Efficient and selective recovery of gold and palladium by simple and easily synthesized polyethylenimine based polymer

Polyethylenimine (PEI) crosslinked by 5,5-dithiodisalicylic acid (TDSA) is prepared through solution polymerization and serves as an adsorbent (TDSA@PEI) for the effective adsorption of Au(III) and Pd(II). TDSA@PEI exhibits excellent adsorption performance for Au(III) in a wide pH range of 3–10. The maximum adsorption capacity of TDSA@PEI for Au(III) and Pd(II) is 2579 mg/g and 808 mg/g at 25 °C, respectively. The adsorption isotherms of the two precious metals by TDSA@PEI are more fitted well by the Langmuir model. Meanwhile, TDSA@PEI exhibits excellent selectivity and reusability for Au(III) and Pd(II) adsorption. The adsorption equilibrium was reached at 5 min for 9.8 mg/L of Pd(II), and the adsorption kinetics of both Au(III) and Pd(II) are in accordance with the pseudo-second-order kinetic model. The adsorption of Au(III) and Pd(II) by TDSA@PEI is a spontaneous, endothermic and entropy increasing process. In addition, the column separation approach proves the great applicability of TDSA@PEI in industry. The abundant amino, thioether and hydroxyl groups in TDSA@PEI are responsible for its superior performance, forming several types of interactions with Au(III) and Pd(II) ions such as electrostatic interactions, chelation and redox.