Valorization of titanium production waste for selective Fe–Ti separation and concentrate production from titanomagnetite: response-surface optimization of chloride-assisted reduction roasting

Abstract

Titanium production wastes represent an underutilized secondary resource with potential value as functional additives in metallurgical processing. This study investigates the chloride-assisted reduction roasting of high-titanium titanomagnetite concentrate using semi-coke, spent titanium chlorinator melt (SMTC), a chloride-rich titanium production waste, and CaF2 to achieve selective Fe–Ti separation. A four-factor Box–Behnken response-surface design was applied to quantify the effects of roasting temperature and semi-coke, SMTC, and CaF₂ dosages on Fe grade, Fe recovery, TiO₂ grade, TiO₂ recovery, and iron metallization. RSM identified roasting temperature as the dominant process variable and delineated a broad high-performance region. The practically optimal conditions were 1200 °C, 20 wt.% semi-coke, 30 wt.% SMTC, and 4 wt.% CaF₂, yielding a magnetic fraction containing 91.24 wt.% Fe at 91.94% recovery and a non-magnetic fraction containing 62.78 wt.% TiO₂ at 96.04% recovery. Compared with NaCl, SMTC provided a substantially better balance between iron metallization and titanium partitioning. XRD and EPMA revealed extensive formation and coalescence of metallic α-Fe together with enrichment of rutile and magnesium titanate in the non-magnetic product. These findings demonstrate that chloride-rich titanium production waste can serve as an effective process additive for selective Fe–Ti separation, providing a dual pathway for titanomagnetite beneficiation and metallurgical waste valorization.