiotics in pharmaceutical industries, was evaluated by response surface methodology. Operational factors including pH (4-10), metronidazole concentration (1-100 mg/l), irradiation time (45-180 min), photocatalyst concentration (0.5-2 g/l), and H 2 O 2 concentration (25-100 mg/l) were investigated. The optimal values of the factors in degrading 99% of the contaminant were as follows: irradiation time = 90 min, photocatalyst concentration = 1 g/l, pH = 10, H 2 O 2 concentration = 40 mg/l, and MNZ concentration = 60 mg/l.

The implementation of heterogeneous photo-nanocatalysts in organic syntheses has been investigated greatly in the last decade as a result of the increasing demand to achieve the organic reactions via the use of green approaches and through the availability of visible light source. Herein, the presented results describe the basic concepts and state-of-the-art of fundamental insight into key features that influence the catalytic performance in organic reactions to investigate and optimize a broad range of catalyzed organic transformations, that benefit the researchers in academia and chemical industry fields., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

The search for alternative water sources is pushing to the reuse of treated water coming from municipal wastewater treatment plants. However, this requires that tightened standards be fulfilled. Among them is the microbiological safety of reused water. Although chlorination is the mostly applied disinfection system, it presents several disadvantages, such as the high doses required and the possibility of formation of dangerous by-products. Moreover, the threat of antibiotic resistance genes (ARGs) spread throughout poorly treated water is requiring the implementation of more efficient disinfection systems. Ozone and photo assisted disinfection technologies are being given special attention to reach treated water with higher quality. Still, much must be done to optimize the processes so that cost-effective systems may be obtained. This review paper gives a critical overview on the application of ozone and photo-based disinfection systems, bearing in mind their advantages and disadvantages when applied to water and municipal wastewater. Also, the possibility of integrated disinfection systems is considered. [ABSTRACT FROM AUTHOR]

Furfural is a toxic chemical compound that is widely applied as a solvent in a great many of industries, and it can cause many problems to the human beings and environment. Various methods of removing furfural from the wastewaters have been studied. AOPs methods are utilized for the elimination of a vast majority of the pollutants due to their high efficiency as well as for their lack of creating secondary contamination. Therefore, the present study aims at comparing the efficiency of UV/ZrO2 and UV/H2O2/ZrO2 photocatalytic processes in removing furfural from aqueous solutions. The solution’s initial pH, furfural’s concentration, zirconium catalyst dosage and time were investigated as the parameters influencing the removal efficiency by the two foresaid processes, and the effect of H2O2 addition in various concentrations into UV/H2O2/ZrO2 process was also evaluated. Spectrophotometer device was employed to assay the concentration of the residual furfural. The results indicated that the pH of the environment, the amount of the nanoparticle and H2O2 input concentration largely influence the furfural omission. The optimal condition for the removal of furfural in UV/ZrO2 process in an initial concentration of 20 mg/L, a pH equal to 3, a catalyst dose of 0.25 g/L during a period of 60-min time was 81.6%, and it was 99% for UV/H2O2/ZrO2 process in a pH equal to 7 with the addition of H2O2 for a concentration of 0.75 mL/L under the same conditions. Generally, it can be concluded that UV/H2O2/ZrO2 and UV/ZrO2 photocatalytic processes can effectively be applied to remove furfural from the aqueous solutions, especially in lower concentrations. [ABSTRACT FROM AUTHOR]