Magnetic chitosan-functionalized bone char for efficient removal of anionic dyes: Insights into adsorption-enhanced...

Dyes are persistent organic pollutants that can bioaccumulate and present serious environmental challenges. The study fabricates a new adsorbent, magnetic chitosan-functionalized bone char (CsFeBC), co-doped with chitosan (Cs), Fe₃O₄, and bone char (BC) to enhance the removal of anionic dyes (Sunset Yellow [SY] and Reactive Blue 19 [RB19]). One-factor experiments showed that CsFeBC exhibits excellent adsorption capacity and a considerably higher removal efficiency. Remarkably, for SY, the removal efficiency of CsFeBC increased by 223.03 % compared to BC. Although the BET-specific surface area and ash content of CsFeBC are smaller than BC, it has a higher acidic oxygen-containing functional group content and electrical conductivity. Therefore, CsFeBC adsorption performance improves mainly due to strong electrostatic attractions. In addition, hydrogen bonding, ionic bonding, and esterification reactions occur between the hydroxyl (-OH) and amino (-NH₂) functional groups introduced by Cs in CsFeBC and the sulfonic acid groups (-SO₃^-) in SY and RB19. Furthermore, CsFeBC performs effectively in a competitive environment where SY and RB19 coexist. Overall, CsFeBC demonstrates the potential of being an effective adsorbent for removing anionic dyes, providing a promising solution for reducing environmental pollution caused by ionic organic compounds.