Effect of Silica Content in a Bio-Polymeric Blended Nanocomposite for Efficient Adsorption of Mercury in Basic Aqueous Solution

Abstract The current work describes the development of silica chitosan-guar gum blended nanocomposites (NCs) for the proficient removal of mercury (Hg 2+ ) ions in aqueous solution at pH 12. The silica NCs were prepared by dispersing the as-synthesized silica nanoparticles (NPs) into the chitosan-guar gum (CS-GG) polymer blend matrix. The developed silica NCs were characterized by FTIR, SEM–EDS, XRD, TGA, and BET. The results confirmed the dispersion of silica NPs on the surface of the CS: GG blend resulting in silica NCs with improved thermal stability, and an enhanced specific pore surface area from 11.843 m 2 /g to 23.029 m 2 /g. The 2 and 5% silica NCs were used as an efficient adsorbent for the removal of mercury ions. The 2 and 5% of silica NCs showed a maximum removal efficiency of 88% and 79% for mercury ions, respectively. The adsorption process is best fitted with the Langmuir adsorption isotherm and pseudo-second-order kinetic model. The adsorbent proved to be economical with 72% of removal efficiency after five cycles using EDTA as a desorbing solution.