Selective extraction of gold from strong acid E-waste leachate through H+-triggered cascade reaction of thiolated β-cyclodextrin

Recycling precious metals from the increasing amount of e-waste is significant for the sustainability of strategic metal resources. However, few technologies have been reported for efficient and highly selective recovery of precious metals from the strong acidic e-waste leachate. Herein, we demonstrated a simply synthesized thiolated beta-cyclodextrin (T-CD) that can recover gold from multi-metal coexistence solutions at pH 2 with an exceptional adsorption capacity of 1890.98 mg/g, and a superior selectivity coefficient about 5x10(4). The recognition of Au3+ by sulfhydryl groups on T-CD and the hydrolysis of T-CD triggered by H+ were proved to be the critically important contributors to the highly selective recovery of gold from strong acid wastewater. In addition, T-CD can directly and effectively extract gold from actual waste PCB leachate, allowing the acidic solution to be recycled five times. This work provides a new guidance for the direct recovery of rare metals from strongly acidic wastewater.