Evaluation of US EPA Method 3052 Microwave Acid Digestion for Quantification of Majority Metals in Waste Printed Circuit Boards

Waste electrical and electronic equipments as urban mines in Burkina Faso: Characterization and release of metal particles

Like other developing countries, Burkina Faso is one of the preferential destinations for second-hand electrical and electronic equipments (EEE). At the end of their life, these EEEs are classified as waste electrical and electronic equipment (WEEE) including Printed Circuit Boards (PCB). A particle size reduction is realized for the release of metals by shredding and grinding to obtain particles smaller 1.5 mm. A granulometric sorting was realized and nine granulometric portions were obtained. Particles were characterized by optical microscopy and Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (EDS). The experiments confirmed that the fractions contained polymers, glass fibers and metals under the form of single metals or alloys. The release of metal was efficient for particles with a size smaller than 0.71 mm. Three digestion procedures were experimented on four components to assess the impact on metals leaching. Microwave-assisted digestion method was the best procedure, compared to the analysis methods ISO 11466: 1995, and method 3050B, adapted. The characterization by Inductively coupled plasma atomic emission spectroscopy (ICP-AES) of these PCBs exhibited important amounts of precious metals (Ag, Au, Pd) and other metals in greater quantities (Cu, Pb, Ni, Co, etc.), leading to their qualification as "Urban Mines" calling for their recovery. The characterization of metals in each granulometric portion is realized. Precious and others metals were distributed in all granulometric size portions. So granulometric size reduction was not efficient for metal separation and recovery from PCBs and alternative methods should be investigated for selective precious metal recovery.