One-step green synthesis of silica microcapsules with high pesticide loading for sustained-release

Abstract

Pesticides are vital for agricultural productivity but their excessive use has raised serious environmental concerns, including soil and water contamination. Traditional pesticide formulations often face issues of rapid degradation, leading to repeated applications and resource waste. Controlled-release systems, particularly microencapsulation, have been proposed as solutions to address these issues, offering the potential to enhance pesticide efficiency and minimize environmental risks. However, traditional methods usually rely on toxic solvents or post-loading processes, which pose significant ecological risks and elevates manufacturing costs. This study presents a one-step green synthesis method to produce silica microcapsules loaded with the pesticide pirimiphos-methyl (PM), a widely used organophosphorus pesticide, without the need for toxic solvents. The synthesis uses tetraethyl orthosilicate (TEOS) and PM as the oil phase, and utilizes surfactants and NaF in an oil/water (O/W) emulsion system. The process is catalyzed by hydrochloric acid to form a silica shell that encapsulates the pesticide in situ. The effects of NaF and the core-to-wall ratio on the morphology, pesticide loading, encapsulation efficiency, thermal stability, and controlled release of the microcapsules were evaluated. The results demonstrate that the microcapsules exhibit high pesticide loading (62.18 %), excellent encapsulation efficiency (up to 92.17 %), and improved thermal stability, with sustained pesticide release over 16 d. This green synthesis method represents a significant advancement in pesticide delivery systems, offering a scalable, eco-friendly solution for sustainable agriculture with reduced environmental and health risks.