Clean and efficient process for the recycling of all components from waste printed circuit boards: Pre-treatment, bio-metallurgy, and deep utilization

Abstract

With the advancement of socio-economic development and the growing emphasis on environmental consciousness, electronic waste (e-waste) with hazardous properties has emerged as a focal point in global waste management. Waste printed circuit boards (WPCBs), which contain abundant metal elements such as Au, Ag, Cu, Al, Fe, and rare earth metals, have garnered widespread attention regarding the recycling challenges. In the absence of policy guidance and feasible technological advancements, WPCBs are typically disposed of through landfilling or incineration. However, WPCBs not only encompass economically valuable metals that can be extracted and processed but also harbor significant amounts of heavy metals and harmful substances that pose severe threats to both human health and environment. Therefore, the clean recycling of WPCBs is pivotal for fostering sustainable development in our society. This paper provides a comprehensive overview of the treatment methods for WPCBs. Firstly, the resource and environmental threat posed by WPCBs is introduced to illustrate the urgency of WPCBs recovery. Subsequently, the approaches for pre-treatment and pre-concentration of WPCBs recovery are described, along with an elaboration on their potential for development. The pre-treatment methods primarily involve crushing and grinding, while pre-concentration mainly utilizes physical techniques such as gravity separation and flotation based on particle density and surface properties. Thirdly, the deep purification methods for WPCBs metals are discussed, including pyrometallurgy, chemical treatment, and biological metallurgy; particular emphasis is placed on the application of bioleaching technology with sustainable development potential. Furthermore, the reuse methods for metallic components (MCs) and non-metallic components (NMCs) obtained through WPCBs separation are summarized. Finally, a systematic process for the clean and efficient recovery of WPCBs is proposed that encompasses pre-treatment, pre-concentration, biological leaching, and all components utilization, aiming to achieve sustainable resource utilization.