Search Results (529)

Industrial and domestic effluents contaminated with synthetic dyes represent a significant global environmental and public health concern, necessitating the development of efficient, cost-effective, and sustainable wastewater treatment technologies. Among various remediation strategies, activated carbon (AC) has garnered considerable attention as an effective adsorbent, owing to its high surface area, excellent porosity, and strong adsorption capacity. This review presents a comprehensive analysis of activated carbon, with a particular focus on its derivation from bamboo biomass—a renewable, abundant, and low-cost precursor. It explores the key physicochemical characteristics of bamboo-based AC, common synthesis techniques, and the role of modification strategies—particularly metal oxide doping with TiO₂, ZnO, and MoS₂—in enhancing dye removal performance. The mechanisms underlying dye remediation, including adsorption and photocatalysis, as well as the synergistic effects observed in advanced AC-based composites, are critically examined. Emphasis is placed on the degradation of commonly used textile dyes such as methylene blue (MB), rhodamine B (RhB), and reactive blue, supported by comparative analyses of efficiency, stability, and reusability across various studies. Finally, the review outlines current challenges and knowledge gaps in the field, offering perspectives on future research directions to advance the development and large-scale application of sustainable bamboo-derived activated carbon composites for effective and eco-friendly wastewater purification. Full article

Emerging pollutants such as pharmaceuticals and synthetic dyes increasingly enter agricultural soils through irrigation with treated or untreated wastewater and via biosolid amendments, raising concerns for plant health, soil functionality, and food chain safety. Their environmental behavior is governed by complex interactions between compound physicochemistry, soil properties, and plant physiology, leading to variable persistence, mobility, and ecotoxicological outcomes. This review synthesizes current evidence on the fate, uptake, and phytotoxic effects of drug and dye contaminants in plant–soil systems, and provides a comparative assessment of ecological risks before and after photocatalytic wastewater treatment. The analysis integrates findings from soil- and hydroponic-based studies addressing pollutant sorption–desorption dynamics, leaching, microbial transformations, and plant responses ranging from germination impairment and biomass reduction to oxidative stress and genotoxicity. Special emphasis is given to the formation and behavior of transformation products generated during photocatalytic degradation, which may display altered mobility or toxicity relative to parent compounds. Comparative evaluation reveals that photocatalysis substantially reduces contaminant loads and toxicity in many cases, although incomplete mineralization or the formation of reactive intermediates can sustain or enhance adverse effects under certain conditions. By linking pollutant fate mechanisms with plant and soil responses, this review highlights both the potential and the limitations of photocatalysis as a sustainable strategy for safeguarding agroecosystems in the context of expanding wastewater reuse. Full article

High-valent metal species (iron, manganese, cobalt, copper, and ruthenium) based advanced oxidation processes (AOPs) have emerged as sustainable technologies for water remediation. These processes offer high selectivity, electron transfer efficiency, and compatibility with circular chemistry principles compared to conventional systems. This comprehensive review discusses recent advances in the synthesis, stabilization, and catalytic applications of high-valent metals in aqueous environments. This study highlights their dual functionality, not only as conventional oxidants but also as mechanistic mediators within redox cycles that underpin next-generation AOPs. In this review, the formation mechanisms of these species in various oxidant systems are critically evaluated, highlighting the significance of ligand design, supramolecular confinement, and single-atom engineering in enhancing their stability. The integration of high-valent metal-based AOPs into photocatalysis, sonocatalysis, and electrochemical regeneration is explored through a newly proposed classification framework, highlighting their potential in the development of energy efficient hybrid systems. In addition, this work addresses the critical yet underexplored area of environmental fate, elucidating the post-oxidation transformation pathways of high-valent species, with particular attention to their implications for metal recovery and nutrient valorization. This review highlights the potential of high-valent metal-based AOPs as a promising approach for zero wastewater treatment within circular economies. Future frontiers, including bioinspired catalyst design, machine learning-guided optimization, and closed loop reactor engineering, will bridge the gap between laboratory research and real-world applications. Full article

Titanium dioxide (TiO₂) nanoparticles (NPs) have garnered significant attention as photocatalysts for degrading organic pollutants, particularly synthetic dyes such as rhodamine B (RhB), methylene blue, methyl orange, and others. The impact of several synthesis methods, including sol–gel, hydrothermal, and chemical vapor deposition (CVD) techniques, on the electrical and morphological properties of TiO₂ NPs has been studied, emphasizing the distinctive physicochemical properties of TiO₂ NPs, including their extensive surface area, significant oxidative capacity, and remarkable chemical stability, which are important in the recent advancements in their use for RhB degradation. A detailed examination of TiO₂’s photocatalytic mechanism shows that it is based on the generation of reactive oxygen species (ROS) by photoinduced electron–hole pair formation under ultraviolet (UV) light exposure. In wastewater treatment, TiO₂ degrades RhB into less harmful byproducts by the generation of electron–hole pairs that initiate redox reactions under sunlight. This study includes a thorough overview of significant factors influencing photocatalytic efficacy. The parameters include particle size, crystal phase (anatase, rutile, and brookite), surface changes, and the incorporation of metal or non-metal dopants to enhance visible light absorption. Researchers continually seek methods to overcome challenges, including restricted visible-light responsiveness and rapid electron–hole recombination. The investigated approaches include heterojunction generation, composite development, and co-catalyst insertion. This review article aims to address the deficiencies in our understanding of TiO₂-based photocatalysis for the degradation of RhB and to propose enhancements for these systems to enable more efficient and sustainable wastewater treatment in the future. Full article

Titanium dioxide (TiO₂) nanoparticles (NPs) are useful as a potential photocatalyst for the degradation of dyes such as methyl orange, rhodamine B, and methylene blue (MB). Understanding the mechanism of photocatalysis and the factors influencing photocatalysis is important for engineering TiO₂ NPs to achieve an unprecedented photocatalysis rate. For TiO₂ NPs, their unique physicochemical qualities, such as small size, large surface area, optimum semiconductor bandgap, substantial oxidative potential, and outstanding chemical stability are factors which influence the MB degradation rate. The electron–hole pair separation in TiO₂ NPs allows for photocatalysis, which is not possible in their bulk form. The formation of reactive oxygen species (ROS) via photoinduced generation of electron–hole pairs under light irradiation is the starting point of the mechanism of photocatalysis for TiO₂ NPs. By generating ROS, TiO₂ NPs catalyze the degradation of MB. The photocatalytic performance of TiO₂ NPs is also different for different crystal phases, such as anatase, rutile, and brookite. The addition of metal or non-metal dopants into TiO₂ NPs enhances photocatalysis by enhancing light absorption, which enhances the generation of electron–hole pairs and of ROS. This review article will explain the mechanism of photocatalysis, the parameters influencing photocatalytic activity, active sites and recombination rates, disadvantages, and strategies to overcome these challenges that can improve TiO₂ NPs for a future wastewater treatment that is both efficient and sustainable. Full article

Mechanical energy is a plentiful, environmentally friendly, and sustainable energy source in the natural world. In this work, we successfully use friction to transform mechanical energy into ZnO and ZnO/Nd₂O₃ (1, 2, 3, 4 and 5 mol%) tribocatalysts. Under magnetic stirring, the catalyst particles and the polytetrafluoroethylene (PTFE)-sealed magnetic bar rubbed against one another, transferring electrons across the contact interface. While the PTFE absorbed the electrons, holes were simultaneously left on the catalyst. Because of their potent oxidative power, the holes in the valence band of sol–gel catalysts can efficiently oxidize organic pollutants, much like photocatalysis. In the absence of light, the tribocatalytic tests showed that ZnO and ZnO/Nd₂O₃ flowers could remove antibiotics (Doxycycline) when magnetized. We could further improve the tribocatalytic performance by adjusting the quantity of rare earth elements (1, 2, 3, 4 and 5 mol%), stirring speed, and magnetic rod type. Besides creating a green tribocatalysis method for organic pollutants’ oxidative purification, this work provides a possible pathway for transforming environmental mechanical energy into chemical energy, which may be applied to environmental remediation and sustainable energy. Full article

Zinc stannate (ZnSnO₃), a lead-free perovskite oxide, possesses a wide band gap along with ferroelectric and piezoelectric characteristics, but its practical use is limited by nanoparticle agglomeration and poor mechanical stability. In this study, ZnSnO₃ nanoparticles were synthesized via a chemical precipitation method and incorporated into electrospun polyvinylpyrrolidone (PVP) nanofibers to overcome these drawbacks. XRD confirmed the formation of orthorhombic perovskite ZnSnO₃, while FTIR verified successful embedding into the PVP matrix without chemical degradation. UV–Vis analysis revealed a slight blue shift in the absorption edge, with the optical band gap widening from 3.61 eV (ZnSnO₃) to 3.73 eV (ZnSnO₃/PVP), accompanied by enhanced visible light absorption. SEM images showed that agglomerated ZnSnO₃ nanoparticles were transformed into smooth, bead-free nanofibers with diameters ranging from 0.22 to 1.80 μm. The synergy between ZnSnO₃ crystallinity and PVP flexibility imparts structural integrity, tunable optical behavior, and mechanical robustness, making the hybrid nanofibers promising candidates for photocatalysis, flexible optoelectronics, and energy-harvesting applications. Full article

Modern medicine is facing a significant challenge in dealing with infections caused by Candida spp. and the biofilms they form. Although there are numerous treatment methods available for Candida species, standard therapeutic protocols are increasingly failing, particularly in cases of chronic local infections, such as those affecting immunocompromised patients (e.g., due to immunosuppression or diabetes). In such cases, a promising approach is to use nanomaterials to inactivate and eradicate Candida spp. and their biofilms. In order to limit the spread of Candida spp. and their biofilms within the healthcare environment, thereby reducing the risk of patient infection, photocatalysis appears to be a noteworthy method for improving therapeutic outcomes. Candida spp. biofilms are difficult to eradicate because they possess multiple resistance mechanisms—including protective extracellular matrix, efflux pumps, quorum sensing, persister and Goliath cells—which collectively enhance drug tolerance, adhesion, and survival rates under antifungal treatment. The use of nanomaterials, such as nanoparticles, carbon dots, or nanozymes for photocatalytic processes, seems to be a promising solution, showing outstanding results in Candida spp. biofilm disruption and inactivation. This is due to their superior biofilm penetration, effective destruction of proteins and enzymes, destabilization of EPS, degradation of nucleic acids, and reduced drug resistance. We collected the most important nanomaterials useful in combating Candida spp. biofilm and organized the photocatalysis mechanism of action in its disruption. Based on current research, we have compiled modern strategies involving nanomaterials and their photocatalytic activity for potential application in the healthcare environment, with the aim of reducing the presence of Candida spp. biofilms and, consequently, lowering the incidence of Candida spp.-related infections. Full article

Mycotoxin contamination is a crucial issue in food safety. However, the removal of trace amounts of mycotoxins from complex food and feed matrices without significant loss of nutritional and flavor quality remains a significant challenge. The integrated adsorption–catalysis strategy involves immobilizing catalytic modules onto adsorption materials, enabling in situ degradation while enriching the mycotoxins. This approach can significantly reduce the dosage of detoxification agents and achieve efficient removal of trace mycotoxins in food. This review provides an overview of adsorbents with enrichment capabilities and their applications in the targeted removal of mycotoxins from food. The adsorption–degradation coupled systems are categorized into the following two main types: adsorption–photocatalysis coupled systems and adsorption–biocatalysis coupled systems. The review introduces recent advances in the design of bifunctional catalysts, focusing on their synergistic mechanisms and practical applications for detoxifying various mycotoxins in food matrices. Finally, the review discusses current industrial challenges and offers insights into future directions for this field. Full article

Brilliant blue, as a pigment food additive, has all the characteristics of printing and dyeing wastewater and belongs to persistent and refractory organic compounds. The photocatalysis–Fenton reaction system consists of two parts: photocatalytic reaction and Fenton reaction. Electrons promote the decomposition of H₂O₂ to produce •OH. In addition, the effective separation of e- and h⁺ by light strengthens the direct oxidation of h⁺, and h⁺ reacts directly with OH⁻ to produce •OH, which can further promote the removal of organic pollutants. In this paper, g-C₃N₄ and Fe/g-C₃N₄ photocatalysts were prepared by the thermal polycondensation method. Fe/g-C₃N₄ of 15 wt% can reach 98.59% under the best degradation environment, and the degradation rate of g-C₃N₄ is only 7.6% under the same conditions. The photocatalytic activity of the catalysts was further studied. Through active species capture experiments, it is known that •OH and •O₂⁻ are the main active species in the system, and the action intensity of •OH is greater than that of •O₂⁻. The degradation reaction mechanism is that H₂O₂ combines with Fe²⁺ in Fe/g-C₃N₄ to generate a large amount of •OH and Fe³⁺, and the combination of Fe-N bonds accelerates the cycle of Fe³⁺/Fe²⁺ and promotes the formation of •OH, thereby accelerating the degradation of target pollutants. •O₂⁻ can reduce Fe³⁺ to Fe²⁺, Fe²⁺ reacts with H₂O₂ to produce •OH, which promotes degradation, and •O₂⁻ itself also plays a role in degradation. In addition, under the optimal experimental conditions obtained by response surface experiments, the fitting degree of first-order reaction kinetics is 0.96642, and the fitting degree of second-order reaction kinetics is 0.57884. Therefore, this reaction is more in line with first-order reaction kinetics. The adsorption rate is only proportional to the concentration of Fe/g-C₃N₄. Full article

Green hydrogen production using membrane electrode assembly (MEA) has attracted significant attention due to its remarkable energy conversion efficiency. To further enhance its sustainability, MEA-based water electrolysis can be integrated with renewable solar energy by adopting a photocatalytic MEA (P-MEA) system, incorporating light-transmitting windows into MEA stacks, and employing suitable photocatalytic electrode materials. A critical challenge lies in developing cost-effective and high-performance photocatalytic electrode materials by replacing conventional noble material systems with earth-abundant photocatalytic electrode materials. This review discusses recent advances in P-MEA concepts and fabrication strategies for photoelectrodes tailored to MEA operation. Particular emphasis is placed on elucidating the mechanisms of light-induced charge dynamics that govern the P-MEA-based water electrolysis process. Overall, this review highlights the synergistic potential of integrating photocatalysis with MEA-based water electrolysis to advance sustainable green hydrogen production. Full article

Photo(electro)-catalysis has increasingly attracted attention from researchers due to its wide applications in green chemical transformation, including organic synthesis and environmental remediation. As a promising candidate, the n-type semiconductor WO₃ possesses a suitable bandgap (~2.6 eV), good visible-light response, high chemical stability, and multi-electron transfer capability, thus endowing it with enormous potential in heterogeneous photocatalysis (PC) and photoelectrocatalysis (PEC) to address environment and energy issues. In this review, the recent research progress of WO₃-based photo(electro)-catalysts is examined and systematically summarized with regard to construction strategies and various application scenarios. To start with, the research background, functionalization methods and possible reaction mechanisms for WO₃ are introduced in depth. Key influencing factors, including light absorption capacity, charge carrier separation, and reusability, are also analyzed. Then, diverse applications of WO₃ for the elimination of organic pollutants (e.g., persistent organic pollutants and polymeric wastes) and green organic synthesis (i.e., oxidation, reduction, and other reactions) are intentionally discussed to underscore their vast potential in photo(electro)-catalytic performance. Finally, future challenges and insightful perspectives are proposed to explore effective WO₃-based materials. This comprehensive review aims to offer profound insights into innovative exploration of high-performance WO₃ semiconductor catalysts and guide new researchers in this field to better understand their vital roles in green organic synthesis and hazardous pollutants removal. Full article

The increasing presence of antibiotics such as cephalosporins in wastewater represents a significant environmental risk. These compounds are excreted in large quantities, and conventional wastewater treatment plants are often ineffective at their removal. Consequently, the development of more sustainable and efficient treatment technologies is essential. In this study, the removal of cephalosporins from aqueous solutions was evaluated through adsorption using pine bark biochar, photocatalysis with TiO₂, and a combination of both processes. Kinetic experiments were conducted with cephalosporin solutions (15 mg/L), employing 150 mg/L of biochar, 100 mg/L TiO₂, or their combination, under continuous stirring and/or UV-vis irradiation. Samples were collected at 0 and 120 min and analyzed via UV-vis spectrophotometry. Adsorption isotherms were established for initial cephalosporin concentrations ranging from 5 to 50 mg/L. The biochar alone achieved a removal efficiency of 94.2% after 120 min. Photocatalysis with TiO₂ alone resulted in 75% removal, while the combined approach reached 95.9%, indicating a synergistic effect between adsorption and photodegradation mechanisms. Kinetic data fitted the pseudo-second-order model, and the Langmuir isotherm provided the best correlation, suggesting monolayer adsorption. These findings demonstrate that pine bark biochar, whether used independently or in combination with TiO₂, constitutes an eco-friendly, effective, and low-cost alternative for the removal of antibiotics from wastewater, while simultaneously contributing to the valorization of forestry residues. Full article

Nitrogen oxides (NO_x) are major atmospheric pollutants, and their escalating emissions, driven by rapid economic development and urbanization, pose a severe threat to both the ecological environment and human health. Conventional denitrification technologies are often hampered by high costs, significant energy consumption, and stringent operational conditions, making them increasingly inadequate in the face of tightening environmental regulations. In this context, photocatalytic technology, particularly systems based on graphitic carbon nitride (g-C₃N₄), has garnered significant research interest for NO_x removal due to its visible-light responsiveness, high stability, and environmental benignity. To advance the performance of g-C₃N₄, numerous modification strategies have been explored, including morphology control, elemental doping, defect engineering, and heterostructure construction. These approaches effectively broaden the light absorption range, enhance the separation efficiency of photogenerated electron-hole pairs, and improve the adsorption and conversion capacities for NO_x. Notably, constructing heterojunctions between g-C₃N₄ and other materials (e.g., metal oxides, noble metals, metal–organic frameworks (MOFs)) has proven highly effective in boosting catalytic activity and stability. Furthermore, the underlying photocatalytic mechanisms, encompassing the generation and migration pathways of charge carriers, the redox reaction pathways of NO_x, and the influence of external factors like light intensity and reaction temperature, have been extensively investigated. From an application perspective, g-C₃N₄-based photocatalysis demonstrates considerable potential in flue gas denitrification, vehicle exhaust purification, and air purification. Despite these advancements, several challenges remain, such as limited solar energy utilization, rapid charge carrier recombination, and insufficient long-term stability, which hinder large-scale implementation. Future research should focus on further optimizing the material structure, developing greener synthesis routes, enhancing catalyst stability and poison resistance, and advancing cost-effective engineering applications to facilitate the practical deployment of g-C₃N₄-based photocatalytic technology in air pollution control. Full article

The photocatalytic degradation of Crystal Violet (CV) using ZnO-based nanomaterials presents a promising solution for addressing water pollution caused by synthetic dyes. This review highlights the exceptional efficiency of ZnO and its modified forms—such as doped, composite, and heterostructured variants—in degrading CV under both ultraviolet (UV) and solar irradiation. Key advancements include strategic bandgap engineering through doping (e.g., Cd, Mn, Co), innovative heterojunction designs (e.g., n-ZnO/p-Cu₂O, g-C₃N₄/ZnO), and composite formations with graphene oxide, which collectively enhance visible-light absorption and minimize charge recombination. The degradation mechanism, primarily driven by hydroxyl and superoxide radicals, leads to the complete mineralization of CV into non-toxic byproducts. Furthermore, this review emphasizes the emerging role of Artificial Neural Networks (ANNs) as superior tools for optimizing degradation parameters, demonstrating higher predictive accuracy and scalability compared to traditional methods like Response Surface Methodology (RSM). Potential operational challenges and future directions—including machine learning-driven optimization, real-effluent testing potential, and the development of solar-active catalysts—are further discussed. This work not only consolidates recent breakthroughs in ZnO-based photocatalysis but also provides a forward-looking perspective on sustainable wastewater treatment strategies. Full article