Effect of Calcination Temperature and Impregnation Time on Physicochemical and Textural Properties of KOH-Modified Rice Husk Ash Materials

Rice husk ash (RHA) is a silica-rich agricultural byproduct with significant potential in the development of sustainable porous materials. This study investigated the effect of calcination temperature and impregnation duration on the physicochemical and textural properties of KOH-modified RHA materials. The method used was calcination at different temperatures (500, 600, and 700 °C) combined with KOH impregnation for 19, 22, and 24 h. The prepared materials were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX), Brunauer–Emmett–Teller (BET) surface analysis, and X-ray diffraction (XRD). FTIR analysis showed that increasing calcination temperature promoted the reduction in residual carbon-containing functional groups and enhanced the dominance of silica-related Si–O–Si vibrations. SEM observations revealed significant morphological evolution from heterogeneous fragmented structures at 500 °C to more interconnected porous frameworks at 600 °C, followed by partial densification and agglomeration at 700 °C. Semi-quantitative EDX analysis confirmed the silica-rich surface composition of the prepared materials, while XRD patterns indicated structural transformation from partially crystalline phases toward more stabilized silica-rich structures. BET analysis demonstrated that sample 2B, calcined at 600 °C with 22 h impregnation, exhibited the most favorable textural characteristics among the selected BET-analyzed samples, with the highest surface area and pore volume. Overall, calcination temperature and impregnation duration significantly influenced the structural evolution, pore development, and physicochemical characteristics of KOH-modified RHA materials. This study contributes to the development of sustainable biomass-derived materials and supports Sustainable Development Goal (SDG) 12, which is related to responsible consumption and production through the valorization of agricultural waste into value-added silica-rich materials.