Enhanced photocatalytic degradation of VOCs using Ln3+-TiO2 catalysts for indoor air purification

Enhanced photocatalytic degradation of amoxicillin using a spinning disc photocatalytic reactor (SDPR) with a novel Fe3O4@void@CuO/ZnO yolk-shell thin film nanostructure

Antibiotics are resistant compounds with low biological degradation that generally cannot be removed by conventional wastewater treatment processes. The use of yolk-shell nanostructures in spinning disc photocatalytic reactor (SDPR) enhances the removal efficiency due to their high surface-to-volume ratio and increased interaction between catalyst particles and reactants. The purpose of this study is to investigate the SDPR equipped to Fe3O4@void@CuO/ZnO yolk-shell thin film nanostructure (FCZ YS) in the presence of visible light illumination in the photocatalytic degradation of amoxicillin (AMX) from aqueous solutions. Stober, co-precipitation, and self-transformation methods were used for the synthesis of FCZ YS thin film nanostructure and the physical and chemical characteristics of the catalyst were analyzed by XRD, VSM,, EDX, FESEM, TEM, AFM, BET, contact angle (CA), and DRS. Then, the effect of different parameters including pH (3-11), initial concentration of AMX (10-50 mg/L), flow rate (10-25 mL/s) and rotational speed (100-400 rpm) at different times in the photocatalytic degradation of AMX were studied. The obtained results indicated that the highest degradation efficiency of 97.6% and constant reaction rate of AMX were obtained under LED visible light illumination and optimal conditions of pH = 5, initial AMX concentration of 30 mg/L, solution flow rate of 15 mL/s, rotational speed of 300 rpm and illumination time of 80 min. The durability and reusability of the nanostructure were tested, that after 5 runs had a suitable degradation rate. Considering the appropriate efficiency of amoxicillin degradation by FCZ YS nanostructure, the use of Fe3O4@void@CuO/ZnO thin film in SDPR is suggested in water and wastewater treatment processes.

How Well Do Our Adsorbents Actually Perform?-The Case of Dimethoate Removal Using Viscose Fiber-Derived Carbons

Growing pollution is making it necessary to find new strategies and materials for the removal of undesired compounds from the environment. Adsorption is still one of the simplest and most efficient routes for the remediation of air, soil, and water. However, the choice of adsorbent for a given application ultimately depends on its performance assessment results. Here, we show that the uptake of and capacity for dimethoate adsorption by different viscose-derived (activated) carbons strongly depend on the adsorbent dose applied in the adsorption measurements. The specific surface areas of the investigated materials varied across a wide range from 264 m² g^-1 to 2833 m² g^-1. For a dimethoate concentration of 5 × 10^-4 mol L^-1 and a high adsorbent dose of 10 mg mL^-1, the adsorption capacities were all below 15 mg g^-1. In the case of high-surface-area activated carbons, the uptakes were almost 100% under identical conditions. However, when the adsorbent dose was reduced to 0.01 mg mL^-1, uptake was significantly reduced, but adsorption capacities as high as 1280 mg g^-1 were obtained. Further, adsorption capacities were linked to adsorbents' physical and chemical properties (specific surface area, pore size distribution, chemical composition), and thermodynamic parameters for the adsorption process were evaluated. Based on the Gibbs free energy of the adsorption process, it can be suggested that physisorption was operative for all studied adsorbents. Finally, we suggest that a proper comparison of different adsorbents requires standardization of the protocols used to evaluate pollutant uptakes and adsorption capacities.

Synthesis and Application of Innovative and Environmentally Friendly Photocatalysts: A Review

Modern society faces two major challenges: removing pollutants from water and producing energy from renewable sources. To do this, science proposes innovative, low-cost, and environmentally friendly methods. The heterogeneous photocatalysis process fits perfectly in this scenario. In fact, with photocatalysis, it is possible both to mineralize contaminants that are not easily biodegradable and to produce hydrogen from the water splitting reaction or from the conversion of organic substances present in water. However, the main challenge in the field of heterogeneous photocatalysis is to produce low-cost and efficient photocatalysts active under visible light or sunlight. The objective of this review is to compare the new proposals for the synthesis of innovative photocatalysts that reflect the requirements of green chemistry, applied both in the removal of organic contaminants and in hydrogen production. From this comparison, we want to bring out the strengths and weaknesses of the proposals in the literature, but above all, new ideas to improve the efficiency of heterogeneous photocatalysis guaranteeing the principles of environmental and economic sustainability.

Recent Advances in Vehicle Exhaust Treatment with Photocatalytic Technology

Vehicle exhaust has been acknowledged as an essential factor affecting human health due to the extensive use of cars. Its main components include volatile organic compounds (VOCs) and nitrogen oxides (NOx), which can cause acute irritation and chronic diseases, and significant research on the treatment of vehicle exhaust has received increasing attention in recent decades. Recently, photocatalytic technology has been considered a practical approach for eliminating vehicle emissions. This review highlights the crucial role of photocatalytic technology in eliminating vehicle emissions using semiconductor catalysts. A particular emphasis has been placed on various photocatalytic materials, such as TiO2-based materials, Bi-based materials, and Metal–Organic Frameworks (MOFs), and their recent advances in the performance of VOC and NOx photodegradation. In addition, the applications of photocatalytic technology for the elimination of vehicle exhaust are presented (including photocatalysts combined with pavement surfaces, making photocatalysts into architectural coatings and photoreactors), which will offer a promising strategy for photocatalytic technology to remove vehicle exhaust.

The Visible light photodegradation of methyl orange and Escherichia coli O157:H7 in wastewater

Water pollution due to dyes and pathogens is problematic worldwide, and the disease burden is higher in low-income countries where water treatment facilities are usually inadequate. Thus the development of low-cost techniques for the removal of dyes and pathogens in aquatic systems is critical for safeguarding human and ecological health. In this work, we report the fabrication and use of a photocatalyst derived from waste from coal combustion in removing dyes and pathogens from wastewater. Higher TiO2 loading of the photocatalyst increased the removal efficiency for methyl orange (95.5%), and fluorine-doping improved the disinfection efficacy from 76% to 95% relative to unmodified material. Overall, the work effectively converted hazardous waste into a value-added product that has potential in point-of-use water treatment. Future research should focus on upscaling the technique, investigating the fate of the potential of the photocatalysts for multiple reuse, and the recovery of TiO2 in treated water.

Single-Atom (Iron-Based) Catalysts: Synthesis and Applications

Supported single-metal atom catalysts (SACs) are constituted of isolated active metal centers, which are heterogenized on inert supports such as graphene, porous carbon, and metal oxides. Their thermal stability, electronic properties, and catalytic activities can be controlled via interactions between the single-metal atom center and neighboring heteroatoms such as nitrogen, oxygen, and sulfur. Due to the atomic dispersion of the active catalytic centers, the amount of metal required for catalysis can be decreased, thus offering new possibilities to control the selectivity of a given transformation as well as to improve catalyst turnover frequencies and turnover numbers. This review aims to comprehensively summarize the synthesis of Fe-SACs with a focus on anchoring single atoms (SA) on carbon/graphene supports. The characterization of these advanced materials using various spectroscopic techniques and their applications in diverse research areas are described. When applicable, mechanistic investigations conducted to understand the specific behavior of Fe-SACs-based catalysts are highlighted, including the use of theoretical models.

Structural and Functional Behaviour of Ce-Doped Wide-Bandgap Semiconductors for Photo-Catalytic Applications

Increasing the photocatalytic efficiency of earth-abundant wide-bandgap semiconductors is of high interest for the development of cheap but effective light-driven chemical conversion processes. In this study, the coupling of ZnO and TiO2 with low contents of the rare-earth Ce species aimed to assess the photo-catalytic performance of the two semiconductors (SC). Structural and optical characterizations were performed to estimate the effect of the different interactions between Zn2+, Ti4+ and Ce4+ ions, and how the photo-responsive behaviour of Ce-Ti and Ce-Zn composites was affected. Therefore, photo-catalytic tests were performed for all Ce-modified SC to assess both their photo-oxidative and photo-reductive properties. Amongst all the tested materials, only Zn-based samples resulted in being suitable for the photo-oxidation of the methylene blue (MB) organic pollutant in a synthetic-dependent fashion.

Photocatalytic activity of Pr-modified TiO2 for the degradation of bisphenol A

Praseodymium doped TiO2 nanoparticles were successfully prepared by the sol–gel method and characterized by X-ray powder diffraction, N2 adsorption–desorption isotherm, and UV–vis spectroscopy. The effects of the dopant on the crystallite size, specific surface area, average pore diameter, pore volume, and bandgap energy were investigated. The photocatalytic activity of the catalysts was evaluated by bisphenol A degradation and mineralization, which is a representative endocrine disruptor. Furthermore, under visible light irradiation the Pr-modified TiO2 photocatalysts exhibited higher photocatalytic efficiency than unmodified TiO2. When praseodymium was loaded (1.0–5.0%) onto the surface of TiO2, the rates of degradation and mineralization were increased 3–5 times.

Efficient Photocatalytic Degradation of Gaseous Benzene and Toluene over Novel Hybrid PIL@TiO2/m-GO Composites

In this work, the PIL (poly ionic liquid)@TiO2 composite was designed with two polymerized ionic liquid concentrations (low and high) and evaluated for pollutant degradation activity for benzene and toluene. The results showed that PIL (low)@TiO2 composite was more active than PIL (high)@TiO2 composites. The photodegradation rate of benzene and toluene pollutants by PIL (low)@TiO2 and PIL (high)@TiO2 composites was obtained as 86% and 74%, and 59% and 46%, respectively, under optimized conditions. The bandgap of TiO2 was markedly lowered (3.2 eV to 2.2 eV) due to the formation of PIL (low)@TiO2 composite. Besides, graphene oxide (GO) was used to grow the nano-photocatalysts’ specific surface area. The as-synthesized PIL (low)@TiO2@GO composite showed higher efficiency for benzene and toluene degradation which corresponds to 91% and 83%, respectively. The resultant novel hybrid photocatalyst (PIL@TiO2/m-GO) was prepared and appropriately characterized for their microstructural, morphology, and catalytic properties. Among the studied photocatalysts, the PIL (low)@TiO2@m-GO composite exhibits the highest activity in the degradation of benzene (97%) and toluene (97%). The ultimate bandgap of the composite reached 2.1 eV. Our results showed that the as-prepared composites hold an essential role for future considerations over organic pollutants.

Synthesis, Characterization, and Photocatalytic Evaluation of Manganese (III) Phthalocyanine Sensitized ZnWO4 (ZnWO4MnPc) for Bisphenol A Degradation under UV Irradiation

ZnWO₄MnPc was synthesized via a hydrothermal autoclave method with 1 wt.% manganese (iii) phthalocyanine content. The material was characterized for its structural and morphological features via X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, transmission emission microscopy (TEM), scanning electron microscopy-Energy dispersive X-ray spectroscopy (SEM-EDX), N₂ adsorption-desorption at 77K, X-ray photoelectron spectroscopy (XPS), and UV-visible/diffuse reflectance spectroscopy(UV-vis/DRS). ZnWO₄MnPc photocatalytic performance was tested on the degradation of bisphenol A (BPA). The ZnWO₄MnPc material removed 60% of BPA after 4 h of 365 nm UV irradiation. Degradation process improved significantly to about 80% removal in the presence of added 5 mM H₂O₂ after 4 h irradiation. Almost 100% removal was achieved after 30 min under 450 nm visible light irradiation in the presence of same concentration of H₂O₂. The effect of ions and humic acid (HA) towards BPA removal was also investigated.

Development of Pharmaceutical VOCs Elimination by Catalytic Processes in China

As a byproduct of emerging as one of the world’s key producers of pharmaceuticals, China is now challenged by the emission of harmful pharmaceutical VOCs. In this review, the catalogue and volume of VOCs emitted by the pharmaceutical industry in China was introduced. The commonly used VOC removal processes and technologies was recommended by some typical examples. The progress of catalytic combustion, photocatalytic oxidation, non-thermal plasma, and electron beam treatment were presented, especially the development of catalysts. The advantages and shortages of these technologies in recent years were discussed and analyzed. Lastly, the development of VOCs elimination technologies and the most promising technology were discussed.

Promotion effect of strong metal-support interaction to thermocatalytic, photocatalytic, and photothermocatalytic oxidation of toluene on Pt/SrTiO3

The importance of strong metal-support interaction (SMSI) in reducible oxide supported noble metal nanoparticles (NP) has been recognized in many thermocatalytic systems but rarely explored in photocatalytic and photothermocatalytic systems. Herein, the promotion effect of SMSI in strontium titanate (STO) supported Pt NP for thermocatalytic, photocatalytic, and photothermocatalytic oxidation (TCO, PCO and PTO) of toluene is reported. SMSI in Pt/STO is achieved through calcination in air (Air-Pt/STO), reduction in H₂ atmosphere (H₂-Pt/STO), wet reduction in HCHO solution (HCHO-Pt/STO) or NaBH₄ solutions (NaBH₄-Pt/STO), resulting in the formation of chemisorbed oxygen and negatively charged Pt NP and promoting oxygen activation in TCO and surface plasmon resonance effects of Pt NP in visible-light-induced PCO and PTO. Both TCO and PCO activities go along with the degree of SMSI as Air-Pt/STO > H₂-Pt/STO > HCHO-Pt/STO > NaBH₄-Pt/STO. Under both visible-light illuminating and thermal environment at 150 °C, the PTO toluene degradation efficiency of Air-Pt/STO is further improved with a factor of 32 times or 9 times than the single PCO or TCO process. The unique synergistic photothermocatalytic oxidation performance of Air-Pt/STO is ascribed to the function of Pt NP and the effect of SMSI. Our findings provide a facile way to design multifunctional supported noble metal catalysts for efficient VOCs degradation process.

A Review on Catalytic Nanomaterials for Volatile Organic Compounds VOC Removal and Their Applications for Healthy Buildings

In order to improve the indoor air quality, volatile organic compounds (VOCs) can be removed via an efficient approach by using catalysts. This review proposed a comprehensive summary of various nanomaterials for thermal/photo-catalytic removal of VOCs. These representative materials are mainly categorized as carbon-based and metallic oxides materials, and their morphologies, synthesis techniques, and performances have been explained in detail. To improve the indoor and outdoor air quality, the catalytic nanomaterials can be utilized for emerging building applications such as VOC-reduction coatings, paints, air filters, and construction materials. Due to the characteristics of low cost, non-toxic and high chemical stability, metallic oxides such as TiO₂ and ZnO have been widely investigated for decades and dominate the application market of VOC-removal catalyst in buildings. Since other catalysts also showed brilliant performance and have been theoretically researched, they can be potential candidates for applications in future healthy buildings. This review will contribute to further knowledge and greater potential applications of promising VOC-reducing catalytic nanomaterials on healthier buildings for a better indoor and outdoor environment well-being.

Recent Advances and Applications of Semiconductor Photocatalytic Technology

Along with the development of industry and the improvement of people’s living standards, peoples’ demand on resources has greatly increased, causing energy crises and environmental pollution. In recent years, photocatalytic technology has shown great potential as a low-cost, environmentally-friendly, and sustainable technology, and it has become a hot research topic. However, current photocatalytic technology cannot meet industrial requirements. The biggest challenge in the industrialization of photocatalyst technology is the development of an ideal photocatalyst, which should possess four features, including a high photocatalytic efficiency, a large specific surface area, a full utilization of sunlight, and recyclability. In this review, starting from the photocatalytic reaction mechanism and the preparation of the photocatalyst, we review the classification of current photocatalysts and the methods for improving photocatalytic performance; we also further discuss the potential industrial usage of photocatalytic technology. This review also aims to provide basic and comprehensive information on the industrialization of photocatalysis technology.

Thermal desorption for remediation of contaminated soil: A review

Soil pollution has become a global environmental concern. Thermal desorption is one of the methods commonly used to remediate contaminated soil. This method has received increasing attention for remediating contaminated sites due to its advantages, such as suitability to different types of contaminants, short treatment period, high efficiency, high safety, and capability to recycle soil and contaminants. This paper provides a comprehensive review of studies on thermal desorption. Introduction of the mechanism, classification, and cost of thermal desorption is presented. Factors affecting the performance of thermal desorption (heating temperature, heating time, heating rate, carrier gas, soil particle size, moisture content, initial concentration of contaminants, and additives) are reviewed. Thermal desorption produces off-gases, which are mostly organic compounds and may result in secondary pollution. Thus far, treatment methods for off-gas have not been systematically investigated. This paper also summarizes current methods for treatment of off-gas in the soil field and of volatile organic compounds in atmospheric and water pollution fields. Several feasible off-gas treatment methods are also comparatively analyzed, and the corresponding principles, advantages, disadvantages, and application ranges are discussed.

Titanium oxide based photocatalytic materials development and their role of in the air pollutants degradation: Overview and forecast

Due to the anthropogenic pollution, especially the environmental crisis caused by air pollutants, the development of air pollutant degradation photocatalyst has become one of the major directions to the crisis relief. Among them, titania (titanium dioxide, TiO₂) family materials were extensively studied in the past two decades due to their strong activity in the photocatalytic reactions. However, TiO₂ had a drawback of large bandgap which limited its applications, several modification techniques were hence developed to enhance its catalytic activity and light sensitivity. In recent years, other metal oxide based materials have been developed as replacements for TiO₂ photocatalysts. In this review, background information and developments from pure TiO₂ to chemically modified TiO₂-based materials as photocatalysts were discussed in detail, which covered their basic properties and their role in the air pollutant removal. It also proposes to solve the shortcomings of TiO₂ by developing other metal oxide-based materials and predict the future development of TiO₂ materials in future environmental applications.

Improved photo-induced charge carriers separation through the addition of erbium on TiO2 nanoparticles and its effect on photocatalytic degradation of rhodamine B

Er_xTi_1-xO₂ nanocomposites was prepared by a simple sol-gel method with various proportion of erbium viz., x=0.02, x=0.04, x=0.06, x=0.08 and x=0.10. The prepared nanocomposites were studied using XRD, UV-Vis DRS, Raman spectra, HR-SEM, EDS, TEM, PL and impedance spectroscopy. XRD revealed that modified TiO₂ nanocomposites possessed only the anatase phase with crystallite sizes of about 8.1 to 12.7nm and which is well consistent with TEM analysis. It is seen that erbium ion exist in the nanocomposites based on the analysis of EDS. HR-SEM analysis revealed that the Er_xTi_1-xO₂ nanocomposites are spherical in shape with size between 10 and 20nm. The amount of erbium remarkably affects the structural, optical and electrical properties. Loading erbium could produce 4f energy levels between valence and conduction bands thus narrowing optical band gap and generates visible absorption peaks. It was found that erbium modified TiO₂ nanocomposites induced a shift in Raman. The enhancement of life time of charge carriers was observed on erbium inclusion.

Role of lanthanum species in improving the photocatalytic activity of titanium dioxide

Lanthanum modification resulted in the additional formation of Ti³⁺ states, which enhanced the charge transfer and separation. Consequently, the photocatalytic activity of TiO₂ under UV light irradiation was significantly improved.

Emerging trends in photodegradation of petrochemical wastes: a review

Various human activities like mining and extraction of mineral oils have been used for the modernization of society and well-beings. However, the by-products such as petrochemical wastes generated from such industries are carcinogenic and toxic, which had increased environmental pollution and risks to human health several folds. Various methods such as physical, chemical and biological methods have been used to degrade these pollutants from wastewater. Advance oxidation processes (AOPs) are evolving techniques for efficient sequestration of chemically stable and less biodegradable organic pollutants. In the present review, photocatalytic degradation of petrochemical wastes containing monoaromatic and poly-aromatic hydrocarbons has been studied using various heterogeneous photocatalysts (such as TiO₂, ZnO and CdS. The present article seeks to offer a scientific and technical overview of the current trend in the use of the photocatalyst for remediation and degradation of petrochemical waste depending upon the recent advances in photodegradation of petrochemical research using bibliometric analysis. We further outlined the effect of various heterogeneous catalysts and their ecotoxicity, various degradation pathways of petrochemical wastes, the key regulatory parameters and the reactors used. A critical analysis of the available literature revealed that TiO₂ is widely reported in the degradation processes along with other semiconductors/nanomaterials in visible and UV light irradiation. Further, various degradation studies have been carried out at laboratory scale in the presence of UV light. However, further elaborative research is needed for successful application of the laboratory scale techniques to pilot-scale operation and to develop environmental friendly catalysts which support the sustainable treatment technology with the "zero concept" of industrial wastewater. Nevertheless, there is a need to develop more effective methods which consume less energy and are more efficient in pilot scale for the demineralization of pollutant.

Gaseous benzene degradation by photocatalysis using ZnO + Zn2TiO4 thin films obtained by sol-gel process

The benzene pollutant in gaseous phase was successfully degraded by using ZnO + Zn2TiO4 multicomponent oxide thin films as photocatalysts. The films were obtained with different Ti/Zn ratios (0, 0.20, 0.40, 0.45, 0.50, 0.67, 0.84, and 1) by the sol-gel route. The initial level of benzene concentration was 110 ± 10 ppm. The process was carried out under different conditions of relative humidity (RH): 25, 50, and 80 % in a batch-type reactor, at room temperature. The results show benzene degradation near to 95 % at t = 240 min, where the multicomponent oxide semiconductor has a Ti/Zn ratio of 0.67. Meanwhile, with the TiO2 thin films, only a degradation of 70 % was reached at the same measurement conditions. This synergistic effect on the photocatalytic activity is a result of the coupling of both semiconductor oxides. An adverse effect on the photocatalytic activity was observed as the relative humidity increases.

Summary of performance data for technologies to control gaseous, odor, and particulate emissions from livestock operations: Air management practices assessment tool (AMPAT)

The livestock and poultry production industry, regulatory agencies, and researchers lack a current, science-based guide and data base for evaluation of air quality mitigation technologies. Data collected from science-based review of mitigation technologies using practical, stakeholders-oriented evaluation criteria to identify knowledge gaps/needs and focuses for future research efforts on technologies and areas with the greatest impact potential is presented in the Literature Database tab on the air management practices tool (AMPAT). The AMPAT is web-based (available at www.agronext.iastate.edu/ampat) and provides an objective overview of mitigation practices best suited to address odor, gaseous, and particulate matter (PM) emissions at livestock operations. The data was compiled into Excel spreadsheets from a literature review of 265 papers was performed to (1) evaluate mitigation technologies performance for emissions of odor, volatile organic compounds (VOCs), ammonia (NH₃), hydrogen sulfide (H₂S), particulate matter (PM), and greenhouse gases (GHGs) and to (2) inform future research needs.

Removal of Indoor Volatile Organic Compounds via Photocatalytic Oxidation: A Short Review and Prospect

Volatile organic compounds (VOCs) are ubiquitous in indoor environments. Inhalation of VOCs can cause irritation, difficulty breathing, and nausea, and damage the central nervous system as well as other organs. Formaldehyde is a particularly important VOC as it is even a carcinogen. Removal of VOCs is thus critical to control indoor air quality (IAQ). Photocatalytic oxidation has demonstrated feasibility to remove toxic VOCs and formaldehyde from indoor environments. The technique is highly-chemical stable, inexpensive, non-toxic, and capable of removing a wide variety of organics under light irradiation. In this paper, we review and summarize the traditional air cleaning methods and current photocatalytic oxidation approaches in both of VOCs and formaldehyde degradation in indoor environments. Influencing factors such as temperature, relative humidity, deactivation and reactivations of the photocatalyst are discussed. Aspects of the application of the photocatalytic technique to improve the IAQ are suggested.

The preparation of TiO2 composite materials modified with Ce and tourmaline and the study of their photocatalytic activity

The synergistic effects of tourmaline and Ce on the degradation of methyl orange by a TiO₂ composite photocatalyst are described.

Evaluation of the photocatalytic activity of Ln3+-TiO2 nanomaterial using fluorescence technique for real wastewater treatment

Evaluation the photocatalytic activity of different Ln(3+) modified TiO2 nanomaterials using fluorescence based technique has rarely been reported. In the present work, xmol Ln(3+) modified TiO2 nanomaterials (Ln = Nd(3+), Sm(3+), Eu(3+), Gd(3+), Dy(3+) and Er(3+) ions; x = 0.005, 0.008, 0.01, 0.02 and 0.03) were synthesized by sol-gel method and characterized using different advanced techniques. The photocatalytic efficiency of the modified TiO2 expressed in the charge carrier separation and OH radicals formation were assigned using TiO2 fluorescence quenching and fluorescence probe methods, respectively. The obtained fluorescence measurements confirm that doping treatment significantly decreases the electron-hole recombination probability in the obtained Ln(3+)/TiO2. Moreover, the rate of OH radicals formation is increased by doping. The highly active nanoparticles (0.02Gd(3+)/TiO2 and 0.01Eu(3+)/TiO2) were applied for industrial wastewater treatment using solar radiation as a renewable energy source.

SYNTHESIS OF Mg DOPED TiO2 NANOCRYSTALS PREPARED BY WET-CHEMICAL METHOD: OPTICAL AND MICROSCOPIC STUDIES

In this work, we report the successful formation of MgO doped TiO 2 nanocrystals (NCs) by simple wet-chemical method. The XRD exhibits a marginal decrease in the crystalline size of TiO 2 nanosamples by the addition of MgO dopant. UV–Vis spectral analysis shows that the addition of MgO in TiO 2 resulted in the red shift of the absorption edge. The optical energy band-gap and molecular vibrational analysis of doped nanosample was ascertained from photoluminescence (PL) and micro-Raman scattering technique respectively. HR-TEM analysis reveals that the substitution has sharply reduced the particle size of TiO 2 NCs .

Method of removal of volatile organic compounds by using wet scrubber coupled with photo-Fenton reaction--preventing emission of by-products

The photo-Fenton reaction was applied as a novel method for the removal of volatile organic compounds (VOCs) in the gas phase, and its effectiveness was experimentally examined. In conventional VOCs removal methods using a photocatalyst or ozone, VOCs are oxidized in the gas phase. Therefore, incompletely oxidized intermediates, which may have adverse effects on health, are likely to contaminate the treated air. On the other hand, in the VOCs removal method developed in this study, because the VOCs are oxidized in the liquid phase by the photo-Fenton reaction, any incompletely oxidized intermediates produced are confined to the liquid phase. As a result, the contamination of the treated air by these harmful intermediates can be prevented. Using a semi-batch process, it was found that the removal efficiency for toluene in a one-pass test (residence time of 17s) was 61%, for an inlet toluene gas concentration of 930 ppbv, an initial iron ion concentration of 20 mg L(-1), and an initial hydrogen peroxide concentration of 630 mg L(-1). The removal efficiency was almost constant as long as H(2)O(2) was present in the solution. Proton transfer reaction mass spectrometry analysis confirmed the absence of any incompletely oxidized intermediates in the treated air.

Comparative study of photocatalytic and photoelectrocatalytic properties of alachlor using different morphology TiO2/Ti photoelectrodes

Wormhole-shaped TiO(2)/Ti (WT) and nanotube-shaped TiO(2)/Ti (TNT) photoelectrodes were prepared by anodic oxidation method. The morphology and structure were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was found that both crystal types of WT and TNT photoelectrodes were composed of anatase and rutile TiO(2) phases; however TNT photoelectrodes had highly ordered nanostructure. The photoelectrochemical (PECH) and photoelectrocatalytic (PEC) properties of WT and TNT photoelectrodes were investigated by photocurrent transient, open-circuit potential and degradation rate of alachlor under the artificial solar light illumination. All results showed that TNT photoelectrodes prepared in NaF-Na(2)SO(4) solution have more excellent photoelectron properties than WT photoelectrodes prepared in H(2)SO(4) solution. The photocatalytic (PC) and PEC experiments of alachlor showed that PC and PEC activities of TNT photoelectrodes were superior to WT photoelectrodes. At applied bias potentials the degradation rate of alachlor at TNT photoelectrodes increased significantly to 94.5%. The higher PC and PEC performance of TNT photoelectrodes were ascribed to the long-range ordered structure and short-orientation diffusion distance of photogenerated carries.

Synthesis of mesoporous BiOBr 3D microspheres and their photodecomposition for toluene

In this article, a facile solvothermal method was introduced to synthesize mesoporous BiOBr microspheres with Bi(NO(3))(3) as Bi source. The synthesized catalysts were characterized by XRD, SEM, TEM, XPS, UV-vis, TG-DTA, and N(2)-adsorption-desorption, and their photoactivity was evaluated by gaseous toluene both under UV and UV-vis irradiation with Degussa TiO(2) P(25) as reference. The prepared BiOBr catalysts were of pure tetragonal phase and its band gap energy was calculated to be about 2.64eV. Comparing with P(25), BiOBr showed promoted photocatalytic activity under UV-vis irradiation, during which more than 90% of toluene was eliminated after 5h irradiation. Kinetic analysis further demonstrated the enhanced activity of BiOBr under UV-vis irradiation and the reaction rate constant k of BiOBr was nearly 2 times higher than that of P(25). The superior activity of BiOBr under UV-vis irradiation can be attributed to its hierarchical structure and suitable band gap energy. Moreover, the reacted intermediates under different light source were identified by GC-MS. Fifteen main intermediates were identified and a tentative pathway of toluene degradation by BiOBr was proposed.