Magnetic separation of ash and slag residues for their multi-component utilization: An overview

Abstract Over the last decades, huge amounts of ash residues have been generated worldwide leading to increasing demand for viable recycling technologies. Magnetic separation is considered a promising option for sustainable management of these wastes. The present paper aims to review the recent advances in magnetic separation of ash residues to convert these waste materials into valuable commodities, minimizing negative environmental impact and in compliance with the circular economy requirements. Emphasis is placed on single magnetic separation techniques, multi-step separation procedures, and implementation of the magnetic separation in more complex separation schemes (in combination with particle-size fractionation, flotation, electrostatic separation, density (sink-float) separation, etc.) Novel and special approaches are mentioned as well (using organic solvents, selective magnetic coating, separation supported by thermal treatment or chlorination, methods for removal of non-magnetic components, magnetic separation applied on solubilized/precipitated compounds etc.). It discusses the latest literature results on the magnetospheres’ morphology, chemical and mineral composition, and elemental leachability. Particular attention is paid to the utilization perspectives of the magnetic fractions and the non-magnetic residues. Based on the existing research status, the paper also provides concluding remarks highlighting the most promising trends. Current limitations indicating suggestions for future research (including insights on how existing approaches could be further improved) are mentioned as well.