Recovery of Light Rare Earth Elements from Coal Ash via Tartaric Acid and Magnesium Sulfate Leaching

Ardak Karagulanova, Burcu Nilgün Çetiner, Kaster Kamunur, Lyazzat Mussapyrova, Aisulu Batkal, Zhannur K. Myltykbayeva, Rashid Nadirov

2025

Full text Open access: Gold Metadata (CSL-JSON)

DOI 10.3390/chemengineering9050101

Data confidence 70 medium

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Abstract

Coal ash is a promising secondary resource for rare earth element (REE) recovery, yet efficient processing under environmentally benign conditions remains challenging. This study demonstrates that tartaric acid, when combined with MgSO4 as a salt additive, enables effective extraction of light REEs (La, Ce, Nd). REE recoveries improved from ~40% without salt to nearly 65% under optimized conditions. Kinetic modeling indicated a surface-reaction–controlled mechanism with activation energies of 20–22 kJ/mol, consistent with SEM evidence of particle erosion and size reduction. These findings highlight the potential of organic-salt leaching systems as alternatives to mineral acid processes, offering both effective REE recovery and reduced environmental impact.