Polymer and graphitic carbon nitride based nanohybrids for the photocatalytic degradation of pharmaceuticals in wastewater treatment - A review

Pharmaceuticals, including antibiotics and anti-inflammatory drugs, have been frequently detected in water reservoirs, in concentrations ranging from ng/L to mu g/L, owing to their wide use in treatment of human and animal disease. Their uncontrolled use results in their increased release into the environment which is harmful for humans, animals, aquatic life and aquatic system. To remove these pollutants from water bodies, various processes including adsorption, membrane and bioreactors have been employed. Among them photocatalysis is one of the most advantageous treatment. Application of advanced chemical treatment, including advanced oxidation or reduction processes (AOPs or ARPs) based on organic-inorganic nanohybrids (OINHs) as photocatalysts revealed high effectiveness. OINHs are combination of two or more components which are organic and inorganic in nature. These materials have been synthesized by various methods and offers novel features owing to synergistic effect of their component. These materials are synthesized through sol-gel, surface functionalization, one pot synthesis, wrapping, and electrospinning methods. Organic components are essential in enhancing photocatalytic activity through increasing stability, surface area, functionality and light responsiveness of nanohybrid. Reports suggest > 99 % degradation of studied pharmaceuticals by these type of photocatalysts in time range of 30-60 min. High effectiveness was reported for carbamazepine, ciprofloxacin, diclofenac, ibuprofen, naproxen, paracetamol, sulfamethoxazole and tetracycline. This review summarizes recent literature on application of OINHs i.e. graphene oxide, g-C3N4, and polymer based nanohybrids, in photocatalytic removal of pharmaceuticals from wastewater via AOPs while elaborating on toxicity of pharmaceuticals, synthesis of OINHs and degradation mechanism of pharmaceutical drugs. Besides, current challenges faced in this field as well as future recommendations are discussed.