Recovery of palladium from solution by defective Carbon nitride and Regenerating as a hydrogenation catalysis

The recycling of precious materials, such as palladium (Pd), was repeatedly documented as essential for a sustainable future with respect to the environment and energy production. However, high-efficiency extraction presented significant challenges. In this work, a surface hydroxyl regulation strategy was used to prepare a defective carbon nitride (CN) with a high specific surface area and hierarchical porosity through cobalt (Co)-doping. Characterization confirmed the successful synthesis of the adsorbent. The results indicated that the optimal pH for the adsorption process was 5.5, adsorption kinetics and isotherms of Pd on the adsorbent suggested that the adsorption followed a pseudo-second-order model and the Langmuir model, respectively. The maximum adsorption capacity reached up to 529.1 mg·g^–1. In addition, it showed high affinity for Pd ions, the K_d value was 4.1 × 10⁴ ml·g^–1. After Pd adsorption, due to the presence of abundant and uniformly dispersed Pd and Co particles which further facilitated cooperative catalysis on the surface of adsorbent, As a result, the Co-CN-Pd was reused as a catalyst for p-nitrophenol hydrogenation. It achieved a turnover frequency (TOF) as high as 1032.6 h^–1, significantly surpassing other catalysts reported in the literature. Overall, this novel adsorbent presented broad application prospects in the field of Pd recovery and reuse.