Alginate-based adsorbents with adjustable slit-shaped pore structure for selective removal of copper ions

Adopting effective and efficient techniques for the treatment of heavy metal pollution in water bodies plays an important role in guaranteeing the quality of water and the sustainable development of water resources. In this study, GO, MMT and SA were used as raw materials to compare the adsorption behaviors of three alginate-based adsorbents crosslinked with different valence metal ions (Ca²⁺, Fe³⁺ and Zr⁴⁺) on Cu(II). The aerogels were based on sodium alginate as the matrix material with unique slit-shaped pore structures formed by stacking effect of sheets and chemical bonding. It was found that the pore structures of the aerogels were denser and more orderly with the increase of the valence states of the crosslinked ions, and the affinity for Cu(II) in planar configuration was stronger. The Zr⁴⁺-GMSA aerogel had the maximum adsorption capacity of 126.68 mg/g and the K_d of Cu(II) was up to 50.80 L/g, which exhibited good preferential adsorption performance. The adsorption mechanism of Mⁿ⁺-GMSA aerogels on Cu(II) was mainly ionic exchange, surface complexation and physical adsorption, which was explored by combining XPS and EDS characterizations of Mⁿ⁺-GMSA before and after adsorption. This scheme can provide valuable and meaningful contribution to realize the selective recovery of Cu(II).