Adsorption and aggregation of Cu²⁺ on carboxymethylated sugarcane bagasse: Adsorption behavior and mechanism

Abundant biomass resources provide us with sufficient material basis, while a large amount of bio-waste is also produced and the high-value utilization of bio-waste is still highly desirable. Herein, we reported a facile one-pot fabrication approach towards efficient utilization of sugarcane bagasse via carboxymethylation to adsorb and recycle Cu²⁺ ions. The modified sugarcane bagasse possessed outstanding adsorption efficiency, with a maximum capacity of 263.7 mg g^-1, owing to the functional groups such as carboxyl and hydroxyl groups, as well as aromatic structure. It was noted that the carboxymethylated sugarcane bagasse (MSB40) swelled rapidly when suffering Cu²⁺ ions solution, and more adsorption sites were available since the physical diffusion barrier was removed, thereby enhancing the absorption capacity. Interestingly, Cu²⁺ ions could induce the aggregation of MSB40 due to the Cu²⁺ ions compress colloid double layer, neutralizes surface charges, which benefited the following separation process. Ultimately, copper oxide was recovered and the purity reached 97.9%. Additionally, in the presence of both Ca²⁺ and Mg²⁺ ions, MSB40 exhibited excellent selectivity for the adsorption of Cu²⁺ ions. This strategy offers a facile and novel clue for the high-value utilization of bio-waste and the recovery of copper for biomaterial and environmental applications.