Adsorption of the Herbicide Endosulfan by Newly Discovered Zeolitic Tuffs in Mexico

The study presents experimental results on the adsorption of endosulfan in new natural zeolite deposits from Mexico. The adsorption of this herbicide was evaluated using inverse gas chromatography with a thermal conductivity detector and helium as the carrier gas. The experimental adsorption data were analyzed using the Langmuir and Freundlich equations in their linear form over a temperature range of 413–573 K. The study also estimated thermodynamic parameters such as the Free Energy of Gibbs (ΔG), isosteric enthalpy of adsorption (ΔH), and entropy change (ΔS) within this temperature range. The results indicated that the zeolites studied had a low adsorption capacity for this herbicide under the experimental conditions. The study also quantitatively determined the presence of starting minerals, with Na-Mordenite and Na-Clinoptilolite being the most prevalent, followed by Ca-Chabazite, Ca-Clinoptilolite, and Montmorillonite, with Quartz being present in low amounts. The NMOR zeolite underwent ion exchanges with AgNO3 to produce the Ag-MOR zeolite and assess its herbicide adsorption capacity. Another mineral, Ca-Stilbite, was present in higher quantities than Ca-Clinoptilolite and Quartz.