JP2010260009A - Acid concentrating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acid concentrating method excellent in operability and economical efficiency and enhanced in the concentration efficiency of an acid. <P>SOLUTION: The acid concentrating method is characterized in that a waste acid solution containing Al is pressurized to be supplied to a pressure dialyzer 1, which has a charged separation membrane 2 having micropores of a nanometer unit of preferably 0.1-10 nm, mounted therein and dialyzed by the separation membrane 2 to concentrate the acid in the waste acid solution. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  This invention is a sulfuric acid recovery from an anodized anodizing solution in an aluminum sash manufacturing process, a hydrochloric acid recovery from an aluminum foil etching process with HCl in an aluminum capacitor manufacturing process, a phosphoric acid recovery from a chemical polishing process using phosphoric acid of an aluminum material, The present invention also relates to a method for concentrating the acid in the waste acid solution for the purpose of recovering the acid from the waste acid solution by acid washing or the like.

  Conventionally, as a method for concentrating acid in a waste acid solution, electrodialysis using a potential difference as a driving force, diffusion dialysis method using a concentration difference as a driving force, ion exchange membrane method using an adsorption force as a driving force, pressure A reverse osmosis method using pressure as a driving force, a pressure dialysis method, or the like is used.

Although the electrodialysis method has a good metal removal rate, both capital investment and running cost are high and economically difficult. The diffusion dialysis method is easy to operate, has a good metal removal rate, and the running cost is relatively low. There are drawbacks such as large required membrane area, lack of maintainability, and discharge of waste liquid almost the same as the amount of stock solution.
The ion exchange resin method has a high metal removal rate and a relatively low running cost, but has a high construction cost and a complicated operation.
The reverse osmosis method lacks durability against an acid concentration of pH 2 or lower. It has also been proposed to use pressure dialysis as in the present invention. This method has a good metal removal rate and can reduce the amount of waste acid, but the acid concentration rate is not good.
That is, both methods have advantages and disadvantages.
JP 2003-144858 A

  This invention makes it a subject to obtain the acid concentration method which is excellent in operativity and economical efficiency, and improves an acid concentration rate.

In the acid concentration method of the present invention, a waste acid solution containing Al is pressurized and supplied to a pressure dialysis apparatus equipped with a charged separation membrane having fine pores of nanometer units, preferably 0.1 to 10 nm. The acid in the waste acid solution is concentrated by dialysis with the separation membrane. The amount of fixed charge (fixed charge density) relative to the unit amount of water contained in the membrane is preferably about 0.1 to 10 × 10 ⁻⁸ equivalent / kg.
The concentration of Al in the waste acid solution is preferably 0.01 mol to 2 mol (Claim 2), and if necessary, Al is added or the solution is diluted so that the concentration is in this range. This is because if the Al concentration is not 0.01 mol or more, Al cannot function as a fixed charge, and if it is 2 mol or more, the osmotic pressure increases and dialysis is difficult.
The operation pressure for dialysis is preferably 1 to 7 MPa (Claim 3). This is because when the operating pressure is 1 MPa or less, the flux (the amount of membrane filtrate water per unit time / unit membrane area) is small, and when it is 7 MPa or more, the operation may be hindered due to the pressure resistance of the apparatus.

According to the present invention, are contained in Al in waste acid solution, Al in solution exists as Al ³⁺ ions network structure is believed that this Al ³⁺ ions behave as if it were a fixed charge. Therefore, when the waste acid solution to be treated is a strong acid waste acid solution having a high degree of anion dissociation, both anion and H ⁺ ion permeation through the separation membrane are promoted. The rejection rate can be greatly reduced. On the other hand, in the case of a waste acid solution of a weak acid having a low degree of anion dissociation, the permeation of the H ⁺ ion through the separation membrane is promoted more than the anion, so that the anion is concentrated on the waste acid solution side, The acid rejection rate of the separation membrane can be greatly increased.
Therefore, the waste acid solution containing Al is supplied to the pressure dialysis machine at dialysis pressure and dialyzed to concentrate the acid on the dialysate side in the case of a strong acid and on the waste acid solution side in the case of a weak acid. it can.
Here, the rejection rate is defined by the solute concentration Cc on the supply liquid side through the separation membrane and the solute concentration Cp on the dialysate side, and [rejection rate R = (1−Cp / Cc) × 100 [%]] Is required.
Therefore, it is possible to improve the acid concentration rate in the pressure dialysis method which has the advantages of excellent operability and economy, good metal removal rate and low waste acid amount.

FIG. 1 is a schematic view of a pressure dialysis apparatus used in the acid concentration method of the present invention.
A separation membrane 2 is attached to the inside of the pressure dialysis device 1, and the inside of the pressure dialysis device 1 is separated into a waste acid solution tank 11 and a dialysate solution tank 12 by the separation membrane 2. A supply port 111 for supplying the waste acid solution to be used and an outlet 112 for taking out the waste solution after dialysis are provided, and an outlet 122 for taking out the dialysate is provided in the dialysate tank 12.
The separation membrane 2 has a structure having a large number of fine pores of nanometer units (0.1 to 10 nm). When a waste acid solution is supplied to the waste acid solution tank 11 side and pressure is applied, water and acid are permeated. However, metals and organic substances having a large molecular weight do not permeate. The micropores have a charged group such as a lower amino group or a quaternary ammonium base, and the fixed charge density is about 0.1 to 10 × 10 ⁻⁸ equivalent / kg.

The waste acid solution supplied to the waste acid solution tank 11 contains Al at a concentration of 0.01 to 2 mol. If the Al concentration of the waste acid solution is higher than this, it is diluted and adjusted to this range, and if it is lower than this, Al is added. The waste acid solution is subjected to pressure dialysis by applying a pressure of 1 Mpa to 7 Mpa to permeate the separation membrane.
When the waste acid solution contains Al, when the acid to be concentrated is a strong acid such as sulfuric acid, both anions such as SO ₄ ²⁻ and H ⁺ ions permeate through the separation membrane. The acid rejection rate of the separation membrane becomes a negative value, and the sulfuric acid is concentrated on the dialysate 12 side. On the other hand, in the case of a weak acid such as phosphoric acid, the permeation of H ⁺ ions through the separation membrane is promoted more than that of an anion such as PO ₄ ^3−, so that the acid rejection rate of the separation membrane is increased to a positive value. Phosphoric acid is concentrated on the waste acid liquid tank 11 side.
Therefore, it is possible to improve the acid concentration rate in the pressure dialysis method that has the advantages of excellent operability and economy, good metal removal rate and low waste acid amount.

  Examples and comparative examples in which Al is added to the waste acid solution and pressure dialysis is performed and in which pressure dialysis is performed without adding Al are shown below.

すなわち、廃酸液にＡｌを添加した場合、分離膜２のＨ_２ＳＯ_４の透過が促進され、透析液漕１２側においてＨ_２ＳＯ_４を濃縮することができる。 [Example 1 / Comparative Example 1] Example of strong acid Pressure when Al 16 g / l (0.6 mol / l) was added to a waste acid solution containing 143 g / l of H ₂ SO ₄ and when Al was not added Dialysis was performed to obtain the results shown in Table 1 (temperature: 44 ° C., dialysis pressure: 5 MPa, micropore size: 0.1 to 1 nm, charged group type: amino group, fixed charge density: (1 to 10 ) × ^{10 -8} eq / _kg-H 2 O).

That is, when Al is added to the waste acid solution, permeation of H ₂ SO ₄ through the separation membrane 2 is promoted, and H ₂ SO ₄ can be concentrated on the dialysate tank 12 side.

すなわち、廃酸液にＡｌを添加した場合、分離膜２のＨＣｌの透過が促進され、透析液漕１２側においてＨＣｌを濃縮することができる。 [Example 2 / Comparative Example 2] Example of strong acid Pressure dialysis was carried out in the case where Al 5.0 g / l (0.19 mol / l) was added to the waste acid solution containing 179 g / l HCl and in the case where Al was not added. The results shown in Table 2 were obtained (temperature: 40 ° C., dialysis pressure: 5 MPa, micropore size: 0.1 to 1 nm, charged group type: amino group, fixed charge density: (1 to 10) × ^10-8 eq / _kg-H 2 O).

That is, when Al is added to the waste acid solution, permeation of HCl through the separation membrane 2 is promoted, and HCl can be concentrated on the dialysate tank 12 side.

すなわち、廃酸液にＡｌを添加した場合、分離膜２のＨ_３ＰＯ_４の透過が抑制され、廃酸液漕１１側においてＨ_３ＰＯ_４を濃縮することができる。 [Example 3 / Comparative Example 3] Example of weak acid When Al 1.9 g / l (0.07 mol / l) was added to a waste acid solution containing 163 g / l of H ₃ PO ₄ and when Al was not added The results shown in Table 3 were obtained (room temperature, dialysis pressure: 3 MPa, micropore size: 0.1-1 nm, charged group type: amino group, fixed charge density: (1-10) × ^{10 -8} eq / _kg-H 2 O).

That is, when Al is added to the waste acid solution, permeation of H ₃ PO ₄ through the separation membrane 2 is suppressed, and H ₃ PO ₄ can be concentrated on the waste acid solution tank 11 side.

  The present invention relates to a method for concentrating an acid in a waste acid solution for the purpose of recovering acid from various waste acid solutions, and has industrial applicability.

Schematic diagram of a pressure dialysis apparatus used in an embodiment of the present invention

DESCRIPTION OF SYMBOLS 1 Pressure dialysis machine 11 Waste acid liquid tank 12 Dialysate liquid 2 Separation membrane

Claims (3)

Pressurize and supply Al containing waste acid solution to a pressure dialysis machine equipped with nanometer-scale micropores and a charged separation membrane, and concentrate the acid in the waste acid solution by dialysis on the separation membrane. And a method for concentrating the acid. The acid concentration method according to claim 1, wherein the Al concentration of the waste acid solution is 0.01 mol to 2 mol. The acid concentration method according to claim 1 or 2, wherein the dialysis operation pressure is 1 to 7 MPa.

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