Project Title: Process mineralogical energy characterization of urban e-waste towards metal recycling
Supervisors: Prof. Jochen Petersen, Dr. Lawrence Bbosa, Dr. Thandazile Moyo
The electronic waste (e-waste) stream is the fastest growing waste stream worldwide, growing at an annual rate of 3 - 5%. This poses a significant challenge for most nations, especially developing countries such as South Africa. Printed Circuit Boards (PCBs) are a major constituent of e-waste, found in nearly all electronic and electric equipment (EEE). These tightly laminated boards are comprised of a matrix of approximately 40% metallic, 30% plastic and 30% glass materials. Developing countries lack the infrastructure, capital and waste volumes to make recycling operations viable resulting in the consideration of hydrometallurgical processes as a primary processing route. However, current research and proposed hydrometallurgical processes require substantial mechanical size reduction of the PCB prior to subsequent processing. This mechanical size reduction has high energy demands resulting in energy costs being a significant factor and a deterrent to the advancement of local PCB processing in developing countries. By quantifying this energy demand, advancement in the local e-waste processing can be achieved. As this is a preliminary study, only unpopulated PCBs will be used with the aim to quantify the energy required for various means of mechanical size reduction of PCBs. It further aims to evaluate the extent of the mechanical size reduction necessary to achieve efficient metals extractions in the subsequent stages and considers this in terms of an economic energy balance. PCBs will undergo three different types of strength tests, three-point-bending, impact and tensile tests. These tests will provide insights into the actual energy demand required to break the boards in three different size reduction environments, hammer mill, ball mill and shredder respectively. Simultaneously, energy demand of the different processes to various particle sizes will be monitored. This allows for comparison of energy required to achieve a certain particle size by comparing it to the metal
percentage recovered from each process through the same acid leaching process. Strength tests provided preliminary insights into the minimum amount of energy required to break the boards in various environments. Clear information on energy required by each mechanical size reduction stage by analysing the amount of metal recovered by each stage.