Abstract: Provided is a method of easily producing scorodite which is stable and has excellent filtering properties with excellent reproducibility and without using complex operations, when processing arsenic that is included in non-ferrous smelting intermediates, and particularly when processing copper arsenic compounds in the form of an intermetallic compound. Scorodite is produced by a leaching step of leaching arsenic from a non-ferrous melting intermediate containing a copper arsenic compound in the form of an intermetallic compound in the presence of a sulfidizing agent and an oxidizing agent, a solution adjusting step of oxidizing trivalent arsenic to pentavalent arsenic by adding the oxidizing agent to the leaching solution, and a crystallizing step of converting the arsenic in the adjusted solution to scorodite crystals.

Abstract: A method of producing an iron-arsenic compound by adding an oxidizing agent to an aqueous solution containing arsenic ions and bivalent iron ions and allowing an iron-arsenic compound precipitation reaction to proceed under stirring of the solution, wherein the precipitation reaction is terminated at a solution pH in the range of 0 to 1. When the arsenic concentration of the pre-reaction solution is 25 g/L or greater, the reaction can be terminated at a solution pH in the range of ?0.45 to 1.2. The pH of the pre-reaction solution is preferably greater than 0 and not greater than 2.0. A ferrous sulfate is can be used as the source of the bivalent iron ions. Even when some amount of impurity elements is present in the arsenic-containing solution, the method is nevertheless capable of forming a scorodite compound excellent in crystallinity in the form of a compact compound barely swollen by moisture and the like, i.e., a niron-arsenic compound excellent in filterability.

Abstract: There is provided an iron arsenate powder which is produced from an arsenic containing solution and wherein the concentration of arsenic eluted or released from the powder is very low. The iron arsenate powder is a powder of dihydrate of iron arsenate, which has a mean particle diameter of not smaller than 8 micrometers, preferably not smaller than 10 micrometers, and a BET specific surface area of not greater than 2 m2/g, preferably not greater than 0.5 m2/g, and wherein the percentage of particles having particle diameters of not greater than 5 micrometers of the powder is not greater than 10%, preferably not greater than 5%. The amount of each of calcium and magnesium contained as impurities in the iron arsenate powder is preferably not greater than 2% by weight.

Abstract: The present invention provides a recovery method in which the indium sponge that is deposited by substitution in the substitution deposition step in the recovery of indium from an indium-containing material is produced in the form of a powder rather than in a bulky form. This recovery method is a method in which an indium sponge is deposited by substitution by adding a substance containing chlorine, and further adding a reducing agent, to an indium-containing solution whose pH has been adjusted to a value in the range of 1 to 2.2.

Abstract: The present invention provides a recovery method in which the indium sponge that is deposited by substitution in the substitution deposition step in the recovery of indium from an indium-containing material is produced in the form of a powder rather than in a bulky form. This recovery method is a method in which an indium sponge is deposited by substitution by adding a substance containing chlorine, and further adding a reducing agent, to an indium-containing solution whose pH has been adjusted to a value in the range of 1 to 2.2.