JPH06157039A - Production of zirconium chloride aqueous solution - Google Patents

Abstract

PURPOSE:To effectively and efficiently produce the zirconium chloride aqueous solution having a high quality by obtaining a hydrochloric acid-extracted slurry containing deposited silicon particles a little in the content of soluble silica and good in filterability from a water-infused cake. CONSTITUTION:The method for producing the zirconium chloride aqueous solution by extracting the water-infused cake of a zircon sand alkali-treated product with hydrochloric acid is characterized by repulping the water-infused cake with water, continuously feeding the produced slurry and hydrochloric acid into a reaction tank, reacting the produced precursor slurry with the hydrochloric acid, aging the reaction solution, and subsequently subjecting the produced hydrochloric acid-extracted slurry to a solid-liquid separation to provide the zirconium chloride aqueous solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a water-leached cake obtained by treating zircon sand with an alkali and leaching with water.
The present invention relates to a method for producing an aqueous zirconium chloride solution by adding hydrochloric acid to extract a zirconium component, and at the same time insolubilizing a silica component and filtering.

Various zirconium compounds such as zirconium oxychloride, zirconium hydroxide and basic zirconium sulfate are produced from an aqueous zirconium chloride solution. Of these, zirconium oxychloride (hereinafter referred to as ZOC)
Is an important compound as a starting material for zirconia-based ceramics.

[0003]

2. Description of the Related Art Generally, an aqueous zirconium chloride solution is prepared by heating and melting zircon sand with an alkali agent or hydrothermally treating it, and then leaching the obtained reaction mixture with water to elute mainly alkali silicate. It is produced by obtaining a water-leached cake containing as a main component, extracting this with hydrochloric acid to form an aqueous solution of zirconium chloride, insolubilizing the remaining silica content, and filtering. As an improvement of this method, after dissolving the above water-leached cake in concentrated hydrochloric acid in the temperature range of 60 to 100 ° C.,
A method is known in which 2 to 1.0 g / l of gelatin is added, the gel-like silica content is coagulated and precipitated, and then the silica content is separated by filtration.

[0004]

However, the biggest problems in this industrial production method are the poor filterability of silica (SiO ₂ .nH ₂ O) which is insolubilized by acid extraction, and the chlorination after filtration. That is, a large amount of dissolved silica is present in the aqueous solution of the substance. Insoluble silica is extremely difficult to filter because it precipitates in a bulky gel state, and cannot be washed.

Therefore, the size of the filter becomes large, and a considerable amount of the target zirconium component is contained in the silica cake, so that the loss cannot be avoided.

[0006] Even by the method of adding gelatin after dissolving in concentrated hydrochloric acid at a high temperature as described above, the silica that can be removed by adding gelatin is only the particles, and the silica in the dissolved state cannot be removed. It takes several days to polymerize and gel the soluble silica. When a zirconium compound is produced using a zirconium chloride aqueous solution containing soluble silica as a raw material, the silica content is mixed as impurities in the product.

The present invention has been made in view of the above problems, and its purpose is to effectively and efficiently produce precipitated silica particles having a small amount of dissolved silica and good filterability from a water leaching cake. It is an object of the present invention to provide a method capable of producing a hydrochloric acid extraction slurry containing the same, and thereby producing an aqueous zirconium chloride solution suitable for producing ZOC.

[0008]

According to the present invention, an alkali-treated zircon sand is leached with water, and a water-leached cake obtained by filtration is extracted by hydrochloric acid treatment to produce an aqueous zirconium chloride solution. In the method, the water-leached cake is repulped with water to prepare a slurry (hereinafter referred to as repulp slurry), and the slurry and hydrochloric acid are reacted while controlling the slurry pH in the reaction tank within a range of 4 to 10. The precursor slurry is continuously added to the tank and reacted to obtain a precursor slurry, and the precursor slurry is reacted with hydrochloric acid, and then aged to obtain a hydrochloric acid extraction slurry, and the aged hydrochloric acid extraction slurry is solid-liquid. This is a method for producing an aqueous zirconium chloride solution by separating and obtaining an aqueous zirconium chloride solution.

The present invention will be described in detail below.

The treatment of zircon sand with alkali is
Generally, a mixture of zircon sand and caustic soda and / or sodium carbonate is subjected to high-temperature heat treatment (alkali melting) or hydrothermal treatment, and the product varies depending on the reaction conditions. Consists of sodium silicate and unreacted zircon sand. The reaction in this treatment is presumed to be represented by the following formula.

ZrSiO ₄ +6 NaOH → Na ₂ ZrO ₃ + Na ₄ SiO ₄ + 3H ₂ O ↑ ZrSiO ₄ +2 NaOH → Na ₂ ZrSiO ₅ + H ₂ O ↑ ZrSiO ₄ + 2Na ₂ CO ₃ → Na ₂ ZrO ₃ + Na ₂ SiO ₃ + 2CO ₂ ↑ Zr ₄ + Na ₂ CO ₃ → Na ₂ ZrSiO ₅ + CO ₂ ↑ The present invention can be applied to any condition in which these alkali melting and hydrothermal treatment are performed.

When the alkali-treated product thus obtained is leached with water, sodium zirconate is hydrolyzed to produce zirconium hydroxide and caustic soda. The solids obtained by removing sodium silicate and excess alkali by filtration are then water leached cakes. The water leached cake is mainly composed of zirconium hydroxide, sodium zirconate, sodium zirconate silicate and unreacted zircon sand. An example of the composition analysis of a water-leached cake is shown below. This is an example of analysis of a reaction melt obtained by heating and melting at 650 ° C. using caustic soda as an alkaline agent, followed by filtering and washing after leaching with water.

[0013] Most of the contained SiO ₂ is a component of sodium silicate zirconate. The content of sodium silica zirconate in the cake increases or decreases depending on the conditions of alkali treatment. Normal,
The composition of the cake is ZrO ₂ = 30-50 wt%, Na ₂
It is in the range of O = 3 to 10 wt% and SiO ₂ = 1 to 8 wt%. The present invention can be applied to a composition within this range or a composition outside of the range.

The feature of the present invention in the hydrochloric acid extraction of the water-leached cake is that the reaction between the repulp slurry obtained by repulping the water-leaked cake with water and the aqueous hydrochloric acid solution is carried out in two steps.
That is, while further controlling the slurry pH in the reaction tank within the range of 4 to 10, the first-stage preliminary reaction in which the slurry is continuously added to the reaction tank to carry out the reaction, and then the precursor slurry obtained in the preliminary reaction is further added. It consists of a second stage reaction in which the zirconium component is extracted by contacting with hydrochloric acid and the silica component is insolubilized. After the completion of this reaction, aging is carried out, and the zirconium component is extracted and particle growth (polymerization, gelation and aggregation). ) Is completed.

On the other hand, in a known method of reacting hydrochloric acid with a water-leached cake or a slurry obtained by repulping a water-leaked cake with water, one is added to the other, or both are simultaneously added to react with each other. The amount of silica increases, and the silica particles also have extremely poor filterability.

Further, the liquid composition at the end of the hydrochloric acid extraction, that is, the amount of water and hydrochloric acid added to the composition and amount of the water leaching cake, affects the precipitation of silica and the filterability of silica particles. The amount of water for repulping the water-leached cake is preferably such that the slurry can be easily stirred when hydrochloric acid is added. If the amount of water added is too small, it becomes difficult to stir the slurry by itself. However, if hydrochloric acid is added to the slurry, the viscosity of the slurry will rapidly increase due to the sol formation of silica, and the stirring of the slurry will be very difficult. On the other hand, if the amount of this water added is too large, both the ZrO ₂ concentration and the free HCl concentration in the final hydrochloric acid extract will be low, and as a result, the amount of dissolved silica will be high and the filterability of silica particles will also be low. From the above relationship, the amount of water for repulping the water-leached cake and the concentration and amount of hydrochloric acid to be added are such that the ZrO ₂ conversion concentration of the liquid phase of the aged hydrochloric acid extraction slurry becomes 9 to 16 wt% and the free HCl concentration. Is preferably set to 1 to 7 wt%. Even within that range, the ZrO ₂ conversion concentration is 11 to 15 wt% and the free HCl concentration is ₂ to 6 wt%.
% Is more preferable. First, the amount of water to be repulped is preferably adjusted so that the ZrO ₂ content of the slurry before addition of hydrochloric acid falls within the range of 20 to 35 w%. At this time, a part of the filtrate obtained by solid-liquid separation of the hydrochloric acid extraction slurry may be used together with water.

The sum of the amounts of hydrochloric acid added to the water-leached cake slurry in the above first and second stages is the stoichiometric amount required for decomposing zirconium hydroxide, sodium zirconate and sodium silicoconate in the slurry. It is desirable to make the total amount of the stoichiometric amount and the excess amount of the above-mentioned hydrochloric acid extract to make the free HCl concentration 1 to 7 wt%. If the amount is too small, not only the target zirconium content is insufficiently extracted, but also the deposition rate of silica is lowered and the filterability of silica particles is also lowered. On the other hand,
If it is too large, the amount of soluble silica increases.

First, in the first-stage preliminary reaction, the water-leached cake slurry and hydrochloric acid are continuously added to the reaction tank under appropriate stirring. At that time, it is essential to control the pH of the slurry in the reaction tank within the range of 4 to 10, and particularly in the range of 6 to 9 the precipitation rate of silica is high (the amount of dissolved silica is low) and the filterability is improved. This is preferable because it improves the quality. Slurry pH in reaction tank
If it is less than 4 or exceeds 10, the precipitation rate of silica decreases, the amount of dissolved silica increases, and the filterability of silica particles also deteriorates.

The temperature of the preliminary reaction is preferably 40 to 80 ° C., and particularly preferably 60 to 80 ° C. because the silica precipitation rate and filterability are made more effective. The temperature of the water leaching cake slurry at the start is preferably set in advance because heat is generated due to reaction heat and the like. Depending on the slurry composition,
Usually, the slurry temperature at the start may be set to room temperature to 50 ° C.

In order to exert the effect on the deposition rate and filterability of silica, when the preliminary reaction is carried out without extracting the liquid from the reaction tank, the repulp slurry and hydrochloric acid are added for 20 minutes or more, and the reaction tank is removed. When the liquid is continuously drawn out, the staying time is preferably 20 minutes or longer, and particularly, the staying time of 30 minutes to 2 hours is more preferable from the viewpoints of effect and operability. In 20 minutes or less,
The precursor of silica particles is insufficiently produced, resulting in poor filterability and a large amount of dissolved silica.

The precursor slurry obtained by the preliminary reaction is then subjected to a second reaction in which it is brought into contact with the remaining hydrochloric acid, and then aged. The purpose of this reaction and aging is an extremely important operation for accelerating and completing the extraction of zirconium content and the polymerization and gelation of silica. As the operation, hydrochloric acid may be added to the reaction tank containing the precursor slurry, or the precursor slurry and hydrochloric acid may be simultaneously added to the reaction tank. When the preliminary reaction is carried out by continuously withdrawing the liquid, the second reaction is preferably carried out by simultaneously adding the latter precursor slurry and hydrochloric acid. The addition of hydrochloric acid in the former case or the addition of the precursor slurry and hydrochloric acid in the latter case are preferably carried out over 30 minutes or more so that the reaction is not carried out rapidly. The reaction temperature is preferably 60 ° C. or higher, and more preferably 80 ° C. or higher.

When these additions are completed, aging is carried out. The aging may be performed by maintaining the slurry temperature at 80 ° C. or higher and stirring for 4 hours or longer. By this aging, extraction of zirconium and polymerization / gelation of silica are almost completed. If the temperature is too low, the extraction of zirconium and the polymerization / gelling of the silica will be insufficient. Therefore, 80 ° C or higher is preferable, and 90 ° C or higher is more effective. The longer the holding time is, the more the zirconium content is extracted and the silica content is polymerized and gelled. Therefore, the holding time is preferably 4 hours or longer, more preferably 6 hours or longer. The longer one is not limited and may be arbitrarily determined.

Following this reaction and aging, the slurry was
It is preferable to cool to 0 ° C or lower. This cooling is effective in reducing the amount of dissolved silica. Since the lower the temperature is, the lower the solubility of silica is, the temperature is preferably 70 ° C or lower, more preferably 65 ° C or lower. However, if too low, ZOC
Or the slurry viscosity increases and the filterability decreases, so the cooling temperature may be determined in consideration of the amount of dissolved silica, ZOC solubility, liquid physical properties, etc. Usually, up to 50 ° C. is preferable in terms of operability.

After cooling, solid-liquid separation is carried out to remove silica and unreacted zircon sand. Solid-liquid separation may be carried out by an ordinary filtering means such as a filter press, a vacuum suction filter, a precoat pressure filter, or the like. Further, either a batch system or a continuous system can be adopted.

Further, the solid-liquid separation can be more effectively carried out by adding the polymer flocculant. Examples of the polymer flocculant include cationic polymethacrylic acid ester and polyamine; nonionic polyacrylamide and polyethylene oxide. The amount of the polymer flocculant added is not particularly limited, but it is preferable to add 0.5 to 5 parts by weight to 100 parts by weight of SiO ₂ . As an addition method, an aqueous solution is preferably added from the viewpoint of mixing and dispersibility. The time of addition is preferably immediately before solid-liquid separation.

[0026]

According to the present invention, the reason why the silica extraction rate of the hydrochloric acid extraction slurry is high and the filterability of the precipitated silica particles is excellent is presumed as follows.

In the present invention, the acid extraction reaction is carried out in two stages. First, in the preliminary reaction under the condition that the pH was maintained at 4 to 10, polymerization of silica and sol formation were efficiently performed, and then,
Under acidic condition with hydrochloric acid, gelation and aggregation of the sol proceed, silica particle growth is promoted, and flocs are formed. Therefore, it is considered that the filterability of the finally obtained silica precipitated particles is improved and the amount of dissolved silica is reduced.

[0028]

INDUSTRIAL APPLICABILITY According to the present invention, a hydrochloric acid extraction slurry having precipitated silica particles having a small amount of dissolved silica and good filterability can be obtained from a water leaching cake, whereby a high quality zirconium chloride aqueous solution can be effectively used. And it can be manufactured efficiently.

[0029]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto.

The compositional analysis values of the water-leached cakes used in Examples and Comparative Examples are shown below.

ZrO ₂ = 39.2 wt%, Na ₂ O = 8.
08 wt%, SiO ₂ = 5.05 wt%, H ₂ O = 38.
8 wt%, unreacted zircon sand = 8.83 wt% Example 1 68 parts by weight of water was added to 100 parts by weight of the water-leached cake having the above composition and repulped to prepare a raw material slurry. The temperature was 35 ° C. and the slurry pH = 12.4.

A raw material slurry was added at 21 g / min to an 800 ml glass reaction vessel equipped with an overflow tube, and 35 wt% HCl was added to the slurry pH of 9.0 ±.
Simultaneously added to 0.5. The addition rate of hydrochloric acid was 3.3 g / min.

The reaction temperature was 62 ° C. in the steady state. The precursor slurry overflowing from the overflow tube was received in a 2 liter glass separable flask. 1458 g was recovered as a precursor slurry. To this precursor slurry, 755 g of 35 wt% HCl was added at 17 g / min. When the addition of hydrochloric acid was completed, the slurry temperature was 9
It reached 0 ° C. Then, while maintaining the temperature at 90 ° C, stirring was continued for 8 hours, and then the slurry temperature was lowered to 60 ° C.
To this slurry, 114 g of 0.5 wt% polyethylene oxide (referred to as PEO) aqueous solution as a polymer flocculant was added, and after 0.5 hour, suction filtration was performed with a Buchner funnel (inner diameter 20 cm) equipped with a glass fiber filter paper. The time required for filtration was about 2 minutes. Filter cake with warm water 247
After washing with ml, 324 g of a cake consisting of silica particles and unreacted zircon sand, ZrO2 = 12.8 wt%, Na
2250 g of an aqueous zirconium chloride solution consisting of Cl = 5.1 wt%, free HCl = 4.0 wt% and SiO ₂ = 0.018 wt% was recovered.

Comparative Example 1 Water-leached cake 7 was added to 953 g of 35 wt% HCl solution.
Add a slurry of 50 g repulped with 510 g of water,
After stirring at 90 ° C for 8 hours, cool to 60 ° C and add 0.5 wt.
% PEO aqueous solution (114 g) was added, and the slurry was filtered under the same conditions as in Example 1. When about 70 g of the liquid was obtained, filtration became impossible.

Example 2 Hydrochloric acid extraction was carried out under the same conditions as in Example 1 and under the same equipment (two-stage reaction tank). The precursor slurry overflowing from the overflow pipe of the first-stage reaction tank was about 24 g / min, and this slurry and 35 wt% HCl were simultaneously added to the second reaction tank at an addition rate of 20 g / min. 755 as the amount of hydrochloric acid
The addition was stopped when g was added. The temperature was 90 ° C. After continuing stirring for 8 hours while maintaining the temperature of 90 ° C,
The slurry temperature was lowered to 60 ° C., 114 g of a 0.5 wt% PEO aqueous solution was added, and filtration was carried out after 0.5 hour, and the filtration was completed in about 1.7 minutes.

Claims (6)

[Claims] 1. A method for producing an aqueous zirconium chloride solution by subjecting an alkali-treated zircon sand product to leaching treatment with water and extracting the water-leached cake obtained by filtration to obtain an aqueous zirconium chloride solution. Repulp with water to prepare a slurry (hereinafter referred to as repulp slurry),
The pH of the slurry and hydrochloric acid in the reaction tank is adjusted to 4 to 4
The precursor slurry is continuously added to the reaction tank while controlling the content within a range of 10 to obtain a precursor slurry, the precursor slurry is reacted with hydrochloric acid, and then aged to obtain a hydrochloric acid extraction slurry. A method for producing a zirconium chloride aqueous solution, which comprises solid-liquid separating the finished hydrochloric acid extraction slurry to obtain a zirconium chloride aqueous solution. 2. The reaction for forming a precursor slurry is performed in 40
At -80 ° C, the repulp slurry and hydrochloric acid are added to the reaction tank for 20 minutes or more without extracting the liquid from the reaction tank, or the liquid is continuously extracted from the reaction tank and the average residence time is 20 minutes. The method according to claim 1, which is performed under the above conditions. 3. The reaction between the precursor slurry and hydrochloric acid is carried out at 60 ° C.
With the above, hydrochloric acid was added to the reaction tank containing the precursor slurry.
Add over 0 minutes or add the precursor slurry and hydrochloric acid simultaneously into the reaction vessel over 30 minutes,
The method according to claim 1 or 2. 4. The method according to claim 1, wherein the aging is carried out at a temperature of 80 ° C. or higher for 4 hours or longer. 5. A 70 ° C. solution before filtering the hydrochloric acid extraction slurry.
The method according to claim 1, wherein cooling is performed below. 6. The method according to claim 1, wherein a polymer coagulant is added to the slurry before solid-liquid separation of the hydrochloric acid extraction slurry.