Remediation of herbicide mixtures in water using nanostructured adsorbents: Behavioral analysis

The improper or excessive use of herbicides has caused soil and water contamination, increasing the demand for techniques for environmental remediation. In this research, we assessed the effectiveness of nanostructured adsorbents in removing the herbicides mixtures of diuron, hexazinone, and sulfometuron-methyl, with the goal of applying this technique in environmental remediation efforts. The nanomaterials employed were microporous beta zeolite (BT), Al-MCM-41 mesoporous silica (AL), hydrotalcite clay (HT), and microporous carbonate biochar (BIO). The nanostructured adsorbents were characterized by X-ray diffraction, X-ray fluorescence, elemental analysis, and nitrogen adsorption and desorption at 77 K, point of zero charge, scanning electron microscope, and transmission electron microscopy. The descending adsorption values of nanostructured adsorbents: for diuron BT (99.35%) > BIO (96.36%) > AL (88.33%), hexazinone, BT (97.26%) > AL (83.75%) > BIO (14.22%), and sulfometuron-methyl, AL (95.73%) > BT (90.96%) > BIO (34.92%). The time required for the adsorption equilibrium was 1 hour, with greater adequacy to the pseudo-second-order kinetic model. The Langmuir and Freundlich isotherms showed the best fit of herbicide adsorption on the microporous BT and BIO, respectively. In the AL, the diuron and hexazinone experimental data fitted more precisely to Temkin's model and sulfometuron-methyl to Freundlich's model. Nanostructured adsorbents have different capacities to adsorb diuron, hexazinone, and sulfometuron-methyl herbicides present in aqueous media, with BT being the material with the highest adsorption capacity for the remediation of the mixture containing the three herbicides.