CS254613B1 - Method of detoxification and pretreatment of wastewater from the production of amino resins - Google Patents

Abstract

The purpose of the solution is to obtain such wastewater that can be easily further treated in biological treatment plants or disposed of in another way. This is achieved by detoxifying and pre-treating wastewater containing formaldehyde, butanol and/or isobutanol, resin residues and possibly methanol, while regenerating the alcohols present. An alkalizing agent is added to the wastewater at an elevated temperature, whereby formaldehyde is converted into non-toxic and biodegradable formose by aldolization, and the water thus treated is subjected to either azeotropic distillation or, in the presence of methanol, distillation at a pressure of 13 to 101.3 kPa, where after distilling off 30 to 70% of the wastewater volume, the distillate is subjected to rectification with possible azeotropic dewatering of the butanol and/or isobutanol fraction.

Description

The present invention relates to a novel process for detoxifying and pretreating waste water from the production of lacquer amino resins to such a degree that the waste water is suitable for biological treatment while obtaining the alcohols contained in the waste water.

Waste waters from the production of lacquer amino resins, i.e. urea or melamine condensates with formaldehyde or paraformaldehyde, partially etherified with aliphatic alcohols, contain, in addition to the resin residues, formaldehyde, etherification alcohol, most often butanol or isobutanol, stabilizes. This mixture of substances cannot be distilled off directly, since formaldehyde passes into all distillation fractions non-quantitatively. In the treatment of these waste waters in biological treatment plants, the biocenosis (activated sludge) is formalized with formaldehyde, as well as in the presence of alcohols contained in these waters during the biocenosis incineration, the loss of the alcohols present.

The problem of waste water treatment from the production of lacquer amino resins thus involves two basic problems. Firstly, the disposal of formaldehyde and secondly the recovery of solvents. Formaldehyde from wastewater is most often removed by physico-chemical processes. Catalytic oxidation with hydrogen peroxide in the presence of iron metal, iron salt, alkali metal salts and soils and platinum is known (Japanese Pat. Nos. 72,044,906, 81,111,085, 820,024,694, Soviet AO No. 552,309, U.S. Pat. Nos. 2,703,267 and 2,703,268). Also known is a process of catalytic oxidation with hypochlorite in the presence of nickel oxide on a polyvinyl chloride support (Japanese Pat. No. 80,027,075).

Liquidation resp. the use of formaldehyde from the mother liquors which are lost in the production of 1,5-methano-3,4-dinitrozo-1,3,5,7-tetraazocyclooctane is dealt with by several MS. No. 185 888, 196 707, 214 605, which deals with the distillation of formaldehyde. However, this method cannot be used in the presence of methanol and other alcohols. Furthermore, it is known from the literature that waste water contaminated with formaldehyde can be treated with adapted activated sludge at a concentration of 200 to 2000 mg.l ³ , whereas the adapted activated sludge is already toxic to formaldehyde at a concentration of 200 mg.l ¹ . While wastewater from the production of lacquer amino resins may contain an even higher concentration of formaldehyde than 2000 mg.l, this method cannot be used. Methods for destroying formaldehyde by reaction with ammonia or ammonium salts to form hexamethylenetetramine (urotropin) are also known. However, it is slightly toxic, poorly biodegradable and undergoes hydrolysis in aqueous solutions to form formaldehyde and the corresponding salt (Walder J .: Formaldehyde, Reinold publ. Corp., New York 1964).

The reaction with urea in an acidic environment results in the formaldehyde contained in the waste water being a urea-formaldehyde condensate useful as a fertilizer, for example, as described in Czechoslovakian author's certificate No. 234,590. A disadvantage of this procedure is that the condensate precipitate retains a significant proportion of alcohols. Československé AO No. 169 239 describes a method for detoxifying and pretreating wastewater from the production of urea-formaldehyde adhesives by aldolizing formaldehyde, while no other organic substances are recovered from the wastewater.

The above-mentioned drawbacks overcome the present invention, which is concerned with a process for detoxifying and pretreating waste water containing formaldehyde, butanol and / or isobutanol, resin residues and optionally methanol, produced by butanol and / or isobutanol etherified urea-formaldehyde and melanin-formaldehyde resins while recovering the alcohols present. SUMMARY OF THE INVENTION An alkanizing agent, in particular calcium hydroxide, is added to the waste water at a temperature of from 40 to 90 ° C in an amount of 0.08 to 0.2 mol per mol of formaldehyde present, thereby converting the formaldehyde by aldolization to a non-toxic and biodegradable formosis. The treated waste water is subjected to either azeotropic distillation or, in the presence of methanol, distillation at a pressure of 13-101.3 kPa, after distillation of 30-70% of the effluent volume, the distillate being further rectified with optional azeotropic dewatering of the butanol and / or isobutanol fraction.

An advantage of the present invention is the possibility of treating wastewater from the production of lacquer amino resins so that the alcohols present are recovered for further use and the reduced wastewater toxicity by reacting formaldehyde to an aldol will allow wastewater treatment in biological treatment plants or other disposal.

The general process of the waste water detoxification and pretreatment process is as follows: to the waste water containing formaldehyde, butanol and / or isobutanol or methanol is added with stirring calcium hydroxide powder, paste or suspension in an amount of 0.08 to 0.2 moles of calcium hydroxide per 1 mole of formaldehyde. The mixture thus obtained is tempered at 40 to 90 ° C, preferably at 60 ° C, until the formaldehyde has reacted completely.

If, in addition to formaldehyde, the waste water contains only bunanol and / or isobutanol, azeotropic distillation is carried out after completion of the aldolization. The waste water can then be treated biologically.

♦

If the waste water contains, in addition to formaldehyde and butanol and / or isobutanol, methanol is also distilled off at normal or reduced pressure of the front fraction in an amount of 30 to 70% by weight after completion of the aldolization. waste water depending on the methanol content, so that the remaining waste water contains methanol at a low concentration and can also be purified biologically.

The front fraction is then rectified on the column, the methanolic fraction is removed from the top of the column, butanol and / or isobutanol fraction from the side off-take and water is removed from the digester. The butanol and / or isobutanol fraction can be processed by azeotropic distillation to an alcohol which can be returned to the resin preparation. Pure water is removed from rectification and azeotropic distillation as a distillation residue, which can be drained into the sewer. The invention is further illustrated by the following examples.

Example 1 kg of waste water from the production of lacquer amino resins prepared from an aqueous formaldehyde solution of the composition:

4.0 wt. of methanol 7.0% wt. butanol 3.0 wt. formaldehyde 86.0 wt. water

was fed into a reactor equipped with a stirrer, a descending condenser with a draft, steam heating and water cooling. 207 kg of calcium hydroxide as technical lime hydrate were added to the reactor and the reaction mixture was heated to 60 ° C. The exothermic reaction increased the temperature to 64 ° C and cooled back to 60 ° C. At this temperature, the reaction mixture was tempered for 60 minutes. After this time, a formaldehyde content of 0.0% by weight was found.

6.015 kg of distillate was then distilled off from the reaction mixture, which was 34.2% by weight. total weight. The distillate had the following composition:

20.2 % wt. butanol 10.8 % wt. of methanol 69.0 % hirtot. water

The distillation residue contained, in addition to the aldolized formaldehyde, 0.4 wt. of methanol. This residue can be disposed of in a biological treatment plant.

The distillate was rectified on a continuous 25 tray rectification column. 92.4 wt. methanol with a butanol content of 1.6 wt. at reflux 6. A butanol fraction was obtained from the 20-storey side flue with the following composition:

1.3 % hmót. of methanol 37.5 % wt. butanol 61.2 % wt. water

The distillation residue was water without methanol and butanol.

The butanol fraction was azeotroped to obtain butanol containing 20.5 wt. water and 1.2 wt. % of methanol, which can be used for the further production of lacquer amino resins.

Example 2 kg of waste water from the production of lacquer amino resins prepared from an aqueous formaldehyde solution of the composition:

5.8 % wt. of methanol 7.2 % wt. butanol 5.0 % wt. formaldehyde 82.0 % wt. water

0.345 kg of lime hydrate at 60 ° C was aldolized for 40 minutes in the same reactor as in Example 1. The free formaldehyde content dropped to 0.0 wt%.

13.145 kg of distillate were distilled off from the reaction mixture at normal pressure,

amounted to 64.6 Ϊ wt. Total weight of composition:

8.8 wt. of methanol 11.1 % wt. butanol 80.1 % wt. water

The distillation residue contained neither methanol nor butanol and could be disposed of in a biological treatment plant.

The distillate was rectified on a continuous 25 tray rectification column. 86.5% by weight were recovered from the top of the column at reflux 6 when injected onto the 13th floor. methanol with a butanol content of 3.9 wt.

Butanol fraction containing 2.9 wt. % methanol, 27.4 wt. % butanol and 69.7 wt. water.

The distillation residue consisted of butanol-free and methanol-free water which could be disposed of in the sewer.

The butanol fraction was distilled azeotropically and the obtained butanol could be used for further production of lacquer amino resins.

Example 3 kg of waste water from the preparation of butanolene of an etherified melamine-formaldehyde resin prepared from paraformaldehyde of the composition:

4.2 wt. % butanol 3.26 wt. % formaldehyde 0.01 wt. % toluene 92.53 wt. water less than was fed to a reactor equipped with a stirrer, descending condenser and a separating funnel with a charge, steam heating and water cooling. 0.160 kg of calcium hydroxide was added to the reactor and the reaction mixture was heated to 60 ° C with stirring. By exothermic reaction the temperature rose to 63 ° C. After cooling to 60 ° C, the mixture was stirred and tempered for 60 minutes until the free formaldehyde content dropped to 0.0 wt%. After the aldolization was complete, the reaction mixture was further heated and the azeotrope of butanol and water ob. mp 92.7 ° C. This azeotrope separated into a butanol phase containing 79.38 wt. % butanol and 20.62 wt. water and an aqueous phase that was returned to the reactor.

After distilling off all butanol, 1.05 kg of a butanol fraction was obtained, which can be used in the further production of resins. The waste water from the reactor can be biologically purified after cooling.

It adds · kg of waste water from the preparation of isobutanolene of etherified melamine-formaldehyde resin prepared from paraformaldehyde with the following composition:

4.4 i wt. % isobutanol 2.98 wt. % formaldehyde less than 0.01 wt. toluene

92.61% wt. The water was worked up in the apparatus of Example 3, in the first step by aldolizing formaldehyde by adding 0.206 kg of calcium hydroxide and heating for 60 minutes at 60 ° C, in the second step by azeotropic distillation of isobutanol / water at b. 1.06 kg of isobutanol containing 17.3 wt. water, which can be used in the further production of resins.

The distillation residue containing formose as the aldehyde formaldehyde product can be purified in a biological treatment plant.

Claims (1)

object of the invention Process for detoxifying and pretreating waste water from the production of lacquer amino resins containing formaldehyde, butanol and / or isobutanol, resin residues and optionally methanol, while recovering the alcohols present, characterized in that an alkalinizing agent is added to the waste water at 40 to 90 ° C in particular calcium hydroxide, in an amount of 0.08 to 0.2 mol per mole of formaldehyde present, thereby converting formaldehyde by aldolization to a non-toxic and biodegradable formose, and subjecting the treated waste water to either azeotropic distillation or, in the presence of methanol, distillation under pressure 13 to 101.3 kPa, where after distillation of 30 to 70% of the volume of the waste water, the distillate is further rectified with optional azeotropic dewatering of the butanol and / or isobutanol fraction.