KR101782361B1 - Freezing method for the simultaneous removal of hexavalent chromium and phenolic pollutants - Google Patents

Abstract

Challenge: To provide a simple and effective way to remove hexavalent chromium and phenolic contaminants simultaneously.
The present invention relates to a method for preparing hexavalent chromium and phenolic contaminant solutions, Mixing the solution; Introducing a pH adjusting agent into the mixed solution; And a step of cooling the solution containing the pH adjuster, wherein the process is simple and the hexavalent chromium and the phenolic contaminants are effectively removed simultaneously by removing the hexavalent chromium and the phenolic contaminants simultaneously.

Description

[0001] The present invention relates to a method for simultaneous removal of hexavalent chromium and phenolic pollutants,

The present invention relates to a method for simultaneous removal of hexavalent chromium and phenolic contaminants using cooling.

Water quality and soil pollution caused by heavy metals are becoming serious. Among them, hexavalent chromium is widely used in plating, alloys, wood preservatives, tanning of leather, and also in natural environments such as groundwater, soil, and wastewater. Since hexavalent chromium is more toxic than trivalent chromium and has good mobility and is difficult to remove by adsorption, it is preferable to remove the hexavalent chromium by three-dimensionally reducing it with an adsorbent.

In addition, recently, pulmonary pollutants among environmental pollutants are one of the most common pollutants, and it is important to develop a method of treating them because they exhibit toxicity to environment even at very low concentrations.

In general, oxidation and reduction reactions between chemical substances slow down with lower temperature, but the oxidation and reduction reactions between some chemical substances accelerate the reaction rate below a certain temperature. This is because during the freezing process the chemicals are concentrated in the quasi-liquid layer around the ice crystals (freezing condensation effect) and the chemical concentration increases, Because.

Accordingly, it is an object of the present invention to solve the above problems of the prior art and to provide a method for efficiently removing hexavalent chromium and phenolic contaminants simultaneously.

In order to achieve the above object, the present inventors have established an effective method for simultaneously removing hexavalent chromium and phenolic contaminants, thereby completing the present invention.

      The present invention

a) preparing a solution containing hexavalent chromium and a solution containing phenolic contaminants;

b) mixing the two solutions;

c) adding a pH adjusting agent to the mixed solution to adjust the initial pH to less than 5; And

d) cooling the pH-adjusted solution, and a method for simultaneously removing hexavalent chromium and phenolic contaminants.

If the same solution contains both hexavalent chromium and phenolic contaminants, the step of preparing and mixing the hexavalent chromium-containing solution and the phenolic contaminant-containing solution in the above method may be omitted.

Although the concentration of hexavalent chromium and phenol-based contaminants is not limited in the mixture of hexavalent chromium and phenol-based contaminants, the concentration ratio of hexavalent chromium and phenol-based contaminants is 0.25: 1 to 4: 1 mixed solution is effective for simultaneous removal of hexavalent chromium and phenolic contaminants.

The pH adjusting agent of the present invention is not particularly limited as long as it is an acid or a base. In the examples of the present invention, the pH was adjusted using perchloric acid (HClO ₄ ) and / or sodium hydroxide (NaOH).

Further, the present invention is characterized in that the cooling temperature is 0 DEG C or lower, and in the embodiment of the present invention, it is set at -10 DEG C to -30 DEG C.

The method for simultaneous removal of hexavalent chromium and phenolic contaminants according to the present invention will be described in detail. First, a solution containing a hexavalent chromium and a solution containing a phenolic contaminant are prepared and mixed.

The initial pH of the mixed solution is set by adding a pH adjusting agent to the mixed solution. Wherein the pH adjusting agent is perchloric acid (HClO ₄ ) and / or sodium hydroxide (NaOH), and the initial pH is less than 5. And preferably from pH 2 to pH 4. When the initial pH of the solution is adjusted to less than 5, reduction of hexavalent chromium and degradation of phenolic contaminants occurs, with more effective degradation taking place in the pH 2 to pH 4 range.

Next, the pH adjusting agent is cooled. The cooling temperature is 0 ° C or less. And is preferably -10 ° C to -30 ° C. When the above range is satisfied, the solution is frozen, and the reduction of hexavalent chromium and the decomposition of the phenolic contaminants can be effectively performed. When the solution containing the pH adjuster is cooled, the solution is frozen. When the solution freezes, hexavalent chromium, phenolic contaminants and hydrogen ions are concentrated in the quasi-liquid layer present around the ice crystals. Thus, the concentration of hexavalent chromium, phenolic contaminants and hydrogen ions present in the quasi-liquid layer is increased. When the hexavalent chromium, the phenolic contaminants and the hydrogen ions are concentrated in the quasi-liquid layer by the cooling step, the reduction of the hexavalent chromium and the decomposition reaction of the phenolic contaminants can be effectively performed.

When the method of simultaneous removal of hexavalent chromium and phenolic contaminants of the present invention is used, reduction of hexavalent chromium and decomposition of phenolic contaminants are simple and effective.

Further, using the method of the present invention, it is possible to simultaneously remove both hexavalent chromium and phenolic contaminants.

Further, the simultaneous removal of hexavalent chromium and phenolic contaminants of the present invention can be widely used for the purification of groundwater, wastewater, soil and the like containing hexavalent chromium and phenolic contaminants.

Fig. 1 relates to the reduction of hexavalent chromium and the decomposition of 4-chlorophenol by cooling a mixed solution of hexavalent chromium and 4-chlorophenol. Experimental conditions: [4-Chlorophenol] = 20 μM, [Hexavalent chromium] = 20 μM, initial pH = 3.5, ice reaction = -20 ° C, liquid reaction = reaction at room temperature (about 25 ° C).
Fig. 2 relates to the reduction of hexavalent chromium and the decomposition of 4-chlorophenol according to the initial concentration of hexavalent chromium and 4-chlorophenol mixed solution. Experimental conditions: (a) Reaction at [4-chlorophenol] = 20 μM, initial pH = 3.5, -20 ° C, (b) [Hexavalent chromium] = 20 μM, initial pH = 3.5, -20 ° C.
3 relates to the reduction of hexavalent chromium and the decomposition of 4-chlorophenol according to the initial pH of a mixed solution of hexavalent chromium and 4-chlorophenol. Experimental conditions: [4-chlorophenol] = 20 μM, [hexavalent chromium] = 20 μM, reaction at -20 ° C.
FIG. 4 relates to the reduction of hexavalent chromium and the decomposition of 4-chlorophenol according to the cooling temperature of a mixed solution of hexavalent chromium and 4-chlorophenol. Experimental conditions: [4-chlorophenol] = 20 μM, [hexavalent chromium] = 20 μM, initial pH = 3.5.

Hereinafter, the configuration of the present invention will be described in more detail with reference to specific embodiments. However, it should be apparent to those skilled in the art that the scope of the present invention is not limited by the description of the embodiments.

Materials and Chemicals

Sodium dichromate _{(Sodium dichromate dehydrate, Na 2 Cr} 2 O 7 2H 2 O, Cr (VI), Aldrich), 4- chloro-phenol _{(4-chlorophenol, C 6 H} 5 ClO, 4-CP, Aldrich), acetone (Acetone , CH ₃ COCH ₃ , Kanto), sulfuric acid (H ₂ SO ₄ , Kanto), and diphenylcarbazide (C ₆ H ₅ NHNHCONHNHC ₆ H ₅ , DPC, Aldrich). Ion-free ultra-pure water (18.3 MΩCM) was used, which was manufactured by Human-Power I + ultra-pure water manufacturing equipment (Human corporation).

Experimental Method

The concentrations of hexavalent chromium and 4-chlorophenol were usually 20 μM. The hexavalent chromium and 4-chlorophenol were mixed and the initial pH was set with perchloric acid (HClO ₄ ) and sodium hydroxide (NaOH). The mixed solution was poured into a conical tube (15 mL), fixed to a circulating water bath at a low temperature, and cooled to a set temperature (usually -20 DEG C). The time zero of the reaction was the moment when the conical tube was placed in the circulating water bath at the cold temperature. After the reaction was completed, the frozen samples were dissolved in warm water (35 ° C). The reaction in the liquid phase was carried out in a conical tube in the same manner and at room temperature (about 25 ° C).

Concentration analysis of hexavalent chromium

The concentration of hexavalent chromium was analyzed using a diphenylcarbazide (DPC) method. The concentration of hexavalent chromium was calculated by measuring the absorbance at 540 nm using an ultraviolet-visible spectrophotometer (Shimadzu UV-2600).

Analysis of concentration of 4-chlorophenol

The concentration of 4-chlorophenol was analyzed using high performance liquid chromatography (HPLC) (Agilent 1120). At this time, an ultraviolet-visible light detector (UV-visible detector) was used, and the absorbance at 228 nm was measured to calculate the concentration. The column was a ZORBAX 300SB C-18 column (4.6 mm × 150 mm). The eluent was 0.1% phosphoric acid solution and acetonitrile in a volume ratio of 80:20.

Results 1: 6-Chromium and 4- Chlorophenol  Reduction of hexavalent chromium by cooling of the mixed solution and reduction of 4- Chlorophenol  decomposition

The reaction mixture was reacted at room temperature (about 25 ° C) or cooled to -20 ° C by adding a mixed solution of hexavalent chromium and 4-chlorophenol into a conical tube. The results are shown in FIG. It can be seen that when the mixed solution of hexavalent chromium and 4-chlorophenol was cooled, the reduction of hexavalent chromium and the decomposition of 4-chlorophenol occurred rapidly. However, when the mixed solution was not cooled or only the respective materials were cooled, the elimination reaction did not occur. When the mixed solution of hexavalent chromium and 4-chlorophenol is cooled, the solution freezes. When the solution freezes, hexavalent chromium, 4-chlorophenol and hydrogen ions are concentrated in the quasi-liquid layer present around the ice crystals. Therefore, the concentrations of hexavalent chromium and 4-chlorophenol in the quasi-liquid layer are increased, and the concentration of hydrogen ions is also increased to decrease the pH. When the hexavalent chromium, 4-chlorophenol and hydrogen ions are concentrated in the quasi-liquid layer by cooling as described above, electrons are smoothly transferred from 4-chlorophenol to hexavalent chromium, whereby reduction of hexavalent chromium and reduction of 4-chlorophenol Decomposition reaction can be effectively carried out.

Result 2: The hexavalent chromium and 4- Chlorophenol  Reduction of hexavalent chromium and initial reduction of 4- Chlorophenol  decomposition

The results are shown in FIG. 2, which shows the amount of reduced hexavalent chromium and the amount of 4-chlorophenol decomposed according to the initial injection concentration of hexavalent chromium and 4-chlorophenol. When the concentration of 4 - chlorophenol was constant, the amount of 4 - chlorophenol decomposition increased and the amount of reduced hexavalent chromium increased as the initial concentration of hexavalent chromium increased. In addition, when the concentration of hexavalent chromium was constant, the amount of reduced hexavalent chromium increased and the amount of 4 - chlorophenol degraded increased as the initial concentration of 4 - chlorophenol was increased. Thus, it can be seen that the amount of decomposition of 4-chlorophenol and the amount of reduced hexavalent chromium increases as their initial concentration increases.

Result 3: 6-valent chromium and 4- Chlorophenol  The reduction of hexavalent chromium and the reduction of 4- Chlorophenol  decomposition

The results of the reduction of hexavalent chromium and the decomposition of 4-chlorophenol according to the initial pH of the mixed solution of hexavalent chromium and 4-chlorophenol are shown in FIG. It can be seen that when the initial pH of the mixed solution is adjusted to less than 5, the reduction of hexavalent chromium and the decomposition of 4-chlorophenol occur effectively. Generally, the lower the initial pH is, the more effective the reduction of hexavalent chromium and the decomposition of 4-chlorophenol are more effective.

Result 4: Reduction of hexavalent chromium and decomposition of 4-chlorophenol according to cooling temperature

The results of the reduction of hexavalent chromium and the decomposition of 4-chlorophenol according to the cooling temperature are shown in Fig. Reduction of hexavalent chromium and decomposition of 4-chlorophenol proceeded effectively at -10 ° C to -30 ° C, which is the experimental condition. Particularly, the lower the temperature, the faster the reduction of hexavalent chromium and the decomposition of 4-chlorophenol.

Claims (6)

Preparing a solution containing a hexavalent chromium and a solution containing a phenolic contaminant, respectively;
Mixing the two solutions to prepare a solution containing hexavalent chromium and phenolic contaminants at the same time;
Adjusting the pH to less than 5 by adding a pH adjusting agent to a solution containing the hexavalent chromium and the phenolic contaminant simultaneously; And
And cooling the pH-adjusted solution to below 0 ° C. A method of simultaneously removing hexavalent chromium and phenolic contaminants.
Preparing a solution containing hexavalent chromium and phenolic contaminants at the same time;
Adjusting the pH to less than 5 by adding a pH adjusting agent to the solution; And
And cooling the pH-adjusted solution to below 0 ° C. A method of simultaneously removing hexavalent chromium and phenolic contaminants.
The method according to claim 1 or 2,
Wherein the phenolic contaminant is 4-chlorophenol. ≪ RTI ID = 0.0 > 11. < / RTI >
The method according to claim 1 or 2,
Wherein the concentration ratio of hexavalent chromium and phenolic contaminants in the solution containing the hexavalent chromium and the phenolic contaminant is in the range of 0.25: 1 to 4: 1 on the molar basis. ≪ / RTI >
The method according to claim 1 or 2,
Wherein the pH adjusting agent is perchloric acid (HClO ₄ ) and sodium hydroxide (NaOH).
The method according to claim 1 or 2,
Wherein the cooling temperature is between -10 DEG C and -30 DEG C. 6. A method for simultaneously removing hexavalent chromium and phenolic contaminants.

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