Gallic acid-functionalized chitosan composite for efficient removal of hexavalent chromium in aqueous

To address the pH limitations of traditional Cr(VI) adsorbents, converting Cr(VI) anions into the more stable Cr(III) cations through a reduction reaction is an effective strategy. Therefore, in this study, gallic acid (GA), with a high redox potential, was selected as the reducing agent, together with chitosan (CS) as the substrate, and sodium alginate (SA) as the gelling agent. A novel SCG composite material was successfully prepared using the sol-gel crosslinking method, which efficiently captured and reduced Cr(VI) while immobilizing Cr(III). At pH = 4, t  = 150 min, and T  = 30 °C, 1 g/L of SCG can remove 94.7 % of Cr(VI), with a reduction rate of 67.5 %, achieving efficient and stable Cr(VI) removal over a wide pH range. Furthermore, the SCG material demonstrated good pH adaptability (It can still remove 84 % of Cr(VI) at pH = 7) and practical applicability. Comparative experiments and DFT calculation results showed that the introduction of GA not only helped form a more compact network structure but also interacted synergistically with CS, significantly promoting the removal of Cr(VI). In conclusion, the SCG composite material provides a new approach for the treatment of Cr(VI)-contaminated wastewater.