A New Approach of Complexing Polymers Used for the Removal of Cu²⁺ Ions

This study presents two modified polymers for Cu²⁺ ion removal from aqueous media. Shredded maize stalk (MC) and a strong-base anionic resin (SAX) were modified with indigo carmine (IC) in order to obtain two different complexing polymers, i.e., IC-MC and SAX-IC. Initially, the complex reaction between IC and Cu²⁺ in the solution was studied. Additionally, the complex formation Cu²⁺-IC in liquid solutions was evaluated at different pH ranges of 1.5, 4.0, 6.0, 8.0, and 10.0, respectively. For Cu²⁺ ions, adsorption onto the IC-MC and IC-SAX batch experiments were conducted. The contact time for evaluating the optimum adsorption for Cu²⁺ ions on the complexing materials was established at 1 h. Efficient Cu²⁺ ion adsorption on the IC-MC and SAX-IC at pH = 10 was achieved. The adsorption of Cu²⁺ ions depends on the quantity of IC retained on MC and SAX. At 2.63 mg IC/g MC(S4) and 22 mg IC/g SAX(SR2), a high amount of Cu²⁺ ion adsorption was reported. The highest adsorption capacity (Q) of IC-MC was obtained at 0.73 mg/g, and for IC-SAX, it was attained at 10.8 mg/g. Reusability experiments were performed using the HCl (0.5 M) solution. High regeneration and reusability studies of IC-MC and IC-SAX were confirmed, suggesting that they can be used many times to remove Cu²⁺ ions from aqueous matrices. Therefore, the development of complexing materials could be suitable for Cu²⁺ ion removal from wastewater.