Nickel Recovery from Printed Circuit Board and Distribution of Other Elements by Heat Treatment and Magnetic Separation

Abstract

In an attempt to recover nickel and remove unnecessary elements during the copper smelting, crushed waste Printed Circuit Board (PCB) was treated by means of heat treatment and magnetic separation. Many multi-layered ceramic capacitors (MLCCs) including nickel have been mounted on PCB. Some MLCCs would be concentrated among the relatively small particles of crushed PCB, whereas others wouldn't be stripped from main board because MLCC has been downsized. In the first experiment, PCB without mounted parts excluding MLCC was treated in a nitrogen atmosphere at temperature, ranging from 773 to 973K, while the residue was magnetically separated. Nickel was concentrated in magnetics, whereas copper was mainly collected in non-magnetics. Nickel grade in magnetics was higher at relative high temperature. When the magnetic separation (magnetic field strength of 0.1T) was carried out after the sample was heated at 873K and screened with a 4mm screen, the nickel grade was enhanced from 0.16% to 6.7%, recovering 74% of feed. Copper loss, on the other hand, in magnetics was less than 1%. 82% of lead and 92% of tin were separated from non-magnetics of over 4mm in size. In the second experiment, crushed PCB with the size under 4mm was magnetically separated. Most nickel was collected into magnetics, which contains also a small amount of gold. In addition, some lead parts made of copper, nickel, tin and zinc plated with gold were also collected as magnetics. Heat treatment and magnetic separation were conducted for magnetics to separate gold from magnetics after separating lead parts. The magnetic fraction of 2 to 4mm in size, which was collected by magnetic separation (magnetic field strength of 0.1T) , after the sample was heated in the air atmosphere at 873K, had a nickel grade of 6.9%, whereas the gold loss was less than 1%. 82% of iron and nickel was separated as magnetics.