Hydrothermal Functionalization and Characterization of Bambusa vulgaris Biochar for High-Efficiency Electrostatic Adsorptive Removal of Reactive Black 5 Dye from Wastewater

Water pollution by synthetic dyes has become a serious environmental concern due to their toxicity, persistence, and widespread discharge from textile and related industries. Among these dyes, reactive black 5 (RB5) is commonly detected in industrial effluents and poses significant risks to aquatic ecosystems and human health. In this study, we investigated the adsorptive removal of RB5 from aqueous solutions using Bambusa vulgaris biochar modified with varying concentrations of ammonia. Bamboo biochar (BB) was prepared via pyrolysis and further functionalized using 20- and 30-mL ammonia treatments to produce B20 and B30, respectively. All prepared adsorbents were comprehensively characterized using SEM, BET, FTIR, TGA, CHN, XRD, and XPS to better understand their physicochemical properties. Adsorption studies systematically examined the effect of contact time, solution pH, adsorbent dose, and initial dye concentration. B20 and B30 exhibited consistently greater initial RB5 dye removal efficiencies (B20: 92.5%; B30: 89.8%) and rates compared to BB (75.2%), with optimum performance at acidic pH. Kinetics were best fitted to the Pseudo-First-Order model, but equilibrium data were best represented by the Langmuir isotherm model, confirming monolayer sorption. The recyclability of BB, B20, and B30 was tested for 8 successive adsorption-desorption cycle. The biochar modified by ammonia presented considerably enhanced recyclability and stability. B20 and B30 retained 67.8% and 66.2% of their initial efficiency, respectively, compared to BB's 48.5%. After-adsorption characterization was done using elemental analysis, FTIR, XRD, SEM, XPS, BET which confirmed RB5 adsorption. This study reveals the immense potential of ammonia-functionalized Bambusa vulgaris biochar, particularly B20, as a highly effective, reusable, and environmentally friendly adsorbent for the successful treatment of anionic dye-polluted textile wastewater.