C18 -functionalized zirconized silica for effective removal of phorate pesticide from agricultural runoff involving groundwater remediation

Abstract

Phorate, a highly toxic organophosphorus pesticide, is frequently used in agriculture to control insects and pests. It can persist for long periods in water sources, posing a risk to human health, aquatic life, and wildlife. Thus, this study developed a practical method for the removal of toxic phorate from water using C18-modified zirconized silica (named C18–ZrSi) adsorbent. Batch adsorption experiments were conducted by varying pH, adsorbent amount, phorate concentration, incubation time, and temperature. The optimal conditions for maximum adsorption of phorate were found to be at pH 7.0 and a temperature of 20–30 °C. X-ray- related and electron microscopies were implemented to characterize the features of the C18–ZrSi adsorbent and demonstrated the phorate adsorption on their surface. The C18–ZrSi adsorbent exhibited adsorption behaviour towards phorate that adhered to a mixed Freundlich and Langmuir isotherm, with a spontaneous and exothermic adsorption process, pseudo-second-order kinetics, and multiple stages of adsorption. The maximum Langmuir adsorption capacity of the C18–ZrSi adsorbent for phorate was identified as 30.5 mg g−1. It is proved that the C18–ZrSi adsorbent efficiently capture phorate from water through the hydrophobic interaction, hydrogen bonding, and Lewis acid-base force. In addition, the C18–ZrSi adsorbent recovered more than 89% of phorate after the third adsorption and desorption. We demonstrated that the C18–ZrSi adsorbent exhibited good selectivity for the removal of phorate from agriculture runoff water samples.