JP2973384B2 - Purification method of aluminum hydroxide and surface treatment method of aluminum material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates is related <br/> method of purifying hydroxide aluminum. The present invention utilizes the purification method, the to crystallize aluminum hydroxide from sodium aluminate solution supersaturated, hydroxide aluminum
The solution mainly containing sodium hydroxide from which
The present invention relates to a method for surface treatment of an aluminum material by using a sodium aluminate solution that returns to a physical solution and maintains an aluminum ion concentration at a predetermined concentration.

[0002]

2. Description of the Related Art The surface of an aluminum plate, which is a support of a lithographic printing plate, is etched using caustic soda before and after roughening mechanically or electrochemically. In addition, for example, nitric acid and hydrochloric acid are used in the step of electrochemically roughening, and sulfuric acid is used in the anodizing step, and various treatment liquids are used for the surface treatment of the support. The surface shape of the treated support after treatment varies greatly depending on the aluminum ion concentration in the treatment solution used for such surface treatment, and the aluminum ion concentration in the solution greatly affects the quality of the support. Further, since an aluminum alloy plate other than an aluminum plate is used for the lithographic printing plate support, the treatment liquid used for the surface treatment may contain many impurities other than aluminum.

As described above, the aluminum ion concentration in the processing solution has a great effect on the quality of the aluminum support for a printing plate. Therefore, it is important to keep the aluminum ion concentration in the processing solution constant at a predetermined concentration. . Conventionally, in order to keep the aluminum concentration constant, the treatment liquid in the treatment system is discharged outside the system to keep the aluminum ion concentration constant,
As described in JP-A-57-192300, a method of using an ion-exchange resin to adsorb aluminum ions in a treatment liquid to the ion-exchange resin and keeping the aluminum ion concentration constant has generally been used. However,
The method of adjusting the outside of the system to keep the aluminum ion concentration constant by discharging the processing solution in the processing system outside the system requires that the processing solution be discharged outside the system, and the amount of the processing solution used is extremely low. There is a problem that it becomes large, and the load of waste liquid treatment is also large.

The aluminum sash material is also etched with caustic soda in a process of performing a process such as matting the surface of the material or forming an anodic oxide film to improve durability. Due to the large volume of the solution, it is necessary to recover the aluminum hydroxide from the etching solution. As a result of various surface treatments such as surface strengthening treatment by anodic oxidation using sulfuric acid, it is necessary to recover aluminum hydroxide from sludge generated by neutralizing waste liquid and control aluminum ion concentration in surface treatment agent Recovery of aluminum ions and the like performed for the above purpose is a problem that is the same as the case of waste liquid treatment in the surface treatment step of the aluminum support for a printing plate.

As described above, in the production of alumina, the production of a lithographic printing plate, or the production of an aluminum sash, etc., in order to produce high-purity aluminum hydroxide from a sodium aluminate solution, hydroxide from aluminum sludge generated in the process is used. The process of recovering aluminum or purifying the crude sodium aluminate solution in the process to obtain high-purity aluminum hydroxide and using it to control the aluminum ion concentration in the surface treatment agent is an important issue. is there.

As described above, conventionally, in the process of producing alumina from bauxite, in the process of obtaining a purified sodium aluminate solution from a supersaturated sodium aluminate solution to produce aluminum hydroxide, impurities have been settled by a sedimentation method using a thickener. There is a method of sedimenting crystals from supersaturated sodium aluminate solution to remove impurities.However, because the impurity crystals are fine, a long time is required for sedimentation, and a large sedimentation area and thus large-scale equipment are required. is there. In addition, very fine crystals of impurities (almost liquid)
Therefore, it takes as long as 42 to 72 hours to crystallize aluminum hydroxide, and the purity of the purified sodium aluminate solution is poor, and the crystal deposition rate is not good.

Hitherto, as a method for removing impurities from a supersaturated sodium aluminate solution, a filtration method using a leaf filter, a filter press, or the like has been performed. However, the filtration method is not practical because clogging is likely to occur.

Further, in order to separate sodium ions and aluminum ions from the sodium aluminate solution, the present inventors have proposed the diffusion of aluminum ions out of the system by diffusion dialysis using an ion exchange membrane (Japanese Unexamined Patent Publication No. 20
099). However, in the case of diffusion dialysis, removal of insoluble metals such as iron adhering to the membrane and scale of aluminum hydroxide etc. adhere to the waste liquid side after diffusion dialysis. And the running cost increases.

[0009]

The problem to be solved by the present invention when producing a crystal of aluminum hydroxide and a purified sodium aluminate solution by a hydrolysis reaction from a supersaturated sodium aluminate solution is to solve the problem. An object of the present invention is to easily and inexpensively remove impurities in a solution to obtain a high-purity aluminum hydroxide crystal and a purified sodium aluminate solution. Furthermore, when the surface of a lithographic printing plate aluminum plate is subjected to an etching treatment using sodium hydroxide, or a surface treatment is carried out using various treatment solutions of acids and alkalis, the problem to be solved by the present invention is that In order to make the quality of etching and surface treatment good and uniform, maintain the aluminum ion concentration in the treatment system at a predetermined concentration and recycle a large amount of aluminum sludge discharged from the surface treatment process as industrially effective. It is to use.

[0010]

SUMMARY OF THE INVENTION The above problems using the purification method and purification method of hydroxide aluminum of the present invention
This is achieved by a surface treatment method for an aluminum material . Chi 's nest <br/>,

(A) In a method for purifying a sodium aluminate solution by crystallizing aluminum hydroxide from a supersaturated sodium aluminate solution by a hydrolysis reaction, impurities in the supersaturated sodium aluminate solution are removed by a centrifugal sedimentation machine. A method for purifying aluminum hydroxide, wherein a hydrolysis reaction is caused thereafter, and aluminum hydroxide is crystallized from a sodium aluminate solution.

[0012]

( B ) In the surface treatment method for an aluminum material, aluminum ions are separated out of a part of a treatment solution containing a sodium aluminate solution to be circulated and used for a surface etching treatment, and aluminum ions in the treatment solution are separated. In the surface treatment method for maintaining the concentration at a predetermined concentration, a part of the treatment solution containing the sodium aluminate solution to be circulated and the non-crystal generated during neutralization of waste acid and waste alkali discharged from the surface treatment step of the aluminum material The mixture is adjusted to a supersaturated sodium aluminate solution by mixing aluminum sludge mainly composed of neutral aluminum hydroxide, and impurities in the solution are removed by a centrifugal sedimentator. Water from which aluminum hydroxide is crystallized and aluminum hydroxide is crystallized and removed
Add sodium oxide-based solution to circulating treatment solution
A method for treating a surface of an aluminum material, comprising using a sodium aluminate solution obtained as described above as a treatment liquid .

( C ) As a centrifugal sedimentation machine used for removing impurities in the supersaturated sodium aluminate solution described in ( a ) above, impurities are removed by using a separation plate type centrifugal sedimentation machine. Thereafter, a hydrolysis reaction is caused, and aluminum hydroxide is crystallized from the sodium aluminate solution. A method for purifying aluminum hydroxide is a better method for purifying aluminum hydroxide. ( D ) When removing impurities in the supersaturated sodium aluminate solution described in ( b ) above, the impurities are removed using a centrifugal sedimentation separator, and then a hydrolysis reaction is caused to occur. Hydroxide from which aluminum hydroxide is crystallized and aluminum hydroxide is removed from solution
That it uses the sodium aluminate solution treatment liquid was added to give <br/> circulating solution of sodium reduction mainly as the processing liquid
Surface treatment method of an aluminum material, characterized in that a better surface treatment method.

Next, a reference method will be described. (E) Hydrolysis reaction from supersaturated sodium aluminate solution
Aluminate to crystallize aluminum hydroxide
In a method for purifying a soda solution, supersaturated sodium aluminate is used.
Calcium in the solution to less than 5 ppm
After hydrolysis reaction occurs, the sodium aluminate solution is
Hydroxide characterized by crystallizing aluminum oxide
A method for purifying aluminum. (F) In the method for treating the surface of an aluminum plate,
Including sodium aluminate solution that is circulated for etching
Aluminum ions from a part of the processing solution
And adjust the concentration of aluminum ions in the processing solution to a predetermined concentration.
In the surface treatment method to keep
Part of the processing solution containing the
Generated during neutralization of waste acid and waste alkali discharged from the process
Based on amorphous aluminum hydroxide
By mixing the sludge with supersaturated aluminum
Adjust to sodium citrate solution, calcium in the solution is 5pp
m and then hydrolyze to aluminum
Crystallization of aluminum hydroxide from sodium acid solution
Hydroxide with aluminum hydroxide crystallized and removed
Obtained by adding a solution mainly comprising
It is characterized by using acid soda solution as processing solution
Surface treatment method for aluminum support for printing plate. When removing the impurities in the supersaturated sodium aluminate solution according to ( e ) and ( f ) above, the method of removing calcium in the supersaturated sodium aluminate solution to less than 5 ppm is to remove the sodium aluminate solution. Maintain at 0 ° C. to 100 ° C. and add slaked lime [Ca (OH) ₂ ] and soda ash (NaCO ₃ ) or phosphate (Na ₂ HPO ₄ ) to the solution. By adding slaked lime [Ca (OH) ₂ ] or the like to the solution, calcium, magnesium, silicic acid, iron, manganese and the like in the solution are removed. Then, when the supersaturated sodium aluminate solution is sent to a crystallization tank to crystallize aluminum hydroxide, the crystallization reaction time becomes very short. Further, by performing this purification method, in the method for treating the aluminum support for a printing plate described in ( f ) above, sludge generated during neutralization of waste acid and waste alkali discharged from the surface treatment step can be efficiently removed. It can be recovered as aluminum hydroxide.

The centrifugal sedimentation devices described in the above ( a ) and ( b ) include the centrifugal sedimentation devices described in ( c ) and ( d ), as well as the decanter type and the cylindrical type. A settler can also be used. However,
The separation plate type has good separation efficiency, and is excellent in that even if the supply amount of the supersaturated sodium aluminate solution, which is the water to be treated, to the centrifugal settling machine is increased, even very fine impurity crystals can be separated and removed well. .

In the following, referring to FIG. 1 and FIG. 2, the reference method and the production of alumina from the bauxite of the present invention will be described.
The step of purifying the sodium aluminate solution described in the above ( e ) and ( c ) will be described. In the purification step described in ( e ) above, the sodium aluminate containing impurities is sent to the flash tank 42 and cooled, for example, into a solution such as phosphate or Slaked lime and soda ash are added in appropriate amounts. The cooled sodium aluminate solution to which phosphates and the like have been added is sent to the thickener 43, where it is in a suspended state. In the sodium aluminate solution in the suspended state, the hydroxide crystals of the impurities are precipitated as relatively large crystals, and settle quickly in the thickener 43. Thereafter, the treatment is carried out according to the general steps to obtain a high purity sodium aluminate solution and alumina.

FIG. 2 shows a step of purifying the sodium aluminate solution described in the above ( c ). FIG. 2 is the same except that a separator centrifugal sedimenter 44 is used instead of the thickener 43 in the general process of alumina production shown in FIG. That is, in the step of purifying the sodium aluminate solution described in ( c ), in FIG. The separated liquid component is sent to a crystallization reaction tank 45, where it is crystallized and treated according to the following general steps to obtain a sodium aluminate solution and alumina of high purity. On the other hand, the solid component separated into solid and liquid is discarded outside the system as red mud. In the step of purifying the sodium aluminate solution described in the above ( f ), ( c )
In the purification step of the sodium aluminate solution described in the above, the removal of impurities may be performed by any type of centrifuge, instead of using the separator centrifuge 44, for example, a decanter centrifuge. .

Next, the step of purifying the sodium aluminate solution of the present invention described in the above ( a ) in the surface treatment step of the aluminum support for a printing plate will be described with reference to FIG. In the etching process, the processing liquid is prepared in a liquid preparation tank 5, and the prepared processing liquid is sent to a spray 3 in an etching processing tank 11 through a liquid feed pipe 12 using a liquid feed pump 4. The etching treatment liquid from the liquid preparation tank can be further sent to the dissolution tank 34 through the liquid supply pipe 13 branched from the liquid supply pipe 12. The amount and timing of liquid supply can be adjusted by operating a valve (not shown) provided in the middle of the pipe.

The liquid adjusting tank 5 and the etching tank 11 are connected by a liquid supply pipe 12 and a return liquid pipe 14, and the etching liquid is circulated between them.
During the etching process, the sodium hydroxide component in the processing solution is reduced by the reaction, the aluminum ion content is increased, and the water is evaporated and the amount of the processing solution is changed. For this reason, the treatment liquid in the liquid preparation tank 5 is supplied with sodium hydroxide solution and water, respectively.
Starting from 1 and 22, it is wasteful to keep the aluminum ions in the processing solution at a predetermined concentration by the replenishing solution without removing the increasing aluminum ions.

For this reason, a part of the processing liquid being circulated in the liquid adjusting tank 5 is supplied to the dissolving tank 34 through the liquid supply pipe 13 in a timely manner to remove aluminum ions from the system. On the other hand, the aluminum sludge 16 converts pH of waste alkali 30 and waste acid 31, 32, 33 discharged from each surface treatment step to pH.
It is neutralized in the adjusting tank 27 and is coagulated and precipitated in the coagulating sedimentation tank 28. Further, solid-liquid separation is performed by a filter press 29, and the solid is separated and sent to a dissolution tank 34 as needed.

In the dissolving tank 34, the etching solution, the aluminum sludge 16 and water 19 as required are mixed, and phosphate or slaked lime and soda ash are added in appropriate amounts. Then, calcium and the like in the liquid are precipitated, and removed by the slide thickener 36 and the filter 35 as necessary. In the precipitation tank 7, aluminum hydroxide is crystallized using aluminum hydroxide seeds in a supersaturated sodium aluminate solution as nuclei.

For this reason, a mixture of a treatment liquid mainly containing sodium hydroxide solution having a reduced aluminum ion concentration and aluminum hydroxide crystals is sent to the thickener 8 through a liquid sending pipe 17 and crystallized aluminum hydroxide Are separated by a drum filter 9 through a pipe 18 and collected in a hopper 10. On the other hand, the processing liquid mainly including the sodium hydroxide solution passes through the recovery pipe 20 as a recovery liquid and is returned to the liquid preparation tank.

Next, the step of purifying the sodium aluminate solution of the present invention described in the above ( d ) in the surface treatment step of the aluminum support for a printing plate will be described with reference to FIG. In FIG. 4, in the step of purifying the sodium aluminate solution of the present invention shown in FIG. 3, a part of the circulating treatment liquid in the liquid preparation tank 5 passes through the liquid supply pipe 13 to the dissolution tank 34. The solution is sent in a timely manner, while the waste alkali 30 and waste acids 31, 32, and 33 discharged from each surface treatment step are neutralized in a pH adjusting tank 27, and the aluminum sludge 16 is coagulated and precipitated in a coagulating sedimentation tank 28. Is further separated into solid and liquid by a filter press 29 and sent to a dissolving tank 34 at an appropriate time, and the two are mixed with water 19 as necessary in the dissolving tank 34. Dissolved components (impurities)
Is removed. If appropriate amounts of phosphate or slaked lime and soda ash are added to the dissolving tank 34 as needed, it is more effective for removing insoluble components. In the precipitation tank 7, aluminum hydroxide is crystallized using aluminum hydroxide seeds in a supersaturated sodium aluminate solution as nuclei.

For this reason, a mixture of the treatment liquid mainly containing sodium hydroxide solution with reduced aluminum ion concentration and the crystals of aluminum hydroxide is sent to the thickener 8 through the liquid sending pipe 17 to form the crystallized aluminum hydroxide. Are separated by a drum filter 9 through a pipe 18 and collected in a hopper 10. On the other hand, the processing liquid mainly including the sodium hydroxide solution passes through the recovery pipe 20 as a recovery liquid and is returned to the liquid preparation tank.

[0026]

【Example】

(Example 1) The results obtained when the surface treatment of the aluminum plate was performed by the apparatus having the arrangement shown in FIG. 3 while modifying the aluminum hydroxide sludge under the following conditions. Aluminum surface treatment conditions Aluminum plate width 1000 mm Processing speed 50 m / min Crystallization method conditions Precipitation tank temperature 55 ° C to 45 ° C Liquid concentration Total NaOH 100 g / L Aluminum 30 g / L Phosphate addition 1 g / L Filter (35) The time required for the crystallization reaction in the precipitation tank (7) was about 12
It was time.

(Example 2) The results of the case where the surface treatment of the aluminum plate was performed by the apparatus having the arrangement shown in FIG. 4 while modifying the aluminum hydroxide sludge under the following conditions. Aluminum surface treatment conditions Aluminum plate width 1000 mm Processing speed 50 m / min Crystallization method conditions Precipitation tank temperature 55 ° C to 45 ° C Liquid concentration Total NaOH 100 g / L Aluminum 30 g / L Use centrifugal sedimentation machine with separator 4000G at this time The time required for the crystallization reaction in 7) is about 12
It was time.

In each of Examples 1 and 2, the time required for the crystallization reaction of aluminum hydroxide was significantly reduced as compared with the conventional crystallization reaction time of 60 hours.

[0029]

According to the sodium aluminate solution refining method and the aluminum plate surface treatment method of the present invention, (1) the equipment is simpler than the conventional production process by the alkali dissolution method of aluminum or the surface treatment process by the alkali etching method. And the equipment scale can be reduced. (2) Since the residence time for crystallization of aluminum hydroxide in the purification of a sodium aluminate solution can be greatly reduced as compared with the related art, the volume of the crystallization reaction tank can be reduced to ４. (3) The crystallization reaction time can be reduced to 1/4.

(4) The use efficiency of the processing solution used for the surface treatment is increased, and the amount of sodium hydroxide used is reduced. (5) It is no longer necessary to dispose of the treatment liquid discharged outside the system, which was conventionally disposed of as industrial waste, and the aluminum hydroxide sludge discharged from each surface treatment step can be used industrially. It can be transformed into aluminum oxide and sold as an industrial product. As described above, it greatly contributes to improvement of manufacturing equipment, improvement of product quality and cost reduction.

[Brief description of the drawings]

FIG. 1 shows a method of purifying a sodium aluminate solution according to a reference method .
It is a schematic diagram of the structure of the luer alumina manufacturing process.

FIG. 2 is a schematic diagram showing the construction of a new alumina production step by the method for purifying sodium aluminate solution by the centrifugal sedimentation method of the present invention.

FIG. 3 is a schematic structural diagram of a surface treatment method of an aluminum support for a printing plate by a sodium aluminate solution purification method of a reference method .

FIG. 4 is a schematic structural diagram of a surface treatment step of an aluminum support for a printing plate by a method for purifying a sodium aluminate solution by a centrifugal sedimentation method of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Nip roll 14 Return liquid pipe 2 Pass roll 15 Electrolysis treatment tank 3 Spray 16 Aluminum hydroxide sludge 4 Liquid feed pump 17 Liquid feed pipe 5 Liquid preparation tank 18 Pipe 6 Rinse tank 19 Dissolution tank water pipe 7 Precipitation tank 20 Recovery pipe 8 Thickener Reference Signs List 21 sodium hydroxide supply pipe 9 drum filter 22 water supply pipe 10 aluminum hydroxide hopper 23 aluminum plate 11 etching treatment tank 24 anodizing power supply tank 12 etching treatment liquid circulation pipe 25 anodization tank 13 etching treatment liquid circulation pipe 26 electrode 27 pH Adjustment tank 37 Phosphate 28 Coagulation sedimentation tank 38 Evaporation tube 29 Filter press 39 Centrifugal settler with separator plate 30 Wash water waste alkaline solution 40 Ball mill 31 Electrolytic treatment solution overflow pipe 41 Digester 32 Wash water waste acid solution 42 Fla Shutanku 33 washing water waste acid solution 43 Thickener 34 dissolving tank 44 separated fitted with centrifugal settler 35 filter 45 crystallization reaction tank 36 the sludge thickener

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C23G 1/36 C23G 1/36 (72) Inventor Yuzo Inukai 4000 Kawajiri, Yoshida-cho, Haibara-gun, Shizuoka Prefecture Fuji Photo Film Co., Ltd. (56 References JP-A-3-28121 (JP, A) JP-A-2-302316 (JP, A) JP-A-48-38890 (JP, A) JP-A-50-134938 (JP, A) 1-200992 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C01F 7/46 B41N 3/03 C23F 1/36 C23F 1/46 C23G 1/24 C23G 1/36

Claims (2)

(57) [Claims] In a method for purifying a sodium aluminate solution, wherein aluminum hydroxide is crystallized by a hydrolysis reaction from a supersaturated sodium aluminate solution, impurities in the supersaturated sodium aluminate solution are removed by a centrifugal sedimentation machine. Thereafter, a hydrolysis reaction is caused, and aluminum hydroxide is crystallized from the sodium aluminate solution. 2. A method for treating a surface of an aluminum material, comprising separating aluminum ions from a part of a treatment solution containing a sodium aluminate solution to be circulated and used for a surface etching treatment, to remove aluminum ions from the treatment solution. In the surface treatment method for maintaining the concentration at a predetermined level, a part of the treatment solution containing the sodium aluminate solution to be recycled and the non-crystallinity generated when neutralizing waste acid and waste alkali discharged from the surface treatment step of the aluminum material By mixing aluminum sludge containing aluminum hydroxide as a main component, the solution was adjusted to a supersaturated sodium aluminate solution, impurities in the solution were removed by a centrifugal sedimentator, and a hydrolysis reaction was caused.
Aluminum hydroxide is crystallized from the sodium aluminate solution, and aluminum hydroxide is crystallized and removed.
A surface treatment method for an aluminum material, wherein a sodium aluminate solution obtained by adding a sodium-based solution to a circulating treatment liquid is used as the treatment liquid .