Study of Metal Leaching from Printed Circuit Boards by Improved Electrochemical Hydrochlorination Technique Using Alternating Current

Abstract

This paper presents the results of the leaching of metals from computer PCBs by electrochemical hydrochlorination using alternating current (AC) with an industrial frequency (50 Hz). Leaching was carried out with a disintegrator-crushed computer motherboard with a particle size (d) of <90 μm. In the course of the research, the leaching efficiency of metals including Fe, Sn, Mn, Al, Cu, Zn, Pb, Ni, Ti, Sb, Cr, Co and V was evaluated depending on process parameters, such as AC density, experiment duration, hydrochloric acid concentration in the electrolyte solution, solid/liquid ratio, electrolyte temperature, and the loading option of raw material (loading option 1 involving loading into the electrolyte solution, and loading option 2 involving loading into the filter containers attached to electrodes). The research results showed that AC superimposition significantly intensifies the leaching of metals. It was established that the complete leaching of metals including Al, Mn, Sn, Ti and Zn, under experimental conditions (loading option 2, CHCl = 6 mol·L−1, i = 0.80 A·cm−2, S/L = 8.6 g·L−1), is reached after 1.5 h, and that of Cu and Ni is reached after 2 h from the beginning of the experiment. At the same time, the degree of leaching of other metals after 2 h is Co-78.8%, Cr-84.4%, Sb-91.7%, Fe-98.9%, V-98.1% and Pb-5.1%. The paper also reports the results on the leaching of all abovementioned metals, as well as Ag and Pd, with disintegrator-crushed mixed computer PCBs with d < 90 μm and loading option 1.