Environment-friendly recycling of resin in waste printed circuit boards

Abstract

Waste printed circuit boards (WPCBs) are considered as an attractive secondary resource and potential environmental pollutant due to the coexistence of valuable components and hazardous substances. The pre-concentration and utilization of resins in non-metallic components are concerned in this study. Mechanical grinding and physical separation were used for the dissociation and recovery of resin. Grinding results show that the R-R model can accurately describe the size composition of grinding products. The dissociation degree of resins increases with the grinding fineness, and the release rate of organics reach 78.79 % with 5 min grinding. Utilizing the natural floatability of dissociated organics, resin can be recovered effectively, which is mainly due to the increase of yield rather than the increase of grade. The resin grade can be enhanced by the difference of its density with that of glass fiber, and the resin content can reach 83.39 % with the sorting density of 1.6 g/cm3. Based on the pyrolysis characteristics of organics determined by TGA, the organics concentrate is utilized by pyrolysis in the form of pyrolysis oil with main components of phenols. This study provides a sustainable and environmentally friendly technology for the reuse of low-value but environmentally threatening non-metallic components in WPCBs.