JPS61283393A - Method for decomposing oxidizing agent - Google Patents

Abstract

PURPOSE:To more inexpensively treat waste water, by treating heavy metal waste water containing an oxidizing agent by using sodium bisulfite. CONSTITUTION:Waste water containing various kinds of oxidizing agents is received in a receiving tank and the pH thereof is adjusted to 2.5 or less by sulfuric acid. Subsequently, the instantaneous treatment of the oxidizing agents is performed by using an aqueous sodium bisulfite solution to decompose said oxidizing agents. Next, the treatment of a heavy metal is performed by a method wherein the pH of waste water is adjusted to 10 by lime milk to form hydroxide which is, in turn, flocculated and sedimented. By this method, treatment time can be shortened and treatment cost can be further lowered.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to complete treatment in heavy metal wastewater treatment, and more specifically, oxides contained in heavy metal wastewater and pretreatment in each plating/etching process. , is an oxidizing agent used in post-treatment, etc., and relates to a method for completely decomposing wastewater from the leprosy treatment process.

[Prior Art] Conventionally, as a method for treating heavy metal wastewater, such as wastewater associated with plating and etching operations, the following process is usually carried out.

First, the oxidizing agent in the heavy metal wastewater (e.g., hydrogen peroxide, acidic ammonium fluoride, perwt# ammonium, etc.) is treated, and then the heavy metal (e.g., cupric chloride, anhydrous chromic acid, other plated heavy metals, etc.) is treated. ).

The above-mentioned oxidizing agent treatment methods include an alkali aeration method, an alkali treatment method, an alkali activated carbon method, a sulfurous acid method, etc.
Heavy metal treatment methods include ion exchange method, coagulation precipitation method,
There are reverse osmosis treatment methods (RO), ultrafiltration methods (OF), etc., but the reason why the oxidizing agent treatment is performed first is that if the oxidizing agent is not completely treated first, then the ion exchange method, RO method, UF method, etc. Alternatively, heavy metal treatments such as coagulation-sedimentation methods cannot be applied successfully. In other words, the oxidizing agent remains.

In the ion exchange method, RO method, and UF method, the resin and membranes that adsorb and filter heavy metal ions are attacked by oxides.
Each processing method becomes impossible. In addition, in the coagulation-sedimentation method,
Heavy metals generated in alkaline conditions (e.g. Cu, kR, etc.)
Oxygen (02) is precipitated by an oxidizing agent into the hydroxide precipitate.
is attached, and the specific gravity becomes lighter than that of water ()120). In other words, hydroxide does not precipitate, which becomes a cause of hydroxide floating. In addition, in the case of the coagulation-sedimentation method for chromium wastewater, even if it is reduced and completely treated as hydroxide, if the oxidant concentration remains above a certain level in the oxidizing agent-containing wastewater treatment process, trivalent water Chromium oxide is reoxidized to hexavalent chromium, and complete wastewater treatment is not performed. For the above reasons, it is necessary to perform oxidizing agent treatment prior to heavy metal treatment.

[Problems to be Solved by the Invention] As methods for performing oxidizing agent treatment as an important pretreatment in the heavy metal wastewater treatment process, the following describes the alkali aeration method, alkaline method, activated carbon method, and sulfite method described above. There are drawbacks.

1) Alkaline aeration method For example, sodium hydroxide is added to the oxidizing agent-containing wastewater.1
Normally, by raising the hydrogen ion concentration (pH) to 10 or higher and aerating it with air, the oxidizing agent is removed from the oxygen [0] in the air.
2] Reacts with. However, this method has the disadvantage that the reaction time is very long. For example, in order to treat wastewater 1113 with 1100 pp of hydrogen peroxide, a minimum of 8 hours is required, assuming that the amount of air aeration is three times the amount of wastewater per minute to the wastewater 1113.

(2) Alkaline treatment method Sodium hydroxide or calcium hydroxide is added to the oxidizing wastewater (heavy metal-containing wastewater) to raise the pH to 10 or more to generate hydroxide, and by adding a coagulant, the hydroxide is coagulated. Precipitate. However, with this method, the concentration of oxidizer decreases very slowly, hydroxide floats up in coagulation and precipitation, and as mentioned earlier, chromium wastewater is reduced and sodium hydroxide is added as chromium sulfate to produce chromium hydroxide. Cr
Even if it is completely treated with C0H)3, if the oxidizing agent treatment is not completed, trivalent chromium will be re-oxidized to hexavalent chromium, so it has the disadvantage that it cannot be completely treated as wastewater after chromium wastewater treatment. . In addition, heavy metals that have a strong tendency to ionize will be redissolved, making it necessary to start the process again.

3) Alkali-erotic carbon decomposition method: Add aqueous sodium hydroxide solution to the oxidizing agent wastewater, and adjust the PH
By raising the value to 10 or more and adding activated carbon, the activated carbon comes into contact with the oxidizing agent (hydrogen peroxide) and self-extinguishes. In other words, activated carbon tries to absorb water (H2O), so oxygen (02) is released, and hydrogen peroxide (H202) absorbs water (H2O).
2O). At this time, the -pH is set to the strongly alkaline side, and the treatment progresses more quickly as the amount of activated carbon added increases. However, activated carbon is very expensive, and furthermore, an excessive amount of sodium hydroxide solution is required to increase the pH, which poses a problem of processing cost.

Furthermore, the activated carbon method, alkaline treatment method, and alkaline aeration method described above have the drawback that oxidizing agents other than hydrogen peroxide do not provide much treatment effect.

4) Sodium sulfite method The sodium sulfite method allows reaction treatment regardless of whether it is alkaline or acidic, but it is expensive and has the problem of processing cost.

The present invention solves the above-mentioned drawbacks and provides a processing method that makes processing time and processing cost faster and cheaper than before.

[Means and effects for solving the problems] The present invention provides an oxidizing agent decomposition method characterized in that sodium hydrogen sulfite is used to decompose the oxidizing agent in the treatment of heavy metal wastewater containing the oxidizing agent. It is. Among the oxidizing agents, the treatment of hydrogen peroxide will be described below.

The principle behind the treatment of hydrogen peroxide, which is an oxidizing agent, with sodium hydrogen sulfite can be expressed as a chemical reaction equation as follows.

2H20z+H2SO4+2NaHSO3+ 2H20
+Na25Oa+2H2Sb To explain the above reaction formula,
Sulfite ion (SO32-) becomes sulfate ion (SO42-
) Oxygen (0)1 of hydrogen peroxide (l202)
5032- becomes 5042-, and the hydrogen (H) of sodium hydrogen sulfite becomes sulfur @ (H2SO4). Also, the sodium ion of sodium hydrogen sulfite (
For Na◆), 8032 of sodium bisulfite
- becomes 5042- through the above reaction, and combines with Na. to form sodium sulfate (Na2SO4). As a result of the above, H2O2 becomes water (H2O).

The above reaction must be carried out smoothly in a wastewater treatment facility. Therefore, each oxidizing agent-containing wastewater is received in a receiving tank,
Adjust the pH to 2.5 or less in sulfuric acid. Here, the oxidizing agent-containing wastewater has a pH of 2.5 or less, so sulfuric acid is not necessary, and the oxidizing agent is instantaneously treated using an aqueous solution of sodium bisulfite. An oxidation-reduction potentiometer (ORP meter) is used to sense the treatment reaction. For the treatment of zero-order heavy metals, in which the oxidizing agent is decomposed by performing the above-mentioned treatment, it is possible, for example, to make the metal alkaline to pH 10 with milk of lime, and to generate hydroxide and coagulate and precipitate it. Further, treatments such as ion exchange method, RO method, UF method, etc. can also be performed. In addition, in the above description that hydroxide is generated when the pH is set to 10, the basis for setting the pH to 10 is that if it is below PHIO, hydroxide will not be formed, and if it is above 110, heavy metal hydroxides that have a strong ionization tendency will be generated. This is because the heavy metals will be redissolved and the concentration of each heavy metal will increase.

[Example] The following experiment was conducted in consideration of the principle of decomposition and the processing procedure described above.

Step 1) Hydrogen peroxide-containing wastewater, ammonium persulfate-containing wastewater, and dichloromethane, which are the washing water of chemical polishing and etching processes.
A total of three types of copper-containing waste water were mixed together at 1 fL each, and 11 samples were taken as samples.

2) Check the hydrogen peroxide concentration. (Concentration test method is described below.
3) Adjust the pH of the above solution to 2.5 or below with sulfuric acid, add the required amount of sodium hydrogen sulfite aqueous solution (40 g/liter) to the hydrogen peroxide concentration determined in 2), and roughly analyze the solution using the H2O2 analysis method. While checking, add sodium bisulfite solution 2 cc at a time until the concentration of hydrogen peroxide becomes 3PP or less.

4) After the procedure in 3), measure the redox potential. (OR
Using a P meter) The resulting concentration of hydrogen peroxide is approximately 1100 pp, and the calculated amount of sodium bisulfite required is 0.31 g.

However, in this example, ammonium persulfate and chloride! $
Since the two copper-containing wastewaters are mixed, the following reaction occurs.

(NH4)2S20B+CuC1'2+Cu5Oa+(
NHn)zsOn+cj'2 Chlorine is liberated in this way, and due to the production of this oxidized substance, sodium bisulfite is required in excess of the above calculated value. That is, since the concentration of Ch was also about 1100 pp, the total required amount was 0.45 g from the above calculation formula. 40g/I! It is about 11 cc as a solution. As a result of the experiment, the hydrogen peroxide concentration was <1 ppm at 12 cc. Further, the oxidation-reduction potential at that time was 250+wV. The redox potential for chromium treatment is 270 mV, ie a redox potentiometer (ORP meter) can be used.

H2O2 analysis method (reagents) 5.5 g of TiCRa, 10 g of (NH4)2S0
8M H250450 shoes! and heat to dissolve. After cooling, water 175a+1! Add carefully to make a constant volume of 250 toge.

Test method) A certain sample 1 to 3 layers i' (10 to 100 as H20z)
10III! Transfer titanium reagent solution to a volumetric flask at 1.0 mA', i3M H,SO+ 2.5
mj) and heated at 60°C for 10+sin. After cooling for 5 minutes, the absorbance at 407 nm is measured using a blank control.

Standard lOlg, 50gg, 1100J
L〈Standard〉 Standard solution: H2O2 (35%) 0.1ai) with distilled water to 100+wI! Dilute it in water to make a standard stock solution, and standardize the concentration by iodometric titration.

25mj) 1OII of distilled water in a stoppered Erlenmeyer flask! %(1
÷5) Sulfuric acid 1III! , Kl O, 2g,
Add to this the standard stock solution 1.0IIi! Add, stopper, mix, and let stand for 15 minutes. Titrate with 0.0 IN sodium thiosulfate using a burette. (Indicator, starch) Perform a blank test and calculate the concentration using the following formula.

Standard stock solution 1 all = H2O20,1? mg
(T-B) f (T: standard value, B: blank test value, f: titer) Take the calculated amount of the standard stock solution with standardized concentration into a volumetric flask and dilute with distilled water to make a solution containing 10 JLgH20z in 1 intestine p. adjust.

Ammonium persulfate method trial drug) a, ammonium persulfate, d, 2% aniline sulfuric acid solution, e, phosphoric acid, f, hydrochloric acid, g, benzene.

<Equipment and instruments> A6 spectrophotometer (Hitachi 181), b, shaker, C, water bath, d, stirrer, 80 rotor, f, air pump, g, graduated cylinder (100 m), h, hall Pipette (1, 5, 10 layer I, i, Komagome pipette (5mi'), j, beaker (100m)
Sentence).

k, colorimetric tube (50 liters 1), 1. Separating funnel (100 μU).

<Flow) Water test (100 points) ↓ 2% aniline sulfuric acid solution 511I! ↓ Concentrate to 30+wjJ ↓ Transfer to 10hJ separatory funnel ↓ Salt #2taR, benzene 5tsR ↓ Transfer the aqueous layer to a 50-layer p colorimeter tube ↓ 50+sj) ↓ Colorimeter standard 0, 250.500.1000.2000 g In addition,
Standard operates in the same way.

[Effects of the invention] Effects of applying sodium bisulfite as a reducing agent 1) By making the oxidizing agent acidic with sulfuric acid and adding the required amount of sodium bisulfite, the hydrogen peroxide concentration becomes <lpp, and the redox potential also decreases. Since the value was within the appropriate range of 250 V, the oxidizing agent was treated in a few seconds by applying a redox electrometer as a treatment process, and the treatment time was extremely shortened. Furthermore, by using sodium bisulfite, treatment can now be performed at a lower cost than before.

2) Applicable to chemical polishing and etching process wastewater that contains hydrogen peroxide, and when the oxidizing agent contains low heavy metals (ferric chloride) and the oxidizing agent-containing wastewater flows out, other heavy metals (nickel sulfate, nickel sulfate, Oxidizing agents can be decomposed even after they are mixed with process wastewater (nickel chloride, zinc sulfate, copper sulfate, etc.). In addition, various oxidizing agents (ammonium persulfate, etc.)
It can also be applied to relationships.

It can be said that this is also suitable for processing using a redox electrometer.

Claims (1)

[Claims] An oxidizing agent decomposition method characterized in that sodium bisulfite is used to decompose the oxidizing agent in the treatment of heavy metal wastewater containing the oxidizing agent.