Removing inorganics from nonmetal fraction of waste printed circuit boards by triboelectric separation

Metals recycling from WPCBs has been studied for a long time, which results in the appearance of many proven techniques. However, the nonmetal fraction in WPCBs has not been fully recycled due to hybrid properties of inorganic and organic composition. In order to improve the usability of the nonmetal fraction from WPCBs, nonmetal materials separation by using a laboratory triboelectric separation system was carried out to improve the reuse efficiency of WPCBs nonmetal fraction. The optimum tribocharger material was investigated by using the charge-mass ratio measurement system, and PMMA is the optimum tribocharger material compared with PVC, PPFT, PPR, SS. The effects of airflow, voltage and feed rate on triboelectric separation were investigated. The product LOI of positive plate is up to 77.26% with recovery rate of 25.49%, while the product LOI of negative plate is down to 47.35% with recovery rate of 35.37%, and the remove rate of inorganics is up to 43.02% by triboelectric separation. The analysis results of X-ray diffraction indicate that the main inorganic materials mixed in nonmetal fraction are SiO2, Al2O3, CaO, Cu, Fe, Sn. The X-ray fluorescence analysis shows that the triboelectric separation can effectively remove the content of SiO2 and Al2O3. The scanning electron microscope images show that inorganics tribocharge positively and distribute in product collection grooves that close to negative plate. (C) 2015 Elsevier Ltd. All rights reserved.