Structural regulation of alginate-based adsorbents based on different coordination configurations of metal ions and selective adsorption of copper ion

To tackle the problem of developing efficient adsorbents for the selective removal of copper ions from wastewater, this investigation focused on the synthesis of Fe-GO/MMT/SA and Al-GO/MMT/SA copper ion adsorbent materials (Fe-GMS and Al-GMS), respectively, by merging two distinct metal ions (Fe(III) and Al(III)) with sodium alginate (SA), graphene oxide (GO), and montmorillonite (MMT). By introducing metal ions with different coordination configurations, the slit structure and pore density of the adsorbents can be effectively controlled, thereby enhancing the selectivity for copper ion adsorption. The results show that Fe-GMS has excellent adsorption capacity for Cu(II) compared with Al(III), and the adsorption capacity and distribution coefficient are 116.44 mg/g and 14.45 L/g, respectively, which is mainly due to the octahedral coordination configuration of Fe(III) having more coordination points when cross-linked with SA, forming a more complex and closer slit structure and cross-linked network. This result was further verified by density functional theory (DFT). Therefore, Fe-GMS stands as a promising Cu(II)-selective adsorbent, offering a valuable framework for the rational design of alginate-based aerogel adsorbents suitable for wastewater treatment applications.