Materials, nanomaterials, nanocomposites, and methods used for the treatment and removal of hazardous pollutants from wastewater: Treatment technologies for water recycling and sustainability

Clean water is becoming a scarce resource due to industrialization and urbanization, which have led to numerous contaminants being discharged into water sources. Pollution is mostly caused by organic and inorganic pollutants, oil, heavy metals, and bioorganisms in concentrations that are exceedingly toxic to the ecosystem. This is bound to increase wastewater, making water treatment a critical aspect of environmental conservation and sustainability. The water industry has to find dependable, affordable materials and methods to ensure sufficient supplies of fresh water. The available methods include physical, chemical, biological, and thermo-catalytic treatment techniques. Some of these methods require several natural and synthetic materials, including nanomaterials, to enhance the water treatment. The principles of chemistry and green synthesis of materials provide a clean platform to design these materials using cost-effective precursors, being nonhazardous and having considerable potential for large-scale manufacturing procedures. Besides carbon nanostructures and polymers, materials can be produced from natural and waste resources using green or semi-green procedures. Green nanomaterials with a large surface area and numerous active sites are highly suitable for the adsorption of contaminants. Semiconductors can use sunlight to catalyze advanced oxidation processes and are particularly good at eliminating recalcitrant water pollutants. This review offers a critical evaluation of the advanced treatment technologies, nanomaterials, and nanocomposites for use in water treatment of contaminated wastewater and industrial water reuse. The review will benefit scientists and users/decision makers’ in industrial sectors interested in water technology.