Enhanced adsorption of inorganic and organic pollutants by amine modified sodium montmorillonite nanosheets

Abstract

This article highlighted the preparation of viable and eco-friendly adsorbents for both organic and inorganic pollutants by modifying sodium montmorillonite using three different modifiers viz. N,N,N,N′,N′,N′-hexamethylhexamethylenediammonium dibromide (HM), N,N,N,N′,N′,N′-hexabutylhexamethylenediammonium dihydroxide solution (HDS) and N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA). X-ray diffraction (XRD) results indicated that the interlayer spacing was increased upon modification. The successful grafting of modifiers onto the interlayer was confirmed by ²⁹Si magic-angel spinning nuclear magnetic resonance (²⁹Si MAS NMR) spectral analysis. The adsorption of inorganic pollutants (Cu²⁺ and Zn²⁺) and organic pollutants [benzene, toluene, ethylbenzene and p-xylene (BTEX)] was discussed based on different properties. Based on the experimental results, in the case of HM, 100% modification was achieved and HM-modified montmorillonite possessed larger surface area. But contrarily HDS-modified montmorillonite with lower surface area showed enhanced adsorption capacity towards inorganic pollutants. Adsorption was 6 to 8 times greater in the modified montmorillonite compared to that of the unmodified one. Adsorption carried out in the mixed pollutants showed that there is no interaction between these pollutants, and the presence of one did not retard the adsorption of another one. The adsorption phenomenon was very complex and was influenced by various combined factors. However, adsorption was mainly controlled not only by surface area but also by the nature and surface charge of the modifiers.