Synthesis and characterization of mesoporous activated carbon derived from Sapindus seeds hulls

This study demonstrates a novel, low-temperature coupled chemical-physical activation strategy to valorise carbon (AC) featuring a mixed micro-mesoporous architecture. The synthesis utilises an optimised two-step process: initial chemical activation with concentrated sulfuric acid (H2SO4) followed by low-energy argon-atmosphere pyrolysis at 500°C. Comprehensive material characterisation was conducted by way of proximate analysis, thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy. The optimised biomass-derived AC exhibited a high char yield of 47.3%, an enhanced elemental carbon content of 70.6%, a moisture content of 4.31%, and an ash content of 6.08%. Gas adsorption diagnostics revealed a functional Brunauer–Emmett–Teller specific surface area of 241.91 m2/g (Langmuir surface area of 361.41 m2/g). Notably, an average pore diameter of 32.42 Å confirms a prominent mesoporous volume fraction well-suited for targeting macromolecular adsorbates. Liquid-phase batch adsorption assays further validated the practical utility of the material, showing rapid initial kinetics for organic dye removal. This approach offers a sustainable, cost-effective framework for agricultural waste valorisation while producing tailored porous matrices for environmental engineering applications.