Post-modified polymer with imidazole groups as an efficient and reusable heterogeneous catalyst for organophosphate degradation

Abstract

In this work, the commercial polymer poly(ethylene-alt-maleic anhydride) was used as a platform for the preparation of an imidazole-rich polymeric catalyst (PEIIm) designed for organophosphate degradation. The catalyst was prepared at gram-scale using simple and cost-effective steps and was characterized by 1H NMR, IR, CHN and TGA. PEIIm showed higher activity than the free imidazole towards the degradation of diethyl 2,4-dinitrophenylphosphate, an organophosphate model, and was recovered by centrifugation and reused without loss of activity. Importantly, experiments performed under excess of substrate demonstrate that true catalysis takes place. Solvent kinetic isotope effect indicates that the pendant imidazole groups attack the phosphorus atom to form a phosphorylated polymeric intermediate that is rapidly hydrolyzed, allowing for the catalyst regeneration. PEIIm was also employed in the degradation of toxic pesticide ethyl paraoxon, resulting in a reduction in its half-life from 780 days to 25 days at 25 °C, pH 8.0.