Reusable Porous SiO₂ for Methylene Blue Removal: A Study on Adsorption and Regeneration Cycles

In response to the water contamination problem, this study presents a novel method to remove methylene blue (MB), a typical water pollutant, using synthesized porous silicon dioxide (SiO₂). The SiO₂ was synthesized via a cost-effective sol–gel method and characterized for its thermal stability, structural, textural, morphological properties, and elemental composition using techniques such as TGA, FT-IR, XRD, BET-BJH, SEM, TEM, and STEM-EDS. A unique aspect of this study is the evaluation of SiO₂ reusability in MB removal through multiple adsorption and thermal regeneration cycles, a critical factor for practical applications. The results demonstrated the successful synthesis of thermally stable, amorphous, porous SiO₂ with a surface area of 811 m²g⁻¹ initially, reducing to 600 m²g⁻¹ after the adsorption and regeneration cycles, indicating its stability and durability. The removal efficiency of MB was consistent across cycles, achieving 71.19 ± 0.94%, 75.55 ± 0.69%, and 73.49 ± 0.15% after 20 min, and the adsorption capacity at equilibrium was 3.73 ± 0.025, 4.08 ± 0.045, and 3.48 ± 0.021 mg_MB g_ads⁻¹ during the first, second, and third cycles, respectively. These findings highlight the potential of the synthesized porous SiO₂ as a reusable and efficient adsorbent for MB removal in water treatment, contributing to the advancement of sustainable and effective solutions for water pollution.