Ultrasonic-Assisted Amine Grafted on Super-Hydrophobic Silica Aerogel Derived from Pumice for Arsenate Adsorption

A highly stable and high-density amino group (6.54 µmol/m2 ) was loaded on super-hydrophobic silica aerogel derived from pumice by the ultrasonic method and used to remove arsenate (As). After ultrasonic amine grafting, the specific surface area did not change, as 832 m2 /g of a specific surface, a hole volume of 3.84 cm3 /g, and an average hole diameter of 12.39 nm were observable. The selected parameters were directly dependent on As adsorption (100% As removal at the pH rate of 6.85, reaction time of 120 minutes, and initial solute concentration of 95.21 µg/L based on multiple non-linear regression analyses). The kinetics of As adsorption was best explained by the pseudo-first-order kinetic, which is proof of the chemical adsorption mechanism. The heterogeneous surface with multilayer adsorption sites for As adsorption was obtained from various isotherm models. The maximum uptake capacity of 42.2 mg/g was observed based on the Khan model. The spent adsorbent was successfully regenerated and reused by HCl, but a substantial reduction in adsorption capacity was detected after five regeneration-reuse cycles. Based on the results, the ultrasonic method was found to be more effective, economical, and environmentally friendly compared to conventional sol-gel methods for the surface amine functionalization of silica aerogel to remove As from the aqueous solution.