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A decanter centrifuge has been employed to successfully separated phosphoric acid and rare-earth-element (REE) -containing particles from phosphoric acid sludge with concentrations ranging from 1, 000 to 2, 200 ppm REEs. Operating efficiently with up to 35 wt. % solids, the centrifuge was demonstrated to achieve approximately 95% phosphoric acid recovery and 90% REEs recovery in a single pass, eliminating the need for additional processing steps. This breakthrough supports a proposed REEs oxide recovery process integrating phosphoric acid (PA), elemental phosphorus (P4), and REEs into two potential pathways: PA-REO and PA-P4-REO. These processes aim to reintroduce recovered phosphoric acid into the main product to significantly increase output and revenue. Post-separation, phosphorus-rich particles can be converted to P4, while REEs-containing solids undergo further treatment including acid leaching, extraction/stripping, precipitation, and calcination to produce a marketable rare-earth oxide (REO) material. Techno-economic analysis indicates promising profitability, with the PA-REO process showing a delta net present value (∆NPV) of 441. 8 million and an expected return within a year of construction, while the PA-P4-REO process yields a ∆NPV of 178. 7 million over a 12-year return period. Both pathways offer robust financial prospects and demonstrate the feasibility of commercial-scale REEs recovery from phosphoric acid sludge.
Jang et al. (Thu,) studied this question.