JPS6017595B2 - Treatment method for wastewater containing oxidizable substances - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention purifies oxidizable substances in wastewater containing oxidizable substances, particularly photographic wastewater, such as developer and fixer liquids, paint wastewater, and dyeing wastewater, by oxidizing and decomposing them. , its high COD
The object of the present invention is to provide a new treatment method that can easily remove components having a chemical oxygen demand.

In recent years, the COD value has been set as a pollution prevention target under the total water quality control, and the discharge regulations have become increasingly strict, making it urgent to sufficiently remove the COD value.

Conventionally, methods for purifying wastewater containing oxidizable substances include thermal oxidation decomposition using hypochlorite and electrolysis when the concentration of oxidizable substances is high; , sufficient decomposition and removal is difficult, and in the case of low concentrations, methods using inorganic synthetic adsorbents, activated carbon adsorption methods, biological treatment methods, pus decomposition methods, oxidation methods (ozone, hydrogen peroxide, chlorine, ultraviolet rays, Ultrasonic waves, etc. alone or in combination) are being used, but these methods are difficult to apply, especially for wastewater containing COD values with inconsistent concentrations, and currently they are discharged as is or after dilution. . For example, the use of X-ray photography in medical institutions has increased significantly, and these photographic wastewaters contain a developer and a fixer. It contains diamine derivatives, phenol or naphthol derivatives, sulfites, alkalis, formaldehyde, hydroxylamine salts, etc., and has a COD value ranging from tens of thousands to 100,000, and the fixing solution contains thiosulfate as well as the main ingredient. It contains sulfite, acetic acid, boric acid, and alum, has a COD value of tens of thousands of feet, and contains several thousand feet of silver ions.

In addition, depending on the type of dye, for example, monoazo-based, anthraquinone-based, phthalocyanine-based dyes, etc. are used in dyeing wastewater, and in addition, neutralizing agents, detergents, softeners, scouring agents, bleaching agents, etc. are used in each process, resulting in a very complex composition. It is a mixed wastewater.

Furthermore, when dyeing wool with chromium, hexavalent chromium may be present in the wastewater, and the COD value can be as high as 3000, making treatment difficult as it must be treated in conjunction with bleaching. This is one of the major types of wastewater. Furthermore, paint wastewater includes manufacturing wastewater from oil-based paints, alcoholic paints, cellulose paints, synthetic resin paints, water-based paints, etc., depending on the raw material, but water-soluble water-based paints are particularly problematic, and their COD values are over 2,700 traces. It also becomes.

In this way, the COD value in wastewater is due to the presence of oxidizable monsters, which can be oxidized and decomposed using a certain type of oxidizing agent, but the type and amount of oxidizing agent depends on the type and content of the oxidizable substance. In particular, oxidizable substances in photographic simulated liquids and disinfectant waste liquids are extremely difficult to oxidize, and usually contain large amounts of substances, and the amount is not constant.

A mixture of ferrous salt and hydrogen peroxide has been known as Fento since ancient times.
n reagent ((Tmns Fardey SM., 47.4
62 (1951) and 47.591 (1951).

)) is known as a strong oxidizing agent, but in order to oxidize wastewater containing highly concentrated oxidizable substances, the amount of ferrous salt and hydrogen peroxide required depends on the concentration of COD value. A high degree of removal must require large amounts of reagents and fairly long processing times. Therefore, in wastewater treatment that requires advanced treatment, using these reagents in units has disadvantages such as inefficiency and slow reaction rate, so as a countermeasure, copper ions and ferrous ions are used as catalysts. Methods to promote oxidative decomposition reactions have also been proposed, but
When ferrous ions are added to hydrogen peroxide, it is difficult to process a large amount due to the risk of explosion due to reaction heat, and it is extremely difficult to control steel ions as well.

In order to determine the amount of ferrous ions to be added, it is necessary to know the COD value in the wastewater in advance, which becomes even more difficult in continuous treatment. The present invention solves the above-mentioned problems with conventional wastewater treatment technology that uses hydrogen peroxide and wastewater treatment technology that uses hydrogen peroxide and ferrous ions or transition metal ions. The present invention provides an innovative wastewater treatment method that can remove oxidizable substances by oxidative decomposition and simultaneously remove contained metal ions such as silver and hexavalent chromium.

That is, in the present invention, after preparing a base of wastewater containing oxidizable substances, adding steel-coated iron powder as a catalyst and extinguishing it, hydrogen peroxide is continuously added to carry out oxidative decomposition, and after the reaction is completed, This is a method in which an alkaline agent is added to raise the pH to 8 or higher to form a precipitate, followed by over-separation in a furnace.

The feature of the present invention lies in the use of copper-coated iron powder as a catalyst, which allows the reaction of the iron powder to be controlled and the copper to be controlled at the same time.

In this case, the rate of the reaction depends on the proportion of the copper film on the surface of the iron powder, and the grain size or surface area of the iron powder has a large effect on the processing efficiency, and the amount of hydrogen peroxide solution can be reduced depending on the amount of copper added. In addition, for low-concentration wastewater, the iron powder remains undissolved even after the reaction is complete, so less alkaline agent is required, and it also acts as a settling aid and has excellent furnace filtration properties. ing. Regarding the copper-coated iron powder used in the present invention, as a result of coating various iron powders with different proportions of copper and performing drainage treatment, the iron powder was 1200heah
A low-density iron content of 60% or more is good, and steel-coated iron powder obtained by coating this with about 10% copper showed particularly good results in the entire concentration range of the waste liquid.

The method of treating wastewater containing oxidized metal by adding ferrous ions, metallic iron, copper ions, or metallic steel is known, but the steel-coated iron powder used in the present invention is fixed on the surface of the special iron powder. They are coated with a certain amount of copper, and have very advantageous effects depending on the amount of catalyst added and the reaction.

The present invention will be described in further detail below.

To explain the oxidative decomposition removal mechanism of oxidizable substances in the present invention, the pH of wastewater containing oxidizable substances is adjusted to 2 to 5 (
Preferably, after adjusting to 2 to 3), when steel-coated iron powder is added, copper is preferentially dissolved first, then iron powder is dissolved, and ferrous ions are present.

When copper ions and iron powder remain, the following reaction occurs due to the difference in ionization head direction.

Cze+10Fe→Fe210Cu ・
...'1 - This reaction is very fast; steel ions are reduced to metallic copper, and iron is eluted as ferrous ions.

Next, by adding hydrogen peroxide solution (Japanese 2Q), reaction formula '1
Hydroxyl radicals (OH'), which are strong oxidants, are generated by reacting with the ferrous ions generated from '. Fe2
10 is 02 → Fe3 10 OH + OH'...■
Fe3 Jujugo 02 → Fe2 Juju H02' Jukkaju
...'3' Reaction formula '21 above is a very distant reaction, but reaction formula '3' is a slow reaction at the rate-determining step.

Furthermore, when hydrogen peroxide and ferrous salt coexist, the following reaction occurs simultaneously. Fe210OH→Fe310OH'
...'4' day 2020 OH → day 2
010 days 02...(51Fe210 days ○→Fe310 days 02'...'6}F
e3 10th day 02 → Fe2 10th day 02 10th day
...{7' The above reaction is expressed by reaction formula '61 when the ratio of hydrogen peroxide to ferrous ions is small and the 4-shelf is dominant, and when the ratio of hydrogen peroxide to ferrous ions is large {7}
becomes dominant.

In the method of the present invention, as shown in reaction formula {1', ferrous ions are gradually dissolved, and copper ions replace and cover the surface of the iron powder as metal steel, so side 7 in the reaction formula is dominant. It is. The eluted ferrous ions are oxidized to ferric ions as shown in leg 6' of the reaction equation, but the oxidized ferric ions oxidize metallic copper to produce copper ions as well as ferrous ions. arise.

Cu+ is he30→Cu2102Fe20
...■ In this way, when copper ions coexist, a cycle occurs in the reaction, which cancels out the finite phase of the reaction formula, further improving efficiency.

Furthermore, even in the coexistence of ferrous ions and metallic copper, copper is eluted by the ferric ions and hydrogen peroxide produced according to reaction formula (1), and copper ions are produced, so that the above-mentioned cyclic reaction occurs. In addition, in addition to the above-mentioned reaction, when iron powder is dissolved as ions, the oxidizing force due to hydrogen in the generator is stronger than the reducing force due to ferrous ions, and the hexavalent chromium is cyclized into three pieces, and there are also ions. Even in the case where the iron powder is present, silver ions can be easily substituted and removed as metal by the presence of iron powder.

In addition to the above reaction cycle, hydrogen peroxide reacts alone and oxidizes other ions in the wastewater, but the catalyst works efficiently and is necessary in that it automatically preferentially dissolves copper. By adding an antifoaming agent such as a silicone emulsion, heat generation and foaming can be prevented, and cresol soap solutions and the like can be safely processed.

Further, the features of the present invention are that, compared to the conventional method of adding steel ions and ferrous ions, there is no accumulation of salts, the consumption of alkaline agents and the amount of precipitation is small, and iron powder By adding the unique reaction of increasing the pH due to the dissolution of the alkali agent, the amount of alkaline agent can be further saved.

At the end of the reaction, dissolution of iron stops, and excess iron remains in the solution as metallic iron without being dissolved.

This speeds up coagulation and sedimentation in the post-treatment process, and also serves as a furnace filter aid, reducing treatment time. There is also a method of adding metal steel and metal iron in the form of thin plates, lines, or particles as catalysts, but the reaction is inconsistent and it is surprising that the amount of copper is controlled.In the present invention, the surface area of the powder is Because we use large, low-density steel-coated iron powder, we can control the amount of copper relative to iron, allowing the reaction between copper and iron to proceed in a cyclical manner, and allowing the reaction to occur over a long distance.

When an oxidizable substance is oxidized and decomposed by hydrogen peroxide and ferrous ions, hydroxyl radicals, which are strong oxidizing agents, are generated, and as mentioned above, a large amount of oxidation reaction heat is generated. In some cases, reaction heat is not generated and oxidative decomposition does not occur, so in order to treat these scale liquids as necessary, the liquid temperature is raised to 30° C. or higher to allow the reaction to proceed naturally.

The present invention oxidizes and decomposes oxidizable substances contained in photographic waste liquid, dye waste liquid, and paint waste liquid through the above reaction, and the COD
It is a highly efficient treatment method that can reduce the value below the regulatory value and also easily recover heavy metals contained in the waste liquid at the same time.

Next, the processing steps of the present invention will be explained.

'11 Adjust the pH of the oxidizable substance-containing wastewater to 2 to 5.
Figure I shows the relationship between the initial solution of drainage and the residual COD value.

This figure shows that sulfuric acid is added to the dyeing wastewater and developer solution, the bait (initial solution) for each solution is set at several points between 1 and 6, and then the solution temperature is heated to 30 to 40°C. After overflowing, steel coated iron powder and hydrogen peroxide were added and mixed, an alkali agent was added to adjust the pH to 8 or higher, and a coagulant was added to perform coagulation separation. What can be seen from these results is that the initial stage differs slightly depending on the type of wastewater, but in the case of dyed wastewater, Bait 2 shows good results, and higher or lower bait settings result in higher COD values. In the case of a developer, the addition of hydrogen peroxide decomposes the shoe and lowers the quality of the shoes, but it is still preferable to set the initial setting to 2 to 5. Therefore, in the present invention, the initial axis adjustment is set to 2 to 5 using key acid, but preferably 2 to 3.
shall be.

■ Next, low-density steel coated iron powder is added and polished to preferentially remove copper.

At this time, if necessary, increase the liquid temperature to 30°C or higher and add an antifoaming agent. '3} Next, hydrogen peroxide is continuously added to allow the oxidative decomposition reaction to proceed. '4} After a certain period of time, add an alkaline agent to adjust the pH to 8 or higher.

As the alkaline agent, caustic soda or slaked lime, or a mixture thereof, preferably slaked lime in the form of milk, is added to improve treatment efficiency and accelerate aggregation. '51 After simmering for a certain period of time, a polymer flocculant is added to cause flocculation, the thickening is stopped, and after sedimentation, over-separation is performed in the furnace. These series of operations can be performed automatically using continuous or batch-type equipment. It will be done.

Next, the present invention will be further clarified using Examples and Comparative Examples.

Example 1 A 2.3% diluted photographic developer waste water was treated as raw water.

Take 200 g of raw water in a beaker, add it to 3 ml, add sulfuric acid to make 5 ml of water, and add 0.0 ml of coachron while thoroughly stirring the neck. Added chicks. Next, 35% weekly hydrogen oxide solution was added using a pump at a rate of 3M/min for 10 minutes, followed by kojihai for 2 minutes. Then add slaked lime to increase the pH
Table 1 shows the results of analysis of the furnace liquid obtained by adding a flocculant to flocculate and separate the flocculant and filtering it through the furnace. Table 1 (Unit material Z) Example 2 Drainage from the dyeing process (including process water from scouring and finishing)
) was provided for the purpose of decolorization and COD removal.

The stock solution has a dark blue color and a COD of approximately 250 females/sleeve.

After adding 1 volume of sulfuric acid to this stock solution, adjusting the pH to 2.5 and heating (30 to 40°C), 0.0% of copper-coated iron powder (Cortatiron) was added. Add batter, add 35% hydrogen peroxide solution and boil for 13 minutes. After that, the iron in the liquid was oxidized with slaked lime, and the iron in the liquid was precipitated by adding a flocculant.The lachrymal fluid was decolored and the COO value decreased. The results are shown in Table 2. 0 Table 2 (Units/Z) Example 3 Painting waste water (COD value 2750 o/Z) was treated as raw water by the method of the present invention.

Take raw water IZ in a beaker and add sulfuric acid to it to adjust the pH.
2, and then copper-coated iron powder was added while sufficiently crossing the ocean. Next, 35% hydrogen peroxide solution was added continuously, then slaked lime was added to make pHIO, and after 19 minutes of stirring, the mixture was flocculated and separated, and this was filtered through the furnace.The results of analysis of the furnace liquid are shown in Table 3. . Table 3 (units/and)

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between initial pH and residual COD value in various wastewater treatments. Figure 1

Claims (1)

[Claims] 1. When subjecting photographic wastewater to oxidative decomposition treatment, the pH of the wastewater is first adjusted to 2 to 5, then copper-coated iron powder and hydrogen peroxide are added, and then an alkaline agent is added to adjust the pH to 8. A method for treating wastewater containing oxidizable substances, which comprises making the above adjustments, adding a coagulant, and performing coagulation separation. 2. When oxidizing and decomposing dyeing process wastewater, first adjust the pH of the wastewater to 2 to 5, then add copper-coated iron powder and hydrogen peroxide, then add an alkaline agent to adjust the pH to 8 or higher, A method for treating wastewater containing oxidizable substances, characterized by adding a coagulant and performing coagulation separation. 3. When oxidizing and decomposing paint wastewater, first adjust the pH of the wastewater to 2 to 5, then add copper-coated iron powder and hydrogen peroxide, then add an alkaline agent to adjust the pH to 8 or higher, and then coagulate. A method for treating wastewater containing oxidizable substances, the method comprising adding an agent to perform coagulation separation.