Facile one-step synthesis of CuZn-HDS/alginate hydrogel beads for highly efficient and selective removal of methyl orange

Hydroxy double salts (HDSs) have shown enormous potential for removing dyes from wastewater. However, the powder form of HDSs limits their potential in commercial applications. Herein, we proposed a facile one-step route to incorporate CuZn-HDS into the copper alginate matrix for methyl orange removal. This strategy could not only shape CuZn-HDS to beads but also significantly enhance the adsorption ability of the matrix. The obtained composite hydrogel beads displayed high water stability and excellent adsorption performance for MO, with more than 98% of MO being removed by CuZn-HDS/Alg-0.5. The maximum adsorption capacity of CuZn-HDS/Alg-0.5 for MO was 763.3 mg·g −1 at 298 K. Besides, the adsorption process matched the pseudo-second-order kinetic model and fitted well with the Freundlich model, suggesting that the adsorption of MO onto CuZn-HDS/Alg-0.5 was a multilayer chemical adsorption process. More importantly, CuZn-HDS/Alg-0.5 could selectively adsorb MO from MO & RhB (Rhodamine B) and MO & MB (Methylene blue) mixed solution. Mechanism studies indicated that the removal of MO was attributed to the electrostatic interaction, complexation interaction and ion exchange interaction between MO and CuZn-HDS/Alg-0.5. This work opens a new route for developing eco-friendly and efficient adsorbents to remove dyes from wastewater.