Rice paper adsorbent for gold recovery

Growing global interest in gold (Au) has spurred the development of adsorption processes as sustainable technologies for effective Au recovery from industrial waste. However, the adsorbents used in such processes often require complex fabrication procedures and/or petroleum-based chemicals, aggravating economic and environmental burdens. To overcome these limitations, this study proposes the transformation of rice paper (RP), a biomass (starch)-based food material, into a high-performance Au adsorbent via facile aqueous-phase chemical modification (hydrazination). The resultant hydrazine-functionalized RP (Hz-RP) adsorbent features a stratified mesoporous structure and demonstrates high mechanical integrity in water. Hz-RP rapidly, effectively, and selectively recovers Au even in complex feed solutions (e.g., electronic waste leachate) via collaborative chemisorption and reduction, outperforming many Au adsorbents reported in the literature. Following Au adsorption, Hz-RP can be readily collected and calcined to obtain high-purity Au. System-level analyses indicate that a Hz-RP-based process to recover Au from discarded electronics is economically and environmentally beneficial. Thus, this study establishes a viable pathway toward a circular resource economy by demonstrating the sustainable recovery of Au from industrial waste and the valorization of biomass/food waste.