KR970001450B1 - Matter for removing fluorine ion from water - Google Patents

Abstract

The removing agents consist of a) over 60 wt% of rare earth metal and b) below 40 wt% of aluminium compound adjusted pH 2~4. a) is chloride,nitrate,sulfate,acetate of rare earth metal(Ce,La,Nb,Pr),and b) is chloride,nitrate,sulfate,acetate of aluminium. It is useful for removing fluorine from wastewater originated by the manufacturing plants of semiconductor,refinery,glass or ceramic and plating plants.

Description

Dissolved Fluoride Ion Remover

The present invention relates to a remover for removing dissolved fluorine ions from waste water containing fluorine, and more particularly, to a dissolved fluorine ion remover capable of effectively removing fluorine using a soluble earth compound and an aluminum compound.

In recent years, with increasing interest in the environment, treatment agents and treatment methods that can effectively and economically remove fluorine (F) contained in wastewater discharged from semiconductor manufacturing plants, smelting plants, glass or ceramic manufacturing plants, plating plants, etc. This is being raised in various ways.

The most common method is to insolubilize fluorine ions in wastewater using Ca compounds, Al compounds, etc. (Japanese Patent Application Laid-Open No. 60-117, No. 62-125894). And a large amount of transcriptional generation, and when fluorine is removed as a Ca compound, theoretically up to 8 mg / l of fluorine ions remain in the solution.

Therefore, it is possible to remove below 15ppm, which is the current discharge standard, but it is impossible to remove to lower concentration which is required in terms of strengthening environmental regulation and total amount regulation and further environmental cleanup.

In this case, too, the concentration of Ca ions in the discharged water is so high that problems such as Ca scale formation occur.

Therefore, a method of using a rare earth to form a very stable insoluble compound with fluorine instead of Ca compound has been proposed to lower the concentration and reduce the amount of transcription.

One of them, a method of removing fluorine by the adsorption method has been proposed in Korea Patent 89-3882.

This adsorptive removal method involves contacting a hydrated insoluble rare earth salt or a hydrated rare earth oxide of a metal with fluorine-dissolved water, followed by contact with an aqueous solution of alkyli to regenerate the adsorbent, and the fluorine sedimentation agent is desorbed. It is effective in the case of fluorine compound or fluorine compound dissolved at low concentration.

However, this method has the disadvantages that the adsorbent used is an insoluble rare earth compound, so the cost of manufacturing the rare earth hydroxide from the raw material is expensive, the amount added is excessive, and the ion exchange is performed only in an acidic solution. The reaction rate is slow because it has to rely on the dependent exchange reaction.

In addition, this method does not use the existing equipment, it is cumbersome to intermittently work in a number of vessels containing a large amount of adsorbent.

In addition, there is a disadvantage that a considerable amount of CaF ₂ residue is generated when the alkali fluoride is treated in the calcination process, and the F remaining in the solution after the treatment is always present at a concentration of about 8 mg / l or more.

Recently, research on the removal of dissolved fluorine using a soluble earth oxide has been conducted. The present applicant has applied for a method of removing dissolved fluorine by a single treatment with a soluble rare earth compound (93-12855).

This method is better than other treatment methods in terms of the removal efficiency of dissolved fluorine and the amount of residues, but the colloidal state of the filtrate is maintained even when the concentration of fluoride ions in the wastewater is relatively low or the coagulant is excessively added depending on the liquidity of the wastewater. It is a big problem in the waste water treatment process because of poor or sedimentation.

That is, since wastewater is usually generated in large quantities, the ease of separation of solid-liquids is a very important factor. Therefore, there is a need for a treatment method having a very high sedimentation rate as well as an effect of removing fluorine ions.

In the conventional method using a rare earth compound, an organic coagulant may be added after adding the rare earth compound. In this case, the sedimentation rate may be increased to some extent, but the injected earth earth ions are dissolved in Na ⁺ , H ⁺ , and NH _4. ^+, OH ^- ions and the like by reacting with the solution of a colloidal state formed by the time-earth Complex fluoride is not possible.

Accordingly, an object of the present invention is to propose a method for removing fluorine at a very low concentration and high efficiency while solving the problems presented previously.

Referring to the colloid-forming ions mentioned above, it is thought that the F ^- ions and the rare earth ions have a similar ion radius, so that the formation of the compound is easy, and thus colloids are generated.

Therefore, in order to solve this problem, it is necessary to find a way to prevent the formation of the compound.

Therefore, the formation of compounds was examined when hydrogen ions, ferric ions, and Al ions were added.

The reason for the addition of hydrogen ions was that the form of the compound was changed depending on the concentration of hydrogen ions. However, the alkali metal and the rare earth fluorine complex mentioned above were still formed when the acid and alkali were added to change the hydrogen ion concentration.

On the other hand, as a result of examining the complex formation in the case of ferric ion or Al ion having a large difference in ion change, ferric ion did not have an additive effect, but Al could completely prevent colloid formation as in the present invention.

Furthermore, when Al is added, the liquid after the treatment is clearer and the relatively expensive rare earth elements can be reduced by that amount, which is advantageous in terms of economics, and there is no need to add a separate inorganic coagulant.

Hereinafter, the present invention will be described.

The present invention comprises a fluorine ion treatment agent characterized by adding an Al compound to a soluble rare earth compound.

In this way, the fluorine ions in the waste water are insolubilized using a treating agent and then fluorine is removed with high efficiency.

The water-soluble composition used in the present invention is 60% or more of the rare earth compound and 40% or less of the Al compound by weight%, and the pH of this water-soluble composition is 2-4.

In the present invention, the rare earth compound is composed of one or two or more of chlorides, nitrates, sulfates and acetates of a rare earth metal composed mainly of Ce, La, Nb, and Pr. The Al compound to be added is an chloride of Al. , Nitrates, sulfates, acetates, one or two or more.

The present invention will be described in more detail with reference to the following examples.

Example 1, Comparative Example 1

Reagent grade NH ₄ F 1g The composition of the artificial waste water (fluorine concentration 51.3㎎ / ℓpH = 5.6) made dissolved in 1ℓ of distilled water, _{CeCl 3 183.5g / ℓ, LaCl 3} 86.4g / ℓ, NdCl 3 54.1g / ℓ, PrCl ₃ 12.0 g / l, Al ₂ (SO ₄ ) ₃ 40.9 g / l, 10 ml of a water-soluble composition containing a small amount of CaCl ₂ , BaCl ₂ , NaCl ₂ (pH = 4.1) was added and reacted for 5 minutes. Caustic soda solution was added to adjust the pH of the solution to 7.5.

After the pH was adjusted, the reaction was further performed for 5 minutes, the agitator was turned off, and the solution was placed in a 1 L cylinder and allowed to settle, and the fluorine ion concentration in the supernatant was measured.

As a comparative example, 10 ml of a water-soluble composition (Comparative Example 1) in which the Al ₂ (SO ₄ ) ₃ was removed from the water-soluble composition was added to the same artificial wastewater.

As a result, in Example 1, the fluorine ion concentration of the supernatant was 1.6 ppm and Al was not detected.

However, in the case of Comparative Example 1, no precipitation was produced and solid-liquid separation was not possible in the colloidal state, so the fluorine ion concentration could not be measured.

Fluoride ion concentration was measured by ion electrode measurement and capacitive method using tomium nitrate.

Example 1, Comparative Example 2

To 1 liter of actual wastewater (fluorine concentration 325.7 mg / l, pH = 23) generated in a semiconductor manufacturer, a water-soluble composition (Example 2) containing 368.5 g / l of a rare earth compound and 92.1 g / l of an Al compound, 63 ml of a water-soluble composition (Comparative Example 2) having a rare earth compound 368.5 g / L without adding the Al compound was added to each of 63 ml, and the experiment was conducted in the same manner as described above, and the fluorine ion concentration was measured.

As a result, in the case of Example 2, the fluorine ion concentration of the supernatant was 3.3 ppm and Al was not detected. Therefore, it is impossible to remove fluorine ions in the form of precipitate.

Therefore, it can be said that the water-soluble composition of Example 2 is more effective for removing fluorine ions.

Examples 3, 4, 5, 6

Al (SO ₄ ) ₃ in a composition containing the same rare earth and trace amounts of CaCl ₂ , BaCl ₂ , NaCl ₂ as in Example 1 for the actual drainage (fluorine ion concentration 81.7 ppm, pH = 2.4) from the TV tube manufacturer for TV 15 ml of each of the water-soluble compositions having 40.9 g / L (Example 3), 19.4 g / L (Example 4), 87.5 g / L (Example 5), and 160.2 g / L (Example 6), respectively. After the experiment was conducted in the same manner as above, the fluorine ion concentration and the Al ion concentration of the supernatant were measured.

As a result, in case of fluorine ion concentration, Example 3 was 1.8 ppm, Example 4 was 1.9 ppm, Example 5 was 3.7 ppm, Example 6 was 4.9 ppm, and in case of Al ions, Examples 3, 4, and 5 were not detected. And only Example 6 was detected at 0.1 ppm.

Claims (3)

Dissolved fluorine ion remover, characterized in that the composition is composed of a soluble rare earth compound and an aluminum compound. The dissolved fluorine ion remover according to claim 1, wherein the soluble rare earth compound is 60 wt% or more and the aluminum compound is 40 wt% or less. The rare earth compound according to claim 1 or 2, wherein the rare earth compound is one or two or more of chlorides, nitrates, sulfates and acetates of a rare earth metal composed mainly of Ce, La, Nb, and Pr. Dissolved fluorine ion remover, characterized in that one or two or more of chloride, nitrate, sulfate, acetate.