Synthesis, characterization and adsorption studies of amino functionalized silica nano hollow sphere as an efficient adsorbent for removal of imidacloprid pesticide

Abstract

In the present research, silica nano hollow sphere (SNHS) and amino functionalized silica nano hollow sphere (SNHS-NH2) adsorbents have been used to remove imidacloprid as a high consumption pesticides from aqueous solutions. SNHS and SNHS-NH2 have been synthesized based on our previously reported methods. FT-IR and SEM techniques have been employed to analyze physicochemical characteristics of produced adsorbents. The adsorption of imidacloprid has been evaluated in terms of kinetic and equilibrium on used different synthesized adsorbents. The adsorption tests were performed in various conditions, in addition to assess the effects of pH, temperature and adsorbent dosage. Equilibrium empirical data have been fitted by Langmuir, Sips, Freundlich, Toth, Khan, Tempkin and Redlich-Peterson isotherms. Correlation coefficients demonstrated that equilibrium data were better matched with the Redlich-Peterson (R-P) isotherm. On the other hand, experiments showed that the amount of adsorbate per unit mass of adsorbent is decreased by increasing of the pH, and the maximum value of qe is obtained in acidic pH. In addition, the amount of adsorbate per unit mass of adsorbent is reduced by rising temperature and the equilibrium adsorption is dropped by increasing the amount of silica adsorbent. Kinetic data have been fitted with Elovich, pseudo-first-order and pseudo-second-order models; according to the obtained correlation coefficients. It can be stated that the pseudo-first-order model is more suited to the kinetic data related to pesticide adsorption on silica adsorbent. Kinetics of imidacloprid adsorption has been investigated at the concentrations of 7.2 mg/L and 10 mg/L. The results demonstrated that the equilibrium rate slope become much steeper in the initial times by increasing concentrations of imidacloprid.