Abstract

Phosphorus control in titanium feedstocks is a critical yet often underestimated requirement for producing pigment-grade TiO₂. Across primary ores, upgraded feedstocks, and industrial processing routes, residual phosphorus—commonly reported as P or P₂O₅—emerges as a key risk factor that governs calcination behavior, rutilization efficiency, and ultimately pigment commercial viability. This critical review examines the mineralogical occurrence and deportment of phosphorus in titanium ores and Ti-bearing feedstocks. It systematically evaluates physical beneficiation, hydrometallurgical, and pyrometallurgical dephosphorization strategies from processing and performance perspectives. Particular emphasis is placed on mineralogical constraints on phosphorus removal, including limitations on liberation, microscale textural associations, and phosphorus redistribution during upgrading. Beyond removal efficiency metrics, the review highlights that P₂O₅ directly suppresses the anatase-to-rutile transformation during calcination by segregating at grain boundaries and stabilizing anatase, yielding mixed-phase pigments that are non-commercial despite high TiO₂ grades. Comparative analysis shows that physical beneficiation alone rarely meets phosphorus thresholds compatible with reliable rutilization; hydrometallurgical routes offer higher selectivity but introduce trade-offs in titanium recovery and effluent management; and pyrometallurgical upgrading to Ti-rich slags enables indirect phosphorus control through elemental partitioning when slag chemistry is explicitly engineered. The review concludes that robust phosphorus control requires integrated, feedstock-specific dephosphorization strategies optimized against rutilization performance rather than bulk chemical specifications, reframing feedstock qualification as a pigment-oriented engineering challenge.