Advanced bis-thiourea polymer resins for efficient gold (III) recovery.

Building upon our previous studies on gold recovery, this work presents an enhanced approach for the selective extraction of gold (Au(III)) from secondary sources using solid-liquid extraction. In light of the economic value attributed to gold, in addition to its distinctive properties and the increasing demand for it, the effective recycling of gold from waste streams becomes a matter of significant importance. Among various recovery techniques, solid-phase extraction offers notable advantages in terms of selectivity and reusability. In this study, we further develop and optimize chelating resins synthesized via alkaline polycondensation of two thiourea-functionalized phenolic monomers with formaldehyde. The resulting formo-phenolic bis-thiourea polymers were evaluated for their gold-binding performance. Sorption experiments demonstrated significantly improved gold uptake capacities of 710 and 833 mg/g, respectively. Moreover, sorption selectivity experiments indicated strong preferential binding of Au(III) even in the presence of competing metal ions such as Pd(II), Ru(III), Rh(III), Pt(II), Zn(II), Cu(II), Ni(II), Fe(II), and Al(III). These findings confirm that the developed chelating resins offer a high-capacity and highly selective platform for the recovery of gold, representing an advancement over our earlier work.