A novel approach to separation of waste printed circuit boards using dimethyl sulfoxide

Waste printed circuit boards are complex heterogeneous mixture consisting of organic material, metal and glass fiber, therefore, it is quite difficult for the recovery of valuable materials from waste printed circuit boards. In this study, waste printed circuit boards without electronic components (known as bare boards) are submerged into dimethyl sulfoxide solvent at 170 °C using refluxing process. Metallographic microscope shows that waste printed circuit boards produce the delamination after treated with dimethyl sulfoxide solvent for 15 min. When waste printed circuit boards are treated with dimethyl sulfoxide solvent for 30 min, the separation of waste printed circuit boards is complete to obtain metals and glass fibers. Moreover, the used dimethyl sulfoxide solvent is vaporized by the rotary decompression which obtains regenerative dimethyl sulfoxide and solid residues. Comparing two Fourier transform infrared spectroscopies, it is found that the regenerative dimethyl sulfoxide is the same as original dimethyl sulfoxide. Thermal analyses combined with Fourier transform infrared spectroscopy show that the solid residues are bromine epoxy resins. These findings suggest that this innovative technology offers an environmental friendly process with no pollution and high efficiency for separating valuable materials from waste printed circuit boards.