Environmental and Technological Assessment of Operations for Extraction and Concentration of Metals in Electronic Waste

Abstract

The exponential growth in the consumption of electronics, in combination with the reduction in their useful life, has led to a significant increase in the volume of electronic materials which are discarded. Printed Circuit Boards (PCBs) are modules composed of ceramic, polymer, and metallic materials of high economic value and with a great potential for damage to biotic and anthropic environments when inadequately discarded. The aims of this work were to study the main environmental impacts and the efficiency of mechanical operations in the electronic waste recycling process in optimizing the concentration of metallic copper. For this, the samples obtained were characterized according to their morphology and chemical composition, and subjected to physical and mechanical treatments: dismantling, grinding, separation by granulometry, density, and magnetic property. The environment impacts were estimated by the Life Cycle Assessment of the pre-treatment processes, associated with copper extraction operations in Waste Printed Circuit Boards (WPCBs). According to the results obtained, it is possible to infer that the NM + 1 mm Concentrated product presents in its metallic composition around 78% copper, which contributes to the efficiency of the hydrometallurgical extraction processes. It is noteworthy that the Concentrated class represents about 14% of copper (wt) taking into account the amount of 3.789 kg of PCB waste input material. The potential for reinsertion of the dust in the material recovery process is highlighted, given that the chemical composition of this particulate has a significant presence of metals. In general, it was found that due to the higher concentration (wt%) of the sample being allocated in the range of −0.15 mm + 0.05 mm, the elements Fe (18.30%), Si (10.73%), Ca (9.21%), and Cu (8.89%) stand out regarding the participation of the elemental composition of this fraction and also regarding the general composition of the sample. Furthermore, the generation of dust during the fragmentation process can be associated with occupational respiratory diseases when not managed. About the Life Cycle Assessment, in seven of the nine categories evaluated, crushing and screening activities accounted for more than 90% of the recorded impact values. In general, it is estimated that in the pre-treatment phase it generated 15.4 kg CO2 eq.