TWI615363B - Method for decreasing the concentration of at least one contamination cation in an electrolytic solution - Google Patents

Abstract

The invention provides a method for reducing the content of polluting cations in an electrolyte. The highly toxic cation can utilize its reduction potential property to provide a suitable reduction potential through a deionization circulation system to reduce and solidify against specific polluting cations. Adsorption is carried out to reduce its concentration in the electrolyte. The method can effectively reduce the content of polluting cations in the electrolyte and improve the service life of the anode treatment without affecting the anodizing process. The main principle is to apply a porous electrode through an external electric field between the two electrodes. Forming an electrostatic field, so that the charged ions in the solution are driven by the electrostatic force to move toward the oppositely charged electrode. At this time, an electric double layer is formed between the electrode and the solid-liquid interface of the electrolyte to separate the contaminant. The purpose.

Description

Method for reducing concentration of at least one contaminating cation in an electrolyte

The invention relates to a method for reducing the content of polluting cations in an electrolyte. The method has the characteristics of reducing the amount of specific ions, reducing the pollution of the electrolyte, improving the purity of the coating, and reducing the discharge of the process.

Aluminum anode treatment is one of the most commonly used surface treatment technologies for aluminum and aluminum alloys. It can produce a continuous coating of metal oxide on the surface of the workpiece. It can control the formation of oxide film by electrochemical method to prevent oxidation of aluminum. It can increase the mechanical properties of the surface, hardness, corrosion resistance, wear resistance, heat resistance, voltage resistance and other special functions. It can also produce a decorative color by different chemical reactions. The resulting oxide film is widely used in various industries, including: semiconductor and optoelectronic industry, biomedical medical equipment, mechanical assembly applications, automobile and motorcycle industry, aerospace industry, food equipment, etc.

The nature of the oxide film in the anodizing process depends on the electrolyte formulation and the applied voltage and current control, and the contaminating cations precipitated in the process will adversely affect the electrolyte and film quality and stability, especially for The workpiece materials in the semiconductor and optoelectronic fields are highly polluting copper, sodium, and potassium ions. The contaminating cation is easily sandwiched into the cellular tube structure of the membrane, and can generally be removed by a post-processing procedure, but the procedure is complicated and improved. Process cost issues. In order to simplify the process, the concentration of polluting cations in the electrolyte can be directly reduced during the process. However, the electrolyte contains a plurality of reactive ions, and it is difficult to use a general chemical treatment method to reduce the contaminated ions in the electrolyte during the electrochemical process. The content is generally controlled by the discharge of the electrolyte to control the ion concentration. This method is also time consuming, costly, and increasing the amount of waste is not environmentally friendly.

Generally, the adsorption of metal ions can be treated by chemical activity, and the adsorption of the metal itself is utilized for adsorption. The higher the activity is the reducing agent, the lower the activity is the oxidant, and the metal activity is: potassium>sodium>钡>锶>calcium> Magnesium>aluminum>carbon>zinc>chromium>iron>cobalt>nickel>tin>lead>hydrogen>copper>mercury>silver>platinum>gold, in order to not affect the composition of the bath, aluminum metal is used in the aluminum anode treatment process It has lower adsorption activity than metal ions such as zinc, chromium, iron, cobalt, nickel and copper. However, this method has its own limitations, such as potassium, sodium and other highly active ions in the semiconductor industry, which is difficult to remove by this method.

Accordingly, it would be desirable to provide a novel method of reducing the concentration of at least one contaminating cation in an electrolyte to address the problems of the prior art.

It is an object of the present invention to provide a method for reducing the concentration of at least one contaminating cation in an electrolyte. The highly contaminating cation can utilize its reduction potential characteristics to provide a suitable reduction potential for specific contamination through a deionization cycle system. The cation is reduced and solidified, and adsorption is carried out to lower its concentration in the electrolyte. This method can effectively reduce the content of polluting cations in the electrolyte without affecting the anodizing process. The invention is applicable to aluminum anode treatment mainly composed of phosphoric acid, sulfuric acid, boric acid, oxalic acid, chromic acid, or a combination thereof.

The capacitor deionization method is a method of removing inorganic salts in water to achieve water desalination. A novel technique that uses an externally biased electrosorption mechanism to separate charged species in water. The main principle is that the porous activated carbon is used as an electrode, and an electrostatic field is formed between the two electrodes by the application of an external electric field, so that the charged ions in the solution are driven by the electrostatic force to move toward the oppositely charged electrode. At this time, an electric double layer is formed between the electrode and the solid-liquid interface of the electrolyte to achieve the purpose of separating the contaminants. This method must be combined with a porous electrode to increase the adsorption capacity by improving the characteristics of the active surface area. The porous electrode plate material may include activated carbon, stainless steel, aluminum, lead, or a metal material having better chemical stability, such as Precious metals, etc.

Active elements, for example, aluminum are easily oxidized, although the oxide layer has a certain passivation effect, but as a result of long-term exposure, the oxide layer will still peel off and lose the protective effect. Therefore, the purpose of the anode treatment is to utilize its oxidative properties by electrochemical method. The formation of an oxide layer is controlled to prevent further oxidation of the aluminum material while increasing the mechanical properties of the surface. Common anodizing techniques include ordinary anodizing, micro-arc anodic treatment, and hard anodizing. When the anode is treated, some parts of the surface of the aluminum anode begin to dissolve, and the time increases, the amount of aluminum dissolved increases, but the surface of the anode begins to emboss. The unevenness of the thickness, the time continues to increase, the dissolution rate is different due to the unevenness, and the faster dissolved portion is gradually depressed. At the same time, the dissolved aluminum ions gradually form aluminum hydroxide and alumina deposited on the surface, but still remain. The pores are allowed to continue the dissolution reaction. After a long time, the deposited precipitate forms a "tube wall", and the main component of the tube wall is aqueous alumina or colloidal aluminum hydroxide.

The control of the applied bias voltage can be controlled for a particular contaminating cation, as shown in Figure 3. This figure is a cyclic voltammetry measurement. Cyclic voltammetry is an extension of linear sweep voltammetry. It is very effective for the characterization of redox couples. It is measured by applying a cyclic potential. Its responsive redox current. Mainly to find the redox peak in an unknown electrochemical system, confirm the potential range of redox, and Peak potential and peak current were used to evaluate the electrochemical properties of the system. Figure 3 is a typical CV curve. The A→B point indicates that the potential is not enough to oxidize the species, and the B→C point potential gradually becomes capable of oxidizing the species, while the D point is the maximum oxidation potential value at which the species is completely oxidized. Due to the concentration polarization, the D→F point current gradually decreases, and from the H→I point, it gradually has the ability to reduce the species, and the J point is the maximum reduction potential value of the species. Therefore, from the CV curve, we can obtain anode peak current (ipa) and peak voltage (Epa), cathode peak current (ipc) and peak voltage (Epc).

In the present invention, if the metal cation is to be adsorbed and solidified, the cathode peak current (ipc) and peak voltage (Epc) of the selected ion can be referred to; if the anion is to be adsorbed, the anode peak current (ipa) and peak voltage of the selected ion can be referred to. (Epa). Under the operation of the cathode peak voltage, the selected contaminating metal ions will be reduced to the metal of the zero valence state and adhered to the surface of the negative electrode. Since the conductivity of the metal is good, the adsorption is continued for a long time, and the adsorbent shielding does not occur. Causes the problem of decreased adsorption.

1‧‧‧Anode treatment equipment

2‧‧‧Deionization Circulation System

10‧‧‧Anode treatment tank

11‧‧‧ electrolyte

12‧‧‧Contaminant cations

13‧‧‧Contaminant anions

20‧‧‧ tank

21‧‧‧Water pipeline

22‧‧‧Water pipe

23‧‧‧ pump

24‧‧‧ positive electrode

25‧‧‧Negative electrode

26‧‧‧ Mixing device

27‧‧‧Power supply

A-K‧‧ points

S11-S14‧‧‧Steps

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing the steps of a method for reducing the concentration of at least one contaminating cation in an electrolyte in an embodiment of the present invention.

Fig. 2 is a schematic view showing the structure of an anode treating apparatus and a deionizing circulation system in an embodiment of the present invention.

Figure 3 is a current-potential diagram of cyclic voltammetry.

Figure 4 is an analysis of cyclic voltammetry.

The invention will be further described below in conjunction with the embodiments.

Please refer to FIGS. 1 and 2, and FIG. 1 is a diagram of reducing electrolyte 11 in an embodiment of the present invention. A flow chart of the steps of the method for at least one concentration of the contaminating cation 12, the method comprising the following steps; and FIG. 2 is a schematic view showing the structure of the anode treating apparatus 1 and the deionizing circulation system 2 according to an embodiment of the present invention.

In step S11, an anode treatment apparatus 1 is provided, the anode treatment apparatus 1 comprising an anode treatment tank 10 containing an electrolyte 11 containing at least one contaminating cation 12. In this embodiment, the anode processing apparatus 1 may be in an operating state or a shutdown state. The coating process of the anode treating apparatus 1 may include ordinary anodizing, micro-arc anodic treatment, and hard anodizing, but the invention is not limited thereto. The electrolytic solution 11 is an aluminum anode treatment liquid containing phosphoric acid, sulfuric acid, boric acid, oxalic acid, chromic acid, or a mixture thereof, but the present invention is not limited thereto. The at least one contaminating cation 12 contains one or more of potassium, sodium, rubidium, cesium, calcium, magnesium, strontium, zinc, carbon, chromium, iron or copper, but the invention is not limited thereto.

In step S12, a deionization circulation system 2 is provided. The deionization circulation system 2 includes: a tank body 20; a water inlet pipe 21 communicating with the anode treatment tank 10 and the tank body 20; and a water outlet pipe 22 communicating with the water supply pipe 22 The tank body 20 and the anode treatment tank 10, wherein the anode treatment tank 10, the water inlet pipe 21, the tank body 20 and the water outlet pipe 22 constitute a circulation passage; a pump 23 is disposed in the circulation passage, the pump The pump 23 is for circulating the electrolyte 11 in the circulation passage; a positive electrode 24 is disposed in the tank 20; and a negative electrode 25 is disposed in the tank 20. The positive electrode 24 and the negative electrode 25 may each be a flat electrode or a porous electrode. The positive electrode 24 may be made of a metal material having a good chemical stability, such as a noble metal such as gold or platinum. The negative electrode 25 may be made of activated carbon, stainless steel, aluminum or lead. In this embodiment, the tank body 20 further includes a stirring device 26 for increasing the moving speed of the ions.

In step S13, the at least one of the electrolytes 11 is analyzed by cyclic voltammetry. The reduction potential of the contaminating cation 12. The reduction potential of the at least one contaminating cation 12 is the maximum reduction potential value of the cyclic voltammetry curve obtained by the cyclic voltammetry. For example, referring to Fig. 4, the reduction potential of copper ions is -2.0 V (Ag/Cl).

In step S14, the reduction potential is applied to the positive electrode 24, so that the at least one contaminating cation 12 is adsorbed on the surface of the negative electrode 25, and is reduced and solidified on the surface. When at least two contaminating cations 12 need to be simultaneously reduced and solidified on the surface, a larger reduction potential of the reduction potentials of the at least two contaminating cations 12 may be applied to the positive electrode 24.

Hereinafter, a specific embodiment (Examples 1-3) will be described in detail with reference to the above examples to further explain the method of reducing the concentration of at least one contaminating cation in the electrolyte of the present invention.

Example 1

The constant potential is used to reduce the copper ion content in the electrolyte 11, the planar aluminum is used as the negative electrode 25, the inert metal platinum is used as the positive electrode 24, and the simulated electrolyte 11 contains 1-20 vol.% H ₂ SO ₄ and 1 30 g/L Cu ^{2 . +} ion, the copper adsorption amount test was performed in a two-electrode system (that is, the positive electrode 24 and the negative electrode 25). The detailed test is that the simulated electrolyte 11 contains 10 vol.% H ₂ SO ₄ and 5 g/L Cu ²⁺ ions, and the measurement results of the cyclic voltammetry at a scanning rate of 0.1 V/s are as shown in Fig. 4. The reduction peak of copper ions was -2.0 V (Ag/Cl). For this two-electrode system, an external bias voltage of -2.0 V was applied to the power supply 27 for one hour, and the adsorption rate of the adsorbed solid copper was calculated to be 7.85 ppm/hr. Cm ² . Purely utilizing metal active adsorption, the adsorption rate is 0.35ppm/hr without external bias. Cm ² . The adsorption rate is increased by 22 times, and under voltage control, side reactions are less likely to occur.

Example 2

The potentiostatic method is combined with the porous foamed aluminum to reduce the copper ion content, and the porous aluminum foam is used as the negative electrode 25. In order to increase the active area to enhance the adsorption rate, the simulated electrolyte 11 contains 10 vol.% H. ₂ SO ₄ and 5 g/L Cu ²⁺ ions were tested for copper adsorption using a two-electrode system. Its copper ion reduction peak is -2.0V. For this two-electrode system, an external bias voltage of -2.0 V was applied to the power supply 27 for one hour, and the adsorption rate of the adsorbed solid copper was calculated to be 40.00 ppm/hr. Cm ² . Compared with the use of a planar aluminum electrode, the adsorption rate is increased by 5 times. The amount of adsorbed cations can be greatly increased by the electrode material of the mesoporous or microporous.

Example 3

The potentiostatic method is used in combination with the stirring device to reduce the copper ion content, and the planar aluminum is used as the negative electrode 25, and the simulated electrolyte 11 contains 10 vol.% H ₂ SO ₄ and 5 g/L Cu ²⁺ ions, and is applied to the deionization system 2 A stirring device of 200 rpm speed is used to enhance the diffusion movement of ions in the electrolyte 11, reduce the excessive accumulation of ions in the electric double layer, and reduce the ion concentration gradient to cause a decrease in the adsorption rate. For this two-electrode system, an external bias voltage of -2.0 V was applied from the power supply 27, and the reduction current value was observed. The stirring current value was raised to 7.3 mA/cm ² from the current density of 3.5 mA/cm ² when no stirring was applied while the stirring device was being stirred. It can greatly increase the adsorption rate of polluting cations.

As described above, the method for reducing the concentration of at least one contaminating cation in the electrolyte of the present invention is a cyclic voltammetry method for analyzing the reduction potential of the at least one contaminating cation 12 in the electrolyte 11, and then applying the positive electrode 24 The reduction potential is such that the at least one contaminating cation 12 is adsorbed on the surface of the negative electrode 25 and is reduced and solidified on the surface, thereby reducing the amount of the specific ions, reducing the contamination of the electrolyte, improving the purity of the coating, and reducing the thickness. Characteristics of wastewater discharged from the process.

The present invention has been disclosed in its preferred embodiments, and is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is defined by the scope of the patent application attached Subject to it.

S11-S14‧‧‧Steps

Claims (9)

A method for reducing the concentration of at least one contaminating cation in an electrolyte comprises the steps of: (1) providing an anode treatment apparatus, the anode treatment apparatus is in operation, and the anode treatment apparatus comprises an anode treatment tank, the anode treatment tank The electrolyte solution comprises at least one contaminating cation; (2) providing a deionization circulation system, the deionization circulation system comprising: a tank body; a water inlet conduit connecting the anode treatment tank and the tank body a water outlet pipe connecting the tank body and the anode treatment tank, wherein the anode treatment tank, the water inlet pipe, the tank body and the water outlet pipe form a circulation passage; a pump is disposed in the circulation passage, the pump Pu is used to circulate the electrolyte in the circulation channel; a positive electrode is disposed in the tank; and a negative electrode is disposed in the tank; (3) the electrolyte is analyzed by cyclic voltammetry a reduction potential of the at least one contaminating cation to confirm a reduction potential range of the contaminating cation, wherein the reduction potential of the at least one contaminating cation is One of the maximum reduction potential values of one of the cyclic voltammetry curves obtained by the cyclic voltammetry; and (4) applying the reduction potential to the positive electrode to adsorb the at least one contaminating cation on the surface of the negative electrode and to reduce and cure On the surface. The method of reducing the concentration of at least one contaminating cation in the electrolyte according to claim 1, wherein the coating process of the anode treating apparatus comprises ordinary anode treatment, micro-arc anode treatment, and hard anode treatment. A method for reducing concentration of at least one contaminating cation in an electrolyte according to claim 1, wherein the at least one contaminating cation comprises potassium, sodium, rubidium, cesium, calcium, magnesium, strontium, zinc, carbon, chromium One or more of iron or copper. A method for reducing the concentration of at least one contaminating cation in an electrolyte as described in claim 1, wherein the negative electrode is a flat electrode or a porous electrode. A method for reducing the concentration of at least one contaminating cation in an electrolyte as described in claim 4, wherein the negative electrode is composed of activated carbon, stainless steel, aluminum or lead. A method of reducing the concentration of at least one contaminating cation in an electrolyte as described in claim 1, wherein the electrolyte comprises phosphoric acid, sulfuric acid, boric acid, oxalic acid, chromic acid, or a mixture thereof. A method for reducing the concentration of at least one contaminating cation in an electrolyte as described in claim 1, wherein the tank further comprises a stirring device. A method for reducing the concentration of at least one contaminating cation in an electrolyte as described in claim 1, wherein the at least two contaminating cations may be applied to the surface while being simultaneously reduced and cured on the surface. The larger reduction potential of the reduction potential of the two contaminating cations. A method for reducing the concentration of at least one contaminating cation in an electrolyte as described in claim 3, wherein the reduction potential of the copper ion is -2.0 V (Ag/Cl).