The Effect of Shredding and Particle Size in Physical and Chemical Processing of Printed Circuit Boards Waste

Circuit boards present in most electric and electronic devices are very important components, which should be removed during sorting and dismantling operations in order to allow further adequate treatment for recovering valuable metals such as copper, nickel, zinc, lead, tin and rare elements. This recovery can be made by physical and chemical processes being size reduction by shredding the first step. In this paper, the effect of particle size in physical and chemical processing of printed circuit boards is presented and discussed. Shredding using cutting-based equipment allowed the comminution of boards and the liberation of particles composed by different materials (mainly metals and resin). Particle sizes less than 1 mm seem to be appropriate to attain high liberation of materials, which is crucial for the physical separation using gravity or electrostatic processes. Concerning chemical treatment, hydrometallurgical processing involves a leaching operation which can be also influenced by particle size of shredded boards. Samples with different granulometries were leached with 1 M HNO3 solutions, being leaching yields evaluated. It was concluded that particle size can be an important factor for the solubilization of some metals, but the effect is not similar for all elements.