KR890002091B1 - Method for removing iron from aluminate solution - Google Patents

Abstract

Iron and transition metals (e.g. Cr) are removed from aluminate soln. (i.e. Al-sulfate, chloride and nitrate) by use of chelate precipitant i.e. alkyldithiocarbamate salt of formula RR1NCS2M or alkylenebisdithiocarbamate salt of formula MS2CNH(CH2)nNHCS2M. Where R and R1=H, Me, Et, or (iso) propyl, same or not, M=Na, K or NH4+, n=2-4 integer.

Description

How to remove iron from aluminum acid salt solution

The present invention removes iron from aluminum sulfates obtained by acid treatment of clay minerals containing aluminum such as vortisite, kaolin, aluminite, montmorillonite, alumina shale, and aluminum acid salts such as aluminum chloride or aluminum nitrate. A new and advanced process for producing pure aluminum acid salts.

In general, a method of inferring an aluminum component from natural aluminum light is largely classified into two processes. In other words, there are alkali extraction methods that extract with alkali such as caustic soda or soda ash, and acid extraction methods that extract with acids such as sulfuric acid and hydrochloric acid. Especially, so-called Bayer method which extracts bokisite by pressurizing and warming with alkaline solution is industrial. It is the most widely used. On the other hand, the main reason why acid extraction method of aluminum ore is not common is that it is not easy to remove these impurities because iron and other heavy metals such as manganese and chromium are co-leached together with aluminum component during acid treatment. to be.

The composition of representative Bokisite among aluminum-containing clay minerals varies depending on the place of origin, but alumina (Al ₂ O ₃ ) is 52-57%, iron oxide (Fe ₂ O ₃ ) is 1-10%, silica (SiO ₂ ) 5-20%, and other small amounts of alkali and alkaline earth metals such as sodium and calcium, and trace metals such as titanium, zinc, copper, and nickel. On the other hand, the representative kaolin composition contains 35-39% of alumina, 40-50% of silica, 2-3% of iron oxide, and contains a small amount of heavy metals such as titanium, chromium and manganese together with a small amount of sodium, potassium and calcium. have. Extracting these aluminum clay minerals with acid co-leachs out the impurities in the minerals in a large amount compared to the extraction with alkylli, and in particular, the iron content (0.1-0.5%) in the aluminum extract is increased, so that the product itself can be colored and used for Most pure aluminum acid salts have been relied on by the alkali method because the use of the product is extremely limited due to iron restrictions. Therefore, researches for removing iron in the acid extract of aluminum have been conducted for several decades, but it has not been industrially applied yet.

The attempted methods for removing iron from the acid extract of aluminum are divided into three methods, precipitation method, solvent extraction method, and solvent precipitation method. None of these methods has been put to practical use. The reason for this is that the technical bodies have problems in industrialization or are disadvantageous in terms of economic efficiency than the alkali extraction method. For example, in the case of aluminum sulfate, the solvent precipitation method (Belg. Pat. 423,079 (1937) adds ethanol to an aqueous solution of aluminum sulfate to crystallize and precipitate the aluminum sulfate salt and leave impurities as iron in the mother liquor. First of all, impurities such as iron are not removed to a satisfactory level, and it is difficult to practically use them due to the difficulty in recovering expensive ethanol, which is a solvent, and in the solvent extraction method (US Pat. 3,479,136 (1969); Brit. 1,037,869 (1966)). After oxidizing all of the + 2-valent iron to + 3-valent iron, the iron is extracted by solvent extraction with an amine extractant such as Amberlite LA-1, where phase separation, recovery of the extractant, and treatment of the spent iron-containing sulfuric acid are performed. In addition to the technical problems, it is also known to be difficult to use, such as the use of expensive oxidizing agents. According to the precipitation method, sodium ferrocyanate (Na ₄ [Fe (CN) ₆ ]) method (US Pat. 3,141,733 (1964)) and ferricyanic acid (K ₃ (Fe (CN) ₆ ) method (Fe) 837,280 (1937)), xanthate salt (RO.CS _2. M, M = Na, K) method (US Pat. 2,416,508 (1947)), etc. However, iron precipitation by these precipitants has been introduced. Particles are produced in a fine colloidal state, which is difficult to filter and the addition of coagulant is very difficult to industrially filter the technical problem. These precipitants are not only expensive but also all iron ions +3 as in the solvent extraction method. It must be oxidized to a state or reduced to +2 valence and then precipitated, so it is hard to realize economic feasibility.

The present inventors accidentally found a new and superior iron removal method while trying various methods to solve the technical and economic problems for iron removal. In other words, a dithiocarbamate-based ligand, which has never been attempted to remove iron, does not react at all with a main metal element such as aluminum in an aluminum acid salt solution (pH = 0.5-3.0) and transfers such as iron and chromium. It has been found to bind selectively and quantitatively with metal ions to form stable crystalline precipitates. In particular, the iron-dithiocarbamic acid salt precipitates were found to be very easy to filter, due to their large precipitated particles, unlike the known precipitates described above. Another surprising and important aspect of the present invention is the fact that the iron-dithiocarbamate salt precipitates thus produced can be recovered and reused at least 80% of the dithiocarbamate precipitant by relatively simple chemical treatment with alkali. Therefore, the present invention is an advantage and a feature that can solve the conventional technical and economic problems at the same time.

In more detail to help understand the present invention, Bokisite, Kaolin. In aqueous aluminum sulfate, aluminum chloride or aluminum nitrate solution obtained by acid treatment of aluminum-containing clay minerals such as aluminite, montmorillonite, alumina shale, etc., the content of co-leached iron is usually 0.1-0.3%. Alkyl dithiocarbamic acid salt represented by general formula (I) which is a chelating precipitant or alkylenebisdithiocarbamic acid salt represented by general formula (II) is used to remove iron contained in these aluminum acid salt aqueous solution. Iron content is removed by adding to aqueous solution.

In formula (I), R and R 'are aliphatic alkyls, respectively, hydrogen, methyl, ethyl, propyl, and isopropyl, and R and R' may be the same or different. And M is an alkali metal such as sodium or potassium or an ammonium group.

_{M · S 2 C-NH- (} CH 2) n -NH-CS 2 · M (II)

In formula (II), M is sodium, potassium, or an alkali metal or ammonium group, like M in formula (I), and n is an integer of 2-4.

As a method for removing iron, an alkyldithiocarbamic acid salt of formula (I) or an alkylene bis dithiocar of formula (II) corresponding to 1.0 to 2.0 times the equivalent of iron equivalent in the aluminum acid salt Adding the chest acid salt to an aqueous solution of aluminum acid salt and stirring produces a dark brown to black iron precipitate. At this time, the iron precipitate is non-colloidal and can be easily filtered because the particles are large. Filtration of the iron-dithiocarbamic acid salt precipitate thus produced yields a solution of purified aluminum acid salt having an iron content of 1-100 ppm, depending on the amount of precipitant used. After washing the filtered precipitate 2-3 times with water, a dilute alkaline solution corresponding to 1.0-2.0 times the equivalent of the dithiocarbamate precipitate of general formula (I) or general formula (II), such as 1-5% When added to an aqueous sodium hydroxide solution, potassium hydroxide solution, or ammonium hydroxide solution and stirred, the dithiocarbamate precipitant is dissolved and regenerated with an alkali salt, and all iron components are precipitated with insoluble iron oxide (Fe ₂ O ₃ · xH ₂ O). At this time, the recovery rate of the dithiocarbamate precipitate of general formula (I) or general formula (II) reaches 80% or more with respect to the amount used for the first iron precipitation reaction depending on the reaction conditions. The recovered dithiocarbamic acid precipitant of formula (I) or formula (II) may continue to be used for the next iron removal. Therefore, the present invention enables practical application not only in terms of technology but also economically, and the superiority and advantages of the present invention will be described in detail as follows.

First, the dithiocarbamate salt precipitation method of the present invention is larger in size and non-colloidal in iron precipitate than any precipitation method conventionally attempted with respect to an aluminum acid salt solution (pH = 0.5-3), and thus has excellent filterability as well as iron powder. Excellent removal rate

Second, in most conventional precipitation methods, all iron components coexisting in the Fe ²⁺ and Fe ³⁺ ions in the aluminum solution are reduced to Fe ²⁺ ions in order to remove iron or in most cases Fe ³⁺ ions. Iron should be precipitated after an isothermal treatment process with oxidation. However, the dithio carbamate salt precipitate of the present invention does not require a pretreatment process and does not require expensive oxidizing agents or reducing agents by making iron precipitates stably in acid with either Fe ²⁺ ions or Fe ³⁺ ions.

Third, during acid treatment of aluminum ore, heavy metal ions such as forgetfulness, chromium, and zinc are co-leached in addition to iron. However, the removal of these heavy metals is not good. However, since the dithio carbamic acid salt precipitant of the present invention is very excellent in removing these heavy metal ions together with iron ions, it is a fact that a highly purified purified aluminum acid salt solution can be obtained.

Finally, in addition to the breakthrough superiority described above, another breakthrough invention that makes the present invention practical is that most of the dithiocarbamate precipitants are retreated by treating the iron-dithiocarbamate salt precipitate with a simple alkali. The fact is that it can be recovered and reused.

The dithiocarbamate salt precipitation method of the present invention described above is not necessarily limited to the aluminum acid salt solution obtained by acid treatment of aluminum ore, and thus can be effectively utilized to remove heavy metal ions such as iron in any similar aluminum acid salt. It is not limited to the embodiments described above and illustrated next.

Example 1

30% of sodium dimethyldithiocarbamate ((CH ₃ ) ₂ was added to the mixture of 100% Al ₂ (SO ₄ ) ₃ concentration and 2050 ppm Fe (3.67m mole) solution of aluminum sulfate 6.0 g (12.6 m mole) of NCS ₂ .Na) aqueous solution was added slowly, followed by stirring for 5 minutes. The produced black iron precipitate was separated by filtration to obtain a pure purified aluminum sulfate solution having an iron content of 39 ppm. The iron precipitate was washed three times with water and then poured into 30 g (15.0 m mole) of 2% aqueous sodium hydroxide solution and then stirred slowly. The black iron precipitate was decomposed to a brown iron oxide precipitate. The iron oxide precipitate thus obtained was filtered and the filtrate was analyzed by standard methods (Official Methods of Analysis of the Association of Official Analytical Chemists, 12th Ed. (1975) 6.310-6.313) and found 1.6 g of sodium dimethyldithiocarbamate (about 90 %) Was recovered. The same result of iron removal experiment was performed using the same sodium sulfate or potassium salt of various alkyldithiocarbamic acid instead of sodium dimethyldithiocarbamate with respect to the same aluminum sulfate solution as described above.

Example 2

30% of sodium dimethyldithiocarbamate ((CH ₃ ) ₂ was added to the solution of kaolin, which was then stirred with 100 g of an aqueous solution of aluminum sulfate having a concentration of 20% Al ₂ (SO ₄ ) _{3 and} 2050 ppm (3.67 m mole) of Fe. 6.2 g (13.5 m mole) of NCS ₂ .NH ₄ ) aqueous solution was slowly added in a nitrogen atmosphere, followed by further stirring for 5 minutes. At this time, the fish precipitate was separated by filtration to obtain a purified aluminum sulfate solution of 5ppm iron content. The iron precipitate was washed three times with water and then placed in 28 g of a 2% ammonium hydroxide solution and then stirred slowly at 35 ° C., and the black iron precipitate was decomposed to red brown iron oxide precipitate. The iron oxide precipitate thus formed was filtered and the filtrate was analyzed by the standard method of Example 1, and 1.7 g (91%) of ammonium dimethyldithiocarbamate was recovered.

Example 3

Kaolin was treated with hydrochloric acid, and the resulting solution was subjected to 20% dimethyl alumina solution with 22% AlCl ₃ concentration, Fe content 1680ppm (3.0m mole), Mn content 42ppm, Cu content 33ppm, Zn content 45ppm, Cr content 35ppm 8.5 g (11.9 m mole) of sodium dithiocarbamate was slowly added in a nitrogen atmosphere, followed by stirring for 5 minutes. The precipitate thus produced was filtered and separated to obtain a pure aluminum chloride solution containing 41 ppm of Fe, 18 ppm of Mn, 5 ppm of Cu, 7 ppm of Zn, and 3 ppm of Cr. The iron precipitate was washed three times with water, added to 30 g of 2% sodium hydroxide, and then stirred slowly at room temperature. The black precipitate turned into a reddish brown iron oxide precipitate. The iron oxide precipitate thus formed was filtered and the filtrate was analyzed by the standard method of Example 1, whereupon 1.5 (88%) of sodium dimethyldithiocarbamate was recovered.

Example 4

AlCl ₃₎ is obtained by processing the kaolin with nitric acid concentration of ₃ 35%, Fe content of 1510ppm (2.70m mole) of aluminum nitrate solution with stirring 100g hard here 30% dimethyl dithiocarbamic acid in an aqueous solution of sodium 5.0g (10.5m mole) Was added in a nitrogen atmosphere and then stirred for another 5 minutes. The produced black precipitate was filtered to obtain a pure aluminum nitrate solution having an iron content of 23 ppm. The iron precipitate was washed three times with water, added to 25 g of 2% sodium hydroxide, and then stirred slowly at room temperature. The black precipitate turned into a brown iron oxide precipitate. The iron oxide precipitate thus formed was filtered off and the filtrate was analyzed by the standard method of Example 1, whereby 1.3 g (87%) of sodium dimethyldithiocarborate was recovered.

Example 5

1 g of barium sulfate was added to 100 g of aluminum sulfate solution having a concentration of 21% and 2085 ppm (3.73 m mole) iron obtained by sulfuric acid treatment, and reacted at 105 ° C. for 1 hour to reduce all Fe ³⁺ ions to Fe ²⁺ . Cool to room temperature. The reduced aluminum sulfate solution was stirred in a nitrogen atmosphere, and 3.9 g (4.56 m mole) of 30% sodium ethylenebisthiocarbamate ((CH ₂ NHCS ₂ Na) ₂ ) aqueous solution was slowly added thereto, followed by further stirring for 5 minutes. The produced black iron precipitate was separated by filtration to obtain a purified aluminum sulfate solution having an iron content of 81 ppm. The filtered iron precipitate was washed three times with water and then placed in 20 ml of a 2% aqueous sodium hydroxide solution, and then stirred slowly at room temperature and under a nitrogen atmosphere. The iron precipitate was decomposed into a reddish brown iron oxide precipitate. The iron oxide precipitate thus formed was filtered off and the filtrate was analyzed by the standard method of Example 1, and 0.94 g (80%) of ethylene bis dithiocarbamate was recovered. Iron removal experiments were performed on the same aluminum sulfate solution using various alkylene bis dithiocarbamate salts instead of sodium ethylene bis dithiocarbamate in the same manner, and the following results were obtained.

Example 6

Aluminite was treated with sulfuric acid to stir 100 g of an aluminum sulfate solution containing 18% Al ₂ (SO ₄ ) ₃ concentration and 1800 ppm (3.22 m mole) of Fe, and 6.9 g (13.0 m mole) of 30% dimethyldithiocarbamate aqueous solution. ) Was added slowly and stirred for another 5 minutes. The produced black precipitate was separated by filtration to obtain a pure aluminum sulfate solution having an iron content of 2 ppm. The iron precipitate was washed three times with water, added to 45 g of 2% potassium hydroxide solution, and stirred slowly to turn the black precipitate into a reddish brown precipitate. The iron oxide precipitate thus formed was filtered and separated, and the filtrate was analyzed by the standard method of Example 1, whereby 1.8 g (87%) of dimethyldithiocarbamate was recovered.

Example 7

10 g of Al ₂ (SO ₄ ) ₃ concentration obtained by treating montmorillonite with sulfuric acid and 100 g of aluminum sulfate solution containing 1020 ppm (1.83 m mole) of Fe, while stirring vigorously, 5.0 g of 20% aqueous sodium dimethyldithiocarbamate solution (6.98m mole) was added slowly and stirred for another 5 minutes. The resulting black iron precipitate was filtered off to obtain a pure aluminum sulfate solution having an iron content of 12 ppm. The iron precipitate was washed three times with water and added to 20 g of 2% sodium hydroxide solution and stirred to turn the black precipitate into an iron oxide precipitate. The iron oxide precipitate was filtered off and the filtrate was analyzed by the standard method of Example 1 to recover 0.9 g (90%) of sodium dimethyldithiocarbamate.

Example 8

100 g of an industrial solid aluminum sulfate solution containing 15.6% of alumina (Al ₂ O ₃ ) and 120 ppm of iron was dissolved in 200 ml of water, and then stirred. Then, 1.2 g of a 10% aqueous dimethyldithiocarbamate solution was added thereto, followed by stirring for 5 minutes. . The produced black precipitate was separated by filtration and then heated to blow water to obtain pure aluminum sulfate having an iron content of 1 ppm or less.

Claims (3)

A method for removing iron and transition metals contained in an aqueous aluminum acid salt solution by adding an alkyldithiocarbamic acid salt of formula (I) or an alkylenebisthiocarbamic acid salt of formula (II) to an aqueous solution of aluminum acid salt.

In general formula (I), R and R 'are aliphatic alkyl and represent hydrogen, methyl, ethyl, propyl, and isopropyl groups, respectively, and R and R' may be the same or different. M is an alkali metal such as sodium or potassium or an ammonium group. In formula (II), M represents a sodium, potassium or ammonium group and n is an integer of 2-4. The aqueous solution of aluminum acid salt according to claim 1, wherein the aqueous solution of aluminum acid salt consists of an aqueous solution of aluminum sulfate, aluminum chloride, or aluminum ferric acid obtained by treating an aluminum-containing clay mineral such as bokisite, kaolin, aluminite, montmorillonite, alumina shale with an inorganic acid. Method for removing iron and transition metals. The process of claim 1, wherein in recovering the alkyldithio carbamate of formula (I) or the alkylenebisdithiocarbamate salt of formula (II), the precipitate is selected from sodium hydroxide, potassium hydroxide or ammonium hydroxide. A method for removing iron and transition metals, characterized by recovering an alkyldithiocarbamic acid salt of formula (I) or an alkylenebisdithiocarbamic acid salt of formula (II) by hydrolysis with an aqueous solution.