Particle Size, Morphology, Texture, and Liberation Characteristics of Rare Earth-Bearing Phases in Phosphogypsum: Consequences for Beneficiation and Process Design

Phosphogypsum (PG) contains rare earth elements (REEs), but bulk concentration does not establish whether physical beneficiation is feasible. This critical review examines how gypsum crystallization, particle-size distributions, crystal habit, aggregation, mineral inclusions, and phase liberation affect REE deportment and the selectivity of downstream processing. Evidence from phosphogypsum studies is distinguished from methodological analogs in mineral processing, and the limitations of laser diffraction, sieving, sedimentation, automated mineralogy, and image-based textural analyses are evaluated. The synthesis shows that the critical design variable is not progressively finer particle size but the mass-balanced distribution of REE-bearing associations across size classes and their actual separability. Controlled comminution and dispersion can improve accessibility of discrete inclusions, yet may generate fines and worsen classification, flotation, filtration, and overall recovery. A staged characterization framework is proposed that links representative sampling, complementary sizing, size-specific chemical assays, quantitative mineralogy, breakage response, and closed process balances to evidence-gated flowsheet selection. The review identifies phase-resolved and size-resolved recovery measurements as a central research requirement for reliable beneficiation and process scale-up.