Degradation of traditional and new emerging pesticides in water by nanomaterials: recent trends and future recommendations

Rapid industrialization and extensive use of pesticides in agriculture practices have contributed to the leaking of pesticide residues into water. Among them, organochlorines are highly toxic with half-lives of many years followed by organophosphates (OPs). Being banned in many countries, most of the pesticides are still persisting in the environment. Due to high perseverance, toxicity and potential to bioaccumulation, their removal is imperative. In this direction, conventional adsorbents such as commercial activated carbon, agricultural and natural waste were highly employed. In modern era, nanomaterials (including nanocomposites and nanobiocomposite) with high surface area come out as most economic, rapid and effective catalyst. TiO2 (photocatalyst) and Fe-0 by itself or with oxidizing agents are playing a promising role in elimination of pesticide pollution and open the opportunities for exploring other nanoparticles as well. Further, their modified, doped or composites form showed enhanced characteristics due to introduction of new energy levels or increase in surface area. In contrast to TiO2 and Fe-0, various nanostructured metal oxides found to degrade OP pesticides by rapid reactive adsorption followed by cleavage of P-O bond via SN2 mechanism. The present review focuses on the present status of pesticide removal using nanoparticles through adsorption together with photocatalytic or redox or reactive degradation. Herein, detailed information on several pesticides, problems related to pesticide, their metabolites, environmental concentration and need for degradation has been presented. In addition, importance of green synthesized nanoparticles along with limitation and potential health risk of nanomaterials in degradation of various organic pollutants has been highlighted.