JPH0525559B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Fields] Fluorine is contained in natural water, and the Japanese tap water quality standards set the fluorine concentration at 0.8 mg/or less. In industry, fluorine-containing aqueous liquids include processing liquids and wastewater for optical materials, processing liquids and wastewater in the electronics industry, processing liquids and wastewater in the metal smelting industry and metal product manufacturing industry, processing liquids and wastewater in the aluminum industry, and phosphorus. processing fluids and wastewater in the acid industry;
Processing fluids and wastewater from the ceramic industry, etc. The present invention relates to a method for removing fluorine from a fluorine-containing aqueous liquid, and is used, for example, to remove (separate and concentrate) fluorine contained in aqueous liquids such as process liquids and industrial wastewater. [Prior Art] Known methods for removing fluorine include a lime method, a coagulation sedimentation method/clarification filtration method using aluminum sulfate, an ion exchange method using activated alumina gel, and an adsorption method using bone char. [Problem to be solved by the invention] Conventionally, as a method for removing fluorine from a fluorine-containing aqueous liquid by coagulation and precipitation, a large amount of lime was used to lower the pH.
Calcium fluoride is precipitated, flocculated, and clarified through filtration, using a large amount of lime, and the PH
After precipitation at a temperature of 10 or higher, aluminum sulfate or ferric sulfate is added to coagulate and precipitate in neutral or weakly alkaline conditions, followed by clarification filtration. It is difficult to reduce the value to less than /. The present invention uses a new combination of iron monocarboxylate and calcium hydroxide to treat fluorine-containing aqueous liquids at low cost by solid-liquid separation methods such as coagulation sedimentation, flotation, clarifying filtration, and dehydration filtration. The aim is to keep the elementary concentration as low as possible, to about 10mg/or less. [Means for Solving the Problems] The present invention includes adding 0.1 mol or more of a monocarboxylic acid iron salt per 1 mol of fluorine to a fluorine-containing aqueous liquid,
This is a method for removing fluorine from a fluorine-containing aqueous solution, which is characterized by adding calcium hydroxide to make the pH near neutral or alkaline, and separating the formed precipitate and floc from solid and liquid. The monocarboxylic acid iron salt according to the present invention is a salt of a monocarboxylic acid and an iron ion, such as an iron () ion, and examples of the monocarboxylic acid include fatty acids such as formic acid, acetic acid, and propionic acid, glycine, alanine, valine, Amino acids such as leucine, isoleucine, serine, threonine, lysine, and arginine are used. That is, the monocarboxylic acid iron salts include iron formate, iron acetate, iron propionate, iron glycine, iron alanine, iron valine, iron leucine,
Isoleucine iron salts, serine iron salts, threonine iron salts, lysine iron salts, arginine iron salts and other monocarboxylic acid iron salts are generally used as aqueous solutions. The iron monocarboxylate salt according to the present invention can be produced by mixing iron hydroxide/oxide with monocarboxylic acid, alkali monocarboxylate, or an aqueous solution thereof, or by adjusting the PH before or after mixing. , a method of oxidizing, a method of mixing a monocarboxylic acid, an alkali monocarboxylic acid, or an aqueous solution thereof with an aqueous solution of iron salts (hydrochloride, sulfate, nitrate, carbonate, etc.), and adjusting the pH before or after mixing. It can be obtained as crystals or solutions by adjusting methods, oxidizing methods, etc. In the monocarboxylic acid iron salt according to the present invention, iron ions (Fe ²⁺ , Fe ³⁺ ), which are polyvalent cations, may neutralize the monocarboxylic acid equivalently or partially; When neutralizing the remaining cations, the charge of the remaining cations is reduced by anions other than monocarboxylic acids and salts.
Creates a complex ion and has a counter ion. The monocarboxylic acid iron salt according to the present invention may be an equivalently neutralized salt or a partially neutralized salt. The present invention is carried out as follows. An appropriate amount of an aqueous solution of iron monocarboxylate is added to the fluorine-containing aqueous solution and stirred, and then milk of lime is added and stirred to adjust the pH to near neutral or alkaline. Generally, pH is preferably around 8 to 10. At this time, an inorganic flocculant or an organic flocculant is further added as required, and rapid stirring or slow stirring is performed to form a precipitate or floc, followed by solid-liquid separation. Further, as for the method of adding and mixing the chemical solution, an aqueous solution of an iron monocarboxylate salt and milk of lime may be simultaneously added to a fluorine-containing aqueous solution and stirred to adjust the pH to near neutral or alkaline. The amount of monocarboxylic acid iron salt to be added is 0.1 mol or more per 1 mol of fluorine, and approximately 0.3 mol or more is effective. If the amount of the monocarboxylic acid iron salt added is less than 0.1 mol, it is difficult to generate sufficient precipitates and flocs, which is not preferable. As the solid-liquid separation method, sedimentation or flotation in a field of gravity or centrifugal force, gravity filtration, vacuum filtration, pressure filtration, press filter, etc. are applied. The monocarboxylic acid iron salt can be used in combination with an alkali, an acid, a monocarboxylic acid aluminum salt, an inorganic flocculant, an organic flocculant, and the like. As an inorganic flocculant, ferric sulfate, ferrous sulfate,
Aluminum salts such as ferric chloride, polyiron and other iron salts, aluminum sulfate, aluminum hydrochloride, PAC, etc. are used as organic flocculants, polyacrylamide, weakly anion modified polyacrylamide and other polymer flocculants are generally used in aqueous solutions. used as. The monocarboxylic acid iron salt according to the present invention can be mixed with nonionic/cationic polymer flocculants, inorganic salts, monocarboxylic acid aluminum salts, and nonionic organic substances, and their crystals or aqueous solutions can be mixed. and can be used. Carboxylic acids are large, with delocalized π electrons.
It is a weak acid. Calcium monocarboxylate, which is produced by interacting with iron monocarboxylate and calcium hydroxide, has a high solubility in water, and a portion of it dissociates in water to form hydrated ions and complex ions, and forms fluoride ions. This method produces stable, poorly soluble salts at low pH (nearly neutral or alkaline) with a smaller amount used than other methods, and the adsorption activity of iron fluoride, iron hydroxide, and other substances produced contributes. considered to be a thing. Note that amino acids have a carboxylic acid group and an amino group, and the amino group is thought to effectively act on fluorine removal. Example 1 Fluorine-containing factory wastewater (Fluorine concentration: 800-950
mg/), add 500 ml of the aqueous liquid to a volume of 500
mL beaker and use a jar tester.
Stir at 150 rpm, and first add 1.0 mol of iron acetate ()/
Add F-mol and stir for 5 minutes, then add calcium hydroxide solution to adjust the pH to 10.5 at 150 rpm.
After stirring for 10 minutes, 10 minutes at 100 rpm, and 15 minutes at 30 rpm, the supernatant liquid was filtered after being allowed to settle for 30 minutes, and the fluorine concentration of the filtrate was measured. was 9.80mg/. In addition,
The fluorine concentration was measured by "JIS, K-0102 Factory wastewater test method (34)-2 ion electrode method". According to the present invention, when applied to the treatment of wastewater containing high concentration of fluorine, it was possible to reduce the fluorine concentration of the treated water to about 10 mg/or less. Example 2 In the same manner as in Example 1, the iron acetate according to the present invention and ferric sulfate were used in combination, and the results shown in Table 1 were obtained.

[Table] Example 3 in which a remarkable fluorine removal effect was obtained by the combined use of iron acetate and ferric sulfate according to the present invention 3 Fluorine-containing aqueous liquid (fluorine concentration: 115 mg/)
The iron formate () solution (concentration) according to the present invention is
6.2wt%) was added and treated in the same manner as in Example 1, the results shown in Table 2 were obtained.

[Table] Example 4 Fluorine-containing aqueous liquid (Fluorine concentration: 115 mg/)
The iron glycine () solution (concentration) according to the present invention is
8.0wt%) was added and treated in the same manner as in Example 1, the results shown in Table 3 were obtained.

[Table] Comparative Example As a comparative example (other than the present invention), Table 4-1 shows the treatment results of fluorine-containing wastewater when calcium chloride and ferric sulfate were added and slaked lime pH was adjusted.
Table 4-2 shows the treatment results for fluorine-containing wastewater when polyiron or PAC was added to the fluoride and PH was adjusted with slaked lime. Polyiron, PAC forms a stable complex,
Although they have adsorption activity, their ability to remove fluorine through chemical reactions is not good, and methods using them cannot achieve the effects of the present invention.

【table】

[Table] [Effects of the invention] According to the method of the present invention, as can be seen from the examples, the amount of added chemicals is significantly smaller, and the pH is lower than that of the conventional method (nearly neutral to alkaline).
to reduce residual fluoride to about 10mg/or less or about 5mg/
Neutralization with acid for drainage is unnecessary or only a small amount of acid needs to be added.
If a polymer flocculant such as polyacrylamide or weakly anionic polyacrylamide is used for solid-liquid separation, the separation speed of coagulation-sedimentation, clarifying filtration, etc. can be increased, and the present invention as a fluorine removal technology The industrial value is great.

Claims (1)

[Claims] 1 per mole of fluorine in a fluorine-containing aqueous liquid
A fluorine-containing aqueous liquid characterized by adding 0.1 mole or more of a monocarboxylic acid iron salt, adding calcium hydroxide to make the pH near neutral or alkaline, and separating the formed precipitate and floc from solid and liquid. removal method.