The increasing presence of various organics poses significant threats to aquatic ecosystems and living organisms. Conventional water treatment methods are often insufficient, necessitating the development of powerful and sustainable alternatives. This study addresses this challenge by exploring the synthesis of ZnO nanoparticles using green tea leaves extract—an eco-friendly approach—for the sunlight-activated removal of organics in agri-food wastewater. The research examined different conditions for the removal of clomazone (CLO), tembotrione (TEM), ciprofloxacin (CIP), and zearalenone (ZEA). Nitrate-derived ZnO synthesized in a water medium (N-gZnO_w) exhibited the highest photocatalytic activity, removing 98.2, 95.8, 96.2, and 96.6% of CLO, TEM, CIP, and ZEA. Characterization techniques (XRD, Raman spectroscopy, SEM, zeta potential measurements, UV–visible spectroscopy) confirmed the synthesis of N-gZnO_w, with an average particle size of 14.9 nm, an isoelectric point of 9.9, and a band gap energy of 2.92 eV. Photocatalytic experiments identified 0.5 mg/cm³ as an optimal catalyst loading, while a higher initial pollutant concentration reduced degradation efficiency. LC-ESI-MS/MS measurements confirmed the efficient pollutant degradation and the formation of degradation intermediates. Hence, this study demonstrates that green tea extract-synthesized ZnO nanoparticles offer a promising, sustainable solution for removing herbicides, pharmaceuticals, and mycotoxins from wastewater, paving the way for eco-friendly water purification technologies.

Clear and sanitarily adequate water scarcity is one of the greatest problems of modern society. Continuous population growth, rising organics concentrations, and common non-efficient wastewater treatment technologies add to the seriousness of this issue. The employment of various advanced oxidation processes (AOPs) in water treatment is becoming more widespread. In this review, the state-of-the-art application of three AOPs is discussed in detail: photocatalysis, sonophotolysis, and sonophotocatalysis. Photocatalysis utilizes semiconductor photocatalysts to degrade organic pollutants under light irradiation. Sonophotolysis combines ultrasound and photolysis to generate reactive radicals, enhancing the degradation of organic pollutants. Sonophotocatalysis synergistically combines ultrasound with photocatalysis, resulting in improved degradation efficiency compared to individual processes. By studying this paper, readers will get an insight into the latest published data regarding the above-mentioned processes from the last 10 years. Different factors are compared and discussed, such as degradation efficiency, reaction kinetics, catalyst type, ultrasound frequency, or water matrix effects on process performance. In addition, the economic aspects of sonophotolysis, photocatalysis, and sonophotocatalysis will be also analyzed and compared to other processes. Also, the future research directions and potential applications of these AOPs in wastewater treatment will be highlighted. This review offers invaluable insights into the selection and optimization of AOPs.

Pure water scarcity is an emerging, all-around problem that globally affects both the life quality and the world’s economy. Heterogeneous photocatalysis under solar irradiation is a promising technique for the organic pollutants (e.g., pesticides, drugs) removal from an aqueous environment. Furthermore, the drawbacks of commercially available photocatalysts can be successfully overcome by using innovative nanoparticles, such as ZrO₂/Fe₃O₄. Four ZrO₂/Fe₃O₄ nanopowders with a different mass ratio of ZrO₂ and Fe₃O₄ were synthesized using the chemical co-precipitation method. XRD analysis showed the presence of magnetite and hematite Fe-oxide phases in all samples. The content of the magnetite phase increased with the addition of 19% ZrO₂. The efficiency of the newly synthesized ZrO₂/Fe₃O₄ nanoparticles was investigated in the rapid removal of selected pollutants under various experimental conditions. Nevertheless, the influence of the water matrix on photocatalytic degradation was also examined. The obtained data showed that using ZrO₂/Fe₃O₄ nanosystems, an appropriate removal rate of the selected pesticides and pharmaceuticals can be reached after 120 min of solar irradiation. Further, the total organic carbon measurements proved the mineralization of the target emerging pollutants. ZrO₂/Fe₃O₄ nanoparticles are economically feasible, as their removal from the suspension can be easily achieved using affordable, environmentally-friendly magnetic separation.

In recent years, much attention has been paid to pharmaceuticals as potential toxic bioactive substances in the worldwide environment. These compounds are continuously introduced into the surroundings in small concentrations, which certainly affects the quality of water, ecosystem, and the general health of living organisms. Photocatalysis is a promising technique for treating pharmaceutically active compounds as organic pollutants over traditional technologies. This study proposes the application of photocatalysts composed of zinc oxide (ZnO) and tin oxide (SnO₂), synthesized using a solid-state method, for the photocatalytic degradation of two selected psychoactive drugs, amitriptyline (AMI) and alprazolam (ALP), under simulated solar and UV irradiation in an aqueous system. The newly synthesized photocatalysts were characterized using the following techniques: SEM/EDS, XRD, DLS, and UV/Vis spectroscopy. The obtained data confirmed the successful synthesis and the possible photocatalytic application of the new materials. Concerning the photocatalytic evaluation, the main results indicate that the highest removal efficiency of AMI and ALP was reached in the presence of ZnO/SnO₂ synthesized in a molar ratio of 2:1 and calcined at 700 °C, under 1.0 mg/mL catalyst loading. Based on the reutilization findings, it can be concluded that the mentioned photocatalyst had not lost its efficiency after three successive runs for the photodegradation of ALP. Additionally, pure ZnO powders showed the highest activity after calcination at 500 °C, in the case of both examined pollutants. The experiments with tert-butanol, sodium fluoride, and ethylenediaminetetraacetic acid suggested that the relative contribution of various reactive species changed in the following order: positively charged holes > ${\mathrm{OH}}_{\mathrm{free}}^{•}$ > ${\mathrm{OH}}_{\mathrm{ads}}^{•}$.

The growing prevalence of emerging contaminants in the aquatic environment poses a critical challenge to global water security. Conventional treatment methods often fail to remove persistent pollutants, necessitating the development of sustainable and efficient alternatives. Heterogeneous photocatalysis, one of the advanced oxidation processes, driven by the light-induced generation of reactive species, has emerged as a promising solution. However, the high cost and environmental footprint of conventional photocatalysts limit large-scale implementation. This review explores the innovative use of waste-derived materials, originating from agricultural residues, industrial by-products, food waste, and electronic waste, as green precursors for photocatalyst synthesis. These materials offer unique structural and chemical properties, including a high surface area, tunable bandgaps, and enhanced stability, while supporting circular economy principles. Recent advances in synthesis strategies, performance optimization, and hybrid system integration are critically analyzed, alongside challenges related to scalability, environmental safety, and process standardization. Waste-to-resource approaches in photocatalysis represent a transformative pathway toward sustainable water treatment and resource recovery.

Pure water scarcity is the most significant emerging challenge of the modern society. Various organics such as pesticides (clomazone, quinmerac), pharmaceuticals (ciprofloxacin, 17α-ethynilestradiol), and mycotoxins (deoxynivalenol) can be found in the aquatic environment. The aim of this study was to fabricate ZnO nanomaterial on the basis of banana peel extract (ZnO/BPE) and investigate its efficiency in the photocatalytic degradation of selected organics under various experimental conditions. Newly synthesized ZnO/BPE nanomaterials were fully characterized by the XRD, FTIR, SEM-EPS, XPS, and BET techniques, which confirmed the successful formation of ZnO nanomaterials. The photocatalytic experiments showed that the optimal catalyst loading of ZnO/BPE was 0.5 mg/cm³, while the initial pH did not influence the degradation efficiency. The reusability of the ZnO/BPE nanomaterial was also tested, and minimal activity loss was found after three photocatalytic cycles. The photocatalytic efficiency of pure banana peel extract (BPE) was also studied, and the obtained data showed high removal of ciprofloxacin and 17α-ethynilestradiol. Finally, the influence of water from Danube River was also examined based on the degradation efficiency of selected pollutants. These results showed an enhanced removal of ciprofloxacin in water from the Danube River, while in the case of other pollutants, the treatment was less effective.