Investigating the Modified Silica Aerogel Removal Efficiency on Removing the Heavy Metals from Aqueous Solutions

Silica aerogel is the nano-porous form silica which is the lightest synthetic solid material. Some specific properties of this material include high surface area (1500 m2.g-1), low density (< 0.03 g.cm-3) and high porosity (%99). In this research, silica aerogel was investigated as an adsorbent of the heavy metal cations in aqueous solutions. The silica aerogel was synthesized by sol-gel method and its surface was modified by Amino propyl triethoxy silane. The modified silica aerogels was studied by SEM and BET techniques. Then its sorbent ability on Pb2+, Cd2+, Zn2+ and Ni2+ cations was investigated. Finally the effective parameters on adsorption of the heavy metals such as pH (2-12), Contact time (0-48 h), adsorbent amount (0-1.5 g) and cation concentration (0-500 ppm) were investigated. optimum adsorption for all cations except cadmium occurred at pH=6 but this adsorption for cadmium occurred at pH=8. Optimum contact time to absorb all the studied cations is equal to 24 hours. Assessing Langmuir and Freundlich isotherms showed that data obtained from the studied cations matches with both isotherms. The highest adsorption capacity of adsorbent for Pb2+, Cd2+, Ni2+ and Zn2+ were respectively 45.45 g, 35.71 g, 40.00 g and 34.48 g per mg of adsorbent. In general, the results of the conducted experiments indicate that the cations have high adsorb ability by the modified silica aerogel and it can be used in the municipal and industrial water and wastewater treatment.