Recent advancements in adsorptive removal of organophosphate pesticides from aqueous phase using nanomaterials

Abstract

Organophosphates (OPs) being the most widely used (similar to 36%) pesticides, are infamous for presence of their traces in surface waters and serious health hazards to humans and animals. Hence, rapid, efficient, easy to use, and cost-effective methods must be explored for their remediation in contaminated waters. Amongst the different pesticide removal methods, adsorption is extensively used as it is economic unit process which is easy to operate and renders no residual by-product. Moreover, nano-sized adsorbents with novel physico-chemical properties may even be more effectively employed for sorptive removal of OPPs in contaminated waters. The review provides an overview of organophosphate pesticides (OPPs) in terms of usage, environmental contamination, and toxicity. Nanomaterials (e.g., carbon nano-structures, metal nanoparticles and oxides, quantum dots, and metal organic frameworks) categorized into inorganic, organic, and hybrid nanomaterials employed for adsorptive removal of OPPs from aqueous phase have been discussed. The parameters that determine their adsorption efficiency have been discussed, calculated, and compared for different nanostructures. The operating mechanisms behind adsorption of OPPs on nanomaterials are mainly electrostatic interactions, H-bonding, and pi-pi stacking (carbon-based nanomaterials), and exchange or sharing of electrons between vacant active site of nanocomposite and OPP molecules (in case of hybrid materials). Diffusion mechanism and rate-limiting steps have been explored via intra-particle diffusion model. The factors influencing the efficiency of adsorbents such as pH, temperature, adsorbent concentration, and incubation time have also been included. The review further recapitulates the details of thermodynamic studies of adsorption process which give information about the spontaneity and exothermic/endothermic nature of the process. The review concludes with summary and future prospects of sorptive removal of OPPs in water.