Thiabendazole adsorption on montmorillonite, octadecyltrimethylammonium- and Acremonium sp.-loaded products and their copper complexes

Abstract

This study is a preliminary approach to develop novel montmorillonite (Mt) based adsorbents for removing inorganic and organic contaminants in a step-like process. Biomass (fungi) and surfactant (octadecyltrimethylammonium bromide) modified montmorillonites (BMt and OMt, respectively) were obtained. In a prior step, Cu2+ was loaded into Mt, BMt and OMt. In a second step, the materials (Mt, Mt-Cu, BMt, BMt-Cu, OMt, OMt-Cu) were used as thiabendazole (TBZ) adsorbents. TBZ adsorption isotherms were performed, and Langmuir, Freundlich and Langmuir-Freundlich mathematical models were evaluated. TBZ removal efficiency of the materials was also tested using three adsorbent dosages. The adsorbents and TBZ-adsorbed products were characterized by X-ray diffraction and thermal analysis, and by electron paramagnetic resonance (EPR) and solid-state nuclear magnetic resonance measurements (ss-NMR). To determine the subsequent arrangement of the adsorption products, leaching experiments were also conducted. In the BMt sample, TBZ adsorption was enhanced compared to the raw Mt sample. An opposite behaviour was observed for OMt samples. All the Cu2+-loaded materials showed better TBZ removal efficiencies than the same materials without Cu2+. Furthermore, Cu2+ chelation through the imidazolic and thiazolic nitrogen atoms of TBZ in all Cu2+-loaded samples allowed TBZ and Cu2+ to be resistant to migration in environmental leaching conditions.