Selective Adsorption of Heavy Metals by Renewable Complexing Polymer

In this study, a novel material obtained from shredded maize stalk (MS) was functionalized using Alizarine Red S (ArS), a complexing agent that contains -OH and -C=O groups in its structure (MS-ArS). The obtained material MS-ArS was employed in adsorption experiments for Mn²⁺, Pb²⁺, Cu²⁺, Cr³⁺, Zn²⁺ and Fe³⁺ (Mⁿ⁺) removal. Initially, complex formation between (Mⁿ⁺) and ArS in buffer solution at pH 4 and 10 was investigated using UV-Vis spectrometric method. The functionalization process of MS was done at pH = 2, 4, 6, 8, and 10. The results showed that the best functionalization was obtained at pH=2. After functionalization study, Mⁿ⁺ adsorption onto MS-ArS at pH 4 and 10 was tested. Mⁿ⁺ adsorption proved to be pH dependent. It was observed that pH=10 was the optimum medium for Mⁿ⁺ adsorption. MS-ArS has affinity for Mⁿ⁺ in the following order Fe³⁺>Cu²⁺>Zn²⁺>Mn²⁺>Pb²⁺>Cr³⁺. The results demonstrate also remarkable desorption rates (D(%)) when 0.5 M HCl is used as regeneration solvent: 94% for Cu²⁺, 92.4% for Fe³⁺, 91.7% for Cr³⁺, 90.8% for Zn²⁺, 90.3% for Pb²⁺, and 86.1% for Mn²⁺. These findings highlight the potential of this sustainable material for effective adsorption and recovery of the complexing material in order to respect the principle of circular economy approach.