Synthesis and evaluation of TiO2 nanotubes/silylated graphene oxide-based molecularly imprinted polymer for the selective adsorption and subsequent photocatalytic degradation of 2,4-Dichlorophenoxyacetic acid

Abstract

2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the well-known commercial herbicides hailing from phenoxy family whose impulsive use becomes a serious threat to aquatic ecology and mankind. Herein we report a novel photocatalyst, TiO2 nanotubes/silylated graphene oxide-based molecularly imprinted polymer (SGOTNT@MIP) for the adsorption and photocatalytic degradation of 2,4-D using visible light. Initially, a TiO2/ silylated graphene oxide (SGOTNT) composite was synthesized in which surface molecular imprinting was done using 2- hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) monomers and 2,4-D as template. AIBN and EGDMA were employed as initiator and crosslinker correspondingly. The synthesized SGOTNT@MIP photocatalyst was characterized using FTIR, SEM, EDS,TG, Raman and XRD techniques. Studies were done to evaluate the effects of various factors like pH, contact time, temperature, etc. on the adsorption process. The pH 2.5 was found to be the optimum pH for maximum adsorption. Experimental kinetic data revealed pseudo-second-order kinetics of adsorption. SGOTNT@MIP showed high selective adsorption rate than its structural analogue. The photocatalytic degradation studies exhibited first-order kinetics and maximum degradation was obtained at pH 4. The regeneration studies authenticated that the SGOTNT@MIP is an excellent probe for the removal and degradation of 2, 4-D from its effluent.