Investigation of acid-activated iron-based bentonite materials for the oxidation mechanism of dimethyl disulfide

Abstract

Due to its low olfactory threshold and high volatility, Dimethyl disulfide (DMDS) is a well-known malodorous compound in pesticides and organic synthesis. This study utilizes sodium bentonite as catalyst support, treating it with acid activation and iron-based modification to create a catalytically active bentonite material. Following modification, the bentonite maintains its fundamental structure while integrating iron ions, resulting in an expanded interlayer spacing and increased specific surface area from 60.371 m2/g to 314.539 m2/g, thereby enhancing catalytic activity. Kinetic modeling fitting demonstrates that combining iron-based acid-activated bentonite with hydrogen peroxide (H2O2) produces the most efficient oxidative system, with the highest reaction rate constant（K = 0.08038 min−1） for DMDS degradation. The best degradation effect was achieved when the ratio of Fe-H-Bent to hydrogen peroxide was 1:5, the pH was 3, and the reaction temperature was 40 °C, and the removal rate was up to 98.9%. Electron paramagnetic resonance (EPR) spectroscopy confirms that hydroxyl radicals (·OH) are this system's primary driver of oxidation. Theoretical computations and product analyses provide insight into the oxidation pathway of DMDS, showing that initial oxidation occurs at the first sulfur atom, forming an intermediate that further oxidizes to dimethyl sulfoxide and ultimately to sulfur dioxide. This research offers a practical method for the effective removal of DMDS in pesticide plants and chemical industrial parks.