A thermosensitive molecularly imprinted poly-NIPAM coated MWCNTs/TiO2 photocatalyst for the preferential removal of pendimethalin pesticide from wastewater

Abstract

In order to realize a selective photodegradation of a specific pesticide from water, a novel thermosensitive molecularly imprinted poly N-isopropylacrylamide (NIPAM) coated MWCNTs/TiO2 nanocomposite (MWCNTs/TiO2/TMIP) was synthesized. Pendimethalin (PM) herbicide was chosen as the target contaminant molecule. The structures and properties of the nanocomposites were characterized by FE-SEM, EDX, TEM, XRD, XPS, FT-IR, and UV–vis DRS techniques. MWCNTs/TiO2/TMIP exhibited a superior target specific recognition ability with the high adsorption capacity. The swelling form of poly-NIPAM at room temperature increased the binding ability of PM to the polymer layer. The excellent selectivities of the adsorption and photodegradation processes of MWCNTs/TiO2/TMIP were verified by comparing them with those of MWCNTs/TiO2/TNIP (a non-imprinted polymer) and also using two structural analogues of PM. The TMIP photocatalyst revealed a high activity in the degradation of PM with a rate constant of 0.0438 min −1 under visible light compared with other corresponding photocatalysts. This was due to the combination of the smart molecularly imprinted technique and the photocatalytic process. In addition, a plausible mechanism for PM photodegradation was proposed based on charge carrier scavenger experiments, indicating that the main active species of this photocatalytic process are the O2− radicals.