Development and characterization of bentonite – activated carbon composite from rice husk for enhanced H₂S gas adsorption

Abstract

Hydrogen sulfide (H₂S) is a major impurity in biogas that must be efficiently removed to prevent corrosion and environmental pollution. This study investigates the synthesis and adsorption performance of bentonite-rice husk activated carbon (SRH@Ben) composites for H₂S removal. The composites were prepared under varying thermal and chemical activation conditions, and their structural, morphological, and chemical properties were characterized using optical microscopy, field-emission scanning electron microscopy (FE-SEM), Energy-Dispersive X-ray Spectroscopy (EDS) and X-ray diffraction (XRD). The results indicate that both activation temperature and rice husk content significantly influence adsorption capacity, with the optimal composite (SRH@Ben 50%-450°C) achieving an H₂S adsorption capacity of 2.23 mg/g. Further chemical activation with KOH enhanced the adsorption capacity to 2.34 mg/g due to increased porosity and surface functionality. Comparative analysis demonstrated that SRH@Ben composites outperformed commercial carbon-based adsorbents (1.18 mg/g) and exhibited comparable efficiency to iron oxide-based materials (2.46 mg/g). These findings highlight the potential of SRH@Ben composites as a cost-effective and sustainable alternative for biogas purification.