Redox active metallene anchored amino-functionalized cellulose composite for electrochemical capture and conversion of chromium

Considering the ubiquity and high toxicity of Cr(VI) species for destroying a sustainable environment, developing energy-efficient method for capturing and detoxifying chromium [Cr(VI) → Cr(III)] is imperative. Herein, ferrocene (Fc) was combined with carboxymethyl cellulose (CMC) and polyethyleneimine (PEI) for Cr(VI) remediation. Fc species possessed reversible redox behavior and low ionization potential, yet it faced challenges with conductivity and stability. Results revealed that, PEI facilitated the binding of Fc within the CMC through electrostatic interactions or coordination bonds, ensuring the good dispersion and stability of Fc. When applied in the electrochemical adsorption of Cr(VI), the combination created a synergistic effect. The presence of Fc and PEI boosted the electrochemical performance by providing faster electronic and ionic transportation, higher specific capacitance coupled with improved electrode-electrolyte interactions, leading to a higher Cr(VI) adsorption capacity over CMC/PEI/Fc (280.5 mg/g) compared to those over CMC and CMC/PEI. The interactions between the Cr(VI) and electrode included the electrosorption, electrostatic interaction of protonated PEI and oxidized Fc species. When the electric field was reversed, the Cr(VI) was electrostatic repulsed and electrocatalytic reduced to Cr(III) with a reduction rate of 85.4 %. This work promoted the development of effective electrosorption materials suitable for complete Cr(VI) removal and detoxification.