• Achieved high leaching efficiencies of Ni (89.4%), Co (94.8%), and Fe (96.5%) from Ni–Co–Fe alloy powder under mild atmospheric conditions (3 M H2SO4, 85°C, 10 mL/g, 90 min).
• H2O2 addition significantly enhances metal dissolution by modulating the solution redox potential, which is critical for efficient leaching.
• Phosphate precipitation effectively removes Fe from leachate (96.1% removal) with minimal Ni loss (2.29%), enabling downstream recovery of Ni and Co.
• Provides a sustainable alternative to high-pressure acid leaching (HPAL) for processing limonitic laterite ores, reducing capital and environmental costs.