A New Technology for Recovery of Metals from Waste Printed Circuit Boards

Advanced Recovery Techniques for Waste Materials from IT and Telecommunication Equipment Printed Circuit Boards

Waste from information technology (IT) and telecommunication equipment (WITTE) constitutes a significant fraction of waste from electrical and electronic equipment (WEEE). The presence of rare metals and hazardous materials (e.g., heavy metals or flame retardants) makes the necessary recycling procedures difficult and expensive. Important efforts are being made for Waste Printed Circuit Board (WPCB) recycling because, even if they only amount to 5–10% of the WITTE weight, they constitute up to 80% of the recovered value. This paper summarizes the recycling techniques applicable to WPCBs. In the first part, dismantling and mechanical recycling techniques are presented. Within the frame of electro-mechanical separation technology, the chain process of shredding, washing, and sieving, followed by one or a combination of magnetic, eddy current, corona electrostatic, triboelectrostatic, or gravity separation techniques, is presented. The chemical and electrochemical processes are of utmost importance for the fine separation of metals coming from complex equipment such as WPCBs. Thermal recycling techniques such as pyrolysis and thermal treatment are presented as complementary solutions for achieving both an extra separation stage and thermal energy. As the recycling processes of WPCBs require adequate, efficient, and ecological recycling techniques, the aim of this survey is to identify and highlight the most important ones. Due to the high economic value of the resulting raw materials relative to the WPCBs’ weight and composition, their recycling represents both a necessary environmental protection action, as well as an economic opportunity.

The influence of waste printed circuit boards characteristics and nonmetal surface energy regulation on flotation

This paper studied the influence of waste printed circuit boards (PCBs) characteristics and nonmetal surface energy (SE) regulation on flotation. First, SEM-EDS was applied to study the appearance and surface element distribution of the glass fiber and copper. The results showed that the glass fiber was present in a bundle and the surface carbon content was 49.42%, which facilitated glass fiber floating. The copper appearance contained many nodules, with a carbon content of 32.54%, which hindered copper sorting. XPS analysis further discovered that copper was mainly present in the forms of CuO, Cu(Met), and Al₂Cu. A FT-IR analysis revealed that the organic matter in the PCBs was essentially the same as the epoxy resin. It was easy to achieve floating and some polar functional groups promoted the adsorption of the flotation reagents. Based on this, by calculating the nonmetal SE, it was found that the proportion of the non-polar component of the nonmetal SE was 94.60%. The EDLVO theory was applied to research interactions between nonmetal particles. Hydrophobic attraction was found to be the main factor causing nonmetal particles to agglomerate. Further, the tannin was used to improve the dispersion of nonmetal by adjusting the nonmetal SE. Furthermore, the hydroxyl and carbonyl groups in the tannin may form hydrogen bonds with the bromine, epoxy and hydroxyl groups in the nonmetal. Finally, flotation test results indicated that tannin added significantly enhanced PCBs flotation efficiency. When the amount of tannin added increased from 0 to 60 mg/L, the recovery of copper increased from 61.92% to 90.53%. Thus, this study provides an alternative approach to improve the flotation efficiency of waste PCBs.

Present status of recycling waste mobile phones in China: a review

A large number of waste mobile phones have already been generated and are being generated. Various countries around the world have all been positively exploring the way of recycling and reuse when facing such a large amount of waste mobile phones. In some countries, processing waste mobile phones has been forming a complete industrial chain, which can not only recycle waste mobile phones to reduce their negative influence on the environment but also turn waste into treasure to acquire economic benefits dramatically. However, the situation of recycling waste mobile phones in China is not going well. Waste mobile phones are not formally covered by existing regulations and policies for the waste electric and electronic equipment in China. In order to explore an appropriate system to recover waste mobile phones, the mobile phone production and the amount of waste mobile phones are introduced in this paper, and status of waste mobile phones recycling is described; then, the disposal technology of electronic waste that would be most likely to be used for processing of electronic waste in industrial applications in the near future is reviewed. Finally, rationalization proposals are put forward based on the current recovery status of waste mobile phones for the purpose of promoting the development of recycling waste mobile phones in developing countries with a special emphasis on China.