SU1549926A1 - Method of removing organic compounds from waste water of aniline dye production - Google Patents

Abstract

The invention relates to methods for treating industrial wastewater, in particular wastewater from aniline dye production and dye shops of textile enterprises contaminated with aniline and its derivatives. The purpose of the invention is to simplify the process, increase the degree of purification and ensure the full utilization of ozone while maintaining a high degree of purification of wastewater from aniline. The method includes alkalinization and ozonation at doses of alkali and ozone, respectively, 5-7 g ^. equiv / mol of aniline and 8-9 mol / mol of aniline; carrying out the ozonization process in a two-section countercurrent reactor with an ozone absorption degree of 0.2-0.3 and 0.7-0.8 in the first and second sections of the reactor, respectively. The method eliminates the formation of sediment in the cleaning process, fully utilizes all the ozone fed to the reactor, increases the cleaning efficiency by COD from 67.4% to 91.9%, increases the degree of ozone absorption from 31.4% to 100%, which eliminates the need to neutralize the residual ozone in the exhaust ozone mixture. 3 tab.

Description

The invention relates to methods for treating industrial wastewater having a high concentration of hardly oxidizable organic compounds, in particular, aniline production wastewater and dyeing plants contaminated with aniline and its derivatives.

The purpose of the invention is to simplify the process, increase the degree of purification, ensure full use of ozone while maintaining a high degree of purification from aniline.

The goal is achieved by processing as follows. For

In the process, the wastewater is clarified, if necessary, in a settling tank or on a filter to separate suspended solids present in the original effluent and affecting the ozonation efficiency. An alkali, preferably sodium hydroxide or potassium hydroxide, is then metered into the water in an amount of g eq / mol aniline. Then ozonation is carried out in a two-section reactor. Liquid is fed successively to the first and second sections, and ozone-containing gas, first to the second and then to the first section. The dose of ozone is taken at the rate of 8sl

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The 9 mol / mol aniline, the reactor design and the process mode are chosen such that the degree of ozone absorption is 0.2-0.30 in the first section as the ozone flows, then the remaining 0.70-0.8 ozone is completely absorbed in the second.

When implementing the proposed method, the formation of a sludge containing organic pollutants becomes minimal, the COD purification rate increases, and aniline is destroyed destructively, and is not removed with the sludge, all ozone supplied is completely absorbed and there is no need to deactivate exhaust gas. Achieved cleaning efficiency for aniline and ozone 100%, for COD - at least 90%. The yield of nitrates — the final oxidation product of the amino group — is about 20% of the theoretical value. A further increase in the doses of ozone and alkali is inexpedient, since the cleaning efficiency practically does not increase, reducing the dose of ozone leads to a proportional decrease in the cleaning efficiency of COD, reducing the dose of alkali reduces the cleaning efficiency and causes

em leakage of ozone through the reactor, increasing the dose of alkali necessitates the subsequent neutralization of the residual alkali with acid with a corresponding increase in the salt content of water.

The choice of the ozonation regime was made on the basis of the dependences obtained experimentally with the ozonization of solutions with aniline concentration of 93 mg / l and COD of 200 mg / l.

In order to completely absobose ozone, it is advisable to maintain an alkaline reaction of the medium until the end of ozonation, for which the alkali should be dosed with a small excess (1–2 g equiv / mol). In addition, for complete absorption of ozone, it is necessary to divide the reactor into two sections with countercurrent movement of water and ozone-containing gas in sections 8 of the first section of the reactor section (the second in the direction of water movement), along the gas movement of the section of ozone, should be 0 2-0.3. Then the remaining 0.70–0.8 will be completely absorbed in the next section.

Example 1. Ozonization of solutions with an concentration is carried out.

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lina 1 mmol / l 193 mg / l) and COD 200 mg / l at the ozone dose of otso mg / l and at varying doses of sodium hydroxide in the range of 2-10 g-eq / mol. The alkali dose is chosen close to the minimum, ensuring the absence of leakage (full use) of ozone in a two-section reactor with a maximum reduction in COD (up to 16-18 mg / l).

The results are presented in table 1.

The results presented in table. 1 proves that ozone leakage through the reactor is absent at specific doses of alkali more than 5 gEq / mol of aniline, and COD is reduced to the maximum possible level of 16-18 mg / l (COD efficiency 91-92%) at doses of sodium hydroxide more than 5 eq / mol aniline.

Thus, the specific dose of alkali must be at least 5 g-eq / / mol aniline. However, the residual alkalinity that must be neutralized with acid should be as low as possible. Therefore, the specific dose of alkali is taken by 5–7 g-eq / mol of aniline, while the residual alkalinity does not exceed 1, k-1.5 mg-eq / l.

EXAMPLE 2 The solution is ozonated with an aniline concentration of 1 mg-mol / l (93 mg / l) and a COD of 200 mg / l with a dose of sodium hydroxide of 6 mg eq / / mol and varying the dose of absorbed ozone within mg / l, the dose of ozone is chosen to be minimal, ensuring a reduction in the COD of the solution to the maximum possible level of 16-TI mg / l.

The results show that the COD is reduced to a minimum level of 16–18 mg / l with a dose of absorbed ozone of 38 mg / l (specific dose of 8 mol / mol aniline).

A further increase in the dose of absorbed ozone to 850 mg / l (17.7 mol / mol) is ineffective with respect to COD.

Considering this, the specific dose of ozone must be chosen in the range of 8-9 mol / mol aniline.

The degree of ozone absorption over the reactor sections should be distributed in such a way as to ensure complete absorption of a given ozone dose, i.e. so that the total degree of ozone absorption in the reactor is 1.

-s 15

Experiments show that alkaline solutions of aniline absorb up to 70-75% of the required dose of ozone before the breakthrough. Ozone absorption then continues, but at a much slower rate, as a result of which ozone leakage is observed. Therefore, in the proposed method, it is claimed that ozonation should be carried out in a two-section reactor that is opposite to the liquid and gas. In the first in the direction of movement of the gas section (the second in the direction of movement of the water) a slow absorption stage is realized, at which 0.2-0.3 of the full dose of ozone is absorbed. Then the remaining 0.7-0.8 ozone will be completely absorbed in the second section. An increase in the degree of ozone absorption in the first section leads to unnecessary costs of ozone, a decrease to ozone leakage through the reactor and pollution of the atmosphere.

To confirm this, ozonization of solutions with aniline concentration of 1 mg-mol / l (93 mg / l) and COD of 200 mg / l in a two-section reactor with different distribution of the degree of ozone absorption in sections was carried out (degree of absorption was varied by varying the depth of the liquid layer in the first section of the reactor).

The results are presented in table 2.

Thus, the optimal distribution of the degree of ozone absorption between the reactor sections, ensuring 100% utilization of ozone and the maximum possible COD efficiency, is in the range of 0.2-0.3 and 0.8-0.7.

A comparative evaluation of the known and proposed methods was carried out on a solution containing 200 mg / l (2.15 mmol / l) aniline and having a COD of 30 mg / l. Coagulation, upholding,

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decantation and neutralization, in accordance with a known method, are carried out in glass (20 L) containers. Ozonation is carried out in reactors with a diameter of 0.032 m with a depth of water layer of about 0.3 m with the ozone-air mixture dispersed by a porous glass plate. In the known method, ozonation is carried out in a single-section reactor in three stages, in the proposed one - in a two-section reactor.

The results are presented in table 3.

From the data of Table 3 it follows that the application of the proposed method as compared to the known method allows to significantly simplify the technological scheme, to avoid the formation of sludge containing organic impurities, to increase the cleaning efficiency of COD from 67 to 91.9%, i.e. by 2.5%, and increase the degree of ozone absorption from 31, L to 100%, i.e. by 68.6%. Accordingly, there is no need to neutralize the residual ozone in the spent ozone-air mixture.

Claims (1)

Invention Formula The wastewater treatment method of aniline dye production from organic compounds, including the introduction of alkali and step ozonation, characterized in that, in order to simplify the process, to increase the degree of purification, to ensure full utilization of ozone while maintaining a high degree of purification of wastewater from aniline, the alkali is introduced in the amount of g-eq / mol of aniline, ozone in the amount of 8-9 mol / mol of aniline, and ozonation is carried out by countercurrent in a two-section reactor with an ozone absorption degree of 0.2-0.3 in the first section along the wayVision 0.70-0.80 ozone and the second section. Table 1 there is U1 Not there is Footprints no 39 16.7 17.2 No Traces 1, k I 0.1 on CH00Ј10 0.2 0.25 0.3 0, 0.75 0.8 0.7 0.7 0.7 0.7 0.15 No No Not Not Not Not 17.2 18 17.6 2.3 Table 2 M Not Not ..- .. Examples one Peppiep 32 16-18 16-18 16-18 28 + 12 + 12) Sulfuric Dose acids, g / l 0.52 700 15 992610 , Continued table. 2 five 0 five lina after cleaning, mg / l COD solution after cleaning, mg / l. Process efficiency,%, according to aniline COD ozone N / about 100 67, 31, A N / OSE 35 100 91.9 100