Patent ID: 8092764

Claim:
An arsenic processing method, comprising: a first step of leaching arsenic from a non-ferrous smelting intermediate containing arsenic, while maintaining a pH in a range of 4.0 to 6.5, forming a slurry from the non-ferrous smelting intermediate, and performing leaching while maintaining the pH in the range of 4.0 to 6.5 by adding sodium hydroxide at a temperature of 50° C. or higher, while blowing air, oxygen, or a gas mixture of air and oxygen, a second step of leaching arsenic while allowing the pH to change, without maintaining the pH, stopping the maintenance of the pH at a point when the arsenic contained in the non-ferrous smelting intermediate is leached in a range of 50% to 90%, continuing leaching while keeping the blowing of air, oxygen, or a gas mixture of air and oxygen, and completing a reaction at a point when the pH decreases to 4 or less; a third step of oxidizing trivalent arsenic in a leaching solution obtained in the second step to pentavalent arsenic, by adding an oxidation agent to the leaching solution; and a fourth step of converting the pentavalent arsenic in an adjusted solution obtained in the third step to scorodite crystals.