A new iron recovery and dephosphorization approach from unroasted high-phosphorus oolitic hematite ore via a facile chemical beneficiation process

Despite the abundance of scientific reports on the treatment of oolitic hematite, it still constitutes a global challenge. The distinctive oolitic structure within the ore is regarded as the primary factor causing the difficulty in the beneficiation of oolitic hematite ore. The objective of this study is to devise an effective approach to tackle the issue of beneficiation of oolitic hematite ore, thereby facilitating the utilization of oolitic hematite ore, which is widely abundant worldwide. Based on the Pourbaix diagram (E_h-pH) of the Al-Si-H₂O system, an alkaline leaching process for eliminating impurities from unroasted oolitic hematite using NaOH solution as the leaching agent was proposed. The optimal parameters were determined as a temperature of 250°C, a NaOH concentration of 16 mol/L, a liquid-to-solid ratio of 4 mL/g, and a reaction time of approximately 2 h. Around 54% of phosphorus (P), 21% of Al₂O₃, and 61% of SiO₂ can be preliminarily removed from unroasted oolitic hematite ore. Through further dephosphorization with dilute sulfuric acid at room temperature, a high-quality Fe concentrate with 63.3% Fe, 0.04% P, and a Fe recovery rate of 96% was obtained. The alkali can be readily regenerated by adding lime to the leaching solution, and the regenerated alkali has a leaching effect comparable to that of the fresh leaching solution. The recycling and utilization of alkaline leaching agents minimize production costs to the greatest extent possible. Mechanical studies have discovered that intact oolites undergo complete dissociation under alkaline leaching, enabling the leaching solution to permeate into the particles and thereby deeply eliminate impurities. The novel method has accomplished efficient processing of oolitic hematite and a reasonable control of production costs during processing, which is significant for expanding the reserves of iron ore resources.