JPS58167425A - Antioxidizing method of iron and the like in solution of alkali aluminate in aqueous caustic alkali solution - Google Patents

Abstract

PURPOSE:To prevent the oxidation of iron in a solution of an alkali aluminate in an aqueous caustic alkali solution and further the coloring of a product prepared by utilizing the same, by adding a specific chelating agent to the solution of the alkali aluminate in the aqueous caustic alkali solution. CONSTITUTION:Any one of gluconic acid or an alkali salt thereof, tartaric acid or an alkali salt thereof, triethanolamine or sorbitol as a chelating agent is added to a solution of an alkali aluminate in an aqueous caustic alkali solution. The amount of the chelating agent is preferably 0.1-10g/l for the gluconic acid or the alkali salt thereof, 0.1-10g/l for the tartaric acid or the alkali salt thereof, 1.0-10g/l for the triethanolamine and 1.0-10g/l for the sorbitol. If the amount is less than the above-mentioned lower limit, the effect of the addition is not produced. If the amount is higher than the above-mentioned upper limit, the effect is not changed and uneconomical.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an aqueous solution of caustic alkali IJ of alkali aluminate.
For example, a caustic alkaline aqueous solution of alkali aluminate is prepared by dissolving crude aluminum hydroxide, such as aluminum hydroxide obtained by treating waste liquid generated in each process of anodizing aluminum and aluminum alloys, in a hot caustic alkaline solution. Concerning the method for preventing the oxidation of iron or low-valent iron present in iron or low-valent iron, products obtained using the caustic alkaline aqueous solution of the alkali aluminate, such as iron or low-valent iron carried into synthetic zeolite or purified aluminum hydroxide. The present invention relates to a method that can also prevent oxidation of compounds.

When aluminum or aluminum alloy is anodized, it is etched in advance with a strong alkaline aqueous solution, but the waste alkaline solution generated by dissolving the aluminum during the etching process is subjected to alkali recovery treatment by the Bayer method, and is processed as a by-product. Aluminum hydroxide is obtained as

Aluminum hydroxide can also be obtained by neutralizing the above-mentioned waste alkaline solution with a waste sulfuric acid electrolyte generated by dissolving a large amount of aluminum during anodizing treatment of aluminum or aluminum alloy.

Furthermore, aluminum hydroxide is also generated during neutralization of washing water used in the process of anodizing aluminum or aluminum alloys.

These aluminum hydroxides contain iron, silicon, magnesium, copper, etc., which are contained as alloy components or impurities in aluminum, although there are differences in degree, as simple substances, hydroxides, and oxides. The aluminum aqueous solution or strong alkaline aqueous solution contains at least 0.001 coulometric power, sometimes more than 1,000 μl, and also contains water of 5 N mass or more.

If these aluminum hydroxides are dissolved in a caustic alkaline hot solution, the aluminum hydroxide will easily dissolve and combine with an alkali to form a caustic alkaline solution containing alkali aluminates, and elements other than iron will be converted into oxides and hydroxides. Alternatively, it may be precipitated or suspended as a single substance, and P can be easily separated using cotton cloth or qualitative paper, but iron or low-valent iron compounds (hereinafter referred to as irons) can be Suspended in the form of fine particles passing through the mesh of cloth or p-cloth, taking in oxygen from the air,
Gradually oxidizes and aggregates to form a reddish-brown precipitate.

In addition, these irons are not easily oxidized even with neutral or alkaline oxidizing agents such as hydrogen peroxide, sodium chlorite, bleaching powder, potassium chlorate, etc., and are not easily oxidized by air oxidation. It gradually oxidizes over several days and becomes a trivalent hydroxide, which coagulates in an alkaline solution as described above to form a reddish-brown precipitate.

Therefore, it is extremely difficult to remove iron from the above-mentioned caustic alkaline solution containing alkali aluminate. Conventionally, a caustic alkaline solution of alkali aluminate still containing iron was used, and an appropriate amount of silicic acid was added. Since synthetic zeolite was manufactured by adding soda and aluminum hydroxide was manufactured by the Bayer process, these products inevitably contained iron, and the iron was oxidized in the air, resulting in a reddish-brown color. The whiteness of the above product was significantly reduced by iron hydroxide (1).

In view of the above points, the present invention has been made for the purpose of preventing air oxidation of iron contained in the aqueous caustic alkali solution of the alkali aluminate. It is used to prevent coloring of synthetic zeolites, aluminum hydroxide, etc. when these products are manufactured using caustic alkaline earth gold.

That is, the present invention is characterized in that a specific amount of any one of the group consisting of gluconic acid or an alkali salt thereof, tartaric acid or an alkali salt thereof, triethanolamine, and sorbitol is added to a caustic alkali aqueous solution of an alkali aluminate. This paper relates to a method for preventing the oxidation of iron, etc. in an aqueous caustic solution of alkali aluminate.

In the method of the present invention, the amount of gluconic acid or its alkali salt added to the caustic alkali aqueous solution of alkali aluminate is 0.1-10 f/l, the amount of tartaric acid or its alkali salt added is 0.1-10 f/l, and the amount of gluconic acid or its alkali salt added is 0.1-10 f/l. Amine is 1.0-10? /l, sorbitol is 1.0-10
It is preferable to use f/l, and the amounts of these (hereinafter referred to as antioxidants) were determined from the experimental results described later.

In addition, any of these antioxidants has no effect when added below the above-mentioned lower limit, and even when added above the above-mentioned upper limit, the effect remains unchanged and is uneconomical.

The method and effects of the present invention will be explained in detail below using experimental examples.

Experimental Example 1 (Preparation of a caustic alkaline aqueous solution of alkali aluminate) Using commercially available high or low grade aluminum hydroxide having the components shown in Table 1, commercially available 45
A caustic soda solution of aluminate was prepared by blending a caustic soda stock solution.

In this 1i14 method, first, put a 45% caustic soda stock solution in a 21 beaker and heat it to 100-110°C, then add a weighed amount of aluminum hydroxide and dissolve the entire amount while stirring until the solution becomes transparent. After reaching the temperature, heating was stopped and pure water was added to bring the total volume to 21.

Table 1 Table 2 Experimental Example 2 (Addition of antioxidant to caustic alkaline solution of alkali aluminate) Caustic soda of sodium aluminate prepared using the +1 high-grade product of Experimental Example 1 at the blending ratio shown in Table 2. solution&l,
A If has the composition roughly shown in Table 3, i In this case, the oxidation rate of iron in the solution is slow and the viscosity is high, making it difficult to pass through the solution. Therefore, dilute it to 1/4 by adding pure water, and after passing, The antioxidant and other reagents according to the present invention shown in are added, and the state of coloration after a predetermined period of time was examined.

Specifically, the above caustic soda solution of sodium aluminate, l&i, and Aii were each added in increasing amounts in pure water to dilute them to 1/4, and the coloring status was visually observed. It was investigated by.

That is, the solution prepared in Experimental Example 1 was added to each 100-40
Place the desired reagent in a 300°C beaker and dilute it to 1/4 in pure water so that the amount after a pause is 0.01'/z or more as shown in Table 4. The amount was increased stepwise and added to each beaker containing 100 ml of the above solution, passed through, placed in each p*t beaker, left open at room temperature for 24 hours, and then added to each beaker. The coloring status of the solution in the beaker was investigated.

The results were similar to those of the solution ' + t A u described above, as shown in Table 4. In Table 4, O indicates no coloring, and × indicates colored samples. Table 4 also shows the rapid oxidizing effect of each drug on iron.
The results of the investigation are also shown.

Table 5 In addition, when tartaric acid and its alkali salts were added in the amounts shown in Table 4 and left in air at room temperature for 24 hours or more, the above solution &l, &l: both 0.5t7 was added in the following amounts. In this case, some oxidation occurred.

For gluconic acid and its alkali salts, the bath 'tL &
When both l and AIf are added at a rate of 0.1t/1 or more, 1
No oxidation was observed even after being left in the air at room temperature for 0 days or more.

In the case of triethanolamine and sorbitol, both of the solutions Ai and 11 are added at a concentration of 1.0171 or more.
No oxidation occurred even after being left in air at room temperature for 10 days or more.

Experimental Example 3 (Preparation of synthetic zeolite from a caustic alkaline solution of alkali aluminate) Using commercially available aluminum hydroxide of +1 high grade and 2 low grade shown in Table 1 of Experimental Example 1, the blending ratio A shown in Table 5 was used.
A commercially available 45% caustic soda stock solution was blended to prepare a caustic alkaline solution of sodium aluminate. Next, during dilution with the same amount of pure water, each of the antioxidants shown in Table 6 was added in the amounts shown in Table 6, respectively. Thereafter, the mixture was filtered, commercially available +3 gold sodium silicate was added thereto, and the mixture was heated and stirred to synthesize zeolite.

Specifically, tAM and 17, which are made by adding pure water and an antioxidant to a caustic soda solution of sodium aluminate, and commercially available S3
Using sodium silicate solution (containing 50% Si) as solution B, first,
After preparing 1000 td of liquid A, pass it through a bitumen cloth or paper at a temperature of 60°C or higher, put it in a beaker No. 21, and while stirring,
Approximately 250 m7 of B liquid heated above 60°C in the mixing ratio of E & 1! , the entire amount of about 450- was added to the above-mentioned mixture ratio of Lagoon 11, and then heated to above so"c and continued stirring. After about 4 hours, the entire amount was filtered and purified water of about 1 to 21 was added. The residual zeolite was washed with water.

The performance of the zeolite obtained with the blending ratio of Alt was as shown in Table 7.

Table 7 also shows zeolite synthesized in the same manner as above using aluminum hydroxide, which is usually recovered from alkaline waste liquid generated in the anodizing process of aluminum alloys.

Table 5 (Liquid A) Table 6 From Table 7, the following can be considered.

(1) By adding an appropriate amount of antioxidant, it is not only possible to prevent the oxidation of residual iron transferred from the raw material aluminum hydroxide into the product zeolite, but also to prevent the oxidation of iron remaining in the product zeolite. A significant amount of iron can be removed just by washing (A1-5 and A7).

On the other hand, when the antioxidant is not added (A6), oxidation of iron cannot be prevented, and iron cannot be removed by washing with water.

(2) Even when the antioxidant according to the present invention is used, the Ca conversion amount of the product zeolite shows a constant value of the theoretical amount, and is within the range of passing as a builder.

Experimental Example 4 (Collecting pure aluminum hydroxide from a caustic alkaline solution of alkali aluminate by Bayer method)
Add a 45% caustic soda stock solution at the mixing ratio shown in /l6ii in the table to prepare an alumin-soda caustic soda solution,
When diluting with 4 times the amount of pure water, the antioxidant shown in Table 8 was added in the additional amount shown in Table 8. Thereafter, a small amount of seed crystals were mixed at room temperature to crystallize aluminum hydroxide, which was washed with twice the amount of pure water as the amount of the caustic soda solution of sodium aluminate and placed in a drying place. The residual iron content of the obtained aluminum hydroxide,
The whiteness was as shown in Table 8.

Table 8 As is clear from Table 8, the iron content contained in the raw material aluminum hydroxide is not oxidized even if 1c remains in the product aluminum hydroxide by adding an appropriate amount of antioxidant. By maintaining a good whiteness and washing the product aluminum hydroxide with water, the residual iron content can be reduced to below the iron content in the raw material aluminum hydroxide.

Agents 1) Akira Agent Ryo Hagiwara - April 1980 Noah 11 Commissioner of the Patent Office Kazuo Wakasugi 2 Title of invention Method for suppressing precipitation of iron etc. in aqueous caustic alkali alkali solution 3, Amendment Relationship with the terms and conditions of the applicant Patent applicant jib +'li 6-1-10 Maeno-cho, Vat-ku, Tokyo
No. 2 - Toranomon f-dai 111 Building'Story (504)'18
Mr. 94 8 A! 't°+7179
) Inside 111 Akira (and 1 other person゛) Target of l correction (1) lj! - Title of the book (2) Claims (3) - Detailed description of the invention 1 Contents of amendment (1) Change the name of the invention in the specification to [Aruin Kei Alkali! Ant Arca, zM47. Correct νhyakuhai such as ``1'' to be a parable.

(2) The scope of claims in Section 1j of the same is corrected in the appendix.

(3) 1111 members lines 19-20 “Exists...
・Antioxidation method” to “precipitation suppression method of dissolved iron compounds”
(4) On page 2, lines 2 to 4 of Oka, ``To purified aluminum hydroxide,
``Preventing'' is corrected to ``Preventing the contamination of 1111 iron hydroxide or ferric hydroxide into purified aluminum hydroxide.''

(Is) [Page 14-4j [I line 5 “Tetsumata a-・
--- It decreased significantly. "Iron or a low-valent iron compound (hereinafter referred to as Tekken) can be combined with a common alkali of the following chemical formula to form a divalent or pentavalent iron compound.

Metallic iron Fe +2 Mol +2 HHO-+ i5 (1
'5(oa)4 )+za ・(1) Ferrous salt 78(OH%+2MOH;: M@(Fe(OH)4
) -----(2) Ferric salt IFe(OH)n+MOH;l:MFeO*+2HmO
・・・・・・・・・・・・(3) However, in the formulas (1) to (3), M represents an alkali metal. It becomes a compound and dissolves, and as a result, the grain of the above r cloth or f paper pass through. In addition, divalent hydroxo iron salt M! [:Fe(OR)4) takes in oxygen from the air and gradually oxidizes to form ferrite MFs01
As the concentration or temperature of the caustic alkaline water S decreases, a retrograde reaction of formula (3) occurs, and ferric hydroxide precipitates and coagulates to form a reddish-brown precipitate. The ferrous compound Ms (Fe(OH)4) gradually oxidizes over several days by air oxidation, and the S@O ferrite MFeO1
In the alkali moat, it precipitates in a layer similar to the above 21 m of hydroxoferric salt, and coagulates to form a reddish-brown precipitate.As described above, 1 gn1 of caustic alkali containing the above alkali aluminate precipitates. To remove the iron fist from the iron, it is necessary to apply caustic alkali, lower the temperature, and let it stand for a few days to precipitate the IIT+iron compound as ferric hydroxide, so the removal of the iron fist is discouraged. Conventionally, synthetic zeolite was produced by adding 91 equivalents of sodium silicate to caustic alkali S*, which is an alkali aluminate containing Tekken, or aluminum hydroxide was produced by the Bayer method. These O products inevitably contain iron. Decreased alkaline O level and t
The white fil of the above product is due to the reddish brown ferric hydroxide that precipitates as the tm temperature decreases! Correct it to ``(-) ``Air oxidation'' in line 1 of page 4 was changed to ``precipitation.''
I am corrected.

(7) Same page 4 1! ``Rlkllization of row Jtr 諌 extraction''
I am corrected.

(8) Mil [Insert ``K after jO into aqueous solution, as a medium-rate agent'' on line 5, and insert ``as a chelating agent'' of ``alkaline aqueous solution K'' on page 5, line 12 of Oka.

(9) On page 5, lines 1, 11, and 19, "antioxidation" is corrected to "precipitation suppression."

Shout: On page 6, line 15, "pure water" is corrected to "preheated pure water."

a Poison Correct the line 4 from just below Oka 7 to [Antioxidant Jtr precipitation suppression].

(2) - On page 6, lines 4-5, "iron...is not slow" is replaced with "iron compound O dissolves [but does not precipitate into crystals]"
I am corrected.

(b) “1/4 times” on the same page, lines 6, 11, and 1s line
is corrected to "4 times".

α◆ Same page, line 7, O "Antioxidation" is corrected to "Prevention of precipitation."

- Corrected "Pure water Jtr heated pure water" written by Oka Ichiichi.

- Oka, page 11, O Insert "after cooling to room temperature" after "add."

(b) Oka! True 6~・Row Ort 9... also shows the meeting. ”
Delete.

(2) Oka 1al [Delete the gold column for "oxidation effect" in the llllJ table.

(b) Correct "polyphagous oxidation" in line 4 of page 11 of Oka to "precipitation of ferric hydroxide."

- Oka page 11, rows C and 1s, “oxidation” is changed to “hydroxide II”.
2@10 precipitation.”

(2) In the first line of page 12 of Oka, before "the same amount", there is "heating when the alkali acid solution is in a high temperature state".
Insert.

- Same 1! The first line of the page, “Oxidation casting”, is changed to “Precipitation suppression”. I am corrected.

(2) Correct "antioxidant" in Table 114 to "# for output control agent".

- Same 13j [Correct l"foJ in the addition amount column of N1m φ1 high-grade product in Table 6 to [LOJ.

- Corrected "antioxidant" in Table 14, True II7 to "precipitation inhibitor" and changed "LoJ" to "-〇" in the column of addition amount of precipitation inhibitor for φ1 high-grade products in -1 in the same table. I am corrected.

- Correct ``IN trace'' in the bottom first line of the 14th true 0$17 table to ``traces''.

-Oka page 15! In lines I and 211, "antioxidation" is corrected to "precipitation suppression".

- "Oxidation of iron" in lines 4 and 9 of opening page 5 is corrected to "precipitation of iron hydroxide."

4. Insert the following sentence between line 14 and line 1s on page 1s.

``In other words, the precipitation inhibitor according to the present invention was originally used for the purpose of suppressing the precipitation of alkali hydroxide due to hydrolysis of alkali aluminate from a caustic alkaline solution containing alkali aluminate.'' Being a %A animal,
Both are O by applying their effect as chelating agents.

For example, in Japan IS* Patent No. 1131571, [aluminum alkali etching solution containing alkali alkali 1]
Add an appropriate amount of a chelating agent such as gluconate sorter, ethylenedeine tetraacetic acid sorter, or flubitol nitrite to 1, add sodium silicate salt, and add a small amount of Iolitom seed crystals in advance at a relatively low temperature. In addition, the purpose of the reaction was to promote the reaction of sodium aluminate and to obtain large allO crystals after the reaction was completed.

However, in order to demonstrate these chelating effects, experience has shown that it is necessary to add chelating agents of st7t or more.
Sorbit, tartaric acid in caustic alkaline water ssi K11j
It was discovered that the chelating effect on iron compounds is far superior to that on alkali alinates, which are 100 to 1000 times more dissolved than iron compounds in a caustic alkaline aqueous solution. There are four. This effect will be verified by the following Experimental Example 4.

” ■ K before “4 times the amount” in the first line of page 16 [4=t=@=6
Insert "Heated".

-Correct "prevention of lling" to "precipitation suppression" in the second line from the Oka 16 purchase and the second line from the bottom.

- "Antioxidant" in Table 8 of 16 is corrected to "precipitation inhibitor."

輔 Correct the first line of page 17 to read ``oxidize'' as ``precipitate''.

Scope of patent claims Akane Caustic alkaline water soluble i1K of alinic acid.

A caustic alkaline aqueous solution of alkali alinate, characterized in that a specific amount of any one of the group consisting of gluconic acid or an alkali salt thereof, distallic acid or an alkali salt thereof, triethanolane, and sorbitol is added as a chelating agent. Method for suppressing precipitation of iron, etc.

Claims (1)

[Claims] In a caustic alkali aqueous solution of an alkali aluminate, a specific amount of any one of the group consisting of gluconic acid or an alkali salt thereof, tartaric acid or an alkali salt thereof, triethanolamine, and sorbitol is added to the aqueous caustic alkali solution of an alkali aluminate. Antioxidant methods such as iron.