Development of a Production Method for Palladium Micrometer-Sized Particles Using DMSO Solvent Containing CuCl₂

Abstract

A novel method to produce palladium micrometer-sized particles is presented. This method consists of the leaching of palladium using dimethyl sulfoxide (DMSO) solution containing CuCl 2 and NaCl followed by the precipitation with citric acid aqueous solution. Precisely, palladium was dissolved in a DMSO solution containing 0.1-0.2 M of CuCl 2 and 0-0.2 M of NaCl at 343 K. The dissolved palladium was precipitated by the addition of a citric acid aqueous solution, and the dried precipitates were imaged using standard SEM. We obtained micrometer-sized particles: angular particles were formed by the addition of 0.1-0.5 M citric acid aqueous solution while spherical particles by 1.0-2.0 M citric acid solution. The maximum recovery efficiency of palladium was 76.1％ and purity of palladium was 92.5 mass％. To investigate the mechanism of particle formation, in-situ monitoring of the formations of palladium particles in the liquid phase was conducted using atmospheric scanning electron microscopy (ASEM). The monitoring revealed that palladium particles form coral-like branching strings in the liquid phase. Comparison with dried spherical particles suggests that the stings were changed into spherical shapes during drying.