The surface chemical functionality and diffusion mediated adsorption of organophosphates from their low concentration

Abstract

The detection and removal of pesticides from their very low concentration solution are daunting tasks. The development of substrates leading to the adsorption of the pesticides requires a thorough understanding of the adsorption process. Here, we studied the interaction of two organophosphates, phorate, and malathion, on functionalized by using four different silane coupling agents, namely n-propyltrimethoxy silane (PTMS), octyltrimethoxy silane (OTMS), 3- (trimethoxysilyl) propyl methacrylate (TMSPMA) and 3- (triethoxysilyl) propionitrile (TESPN).Diffusion controlled kinetic model with a surface phase concept is developed. The concentration of the pesticides used in this work in the range of 1–20 mg/L. The model is fitted to the real-time adsorption data of phorate, and malathion over various substrates obtained using QCM-D. The results show that TMSPMA functionalized surface being more hydrophilic among all surfaces adsorbs hydrophobic pesticides molecules more uniformly. The monolayer adsorbed mass of pesticides obtained experimentally aligns with the theoretically calculated mass for TMSPMA functionalized silica surface. The adsorption is explained through molecular interactions. A reasonably strong binding with a possibility of reversible binding of phorate and malathion on TMSPMA functionalized surface is observed.