KR920009840B1 - Fluorine removing method from the cokes waste water - Google Patents

Abstract

The method for elimination of fluorine in codes waste water comprises (1) firstly, reacting waste water of cokes, which contains fluorine ion, cyanide ion, ammonium ion and the other organic and inorganic materials, with iron chloride (II) in the controlled range of pH 3.5-4.5, (2) secondly, reacting the above waste water with calcium hydroxide in pH 8-9 and (3) sedimentiating and separating fluorine ion in the pH range of 5.0-8.5 adding calcium alunite as a reaction promoting agent and PAA (polyacryl amide) as a flocculation promoting agent.

Description

How to remove fluorine from coke wastewater

1 is a schematic diagram of an apparatus required for practicing the present invention.

2 is a graph showing the effect of removing fluorine ions by the addition of ferric chloride and calcium hydroxide after adjusting the pH with NaOH according to the conventional method.

3 is a graph showing the effect of removing fluorine ions by adding calcium hydroxide and phosphoric acid in an appropriate ratio according to the conventional method.

4 is a graph showing the effect of removing fluorine ions by the addition of an aluminum sulfate flocculant according to the conventional method.

5 is a graph showing the effect of removing fluorine ions by the addition of ferric chloride and calcium hydroxide according to the conventional method.

6 is a graph showing the effect of removing fluorine ions according to the present invention.

7 is a graph showing the effect of COD removal of the complex wastewater generated incidentally according to the practice of the present invention.

8 is a graph showing the effect of CN ⁻ removal of complex wastewater incidentally according to the practice of the present invention.

* Explanation of symbols for the main parts of the drawings

1: Stirrer 2: pH meter

The present invention relates to a method for removing fluorine ions from COKE wastewater, and more specifically, contains not only fluorine ions generated in a coke plant, but also various organic substances and inorganic substances such as phenol, cyan ions, ammonium ions and sulfur compounds. The present invention relates to a treatment method for effectively removing fluorine ions from mixed wastewater. As a conventional method for removing fluorine ions in wastewater, calcium salts such as calcium oxide, calcium hydroxide and calcium carbonate are added to remove and treat precipitates formed by reacting fluorine ions with calcium salts; Precipitation removal by coagulation additives, such as aluminum sulfate; Treatment method by appropriate addition of calcium salt and phosphate; Adsorption and removal by ion exchange resins and activated alumina have been mainly used.

However, these conventional methods have good fluorine ion removal efficiency in wastewater containing high concentrations of fluorine ions, such as pickling processes in steel mills with simple fluorine ions in wastewater or semiconductor companies. It is a complex wastewater containing phenol, cyan ion, ammonium ion, and sulfur compound. The complex wastewater contains 50-80 mg / l of relatively low concentration of fluorine ion, and thus contains low concentration of fluorine ion. When applied to the wastewater is a problem that only 20-40mg / l is removed.

In addition, the adsorption treatment method using an ion exchange resin or activated alumina is not suitable for waste water generated in large quantities, and also has difficulty in regenerating the treatment agent.

Accordingly, an object of the present invention is to add a predetermined amount of ferric chloride, calcium hydroxide and a reaction promoter potassium alum in order to adjust to an appropriate pH range in the coke wastewater containing a large amount of cyan ions, ammonia ions and sulfur compounds It is to provide a method for effectively removing fluorine ions.

In the present invention, COKE wastewater containing fluorine ions is first reacted by adding ferric chloride at room temperature to adjust pH to 3.5-4.5, and then calcium hydroxide (Ca (OH) ₂ ) is added to Secondary reaction by adjusting the pH to 8-9, and then adding potassium alum and PAA (Poly Acryl Amide) to adjust the pH to 5.0-8.5 to precipitate and remove the fluorine ion after separation. The reason for numerical limitation of the present invention is explained below.

When the pH of the first reaction is less than 3.5, an economical problem arises compared to the removal effect, and when the pH is 4.5 or more, it is preferable to adjust the pH to 3.5-4.5 during the first reaction because the efficiency of removing fluorine and cyanide decreases. . In addition, when the pH of the secondary reaction is 8 or less, the removal efficiency of fluorine ions is reduced due to the lack of Ca ⁺⁺ ions, and when the pH is 9 or more, it is uneconomical due to excessive chemical cost and excessive sludge generation compared to the increase of the removal effect. It is preferable to make pH at the time of secondary reaction into 8-9. In addition, when the pH is lower than 5.0 at the last reaction, it is more economical than the removal effect and the floc shape of sedimented sludge is not economical.When the pH is higher than 8.5, the efficiency of removing fluorine ions is significantly lowered to 15 mg / l, which is the environmental management standard. Since fluorine ions in the wastewater cannot be removed, the pH is preferably 5.0-8.5.

In the present invention, when ferric chloride is added as a source of iron ions to the complex wastewater generated in the coke plant and the pH is set to 3.5-4.5 as described above, Fe ₄ {Fe (CN) according to Scheme (1) (2). ) scheme: _{6} 3} is formed as well as a cyan ion removal, excess iron ions is added to the calcium hydroxide to form a ferrous salt such as ammonium ion and the complex form of the fluoride ion _{(NH 4) 2 FeF 6 (} 3) Iron hydroxide and ammonium hydroxide are formed by the co-precipitation to improve the water quality.

If it does not, put into a reaction promoter, potassium alum, the reaction (3) does not occur well well-fluoride treatment, in which the calcium hydroxide to adjust the pH to 8-9, and then 2-order reaction, the fluoride ions in the form of CaF ₂ By adding potassium alum to pH 5-8.5 in order to remove the precipitate well and PAA, a polymer coagulant, to effectively form flocs, the fluorine concentration of the wastewater can be effectively treated.

The apparatus required for carrying out the method of the present invention, as shown in FIG. 1, is a method for primary reaction with fluorine ions by adjusting the pH to 3.5-4.5 by adding ferric chloride solution to coke wastewater containing fluorine ions. First reactor; A second reaction tank for reacting with calcium ions by adding calcium hydroxide as an alkaline agent to adjust the pH to 8-9; It consists of a third reactor to remove fluorine ions by adjusting the pH to 5.0-8.5 by adding potassium alum, which is a reaction promoter to promote the reaction between fluorine compounds and calcium ions in waste water, and PAA, which is an aggregation promoter.

Each said reaction tank is provided with the stirrer 1 and the pH meter 2 for accelerating reaction.

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

As shown in FIG. 1, coke wastewater containing pH 7 containing 50-80 mg / l of fluorine ion was added to the first reactor of the test apparatus, and ferric chloride was added at room temperature to adjust pH to 4 After the first reaction for 5 minutes, the pH was adjusted to pH 8-9 by adding calcium hydroxide in the second reactor, followed by secondary reaction for 5 minutes, and then the pH was adjusted to 7.0-8.5 by adding potassium alum and polymer coagulant in the third reactor. The reaction was carried out for 5 minutes, held for 30 minutes, and subjected to the flocculation treatment. The results were shown in FIG. 6, and the secondary effect was shown in FIG. 7 and FIG.

As shown in FIG. 6, it can be seen that by adding potassium alum, which is the flocculation promoter according to the present invention, the fluorine ion removal rate is 80% or more and the fluorine ion in the composite wastewater is treated well below 15 mg / l.

In addition, it can be seen from FIG. 7 that the COD of 100 mg / l or more was stably treated to less than 60 mg / l after the treatment, and that the cyan ion concentration of 1.2 mg / l was stable to 0.7 mg / l or less from FIG. It can be seen that.

Comparative Example 1

As in Example 1, after adjusting the pH with NaOH in a conventional wastewater containing fluorine ions, 150 mg / l of ferric chloride and 300 mg / l of calcium hydroxide were added to test fluorine ions. It is shown in 2 degrees. According to Figure 2 it can be seen that the fluorine ion was removed to about 32mg / l above pH 9.5.

Comparative Example 2

In the wastewater containing fluorine ion as in Example 1, calcium hydroxide and phosphoric acid were added in a 5: 3 ratio, that is, calcium hydroxide 150 mg / l was added to 90 mg / l of phosphate ions to remove fluorine ions. As shown in FIG. 3, it can be seen that there is almost no fluorine ion removal effect.

Comparative Example 3

In the wastewater containing fluorine ions as in Example 1, a flocculant of aluminum sulfate was added by a conventional method, and the fluorine ion removal experiment was conducted. As a result, it is shown in FIG. The treatment efficiency was better than that of calcium salt, but it was not possible to remove fluoride ion up to 15mg / l.

[Comparative Example 4]

In the wastewater containing fluorine ions as in Example 1, fluoride ion removal experiment was conducted by simply adding 100 mg / l of ferric chloride and calcium hydroxide without adding potassium alum, which is a reaction promoter, according to a conventional method. As shown in Figure 1, the fluorine ion removal effect is not good.

As described above, according to the method of the present invention, even if a low concentration of fluorine ions is contained in the complex wastewater generated in the coke plant, there is an effect of removing fluorine ions more efficiently than the conventional method.

Claims (1)

Ferric chloride was added to coke wastewater containing fluorine ion, cyan ion, ammonium ion, other organics and minerals at room temperature to adjust the pH to 3.5-4.5, followed by primary reaction. After secondary reaction by adjusting to -9, potassium alum and PAA (Poly Acryl Amide) were added to adjust pH to 5.0-8.5 to precipitate and remove fluorine ions. Way.

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