Palladium recovery from electroplating wastewater by a binary separation process

Abstract

A binary separation method was proposed to recover palladium from wastewater and to deliver pure metallic palladium as a final product. Wastewater samples from electroplating plants contained ppb level of palladium and other metals, including copper, nickel, zinc, iron, etc. Palladium was first selectively recovered from the wastewater via precipitation by iodide ions, and the palladium precipitated was then reduced by L-ascorbic acid. The conditions for palladium recovery were optimised by adjusting the pH, temperature, and reagent dosage. Palladium could be separated from the wastewater a few seconds after the addition of iodide ion. By adding a slight excess amount of iodide ion, 100% palladium recovery was achievable from a solution of pH below 2.5, while no coprecipitation of other metals was observed within a pH range of 1-3. 100% palladium was recovered in a 15-min reduction reaction at 80℃, with quadruple the molarity of L-ascorbic acid compared to that of palladium. The recovered products after precipitation and reduction were analysed respectively, by X-ray photoelectron spectroscopy, Powdered X-ray Diffraction, Scanning electron microscopy, and Fourier-transform infrared spectroscopy. These characterisation methods confirmed that the palladium iodide was obtained from precipitation, and metallic palladium was obtained from reduction. Based on the obtained results, this method guaranteed a high recovery of pure palladium. Considering the minimal time and reagent amount required, this binary separation method is safe, straightforward, and practical for industrial application

Date of Award	2022
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Xijun HU (Supervisor)