Experimental study of lead (II) removal using polymorphous silica adsorbents

Adsorption of lead(II) as a major heavy metal pollutant onto nano-adsorbents of Andalusite, Kyanite and Sillimanite was studied in a batch system. Nano­-adsorbents were prepared via crushing, using a planetary ball mill and then characterized by different analyses such as: SEM, XRD, XRF and FT-IR. Major factors affecting the adsorption process were studied including pH, adsorbents dosage, initial metal concentration and temperature. Afterward, the adsorption process was studied isothermally, kinetically, and thermodynamically. The results show that aluminum silicates polymorphs are efficient adsorbents for removal of lead(II) and the removal exceeds 90%. The Freundlich isotherm model was best fitted with the experimental data. Chemisorption may control the rate of adsorption due to following the pseudo-second-order kinetic model. Thermodynamic investigation proved low randomness, exothermic and spontaneous nature of the process.