Facile fabrication of Cu_xS_y/Carbon composites using lignosulfonate for efficient palladium recovery under strong acidic conditions

The recovery of noble metals from aqueous systems is of great significance for constructing sustainable framework of modern industry yet remains challenging. Herein, Cu_xS_y/Carbon composites with superior thermal stability and adsorption capacity were successfully synthesized via one-pot hydrothermal method using lignosulfonate as dual role of raw materials. The optimal synthesis conditions were investigated via tailoring the temperature and the mass ratio of reagents. The morphologies and physical properties of the composites were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The surface chemistry was analyzed by Zeta potential analysis, Brunauer-Emmet-Teller (BET), and X-ray photoelectron spectroscopy (XPS). The Langmuir model and the pseudo-second-order model well described the adsorption of Pd(II) and Pd(IV) delivered by fabricated composites. The adsorption capacity obtained from Langmuir isotherm model towards Pd(IV) was 114 mg/g and Pd(II) was 101 mg/g, respectively. More importantly, the adsorbed palladium species could be desorbed with hydrochloric acid and thiourea, which suggested good durability and recycling performance of the typical composite. This work might provide a new guidance for the utilization of lignin or its derivatives and enriched the research in the field of noble metal recovery.