JPH07769A - Recovering method for acid - Google Patents

Abstract

PURPOSE:To reutilize harmful waste by converting a sparingly water-soluble metallic salt to a metallic hydroxide, acid and alkali. CONSTITUTION:A recovering method for acid from the metallic salt is to recover the acid and the alkali by allowing the fine particulate sparingly water-soluble metallic salt, preferably having <=1mm particle diameter, to react with an alkaline aq. solution, passing the salt aq. solution after separating the produced metallic hydroxide through an ion exchange membrane electrodializer made by combining a bipolar membrane, an anion exchange membrane and a cation exchange membrane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering an acid, and more particularly to a method for recovering an acid and an alkali from a poorly water-soluble metal salt by using an ion exchange membrane electrodialyzer.

[0002]

BACKGROUND OF THE INVENTION Poorly water-soluble metal salts are discharged from, for example, refining processes in the metal industry, washing processes in the stainless steel industry, tantalum and lead treatment processes, and etching processes in the semiconductor industry. Since this poorly water-soluble metal salt is poorly soluble in water, it is difficult to carry out an aqueous solution reaction, and there is no suitable means such as conversion to other useful compound for recovery, and its disposal is often In this case, it was dumped in a landfill as it was or after it was solidified with cement. However, metal ions forming a poorly water-soluble metal salt, such as cations such as aluminum, chromium, manganese, copper, iron, zinc, cadmium, barium, mercury, and lead, and fluorine in the anion, There are highly toxic substances such as cyanide ions. Therefore, if such a toxic substance is discarded, even if it is a poorly water-soluble metal salt, a trace amount of it may dissolve into rainwater, groundwater, etc., and be mixed into surface water and groundwater. There is a serious situation that cannot be left unchecked.

[0003]

Therefore, the object of the present invention is to:
An object of the present invention is to provide a method for recovering a poorly water-soluble metal salt, which has been discarded so far, by converting it into a metal hydroxide, an acid and an alkali, which can be newly used.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been proposed in order to achieve the above-mentioned object, and is characterized in that a particulate water-insoluble metal salt is treated by a specific method. Later, it is to be recovered as an acid or an alkali by a specific ion exchange membrane electrodialysis device. That is, according to the present invention, a particulate poorly water-soluble metal salt is reacted with an alkaline aqueous solution, and the salt aqueous solution after separation of the produced metal hydroxide is used as a bipolar membrane, an anion exchange membrane and a cation. Provided is a method for recovering an acid from a metal salt, which comprises recovering an acid and an alkali through an ion exchange membrane electrodialyzer that is combined with an exchange membrane.

[0005]

DETAILED DESCRIPTION OF THE INVENTION The important technical features of the present invention are:
A step (A) of reacting a particulate water-insoluble metal salt with an alkaline aqueous solution, a step (B) of separating the metal hydroxide from the reaction solution, and a salt aqueous solution after the metal hydroxide is separated. The point is that the step (C) of recovering the acid and the alkali by passing through an ion exchange membrane electrodialyzer comprising a combination of a bipolar membrane and an anion / cation exchange membrane is combined, and at this time, if necessary, the step (C) The more produced alkali can be used as the alkali in the step (A), or the produced acid can be reused by adding it to the acid cleaning solution.

The sparingly water-soluble metal salt referred to in the present invention includes
Although not particularly limited, those having a solubility in water of 10 g / 100 g or less (20 ° C.) at room temperature are preferable. Such metal salts include metal sulfides, chlorides, fluorides, bromides, iodides, sulfates, phosphates, iodates, bromates, chromates, molybdates, periodates, Oxalate, phthalate, benzoate, mandelate, or chelate-type sparingly soluble salts such as oxynate, 8-oxyquinaldate, dimethylglyoxymate, cuperate, 1-nitroso-2-naphthate, and saltyl. There are aldoximate, N-benzoylphenyl hydroxyaminate, nioximate, quinoxaline-2,3-dithiolate, tris (2-thiopyridine-N-oxide), furfurylaldoximate, flavonate and the like.

Specific examples of metal sulfides include zinc sulfide, aluminum sulfide, antimony sulfide, cadmium sulfide, silver sulfide, chromium sulfide, strontium sulfide, potassium sulfide, tungsten sulfide, titanium sulfide, and sulfide. There are iron, copper sulfide, nickel sulfide, vanadium sulfide, etc., and chlorides include silver chloride, mercury chloride, thallium chloride, lead chloride, etc.

The fluorides include zinc fluoride, aluminum fluoride, yttrium fluoride, iridium fluoride,
Uranium fluoride, osmium fluoride, cadmium fluoride,
Calcium fluoride, Chromium fluoride, Cobalt fluoride, Zirconium fluoride, Mercury fluoride, Sodium fluoride, Strontium fluoride, Cerium fluoride, Tungsten fluoride, Tantalum fluoride, Titanium fluoride, Iron fluoride, Fluoride Copper, thorium fluoride, lead fluoride, nickel fluoride, vanadium fluoride, hafnium fluoride, palladium fluoride, barium fluoride, bismuth fluoride, magnesium fluoride, manganese fluoride, molybdenum fluoride, lithium fluoride, etc. There is.

Examples of the bromide include silver bromide and platinum bromide. Examples of iodides include silver iodide and lead iodide. Examples of the sulfate include silver sulfate, calcium sulfate, yttrium sulfate, gadolinium sulfate, mercury sulfate, strontium sulfate, thallium sulfate, thorium sulfate, lead sulfate, europium sulfate and lanthanum sulfate. As the phosphate, zinc phosphate, aluminum phosphate, calcium phosphate, silver phosphate, cobalt phosphate, mercury phosphate, barium hydrogen phosphate, cerium phosphate, iron phosphate, lead phosphate,
Examples include nickel phosphate, barium phosphate, magnesium phosphate, lithium phosphate and the like. As iodate,
Examples include calcium iodate, silver iodate, potassium hydrogen iodate, and barium iodate.

The bromate includes silver bromate. Chromates include silver chromate, lead chromate, barium chromate and the like. Examples of molybdates include calcium molybdate and lead molybdate. Examples of oxalates include zinc oxalate, uranyl oxalate, calcium oxalate, silver oxalate, cobalt oxalate, potassium hydrogen oxalate, sodium hydrogen oxalate, strontium oxalate, cerium oxalate, iron oxalate, and oxalate. Examples include copper, sodium oxalate, lead oxalate, nickel oxalate, barium oxalate, bismuth oxalate, magnesium oxalate, manganese oxalate, and lithium oxalate. The poorly water-soluble metal salt may be a single salt or a mixture of a plurality of salts.

The poorly water-soluble metal salt is usually solid. The chemical reaction of such a solid proceeds from the surface, and the reaction product on the surface of only a few tens of microns from the surface generally inhibits the internal reaction. Therefore, it is difficult to carry out the aqueous solution reaction of the poorly water-soluble metal salt, and there is no suitable means for converting it into another useful compound.

However, as a result of earnest research, the present inventors have found that
The present invention was found by discovering that a poorly water-soluble metal salt in the form of fine particles can be converted into a metal hydroxide and an aqueous salt solution by reacting the poorly water-soluble metal salt with an alkaline aqueous solution. In particular, a salt in which the metal is iron is likely to undergo hydroxide formation.

Further, when the iron salt is added to a poorly water-soluble metal salt other than the iron salt and a reaction with the alkaline aqueous solution is performed, the other poorly water-soluble metal salt is likely to be converted into a hydroxide. Here, the particle size of the fine particles of the poorly water-soluble metal salt may vary depending on the target substance, reaction temperature, time, etc.
mm or less, preferably 0.5 mm or less.

A known method is used as a method for making the poorly water-soluble metal salt into fine particles, and there is no particular limitation. To pulverize, it is necessary to know the hardness, specific gravity, surface friction coefficient and other properties of the salt, conditions such as humidity and temperature, size, etc., and select a pulverizing method suitable for it. As a crusher used for atomization, jaw crusher, gyratory crusher, cone crusher, roll crusher, edge runner, impact crusher, hammer mill, ball mill, vibrating ball mill, ring roll mill, centrifugal crusher, colloid mill, mixer , Mortar, etc.

As the alkali used in the present invention, any alkali can be used as long as it exhibits alkalinity when it becomes an aqueous solution. Sodium hydroxide, potassium hydroxide, lithium hydroxide, tetramethylammonium hydroxide, ammonia, etc. are used as the aqueous solution. To be If the concentration of the alkali in the aqueous solution is too low, when the salt aqueous solution is electrodialyzed by the ion exchange membrane electrodialysis apparatus in the next step, the salt concentration of the salt aqueous solution becomes low and the current becomes difficult to flow,
Further, if the concentration is too high, it becomes difficult to separate the metal hydroxide and the salt aqueous solution, so the appropriate concentration range is 1 to 40 wt%.
It is preferably 3 to 30 wt%. Further, the higher the temperature range for the reaction with the poorly water-soluble salt, the faster the production of the metal hydroxide, and the easier the separation of the metal hydroxide and the salt aqueous solution. The preferred temperature range is 30 to 10
The temperature is 0 ° C, more preferably 50 to 95 ° C.

In order to further facilitate the separation of the metal hydroxide and the aqueous salt solution, it may be preferable to use an aggregating agent. For example, in addition to the inorganic aggregating agent, a water-soluble polymer aggregating agent may be used. Can be added.

The method for reacting the poorly water-soluble metal salt with the alkaline aqueous solution is not particularly limited, but it is usually preferable to disperse the particulate poorly water-soluble metal salt in the alkaline aqueous solution. As a dispersion method, fine particles of a poorly water-soluble metal salt may be added to an alkaline aqueous solution with stirring, or the reverse operation may be performed. A particularly preferred method is in the presence of an alkaline aqueous solution. It is a method of reacting while grinding a poorly water-soluble metal salt. The reaction time of the poorly water-soluble metal salt and the alkaline aqueous solution is not particularly limited, but it is usually preferable to select it in the range of 1 to 30 hours.

The precipitate generated at this time is a metal hydroxide, and as a method for separating this from a salt aqueous solution, a conventionally known separation method can be adopted without any limitation. The method of separating the metal hydroxide and the salt solution is predominantly the sedimentation / filtration method. Prior to filtration, the concentration of the metal hydroxide, the size of solid particles, the filtration resistance, the compressibility, the dehydratability, and the viscosity of the filtrate are taken into consideration,
The optimum filtration method should be adopted. Gravity filtration, centrifugal filtration, pressure filtration, vacuum filtration, and compression filtration are available as filtration methods. Among them, vacuum filtration is preferable when the filtration resistance is relatively small, and pressure filtration is preferable when it is difficult to filter. Used for. The filtration devices that can be used are bag filter, Nütsche filter, concave plate pressure filter, filter plate filter frame filter, pressure leaf filter, batch vacuum filter, continuous vacuum filter, batch centrifugal filter. Vessel, automatic batch centrifugal filter, continuous centrifugal filter, etc. The lower the water content of the hydroxide separated at this time, the more preferable it is, but it is usually 95% or less, preferably 80% or less. The metal hydroxide generated at this time can be reused in the metal manufacturing process.

In the present invention, the salt aqueous solution obtained by the above treatment is passed through an ion exchange membrane electrodialyzer which is a combination of a bipolar membrane, an anion exchange membrane and a cation exchange membrane to remove acid and alkali. to recover.

In this ion exchange membrane electrodialysis device, conventionally known bipolar membranes can be used without any limitation. For example, one side of a polymer film capable of introducing an ion exchange group is partially covered, the surface of the cover film that is not in contact is sulfonated to introduce a cation exchange group, and then the cover film is peeled off Bipolar membrane in which an anion exchange group is introduced (Japanese Patent Laid-Open No. 55-8682).
1, JP-A-55-99927), a bipolar membrane in which the interface between an anion exchange membrane and a cation exchange membrane is treated with an inorganic compound, and both membranes are joined (JP-A-59-47235). .

The anion exchange membrane is not particularly limited, and a known anion exchange membrane can be used. For example, a quaternary ammonium group, a primary amino group, a secondary amino group, a tertiary amino group, or an anion exchange membrane in which a plurality of these ion exchange groups are mixed can be used. Further, the anion exchange membrane may be of a polymerization type, a condensation type, a homogeneous type or a heterogeneous type, and the presence or absence of a reinforcing core material, a hydrocarbon type, a fluorine type, or an anion derived from a material or a manufacturing method. Any ion exchange membrane may be used regardless of the type and model thereof.

Further, a 2N-salt solution is electrodialyzed at a current density of 5 A / dm ² , and if it has a current efficiency of 70% or more and substantially functions as an anion exchange membrane, it is generally called an amphoteric ion exchange membrane. Even if it is formed, it can be used as the anion exchange membrane of the present invention. Since an anion exchange membrane tends to easily permeate an acid, it is preferable to use an anion exchange membrane that hardly permeates an acid. When producing an oxidizing acid such as nitric acid, it is preferable to use an oxidation-resistant anion exchange membrane.

The cation exchange membrane is not particularly limited, and a known cation exchange membrane can be used. For example, a cation exchange membrane having a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, a sulfuric acid ester group and a phosphoric acid ester group, and a cation exchange membrane in which a plurality of these ion exchange groups are mixed can be used. In addition, cation exchange membranes are classified into polymerization type, condensation type, homogeneous type and heterogeneous type, and the presence / absence of reinforcing core material, hydrocarbon type, fluorine type, and cations derived from materials and manufacturing methods. Any ion exchange membrane may be used regardless of the type and model thereof. Furthermore, 2N-saline solution was added to 5A.
If electrodialyzed at a current density of / dm ² and substantially functioning as a cation exchange membrane having a current efficiency of 70% or more, even if it is generally called an amphoteric ion exchange membrane, It can be used as a cation exchange membrane. A film that is stable, has high current efficiency, and has low electric resistance even in a high hydroxide ion concentration is preferable.

As the ion exchange membrane electrodialysis apparatus comprising a combination of a bipolar membrane, an anion exchange membrane and a cation exchange membrane, a known one can be used, and a three-chamber type electrodialysis tank can be preferably used. FIG. 1 shows a schematic diagram of a three-chamber type bipolar membrane electrodialysis tank. In a three-chamber type bipolar membrane electrodialysis tank, three types of membranes, a bipolar membrane (B) 1, an anion exchange membrane (A) 3 and a cation exchange membrane (C) 2, are used as membranes, and the chambers are made of alkali, acid and salt. Three chambers are formed. Here, the chamber between the cation exchange membrane (C) and the bipolar membrane (B) is the alkali chamber 11, and the bipolar membrane (B).
A chamber between the anion exchange membrane (A) and the anion exchange membrane (A), a chamber between the anion exchange membrane (A) and the cation exchange membrane (C) is a salt chamber 1
3 A typical structure of the electrode and the membrane is the anode- (C-
B-A-) n-C-cathode (where n is the number of repeated cation exchange membranes, bipolar membranes, and anion exchange membranes).

The anion-exchanger side of the bipolar membrane is usually used for the anode side, and the cation-exchanger side is used for the cathode side. In such a three-chamber electrodialysis tank, the salt aqueous solution separated from the precipitate is supplied to the salt chamber. As the method of electrodialysis in the present invention, a salt chamber, an acid chamber, an alkaline chamber, a tank for a liquid to be supplied to each chamber is provided, and a liquid to be supplied to each chamber is provided between each chamber and the liquid tank. A method of circulating can be suitably adopted. Furthermore, when the salt concentration of the salt chamber solution is low,
An electrodialysis tank for concentrating salts can be separately provided in the salt circulation system to keep the salt concentration above a certain level. The desalting solution at this time can be used as a cleaning solution for metal hydroxide.

As a method of extracting the generated acid or alkali, the following method can be preferably adopted. 1. When a thin acid or alkaline aqueous solution is initially charged in the acid chamber and the alkaline chamber respectively to generate an acid or alkali and reach a predetermined concentration, a predetermined amount is withdrawn and water is replenished to the initial acid or alkali concentration. That
The so-called batch method. 2. A continuous method in which an acid or alkaline aqueous solution having a predetermined concentration is charged in advance in the acid chamber and the alkaline chamber, and water is continuously added according to the amount of electricity to be applied during energization to overflow the acid or alkaline aqueous solution having the predetermined concentration.

The temperature of various liquids during the bipolar membrane electrodialysis is usually 5 to 70 ° C., preferably 20 to 50 ° C. The current density is not particularly limited, but is generally 1 to 30 A /
Suitably, it is dm ² , preferably 3 to 20 A / dm ² .

The alkali produced by the above treatment can be reused in the reaction for producing the metal hydroxide and the salt aqueous solution. The generated acid can be used for washing metals and neutralizing waste alkali.

[0029]

According to the present invention, a poorly water-soluble metal salt, which has just been discarded, can be converted into a metal hydroxide, an acid and an alkali by a simple method never considered before. Thus, the present invention greatly contributes to resource saving and pollution prevention.

[0030]

EXAMPLES In order to describe the present invention more specifically, examples and comparative examples will be described below, but the present invention is not limited to these examples.

Example 1 Iron Fluoride (FeF ₃ .3H ₂
200 g of O) was dispersed in 1.20 liters of water, and the resulting mixture was agitated into fine particles in a mixer to obtain a powder having a maximum diameter of 0.4 mm. Then, 2.01 liter of 9.4% potassium hydroxide aqueous solution was added to the mixture while stirring the mixture, the mixture was maintained at 50 ° C. for 10 minutes, and then left for 5 hours. The solution was filtered through No. 5C filter paper to obtain 128 g of ferric hydroxide. Further, a 1.12N potassium fluoride solution was obtained as a filtrate. As shown in FIG. 1, the bipolar membrane electrodialysis tank has a cation exchange membrane (Neoceptor CMX manufactured by Tokuyama Soda Co., Ltd.), a bipolar membrane (Neoceptor BP-1), and an anion exchange membrane (Neoceptor) between a pair of anion and anode. 6 sheets, 5 sheets, 5 sheets (AMH) in order (the effective membrane area of each of the cation exchange membrane, the bipolar membrane, and the anion exchange membrane is 1 dm ² and the total membrane area is 6, respectively).
5,5 dm ² ), using a filter press type bipolar membrane electrodialysis tank in which an alkaline chamber, an acid chamber and a salt chamber are formed, and 2.5 liters of the above potassium fluoride solution is placed in the alkaline chamber. 2 liters of 0.56% KOH aqueous solution and 2 liters of 0.2% HF aqueous solution were supplied and circulated in the acid chamber at a linear velocity of 6 cm / sec. 5 liters of a 10% potassium hydroxide aqueous solution was circulated in each of the anode chamber and the cathode chamber. Electrodialysis was performed at 40 ° C. and a current density of 5 A / dm ² for 3 hours. The voltage at this time was 2 V / unit cell. As a result, 2.2 liters of potassium hydroxide aqueous solution (potassium hydroxide 136.
6 g) and from the acid chamber 2.2 liters (containing 48.8 g hydrofluoric acid) were obtained.

Example 2 Chromium Fluoride (CrF ₃ ) 1
31 g was dispersed in 1.20 liters of water, and agitated into fine particles in a mixer to obtain particles having a maximum diameter of 0.3 mm.
Then, 2.01 liter of a 9.4% potassium hydroxide aqueous solution was added to the mixture while stirring with the mixer, the mixture was maintained at 60 ° C. for 10 minutes, and then left for 10 hours. Filter the solution through No. 5C filter paper,
124 g of chromium hydroxide was obtained. As a filtrate, 1.
A 12N potassium fluoride solution was obtained. As the electrodialysis tank, the same bipolar membrane electrodialysis tank as in Example 1 was used. The salt chamber contained 2.5 liters of the above potassium fluoride solution, and the alkali chamber contained 2 liters of 0.56% KOH aqueous solution. 2 liters of 0.2% HF aqueous solution in each chamber at 6 cm / se
It was supplied and circulated at a linear velocity of c. 5 liters of a 10% potassium hydroxide aqueous solution was circulated in each of the anode chamber and the cathode chamber.
Electrodialysis was performed at 40 ° C. and a current density of 5 A / dm ² for 3 hours. The voltage at this time was 2.2 V / unit cell. As a result, 2.2 liters of an aqueous potassium hydroxide solution (including 140 g of potassium hydroxide) from the alkaline chamber.
However, from the acid chamber, 2.2 liters of a solution (containing 50 g of hydrofluoric acid) was obtained.

Example 3 200 g of lead chloride was pulverized with a ball mill into fine particles having a maximum diameter of 0.2 mm. This was dispersed in 1.44 liters of 4% sodium hydroxide, stirred for 1 hour, and then left at 60 ° C. for 20 hours. Liquid N
Filtration with 5C filter paper gave 160 g of lead hydroxide.
Further, a 1.4N sodium chloride solution was obtained as a filtrate. 1 liter of this sodium chloride solution was supplied to the bipolar membrane electrodialysis cell of Example 1. 1.4 in the salt room
N sodium chloride solution, 1% of 0.4% sodium hydroxide aqueous solution in the alkaline chamber, 0.5% in the acid chamber
1 liter of the hydrochloric acid aqueous solution was supplied and circulated at a linear velocity of 6 cm / sec. 10 anode and 10 cathode chambers
5 liters of a% aqueous sodium hydroxide solution were circulated. 40
Electrodialysis was carried out at a temperature of 5 ° C. and a current density of 5 A / dm ² for 1 hour.
The voltage at this time was 1.8 V / unit cell. As a result, 1.1 liters of sodium hydroxide aqueous solution (including 30 g of sodium hydroxide) from the alkaline chamber
However, 1.1 liters (containing 32 g of hydrochloric acid) of a solution was obtained from the acid chamber.

<Example 4> 218 g of lead sulfate was pulverized in a mortar into fine particles having a maximum diameter of 0.1 mm. 4% for this
The mixture was dispersed in 1.44 liters of sodium hydroxide, stirred for 1 hour, and then left at 60 ° C. for 20 hours. Liquid No. 5C
After filtering through No. filter paper, 160 g of lead hydroxide was obtained. Further, a 1.4N sodium sulfate solution was obtained as a filtrate. 1 liter of this sodium chloride solution was supplied to the bipolar membrane electrodialysis cell of Example 1. The above 1.4N sodium sulfate solution was placed in the salt chamber, 1 liter of 0.4% sodium hydroxide aqueous solution was placed in the alkaline chamber, and 1 liter of 0.5% sulfuric acid aqueous solution was placed in the acid chamber at a line of 6 cm / sec. Supplied and circulated at a speed. 5 liters of a 10% sodium hydroxide aqueous solution was circulated in each of the anode chamber and the cathode chamber. Electrodialysis was performed at 40 ° C. and a current density of 5 A / dm ² for 1 hour. The voltage at this time was 2.0 V / unit cell. As a result, 1.1 liters of a sodium hydroxide aqueous solution (containing 30 g of sodium hydroxide) was obtained from the alkaline chamber, and 1.1 liters (containing 42 g of sulfuric acid) was obtained from the acid chamber.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a three-chamber electrodialysis tank used in Examples.

[Explanation of symbols]

 1 Bipolar Membrane (B) 2 Cation Exchange Membrane (C) 3 Anion Exchange Membrane (A) 11 Alkali Chamber 12 Acid Chamber 13 Salt Chamber 14 Anode 15 Cathode 16 Anode Chamber 17 Cathode Chamber

Claims (1)

[Claims] 1. A bipolar membrane, an anion exchange membrane and a cation exchange membrane, which are obtained by reacting a finely water-insoluble metal salt in a fine particle form with an alkaline aqueous solution and separating the resulting metal hydroxide. A method for recovering an acid from a metal salt, which comprises recovering the acid and the alkali through an ion-exchange membrane electrodialysis device that is a combination thereof.