Separation and purification of metal and fiberglass extracted from waste printed circuit boards using milling and dissolution techniques

Abstract

Pulverization operations are extensively used in the recycling of waste printed circuit boards (WPCBs) for liberation of metal and fiberglass in powder shape. The types of liberated metals can vary greatly, for instance it can be copper, tin, lead, aluminum, nickel, gold, palladium, and so forth. However, the obtained metal and nonmetal particles remain contaminated by hazardous material—Brominated Epoxy Resin (BER) what can result in series of environmental and health issues during the further processing. The developed approach was focused on the extraction of uncontaminated copper and fiberglass (which are considered the basic elements that can make up >50% of total WPCB weight) in the form of micro‐particles. To achieve this goal, WPCB samples were cut from areas with high copper concentration while the other components like solder and through‐hole pads (containing other metals) were avoided. At the next step, high energy ball milling was used to grind WPCBs and obtain BER/metal and BER/fiberglass particles. After that, Dimethylformamide (DMF) and ultrasonication were used for dissolution of BER in the powder at a low temperature 50°C, whereas the total treatment time was 4 h and solid to liquid ratio was 1:6 (w/v). Finally, centrifugation was employed to separate the liquid phase (BER/DMF solution) from solid phase (metal and fiberglass particles). The experiments were conducted on five WPCB samples of the same weight that were cut from the five different WPCB models. After the experiments used DMF was regenerated by a rotary evaporator. Ultraviolet‐Visible Spectroscopy, metallographic microscope, Fourier transform infrared spectroscopy, and SEM‐EDS were used to examine the structure of recovered BER, fiberglass, regenerated DMF, and base metal compositions of each sample. The results showed that the metal composition of samples directly depended on WPCB model types. Also, the treatment significantly improved the purity of the extracted fiberglass, therefore it can be used as a high‐purity micro‐filler material for composite applications; the same purification was observed for recovered copper. © 2018 American Institute of Chemical Engineers Environ Prog, 37: 1901–1907, 2018