Recovery of copper nanoparticles from waste printed circuit board and its characterization

Abstract

Waste PCBs were collected and shredded by a shredder in the current work. Shredded PCBs were treated by NaOH solution to remove or loosen up the polymer coating painted on the PCB. As copper was the target element in this experiment two step leaching process was adopted. In the first step, low concentration HNO3 treatment was done to leach the solders and other metals except copper and second step leaching was done by H2O2 added HCl solution for copper leaching. Copper was reclaimed as nanoparticles by electrowinning process using this copper pregnant leach liquor as the electrolyte. Concentration of various elements in the leach liquors of two step leaching process was determined by Atomic absorption spectrometry (AAS). Different characterization techniques such as particle size analysis, SEM with EDX, XRD and Rietveld refinement were applied to characterize copper nanoparticles. Final Cu rich solution found the concentration of Cu 29,437.5 ppm with the presence of few other elements. Reclaimed copper particles were in the range of around 30 to 200 nm revealed by SEM images while having the average crystallite size of 76 nm determined by Rietveld refinement. Presence of metastable cuprous oxide phase was found from the XRD analysis and elemental Cu phase percentage was 65. Macro scale EDX analysis confirmed that vacuum drying of the Cu particles dropped the O contamination from 30% to 6%.