Selective metal recovery by mucin: turning gold from wastewater into a peroxymonosulfate-activated catalyst

Abstract

The growing volumes of metal wastewater produced by industry require more efficient techniques for metal recovery. Biosorption is an attractive and desirable method for metal recovery because it avoids the additional chemicals beyond the sorbent. Mucin glycoprotein is a natural bioresource that can potentially adsorb and reduce precious metals. In this study, we examine the ability of mucin to recover gold from a mixed-metals solution in an acidic environment modeling industrial wastewater. We show that selectivity in the adsorption of the metals—and particularly precious metals—is driven by the metal's chemical properties and affinity to mucin. The ability of mucin to reduce gold ions and transform them into nanoparticles was also investigated both in mixed-metal solutions and isolated-metal solutions and with two different forms of mucin (dissolved and nanofibers). Lastly, the recovered gold NPs were used in persulfate activation for the oxidation of an organic pollutant: bisphenol A. This study illustrates a two-step circular-economy process—sorption of precious metals and utilizing those adsorbed metals for secondary decontamination—using the benign, cost-effective biomaterial mucin.