Synthesis and Characterization of Silica-Based Adsorbents Employing Maize Stalks as Porogenic Agents and Their Application in Phenol Removal

Silica-based materials modified with maize stalks were synthesized using different sol-gel routes (acid-catalyzed route, base-catalyzed route, acid-catalyzed followed by base-catalyzed (two steps) hydrolytic route, and FeCl₃-catalyzed nonhydrolytic route). The porogenic role of maize stalks as templates was evaluated by comparing the effects of thermal and ultrasonic extraction methods. The resulting adsorbents were characterized via a set of complementary techniques, including nitrogen adsorption/desorption (BET), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and elemental analysis (CHN). The texture, structure, and morphology of the resulting materials were shown to be dependent on the synthesis route. The sorbent material produced via the two-step route followed by ultrasound extraction had the highest adsorption capacity, which allowed the removal of 28% (q = 0.84 mg g⁻¹) of the phenol from the aqueous solution.