Green functionalization of Arachis hypogaea shells via Aspergillus-mediated SSF for efficient Pb(II) removal: Kinetics, mechanism and economic evaluation

A novel eco-friendly adsorbent was developed by modifying Arachis hypogaea (groundnut) shells using Aspergillus niger mediated solid-state fermentation (SSF). The SSF technique is a unique, cost-effective, and environmentally friendly method to improve the structural properties of the adsorbent. This green functionalization enhanced the adsorptive performance without chemical treatment. Characterization through FTIR and SEM revealed the introduction of active functional groups and increased porosity. The maximum Pb(II) removal capacity of fermented groundnut shell (FGS) reached 36.82 mg/g at pH 5.0, outperforming the raw shell (3.53 mg/g). Adsorption followed the Langmuir isotherm and pseudo-second-order kinetics, with film diffusion as the primary mechanism. Thermodynamic analysis indicated spontaneous and endothermic adsorption, while regeneration studies showed over 30% efficiency retention after two cycles. The process reduced treatment cost by over tenfold. Furthermore, the treatment of raw industrial effluent also shows significant decreases during the batch adsorption process. This study offers a sustainable alternative for heavy metal remediation using agro-waste and fungal biotechnology.