Functionalizing natural wood and delignified wood into bio-adsorbents for removal of Cu²⁺ from water

Natural pinewood and delignified pinewood were functionalized into bio-adsorbent materials for water remediation, particularly for removing copper ions (Cu²⁺). Wood was functionalized by esterification with maleic anhydride and citric acid, which increased the content of carboxyl functional groups for the chelation of copper ions. The effects of wood delignification and functionalization on the bio-adsorbents’ adsorption capacity for copper ions in water were investigated. Cu²⁺ adsorption capacity and COOH grafting density showed an almost linear correlation with wood-based bio-adsorbents. Although the delignification of wood did not impact the adsorption capacity of the delignified wood functionalized with maleic anhydride, it significantly enhanced the Cu²⁺ adsorption capacity (attaining 0.22 mmol/g) of the delignified wood functionalized with citric acid (with a COOH content of 0.50 mmol/g). Moreover, the delignified wood functionalized with citric acid showed only a 10% loss in adsorption capacity after three regeneration cycles with acetic acid, showing a promising application as a bio-adsorbent material for the removal of copper ions from water. © The Author(s), under exclusive licence to Springer Nature B.V. 2023.