First Principle Study of the Adsorption of Glyphosate on Illite Clay for Water Depollution

The use of herbicides such as glyphosate in the agricultural sector enables agricultural intensification and thus satisfies the demand for agricultural products on the market. Glyphosate is widely used in agriculture as a herbicide for weeding fields. However, its use has a major drawback that calls into question its many advantages. After use, its toxic residues and metabolites end up in groundwater, which is an important source of drinking water for the population. Adsorption is the most suitable technique for recovering these toxic residues before the water is consumed. Based on Density Functional Theory, implemented in the VASP simulation code, we studied the ability of illite to adsorb glyphosate. The absorbent properties, the abundance of illite throughout the world, particularly in Benin, and the fact that it is free from toxic products were the criteria that guide us in the of illite clay for our work. Our work revealed that the process of adsorption of glyphosate on the illite surface is exothermic. This process does not present any risk of release of toxic by-products on five of the six studied sites. The illite clay can then be used to design water depollution filters to decrease medical as well as financial burden.