Abstract
There is an increased need for rare earth elements (REEs) due to their importance in modern technologies such as in renewable energy, electronic gadgets and defence equipment. Specifically, the demand for some REEs including neodymium, dysprosium and terbium often exceeds their existing global supply. Consequently, researchers are seeking alternative sources of extraction of these elements from secondary sources. This review paper examines the existing studies in this area of research. The specific objectives of this article are to: (1) examine the current extraction methods for REEs from coal ash; (2) investigate the current trends of research in this knowledge area and technological innovations; (3) discuss challenges and future directions for sustainable recovery. A narrative review approach was adopted to discuss the trends of recent research in this field of study. Results reveal that coal ash contains significant REE concentrations, suggesting its potential as a secondary resource within a circular economy framework. The study underscores that integrating environmentally benign extraction methods and life-cycle assessments could reduce waste, support resource recovery, and promote industrial sustainability. The findings contribute to ongoing efforts to transform coal combustion residues from environmental liabilities into strategic assets for green and sustainable mineral supply chains.