US2149370A - Treatment of titanium liquors - Google Patents

Description

Patented Mar. 7, 1939 TREATMENT OF TITANIUM LIQUORS Carlton E. Smith, Linthicum Heights, Md., as-

. Signor, by mesne assignments,to E. I. du Pont de Nemours and Company, a corporation of Delaware No Drawing. Application January 9, 1936, Serial No. 58,257

6 Claims.

The present invention relates to the adjustment of trivalent and tetravalent titanium compounds contained in titanium salt solutions which are intended for hydrolysis. In producing titanium salt solutions from titaniferous iron ores it has been found advisable to have practically all the iron'present in the ferrous state so that during hydrolysis of the titanium salt no iron would be precip tated together with titanium oxide.

It has already been the practice to reduce a part of the titanium salt to the trivalent stage so that any oxidation would preferably first oxidize the titanium without changing the status of the iron compounds in the solution. While this trivale'nt titanium in the liquor does not hydrolyze and is therefore lost in'the mother liquors of the hydrolyzed titanium compounds, this loss would not be sufilcient to materially influence the yields, I have found that the losses are much greater than would correspond to the amount of trivalent titanium, but it was usually considered that these losses were due to other factors such, for instance, that below a certain concentration of the titanium in the liquor no further hydrolysis takes place. I havenow found that trivalent titanium in a solution of tetravalent titanium salt acts as a negative catalyst on the hydrolysis. In other words, that trivalent titanium prevents complete hydrolysisof the tetravalent titanium,

and ,I have furtherfound that by controlling the amount of trivalent titanium in the hydrolysis liquor down to a certain amount I obtained a substantially higher yield of hydrolyzed titanium oxide.

For instance, I have been able, by reducing the titanous concentration of a titanium sulfate concentration from about 2.8 g/ 1 Ti+++ to about 0.3

g:/'1 Ti+++, to increase the yield of precipitated titanium dioxide by 2.2%; whereas, if the additional precipitated titanium dioxide had been only that arising from the oxidized titanous sulfate, only 1.0% havebeen precipitated.

Based on the above discoveries my invention consists in oxidizing the trivalent titanium in a more titanium dioxide would resulting attack mass containing the mixed sulfates in water or dilute sulfuric acid. The rate of solution is greatly increased by reduction of the ferric sulfate to the ferrous condition; in fact in practical operation the dissolving step is usu ally accompanied. by this reduction. The reduction of the ferric sulfate is ordinarily accomplished by the addition of metallic iron in amount sufficient to convert all the ferric compounds to ferrous compounds.

Under practical operating conditions an excess of metallic iron must be used to complete this reduct-ion within a reasonable time and there results a considerable conversion of the titanic sulfate to the trivalent titanous form. As a result of such practical consideration, the treated solutions always contain an amount of trivalent titanium in excess of that which experience has taught would be required to adequately protect the ferrous compounds, from being re-oxidized.

Normally, from 52-53% of the titanium sulfate is thus reduced to the titanous condition. It has been the previous practice to clarify this solution containing titanic sulfate, titanous sulfate and ferrous sulfate, remove part of the ferrous sulfate by crystallization and then hydrolyze to precipitate hydrous titanic oxide. During the clarification of the solution and the subsequent treatment preparatory to hydrolysis the titanous content tends to decrease but remains at the level of (Mi-2.0% of the total titanium content of the solution. Consequently the hydrolysis is ordinarily conducted in the presence of (LE-2.0% of titanous compounds based upon the total titanium content of the solution.

According to my invention I oxidize this trivalent titanium in careful operations. I can stop the oxidation at the point desired. In some instances it might be convenient to over-oxidize to the point where some of the iron is also oxidized and then reduce back to the desired degree of reduction of the titanium. For this purpose I can use any desirable oxidizing agent. Ferric oxide has been found very convenient and hydrogen peroxide,as well as bichromates, permanganates, chlorates, nitric acid, persulfates, red lead, manganese dioxide, ozone, electrolytic oxidation, etc. Such oxidizing agent is simply added in a calculated amount of the titanium sulfate solution. Among the various oxidizing agents it will be understood that ferric salts and particularly ferric oxide, which is insoluble in the titanium liquor, is the most convenient as this oxidizing agent is incapable of oxidizing the ferrous iron present in the solution.

In the practice of my invention I have taken a titanium solution containing approximately 2% of its titanium content in the titanous condition and have added to this solution a sufficient amount of ferric oxide to decrease the titanous content from 2% down to .3% of the total titanium content. The ferric oxide used is a calcined product substantially insoluble in the titanium solution. I have found that the ferric oxide. obtained by roasting copperas makes an excellent oxidizing agent and I prefer to incompletely roast such copperas so that some more or less insoluble ferric sulfate is present. I have then filtered the treated titanium solution to remove traces of insoluble impurities and haveused the treated liquor in the hydrolysis step to produce a precipitated hydrous titanic oxide suitable for calcination to yield a white titanic oxide pigment.

Example I During a 24-hour period four large scale-hydrolyses were made using a titanium sulfate solution having an average concentration of 250 grams TiOz per liter, of which 2.6 grams per liter (1.04%) was in the trivalent state. Average yield on the four hydrolyses was 95.5%.

In similar manner with other conditions being identical four other large scale hydrolyses were made using titanium solution at 250 grams TiOz per liter, in which the excess amount of titanium in the trivalent state had been decreased by oxidation of the same with calcined copperas to 0.4 gram per liter (0.16%). Under the same conditions of hydrolysis the average yield of these four hydrolyses was 97.2%, or 1.9% improvement 7 over yield obtained above, where trivalent tita- Example II In this case two laboratory hydrolyses were ,made on the same titanium sulfate solution, one

solution containing 1.4 grams per liter (10.78%) of titanous sulfate, the other containing 0.05 gram per liter (0.034%) of titanous sulfate. In the latter case, the titanium in the titanous condition had been oxidized by the addition of a calculated amount of hydrogen peroxide.

Hydrolysis No. 1 i I No. 2

'IiO, before hydrolysis 179 g/l 177 g/l Ti+++ before hydrolysis 1.4 g/l 0.06 g/l Ti+++ after hydrolysis 1. 2 g/l 0.04 g/l 95. 3% 96.5% 95.6% 96.8% 8hr. boil. 95.3% 97. 3%

r Decrease in titanous content 1.34 g/ 1 7 Actual increase in yield 1.0-1.2 Theoretical increase in yield 0.75

of tetravalent titanium present by oxidizing excess trivalent titanium present in said solution to a concentration of substantially 0.2% to 0.5% of the total titanium present by adding to said solution a relatively small amount of a water-insoluble ferric compound from the group consisting of ferric oxide and calcined ferrous sulfate, and subjecting the resultant solution to hydrolysis.

2. The process of claim 1, in which the excess trivalent titanium is oxidized by the addition of roasted copperas to a titanium sulfate solution.

3. A process for hydrolyzing a titanium salt solution containing an excess quantity of trivalent titanium, to effect substantially complete hydrolysis of the tetravalent titanium present in said solution, comprising adding suflicient ferric oxide to said solution to decrease by oxidation its trivalent titanium content to a concentration ranging from substantially .2% to not to exceed substantially .5% of the total titanium present, and then hydrolyzing the resultant solution.

4. A process for hydrolyzing a titanium sulfate solution containing an excess amount of trivalent titanium, to effect substantially complete hydrolysis of the tetravalent titanium content thereof, comprising adding a suificient amount of calcined ferrous sulfate to said solution to decrease by oxidation the trivalent titanium content of said solution to a concentration ranging from substantially .2% to not to exceed substantially .5% of the total titanium present, and subjecting the resultant solution to hydrolysis.

5. A process for hydrolyzing a titanium salt solution containing excess quantities of trivalent titanium in order to effect substantially complete hydrolysis of its tetravalent titanium content, comprising adding to said solution-a mixture of water-insoluble ferric oxide and ferric sulfate in amount sufficient to decrease by oxidation the trivalent content of said solution to a concentration ranging from substantially .2% to not to exceed substantially .5% of the total titanium present, and then subjecting said solution to hydrolysis. I

6. A process for increasing the hydrolysis yields of TiOz from a titanium salt solution containing excess quantities of trivalent titanium, comprising adding ferric oxide to said solution in an amount sufiicient to decrease by oxidation its trivalent titanium content to substantially .3% of the total titanium present, and then hydrolyzing said solution.

CARLTON E. SMITH.