Optimizing the synthesis of nanostructured SiO2 from Ethiopian pumice for use in rubber reinforcement

This study investigated the optimization of synthesis parameters for producing nanostructured SiO₂ from Ethiopian pumice for use as rubber reinforcement. Important variables such as pH, sol‒gel synthesis temperature, stirring rate, calcination temperature, sodium silicate modulus, NaOH concentration, and H₂SO₄ concentration were systematically varied. FTIR, XRD, BET, TGA, and SEM were used to characterize the resulting SiO₂ and assess how these parameters affect its morphological, surface, thermal, and structural properties. According to BET analysis, a sodium silicate modulus of 3-4 produced the best results. FTIR and BET tests showed that H₂SO₄ concentrations of 2 M and 2.5 M were ideal, while NaOH concentrations of 2 M and 3 M were optimal based on BET and XRD analyses. The best silica was obtained within a synthesis temperature range of 70-90 °C, as indicated by XRD, FTIR, and SEM investigations and pH values between 8 and 10 were confirmed by XRD and SEM to be suitable. TGA revealed that the ideal calcination temperature ranged from 600 °C to 800 °C, while SEM showed that the best stirring rate was 600 rpm. These studies confirm that the characteristics of Ethiopian pumice-derived SiO₂ for rubber reinforcement are strongly influenced by the optimized synthesis conditions.