Diethyl dihydropyridine as sensitizer to enhance the catalytic activity of titanium dioxide for efficient degradation of pollutants

The compound 3,5-pyridine-dicarboxylic-acid-1,4-dihydro4-(4-hy-2,6- dimethyl diethyl ester (PDDD) was synthesized via a hydrothermal method and subsequently chemically grafted onto nano-TiO₂. The initial synthesis was confirmed by infrared spectroscopy. The catalyst was further characterized using X- ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (TEM) mapping, which conclusively demonstrated that the PDDD organic compound is covalently bonded to nano-TiO₂. This covalent bond exhibited exceptional performance in subsequent investigations. Methyl orange was employed as a model pollutant for the photocatalytic degradation of dye- contaminated wastewater under visible light. The effects of catalyst loading, initial methyl orange concentration, and pH on the degradation of wastewater were systematically investigated. The results demonstrated that the catalyst exhibited remarkable stability, with less than a 1% change in degradation efficiency after seven cycles of wastewater treatment. Furthermore, at a pH of 4 and a catalyst concentration of 2 g/L, the catalyst was capable of completely degrading a 100 mg/L methyl orange solution within 80 minutes. This catalyst offers a promising solution for the degradation of high-concentration wastewater.