Sustainable hybrid activated carbon from banana peel and olive pomace for efficient removal of structurally diverse dyes

Introduction Agricultural-waste-derived activated carbons offer a sustainable alternative to conventional adsorbents; however, most studies rely on single biomass precursors and evaluate adsorption using only one model pollutant. Methods In this study, a hybrid activated carbon (HAC) derived from banana peel and olive pomace was developed and evaluated for the removal of four structurally distinct dyes: methylene blue (MB), methyl orange (MO), crystal violet (CV), and Eriochrome Black T (EBT). The effects of adsorbent dosage, pH, and contact time were investigated, followed by adsorption isotherm, kinetic, and regeneration analyses. Results An adsorbent dosage of 12 g/L and pH 2 provided the most favorable adsorption conditions. The hybrid activated carbon was found to have a high removal efficiency of 97.71% for MB, 98.41% for MO, 98.70% for CV, and 98.95% for EBT, respectively, under the optimized conditions to remove different dyes with different chemical structures. The equilibrium data were generally better described by the Langmuir model, while the adsorption kinetics showed stronger agreement with the pseudo-second-order model. HAC exhibited maximum adsorption capacities of 130.34, 99.70, 112.42, and 114.52 mg/g for MO, MB, CV, and EBT, respectively, with hybridization enhancing the adsorption capacities toward MO and EBT compared with the individual activated carbons. Regeneration experiments showed that HAC retained adsorption functionality after ten cycles, although removal efficiencies decreased to approximately 42%–56%. Discussion The results in this study validate the potential of olive pomace and banana peel-based hybrid activated carbon as a waste derived, reusable material for the removal of dyes from contaminated wastewater, thereby valorizing agricultural waste and promoting sustainable resource utilization.