Method for decomposing hazardous organic compounds in wastewater

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]

[0001] The present invention relates to a method for decomposing hazardous organic compounds, particularly persistent hazardous organic compounds, contained in various types of waste liquid. [Background technology]

[0002] Organic compounds contained in various waste liquids are usually treated by oxidative decomposition. However, difficult-to-decompose organic compounds such as 1,4-dioxane contained in groundwater in landfill sites, 1,2-dichloroethane contained in waste sulfuric acid, and dioxins with high toxicity equivalence indexes cannot be decomposed by normal aeration treatment, and require expensive equipment such as a high-temperature decomposition device (Patent Document 1) or an electrolysis device (Patent Document 2). Moreover, in the oxidation treatment at room temperature, an ozone-containing gas is used as the oxidizing gas, and further, an ultraviolet ray irradiation device is required (Patent Document 3).

[0003] Furthermore, odorous components such as methyl mercaptan cannot be completely decomposed by normal aeration treatment, and even trace amounts remaining can become a source of odor. Therefore, in order to completely decompose these components, expensive adsorbents (Patent Document 4) and equipment consisting of multiple steps (Patent Document 5) are required.

[0004] Thus, there has been a demand for the development of a simpler method for decomposing and removing persistent organic compounds and trace amounts of malodorous components contained in waste liquid. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-057923 A [Patent Document 2] JP 2014-014754 A [Patent Document 3] JP 2008-126125 A [Patent Document 4] JP 2018-083170 A [Patent Document 5] JP 2007-319842 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a method for decomposing hazardous organic compounds, such as those which are difficult to decompose or have a bad odor, contained in various types of waste liquid, in a manner that is simpler than conventional methods. [Means for solving the problem]

[0007] The inventors of the present invention have conducted extensive research into methods for dissociating and cleaving the covalent bonds of organic compounds, based on the idea that if the covalent bonds of harmful organic compounds contained in wastewater can be dissociated and cleaved, any difficult-to-decompose organic compounds can be decomposed. As a result, they have found that the covalent bonds of organic compounds in wastewater can be easily dissociated and cleaved by using nickel peroxide as a solid peroxide, increasing the amount of dissolved oxygen in the wastewater, and / or adding sodium hypochlorite, and have arrived at the present invention. According to the inventors' experiments, many organic compounds can be decomposed by using a solid peroxide material mainly composed of nickel peroxide, increasing the amount of dissolved oxygen in the wastewater, or adding sodium hypochlorite, but organic compounds that could not be decomposed by these combinations could also be decomposed by combining nickel peroxide with an increase in the amount of dissolved oxygen in the wastewater and adding sodium hypochlorite.

[0008] The aspects of the present invention are as follows. (1) A method of decomposing hazardous organic compounds in waste liquid by adding a solid peroxide containing nickel peroxide as the main component to the waste liquid containing hazardous organic compounds, and by increasing the amount of dissolved oxygen in the waste liquid and / or adding sodium hypochlorite. (2) A method for decomposing the hazardous organic compounds of (1), wherein the hazardous organic compounds are persistent organic compounds. (3) A method for decomposing the hazardous organic compounds of (1), wherein the hazardous organic compounds are odorous organic compounds.

[0009] In the present invention, "nickel peroxide" refers to nickel sesquioxide or a mixture of nickel sesquioxide and nickel oxide hydrate. Also, "solid peroxide" refers to nickel peroxide, which is mixed with magnesium oxide and alumina silica as solidifying agents, and then solidified and molded.

[0010] In the present invention, in order to increase the amount of dissolved oxygen in waste liquid containing hazardous organic compounds, a well-known aeration device can be used, and any type of aeration device can be used as long as it can aerate air or an oxygen-enriched gas into the waste liquid and increase the amount of dissolved oxygen.

[0011] The solid peroxide material in the present invention is nickel peroxide solidified with magnesium oxide and alumina silica, and the amount of solidifier added is desirably the minimum amount necessary to achieve the strength required for the use of the solid peroxide material. In addition, by blending inorganic fiber materials such as glass fiber, the strength of the solid peroxide material is improved, so that the amount of solidifier used can be reduced.

[0012] The mechanism of dissociation and cleavage of the covalent bonds of hazardous organic compounds assumed in this invention is explained using the schematic diagram in Figure 1. (1) shows the state in which 1,4 dioxane, sodium hypochlorite, and a solid peroxidizing agent are present in water. As shown in the figure, sodium hypochlorite comes into contact with the solid peroxidizing agent. (2) shows the sodium hypochlorite coming into contact with the solid peroxidizing agent decomposing to generate nascent oxygen, which then attacks the covalent bond of 1,4 dioxane. (3) shows the state in which the covalent bond of 1,4 dioxane attacked by the nascent oxygen has been dissociated and cleaved.

[0013] Instead of sodium hypochlorite, hydrogen peroxide, chlorine oxides other than sodium hypochlorite, permanganates, and chromates can release active oxygen, but nickel peroxide is also reduced and the reduced nickel hydroxide cannot be converted to peroxide.On the other hand, acidic oxidizing agents such as chlorine water, chlorine cyanuric acid, and persulfates can oxidize nickel hydroxide to peroxide, but cannot generate active oxygen.

[0014] Nickel peroxide is preferably mixed with a solidifying agent, molded, filled into a filling tank, and then brought into contact with waste liquid to which sodium hypochlorite has been added. Since sodium hypochlorite may cause a chlorine addition reaction with the oxidized material over time, it is preferable to add it to the waste liquid just before the reaction tank.

[0015] Since there is a slight time lag between when sodium hypochlorite is added and when it completely decomposes and generates all the oxygen that is being generated, it is desirable to control the amount of sodium hypochlorite added according to the fluctuation of the COD of the wastewater. Also, if the "multi-stage addition method" is used, in which the amount of oxygen compound solution added is gradually decreased according to the decrease in COD, it is advantageous because the amount of oxygen compound solution used can be reduced.

[0016] Furthermore, if too much time is required before the wastewater is treated after mixing the sodium hypochlorite solution with the wastewater, side reactions other than oxidation, such as a chlorine addition reaction with the oxidized material, may occur, which may make the oxidation reaction difficult, so it is preferable to add the sodium hypochlorite solution before the wastewater is introduced into a reaction tank or reactor. Also, if the wastewater contains oxidized materials such as amine salts that are particularly prone to chlorine addition reactions, it is preferable to add caustic soda to the wastewater together with the oxygen compound solution, or before or after the addition of the oxygen compound solution, to prevent the chlorine addition reaction. Effect of the Invention

[0017] According to the method of the present invention, it is possible to decompose persistent 1,4-dioxane, 1,2-dichloroethane, or dioxins in a comparatively short time, and it is possible to reduce odorous components such as methyl mercaptan produced in oil refineries to an odor index of 9 or less (undetectable by the human sense of smell) in as little as two hours, and it is also possible to decompose odorous components in nitrogen liquid generated by biomass power generation facilities in a short time. [Brief description of the drawings]

[0018] [Figure 1] Schematic diagram of the cleavage of the covalent bond of an organic compound by the method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Examples of the present invention will be described below, but the present invention is not limited thereto. EXAMPLES

[0020] <Production of solid oxide materials 1> Glass fibers with a length of about 3 to 5 mm, which have been previously treated with sulfuric acid and potassium permanganate to remove organic matter, are added to a nickel salt solution such as nickel sulfate, nickel nitrate, or nickel chloride at a concentration of about 10 to 25%, with about 10 to 30 wt% of the nickel content, and then a 19 to 25% caustic soda solution is used to convert the nickel content to nickel hydroxide (Ni(OH)2), and then a sodium hypochlorite solution sufficient to convert this to Ni(OH)3 is added at 30°C or less. Next, the glass fibers are washed and filtered to make a cake with a moisture content of 35 to 45%, and magnesium oxide or alumina silica with a content of 25 to 50% of the nickel content is added and kneaded as a solidifying agent, and the cake is molded into an appropriate shape to make a peroxide material. The size of this molded product can be determined appropriately depending on the capacity of the processing device, etc., and the length of the glass fibers can be determined depending on the size. The molded product is left to stand for 1 to 2 days and then dried at 40°C. EXAMPLES

[0021] When nickel oxide (NiO) is added with sodium hypochlorite (NaClO) to produce the peroxides Ni2O3 and Ni3O4, if some nickel peroxide is mixed with the nickel oxide and then treated with sodium hypochlorite, the conversion to peroxides can be completed in a shorter time. By repeatedly adding nickel oxide to the nickel peroxide produced and treating it with sodium hypochlorite, a large amount of nickel peroxide can be produced in a short time. To 100 parts by weight of the 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 were added and mixed and kneaded, and then the mixture was granulated to about 6 mm in diameter and air-dried for 24 hours to obtain an oxidizing agent. EXAMPLES

[0022] <Decomposition of 1,2-dichloroethane in waste sulfuric acid by aeration and oxidation> [Test 1] 10 liters of normal waste sulfuric acid was aerated by blowing in 7 liters of air per minute for 144 hours. [Test 2] 10 liters of waste sulfuric acid containing acetic acid was aerated by blowing in 7 liters of air per minute for 240 hours. The aeration device used in this experiment was manufactured by AMS Engineering (CATH-F). The results of measuring the amount of 1,2-dichloroethane in the wastewater 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 standard value by aeration alone, but by combining it with a peroxidizing agent such as nickel peroxide according to the method of the present invention, the amount can be dramatically reduced.

[0023] [Table 1] EXAMPLES

[0024] <Decomposition of 1,4-dioxane in leachate by aeration, peroxide and sodium hypochlorite> [Test 1] 6.0 L of underground leachate containing 1,4-dioxane was aerated with air at 3.75 L / min for 1 hour. [Test 2] 200 g of nickel peroxide was added to 6.0 L of underground leachate containing 1,4-dioxane, and the mixture was aerated with 3.75 L / min of air for 1 hour. [Test 3] 200 g of nickel peroxide and 300 cc of sodium hypochlorite were added to 6.0 L of underground leachate containing 1,4-dioxane, and the mixture was aerated with 3.75 L of air per minute for 1 hour. Aeration device used (AMS Engineering, CATH-F) 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, aeration alone, or a combination of aeration and peroxidation material, was unable to decompose 1,4-dioxane, but by further combining it with sodium hypochlorite, the amount of 1,4-dioxane in the leachate was dramatically reduced.

[0025] [Table 2] EXAMPLES

[0026] <Oxidative decomposition of organic compounds by combining various oxidizing materials with nickel peroxide> The organic compounds used were 0.25% ethyl alcohol and 0.25% triethanolamine. The results of treatment with (1) sodium hypochlorite solution, (2) nickel peroxide, and (3) sodium hypochlorite solution and nickel peroxide were as follows: (1) When an excess amount of sodium hypochlorite solution was added to 0.25% ethyl alcohol and 0.25% triethanolamine, after two hours, 48% of the ethyl alcohol was decomposed and 39% of the triethanolamine was decomposed. (2) When a similar test was conducted using nickel peroxide instead of sodium hypochlorite solution, about 90% of the ethyl alcohol and triethanolamine were decomposed after two hours. However, the procedure was complicated because it was necessary to regenerate the reduced nickel peroxide. (3) In accordance with the present invention, when an excess amount of sodium hypochlorite solution was added to ethyl alcohol and triethanolamine, and then nickel peroxide was added, 93% of the ethyl alcohol was decomposed after 15 minutes, and 96% of the triethanolamine was decomposed after 45 minutes. In addition, nickel peroxide did not need to be regenerated because it only functioned as a catalyst. EXAMPLES

[0027] <Decomposition of odorous components using methyl mercaptan stock solution> A 50L reaction tank was prepared, and 9 kg of methyl mercaptan stock solution was added to the tank, followed by 450 g of peroxide material whose main component is nickel peroxide. The tank was heated by running hot water through the jacket, and the temperature inside the tank was adjusted to 40-45°C. In this state, the reaction tank was aerated at 7.50 L / min, and the odor, temperature, DO, OPR, and pH were measured after 30, 60, 90, and 150 minutes. The measurement results are shown in Table 3. The "Odor (human)" evaluation is the result of a sensory test based on the following criteria: strong: strong odor, medium: odor that can be easily detected, slight: odor that can be barely detected, none: odor that cannot be detected. The "Odor Index" is defined as the logarithm of the dilution ratio when a substance is diluted with odorless air until the odor can no longer be detected, multiplied by 10.

[0028] [Table 3]

[0029] As can be seen in Table 3, the odor decreased between 30 and 60 minutes, and was virtually odorless between 90 and 150 minutes. When humans smell an odor, the way they perceive the odor changes depending on the shape of the odor-generating liquid container, and measurements using an odor sensor also change even if the measuring part is slightly misaligned, so there was some variation in the above measured values, but if the ORP (oxidation-reduction potential) is below -550mv, humans will no longer be able to detect the odor.

[0030] Furthermore, experiments were conducted using waste liquid with a strong odor in which the amount of peroxide added and the amount of aeration were changed. Two 50-liter reaction tanks were prepared, and 9 liters of methyl mercaptan waste liquid was added to each tank, followed by a specified amount of a peroxidizing agent whose main component is nickel peroxide. In this state, each tank was aerated with a specified amount of air for 90 minutes, and the odor index was measured before and after treatment. The measurement results are shown in Table 4. Similar results were obtained with waste liquid (2), in which the amount of aeration was reduced, and with waste liquid (3), in which the amount of peroxidizing agent added and the amount of aeration were increased, the odorous components were almost completely decomposed.

[0031] [Table 4] EXAMPLES

[0032] <Decomposition of odorous components in amino acid waste liquid> An aeration device was operated to aerate 900cc of amino acid waste liquid at 3.75L / min. After 2 hours, there was no change in the strong odor peculiar to amino acids, so 90g (10%) of the peroxidizing agent of the present invention and 45cc (5%) of sodium hypochlorite were added and aeration was continued. Aeration device used (AMS Engineering, CATH-F) The pungent odor disappeared 18 hours after the start of aeration, and after 24 hours the odor had decreased to the point where it was only faintly detectable. EXAMPLES

[0033] <Decomposition of odorous components in ammonia waste liquid> To 900 cc of ammonia waste liquid, 90 g (10%) of the peroxidizing agent of the present invention and 45 cc (5%) of sodium hypochlorite were added while aeration was performed at 3.75 L / min by operating an aeration device. Aeration device used (AMS Engineering, CATH-F) Two hours after the start of aeration, the odor was no longer detectable, and the aeration was stopped 15 hours and 30 minutes after it began. EXAMPLES

[0034] <Decomposition of odorous components in shellfish sludge> Mussels that grow and attach to the cooling water passages of power plants are regularly removed, but the shellfish that are removed soon emit a strong odor. These types of odors are: Ammonia: 10~1000ppm Hydrogen sulfide: 0.05~4.0ppm Methyl mercaptan: 0.1~8.0ppm (Equipment used: Gastec gas detector tube type gas measuring device GV-100S) The collected shells were crushed with shells together to about 10-15 mm diameter, and 2 kg was placed into each of three 20 L containers (A, B, C). 10 L of purified water was added, and a specified amount of peroxide and sodium hypochlorite was added to each container. The container was aerated for 30 minutes at an air volume of 3.75 L / min. The odorous components in the shell sludge were reduced to less than 50 ppm for ammonia, less than 1.0 ppm for hydrogen sulfide, and less than 1.0 ppm for methyl mercaptan. Aeration device used (AMS Engineering, CATH-F) 2 kg of fresh shellfish sludge was added to one of the containers after the aeration treatment, and the container was aerated for 30 minutes at an air volume of 3.75 l / min. This container was designated as container D. The odorous components in the shellfish sludge before and after aeration in vessels A to D are as shown in Table 5 below, and the odor was dramatically reduced in all cases.

[0035] [Table 5] EXAMPLES

[0036] <Comparison between sodium hypochlorite alone and in combination with peroxide> The change in COD over time was investigated for the organic compounds shown in Table 6 when sodium hypochlorite was added alone and when sodium hypochlorite was added in combination with a peroxide agent. The results are shown in Table 6. When sodium hypochlorite was used alone, the concentration only decreased by about 30% even after 2 hours, but when sodium hypochlorite and a peroxide were added in combination, the concentration decreased by about 90% in the short period of 10 to 20 minutes.

[0037] [Table 6] EXAMPLES

[0038] <Inorganic wastewater> When a prescribed amount of sodium hypochlorite was added to the inorganic wastewater shown in Table 7 and the change in COD over time was measured, all wastewater showed a treatment rate of 70 to 100% in a short time of less than 15 minutes. In particular, most sodium nitrite wastewater was treated nearly 100% with the theoretical amount of COD added and in a short time of about 10 minutes. Furthermore, cyanide-containing wastewater can be treated at a higher level, from low to high concentrations. Thus, it was found that sodium hypochlorite alone is sufficient for inorganic wastewater treatment.

[0039] [Table 7] EXAMPLES

[0040] <Alcohol wastewater> When the change in COD over time was measured when sodium hypochlorite and a peroxidizing agent were added to the alcohol wastewater shown in Table 8, all wastewater showed a treatment rate of 85 to 99% in a short period of time within 10 to 30 minutes. In particular, the decomposition rate of isopropyl alcohol-containing wastewater varies somewhat depending on the conditions, but decomposition of 90% or more is possible, but the consumption of additives required was about four times the theoretical COD value. In addition, ethylene glycol-containing wastewater could be treated with a decomposition rate of 85 to 90% at about twice the theoretical COD amount. Thus, it can be seen that alcohol wastewater can be sufficiently treated by the combined treatment of the present invention.

[0041] [Table 8] EXAMPLES

[0042] <Phenol wastewater> The changes over time in COD and phenol concentration were measured when sodium hypochlorite and a peroxidizing agent were added to the phenolic wastewater shown in Table 9, and air aeration was combined. In the case of phenolic wastewater, COD treatment and phenol treatment are necessary, and treatment must be performed according to the purpose. Phenol decomposition is nearly 100% possible with an additive equal to or greater than the theoretical COD amount, and in the case of COD, the decomposition rate is 90% with an additive equal to the theoretical COD amount, but the decomposition rate drops sharply if more is added.

[0043] [Table 9] EXAMPLES

[0044] <Aldehyde wastewater> When the change in COD over time was measured when sodium hypochlorite and a peroxidizer were added to the aldehyde-containing wastewater shown in Table 10, it was found that adding about twice the amount of additive from the theoretical amount of COD was enough to treat about 95% of the COD.

[0045] [Table 10] EXAMPLES

[0046] <Organic acid wastewater> When the change in COD over time was measured when the organic acid wastewater shown in Table 11 was treated with a combination of sodium hypochlorite and a peroxidizing agent, it was found that for sodium citrate and sodium stearate, more than 90% of the COD could be treated by adding an additive equivalent to the theoretical COD amount, but for acetate compounds, an additive equivalent to about 5 to 10 times the theoretical COD amount was required.

[0047] [Table 11] EXAMPLES

[0048] <Amine wastewater> The change in COD over time was measured when hypochlorous acid and peroxidizing agents were added to the amine-based wastewater shown in Table 12. Since amine-based compounds can decompose 70-90% of COD by reacting with additives in an alkaline environment, all experiments were performed in an alkaline environment. For wastewater containing triethanolamine, additives were used in an amount 2 to 4 times the theoretical COD amount, and the decomposition rate was about 70% after a reaction time of 15 minutes. For wastewater containing secondary fatty acid amines, the reaction time was set at 30 minutes, and more than 80% decomposition was achieved using additives in the theoretical COD amount.

[0049] [Table 12] EXAMPLES

[0050] <Other organic wastewater> The change in COD over time was measured when sodium hypochlorite and a peroxidizing agent were added to other organic wastewater 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 to 90%, but when looking at the treatment results of wastewater where the contents of the main components of the wastewater are known, such as in Examples 11 to 17, the decomposition rate of COD of wastewater with a large molecular weight of organic matter is low, and the decomposition rate tends to be higher for organic matter with a smaller molecular weight.

[0051] [Table 13] EXAMPLES

[0052] <Various factory wastewater> Table 14 shows wastewater containing complex and unknown components, grouped by industry. The change in COD over time was measured when sodium hypochlorite and a peroxidizing agent were added to these organic wastewater. Ion exchange resin wastewater is regenerated wastewater from ion exchange resin in the organic matter refining process. The COD decomposition rate is not very high at 69.6%, but COD of 27 ppm meets the discharge standard. The wastewater from electroless plating was treated by aeration after copper was reduced and recovered. Although the wastewater from capsule manufacturing, sugar-coated tablet manufacturing, and pharmaceutical factory wastewater are from different companies, they are all wastewater discharged from the pharmaceutical manufacturing process. In the treatment of these wastewaters, good results have been obtained with a COD decomposition rate of 80-90%. For domestic wastewater, the results of primary treatment and secondary treatment (biological treatment) are shown. The wastewater that underwent biological treatment had a low COD before treatment and a very low COD after treatment, and it is considered economical to treat wastewater with this level of COD. Furthermore, when the method of the present invention was used as a tertiary treatment for human wastewater, the results showed that not only was the COD low, but the decolorization effect was also good. Food-related wastewater also has a COD treatment rate of 70% or more if it is subjected to biological treatment, but when the treatment of the present invention is applied as a secondary treatment, the effect is not so good.

[0053] [Table 14] EXAMPLES

[0054] <Dyeing wastewater> Sodium hypochlorite and a peroxide were added to dyeing wastewater and treated for 5 minutes. The COD was measured and the color of the wastewater was observed. The results are shown in Table 15.

[0055] [Table 15] EXAMPLES

[0056] <Sodium hypochlorite> The purpose of this experiment was to decompose sodium hypochlorite added in excess as an additive for implementing the present invention, and sodium hypochlorite added for decolorizing and sterilizing wastewater. Peroxide was added to the wastewater to be treated, and the results are shown in Table 16. Sodium hypochlorite was decomposed efficiently in a short time.

[0057] [Table 16]

Claims

1. A method for decomposing hazardous organic compounds in wastewater by using an aeration device (CATH-F) manufactured by Ams Engineering to aerate air or oxygen-enriched gas into wastewater containing hazardous organic compounds for more than 30 minutes to increase the amount of dissolved oxygen in the wastewater, adding sodium hypochlorite, and contacting the wastewater with a solid peroxide formed by adding magnesium oxide and alumina silica to nickel peroxide.

2. 2. The method for decomposing hazardous organic compounds according to claim 1, wherein the hazardous organic compounds are difficult-to-decompose organic compounds.

3. 3. The method for decomposing hazardous organic compounds according to claim 2, wherein the hazardous organic compounds are malodorous organic compounds.

Images