• Na2SO4 addition during reductive roasting significantly enhances Ni and Co recovery from limonitic laterite, achieving 94.03% Ni and 80.16% Co recoveries.
• The formation of dual liquid phases (FeS–FeO–Fe and NaAlSiO4–NaFeSiO4) promotes particle migration and aggregation, yielding high-grade alloy powder.
• Pilot-scale rotary kiln trials confirm the industrial scalability and feasibility of the Na2SO4-assisted process.
• The study provides a sustainable pathway for extracting critical metals from low-grade laterite ores, addressing the growing demand for battery materials.