Separation method of acetic acid in electronic waste acid solution

Abstract

The invention relates to the technical field of recycling of waste acid liquid in the electronic industry, in particular to a method for separating acetic acid from electronic waste acid liquid. The method comprises the following steps: filtering the electronic waste acid solution to remove mechanical impurities, and then separating acetic acid by adopting an adsorption rectification method to obtain a dilute acetic acid product; the content of acetic acid in the residual acid liquor is less than 5000 PPM. In the adsorption rectification method, a molecular sieve is used as an adsorbent. According to the method, the acetic acid in the waste acid is separated, purified and recycled, the utilization value is improved, the content of the acetic acid in the distillation residual liquid is controlled to be smaller than or equal to 5000 ppm, the acetic acid is a carbonaceous organic matter, and the explosion risk can be controlled when the residual nitric acid and phosphoric acid mixed acid is utilized in ammonification by controlling the content of the acetic acid.

Description

Technical Field

[0001] The invention relates to the technical field of recycling waste acid liquid in the electronics industry, and in particular to a method for separating acetic acid from waste acid liquid in the electronics industry. Background Art

[0002] In the electronics industry, especially in the thin-film transistor liquid crystal display (TFT-LCD), light-emitting diode (LED) and organic light-emitting diode (OLED) industries, my country has become the world's largest display production base.

[0003] In the manufacturing process of liquid crystal panels, etching solutions composed of nitric acid, phosphoric acid, and acetic acid are often used in the aluminum-based electrode etching section and the aluminum alloy interconnection line etching section in the semiconductor manufacturing process. The etching waste liquid and cleaning solution after use contain mainly phosphoric acid, as well as nitric acid, acetic acid, and the elements such as aluminum, molybdenum, and iron that are produced by etching. This type of waste liquid will appear transparent, light yellow, or different shades of blue due to the different contents of elements such as molybdenum, and this part of the waste liquid needs to be treated. There have been many studies on the treatment of waste acid liquid at home and abroad, mainly including distillation, extraction, precipitation and other treatment methods. These methods all have the difficulties of difficult separation of nitric acid and acetic acid, difficult separation and recycling of metal elements, large investment, high energy consumption, or low product value.

[0004] CN 11530451 A provides a method for recycling waste phosphoric acid to produce urea phosphate. The patent mentions that acetic acid and nitric acid are difficult to separate, so acetic acid and nitric acid are evaporated in the form of mixed acid by adding water to achieve the recycling of phosphoric acid. The mixed acid evaporated by this method is still difficult to be reused. If nitric acid and acetic acid can be separated, it will have better economic value. More water is added to evaporate nitric acid and acetic acid, and the added water also needs to be evaporated, so more energy consumption is required. Summary of the invention

[0005] The purpose of the present invention is to provide a method for separating acetic acid from electronic waste acid liquid in view of the problems existing in the current prior art; through this method, the separation, purification and recovery of acetic acid in waste acid can be better achieved, thereby improving the utilization value.

[0006] In order to achieve the above invention object, the technical solution of the present invention is as follows:

[0007] A method for separating acetic acid from waste electronic acid liquid comprises the following steps: filtering the waste electronic acid liquid to remove mechanical impurities, and then separating acetic acid by an adsorption distillation method to obtain a dilute acetic acid product; the acetic acid content in the residual liquid after the adsorption distillation is less than 5000 PPM, thereby reducing the explosion risk in the process of directly neutralizing the residual acid with ammonia to produce ammonium nitrate phosphorus for fertilizer, and meeting the safety requirements of ammonia neutralization.

[0008] Preferably, in the method for separating acetic acid from waste electronic acid liquid, a molecular sieve is used as an adsorbent in the adsorption distillation method. More preferably, the molecular sieve is a 5A molecular sieve.

[0009] Preferably, in the adsorption distillation method, a composite heat-resistant polymer plastic loaded with 5A molecular sieve adsorbent is used as the adsorption distillation material.

[0010] Preferably, in the adsorption distillation method, the adsorption distillation material can be processed into Raschig rings or plate corrugations as required.

[0011] Preferably, the adsorption distillation material is prepared by blending and modifying 5A molecular sieve, PP, solid cyano resin powder modifier and glass fiber; based on 100 mass percentage, the amount of 5A molecular sieve added is 10-20%, the solid cyano resin powder modifier is 5-10%, the glass fiber is 15-30%, and the balance is pp.

[0012] In the adsorption and distillation material, cyano resin, as a high-temperature resin, has the function of improving the heat resistance of the filler, and the presence of cyano is more conducive to the adsorption of nitro and nitrogen oxides; if the molecular sieve adsorption filler is added in too low an amount of molecular sieve, the adsorption effect cannot be guaranteed, and if the molecular sieve is added in too high an amount, the mechanical properties of the material will be affected; if the cyano resin is added in too low an amount, the heat resistance will be affected, and the adsorption performance will also be affected; if the amount is added in too much, the cost of the cyano resin is too high, which affects the economy of the material.

[0013] Preferably, the adsorption distillation material is a 1-2 mm thin-walled material or a thin plate material. If it is too thin, it will affect the mechanical properties, and if it is too thick, the molecular sieve and the cyano resin surface will not be sufficiently exposed, affecting the performance.

[0014] Preferably, in order to further reduce the operating temperature and energy consumption, the distillation is performed by vacuum distillation.

[0015] The above method for separating acetic acid from electronic waste acid liquid comprises the following specific steps:

[0016] The electronic waste acid liquid is filtered to remove mechanical impurities; then the electronic waste acid is preheated and then the adsorption distillation method steps are started, first entering the middle part of the distillation tower, and exchanging vapor and liquid with the acetic acid, water, and nitrogen oxide vapor mixture from the lower section of the distillation tower in the packing layer; phosphoric acid and most of the unvaporized nitric acid and metal ion impurities pass through the lower section packing bed into the tower kettle, and nitrogen oxide, water, and acetic acid are further adsorbed and exchanged vapor and liquid in the upper section, and the acetic acid and water liquid refluxed from the top of the tower are further eluted, so that the rising acetic acid and water are purified and separated, and the acetic acid and water vapor out of the top of the tower are condensed by a condenser to obtain an acetic acid solution, part of the acetic acid solution is returned for use as a reflux elution liquid, and the rest is extracted as a product.

[0017] Preferably, a heater or a reboiler is provided at the bottom of the distillation tower as a heat source supply measure.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (I) The adsorption distillation process is used to effectively solve the problem of azeotropic separation of nitric acid and acetic acid. Nitric acid is retained in phosphoric acid, and acetic acid and part of water are separated by distillation.

[0020] (ii) The acetic acid content in the distillation residue is ≤5000ppm. Acetic acid is a carbon-containing organic matter. Controlling its content can control the explosion risk of the remaining nitric acid and phosphoric acid mixed acid when it is neutralized by adding ammonia.

[0021] (III) The distilled acid can be blended and neutralized with ammonia to produce fertilizer-grade ammonium phosphate products containing ammonium nitrate phosphate, thereby realizing better economic value.

[0022] (IV) The adsorption distillation process described in the present invention is compared with the water distillation process described in patent CN11530451A. Only acetic acid and part of the water originally present in the waste acid, which account for a relatively low proportion, need to be distilled out, and there is no need to distill out the added water, which has lower energy consumption.

[0023] (V) In this method, a preferred adsorption distillation material is used as a filler, and the filler is suitable for separating acetic acid from a mixed solution of nitric acid, acetic acid and water by adsorption distillation, which effectively solves the problem of difficult separation of nitric acid and acetic acid, realizes separation, purification and recovery of acetic acid in waste acid, and improves the utilization value. Compared with the enamel corrugated plate structured filler mentioned in CN 115304514A, the molecular sieve modified adsorption distillation material is light in weight, easy to install, easy to repair, and has low requirements on the internal support structure of the tower.

[0024] (VI) The molecular sieves used as adsorption materials are mixed. The molecular diameter of acetic acid is about 0.85nm. The nitric acid exists in the form of water and nitrogen dioxide during evaporation. The molecular diameter of nitrogen dioxide is about 0.36nm and the diameter of water is about 0.4nm. A molecular sieve with a micropore diameter of about 5A is selected. Nitric oxide can enter, but acetic acid cannot. The adsorption material changes the ratio of nitric acid and acetic acid at the microinterface in the packing bed. Nitric acid and acetic acid are no longer in an azeotropic state. The vapor-liquid and gas-gas separation is achieved under the full distribution of the distillation packing bed and the action of the reflux washing liquid. Finally, the acetic acid is evaporated alone, and the evaporation rate is >99%; the azeotropic point of the mixture of nitric acid and water is higher than the boiling point of the acetic acid aqueous solution. In addition, due to the adsorption effect of the molecular sieve, acetic acid will be preferentially evaporated from the top of the distillation tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic flow chart of a method for separating acetic acid from waste electronic acid solution in Example 1 of the present invention;

[0026] Among them, 1 is reflux condenser, 2 is reflux ratio regulator, 3 is distillation column, 4 is loaded molecular sieve Raschig ring packing, 5 is flask, 6 is electric heating jacket, 7 is receiving bottle, and 8 is vacuum pump.

[0027] Figure 2 This is a schematic flow chart of a method for separating acetic acid from waste electronic acid solution in Example 2 of the present invention;

[0028] 1 - waste acid storage tank, 2 - filter, 3 - feed pump, 4 - preheater, 5 - distillation tower, 6 - upper section of distillation tower loaded with molecular sieve plate corrugated packing, 7 - lower section of distillation tower loaded with molecular sieve plate corrugated packing, 8 - distillation tower kettle, 9 - top condenser, 10 - reflux ratio controller, 11 - reboiler, 12 - bottom receiving tank, 13 - dilute acetic acid tank, 14 - vacuum pump. DETAILED DESCRIPTION

[0029] The method for recycling waste acid in the electronics industry of the present invention comprises the following specific implementation steps:

[0030] Waste acid from the electronics factory is filtered out by the filter to remove mechanical impurities, avoiding the introduction of scale into the system or causing mechanical blockage or equipment wear.

[0031] The waste acid with mechanical impurities filtered out enters the middle of the distillation tower after preheating, and exchanges vapor and liquid with the vapor mixture of acetic acid, water, nitrogen oxide, etc. from the lower section of the tower in the packing layer. Phosphoric acid and most of the unvaporized nitric acid and metal ion impurities pass through the lower packing bed into the tower kettle. Nitrogen oxide, water, and acetic acid are further adsorbed and exchanged with vapor and liquid in the upper section. The acetic acid and water liquid refluxed from the top of the tower are further eluted, so that the rising acetic acid and water are purified and separated. The acetic acid and water vapor out of the top of the tower are condensed by the condenser to obtain acetic acid solution. Part of the acetic acid solution is returned as reflux eluent, and the rest is extracted as a product. A heater or reboiler is set at the bottom of the tower as a heat source and measure.

[0032] The liquid at the bottom of the tower mainly contains metal elements such as phosphoric acid, nitric acid, aluminum ions, and molybdenum ions.

[0033] The liquid at the bottom of the tower is cooled to room temperature by a cooler and sent to a storage tank for further processing and utilization.

[0034] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0035] Any feature disclosed in this specification (including claims and abstract), unless otherwise stated, may be replaced by other equivalent or alternative features having similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0036] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0037] Embodiment 1:

[0038] A method for separating acetic acid from electronic waste acid liquid, flow chart Figure 1 As shown:

[0039] A small amount of waste liquid from an electronics factory was taken under laboratory conditions, and distilled with water according to the method described in CN 115304514 A to obtain about 800 ml of a mixed acid solution of nitric acid and acetic acid, the composition of which was (by volume ratio): 16.8% acetic acid, 8.4% nitric acid, and 74.8% water.

[0040] The mixed acid solution obtained by the above treatment was added to a 1000 ml flask 5 and filled with 24 Φ , a 600mm long distillation column 3, the distillation column 3 is filled with about 300ml of Φ4mmX4mm hollow polymer filler 4 loaded with 5A molecular sieve, and then the reflux pipe regulator 2, reflux condenser 1, extraction pipe, receiving bottle 7 are installed in sequence, and the receiving bottle 7 is connected to the vacuum pump 8.

[0041] The flask 5 is heated by an electric heating jacket 6 with adjustable power to provide a heat source; the reflux ratio is controlled to be 1:1, the distillation temperature at the top of the distillation column does not exceed 51°C, the temperature of the flask 5 does not exceed 72°C, and the vacuum degree is controlled to be -0.09Mpa; the acetic acid concentration of the distillate at the top of the distillation column is obtained to be 19.2wt%, and the residue in the cooling flask 5 is obtained.

[0042] After testing, the nitric acid content was 67.5wt% and the acetic acid content was 480ppm, indicating that the acetic acid was well separated after distillation.

[0043] Embodiment 2:

[0044] The method steps in this embodiment are the same as those in Embodiment 1, except that:

[0045] 1. The composition of the waste acid to be separated is (wt%): 52% phosphoric acid (calculated as phosphate radical in metal salt), 5.5% nitric acid, 10.3% acetic acid, 0.22% aluminum, 0.31% molybdenum, 0.25% copper, and 31.42% water.

[0046] 2. Replace the material in the distillation column 3 with corrugated perforated plate structured packing.

[0047] The corrugated plate structured packing is made of 18% by weight of 5A molecular sieve, 5% of cyano resin, 24% of glass fiber, and the remainder is pp, and the total weight percentage is 100%, and the corrugated plate structured packing with a wall thickness of 2mm is obtained by blending and processing.

[0048] After detection, after distillation separation, 34.3 wt% of acetic acid was obtained, indicating that the separation of acetic acid from the waste acid mixture of nitric acid and phosphoric acid was achieved.

[0049] Example 3

[0050] A method for separating acetic acid from waste electronic acid liquid, the specific flow chart is as follows Figure 2 As shown:

[0051] The components of the waste acid recovered from the electronics factory from the waste acid storage tank 1 are: 51.2% phosphoric acid (calculated as phosphate radical in metal salts), 5.0% nitric acid, 9.8% acetic acid, 0.24% aluminum, 0.36% molybdenum, 0.03% iron, and 33.37% water.

[0052] The waste acid is sent to the filter 2 to filter out mechanical impurities, and enters the preheater 4 of the upper distillation of the distillation tower 5 through the feed pump 3 to be preheated to 82°C. After preheating, it enters from the lower part of the tower. The tower diameter is 200mm and the tower height is 3000mm. The upper section of the distillation tower 5 is filled with the molecular sieve plate corrugated packing 6 loaded on the upper section of the distillation tower, and the lower section of the distillation tower 5 is filled with the molecular sieve plate corrugated packing 7 loaded on the distillation tower. The bottom of the distillation tower 5 is provided with a distillation tower kettle 8, and the distillation tower kettle 8 is connected with the reboiler 11. The top of the distillation tower 5 is provided with a reflux tower top condenser 9 and a reflux ratio controller 10, and the reflux ratio is controlled at 2:1; the top temperature of the distillation tower 5 is controlled not to exceed 68°C, and the vacuum is controlled at -0.08MPa; continuous feeding and extraction are carried out to obtain a top acetic acid concentration of 31.6%.

[0053] The formula and preparation method of the molecular sieve plate corrugated packing 6 loaded on the upper section of the distillation tower and the molecular sieve plate corrugated packing 7 loaded on the lower section of the distillation tower are as follows:

[0054] Formula: Based on 100% by mass, it contains 18% 5A molecular sieve, 5% cyano resin, 24% glass fiber, and the balance is PP.

[0055] Preparation method: Weigh each substance in proportion, then blend them into modified PP material, and then process them into 2mm thick corrugated hole plate regular packing to obtain loaded molecular sieve plate corrugated packing. The blending preparation method is conventional technology and will not be repeated.

[0056] The concentrated acid aqueous solution extracted from the bottom of the distillation tower 5 is phosphoric acid (calculated based on the phosphate radical in the metal salt).

[0057] 76.4%, nitric acid 7.5%, acetic acid 1250ppm, aluminum 0.36%, molybdenum 0.54%, iron 0.04%.

[0058] experiment:

[0059] Based on the process of the method for separating acetic acid from waste electronic acid liquid described in Example 2, the effects of different proportions of 5A molecular sieve, cyano resin, PP and glass fiber on the separation effect were determined.

[0060] Specifically, 5A molecular sieve, cyanoresin, PP and glass fiber are first processed into material test pieces. The test pieces are laboratory Raschig rings with a diameter of 4mm, a length of 4mm and a wall thickness of 1mm, which are used in an adsorption distillation test system composed of a 1L flask in the laboratory; the electronic waste acid is separated, and the electronic waste acid used contains 52% phosphoric acid, 5.5% nitric acid, 10.3% acetic acid, 0.22% aluminum, 0.31% molybdenum, 0.25% copper, and 31.42% water, based on the phosphate radical in the metal salt. The specific proportion relationship and test results are shown in the following table:

[0061]

[0062] The above-mentioned embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

[0063] This background section is provided to generally present the context of the invention, and the work of the presently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither explicitly nor implicitly admitted to be prior art to the present invention.

Claims

1. A method for separating acetic acid from electronic waste acid liquid, characterized in that The method comprises the following steps: filtering the electronic waste acid liquid to remove mechanical impurities, and then separating acetic acid by an adsorption distillation method to obtain a dilute acetic acid product; the acetic acid content in the remaining acid liquid is less than 5000 PPM.

2. The method for separating acetic acid from electronic waste acid liquid according to claim 1, characterized in that: In the adsorption distillation method, molecular sieve is used as adsorbent.

3. The method for separating acetic acid from electronic waste acid liquid as claimed in claim 2, characterized in that: The molecular sieve is 5A molecular sieve.

4. The method for separating acetic acid from electronic waste acid liquid as claimed in claim 3, characterized in that: In the adsorption distillation method, a composite heat-resistant polymer plastic loaded with 5A molecular sieve adsorbent is used as the adsorption distillation material.

5. The method for separating acetic acid from electronic waste acid liquid as claimed in claim 4, characterized in that: The adsorption and distillation material is in the form of Raschig rings or plate corrugations.

6. The method for separating acetic acid from electronic waste acid liquid as claimed in claim 4, characterized in that: The adsorption and distillation material is a molecular sieve modified adsorption and distillation material, which is prepared by blending and modifying 5A molecular sieve, PP, solid cyano resin powder material modifier and glass fiber; based on 100 mass percentage, the amount of 5A molecular sieve added is 10-20%, the solid cyano resin powder material modifier is 5-10%, the glass fiber is 15-30%, and the balance is PP.

7. The method for separating acetic acid from electronic waste acid liquid as claimed in claim 6, characterized in that: Based on the mass percentage of 100, the amount of 5A molecular sieve added is 11%, the solid cyano resin powder material modifier is 8%, the glass fiber is 15%, and the balance is PP.

8. The method for separating acetic acid from electronic waste acid liquid as claimed in claim 6, characterized in that: The adsorption and distillation material is a 1-2 mm thin-wall material or a thin plate material.

9. A method for separating acetic acid from electronic waste acid liquid as described in any one of claims 1 to 8, characterized in that The specific steps include: The electronic waste acid liquid is filtered to remove mechanical impurities; then the electronic waste acid is preheated and then the adsorption distillation method steps are started, first entering the middle part of the distillation tower, and exchanging vapor and liquid with the acetic acid, water, and nitrogen oxide vapor mixture from the lower section of the distillation tower in the packing layer; phosphoric acid and most of the unvaporized nitric acid and metal ion impurities pass through the lower section packing bed into the tower kettle, and nitrogen oxide, water, and acetic acid are further adsorbed and exchanged vapor and liquid in the upper section, and the acetic acid and water liquid refluxed from the top of the tower are further eluted, so that the rising acetic acid and water are purified and separated, and the acetic acid and water vapor out of the top of the tower are condensed by a condenser to obtain an acetic acid solution, part of the acetic acid solution is returned for use as a reflux elution liquid, and the rest is extracted as a product.

10. The method for separating acetic acid from waste electronic acid liquid according to claim 9, characterized in that: A heater or a reboiler is installed at the bottom of the distillation tower as a heat source supply measure.

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