Intercalation of Glyphosate in Mg–Al Layered Double Hydroxides and Its Controlled Release

The LDHs in the Mg-Al systems containing glyphosate were synthesized by the reconstruction and coprecipitation methods at a constant pH. The XRD data show that the Mg₂Al-glyphosate hybrid material was formed in both cases, even though a better crystallinity was achieved from the synthesis conducted by the coprecipitation method. Moreover, vertical glyphosate intercalation can be inferred, given the observed 7.9 Å interlamellar spacing. Solid-state NMR and FT-IR-ATR data corroborate the formation of the material, with significant changes in the spectra of both when comparing the hybrid materials and free glyphosate. Studies involving pH variation showed the greatest glyphosate release at pH 10, reaching approximately 70% and governed by first-order kinetics, confirmed by the simulation model. Experiments involving carbonate, nitrate, and chloride anions suggest that the presence of carbonate has a greater influence on glyphosate release and that an increase in the concentration of this anion also corroborates to an increase in glyphosate release, both of which are also governed by a first-order mechanism.