Calcium oxyhydroxide (CaO/Ca(OH)2) nanoparticles: Synthesis,characterization and evaluation of their capacity to degrade glyphosate-based herbicides (GBH)

Nanometric calcium oxyhydroxides (CaO/Ca(OH)₂) were synthesized by two chemical routes, controlled precipitation and polymer complex (Pechini). The ceramic powders synthesized by the Pechini method were assessed for their ability to remove organic molecules of a glyphosate-based herbicide (GBH). The nanoparticles were characterized using ultraviolet–visible (UV–Vis) absorption, infrared (IR), and Raman spectroscopies, as well as with X-ray diffraction (XRD) and scanning electron microscopy (SEM). Characterization revealed the synthesized particles to be nanometric in size (<100 nm), with an irregular morphology and a band gap of ~6.3 eV, evidencing a quantum confinement phenomenon. In testing for the removal of GBH with the CaO/Ca(OH)₂ synthesized by the Pechini method, a new product was formed by interaction with the organic molecules. The CaO/Ca(OH)₂-GBH interaction was so strong, at room temperature, that the solid completely dissolved, leaving no sediment. To determine the chemical nature of the resulting solution, aliquots were taken at the end of the test and analyzed by IR spectroscopy, revealing the existence in the system mainly of phosphate and phosphate-calcium groups, indicating that an important chemical reaction must have occurred between CaO/Ca(OH)₂ and HBG to modify the chemical structure of both compounds. The results obtained lead us to consider the synthesized CaO/Ca(OH)₂ nanoparticles as potential removers of agrochemical residues and other organic compounds that exist in water sources.