Morphological evolution and recovery of high-purity ZnO from zinc roasting dust via pyrometallurgical reduction

• ZnO production from zing roasting dust, a major metallurgical byproduct. • An ecofriendly dry reduction–reoxidation process for ZnO recovery. • Distinct reduction temperature-dependent morphological changes in ZnO. • Approximately 99.5 % ZnO recovery under optimized reaction conditions. • Sustainable resource utilization in metallurgical industries. Zinc oxide (ZnO) is a versatile functional material with widespread applications in ceramics, coatings, catalysts, and optoelectronics, where high-purity ZnO is required. In this study, zinc roaster fume dust, a major metallurgical byproduct, was utilized as an alternative feedstock to produce ZnO through a dry reduction–reoxidation process. The reduction conditions, such as the reduction temperature (1100–1400 °C), reductant content (10–20 wt% coke with respect to the feedstock), and reaction time (30–90 min), were systematically explored to maximize ZnO recovery. The best-performing condition was 1150 °C for 60 min with 15 wt% coke, yielding ZnO of ∼99.5 wt% purity, as verified by inductively coupled plasma optical emission spectrometry and X-ray diffraction. Morphological characterization of the recovered ZnO powder revealed a distinct temperature-dependent phase transition; at ≤1150 °C, hexagonal prismatic crystals dominated due to anisotropic growth along [0001], whereas at higher temperatures spherical particles prevailed, consistent with supersaturation-driven nucleation of Zn vapor followed by rapid reoxidation. The particle-size distribution narrowed with increasing temperature, while agglomeration above ∼1300 °C broadened the mean size, indicating an upper thermal limit for uniform powders. these results demonstrate that dry reduction–reoxidation offers an effective and environmentally benign pathway to recover industrial-grade, high-purity ZnO from zinc fume dust while enabling morphology control via thermally tunable nucleation–growth regimes.