Hybrid palm kernel shell activated carbon–Xerogel adsorbents for efficient SO 2 capture: Synthesis, characterization, and process optimization

Sulfur dioxide (SO2), a colorless gas with a distinctive pungent odor, is a significant air pollutant, primarily released from industrial processes and fossil fuel combustion. Its high reactivity and environmental impact, including contributions to acid rain, necessitate efficient capture and storage solutions. This study also aims to optimize SO2 adsorption by investigating the effects of flow rate, adsorbent weight, and contact time using Box-Behnken design within response surface methodology, as well as to evaluate the performance of individual (PKSAC, PKSX) and hybrid (PKSACX) adsorbents at various blending ratios to maximize removal efficiency. To overcome the limitations of each material individually, a blended series of PKSAC and PKSX was introduced to enhance SO2 adsorption efficiency. The Response Surface Methodology (RSM) with Box Behnken Composite Design (BBD) was employed to optimize two critical parameters: contact time and gas flow rate. Experimental findings showed that adsorption efficiency was maximized at lower flow rates and longer contact times, with the PKSACX blend achieving superior removal rates at optimal conditions. Statistical validation via ANOVA and visualization through contour and 3D surface plots highlighted significant parameter interactions, demonstrating that the 70:30 Xerogel-to-activated carbon blend achieved the highest SO2 removal efficiency. These results confirm the effectiveness of RSM-BBD in identifying optimal operating conditions and underscore the potential of PKSACX as a robust, sustainable adsorbent in industrial desulfurization processes. The removal efficiency of sulfur dioxide SO2 was significantly influenced by the blending ratio of palm kernel shell xerogel (PKSX) and palm kernel shell activated carbon (PKSAC). Among the investigated compositions, the PKSACX blend with a PKSX:PKSAC ratio of 70:30 exhibited the highest removal efficiency of 91%, surpassing the individual performances of PKSAC (84%) and PKSX (86%). This enhanced adsorption performance suggests a synergistic interaction between the porous carbon structure of PKSAC and the gel-based matrix of PKSX, which likely promotes improved surface accessibility and gas-solid interactions. A gradual decrease in removal efficiency was observed as the proportion of PKSAC increased, indicating that an optimal balance between the two components is critical for maximizing adsorption efficiency.