Hematite manufacturing process and hematite manufactured by same

A process for producing hematite in which a slurry is prepared by adding sulfuric acid to a nickel oxide ore, and leaching nickel and cobalt in a sulfuric acid solution at a high temperature and high pressure, a first neutralizing agent is added to the slurry to adjust pH, and the slurry is separated into a leachate containing nickel and cobalt and leached residue as hematite, and recovered, the process comprising using, as the first neutralizing agent, magnesium oxide produced by passing through the following steps (1) to (5):

• (1) sulfurization step of adding a second neutralizing agent to the leachate to separate impurities, and adding a sulfurizing agent to the resulting neutralized solution to obtain sulfides of nickel and cobalt, followed by separating a sulfurized solution;
• (2) calcium separating step of concentrating discharge waste water, which is obtained by adding a third neutralizing agent to the sulfurized solution to separate aluminum and manganese from the sulfurized solution, to precipitate and separate calcium contained in the discharge waste water as calcium sulfate;
• (3) magnesium crystallizing step of further concentrating a solution, which is obtained by passing through the calcium separating step, to precipitate and separate magnesium contained in the solution as magnesium sulfate;
• (4) roasting step of roasting the magnesium sulfate, which is separated in the magnesium crystallizing step, together with a reducing agent to obtain magnesium oxide and a sulfurous acid gas;
• and
• (5) washing step of washing the magnesium oxide obtained in the roasting step.