FI62519B - PROCEDURE FOR THE CONSTRUCTION OF FERRARIES AND TITLE MEASUREMENT - Google Patents

Description

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The present invention relates to a process according to the preamble of claim 1, which relates to a process for the removal of ferric iron from a titanium dioxide concentrate, in particular an ilmenite concentrate.

Pigment-grade titanium dioxide is produced industrially by either the chloride or sulfate process. The former is based on the chlorination of the high titanium dioxide starting material under reducing conditions and the combustion of the titanium tetrachloride obtained at high temperature and the oxygen stream to TiO 2 and chlorine, which is recycled. In the latter method, the sulfate method, a TiOg-containing mineral, usually an enrichment of ilmenite, is dissolved in sulfuric acid. From this, TiO 2 is doped after flocculation of hydrolytically insoluble material, partial crystallization of ferric sulfate from the reduction of trivalent iron, and some other process steps. Final pigment properties of saut-20 when calcined and ground titanium dioxide hydrate is obtained (Kirk-Otitoer: Encyclopaedia of Chemical Processes, Vol. 20, p. 1400 (1969)) ·

The reduction of ferric iron mentioned in the sulphate process and the crystallization of ferrous sulphate constitute the most problematic step in the process for the protection of the environment. It is important for the quality of the pigment that when the titanium oxide hydrate is precipitated, the trivalent iron of the solution is completely reduced. Otherwise, this trivalent iron is absorbed on the surface of the pigment and causes deterioration of whiteness.

Trivalent iron is most commonly reduced by scrap iron according to formula (1) (1) Fe + 2Fe3 + = 3Fe2 +

Normally, due to the acidic conditions, some hydrogen gas is also formed in the reaction, which naturally poses an explosion hazard.

The reduction of ferric iron can also be carried out electrolytically according to formula (2): • 5 + - p + (2) Fe + e Fe 5 In this case the iron content of the solution does not increase, but the electrode material used, usually lead, may partially dissolve and cause occupational hygiene and environmental hazards.

Crystallized FeSO 4 hydrate is largely a 10-ton waste. In addition, after hydrolytic precipitation, it remains in the acid leaving the process, the so-called waste acid, a lot of ferrous sulfate.

Said ferrous sulphate waste poses a serious environmental and waste problem. If the amount of trivalent iron 15 could be reduced in any other way than by reducing the iron already dissolved, these environmental and waste problems could be reduced. This reduction of ferric iron should obviously take place even before dissolution.

It is known that ferric iron can also be removed from solution by 20 liquid extractions. Accordingly, U.S. Patent No. 1+ 168 29T discloses the extraction of trivalent iron from solution with HDEHP. FI patent application 761256, on the other hand, discloses a corresponding extraction after precipitation of TiO 2 hydrate.

In a known method (Kirk-OQiner: Encyclopaedia of 25 Chemical Processes, Vol. 20, p. 1 * 00), e.g.

a mixture of ilmenite and hematite with 35% TiO 2 and 28% FeO and 26% FegO 2 in an electric furnace with anthracite to give a mixture of 72% TiO 2 and 9% FeO.

Such a reduction method is expensive in the current energy-30 situation.

It has now surprisingly been found that by treating a ferric iron-containing titanium dioxide concentrate, in particular ilmenite concentrate, with an aqueous solution of lignosulphonic acid obtained from wood sulphite digestion, trivalent iron 35 can be selectively dissolved in oil.

Such ferric lignosulfonate complexes can be prepared as is known, for example, by adding ferric sulfate, 3,251,9 nitrate, or chloride to a solution of potassium lignosulfonate (U.S. Patent 3,985,667 to International Telephone and Telegraph Corporation).

More specifically, the method according to the invention is mainly characterized by what is set out in the characterizing part of claim 1.

The lignosulfonic acid required to treat ilmenite can be prepared, for example, from calcium lignosulfonate by treating it with sulfuric acid to give a reaction of calcium lignosulfonate with sulfuric acid to give gypsum and lignosulfonic acid according to formula (3): (3) CaLSO 3 + HgSO 4 »Ca

However, the procedure is disadvantageous because the lignosulfonic acid thus prepared is easily polymerized and is then unusable for extracting ferric iron from ilmenite concentrate.

Lignosulfonic acid can also be prepared by cation exchange. Such a method is known e.g. U.S. Patent 3,957,703 (Georgia-Pacific Corporation).

Calcium can also be extracted from calcium lignosulfonate with di-2-ethylhexylphosphoric acid (N.E. Brezhneva et al., Proceedings International Solvent Extraction Conference 197, Vol. 2, pp. 1737-1760). The latter method, based on liquid extraction, has e.g. the advantage that the preparation of 25 lignosulfonic acid can be easily made continuous. On the other hand, calcium is only partially extracted in the process, and this prevents polymerization by heating the lignosulfonic acid.

The production of lignosulfo-30 nic acid by solid cation exchange also has the potential for a continuous process.

In the treatment of ilmenite, it does not matter whether or not lignosulphonic acid contains sugars. Instead, this fact is relevant to the use of the obtained ferric lignosulfonic acid-35 complex. If the product is used as a dispersant for cement, sugars have a retarding effect on cement hardening. In the oil drilling industry, sugar also has a detrimental effect - e.g. odor nuisances of mud>. 6251 9 are due to biological reactions of sugar waste.

Lignosulfonate can be prepared as sugar-free, for example, by using the sugars in the sulfite waste liquor as ethanol or by a pecyl process as a protein. However, some sugars still remain in the resulting lignosulfonate product. High purity sugar-free lignosulfonate is obtained when the sulfite waste liquor is treated by ultrafiltration or liquid extraction. The previous method is known e.g. From Per Clausen's (De Danske Sukker-10 factory) article "Membrane filtration <jf SSL ..." Pulp & Paper Canada 79 No. 3, T81-T85 March 1970 / Liquid extraction is known e.g. U.S. Patent 3,825,526 (Forss et al.) And FI Patent Application 791-95 (S-L Hämälä, S. Koivunen, A-K Kontturi and V. Sarkkinen).

The following examples further illustrate the method of this invention applied to the treatment of ilmenite. Example 1

20 Na-lignosulfonate obtained from the waste liquor of spruce sulphite soup and purified by the method according to Finnish patent application 791695 was treated with an acidic, strongly acidic cation exchanger as follows:

Na-lingosulfonate concentration 108 g / l, solution 1 liter Ion exchange resin 250 ml 25 Mixing time 1 h

The ion exchange resin was separated. The solution was boiled to reduce the concentration of SO 2. 100 ml of ion exchange resin was added again. Stirred for 30 min. The resin was separated.

In the lignosulfonic acid solution thus obtained, 180 g of ilmenite concentrate was now dispersed, the composition of which was as follows:

TiO2 UT, 2%

FeO U0.5% 35 Fe2 ° 3 * V205 0.3% 5 62519

The resulting dispersion was heated to 100 ° C with good stirring and maintained at this temperature for 1 h. The ilmenite concentrate was now filtered off, washed and analyzed. Its composition was as follows: 5 TiO 2 1 + 8.9%

FeO U2.0%

Fe 2 O 3 0.8% V 2 O 5 0.2% The treated ilmenite was reprocessed with pure lignosulfonic acid solution. After the resumption of treatment, the Coalition Party was as follows:

TiO 2 1 + 9.3%

FeO 1 + 2.3%

Fe 2 O 3 0.1% 15 v2o5 0.1%

Thus, about 98% of the lignosulfonate-complex had been removed from ferric iron and about 66% from vanadium. The removal of the latter may advantageously affect the whiteness of the pigment prepared from the ilmenite concentrate.

The filtrate from the first lignosulfonic acid treatment of the ilmentite concentrate was treated as follows: To a 100 ml solution was added 20 g of NH 4 SCN and the solution was extracted with 100 ml of amyl alcohol. The shaking time was 10 min. The organic and aqueous phases were separated. The organic 25 phase was intense red. The organic phase was treated with ammonia water to give the organic phase with rhodanide 3+. .

Fe contained in lexina precipitated. The precipitate weighed 0.57 g. It contained maghemite and hematite according to X-ray diffractometry, and the elements V, Mn and Ti were also found according to the study.

Example 2

The procedure was as in Example 2, but the lignosulfonic acid was prepared from ultrafiltered lignosulfonate with a purity of 95%.

TiO2 U9.0%

FeO 1 * 2.2%

Fe 2 O 3 0.1+% V 2 O 5 0.2% 5 Example 3

Calcium bisulphite soup waste broth with the following composition:

Lignosulfonates 95 g / l

Sugars 6 g / l 10 Ca 5, U g / l were treated as follows:

1 liter of waste broth was taken and extracted with stirring for 30 minutes with d-2-ethylhexylphosphoric acid diluted overnight with xylene. The phase ratio was 2 parts of 15 organic phases, 1 part of an aqueous phase.

After clarification, the solution had a calcium content of 1, 1 g / l and a pH of 1.2.

The aqueous phase was re-extracted in a phase ratio of 2: 1, and the Ca content was further reduced to 0.7 g / l. The pH was 1.0 after the second 20 extractions.

180 g of the ilmenite concentrate mentioned in Example 1 was now dispersed in the obtained lignosulfonic acid solution. The resulting dispersion was stirred at 100 ° C for 1 h and the ilmenite concentrate was filtered off. Its analysis was as follows: 25 TiOg 1 * 8.8%

FeO 1 + 1.9 l

Fe 2 O 3 1.0% V 2 O 5 0.2%

Example 1+ 30 The ilmenite concentrate obtained in Example 1 was dissolved in 93% sulfuric acid, which was used so that the HgSO 4: TiOg ratio of the solution was 1.95. The trivalent iron in the solution was reduced with 100 mg of iron chips when the amount of starting ilmenite concentrate was 180 g. The reduction was continued until the solution contained 3 g / l of trivalent titanium. Solution 7 62519 was filtered and concentrated to a specific gravity of 1.7. The solution was now heated to 90 ° C and 2% TiO 2 of titanium hydroxide cores were added to act as crystallization cores. Solution 5 was then heated to reflux and boiled for 1 h

TiOp hydrate precipitated. The precipitate was washed, treated with 0.5. .... ... 3 + g at Zn powder temperature to reduce any Fe remaining in the pigment, washed and 1% ZnO by weight of TiOgt was added as a rutilization catalyst. The product was calcined to the finished rutile-TiO 2 pigment for 1 h / 850 ° C. The rutile content was then 96.9 #.

The whiteness of the pigment was measured with an El Repho whiteness meter to give 99.28% of the whiteness of MgO.

1 5 Example 6

The procedure was as in Example 5, but using the untreated ilmenite concentrate mentioned in Example 1. The reduction consumed U, 5 g of iron chips, i.e. more than ^ times the amount. The pigment obtained had a rutile content of 20.6 delta and a whiteness of 98.1% of the whiteness of MgO.

An aqueous solution of lignosulfonic acid can generally be contacted with the concentrate to be treated, e.g., by spraying the solution onto the concentrate and allowing it to flow through the rich tea. The concentrate and the aqueous solution can also be mixed together. The mixing temperature may be 30 to 110 ° C, preferably 90 to 100 ° C. The weight ratio of lignosulfonic acid to concentrate may be 0.8 to 1.3, preferably about 1.0. The concentration of the aqueous lignosulfonic acid solution may be 5 to 25%, preferably 30 to about 10%.

Claims (9)

8 62519 A process for the removal of ferric iron by liquid treatment from a ferric iron-containing titanium dioxide concentrate, in particular ilmenite concentrate. characterized in that 5. the ferric iron-containing concentrate is contacted with an aqueous solution of lignosulfonic acid so that the weight ratio of lignosulfonic acid to concentrate is 0.5 to 5.0 and the concentration of the aqueous solution is 1 to 50%, and the ferric iron-free solid concentrate tO is separated from the dissolved ferric iron from an aqueous solution of lignosulfonic acid in a manner known per se, e.g. by filtration, clarification or centrifugation. Process according to Claim 1, characterized in that an aqueous solution of lignosulphonic acid is sprayed onto the ferric iron-containing concentrate and allowed to flow through the concentrate. Process according to Claim 1, characterized in that the ferric iron-containing concentrate and the ligno- The aqueous sulfonic acid solution is mixed together. Process according to Claim 1 or 3, characterized in that the concentrate and the aqueous solution are brought into contact with one another at a temperature of 30 to 110 ° C. Process according to Claim U, characterized in that the concentrate and the aqueous solution are brought into contact with one another at a temperature of 90 to 100 ° C. Process according to Claim 1, characterized in that the weight ratio of lignosulfonic acid to concentrate is 0.8 to 1.3, preferably about 1.0. Process according to Claim 1, characterized in that the concentration of the aqueous solution of lignosulfonic acid is 5 to 25%, preferably n, 10%. Process according to Claim 1, characterized in that the ligno-35 sulfonic acid used in the aqueous solution is substantially sugar-free. 6251 9