JP2001054988A - Method for treating waste nitric acid liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an efficient method for treating waste nitric acid liquid for recovering high purity nitric acid from waste nitric acid liquid containing aluminum generated in a lithographic printing production process for recycling with energy consumption reduced. SOLUTION: A reaction process in which waste nitric acid liquid containing aluminum which is generated in a lithographic printing production process is added with sulfuric acid in an amount 1.0-1.5 times in mole ratio as large as the amount of aluminum in the waste liquid to produce aluminum sulfate and a distillation process in which nitric acid separated in the reaction process is separated/recovered by distillation are provided. Preferably, the distillation process has an aluminum sulfate recovery process in which liquid containing aluminum sulfate is transferred from the bottom part of a distillation still to a crystallization tank, in which aluminum sulfate is deposited and separated/ recovered from the nitric acid solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a nitric acid waste solution containing aluminum, and more particularly, to a method for etching and roughening a continuously running aluminum plate in a lithographic printing plate manufacturing process. The present invention relates to waste liquid treatment of a process using nitric acid as a main component used for chemical treatment.

[0002]

2. Description of the Related Art Usually, nitric acid is used to etch the surface of aluminum in a lithographic printing plate manufacturing process. In the waste liquid generated in this step, nitric acid and dissolved aluminum exist as aluminum nitrate. Since such waste liquid contains metal and nitric nitrogen, it is generally neutralized with caustic soda, and the sodium nitrate solution generated by the treatment is reduced to nitrogen gas by biological treatment and discharged. is there. The biological treatment includes, for example, a biological treatment in which a hydrocarbon having a relatively small number of carbon atoms, such as methanol, is added to a nitric acid waste liquid as a hydrogen donor, and the nitrogen is reduced to nitrogen gas via ammoniacal nitrogen by denitrifying bacteria. This method is effective when the concentration of nitrate nitrogen is several hundred ppm or less, and when the concentration of the waste liquid is about 0.5 to 5%, a large amount of dilution water is required. Further, such a biological treatment requires a reaction time of several hours, and has a disadvantage that the scale of the apparatus is large and a large installation area is required. There is also a problem that a large amount of cost is required to supply the dilution water and the hydrogen donor.

[0003] In recent years, the amount of nitric acid waste liquid is expected to increase with the increase in the amount of treatment, and there is a demand for an economical method for treating nitric acid which is an alternative to biological treatment. In addition, since nitric acid is expensive, it is more desirable to collect and reuse nitric acid waste liquid from the viewpoint of resource saving than simply treating the nitric acid waste liquid. As a method for recovering nitric acid, aluminum nitrate solution can be separated and recovered into nitric acid and aluminum hydroxide by bipolar membrane electrodialysis, or sodium nitrate solution can be separated into nitric acid and caustic soda by diaphragm electrolysis. Although such techniques are known, power and separation membranes are costly, and have not been effective solutions to the problems.

Japanese Patent Application Laid-Open No. 6-1603 discloses a method applicable to the treatment of a waste liquid containing nitric acid in a manufacturing process of an electrolytic capacitor. Although the above-mentioned method of adding excess sulfuric acid is disclosed, there has been a problem that the excess sulfuric acid is difficult to separate from nitric acid in a liquid phase, and a mixed acid is formed to complicate the treatment. The treatment of nitric acid waste liquid containing aluminum has the above-mentioned problems. In particular, the waste liquid generated in the manufacturing process of a lithographic printing plate generally having a nitric acid concentration of about 0.5 to 5% requires a large installation area. There has been a long-felt need for an economically advantageous method of regenerating without the need.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to solve these problems and to recover and reuse high-purity nitric acid from nitric acid waste liquid containing aluminum generated in a lithographic printing plate manufacturing process. Another object of the present invention is to provide a highly efficient processing method that consumes less energy.

[0006]

In general, as one of the methods for producing nitric acid, a method is known in which nitrite is decomposed with sulfuric acid and then separated by distillation to distill out nitric acid. The method according to the present invention, based on this finding, has eagerly studied to recover nitric acid from a nitric acid waste liquid containing aluminum, and has constructed a treatment system capable of effectively utilizing an aluminum compound. That is, the method for treating a nitric acid waste liquid of the present invention is characterized in that the nitric acid waste liquid containing aluminum generated in the lithographic printing plate production process has a molar ratio of 1.0 to the contained aluminum.
It is characterized by comprising a reaction step of adding 1.5-fold amount of sulfuric acid to produce aluminum sulfate, and a distillation step of separating and recovering nitric acid liberated in the reaction step by distillation.

In this distillation step, a liquid containing concentrated aluminum sulfate is appropriately transferred to the crystallization tank from the bottom of the distillation still used, aluminum sulfate is precipitated in the crystallization tank, and the aluminum sulfate is separated from the nitric acid solution. It is preferable to have an aluminum sulfate recovery step of recovering from the viewpoints of processing efficiency and effective use of aluminum components. In the case of providing such an aluminum sulfate recovery step, it is preferable to provide a circulation system for returning the nitric acid solution after separating and recovering the aluminum sulfate to the distillation can from the viewpoint of improving the recovery rate of nitric acid, and further, In addition to the separated nitric acid solution, in the aluminum sulfate recovery step, water containing nitric acid separated in the dehydrating step of the precipitated aluminum sulfate crystals, waste water of washing water used for washing the crystals, and the like can be distilled together with the nitric acid solution. By returning to, the recovery efficiency of nitric acid can be improved.

In carrying out the treatment method of the present invention, the flow rate of the nitric acid waste liquid and the concentration of aluminum ions contained in the waste liquid are automatically sampled and measured at predetermined intervals, and the amount of sulfuric acid to be added is measured. By providing a control step, a stoichiometrically appropriate reaction process can always be performed, which is a preferable embodiment in terms of recovery efficiency and reduction of wasteful costs. The processing method of the present invention comprises:
It is preferably applied to a nitric acid waste liquid having a free nitric acid content of 0.5 to 5% and a waste liquid generated in a lithographic printing plate manufacturing process having an aluminum nitrate content of about 0.5 to 8%. And excellent effects can be obtained.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The method for treating nitric acid waste liquid of the present invention includes aluminum,
In general, a reaction step of adding 1.0 to 1.5 times the molar amount of sulfuric acid with respect to the contained aluminum to a nitric acid waste liquid having a concentration of 0.5 to 5% to produce aluminum sulfate,
Thereafter, it is characterized by including at least two distillation steps of separating and recovering nitric acid by distillation.
In the reaction step, the molar ratio of sulfuric acid / aluminum is adjusted to 1.0 to 1.0 depending on the aluminum ion content measured in advance.
1.5, preferably 1.4-1.5 sulfuric acid is added and allowed to act to form a mixed solution containing aluminum sulfate and free nitric acid from aluminum nitrate in the solution; , The nitric acid is concentrated and recovered by distillation.

[0010] The amount of sulfuric acid acted on in the reaction step is
When the molar ratio of aluminum becomes 1.5, the input sulfuric acid is all converted to aluminum sulfate and discharged out of the system. When sulfuric acid is added at a molar ratio to aluminum exceeding 1.5, the excess sulfuric acid remains in the liquid phase system, and as the concentration increases, it is mixed into the distilling nitric acid solution in the distillation step. Purity is reduced, which is inconvenient. On the other hand, when the added amount of sulfuric acid is in the range of 1.0 or more and less than 1.5 in molar ratio, some aluminum nitrate remains in the system, but when the concentration increases, the crystallization step described later will soon. Since it is coprecipitated with aluminum sulfate and discharged outside the system, it does not affect the quality of the recovered nitric acid. However,
When the molar ratio of the addition of sulfuric acid is less than 1.0, there is no problem with the quality of nitric acid, but aluminum nitrate is mixed with aluminum sulfate as an impurity, and the quality of aluminum sulfate may deteriorate, which is not preferable. From the above viewpoints, the addition amount of sulfuric acid needs to be 1.0 to 1.5 times in molar ratio with respect to the contained aluminum, and is in a range as close as possible to 1.5, particularly in a molar ratio of 1. It is preferably from 4 to 1.5.

In the distillation step, free nitric acid is removed during the distillation, and the aluminum sulfate solution to be concentrated is transferred to a crystallization tank installed in an external circulation system by, for example, extracting the liquid from the bottom of the distillation can. Therefore, solids can be continuously taken out by precipitating them as aluminum sulfate crystals and performing solid-liquid separation. By appropriately removing the concentrated aluminum sulfate solution as described above, precipitation of aluminum sulfate in the distillation can can be prevented. After the aluminum sulfate is taken out of the crystallization tank, it can be used as a flocculant after washing with water, dehydration and drying.

Further, the nitric acid solution from which the aluminum sulfate has been separated is recovered again as nitric acid by supplying it again to the distillation can, so that the recovery efficiency of nitric acid can be improved. At this time, in order to suppress energy consumption, it is effective to concentrate the free nitric acid concentration to about 15% by evaporating the waste liquid containing free nitric acid and aluminum nitrate using a multi-effect tube before adding sulfuric acid. is there. Nitric acid is an azeotrope having the highest boiling point with water. However, at a concentration of 15% or less, nitric acid hardly evaporates and water is overwhelmingly evaporated, so that the concentration can be increased substantially without distilling out nitric acid.

According to the present invention, nitric acid and aluminum sulfate as a by-product can be recovered and reused, and the waste liquid can be treated without alkali neutralization.
The cost of alkaline raw materials such as caustic soda is not required, and it is preferable in terms of cost.

An embodiment of the present invention will be described with reference to the flow chart of FIG.
It will be described sequentially. A waste liquid containing 0.5 to 5% of free nitric acid and 0.5 to 8% of aluminum nitrate discharged from the lithographic printing plate manufacturing process is first supplied to a first evaporator 10 and concentrated in a first stage by steam. , And the obtained concentrated liquid is further successively concentrated by the second evaporator 11. As these evaporators, it is preferable to use a double effect can for energy saving. According to such an embodiment, the evaporators 10 and 11 are depressurized by a vacuum pump (not shown). . The concentration of free nitric acid in the distillate vapor is determined by the concentration of free nitric acid in the evaporators 10 and 11, but from the vapor-liquid equilibrium of the nitric acid / water / aluminum nitrate system, when the free nitric acid concentration is 15% or less, substantially only water is used. Distills. For this reason, in consideration of the efficiency in the future process, it is preferable to concentrate the second evaporator 11 until the free nitric acid concentration becomes about 15%. Since the steam generated here hardly contains nitric acid, there is no need to collect the drain. On the other hand, when the degree of concentration is advanced, aluminum nitrate may be deposited. Since the precipitation of aluminum nitrate lowers the efficiency of the subsequent reaction step, the concentration of aluminum nitrate is set to 30% by concentration of aluminum nitrate so that aluminum nitrate is not deposited. It is necessary to adjust to less than degree.

The waste liquid containing concentrated nitric acid and aluminum nitrate is
It is transferred to a reaction tank 14 by a pump (not shown) via a transfer pipe provided with an aluminum ion concentration detector 12 and a flow meter 13. Here, the amount of aluminum ions contained in the waste liquid is detected from the concentration of aluminum ions in the waste liquid and the flow rate of the waste liquid, and the sulfuric acid is adjusted so that the molar ratio of sulfuric acid / aluminum is in the range of 1.0 to 1.5. The supply amount is measured by a flow meter 15 and charged into the reaction tank 14, where the waste liquid and the sulfuric acid are stirred and mixed. As a result, aluminum ions existing as aluminum nitrate react with sulfuric acid in a molar ratio of about 1.5 times as much as sulfuric acid to become aluminum sulfate, and nitric acid can be easily dissociated. As the aluminum ion concentration detector 12 used for detecting the aluminum ion concentration, a titrator having an automatic sampling function is preferable. Further, as the flow meter 13, a general known mass flow meter, an integrating flow meter, or the like can be used. (Reaction step)

Next, the waste liquid reacted in the reaction tank 14 is conveyed to a distillation can 16 by a liquid feed pump (not shown).
The mixture is heated to the boiling point in the distillation can 16, and water / nitric acid vapor coming out of the tower is condensed with water in a condensing can 17, and a high-purity nitric acid aqueous solution is collected in a reserve tank 18 and reused. (Distillation step) On the liquid side in the distillation can 16, the concentration of aluminum sulfate naturally increases, and the concentration of nitric acid also occurs at the same time. In general, it is desirable to perform the distillation operation under reduced pressure to reduce the boiling point from the viewpoint of preventing corrosion of the apparatus.

From the viewpoint of preventing the precipitation of aluminum sulfate in the distillation can 16 and improving the recovery efficiency of nitric acid, the solution is appropriately drawn from the bottom of the distillation can 16 to feed a liquid (not shown).
To the crystallization tank 19 where aluminum sulfate can be precipitated and separated. Here, the nitric acid solution separated from the solid aluminum sulfate is returned to the distillation can 16 via the second reserve tank 20 and circulated. At this time, in order to make aluminum sulfate precipitation proceed efficiently in the crystallization tank 19, the crystallization tank 1
The temperature in 9 is preferably set to be 5 to 10 ° C. lower than the temperature of distillation still 16. The cooling can be easily performed by a method of cooling the water by using the crystallization tank 19 as a jacket type or a method of installing a heat exchanger in the tank. The precipitated aluminum sulfate is retained at the bottom of the crystallization tank 19 using gravity sedimentation or the like. According to this method, the aluminum sulfate is separated from the liquid, and the aluminum sulfate is not precipitated in the distillation can 16,
Since the concentration of nitric acid can be increased, it is possible to recover nitric acid at a high recovery rate.

Next, an operation of taking out aluminum sulfate deposited on the bottom of the crystallization tank 19 out of the system will be described. Crystallization tank 19
The precipitated powder of aluminum sulfate retained at the bottom of the tank is transferred to the dehydrator 21 together with the liquid by a pump (not shown). Since the liquid phase is a solution containing nitric acid, it is transferred to the second reserve tank 20 by the pump. Then, it is returned to the distillation can 16 and circulated together with the precipitated aluminum sulfate and the separated nitric acid solution described above. As the dehydrator 21, a known belt press, screw press, or the like can be used. The resulting precipitated aluminum sulfate is washed with water after a dehydration treatment and a washing step 22,
After the nitric acid content is removed, it is dried by a dryer 23 and then accumulated in a hopper 24 to be used as aluminum sulfate powder.

In the flow illustrated in FIG. 1, the dewatering step and the water washing step are separate steps, but the water is sprayed on the aluminum sulfate powder by spraying or the like during or at the end of the dewatering operation by the dehydrator. In addition, the dehydration step and the washing step can be performed simultaneously, and more efficient processing can be performed. At this time, the waste liquid used for washing the aluminum sulfate powder also contains a predetermined amount of nitric acid.
0, mixed with the separated nitric acid solution and the waste liquid in the dehydration step in the reserve tank 20, and sent to the distillation can 16 again by a pump (not shown), thereby recovering an effective nitric acid component. it can.

As described above, the present invention proposes a system capable of recovering nitric acid with high efficiency from a nitric acid waste liquid containing free nitric acid and aluminum nitrate, and recovering aluminum as aluminum sulfate.

[0021]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto. (Example 1) First, details of the waste liquid in the manufacturing process of a lithographic printing plate (hereinafter, referred to as PS plate) to which the waste liquid treatment method of the present invention is suitably applied will be described with reference to the planographic printing plate manufacturing process. explain.

The PS plate is a printing plate characterized in that an image is formed by providing a hydrophilic region and an ink affinity region on an aluminum support. Therefore, the properties of the aluminum surface used as the support are required to have water retention, adhesion to the photosensitive layer (recording layer), abrasion resistance during printing, and hydrophilicity. In general, the surface of the support is processed into a fine uneven shape in order to secure water retention and usually adhesion to a photosensitive layer based on a resin layer. Usually, as these uneven shapes, a multilayer uneven shape in which waves having different wavelengths are superposed is formed. From the viewpoint of imparting abrasion resistance, a treatment for hardening the surface is required, and usually an alumite treatment is performed. Hydrophilicity is achieved by the action of an aqueous solution of an alkali metal salt of silicic acid at the final stage of the treatment.

First, the surface treatment of PS plate aluminum will be described. Surface treatment process (1) to be described below
(8) shows only the basic processing steps. In practice, a water-washing step using a spray or the like to wash out the liquid taken out from the previous step is performed between these steps.
A description of these intermediate processing steps is omitted.
First, an untreated aluminum plate is subjected to a mechanical surface roughening step (1). Here, a slurry solution of abrasive powder such as pumice, silica sand, and alumina was supplied to the surface of the aluminum plate by spraying, and the surface was roughened by rubbing the surface with a nylon brush. By this mechanical surface roughening treatment, 1
An uneven structure having a wavelength of 0 to 20 microns is formed.

The etching step (2) is subsequently carried out for the purpose of smoothing the surface of the uneven structure obtained in the surface roughening treatment (1), preventing the ink from being caught at the time of printing, and making it harder to stain. Here, the surface was subjected to an etching treatment of 1 to ²⁰ g / m ² by spraying a NaOH solution. Next, aluminum hydroxide called smut generated during etching in the pickling step (3) and adhered to the surface was removed by pickling with nitric acid.

Next, in the electrolytic surface roughening step (4), the surface was electrolytically roughened in order to form a smaller uneven structure and a wavelength of 1 to 10 μm. As a power source, a rectangular wave alternating current having a frequency of 60 Hz was used, and nitric acid was used as an electrolytic solution. Subsequently, an etching step (5) is performed to make the surface 0.1 to 3
g / m ^{2 was} slightly etched to remove the smut generated in the electrolytic surface roughening step (4), and at the same time to control the unevenness of the surface. The etching solution used was a NaOH solution. Next, in the pickling step (6), the etching step (5)
The smut generated in the above was pickled with nitric acid and removed. Through the above steps (1) to (6), irregularities were formed on the aluminum surface with high precision.

Next, in order to provide abrasion resistance, in the alumite step (7), an alumite treatment for forming an oxide film on the uneven surface was performed. DC power was used as the power source, and sulfuric acid was used as the electrolyte. The oxide film amount was 1 to 4 g / m ² . Finally, a hydrophilicity step (8) is performed to impart water retention and hydrophilicity. Here, an aluminum plate having irregularities previously formed was dipped in an aqueous solution of sodium silicate to form a silicate layer of 1 to ²⁰ mg / m ² on the alumite surface to impart hydrophilicity.

After the above-mentioned surface treatment step is completed, a support for a PS plate is obtained. The obtained support is formed by applying a photosensitive layer according to the purpose on the support, drying it, and then cutting it to a fixed size to prepare a PS plate.

Among the surface treatment steps described above, the nitric acid waste liquid containing aluminum, which is generated in the electrolytic surface roughening step (4) to the pickling step (6), was treated by the method of the present invention. PS
10 kg of waste solution (free nitric acid concentration 1%, aluminum ion concentration 0.5%, aluminum nitrate conversion 3.94%) in the nitric acid etching step of the aluminum plate for plate is used for an experiment equivalent to the flow chart shown in FIG. It was charged into the first evaporator 10 in the recovery system. First evaporator 1 which is a double effect evaporator 1
0, 8.5 kg of water is evaporated through the second evaporator 11, and a solution 1 having a free nitric acid concentration of 6.6%, an aluminum ion concentration of 3.3% and an aluminum nitrate conversion of 26.2% at the outlet side of the evaporator 11. 0.5 kg was obtained.

This solution was transferred to the reaction layer 14, and 98% concentrated sulfuric acid corresponding to a sulfuric acid / aluminum molar ratio of 1.5 was added to 0.278.
After adding 10 kg and stirring for 10 minutes, simple distillation was performed in a distillation can 16 under reduced pressure. During this time, 1.31 kg was withdrawn as bottom liquid from the lower part of the evaporator 16, and the temperature was reduced to about 10 ° C. in the crystallization tank 19.
Upon cooling, aluminum sulfate was precipitated. After filtering this precipitate,
It is subjected to a water washing step 22, washed with 1 kg of water, and dried in a drier 24.
To obtain an aluminum sulfate powder, which was stored in the hopper 24. In the first embodiment, in the recovery of aluminum sulfate, the dehydrator 21 shown in the flow of FIG.
Solid-liquid separation was performed by filtration. The supernatant of the crystallization tank 19, the filtrate of the precipitate, and the washing waste liquid in the water washing step 22 were collected in a reserve tank 20, mixed, transferred as a feed to the distillation can 16 of the simple distillation apparatus, and subjected to simple distillation. The simple distillate was cooled with water, condensed, and received in the reserve tank 18. The input steam was controlled so that the level of the distillation still liquid at the time of simple distillation was constant. The above operation was repeated until the inside of the experimental apparatus became a steady state.

In a steady state, the nitric acid waste liquid 10
0.31 kg of aluminum sulfate powder and a flocculant (nitric acid concentration: 18%, 2.5 kg) were collected per kg. Nitric acid 0.
45 kg (100% conversion) was obtained. High-purity nitric acid was obtained in the recovered nitric acid without any contamination caused by the sulfuric acid used in the treatment step.

Example 2 10 kg of waste liquid (free nitric acid concentration: 5%, aluminum ion concentration: 1%, aluminum nitrate conversion: 7.9%) in a nitric acid etching step of an aluminum plate for PS plate was
In the same manner as in Example 1, it was put into the experimental recovery system equivalent to the flow shown in FIG. 6.5 kg of water is evaporated by the double effect evaporators 10 and 11, and at the outlet side of the evaporator 16, the free nitric acid concentration is 14.2%, the aluminum ion concentration is 2.8%,
3.5 kg of a 22.5% solution of aluminum nitrate was obtained.

Next, 0.556 kg of 98% concentrated sulfuric acid corresponding to a sulfuric acid / aluminum molar ratio of 1.5 was added in the reaction layer 14 and stirred for 10 minutes, followed by simple distillation under reduced pressure in the distillation still 16. During this time, 1.62 kg was withdrawn as a bottom liquid, and the temperature was cooled to about 10 ° C. in the crystallization tank 19 to precipitate aluminum sulfate. After the precipitate was filtered, the precipitate was washed with 1 kg of water and dried to obtain aluminum sulfate powder.

The supernatant of the crystallization tank 19, the filtrate of the precipitate, and the washing waste liquid are collected in a reserve tank 20 and mixed.
It was transferred as a feed into the distillation can 16 of the simple distillation apparatus and subjected to simple distillation. The simple distillate was cooled with water, condensed, and received in the reserve tank 18. The input steam was controlled so that the level of the distillation still liquid at the time of simple distillation was constant. The above operation was repeated until the inside of the experimental apparatus became a steady state. In a steady state, 0.62 kg of aluminum sulfate powder and coagulation liquid (nitrate concentration 2
7%, 4.4 kg). 1.19 kg of nitric acid (1
(Equivalent to 00%).

As is clear from the first and second embodiments,
ADVANTAGE OF THE INVENTION According to this invention, nitric acid is collect | recovered from the nitric acid waste liquid containing aluminum, such as the waste liquid discharged in the manufacturing process of a PS plate, and the aluminum component can also be collect | recovered as aluminum sulfate as needed. For this reason, expensive nitric acid is reused, and aluminum sulfate can be used as a coagulant, and the treatment method of the present invention does not require an alkali for neutralization. These economic effects are significant. Moreover, efficient treatment is possible without requiring a large installation area as in biological treatment.

[0035]

According to the method for treating nitric acid waste liquid of the present invention,
The present invention has an excellent effect of recovering and reusing high-purity nitric acid with low energy consumption, high efficiency and high efficiency from a nitric acid waste liquid containing aluminum generated in a lithographic printing plate manufacturing process.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of a method for treating a nitric acid waste liquid of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 1st distillation can 11 2nd distillation can 12 Aluminum ion concentration detector 13 Flow meter (For measuring nitric acid waste liquid amount) 14 Reaction tank 15 Flow meter (For controlling sulfuric acid supply amount) 16 Distillation can 17 Condensing can 18 Reserve tank (For recovering nitric acid) 19 Crystallization tank 20 Reserve tank (For recovering nitric acid-containing solution) 21 Dehydrator 22 Washing process 23 Dryer 24 Hopper (for aluminum sulfate powder)

Claims (5)

[Claims] 1. A reaction for producing aluminum sulfate by adding 1.0 to 1.5 times the molar ratio of sulfuric acid to aluminum contained to a nitric acid waste liquid containing aluminum generated in a lithographic printing plate manufacturing process to produce aluminum sulfate. A method for treating nitric acid waste liquid, comprising: a step of separating and recovering nitric acid liberated in the reaction step by distillation. 2. In the distillation step, a liquid containing aluminum sulfate is transferred to a crystallization tank from the bottom of a distillation can used, aluminum sulfate is precipitated in the crystallization tank, and aluminum sulfate is separated and recovered from a nitric acid solution. The method for treating a nitric acid waste liquid according to claim 1, further comprising an aluminum sulfate recovery step. 3. The method for treating nitric acid waste liquid according to claim 2, further comprising a circulation system for returning the nitric acid solution from which aluminum sulfate has been recovered to the distillation can in the aluminum sulfate recovery step. 4. In the aluminum sulfate recovery step, dehydration of aluminum sulfate, dehydration occurring during washing with water,
4. The method for treating a nitric acid waste liquid according to claim 3, further comprising a circulation system for returning the waste liquid of the washing water to the distillation can along with the nitric acid solution after the recovery of the aluminum sulfate. 5. The method according to claim 1, further comprising a step of automatically sampling and measuring the flow rate of the nitric acid waste liquid and the concentration of aluminum ions contained in the waste liquid at predetermined intervals to control the amount of sulfuric acid to be added. The method for treating a nitric acid waste liquid according to claim 1.