With increasing attention on environmental impacts and sustainable development, the conversion of underutilised bagasse (BG) or low-value fibre waste into biosorbents has considerable potential applications. In this study, BG carboxymethyl cellulose (BGCMC) with a high degree of substitution (DS) was prepared by controlling the ratio of monochloroacetic acid (MCA) and sodium hydroxide to BG cellulose. BGCMC aerogels (BCGel) were obtained using the crosslinking reaction of citric acid (CA) with hypophosphite sodium (HPS) as a catalyst. The adsorption results were more suitable to be described by the Langmuir isotherm (R² > 0.99), with maximum adsorption capacities of BC₃Gel for Pb(II) and MB of 353.36 and 1260.9 mg g⁻¹, respectively. Additionally, after treatment with 50% alcohol or 0.05 M EDTA solution, BCGel exhibited satisfactory removal performance even after five regeneration cycles. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectrometry (EDS) results demonstrated that cationic exchange and electrostatic interaction were the main Pb(II) and MB adsorption mechanism. The adsorption mechanism of BCGel for pollutants involves the interaction of multiple adsorption forms. The excellent Pb(II) and MB adsorption capacities of BCGel provide another avenue for the recycling of waste BG in the wastewater treatment field.