Cleaner approach to the recycling of metals in waste printed circuit boards by magnetic and gravity separation

Abstract

A physical cleaning approach utilizing magnetic separation and gravity beneficiation was used to recover metals from waste printed circuit boards (WPCBs). In addition, particle shape and settling velocity were measured to identify the sorting process. Based on element content analysis, separation procedures were designed for 1–0.5 mm and −0.5 mm. For −0.5 mm particles, magnetic particles were first recovered using a magnetic separator, and separation tailings were re-separated by gravity concentrator. Meanwhile, the 1–0.5 mm was directly separated by gravity separator. For −0.5 mm, magnetic concentrate with yield of 2% and 88% iron grade (oxide) was obtained. The contents of Cu and Fe in the gravity concentrate are 11.09% and 39.62%, with the recovery of 82.33% and 74.15%, respectively. For 1–0.5 mm, Cu and Fe content in concentrate are 67.7% and 8.17%, corresponding to respective recovery of 79.22% and 90.44%. The sorting mechanism was revealed by the particle settling velocity observation. Results show that the settling velocity of metal particles is significantly greater than that of impurity particles for both 1–0.5 mm and −0.5 mm. Because the separation tailings of 1–0.5 mm and the separation concentrates of −0.5 mm have the same settling speed, it is necessary to separate 1–0.5 mm and −0.5 mm particles separately. The study illustrates that the pollution-free physical method is efficient for recycling and recovering metal from WPCBs.