Method of making goethite powder

Claim 2

In the production of goethite, the improvement comprising a method of making acicular goethite powder comprising the steps of: 1. mixing in a relatively short time an aqueous solution of an alkali hydroxide selected from the group consisting of sodium hydroxide and potassium hydroxide with an aqueous solution of ferrous salt selected from the group consisting of ferrous chloride and ferrous sulfate under an inert atmosphere to form a suspension of ferrous hydroxide in a temperature range of 60° to 80° centrigrade, 2. continuously stirring said mixed ferrous hydroxide suspension for a period of 2 to 5 hours which time is substantially greater than said mixing time under an inert gaseous atmosphere until milk-white colored fine ferrous hydroxide suspension is formed, and during said period of stirring the temperature of the solution being in the temperature range of 60° to 80° centrigrade, 3. and then oxidizing said ferrous hydroxide suspension by an oxygen containing gas for a period of 4 to 6.5 hours until yellow colored goethite is formed, the temperature range being 50° to 80° centrigrade when the alkali hydroxide is potassium hydroxide and the ferrous salt is ferrous chloride and the temperature range being 40° to 60° centrigrade when sodium hydroxide is the alkali hydroxide and the ferrous salt is ferrous sulfate.

Claim 3

A method of making goethite powder according to claim 1, wherein a mol ratio of OH - ion to Fe ++ ion (OH - /Fe ++ ) is over 3.

Claim 4

A method of making goethite powder according to claim 1, wherein a mole ratio of OH - ion to Fe ++ ion (OH - /Fe ++ ) is 3.8-5.8.

Claim 5

The method of claim 1, wherein said contacting is continued until substantially all of the ferrous ions in said suspension have been removed by oxidation.

Claim 6

The method of claim 1, wherein after said contacting is completed, the resulting mixture is filtered, and the so separated solids are dried and pulverized.

Claim 7

The method of claim 1, wherein the concentration of said ferrous salt in said starting solution thereof ranges from about 1.2 to 3.0 mol per liter of water.

Claim 8

The method of claim 1, wherein the concentration of said alkali hydroxide in said starting solution thereof ranges from about 6.0 to 12.0 mol per liter of water.

Claim 9

The method of claim 1, wherein said inert gaseous atmosphere comprises nitrogen.

Claim 10

The method of claim 1, wherein said oxygen containing gas comprises air.

Claim 11

In the production of goethite, the improvement comprising a method of making acicular goethite powder comprising a method of steps of mixing and simultaneously stirring for a relatively short time an aqueous solution of an alkali hydroxide selected from the group consisting of potassium hydroxide and sodium hydroxide with an aqueous solution of a ferrous salt, selected from the group consisting of ferrous chloride and ferrous sulfate in a temperature range of 60° to 80° centigrade and then continuing said stirring of the resulting mixture thereby to produce a colloidal aqueous suspension of ferrous hydroxide, said stirring being continued for a period of 2 to 5 hours until milk-white colored ferrous hydroxide suspension is formed, said mixing being accomplished in a time interval less than that used for said stirring, said mixing and said stirring being carried out in an inert gaseous atmosphere, during said stirring the temperature of said solution maintained in the temperature range of 60 to 80° C, and thereafter contacting the resulting suspension with an oxygen containing gas, thereby to oxidize said ferrous hydroxide for a period of 4 to 6.5 hours until yellow goethite is formed the temperature being 50° to 80° centigrade when potassium hydroxide and ferrous chloride is used and the temperature of 40° to 60° centrigrade when sodium hydroxide and ferrous sulfate is used.

Claim 12

In the production of goethite, the improvement comprising a method of making acicular goethite powder comprising a method of steps of mixing and simultaneously stirring for a relatively short time an aqueous solution of an alkali hydroxide selected from the group consisting of potassium hydroxide and sodium hydroxide with an aqueous solution of a ferrous salt, selected from the group consisting of ferrous chloride and ferrous sulfate in a temperature range of 60° to 80° centigrade and then continuing said stirring of the resulting mixture thereby to produce a colloidal aqueous suspension of ferrous hydroxide, said stirring being continued for a period of 2 to 5 hours until milk-white colored ferrous hydroxide suspension is formed, said mixing being accomplished in a time interval less than that used for said stirring, said mixing and said stirring being carried out in an inert gaseous atmosphere, during said stirring the temperature of said solution maintained in the temperature range of 60 to 80° C, and thereafter contacting the resulting suspension with an oxygen containing gas, thereby to oxidize said ferrous hydroxide for a period of 4 to 6.5 hours until yellow goethite is formed the temperature being 50° to 80° centigrade when potassium hydroxide and ferrous chloride is used and the temperature of 40° to 60° centrigrade when sodium hydroxide and ferrous sulfate is used.

Claim 13

A method of making goethite powder according to claim 10, wherein a mol ratio of OH - ion to Fe ++ ion (OH - /Fe ++ ) is 3.2-4.5.

Claim 14

A method of making goethite powder according to claim 10, wherein said fine ferrous hydroxide suspension is oxidized at the temperature of 50°-80° C.