Application Of Heterogeneous Photocatalysis Research Articles

Synthetic Chemistry in Flow: From Photolysis & Homogeneous Photocatalysis to Heterogeneous Photocatalysis.

Photocatalytic synthesis of value-added chemicals has gained increasing attention in recent years owing to its versatility in driving many important reactions under ambient conditions. Selective hydrogenation, oxidation, coupling, and halogenation with a high conversion of the reactants have been realized using designed photocatalysts in batch reactors with small volumes at a laboratory scale; however, scaling-up remains a critical challenge due to inefficient utilization of incident light and active sites of the photocatalysts, resulting in poor catalytic performance that hinders its practical applications. Flow systems are considered one of the solutions for practical applications of light-driven reactions and have experienced great success in photolytic and homogeneous photocatalysis, yet their applications in heterogeneous photocatalysis are still under development. In this perspective, we have summarized recent progress in photolytic and photocatalytic synthetic chemistry performed in flow systems from the view of reactor design with a special focus on heterogeneous photocatalysis. The advantages and limitations of different flow systems, as well as some practical considerations of design strategies are discussed.

Ceramic membrane reactor integrated with UV/O3/Catalyst Beads for treating real textile wastewater: Enhanced effluent quality, fouling control and molecular transformations of DOM

A ceramic membrane reactor (CMR) was employed to treat real textile wastewater with the simultaneous use of UV, O3, and photocatalytic beads for dissolved organic matter (DOM) transformation and membrane fouling control. The O3 treatment exhibited high performance in color removal. Simultaneous use of UV and ozonation (UV/O3) resulted in 91% and 64% color and chemical oxygen demand (COD) removal, respectively, and delayed (3-fold) fouling time compared to UV alone. A combination of TiO2-loaded polymeric beads with UV/O3 (UV/O3/Beads) further enhanced the color (96%) and COD (86%) removal as well as improved fouling control by 9-folds compared to the control (Air alone) experiment. Three-dimensional excitation-emission matrix (3-D EEM) fluorescence spectra revealed minimum DOM and synergistic effects of UV, O3, and photocatalytic beads (UV/O3/Beads) in the degradation of fluorescent DOM. The •OH radicals were leading in degrading organic pollutants during the treatment. Transformations of heteroatomic DOMs were confirmed by the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). S-containing compounds in the treated samples appeared in a reduced state (lower H/C and O/C ratios), indicating the transformation of R–SO3 to R–S–R. Whereas N-containing DOM was mostly oxidized. UV/O3 rapidly transformed dye molecules to colorless, creating suitable conditions for photocatalytic beads for accelerated degradation of pollutants. Also, the PTR-TOF-MS analysis revealed the successful removal of toxic VOCs (Methanethiol, Allylamine, Cyclohexenes, Butanes, Propanes, and Hydrazines) from wastewater by the UV/O3/Beads treatment. Based on these findings, DOM transformations could be better understood, and the simultaneous application of heterogeneous photocatalysis and UV/O3 could be safely recommended as a promising technology for treating industrial wastewater.

Tungsten Oxide Morphology-Dependent Au/TiO2/WO3 Heterostructures with Applications in Heterogenous Photocatalysis and Surface-Enhanced Raman Spectroscopy

Developing highly efficient Au/TiO2/WO3 heterostructures with applications in heterogeneous photocatalysis (photocatalytic degradation) and surface-enhanced Raman spectroscopy (dye detection) is currently of paramount significance. Au/TiO2/WO3 heterostructures were obtained via heat or time-assisted synthesis routes developed by slightly modifying the Turkevich–Frens synthesis methods and were investigated by TEM, SEM, XRD, Raman spectroscopy, XPS, photoluminescence, and UV–vis DRS techniques. Structural features, such as WO3 crystalline phases, TiO2 surface defects, as well as the WO3 (220) to TiO2-A (101) ratio, were the key parameters needed to obtain heterostructures with enhanced photocatalytic activity for removing oxalic acid, phenol, methyl orange, and aspirin. Photodegradation efficiencies of 95.9 and 96.9% for oxalic acid; above 96% (except one composite) for phenol; 90.1 and 97.9% for methyl orange; and 81.6 and 82.1% for aspirin were obtained. By employing the SERS technique, the detection limit of crystal violet dye, depending on the heterostructure, was found to be between 10−7–10−8 M. The most promising composite was Au/TiO2/WO3-HW-TA it yielded conversion rates of 82.1, 95.9 and 96.8% for aspirin, oxalic acid, and phenol, respectively, and its detection limit for crystal violet was 10−8 M. Au/TiO2/WO3-NWH-HA achieved 90.1, 96.6 and 99.0% degradation efficiency for methyl orange, oxalic acid, and phenol, respectively, whereas its limit of detection was 10−7 M. The Au/TiO2/WO3 heterojunctions exhibited excellent stability as SERS substrates, yielding strong-intensity Raman signals of the pollutant molecules even after a long period of time.

TiO2-CeO2 assisted heterostructures for photocatalytic mitigation of environmental pollutants: A comprehensive study on band gap engineering and mechanistic aspects

Industrial pollution is a substantial problem in the growing world of continuous innovative products and intensive developments. Pollution due to organic contaminants is the major detrimental components to environmental cleanness and sustainability. The textile industries alone produce about 1.3 million various dyes and pigments that absorb and reflect sunlight in water. This process highly affects the photosynthetic cycle of algae and other living organisms, thus balancing natural ecosystem. The breakdown of organic pollutants into harmful products, which are mutagenic, carcinogenic, and toxic to living organisms, creates a serious environmental concern globally. Nevertheless, recently application of heterogeneous photocatalysis in facilitating the removal of these organic effluents is very attractive and efficient, using various semiconductor-based composite materials which act as catalysts under light irradiation. This review focuses on recent developments of TiO2-CeO2 based nanostructure semiconductor materials, which include structural and interfacial ameliorations such as doping with other metals, non-metals, metal oxides and carbonaceous materials. Both TiO2 and CeO2 are highly redox and exchangeable (Ti+4/Ti+3 and Ce+4/Ce+3), and their performance is boasted by their associated defects and oxygen vacancy structure properties, making them amenable to high photoactivity performances. Herein, the effect of various synthesis factors on structural, electronic, optical, and morphological properties, and thus on modification of band gap edges, as well as on their photocatalytic activity and applications, is also reviewed.

Photocatalytic Degradation of Pharmaceutical Amisulpride Using g-C3N4 Catalyst and UV-A Irradiation

In the present study, the photocatalytic degradation of amisulpride using g-C3N4 catalyst under UV-A irradiation was investigated. The photocatalytic process was evaluated in terms of its effectiveness to remove amisulpride from ultrapure and real municipal wastewater. High removal percentages were achieved in both aqueous matrices. However, a slower degradation rate was observed using wastewater as matrix that could be attributed to its complex chemical composition. The transformation products (TPs) were identified with liquid chromatography–mass spectrometry (LC–MS) in both ultrapure and real municipal wastewater. Based on the identified TPs, the photocatalytic degradation pathways of amisulpride are proposed which include mainly oxidation, dealkylation, and cleavage of the methoxy group. Moreover, the contribution of reactive species to the degradation mechanism was studied using well-documented scavengers, and the significant role of h+ and O2•− in the reaction mechanism was proved. The evolution of ecotoxicity was also estimated using microalgae Chlorococcum sp. and Dunaliella tertiolecta. Low toxicity was observed during the overall process without the formation of toxic TPs when ultrapure water was used as matrix. In the case of real municipal wastewater, an increased toxicity was observed at the beginning of the process which is attributed to the composition of the matrix. The application of heterogeneous photocatalysis reduced the toxicity, and almost complete detoxification was achieved at the end of the process. Our results are in accordance with literature data that reported that heterogeneous photocatalysis is effective for the removal of amisulpride from aqueous matrices.

Zinc tungstate: a review on its application as heterogeneous photocatalyst

ZnWO4 crystallizes in a monoclinic wolframite-like structure, which has been studied for applications in heterogeneous photocatalysis for degradation, oxidation, and reduction of various contaminants. This type of tungstate has proved to be an efficient photocatalyst under both ultraviolet and visible light irradiation and, when ZnWO4 forms a heterostructure with other semiconductors or when it is doped with different ions, it has a great efficiency under sunlight irradiation. For instance, the optimization of ZnWO4 efficiency has been attained by its heterojunction with different semiconductors such as ZnO, one of the most used materials for this purpose, but also with other compounds such as BiOBr, FeWO4, TiO2, WO3, Bi2WO6, among others. In addition, doping ZnWO4 with the Ti4+, Bi3+, Ce3+, and Co2+ metal ions or with nonmetals (F- and N3-) can also increase the photocatalytic yield of the material. The photocatalytic properties of ZnWO4-based catalysts have been explored toward inorganic and organic molecules. However, among the variety of target molecules, organic pollutants such as methylene blue, methyl orange, and rhodamine B dyes appear as the most investigated in studies involving photocatalysis in the presence of ZnWO4. In our review, we summarize important literature works, highlighting the advancement in photocatalysis using ZnWO4.

The Influence of Synthesis Methods and Experimental Conditions on the Photocatalytic Properties of SnO2: A Review

Semiconductors based on transition metal oxides represent an important class of materials used in emerging technologies. For this, the performance of these materials strongly depends on the size and morphology of particles, surface charge characteristics, and the presence of bulk and surface defects that are influenced by the synthesis method and the experimental conditions the materials are prepared. In this context, the present review aims to report the importance of choosing the synthesis methods and experimental conditions to modify structural, morphological, and electronic characteristics of semiconductors, more specifically, tin oxide (SnO2), since these parameters may be a determinant for better performance in various applications, including photocatalysis. SnO2 is an n-type semiconductor with a band gap between 3.6 and 4.0 eV, whose intrinsic characteristics are responsible for its electrical conductivity, good optical characteristics, high thermal stability, and other qualities. Such characteristics have provided excellent results in advanced oxidative processes, i.e., heterogeneous photocatalysis applications. This process involves semiconductors in the production of hydroxyl radicals via activation by light absorption, and it is considered as an emerging and promising technology for domestic-industrial wastewater treatment. In our review article, we focused on the photodegradation of different organic dyes and types of persistent organic pollutants using SnO2-based photocatalysts, and how the efficiency of these materials can be impacted by synthesis methods and experimental conditions employed to prepare them.

Sustainable Green Nanotechnologies for Innovative Purifications of Water: Synthesis of the Nanoparticles from Renewable Sources.

Polluting the natural water resources is a serious global issue, which is confirmed by the fact that today at least 2 billion people consume water from contaminated sources. The conventional wastewater treatment methods cannot effectively remove the persistent pollutants (e.g., drugs, organic dyes, pesticides) from the aqueous environment. Heterogeneous photocatalysis is a promising and sustainable alternative for water remediation. It is based on the interaction between light irradiation and the semiconductors (e.g., TiO2, ZnO) as photocatalysts, but these compounds, unfortunately, have some disadvantages. Hence, great attention has been paid to the nanotechnology as a possible way of improvement. Nanomaterials have extraordinary properties; however, their conventional synthesis is often difficult and requires a significant amount of dangerous chemicals. This concise topical review gives recent updates and trends in development of sustainable and green pathways in the synthesis of nanomaterials, as well as in their application for water remediation. In our review we put emphasis on the eco-friendly, mostly plant extract-based materials. The importance of this topic, including this study as well, is proved by the growing number of publications since 2018. Due to the current serious environmental issues (e.g., global warming, shortage of pure and quality water), it is necessary for the traditional TiO2 and ZnO semiconductors to be replaced with the harmless, non-toxic, and more powerful nanocomposites as photocatalysts. Not only because of their higher efficiency as compared to the bulk semiconductors, but also because of the presence of biomolecules that can add up to the pollutant removal efficiency, which has been already confirmed in many researches. However, despite the fact that the application of heterogeneous photocatalysis together with green nanotechnology is absolutely the future in water purification, there are some challenges which have to be overcome. The exact effects of the biomolecules obtained from plants in the synthesis of nanoparticles, as well as in the photocatalytic processes, are not exactly known and require further investigation. Furthermore, heterogeneous photocatalysis is a well-known and commonly examined process; however, its practical use outside the laboratory is expensive and difficult. Thus, it has to be simplified and improved in order to be available for everyone. The aim of our review is to suggest and prove that using these bio-inspired compounds it is possible to reduce human footprint in the nature.

Enhanced photocatalytic activity of cobalt-doped titanate nanotube heterostructures decorated with Cu2O-CuO nanoparticles for organic pollutant degradation under UV and visible irradiation

In this work, Co-doped titanate nanotubes decorated with Cu2O/CuO nanoparticle heterostructures (TNTs-Co-Cu) were successfully synthesized by hydrothermal method followed by an impregnation method. The photocatalysts were characterized by TEM, XRD, Raman spectroscopy, XPS, N2 adsorption/desorption, DRS, and Photoluminescence. The results confirm the success of the TNTs-Co-Cu heterojunctions synthesis and the excellent absorption exhibited in the visible light region. Furthermore, the photocatalytic activity of the TNTs-Co-Cu materials was higher than that of pure titanate nanotubes (TNTs) and doped with cobalt (TNTs-Co) for Methyl Blue (MB) photodegradation under UV and visible light irradiation. The improved photocatalytic activity may can explained due to the increased the lifetime of photogenerated electron/hole pairs. The photocatalytic mechanism study suggested that the photogenerated electrons in conduction band (CB) of the Cu2O flow through the CuO CB to CB of TNTs-Co, whereas the photogenerated holes migrate in the opposite direction. These transfers result in the production of O2– and OH radicals to promote the photooxidation reaction of MB. This study provides the understanding on the heterojunction mechanism of the MB photodegradation by TNTs-Co-Cu under UV irradiation and shows their high photocatalytic activity after 5 cycles, which make the TNTs-Co-Cu a promising photocatalyst for the multifunctional heterogeneous photocatalysis applications.

Photochemical transformation of fentanyl under the simulated solar radiation – Enhancement of the process by heterogeneous photocatalysis and in silico analysis of toxicity

In this study the photochemical transformation of fentanyl—a very potent opioid drug—under simulated solar radiation was investigated for the first time. This pharmaceutical is frequently detected in various environment samples at concentrations that should be regarded as potentially harmful. Nevertheless, to date, no drug phototransformation products (TPs) have been reported. Considering fentanyl's exceptionally high toxicity, knowledge of the properties of these potential TPs is essential in order to properly assess its pollution impact. In this study, all photolytic experiments were performed using a xenon lamp (D65 filter) and RP-UHPLC coupled with the ESI-high-resolution tandem mass spectrometry. The phototransformation of fentanyl in natural river water and the application of heterogeneous photocatalysis as a possible way of decontaminating water were also investigated. Fentanyl turned out to be photostable, but twenty-six previously unreported TPs (formed mainly as a consequence of hydroxylation and oxidation) were found and characterized. The applied catalysts—TiO2 and ZnO—showed very high effectiveness, and the presence of the natural water matrix further increased the photodecomposition rate (up to 600 times) relative to direct photolysis. Importantly, the almost complete degradation of the parent compound as well as its TPs after 16 min of irradiation indicated that heterogeneous photocatalysis can be considered an efficient way of treatment of fentanyl-contaminated water. The computational analysis of toxicity showed that fentanyl may be more harmful to rodents and aquatic species than its TPs. However, some of these products are probably more mutagenic and developmentally toxic. Additionally, one product in particular may be a strong estrogenic compound, proving the importance of assessing TPs' toxic properties. The evaluation of bioaccumulation, bioconcentration and biodegradability revealed that fentanyl possesses unfavorable properties compared to TPs.

Factors influencing the adsorption and photocatalysis of direct red 80 in the presence of a TiO2: Equilibrium and kinetics modeling

Among the different photocatalysts, TiO2 ( Eg = 3.1 eV, zero charge point (pHpzc = 6.3), and surface = 55 m2/g) is currently the most efficient and the most studied semiconductor due to its strong photocatalytic activity, non-toxicity, and chemical stability. The elimination of DR-80 on TiO2 is studied by adsorption in batch mode and by application of heterogeneous photocatalysis onto TiO2 under UV irradiation. The effects of contact time (0–60 min), initial pH (3–11), dose of the adsorbent (0.5–3 g L−1), and DR-80 concentration (40–60 mg L−1) on the adsorption of DR-80 by TiO2 are studied for optimization of these parameters. The kinetic parameters, rate constants, and equilibrium adsorption capacities are calculated and discussed for each applied theoretical model. The adsorption of DR-80 is well described by the pseudo-first-order kinetic model. The fitting of the adsorption isotherms shows that the models of Langmuir and Temkin offering a better fit and an adsorption 64.102 mg/g at 25 °C of DR-80 are eliminated. The results showed that the photocatalytic efficiency strongly depends on the pH while the initial rate of photodegradation is proportional to the catalyst dose, and becomes almost constant above a threshold value. It was found that the photodegradation is favored at low DR-80 concentrations in accordance with the Langmuir–Hinshelwood model with the constants Kad = 6.5274 L/mg and KL–H = 0.17818 mg L−1 min. However, the adsorption is improved for high DR-80 concentrations. It is found that the degradation depends on both the temperature and the pH with a high elimination rate at high temperature. The photocatalyst TiO2 has a better activity for the degradation of DR-80, compared to some commercial catalysts that have been described in the literature.

Single Copper Atoms Enhance Photoconductivity in g-C3N4.

Graphitic carbon nitride (g-C3N4) and its doped analogues have been studied over the past decade in part due to their promising applications in heterogeneous photocatalysis; however, the effect of doping on the photoconductivity is poorly understood. Herein, we investigate Cu doped g-C3N4 (Cu-g-C3N4) and demonstrate via extended X-ray absorption fine structure that Cu+ incorporates as an individual ion. Time-resolved optical pump terahertz probe spectroscopy was utilized to measure the ultrafast photoconductivity in response to a 400 nm pump pulse and showed that the Cu+ dopant significantly enhances photoconductivity of the as-prepared powdered sample, which decays within 10 ps. Furthermore, a film preparation technique was applied that further enhanced the photoconductivity and induced a longer-lived photoconductive state with a lifetime on the order of 100 ps. This study provides valuable insight into the ultrafast photoconductivity dynamics of g-C3N4 materials, which is essential toward developing efficient g-C3N4 photocatalysts.

Floating Photocatalysts for Effluent Refinement Based on Stable Pickering Cellulose Foams and Graphitic Carbon Nitride (g-C3N4).

The transfer of heterogeneous photocatalysis applications from the laboratory to real-life aqueous systems is challenging due to the higher density of photocatalysts compared to water, light attenuation effects in water, complicated recovery protocols, and metal pollution from metal-based photocatalysts. In this work, we overcome these obstacles by developing a buoyant Pickering photocatalyst carrier based on green cellulose nanofibers (CNFs) derived from wood. The air bubbles in the carrier were stable because the particle surfactants provided thermodynamic stability and the derived photocatalytic foams floated on water throughout the test period (4 weeks). A metal-free semiconductor photocatalyst, g-C3N4, was facilely embedded inside the foam by mixing the photocatalyst with the air-bubble suspension followed by casting and drying to produce solid foams. When tested under mild irradiation conditions (visible light, low energy LEDs) and no agitation, almost three times more dye was removed after 6 h for the floating g-C3N4–CNF nanocomposite foam, compared to the pure g-C3N4 powder residing on the bottom of a ca. 2 cm-high water pillar. The buoyancy and physicochemical properties of the carrier material were imperative to render escalated oxygenation, high photon utilization, and faster dye degradation. The reported assembly protocol is facile, general, and provides a new strategy for assembling green floating foams that can potentially carry a number of different photocatalysts.

Photocatalysis Meets Magnetism: Designing Magnetically Recoverable Supports for Visible-Light Photocatalysis.

While magnetic supports have been widely used to immobilize homogeneous catalysts in organic chemistry, this strategy has so far found very little application in photocatalysis. Indeed, magnetic supports are dark colored, and thus compete for photon absorption with photocatalysts themselves. We have developed a series of core-shell Fe(0)-silica nanoparticles as supports for immobilizing the photosensitizer Ru(bpy)32+, featuring various silica shell thicknesses-16-34 nm SiO2-on 9 nm Fe cores. The supports and the resulting photocatalytic systems were studied for their magnetic, optical, and catalytic properties in the context of the photooxidation of citronellol, and we found that thicker silica shells lead to higher catalytic activity. We correlated this effect as well as Ru(bpy)32+ fluorescence and singlet oxygen generation to the absorption properties of the supports. We were able to reuse our optimal system three times with minimal loss of activity and achieved turnover numbers largely surpassing the performance of homogeneous Ru(bpy)32+. This work highlights the role of material design in the conception of new supports for applications in heterogeneous photocatalysis.

Limitations and Prospects for Wastewater Treatment by UV and Visible-Light-Active Heterogeneous Photocatalysis: A Critical Review.

Heterogeneous photocatalysis (HPC) has been widely investigated in recent decades for the removal of a number of contaminants from aqueous matrices, but its application in real wastewater treatment at full scale is still scarce. Indeed, process and technological limitations have made HPC uncompetitive with respect to consolidated processes/technologies so far. In this manuscript, these issues are critically discussed and reviewed with the aim of providing the reader with a realistic picture of the prospective application of HPC in wastewater treatment. Accordingly, consolidated and new photocatalysts (among which the visible active ones are attracting increasing interest among the scientific community), along with preparation methods, are reviewed to understand whether, with increased process efficiency, these methods can be realistically and competitively developed at industrial scale. Precipitation is considered as an attractive method for photocatalyst preparation at the industrial scale; sol-gel and ultrasound may be feasible only if no expensive metal precursor is used, while hydrothermal and solution combustion synthesis are expected to be difficult (expensive) to scale up. The application of HPC in urban and industrial wastewater treatment and possible energy recovery by hydrogen production are discussed in terms of current limitations and future prospects. Despite the fact that HPC has been studied for the removal of pollutants in aqueous matrices for two decades, its use in wastewater treatment is still at a "technological research" stage. In order to accelerate the adoption of HPC at full scale, it is advisable to focus on investigations under real conditions and on developing/improving pilot-scale reactors to better investigate scale-up conditions and the potential to successfully address specific challenges in wastewater treatment through HPC. In realistic terms, the prospective use of HPC is more likely as a tertiary treatment of wastewater, particularly if more stringent regulations come into force, than as pretreatment for industrial wastewater to improve biodegradability.

2D/2D Wg-C3N4/g-C3N4 composite as “Adsorb and Shuttle” model photocatalyst for pollution mitigation

Semiconductor mediated photodegradation of dyes is an important application of heterogeneous photocatalysis. Frequently, transitional metal oxides, sulfides and oxometallate photocatalyst are accentuated in pollutants degradation burdening the cost and secondary pollution of metal leaching. In this work, a metal-free 2D/2D photocatalyst is built by pristine g-C3N4; supported on the acid-treated protonic white g-C3N4 substrate for concurrent high adsorption and excellent visible light absorption as “Adsorb & Shuttle (A&S)” model photocatalyst. Herein, oxidized white g-C3N4 provides excess active sites for binding of dye molecules through adsorption and delivers it to photoactive g-C3N4 sites by surface diffusion, while g-C3N4 degrades the organic pollutants by releasing strong reactive oxidative species (ROS). The formation of face-to-face matching 2D/2D Van der Waal’s (vdW) type homojunction reduced exciton recombination and improved photoactivity. The current A&S strategy may provide new insights into the rational design of g-C3N4 based adsorption induced photocatalysts for effective and rapid decomposition of organic pollutants.

Evaluation of the Structural, Photonic and Morphologic Effects Caused by Zinc Doping in the Titanium Dioxide Powder Samples Obtained by Sol-Gel Method

The anatase phase of titanium dioxide ceramic material plays important rule in heterogeneous photocatalysis, beside the global phase amount and powder morphology. Some of structural parameters are useful to predict several properties, including the crystallization process and mechanism of the irreversible anatase-to-rutile phase transition. The photocatalytic process is based on charge transference from electron-hole pair to material surface, starting some redox reactions in aqueous media. The stable positive defects harm the recombination event and improve the final properties of that material. Modifiers with lower oxidation state than titanium (IV) is applicable for this purpose, what idea becomes the objective of this work. The Sol-Gel method was used to prepare bare and zinc doped-titanium dioxide powder samples reaching good compositional homogeneity for both samples calcined at 500 oC for 4 hours. Rietveld refinement carried out from raw x-ray diffraction patterns was used to demonstrate the formation of solid solution between zinc and titanium oxides. Besides that result, the determination of bandgap energy and SEM images corroborated the structural changes caused by zinc insertion in anatase phase and important difference in powder morphology was observed for zinc doped powder samples in order to reduce the agglomeration degree for better performance for heterogeneous photocatalysis applications.

ADMI color and toxicity reductions in raw textile mill effluent and dye mixtures by TiO2/UV is limited by presence of vat dyes.

Full-scale application of heterogeneous photocatalysis for industrial wastewater treatment remains a challenge because of the complex nature of these matrices and the potential to form toxic by-products during treatment. A recent unsuccessful attempt to find adequate conditions for TiO2/UV treatment of a cotton dyeing textile mill led to this study on the treatability of mixtures of the dyes used in the greatest amounts at the mill and therefore most likely to be present in mill effluent. Four reactive and three vat dyes were mixed in different combinations and treated (10mg/L of each dye, 0.5mg/L TiO2, pH4) to evaluate the influence of the different dyes on ADMI color, chemical oxygen demand (COD), and acute toxicity. While ADMI color removal was similar in all dye mixtures, COD removal was higher when vat dyes were absent. When treated individually, vat dyes exhibited greater recalcitrance, with no ADMI color removal and COD removals of less than 30%. Toxicity to Daphnia similis was decreased or eliminated from dye mixtures that exhibited the highest COD removals and corresponded to those in which reactive dyes were partially degraded. For raw textile mill effluent, photocatalysis reduced but did not eliminate treated effluent toxicity (EC50 = 26.8%).

Removal of contaminants of emerging concern (CECs) and antibiotic resistant bacteria in urban wastewater using UVA/TiO2/H2O2 photocatalysis

The dispersion of pollutants and proliferation of antibiotic resistant bacteria in the aquatic environment are an emerging health concern worldwide. In this sense, it is essential to develop new technologies to increase the quality of wastewater treatment, which is spread throughout the environment. The present study has demonstrated evidence of the existence of antibiotic and mercury-resistant bacteria in the aquatic environment. The application of heterogeneous photocatalysis with UVA/TiO2 P25 slurry (200 mg L−1), UVA/TiO2-immobilized, and UVA/TiO2-immobilized/H2O2 were evaluated for the simultaneous elimination of a mixture of contaminants of emerging concern (acetamiprid (ACP), imazalil (IMZ) and bisphenol A (BPA)) and inactivation of antibiotic and mercury-resistant bacteria (Pseudomonas aeruginosa and Bacillus subtilis). UVA/TiO2-immobilized/H2O2 increased the inactivation and elimination of the contaminants. After the combined treatment, the mixture of BPA, IMZ and ACP decreased 62%, 21% and <5%, respectively, after 300 min at 13.10 kJ L−1 of accumulated UV energy. The Pseudomonas aeruginosa strain was inactivated after 120 min using 5.24 kJ L−1 of accumulated UV energy, whereas the Bacillus subtilis strain was shown to be extremely resistant, with a capacity to develop mechanisms to avoid the oxidation process.

Heteroatom‐Doped Carbonaceous Photocatalysts for Solar Fuel Production and Environmental Remediation

AbstractPhotocatalytic solar energy conversion and environmental remediation including water splitting, CO2 reduction, and pollutant degradation have attracted rapidly growing attention, owing to global fossil fuel depletion and increasing environmental issues. From the viewpoint of the broad availability, good environmental acceptability, high corrosion resistance, as well as the readily tailorable microstructure, electronic structure and surface chemical properties, carbonaceous materials have been demonstrated as promising and sustainable low‐cost metal‐free alternatives to metal‐based photocatalysts for solar fuel production and pollutant degradation. The non‐metallic heteroatoms doping approach has been considered as a powerful tool for modulating electronic structure, morphology, surface structure and surface chemistry, textural properties, optical properties, and electrochemical properties, as well as catalytic properties of carbonaceous photocatalysts. This Review represents a comprehensive overview of the latest advance in preparation and physicochemical properties of diverse non‐metallic heteroatoms‐doped carbonaceous materials, as well as their applications in heterogeneous photocatalysis towards solar energy conversion and environmental remediation. The physicochemical properties and photocatalytic performance of the carbonaceous photocatalysts are carefully compared, as well as a brief overview of fundamental principles for the promoting effect of heteroatoms‐doping is also presented. In addition, the future perspectives on the opportunities and challenges of heteroatoms doping for fabricating novel and excellent carbonaceous photocatalysts are outlined.