REE + Y and Sc distribution across the Djebel Onk phosphate beneficiation circuit (Algeria) using k0-INAA and WDXRF

Sedimentary phosphorites are increasingly recognized as potential secondary sources of rare earth elements (REE), yet their distribution during industrial beneficiation remains poorly documented. This study investigates the concentrations and process-scale distribution of REE + Y and Sc across eight streams of the Djebel Onk phosphate beneficiation circuit (Kef Essnoun, Tebessa, Algeria) using k 0 -instrumental neutron activation analysis (k 0 -INAA) and wavelength-dispersive X-ray fluorescence spectrometry (WDXRF). Results show that total REE concentrations (ΣREE, including Y) range from 645 mg/kg in the wet-route coarse reject to 955 mg/kg in the dry-route commercial product (CPD). Relative to the run-of-mine feed (832 mg/kg), REE enrichment reaches 15 % in CPD and 6 % in the wet-route commercial product. PAAS-normalized REE patterns are broadly similar across all streams, indicating that beneficiation redistributes REE among process products and residues without substantially modifying their geochemical characteristics. A process-scale mass balance based on measured REE concentrations and plant production data indicates that 63.3 % of the feed REE inventory reports to commercial phosphate products, whereas 36.7 % is distributed among reject and residue streams. The turbo-ventilator ultrafines (TSV) contain the largest non-product REE inventory (17.2 % of feed REE), while the combined fine residue streams retain 24.9 % of the total REE entering the circuit. Scandium exhibits a contrasting distribution pattern, preferentially partitioning into fine residue streams rather than phosphate concentrates. These results provide the first process-scale assessment of the distribution of REE, Y, and Sc in the Djebel Onk beneficiation circuit and contribute to understanding the behavior of critical elements during industrial phosphate processing.