Utilização de biocarvão para absorção de glifosato em meio aquoso

Abstract

Glyphosate, one of the most widely sold pesticides, is the active ingredient in over 750 broad-spectrum herbicides. Its application across large crop areas and potential overuse, have led to it being frequently researched in scientific literature. Although it is not classified as extremely toxic, there is growing global attention to its potential direct and indirect health effects. Adsorption is a promising route for glyphosate removal, and materials derived from agricultural waste, such as green coconut husks, are emerging as a sustainable alternative. Brazil is one of the world's largest coconut producers, generating millions of tons of unused green coconut husks annually—up to 3 million tons per year. These husks represent a vast lignocellulosic resource that can be converted into biochar through heat treatment. The main objective of this study was to evaluate the efficiency of biochar produced from green coconut husk waste as a biosorbent in removing glyphosate from aqueous media. The results and discussions demonstrated that all biochar samples were satisfactorily obtained through the pyrolysis process. The adsorption efficiency of sample A7 was 84.36%. Glyphosate adsorption increased rapidly at low concentrations and more slowly until the sites on the adsorbent surface were saturated. Both the Langmuir and Freundlich models presented excellent fits to the data, which is consistent with the most recent literature, indicating that glyphosate adsorption on biochar may involve multiple mechanisms, including electrostatic attraction, physical pore trapping, and size exclusion. EDS analyses indicated changes in elemental 2 composition (reduction of carbon and oxygen and appearance of phosphorus) in the post-adsorption samples, attesting to the effectiveness of the glyphosate adsorption process. In conclusion, the results obtained indicate that green coconut shell biochar has promising potential as an adsorbent for glyphosate removal in aqueous media. The high adsorption efficiency observed with a small mass of adsorbent suggests that large quantities of biochar would not be necessary for the treatment of contaminated water, contributing to the water treatment process and to the promotion of sustainable Brazilian agriculture, with responsible consumption and production.