Valorization of pineapple leaf waste into Fe-Modified biochar for efficient H2S adsorption.

Thailand generates large amounts of agricultural residues, particularly pineapple leaves (PAL), which are often underutilized. In this study, pineapple leaf-derived biochar (PALC) was developed as an efficient hydrogen sulfide (H2S) adsorbent via FeCl3 pretreatment and pyrolysis under oxygen-free conditions at 400-800°C, with PAL-to-Fe mass ratios of 0.5-3. The adsorption performance was governed by pore structure and iron species, both influenced by pyrolysis temperature and Fe loading. The optimal material, 2Fe/PALC600, dominated by Fe3O4, achieved the highest adsorption capacity of 380.1 ± 15.4 mg H2S g-1 under 40%RH conditions. While humidity enhanced H2S removal, the presence of 40%v/v CO2 significantly suppressed performance due to competitive surface physisorption. X-ray photoelectron spectroscopy (XPS) analysis revealed transformations of Fe species on the biochar surface before and after H2S exposure, and density functional theory (DFT) calculations provided further insights into the adsorption mechanism. These findings highlight the strong potential of Fe-modified PAL-derived biochar as a sustainable and cost-effective material for gas purification, while also valorizing agricultural waste.