Bifunctional chitosan/tannin aerogel for gold recovery via electrostatic attraction and in-situ reduction

Enhancing gold recovery from wastewater significantly boosts resource efficiency and safeguards the environment. Addressing this need, we have proposed a straightforward and efficient one-step approach utilizing a multifunctional cellulose/chitosan/tannin aerogel (CCTG) to recover Au (III) through a combined adsorption-reduction mechanism. Under optimal conditions of pH 3 and 35 °C, our CCTG demonstrates a remarkable maximum adsorption capacity of 1761.6 mg·g^-¹ , swiftly reaching equilibrium within 80 min. The adsorption kinetics indicates a pseudo-second-order model, suggesting a rapid and efficient interaction. Further investigation into adsorption isotherms reveals that both higher initial Au concentrations and elevated temperatures facilitate the adsorption capacity, with the Langmuir model offering a superior fit, indicative of monolayer chemisorption verifying a testament to the selective and specific nature of the process. Remarkably, CCTG maintains its exceptional adsorptive capability across varying ionic strengths. In binary metal systems of Au(III) with Cu (II), Cd (II), Co (II), Ni (II), and Cr (III) respectively, CCTG displays a preferential affinity for Au (III). The underlying mechanism of this performance is a dual-action process: electrostatic attraction facilitated by chitosan and reductive capacity endowed by tannic acid. Our work presents a compelling strategy for the practical application of gold recovery from wastewater in an efficient and environmentally friendly manner.