Ecofriendly Synthesis of Titanium Dioxide for Glyphosate Adsorption

Abstract

The widespread use of glyphosate for weed control in agricultural, silvicultural, and urban areas worldwide is causing concerns about its potential toxicity and mobility in environment. Consequently, there is a pressing need to develop treatment processes to mitigate the effects of glyphosate, its metabolites, and/or coadjutants on the environment. Titanium dioxide nanoparticles (TNPs), among the most widely used engineered NPs, have recently attracted significant attention for glyphosate adsorption. In this study, TNPs were obtained through two synthesis procedures working at low temperatures and with a reduced amount of organic solvent. The first involves a polycondensation reaction of alkoxide precursors at 70 °C in a water-in-oil (W/O) microemulsion with a 1 : 1 volume ratio, employing cetylpyridinium bromide (CPB) as a cationic surfactant to obtain crystalline TNPs. In the second method, two resins characterized by different morphologies were used as a template, to grow amorphous TNPs. Glyphosate adsorption tests performed at different pH values, i.e. 4.0 and 8.5, revealed that the analyte is more effectively retained by the TNPs at pH 4.0, at which TiO₂ surfaces are positively charged and better interact with anionic glyphosate species. TNPs obtained via microemulsion using titanium alkoxide as the precursor and calcined at 450 °C showed excellent performance, removing from the solution nearly 99% of glyphosate, even at pH 8.5. Similarly, resin composites work efficiently in eliminating a high percentage of glyphosate, taking advantage of a better dispersion of amorphous TiO₂ and a higher surface-to-volume ratio. This study demonstrates the effective capture of glyphosate by titanium dioxide nanoparticles, highlighting some factors contributing to the adsorption ability, and their potential as a unique tool for adsorbing glyphosate in a one-pot process.