Upcycling of Wool Keratin for Selective Recovery of Gold from Aqueous Solution

Abstract

The demand for gold recovery from e-waste is steadily increasing, and thus the design and preparation of efficient adsorbents for gold recovery is of great environmental and economic importance. This study explored wool keratin (WK) waste, an S-containing natural protein resource, as well as cellulose to fabricate functional adsorbents for selective gold recovery, based on the strong affinity of S element to gold. WK and cellulose were firstly dissolved simultaneously in ether-functionalized protic ILs by a hydrogen-bonding-acceptor strengthening strategy, and rheological research revealed that the ratio of WK/cellulose, concentration and test temperature had important influences on the rheological properties of WK/cellulose/[DBNH][Mea] solutions. WK/cellulose composite aerogels were prepared by a simple sol-gel transition process and followed by freeze-drying technique, and were systematically characterized by solid state nuclear magnetic resonance (SSNMR), FTIR, XRD, TGA, SEM and elemental analysis. The optimal W60C40 aerogel had excellent adsorption capacity (330.8 mg/g) and adsorption selectivity for Au(III), and good recoverability with a high recovery rate (94%) of gold after five times of reuse, providing a new and efficient type of bio-based adsorbent for gold recovery via an environmentally friendly and economically feasible approach.

Keywords: wool keratin, renewable sources, protic ionic liquids, composite aerogels, selective recovery of gold