Thiourea-formaldehyde-Functionalized Graphene Oxide for the Selective Removal of Copper from Multielement Solution

Copper (Cu), a critical raw material (CRMs) essential for renewable energy technologies, requires sustainable recovery strategies to ensure supply security and minimize environmental impacts. Recent market trends highlight the growing economic and strategic importance of Cu, reinforcing the need for selective recovery from secondary and waste-derived resources. However, Cu separation from complex waste streams, such as wind turbine leachates, remains challenging due to competition from base metals and rare earth elements. In this study, a thiourea-formaldehyde functionalized graphene oxide (G3DTF) is introduced as a new sulfur- and nitrogen-rich hybrid sorbent for selective Cu recovery under competitive conditions. Unlike conventional graphene-based materials, G3DTF incorporates tailored S/N donor sites within a graphene oxide framework, creating preferential coordination environments for Cu. The sorbent was evaluated in both monoelement and equimolar multielement solutions (100 μM of each element: boron, cobalt, copper, nickel, praseodymium, neodymium, gadolinium, dysprosium). Under optimized conditions, G3DTF achieved up to ≈99% Cu removal while exhibiting negligible uptake of competing ions. Langmuir isotherm analysis yielded a maximum adsorption capacity (q _max) of 23.4 mg g^-1, indicating strong affinity to Cu. Kinetic analysis revealed condition-dependent behavior. Copper adsorption followed pseudo-first-order kinetics in monoelement systems, whereas chemisorption became rate-limiting under competitive multielement matrices. Response surface optimization identified sorbent dosage as the dominant operational parameter, with optimal performance at 1.1 g L^-1 and pH 5.2, independent of salinity. XPS analysis confirmed that Cu-S governs selective binding. The performance of G3DTF in real leachate-mimicking systems further validated its selectivity and application potential. These results demonstrate the ability of G3DTF as a sustainable platform for selective Cu recovery from CRM-rich waste streams.