Bamboo fiber-reinforced chitosan biomass aerogel for Cr(VI) and Cu(II) capture: Batch adsorption experiments and density functional theory calculations

The combination of bamboo fiber (BF) with chitosan (CS) in aerogels to capture heavy metals from contaminated water has not yet been previously reported. In this study, we used a straightforward sol–gel followed by freeze-drying method to fabricate a biomass composite aerogel using waste BF and CS (BF/CSA). This material is low-cost, eco-friendly, and recyclable. In particular, the BF/CSA-2 exhibited excellent mechanical strength and strong acid resistance. It effectively adsorbed Cr(VI) at pH=2 and Cu(II) at pH=5, achieving removal efficiencies of 94% and 85%, respectively. The corresponding maximum adsorption capacities were 162.10 and 138.97 mg/g. BF/CSA-2 exhibited a high removal efficiency (>70 %) after five consecutive reuse cycles. The chemisorption mechanism was confirmed through adsorption isotherms and kinetic analysis. In addition, density functional theory (DFT) calculations revealed adsorption energies of −196.473 and −121.964 kcal/mol for Cr(VI) and Cu(II), respectively, on BF/CSA-2. Based on experimental characterization and theoretical calculations, the removal mechanism involves complexation, electrostatic attraction, and reduction. This study presents a promising advancement toward the development of scalable and sustainable biomass-based aerogels for water purification.