Self-Assembled Y₂O₃/Y(OH)₃ Heterojunction Nanosheets Hydrogel for Efficient Metal Resources Recovery

Hydrogels are innovative and efficient adsorbent for metal resource recovery owing to their three-dimensional porous network, abundant functional groups, and exceptional hydrophilicity. However, the fabrication of stable metal oxide hydrogels in aqueous media is severely hindered by rapid metal ion hydrolysis and unstable oxide-water interfaces, leading to structural disintegration. Here, we developed a two-step, solvent-mediated self-assembly strategy to fabricate a robust 3D Y₂O₃/Y(OH)₃ heterogeneous nanosheets hydrogel (3D-YHNH) for metal resource recovery. The 3D-YHNH shows exceptional adsorption performance, exhibits high capacities of 594.5 mg g^-1 for CrO₄ ^2- and 155.3 mg g^-1 for Au(III), coupled with ultra-rapid adsorption equilibrium kinetics achieved in 2 min. The 3D-YHNH demonstrated exceptional durability, retaining 99.2% of its initial capacity after 100 consecutive cycles. Combined experimental results and DFT calculations reveal that the exposure of active sites and formation of interfacial defects within 3D-YHNH generate substantial structural positive charges, resulting in enhanced electrostatic interactions with CrO₄ ^2- anions. Successful demonstration of kilogram-scale preparation, together with concentration factors up to 572.6 of Cr(VI) from wastewater and 48.20 of Au(III) from kilogram-scale e-waste, suggests that 3D-YHNH is compatible with industrial deployment. This finding paves the way for sustainable technologies for recovering valuable metals, directly supporting circular economy initiatives.