Gold recovery from E-waste using freestanding nanopapers of cellulose and ionic covalent organic frameworks

The ever-increasing production of electronic devices generates a huge amount of electronic waste (E-waste). Therefore, there is an urgent need for advanced recycling technology for E-waste that provides both economic and environmental benefits. Herein, we describe the preparation of flexible, freestanding CF-COF nanopapers consisting of cellulose fibers (CFs) and guanidinium-based ionic covalent organic framework (COF) that can be used for recovering gold from E-waste leaching solutions via a membrane separation technique. Due to the synergetic effects of physical adsorption, ion exchange and chemical reduction, the COF has an extremely high capture capacity (up to 1,794 mg of Au per gram of COF), is highly selective and has fast kinetics for adsorbing trace amounts of [AuCl4]- in aqueous solution. The high COF loadings (similar to 50 wt%) and hierarchical porosity of the CF-COF nanopapers resulted in excellent performance when capturing gold species from the E-waste leaching solution. This study provides new possibilities for developing sustainable membrane materials, and highly efficient and cost-effective techniques for the recovery of precious metals from E-waste.