JP2022121251A - Method of decomposing harmful organic chemical compound in effluent - Google Patents

Abstract

To provide a simpler method of decomposing a hardly decomposable or malodorous harmful organic chemical compound contained in effluent, relative to a conventional one.SOLUTION: A covalent bond of an organic chemical compound in effluent can easily be dissociated/cut by adding a solid peroxide comprising nickel peroxide as a primary component to effluent including a harmful organic chemical compound, and by increasing an amount of oxygen dissolved in effluent and/or adding sodium hypochlorite thereto, and thereby a harmful organic chemical compound in effluent can be decomposed.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a method for decomposing harmful organic compounds contained in various waste liquids, particularly persistent harmful organic compounds.

Organic compounds contained in various waste liquids are usually treated by oxidative decomposition. However, persistent organic compounds such as 1,4-dioxane contained in landfill groundwater, 1,2-dichloroethane contained in waste sulfuric acid, and dioxins with a high toxicity equivalence index cannot be decomposed by normal aeration treatment. Expensive equipment such as a high-temperature decomposition device (Patent Document 1) and an electrolysis device (Patent Document 2) was required.
Further, in the oxidation treatment at room temperature, an ozone-containing gas is used as the oxidizing gas, and an ultraviolet irradiation device is required (Patent Document 3).

Furthermore, malodorous components such as methyl mercaptan cannot be completely decomposed by normal aeration treatment, and if even trace amounts remain, they become a source of malodorous substances. ) and equipment consisting of multiple processes (Patent Document 5).

Thus, it has been desired to develop a simpler method for decomposing and removing persistent organic compounds and trace amounts of malodorous components contained in the waste liquid.

Japanese Patent Application Laid-Open No. 2004-057923 JP 2014-014754 A JP-A-2008-126125 Japanese Patent Application Laid-Open No. 2018-083170 Japanese Patent Application Laid-Open No. 2007-319842

It is an object of the present invention to provide a method for decomposing organic compounds that are difficult to decompose and have malodorous components contained in various waste liquids by a simpler method than conventional methods.

The inventors of the present invention believe that if the covalent bonds of harmful organic compounds contained in wastewater can be dissociated and cleaved, any persistent organic compounds can be decomposed. As a result of intensive studies, it was found that by using nickel peroxide as a solid peroxide and increasing the amount of dissolved oxygen in the waste liquid and/or adding sodium hypochlorite, organic compounds in the waste liquid can be eliminated. The inventors have found that the covalent bond can be easily dissociated and cleaved, leading to the present invention. According to experiments by the present inventor, many organic compounds can be decomposed by adding a solid peroxide containing nickel peroxide as a main component, increasing the amount of dissolved oxygen in the waste liquid, or adding sodium hypochlorite. Organic compounds that could not be decomposed by these combinations could also be decomposed by combining nickel peroxide, increasing the amount of dissolved oxygen in the wastewater, and adding sodium hypochlorite.

Aspects of the present invention are as follows.
(1) Adding a solid peroxide containing nickel peroxide as a main component to the waste liquid containing harmful organic compounds, and increasing the amount of dissolved oxygen in the waste liquid and/or adding sodium hypochlorite. A method of decomposing harmful organic compounds in a waste liquid by adding
(2) The method of decomposing a toxic organic compound of (1), wherein the toxic organic compound is a persistent organic compound.
(3) The method of decomposing the harmful organic compound of (1), wherein the harmful organic compound is a malodorous organic compound.

In the present invention, "nickel peroxide" refers to nickel trioxide or a mixture of nickel trioxide and nickel oxide hydrate. Further, the "solid peroxide" is obtained by adding and mixing magnesium oxide and alumina silica as a solidifying agent to the nickel peroxide, followed by solidifying and molding.

In the present invention, in order to increase the dissolved oxygen in the waste liquid containing harmful organic compounds, a well-known aerator can be used to aerate air or an oxygen-enriched gas into the waste liquid to increase the amount of dissolved oxygen. It doesn't matter what kind.

The solid peroxide material in the present invention is obtained by solidifying nickel peroxide with magnesium oxide and alumina silica. It is desirable to limit the amount of Further, if an inorganic fiber material such as glass fiber is blended, the strength of the solid peroxide material is improved, so that the amount of the solidifying agent used can be reduced.

The dissociation/cleavage mechanism of the covalent bond of the harmful organic compound presumed in the present invention will be explained with reference to the schematic diagram of FIG. (1) indicates a state in which 1,4 dioxane, sodium hypochlorite, and solid peroxide are present in water. As shown, the sodium hypochlorite contacts the solid peroxide material. In (2), sodium hypochlorite in contact with the solid peroxide is decomposed to generate nascent oxygen, and this nascent oxygen attacks the covalent bond of 1,4 dioxane. show. (3) shows a state in which the covalent bond of 1,4-dioxane attacked by nascent oxygen is dissociated and cleaved.

In place of sodium hypochlorite, hydrogen peroxide, chlorine oxides other than sodium hypochlorite, permanganate, and chromate can release active oxygen, but nickel peroxide is also reduced. , the reduced nickel hydroxide cannot be peroxided. On the other hand, acidic oxidants such as chlorine water, chlorocyanuric acid, and persulfates can oxidize nickel hydroxide into peroxides, but cannot generate active oxygen.

Nickel peroxide is preferably mixed with a solidifying agent, molded, filled in a filling tank, and brought into contact with a waste liquid to which sodium hypochlorite has been added. Since sodium hypochlorite may cause a chlorine addition reaction with the substance to be oxidized over time, it is desirable to add sodium hypochlorite to the waste liquid just before the reaction tank.

After sodium hypochlorite is added, there is a slight time lag until it completely decomposes and generates all the oxygen in the nascent stage, so the amount of sodium hypochlorite added is controlled according to the fluctuation of the COD of the waste liquid. It is desirable to Also, in the case of the "multi-stage addition method" in which the amount of oxygen compound solution added is reduced in stages according to the decrease in COD, it is advantageous because the amount of oxygen compound solution used can be reduced.

Furthermore, if it takes too long to treat the waste water after mixing the sodium hypochlorite solution with the waste water, side reactions other than oxidation, such as chlorine addition reaction to the oxidized substance, may occur. It is desirable to add it before the waste water is introduced into the reaction vessel or reactor, as it may cause difficulties in the oxidation reaction. In addition, when there are substances to be oxidized, such as amine salts, which are particularly susceptible to chlorine addition reaction in the waste water, caustic soda is added to the waste water together with the oxygen compound solution, or before or after the addition of the oxygen compound solution, and chlorine is added to the waste water. It is desirable to prevent addition reactions.

According to the method of the present invention, persistent 1,4-dioxane, 1,2-dichloroethane, or dioxins can be decomposed in a relatively short period of time. can be lowered to an odor index of 9 or less (incapable of being detected by the human sense of smell) in as little as two hours.

Schematic diagram of how the covalent bond of an organic compound is cleaved by the method of the present invention.

Examples of the present invention are described below, but the present invention is not limited thereto.

<Production of solid oxidizing material 1>
Glass fiber with a length of about 3 to 5 mm, which has been pretreated with sulfuric acid and potassium permanganate to remove organic matter, is added to a nickel salt solution such as nickel sulfate, nickel nitrate, and nickel chloride at a concentration of about 10 to 25%. Add about 10 to 30 wt%, then convert the nickel content to nickel hydroxide (Ni(OH) ₂ ) with a 19 to 25% caustic soda solution, and then add enough sodium hypochlorite solution to convert this to Ni(OH) ₃ is added below 30°C. Next, the cake is washed with water and filtered to obtain a cake with a moisture content of 35 to 45%, to which magnesium oxide or alumina silica with a nickel content of 25 to 50% is added and kneaded, molded into an appropriate shape, and peroxided. material. The size of this molding may be appropriately determined according to the capacity of the processing apparatus, etc., and the length of the glass fiber may also be determined according to the size. Moldings are allowed to stand for 1-2 days and then dried at 40°C.

When sodium hypochlorite (NaClO) is added to nickel oxide (NiO) to make peroxides of Ni ₂ O ₃ and Ni ₃ O ₄ , nickel peroxide is partially mixed with nickel oxide to produce hypochlorite. When treated with sodium chlorate, it can be converted to peroxide in a shorter time, and by repeating the sodium hypochlorite treatment by adding nickel oxide to the generated nickel peroxide, a large amount of peroxide can be produced in a short time. Nickel can be produced.
To 100 parts by weight of nickel peroxide thus obtained, 100 parts by weight of calcined magnesite, 8 parts by weight of alumina silica, and 39.6 parts by weight of water are added, mixed and kneaded, and then granulated to about 6 mm in diameter. It was air-dried for 24 hours to obtain an oxidizing material.

<Decomposition of 1,2-dichloroethane in waste sulfuric acid by combination of aeration and oxidant>
[Test 1] 10 liters of normal waste sulfuric acid was aerated by blowing 7 liters of air per minute for 144 hours.
[Test 2] 10 liters of waste sulfuric acid containing acetic acid was aerated by blowing 7 liters of air per minute for 240 hours.
The aeration device used in this experiment is manufactured by Ams Engineering (CATH-F).
The results of measuring the amount of 1,2-dichloroethane in the waste liquid in each test are shown below. As is clear from the table, the amount of 1,2-dichloroethane in the waste sulfuric acid can be reduced to below the reference value only by aeration, but by the method of the present invention, by combining the peroxide material of nickel peroxide, , could be dramatically reduced.

<Decomposition of 1,4-dioxane in leachate by combination of aeration, peroxide and sodium hypochlorite>
[Test 1] 6.0 l of underground leachate containing 1,4-dioxane was aerated with 3.75 l/min of air for 1 hour.
[Test 2] 200 g of nickel peroxide was added to 6.0 liters of underground leachate containing 1,4-dioxane, and the mixture was aerated with air at 3.75 liters/minute for 1 hour.
[Test 3] 200 g of nickel peroxide and 300 cc of sodium hypochlorite were added to 6.0 liters of underground leachate containing 1,4-dioxane, and the mixture was aerated for 1 hour at 3.75 liters/minute of air.
Aeration device used (CATH-F, manufactured by Ams Engineering Co., Ltd.)
The results of measuring the amount of 1,4-dioxane in the leachate in each test are shown below. As is clear from the table, 1,4-dioxane could hardly be decomposed by aeration alone or by a combination of aeration and peroxide. - the amount of dioxane could be reduced dramatically.

<Oxidative Decomposition of Organic Compounds by Combination of Various Oxidizing Agents and Nickel Peroxide>
Using 0.25% ethyl alcohol and 0.25% triethanolamine as organic compounds, (1) sodium hypochlorite solution, (2) nickel peroxide, (3) sodium hypochlorite solution and peroxide The results of treatment with nickel oxide were as follows.
(1) When an excess amount of sodium hypochlorite solution was added to each of 0.25% ethyl alcohol and 0.25% triethanolamine, 48% of ethyl alcohol was decomposed after 2 hours, and triethanolamine 39% decomposed.
(2) When a similar test was performed using nickel peroxide instead of the sodium hypochlorite solution, about 90% of ethyl alcohol and triethanolamine could be decomposed after 2 hours, but they were reduced. The operation was complicated because it was necessary to regenerate nickel peroxide.
(3) According to the present invention, when an excess amount of sodium hypochlorite solution is added to each of ethyl alcohol and triethanolamine, and then nickel peroxide is added, ethyl alcohol is 93% after 15 minutes, triethanolamine is could each be decomposed by 96% after 45 minutes. Also, nickel peroxide did not need to be regenerated, as it only functions as a catalyst.

<Decomposition of Odor Components Using Methyl Mercaptan Stock Solution>
A 50-liter reaction tank was prepared, and 9 kg of methyl mercaptan undiluted solution was charged into the tank, then 450 g of a peroxide agent containing nickel peroxide as a main component was added, and hot water was passed through the jacket of the reaction tank to heat the inside of the reaction tank. The temperature was adjusted to 40-45°C. In this state, the reactor was aerated at 7.50 l/min, and the odor, temperature, DO, OPR and pH were measured after 30, 60, 90 and 150 minutes. Table 3 shows the measurement results.
The evaluation of "odor (human)" is based on the results of sensory tests based on: large: strong odor, medium: easily perceivable odor, slight: barely perceptible odor, and none: inability to perceive odor. The "odor index" is defined as a value obtained by multiplying the logarithm of the dilution factor by 10 when diluted with odorless air until the odor is no longer perceived.

As can be seen in Table 3, the odor was reduced between 30 and 60 minutes, and could be made almost odorless between 90 and 150 minutes. When humans sniff odors, the way they perceive odors changes depending on the shape of the odor-generating liquid container, and the measurement by the odor sensor also changes even if the measuring part shifts slightly. However, if the ORP (oxidation-reduction potential) is -550mv or less, humans will not be able to perceive the odor.

In addition, experiments were carried out by changing the addition amount of peroxide and the amount of aeration using waste liquid with a strong odor.
Two 50-liter reaction tanks were prepared, 9 liters of methyl mercaptan waste liquid was put into each tank, and then a predetermined amount of a peroxide agent containing nickel peroxide as a main component was put into each tank. In this state, each tank was aerated with a predetermined amount of air for 90 minutes, and the odor index before and after treatment was measured. Table 4 shows the measurement results. Almost the same result was obtained with the waste liquid (2) in which the amount of aeration was reduced, and the odorous components could be almost completely decomposed in the waste liquid (3) with the addition amount of peroxide and the amount of aeration increased.

<Decomposition of Odor Components in Amino Acid Waste Liquid>
The aerator was operated to aerate 900 cc of the amino acid waste liquid at a rate of 3.75 l/min. After 2 hours, there was no change in the strong odor peculiar to amino acids, so 90 g (10%) of the peroxide material of the present invention and 45 cc (5%) of sodium hypochlorite were added and aeration was continued.
Aeration device used (CATH-F, manufactured by Ams Engineering Co., Ltd.)
18 hours after the start of aeration, the pungent odor disappeared, and 24 hours after the start of aeration, the odor was reduced to a faint odor.

<Decomposition of Odorous Components of Ammonia Waste Liquid>
90 g (10%) of the peroxide material of the present invention and 45 cc (5%) of sodium hypochlorite were added to 900 cc of ammonia waste liquid while operating the aerator to aerate at 3.75 l/min.
Aeration device used (CATH-F, manufactured by Ams Engineering Co., Ltd.)
Two hours after the start of aeration, no odor was felt at all, and 15 hours and 30 minutes after the start of aeration, the aeration was stopped.

<Decomposition of odorous components of shellfish sludge>
Although the mussels that develop and adhere to the cooling water passages of the power plant are removed periodically, the collected mussels immediately give off a strong odor.

These odor types are
Ammonia: 10-1000ppm
Hydrogen sulfide: 0.05-4.0ppm
Methyl mercaptan: 0.1-8.0 ppm
Met. (Equipment used: GV-100S detector tube type gas measuring device manufactured by Gastech)
Grind the collected shellfish to about 10 to 15 mmφ together with the shell, put 2 kg each into three 20 L containers (A, B, C), add 10 L of purified water, and add a predetermined amount of peroxide and hypochlorite to each container. Acid soda was added and aeration was performed for 30 minutes at an air volume of 3.75 l/min. The odor components in the shellfish sludge were 50 ppm or less for ammonia, 1.0 ppm or less for hydrogen sulfide, and 1.0 ppm or less for methyl mercaptan. rice field.
Aeration device used (CATH-F, manufactured by Ams Engineering Co., Ltd.)
2 kg of new shellfish sludge was added to one of the aerated containers, and further aerated for 30 minutes at an air volume of 3.75 l/min. This is container D.
The odor components in the shellfish sludge before and after the aeration of containers A to D are shown in Table 5 below, and the odor was dramatically reduced in each case.

<Comparison between sodium hypochlorite alone and peroxide and combination>
To the organic compounds shown in Table 6, changes in COD over time were investigated in cases where sodium hypochlorite alone was added and in cases where sodium hypochlorite and a peroxide were added in combination.
The results are shown in Table 6. In the case of sodium hypochlorite alone, the decrease was only about 30% even after 2 hours, but when sodium hypochlorite and peroxide were added in combination, the , decreased by about 90% in a short period of 10 to 20 minutes.

<Inorganic Wastewater>
A predetermined amount of sodium hypochlorite was added to the inorganic wastewater shown in Table 7, and the change in COD over time was measured. rice field. In particular, almost 100% of the sodium nitrite wastewater was treated with the theoretical addition amount of COD and a short period of about 10 minutes. In addition, the cyanide-containing effluent can be treated to a higher degree, and can be treated from a low concentration to a high concentration. Thus, it was found that the single treatment of sodium hypochlorite is sufficient for inorganic wastewater.

<Alcohol-based waste water>
When the change in COD over time was measured when sodium hypochlorite and peroxide were added to the alcohol-based wastewater shown in Table 8, the wastewater was 85-85% in a short period of 10-30 minutes. A treatment rate of 99% was shown. In particular, although the decomposition rate of isopropyl alcohol-containing wastewater varies slightly depending on the conditions, it is possible to decompose 90% or more, but the amount of additive required is about four times the theoretical COD value. Ethylene glycol-containing wastewater could be treated with a decomposition rate of 85-90% at about twice the theoretical amount of COD. Thus, it can be seen that alcohol-based wastewater can be sufficiently treated by the combined treatment of the present invention.

<Phenolic Wastewater>
Changes over time in COD and phenol concentrations were measured when adding sodium hypochlorite and a peroxide agent to the phenol-based wastewater shown in Table 9, and in combination with air aeration. In the case of phenolic wastewater, COD treatment and phenol treatment are required, and it is necessary to carry out treatment according to the purpose. Phenol can be decomposed almost 100% with more than the theoretical amount of additive for COD. The decomposition rate drops sharply.

<Aldehyde wastewater>
When the change in COD over time was measured when sodium hypochlorite and peroxide were added to the aldehyde-based wastewater shown in Table 10, the addition of about twice the theoretical amount of COD resulted in 95 % COD treatment was possible.

<Organic acid wastewater>
When the change in COD over time was measured when adding sodium hypochlorite and peroxide to the organic acid wastewater shown in Table 11, it was found that sodium citrate and sodium stearate were about the theoretical amount of COD. With the addition of additives, 90% or more COD treatment was possible, but for acetic acid compounds, the amount of additives required is about 5 to 10 times the theoretical amount of COD.

<Amine wastewater>
Changes in COD over time were measured when hypochlorous acid and peroxide were added to the amine wastewater shown in Table 12. Since the amine compound is alkaline and can decompose 70 to 90% COD by reacting with the additive, this experiment was carried out in an alkaline environment.
The triethanolamine-containing waste water had a decomposition rate of about 70% in a reaction time of 15 minutes using 2 to 4 times the theoretical COD amount of the additive. In the case of fatty acid secondary amine-containing waste water, the reaction time was set to 30 minutes, and COD theoretical amount of additive was used, and 80% or more was decomposed.

<Other organic wastewater>
Changes in COD over time were measured when sodium hypochlorite and peroxide were added to other organic waste water shown in Table 13. The decomposition rate of organic matter in this experiment was 50 to 90%. In other experiments, the decomposition rate was generally 50-90%. The decomposition rate of COD in wastewater with a large molecular weight is low, and there is a tendency for the decomposition rate to increase as the molecular weight decreases.

<Various factory wastewater>
Table 14 summarizes wastewater with complex and unknown components by industry. It was measured.
The ion-exchange resin wastewater is recycled wastewater from the ion-exchange resin in the organic matter refining process. Although the COD decomposition rate is not very high at 69.6%, COD27ppm clears the discharge standard.
Wastewater for electroless plating is obtained by reducing and recovering copper in the wastewater and then subjecting it to an aeration treatment.
Capsule manufacturing wastewater, sugar-coated tablet manufacturing wastewater, and pharmaceutical factory wastewater are all wastewater discharged from pharmaceutical manufacturing processes, although they are produced by different companies. Good results of COD decomposition rate of 80 to 90% have been obtained in the treatment of these wastewaters.
For domestic wastewater, the results of primary treatment and secondary treatment (biological treatment) are shown. Wastewater that has been subjected to biological treatment has a low COD before treatment and a very low COD after treatment. Furthermore, when the method of the present invention was adopted as a tertiary treatment of night soil as part of domestic wastewater, the result was that not only the COD but also the decolorization effect was good.
Food-related wastewater also has a COD treatment rate of 70% or more after biological treatment.

<Dyeing wastewater>
Table 15 shows the results of observing the color of the wastewater by measuring the COD when the dyeing wastewater was combined with the addition of sodium hypochlorite and peroxide and treated for 5 minutes.

<Sodium hypochlorite>
The purpose of this experiment is to decompose sodium hypochlorite as an additive added excessively for carrying out the present invention and sodium hypochlorite added for decolorizing and sterilizing waste water.
Table 16 shows the results of treatment by adding peroxide to the waste water to be treated. Sodium hypochlorite was efficiently decomposed in a short time.

Claims (3)

Adding a solid peroxide containing nickel peroxide as a main component to wastewater containing harmful organic compounds, and increasing the amount of dissolved oxygen in the wastewater and/or adding sodium hypochlorite. A method of decomposing harmful organic compounds in waste water by . 2. The method for decomposing harmful organic compounds according to claim 1, wherein the harmful organic compounds are persistent organic compounds. 4. The method for decomposing harmful organic compounds according to claim 3, wherein the harmful organic compounds are malodorous organic compounds.

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