Eco-innovation: using underutilized white bean straw and aluminum waste for dye removal

Abstract As environmental concerns about synthetic dyes increase, innovative and sustainable solutions become increasingly essential to mitigate their impact. In this study, a low-cost biosorbent, Al 2 O 3 @White Bean Straw, was synthesized for the removal of Alizarin Red S, a hazardous synthetic dye, from aqueous solutions. Nano-Al 2 O 3 was derived from waste aluminum cans and subsequently applied onto White Bean Straw to produce the proposed composite adsorbent. Batch experiments were conducted to compare the effectiveness of the raw White Bean Straw and the synthesized Al 2 O 3 @White Bean Straw as adsorbents. Raw White Bean Straw achieved a maximum Alizarin Red S removal percentage of 61.3% at optimum conditions of 0.05 g/L dosage, pH 10, a contact time of 120 min, and room temperature. On the other hand, for Al 2 O 3 @White Bean Straw, the maximum removal percentage of 80.12% was attained at the optimum conditions of 0.1 g/L dosage, pH 2, a contact time of 60 min, and room temperature. For both cases, the experimental data were analyzed for isotherm, kinetic, and thermodynamic determination. The results indicated that pseudo-second-order kinetics and the Freundlich isotherm were the best fits for the data. The findings of the analysis of the thermodynamic parameters for the process showed that the system was exothermic and spontaneous. Additional experiments were done on Al 2 O 3 @White Bean Straw in a continuous fixed-bed. The Adams-Bohart, Yoon-Nelson, and Thomas models all provided accurate fits to the adsorption behavior of Al 2 O 3 @White Bean Straw under various operating circumstances.