Semicarbazide-Functionalized periodic mesoporous organosilica for efficient adsorption of chlorpyrifos and diazinon organophosphate pesticides from water

Organophosphate pesticides such as chlorpyrifos (CPF) and diazinon (DZN) are recognized as hazardous water pollutants due to their high stability and toxicity. In this study, a novel mesoporous adsorbent based on semicarbazide-functionalized periodic mesoporous organosilica (SC-Pr-PMO) was prepared and used to remove these pollutants from aqueous solutions. Characterization of the SC-Pr-PMO adsorbent was carried out using various techniques such as Fourier-transform infrared (FT-IR) spectroscopy, Brunauer-Emmett-Teller (BET) analysis, field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDS), EDS elemental mapping, X-ray diffraction (XRD), thermogravimetry/differential thermogravimetry analysis (TGA/DTA), and the pH of zero-point charge (pH pzc ). The effects of several factors on the adsorption performance including solution pH, adsorbent dosage, contact time, and initial pollutant concentration were investigated. The maximum adsorption capacity (q max ) was 178.02 mg g −1 and 116.20 mg g −1 for CPF (at pH = 11) and DZN (at pH = 7), respectively. The experimental adsorption data were analyzed using the Langmuir, Freundlich, Dubinin–Radushkevich and Temkin isotherm models, as well as the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. Also, the removal efficiency of CPF and DZN after five cycles reached 77.17% and 85.34%, respectively. Therefore, SC-Pr-PMO demonstrates excellent performance, as an effective, stable, easily separable, and reusable adsorbent, for CPF and DZN removal from aqueous environments.