Photocatalytic activity of CuO nanoparticles for organic and inorganic pollutants removal in wastewater remediation

Facile green synthesis of novel tantalum doped tungsten trioxide for photocatalytic degradation: Correlation with COMSOL simulation

The facilegreen synthesis techniqueis becoming more and more important, and it has been proposed as a potential substitute for chemical techniques. The current study describes a low-cost, environmentally friendly method for producing tungsten trioxide (WO3) and tantalum (Ta) doped WO3nanoparticles that uses 15 % (w/v) Azadirachta indica (Neem) leaf extract and different concentrations of Ta dopant (1 to 5 %) due to its well-matched ionic radius with WO3. Various techniques FESEM, TEM, EDX, BET, UV-Vis and PL, XRD, and FTIR were used to illustrate the morphological, elemental, optical, structural, and vibrational analysis of the synthesized nanoparticles respectively. Interestingly, the band gap was significantly reduced to 1.88 eV by the addition of a dopant element. For 3 % Ta/WO3, the average particle size was also reduced to 31.6 nm. The synthesized WO3nanoparticles employed in the current study have been used for photocatalytic activitypurposes. Methylene blue (MB), one of the principal water pollutants, was degraded more quickly by the synthesized Ta/WO3nanoparticles when exposed to UV radiation. Among them, 3 % Ta/WO3 gives significantly higher photodegradation 89 % attributed to the Burstein-Moss effect. The significant output of optimized nano-photocatalyst has been observed from the trapping experiment and reusability test. Furthermore, Zeta potential and TOC analysis have been taken to check the stability and mineralization performance. Additionally, the results of the simulation that was carried out using the finite element analysis approach in the RF module of COMSOL Multiphysics 5.3a are quite similar to the experimental findings. This simulation method made it easier for readers to understand the numerous aspects of the photocatalytic process that has been discussed here.

Transition metals-doped g-C3N4 nanostructures as advanced photocatalysts for energy and environmental applications

Graphitic carbon nitride (g-C3N4)-based heterostructured photocatalysts have received significant attention for its potential applications in the treatment of wastewater and hydrogen evolution. The utilization of semiconductor materials in heterogeneous photocatalysis has recently received great attention due to their potential and eco-friendly properties. Doping with metal ions plays a crucial role in altering the photochemical characteristics of g-C3N4, effectively enhancing photoabsorption into the visible range and thus improving the photocatalytic performance of doped photocatalysts. As an emerging nanomaterial, nanostructured g-C3N4 represents a visible light-active semiconducting photocatalyst that has attracted significant interest in the photocatalysis field, particularly for its practical water treatment applications. To the best of our knowledge, investigations of functionalized photocatalytic (PC) materials on 3d transition metal-doped g-C3N4 remain unexplored in the existing literature. g-C3N4 based heterohybrid photocatalysts have demonstrated excellent reusability, making them highly promising for wastewater treatment applications. This paper describes the overview of numerous studies conducted on the heterostructured g-C3N4 photocatalysts with various 3d metals. Research studies have revealed that the introduction of element doping with various 3d transition metals (e.g., Ti, Mn, Fe, Co, Ni, Cu, Zn, etc.) into g-C3N4 is an efficient approach to enhance degradation efficacy and boost photocatalytic activity (PCA) of doped g-C3N4 catalysts. Moreover, the significance of g-C3N4 heterostructured nanohybrids is highlighted, particularly in the context of wastewater treatment applications. The study concludes by providing insights into future perspectives in this developing area of research, with a specific focus on the degradation of various organic contaminants.

Recent advances and new insights on the construction of photocatalytic systems for environmental disinfection

Photocatalysis, as a sustainable and environmentally friendly green technology, has garnered widespread recognition and application across various fields. Especially its potential in environmental disinfection has been highly valued by researchers. This study commences with foundational research on photocatalytic disinfection technology and provides a comprehensive overview of its current developmental status. It elucidates the complexity of the interface reaction mechanism between photocatalysts and microorganisms, providing valuable insights from the perspectives of materials and microorganisms. This study reviews the latest design and modification strategies (Build heterojunction, defect engineering, and heteroatom doping) for photocatalysts in environmental disinfection. Moreover, this study investigates the research focuses and links in constructing photocatalytic disinfection systems, including photochemical reactors, light sources, and material immobilization technologies. It studies the complex challenges and influencing factors generated by different environmental media during the disinfection process. Simultaneously, a comprehensive review extensively covers the research status of photocatalytic disinfection concerning bacteria, fungi, and viruses. It reveals the observable efficiency differences caused by the microstructure of microorganisms during photocatalytic reactions. Based on these influencing factors, the economy and effectiveness of photocatalytic disinfection systems are analyzed and discussed. Finally, this study summarizes the current application status of photocatalytic disinfection products. The challenges faced by the synthesis and application of future photocatalysts are proposed, and the future development in this field is discussed. The potential for research and innovation has been further emphasized, with the core on improving efficiency, reducing costs, and strengthening the practical application of photocatalysis in environmental disinfection.

Fabrication of ternary metal oxide (ZnO:NiO:CuO) nanocomposite heterojunctions for enhanced photocatalytic and antibacterial applications

In this article, ZnO:NiO:CuO nanocomposites (NCPs) were synthesized using a hydrothermal method, with different Zn : Ni : Cu molar ratios (1 : 1 : 1, 2 : 1 : 1, 1 : 2 : 1, and 1 : 1 : 1). The PXRD confirmed the formation of a NCP consisting of ZnO (hexagonal), NiO (cubic), and CuO (monoclinic) structures. The crystallite sizes of NCPs were calculated using Debye Scherrer and Williamson-Hall methods. The calculated crystalline sizes (Scherrer method) of the NCPs were determined to be 21, 27, 23, and 20 nm for the molar ratios 1 : 1 : 1, 2 : 1 : 1, 1 : 2 : 1, and 1 : 1 : 2, respectively. FTIR spectra confirmed the successful formation of heterojunction NCPs via the presence of metal-oxygen bonds. The UV-vis spectroscopy was used to calculate the bandgap of synthesized samples and was found in the range of 2.99-2.17 eV. SEM images showed the mixed morphology of NCPs i.e., irregular spherical and rod-like structures. The dielectric properties, including AC conductivity, dielectric constant, impedance, and dielectric loss parameters were measured using an LCR meter. The DC electrical measurements revealed that NCPs have a high electrical conductivity. All the NCPs were evaluated for the photocatalytic degradation of Methylene blue (MB), methyl orange (MO), and a mixture of both of these dyes. The NCPs with a molar ratio 1 : 1 : 2 (Zn : Ni : Cu) displayed outstanding photocatalytic activity under sunlight, achieving the degradation efficiency of 98% for methylene blue (MB), 92% for methyl orange (MO) and more than 87% in the case of a mixture of dyes within just 90 minutes of illumination. The antibacterial activity results showed the more noxious nature of NCPs against Gram-negative bacteria with a maximum zone of inhibition revealed by the NCPs of molar ratio 1 : 2 : 1 (Zn : Ni : Cu). On the basis of these observations, it can be anticipated that the NCPs can be successfully employed for the purification of contaminated water by the degradation of hazardous organic compounds and in antibacterial ointments.

Relevance of photocatalytic redox transformations of selected pharmaceuticals in a copper- and iron-rich Mediterranean intermittent river

This work aimed at investigating specific attenuation pathways of pharmaceuticals in copper- and iron-rich Mediterranean intermittent and sunlit rivers by combining lab- and field-scale studies. Poorly photodegradable and biodegradable compounds such as fluconazole, oxazepam and venlafaxine attenuated in two river stretches with short hydraulic residence times (<3 h). This result was assumed to be related to their capacity to interact with photoreactive free Cu2+ and Fe3+ or their associated oxides. Lab-scale photodegradation experiments under simulated solar irradiation revealed the beneficial impact of a mixture Cu2+ and colloidal iron hydroxides at environmental concentrations and at neutral pH on the pharmaceuticals photodegradation kinetic rate constants. These latter were consistent with the in-stream attenuation rate constants of targeted contaminants which ranged from 0.104 to 0.154 h-1. Further identification of phototransformation products by LC-HRMS highlighted reductive transformation pathways including reductive dehalogenation and hydrogenation reactions. Several TPs were found to be stable under irradiation and were detected in field monitoring, accordingly. This was ascribed to the formation of a Cu/Fe composite material under solar irradiation with photocatalytic properties. The role of Cu was to trap the electron in the conduction band of the iron-based photocatalyst, which promoted separation efficiency of electron-hole pairs as well as enhanced photoreduction processes at the expense of oxidation ones. Even though, these mechanisms have been reported in water treatment field for organic micropollutants removal, their significance was demonstrated for the first time in natural settings.

Exploring Copper Oxide and Copper Sulfide for Non-Enzymatic Glucose Sensors: Current Progress and Future Directions

Millions of people worldwide are affected by diabetes, a chronic disease that continuously grows due to abnormal glucose concentration levels present in the blood. Monitoring blood glucose concentrations is therefore an essential diabetes indicator to aid in the management of the disease. Enzymatic electrochemical glucose sensors presently account for the bulk of glucose sensors on the market. However, their disadvantages are that they are expensive and dependent on environmental conditions, hence affecting their performance and sensitivity. To meet the increasing demand, non-enzymatic glucose sensors based on chemically modified electrodes for the direct electrocatalytic oxidation of glucose are a good alternative to the costly enzymatic-based sensors currently on the market, and the research thereof continues to grow. Nanotechnology-based biosensors have been explored for their electronic and mechanical properties, resulting in enhanced biological signaling through the direct oxidation of glucose. Copper oxide and copper sulfide exhibit attractive attributes for sensor applications, due to their non-toxic nature, abundance, and unique properties. Thus, in this review, copper oxide and copper sulfide-based materials are evaluated based on their chemical structure, morphology, and fast electron mobility as suitable electrode materials for non-enzymatic glucose sensors. The review highlights the present challenges of non-enzymatic glucose sensors that have limited their deployment into the market.

Photocatalytic degradation of imidacloprid using Ag2O/CuO composites

Imidacloprid is one of the most commonly used neonicotinoid pesticides that has been identified as a neurotoxin for various non-target organisms. It binds to the central nervous system of organisms, causing paralysis and eventually death. Thus, it is imperative to treat waterwaters contaminated with imidacloprid using an efficient and cost effective method. The present study presents Ag₂O/CuO composites as excellent catalysts for the photocatalytic degradation of imidacloprid. The Ag₂O/CuO composites were prepared in different compositions by adopting the co-precipitation method and used as a catalyst for the degradation of imidacloprid. The degradation process was monitored using UV-vis spectroscopy. The composition, structure, and morphologies of the composites were determined by FT-IR, XRD, TGA, and SEM analyses. The effect of different parameters i.e time, concentration of pesticide, concentration of catalyst, pH, and temperature on the degradation was studied under UV irradiation and dark conditions. The results of the study evidenced the 92.3% degradation of imidacloprid in only 180 minutes, which was 19.25 hours under natural conditions. The degradation followed first-order kinetics, with the half life of the pesticide being 3.7 hours. Thus, the Ag₂O/CuO composite was an excellent cost-effective catalyst. The non-toxic nature of the material adds further benefits to its use. The stability of the catalyst and its reusability for consecutive cycles make it more cost effective. The use of this material may help to ensure an immidacloprid free environment with minimal use of resources. Moreover, the potential of this material to degrade other environmental pollutants may also be explored.

Synthesis and characterization of visible-light-driven novel CuTa2O6 as a promising practical photocatalyst

In this work, the novel CuTa₂O₆ phase was successfully synthesized by the hydrothermal and followed by the calcination process. The X-ray diffraction pattern confirms the formation of different phases. At a low temperature, CuTa₂O₆ exhibits the orthorhombic phase, whereas, at a higher temperature, it underwent a phase transition to a cubic crystal structure. X-ray photoelectron spectroscopic results suggest the presence of all the elements (Cu, Ta, and O). The optical studies were carried out using a UV-Vis DRS spectrophotometer. FESEM images confirm the spherical-shaped particles for the sample annealed at a high temperature. The local atomic and electronic structures around Cu and the contribution of the Cu oxidation state in the CuTa₂O₆ system were determined by X-ray absorption spectroscopy. To investigate the effective usage of CuTa₂O₆ in treating wastewater, its photocatalytic activity was investigated by evaluating its use in the photodegradation of MO dye under visible light irradiation. Moreover, the prepared CuTa₂O₆ photocatalyst exhibits significant photocatalytic activity in the degradation of MO dye and shows excellent stability; it is therefore a promising material for potential use in a practical photocatalyst. The CuTa₂O₆ photocatalyst suggests an alternative avenue of research into effective photo-catalysts for solar hydrogen water splitting.

Photocatalytic Performance and Kinetic Studies of a Wood Surface Loaded with Bi2O3-Doped Silicon-Titanium Composite Film

In this paper, a surface self-cleaning wood was obtained by loading Bi₂O₃-doped silica-titanium composite film on the surface of wood by the sol-gel method. The effects of different Bi doping amounts on the structure and photocatalytic properties of the modified wood were investigated. The doping of Bi₂O₃ inhibited the growth of TiO₂ crystals and the phase transition from anatase to rutile. In addition, Bi₂O₃ could improve the photocatalytic activity of the composite film by appropriately reducing the grain size of TiO₂ and increasing the crystallinity of TiO₂. Furthermore, doping with Bi₂O₃ shifted the absorption wavelength of the wood samples back into the visible range, indicating that the increase in Bi content favoured light absorption. The wood samples loaded with Bi₂O₃-doped Si-Ti composite membranes had the best photocatalytic activity and the highest reaction rate when n (Ti):n (Bi) = 1:0.015. Degradation rates of 96.0% and 94.0% could be achieved for rhodamine B and gaseous formaldehyde, respectively. It can be seen that wood samples loaded with Bi₂O₃-doped Si-Ti composite films on the surface exhibit excellent photocatalytic activity against both gaseous and liquid pollutants.

Effect of the green synthesis of CuO plate-like nanoparticles on their photodegradation and antibacterial activities

Green synthesis of copper oxide nanoparticles and its effects on photocatalytic dye degradation and antibacterial activities are reported. The synthesis of nanoparticles by green routes provides many advantages over chemical routes, including simplicity, cost-effectiveness, and fast processing route without using any costly or harmful chemicals. Tridax procumbense (coat buttons) plant root extract was used to synthesize copper oxide nanoparticles. The synthesized Tridax procumbense-copper oxide nanoparticles (TP-CuO NPs) were characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering spectroscopy (DLS), and X-ray diffraction (XRD) techniques. The synthesized TP-CuO NPs were applied for photocatalytic dye degradation and antibacterial activity studies. The TP-CuO NPs exhibited a maximum antibacterial activity at 500 μg mL^-1 concentration against Staphylococcus aureus and E. coli showing inhibition zones of 7.5 mm and 7.2 mm, respectively. The photocatalytic ability of the TP-CuO was also tested against the textile dye Trypan blue (TB), and showed about 55% degradation after 48 h for 500 μg mL^-1 CuO NP concentration, showing a concentration-dependent degradation efficiency. This is the first work on TP-derived CuO nanoparticles and their photocatalytic and antimicrobial applications. Overall, this study supports the superiority of green-synthesized TP-CuO NPs as photocatalytic and antimicrobial agents.

Photocatalytic and Electrochemical Activity of Magnesium Oxide Nanoballs Synthesized via a Hydrothermal Route

Currently, there is growing concern about minimizing the environmental impacts caused by the generation of waste on water, soil, air pollution, and contamination of the environment in general. Magnesium oxide (MgO) nanoballs (NBs) were synthesized by the hydrothermal method followed by a calcination process. The average size of particles dispersed in deionized water was 159.2 ± 70 nm. The energy band gap was calculated to be 5.14 eV. The magnetic behavior, cyclic voltammetry, and electrochemical impedance of MgO NBs were studied. Under visible-light irradiation, the photocatalytic activity of MgO nanoballs was investigated by methylene blue (MB) dye. Results showed that photodegradation for MB under visible light irradiation for 120 min and degradation results are fitted well with pseudo-first-order reaction kinetics with a rate constant of 0.00252 min−1 and a correlation coefficient of 0.96.

Effects of methanol, sodium citrate, and chlorella powder on enhanced anaerobic treatment of coal pyrolysis wastewater

To better promote environment friendly development of the coal chemical industry, this study investigated effects of methanol, sodium citrate, and chlorella powder (a type of microalgae) as co-metabolic substances on enhanced anaerobic treatment of coal pyrolysis wastewater with anaerobic sludge. The anaerobic sludge was loaded into four 2 L anaerobic reactors for co-metabolism enhanced anaerobic experiments. Anaerobic reactor 1 (R1) as control group did not add a co-metabolic substance; anaerobic reactor 2 (R2) added methanol; anaerobic reactor 3 (R3) added sodium citrate; and anaerobic reactor 4 (R4) added chlorella powder. In the blank control group, the removal ratios of total phenol (TPh), quinoline, and indole were only 12.07%, 42.15%, and 50.47%, respectively, indicating that 50 mg/L quinoline, 50 mg/L indole, and 600 mg/L TPh produced strong toxicity inhibition function on the anaerobic microorganism in reactor. When the concentration of methanol, sodium citrate, and chlorella was 400 μg/L, the reactors with co-metabolic substances had better treatment effect on TPh. Among them, the strengthening effects of sodium citrate (TPh removal ratio: 44.87%) and chlorella (47.85%) were better than that of methanol (38.72%) and the control group (10.62%). Additionally, the reactors with co-metabolic substances had higher degradation ratios on quinoline, indole, and chemical oxygen demand (COD). The data of extracellular polymeric substances showed that with the co-metabolic substances, anaerobic microorganisms produced more humic acids by degrading phenols and nitrogen-containing heterocyclic compounds (NHCs). Compared with the control group, the reactors added with sodium citrate and chlorella had larger average particle size of sludge. Thus, sodium citrate and chlorella could improve sludge sedimentation performance by increasing the sludge particle size. The bacterial community structures of reactors were explored and the results showed that Aminicenantes genera incertae sedis, Levinea, Geobacter, Smithella, Brachymonas, and Longilinea were the main functional bacteria in reactor added with chlorella.

Photocatalytic Efficiency of Titanium Dioxide for Dyes and Heavy Metals Removal from Wastewater

The hazardous toxicity of dye materials, even in low concentrations, harms ecological systems. It releases a large number of contaminants into the water, resulting as waste water. Dyes prevent the process of photosynthesis by obstructing light passage, lowers the oxygen levels dissolved in the water. Also, a good number of the dyes and heavy metals are carcinogenic and mutagenic to human beings. Heterogeneous photocatalysis is a promising technology for removing organic, inorganic, and microbial pollutants from water and wastewater. It is preferable to other conventional wastewater treatment approaches due to its benefit, such as low cost, environmental friendliness, ability to proceed at ambient temperature and pressure conditions, and to completely degrade pollutants into environmentally safe products with suitable measures. The titanium oxide (TiO2) is one of the most promising material that has gained enormous importance in the field of energy and environmental applications. The unique physicochemical properties of TiO2 make it one of the best candidates among existing photocatalysts. This review provides an overview of strategies employed to augment its catalytic performance as well as the impact of different operational parameters on the removal proficiency of various organic and inorganic pollutants in water and wastewater treatment. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Current Developments in the Effective Removal of Environmental Pollutants through Photocatalytic Degradation Using Nanomaterials

Photocatalysis plays a prominent role in the protection of the environment from recalcitrant pollutants by reducing hazardous wastes. Among the different methods of choice, photocatalysis mediated through nanomaterials is the most widely used and economical method for removing pollutants from wastewater. Recently, worldwide researchers focused their research on eco-friendly and sustainable environmental aspects. Wastewater contamination is one of the major threats coming from industrial processes, compared to other environmental issues. Much research is concerned with the advanced development of technology for treating wastewater discharged from various industries. Water treatment using photocatalysis is prominent because of its degradation capacity to convert pollutants into non-toxic biodegradable products. Photocatalysts are cheap, and are now emerging slowly in the research field. This review paper elaborates in detail on the metal oxides used as a nano photocatalysts in the various type of pollutant degradation. The progress of research into metal oxide nanoparticles, and their application as photocatalysts in organic pollutant degradation, were highlighted. As a final consideration, the challenges and future perspectives of photocatalysts were analyzed. The application of nano-based materials can be a new horizon in the use of photocatalysts in the near future for organic pollutant degradation.