Agricultural wastewater treatment: a review of nanomaterial applications

Nutrient-enriched wastewaters from agriculture, involving cultivation, husbandry, aquaculture, and agro-processing operations, include a wide variety of pollutants, including nutrients, pesticides, metals, veterinary drugs, pathogens, and suspended solids. In response to such wastewater treatment challenges, the potential of nanoparticles is seen owing to their high surface-to-volume ratio, adjustable surface chemistry, and multistage catalytic properties. This review presents a critical evaluation of the state of research on using nanomaterials for treating agricultural wastewater. In particular, it considers recent advances in adsorption, photocatalysis, redox decontamination, antibacterial activity, and hybrid approaches. Comparing studies, one can conclude that the removal efficiency of pristine metal oxides (TiO₂ and ZnO) as photocatalysts reaches 80–99%, whereas graphene and hybrid nanomaterials show more than 90% removal efficiency due to better charge separation and visible-light operation. The range of reported adsorption capacity values is 20–700 mg g−¹, depending on material structure, modification, and type of wastewater used. In addition, this review discusses structure-property relations and technological aspects of photocatalytic efficiency, scale-up, techno-economic feasibility, toxicity, environmental stability, and ecotoxicology of nanoparticles. The pilot-scale tests, involving solar photocatalytic reactors and nanocomposite membrane systems, are evaluated in order to assess opportunities and challenges related to the process of technology transfer. Lastly, possible future directions are suggested in terms of AI-assisted materials design, green synthesis approaches, smart reactor designs, circular economy considerations, and standardized environmental risk assessments. Through the integration of materials design, functionalities, comparative evaluation, and practical implementation, this review offers an exhaustive framework for the development of safe and scalable nanotechnologies for agricultural wastewater treatment.