Green and efficient mineral phase transformation of saprolitic nickel laterite ore through fluidized pre-heating and hydrogen-based pre-reduction processes

• Optimal fluidized pre-heating and hydrogen pre-reduction parameters were established (700°C for 30 min pre-heating; 700°C for 30 min pre-reduction; 80% H2 concentration), achieving nickel metallization of 90.56% and iron metallization of 41.31%. • Hydrogen enables effective nickel reduction at relatively low temperatures, offering a green alternative to conventional carbon-based reductants. • Pre-heating treatment is beneficial as it opens the mineral structures of serpentine and limonite, enhancing the interaction between reducing gas and nickel during pre-reduction. • The study provides mechanistic insights into phase composition, magnetism, surface elemental valence states, and microstructure evolution during fluidized pre-heating and pre-reduction of saprolitic nickel laterite ore.