Recovery of high-quality iron phosphate from acid-leaching tailings of laterite nickel ore

Laterite nickel ore is rich in nickel and iron resources, and the nickel element is extracted in the form of nickel salt. However, the acid-leaching tailings of laterite nickel ore (LTLNO), which contain valuable iron resources, have not been cost-effectively recovered. In this work, we designed a novel method to extract iron from LTLNO and recycle it into high-valuable iron phosphate products using only phosphoric acid and iron powder. We explored the effects of reaction parameters, such as phosphoric acid concentration, iron powder dosage, time, and temperature, on the leaching behavior of key elements. The results showed that the iron leaching rate was as high as 96.54 % when using 3.5 mol/L phosphoric acid with a liquid-to-solid ratio (L/S) of 5 mL/g and an iron powder dosage based on the Fe/Fen+ ratio of 0.5 after 3 h at 25 degrees C, and a final high-purity FePO4 (99.4 %) was obtained. Kinetic analysis revealed that the leaching reaction was controlled by the diffusion through the neogenetic layer, and the leaching reactions were thermodynamically favorable. This method allows for a simpler and more efficient recovery of iron and the products of higher-value iron phosphate products than other LTLNO recycling technologies. Additionally, it offers a total economic benefit of $134/t for LTLNO treatment, demonstrating great prospects for industrial application.