FI70872C - FOERFARANDE FOER RENING AV AVFALLSVATTEN SOM INNEHAOLLER FENOLFENOLDERIVAT ELLER FENOL OCH FORMALDEHYD - Google Patents

Description

T 70872

Method for the treatment of waste water containing phenol, phenol derivatives or phenol and formaldehyde

Divided separated from patent application 773299.

5 (FI patent 64793)

The invention relates to a process for the treatment of effluents containing phenol, phenol derivatives or phenol and formaldehyde by treatment with hydrogen peroxide.

Phenol synthesis, coke production and gas installations, dry distillation of lignite and not least the production of phenol-formaldehyde resins (phenolic plastics) generate phenolic effluents of different concentrations.

The complete removal of toxic phenols as well as toxic formaldehyde from the effluents of the latter industrial sectors, especially in such a way that such effluents are subsequently suitable for biological treatment, is still a very important task which has not been satisfactorily solved in a high concentration range so far.

In the manufacture of said phenolic plastics, e.g.

the so-called. "reaction waters" which, depending on the condensation method, are either temporal or acidic, contain volatile phenol in a concentration of 1,700 to 15,000 mg / l and free formaldehyde in a concentration of 1,200 to 8,100 mg / l (F. Meinck, H. Stoof, K.

25 Kohlschutter "Industrie-Abwässer", 4th edition, Gustav Fischer-Verlag, Stuttgart, 1968, p. 619).

Several methods are known for the treatment of phenolic wastewater, but these methods are not generally suitable for use in a wider concentration range.

At high phenol concentrations, for example, steam distillation can be used to recover phenol. In addition, several extraction methods are known in which, for example, benzene, toluene or also tricresyl phosphate is used to carry out the extraction of phenol. However, these methods have the disadvantage that certain residual components of the extractant end up in the effluent; 2 70872, in addition to the so-called the "washing liquid" varies, so complete removal of phenol is not possible.

Complete phenol removal can be accomplished by evaporation of the effluent and incineration of the residues. However, these 5 methods consume considerable energy.

At low phenol concentrations, adequate phenol removal can be obtained using special activated carbons, however, the effect depends on the amount of carbon, the species, the granularity and the method of operation (time of action, pH and temperature of the waste water).

Depending on the composition and concentration of the phenolic wastewater, the adsorption efficiency is very variable and at medium and high phenolic concentrations e.g.

From a concentration of 1,000 ppm, too expensive.

One adsorption method uses certain synthetic resins, e.g. polymethacrylates or polyvinyl benzenes. Thus, for example, the phenol content of phenolic wastewater can be reduced from 6,700 ppm to about 0.1 ppm (U.S. Patent Nos. 3,663,467, 3,531,463).

20 However, such adsorption methods cannot be used for phenol-formaldehyde-containing waste water from the plastics industry, since the toxic waste formaldehyde still remains in the waste water thus treated.

In some cases, phenol-rich effluents can also be biologically treated in so-called "Nocardia method". Pure cultures of these organisms close to the fungi are inoculated into biofilter or activated sludge plants. In the preferred case, a purification effect of 99% is obtained, so that a certain residual fraction remains in the biodegradation.

This is because the effect is always dependent on other conditions, so that the organisms are damaged or even destroyed by too much phenol or, correspondingly, by other waste-water toxins. The method cannot therefore be considered safe in preventing the toxicity of the effluent.

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In addition, in the use of such a special biological fermentation or active plant, N- and P-containing nutrient salts must always be added (Gesundh.-Ing. 81) (1961) (1960, 205). These measures require the relatively expensive use of a special clarification plant.

In a very known method, the phenol is oxidized with chlorine dioxide. Chlorine dioxide is obtained either by the action of acids on chlorite, preferably Na chlorite, or by reacting chlorine with sodium chlorite, e.g.

In the presence of 10 sulfuric acid. However, in this latter process there is a risk that chlorophenols will produce chlorophenols which are even more toxic. In addition, the oxidation does not take place 100%. This also applies to the generation of chlorine dioxide by the action of acid on chlorite-15. In this case, however, far-reaching oxidation can be obtained. However, experiments have shown by gas chromatographic analyzes of the effluents thus treated that, after oxidation, varying amounts of phenol remain in the effluent, ranging from about 10 ppm to more than 100 ppm. In addition, gas chromatography yielded hitherto unidentified foreign peaks that could be assumed to be due to oxidation intermediates (quinones, hydroquinones, or possibly chlorinated products) (see also H. Thielmann, Gesund.-Ing. 92 (1971), 10, p. 297).

25 Corrosion problems due to the strong acidity of waste water cannot be ignored either.

According to literature data (Klossowski, Jerzy,

Gaz, Woda Tech Sanit. (1968), 42, 197-200), chlorine dioxide gas developed from sodium chlorite and sulfuric acid decomposes phenol and its derivatives by only 83%.

Oxidation of phenol with chlorine dioxide results in p-benzoquinone in the acidic and neutral range, while in the alkaline range a large excess of chlorine dioxide (5 mg ClCl 3 to 1 mg phenol) gives a mixture of organic acids, mainly maleic and oxalic acid (Chemical Abstract, 79, 23266m).

U.S. Patent No. 4,70872 to 141,814 describes a process for treating wastewater from phenol / formaldehyde resin production by removing formaldehyde by performing a quick-lime treatment at room temperature or 98 ° C and removing the phenol by oxidizing either electrochemically or MnCl 2. with. "Quick-line" means calcium hydroxide.

In another method, phenol, methanol and formaldehyde are removed from wastewater. by "liquid phase oxidation" 10 (I.S. Stepanyan, I.A. Vinokur, G.M. Padaryan, khim. prom.

(1972), 30/31 or Int. Chem. Eng. 12 (1972), 4, 649/651). In this process, wastewater is blown with air at a pressure of 40 bar at 200 ° C through nozzles into an electrically heated reactor. However, only about 95% phenol oxidation, about 77% methanol and about 93% formaldehyde oxidation have been obtained as experimental results. In another series of experiments, the oxidation rates of these substances were only 80%. The method is technically quite cumbersome and toxic substances remain in the wastewater.

German Offenlegungsschrift No. 2,404,264 describes a process for the treatment of wastewater containing phenol, formaldehyde and their reaction products, which process is based on the addition of water-soluble aminoplastic resin precondensates or aqueous solutions thereof to the wastewater. The reaction mixture is kept at the boiling point in the alkaline range for 2 to 8 hours, then neutralized and the precipitated reaction products are separated.

As can be seen from the examples given, only pre-purification can be performed by this method; complete removal of phenol and formaldehyde is impossible.

It has also been proposed that effluents containing phenol and phenol / formaldehyde be treated with alkali or alkaline earth chlorites in the presence of certain amounts of formaldehyde (German Application 2,657,192). This method 35 completely removes the phenol and formaldehyde, however, the treated wastewater becomes saline through alkali and alkaline earth metal chlorite treatment. The wastewater thus treated can then possibly be further treated with activated carbon.

In addition, a process is known in which phenol is removed from wastewater by means of hydrogen peroxide in the presence of ferric chloride. In this case, the pH of the effluent is adjusted to pH 2.5 to 3.5 before treatment and to pH 10 after treatment. After clarification of the suspension with suitable substances, the phenol content of the effluent is still 0.3 ppm (Japanese Patent Application No. 10,090,902/72 - Application Publication No. 77449/74).

One method of treating phenol / formaldehyde-containing wastewater also uses hydrogen peroxide with an application rate of more than 1.5 times the COD value of the wastewater and ferrous sulfate. The pH of the effluent decreases to 3-4 due to the addition of hydrogen peroxide and fer-15 rosulfate (Japanese Patent Application 44906/72 - Application Publication No. 6763/74).

Both of the latter methods are suitable for use with low phenol and formaldehyde contents up to 100 ppm. In order to achieve fully higher phenol concentrations in the effluent, the amount of iron and salt must be increased accordingly, which leads to an excessive salt load.

In addition, in the latter case, at least 50 ppm of formaldehyde remains.

Furthermore, the above methods do not affect the purification of wastewater containing phenolic derivatives such as pyrocatechol, resorcinol, pyrogallol, cresols, chlorophenol or hydroquinone. The object of the invention is to remove phenol, phenol derivatives or phenol and formaldehyde 30 without salt loading from wastewater, even when present in high concentrations. High concentrations mean concentrations of phenol or phenol derivatives up to 0.5% and concentrations of formaldehyde up to 5%, as higher concentrations are not economical.

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The process according to the invention for the treatment of effluents containing phenol, phenol derivatives or phenol and formaldehyde by treatment with hydrogen peroxide is characterized in that 0.5 to 2 g per liter of effluent are added to the effluent before treatment with hydrogen peroxide-5. ).

Unlike the above-mentioned methods using hydrogen peroxide and iron salts, the method of the present invention is not pH dependent. It can be performed on neutral, acidic or temporal wastewater.

Wastewater containing alkali-reactive phenol, phenol derivatives or phenol and formaldehyde can be purified relatively quickly by treatment with hydrogen peroxide if 0.5-2 g / liter of effluent is added to the treated effluent before adding sodium peroxide to sodium ferriethylenediamine tetraacetate The complex salt of 8 FeNa'3H2O * * can be added as a solid or aqueous solution to the effluent to be treated.The amount of hydrogen peroxide required per mole of phenol or phenol derivative for their oxidation is 8 moles If a further 2 moles of hydrogen peroxide are present at the same time Irrespective of the phenol and formaldehyde content of the effluent, 1-2 g of sodium ferricethylenediamine-tetraacetate trihydrate complex salt per liter of effluent is sufficient, and the pH of the effluent should be at least 8. In principle, neutral or acidic effluents can also be treated by adjusting their p H first with alkali hydroxide to at least 30 but not more than 12. In practice, the process is carried out by adding to the alkali-reactive effluent to be treated with stirring the complex salt and then the required amount of hydrogen peroxide solution corresponding to phenol, phenol derivatives and formaldehyde. After a few minutes, usually after 5-15 minutes, of the addition of hydrogen peroxide, an oxidative reaction begins, which can be observed in the dark discoloration of the wastewater, an increase in temperature and a decrease in pH. After about 30 minutes after the reaction is complete, the pH is at most 2. All known alkali or alkaline earth metal hydroxides are suitable for neutralizing the acidic, dark effluent obtained, preferably calcium hydroxide in the form of lime milk. Upon neutralization, the effluent obtained by the method described above whitens and precipitates an alkaline earth metal hydroxide precipitate containing small amounts of iron.

If the purification reaction does not start quickly enough, it has proven advantageous to add small amounts of activators to initiate the reaction. Suitable activators are halides, sulphates, nitrates and also organic salts, such as alkali or alkaline earth metal formates, e.g. sodium, potassium, calcium or barium formate, and also the corresponding zinc, aluminum, nickel and manganese salts. Sodium chloride is very suitable.

Activators are added in an amount of 0.1 to 0.2% by weight of the amount of hydrogen peroxide used. It is possible to dissolve them already in hydrogen peroxide or they can be added to the wastewater as solids. Highly dispersed water-insoluble silicic acids are also suitable as activators in said amounts.

Hydrogen peroxide is used in an amount of 7.5 to 8 moles per mole of phenol or phenol derivative. In the presence of formaldehyde, it is necessary to add a further 2 moles of hydrogen peroxide per mole of formaldehyde.

The purification is preferably carried out at room temperature or at the temperature at which the effluents are obtained.

30 In general, waste water to be treated can be treated as such by this method. Only if the phenol content is more than 5,000 ppm, it is recommended to dilute the wastewater to a phenol value of less than 5,000 ppm before treating the wastewater with the method according to the invention, so that the reaction does not take place too vigorously.

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Quantitative determination of phenol or its derivatives is carried out by gas chromatography under the following conditions:

Gas chromatograph Perkin-Elmer F 7 (FID). Column 5 temperature 180 ° C, injection housing 230 ° C, flow approx. 24 ml / min; column 1 m Poropak P, No. 85, sample volume 1 μl / min; paper advance 0.5 cm / min.

Formaldehyde analysis is performed colorimetrically using a key highly sensitive condensation reaction of formaldehyde, acetylacetone and ammonia or ammonium acetate to form yellow diacetyldihydrolutidine (T. Nash. Nature (London) 170 (1952), 976).

The simplest and most advantageous way of working has proved to be the use of hydrogen peroxide solutions in which 0.05 to at most 0.1% by weight of NaCl have been dissolved.

Of course, sodium chloride can also be added to the treated wastewater as a solid.

The process is usually carried out by adding the required amount of hydrogen peroxide and about 0.1% of activator, preferably sodium chloride, to the effluent containing phenol, phenol derivatives or phenol and formaldehyde with stirring, whereby oxidation begins at room temperature within a few minutes of the end of the addition. It can be observed in the conversion of wastewater to dark, carbon dioxide evolution, temperature rise and pH drop to 2-1.

The whole reaction usually takes 30-40 minutes and can be completed by the cessation of gas evolution, stagnation or drop in temperature. The acidic wastewater is then neutralized. This also precipitates a small amount of iron ions present.

All known alkali or alkaline earth metal hydroxides are suitable for neutralization, preferably calcium hydroxide is used as lime milk.

35 After the settling of the iron hydroxide precipitate and the possible alkaline earth hydroxide precipitate, practically 9 70872 colorless, completely non-toxic effluents can be discharged to a biological clarification plant.

In addition to phenol, the process according to the invention can also remove o- and p-cresol as well as tert-butylphen-5-yl and hydroquinone.

The following examples illustrate the invention. They use both artificially prepared effluents containing phenol, phenol derivatives and phenol and formaldehyde in amounts of 100-5000 ppm, as well as effluents from the phenolic resin industry. All% are by weight.

Example 1

Sodium ferriethylenediamine tetraacetate trihydrate was added with stirring to temporal effluents having pH values between 8-9 and containing 100, 1,000 and 5,000 ppm phenol. The amounts of complex salt addition were 1-2 g per liter of wastewater. After the complex salt was dissolved, 10% hydrogen peroxide solution corresponding to the phenol content was added with stirring. This amount was 2.8 ml of 10% hydrogen peroxide solution per liter of wastewater in a sample containing 100 ppm phenol, 27.4 ml in a sample containing 1,000 ppm phenol and 137 ml in a sample containing 5,000 ppm phenol.

The same set of experiments was performed with 35% hydrogen peroxide, with the addition amounts per liter of effluent being 1.5 ml of 35% hydrogen peroxide solution in a sample containing 100 ppm phenol, 7.2 ml in a sample containing 1,000 ppm phenol and 36.2 ml in a sample containing 5,000 ppm phenol. ppm sample.

After a few minutes, the reaction started, which could be seen in the darkening of the effluent, an increase in temperature and a decrease in pH, and the evolution of CCl 2. After 30 minutes, the oxidation was complete and lime milk was added to the acidic wastewater samples to neutralize them. Analytical samples were taken from the bleached, clear effluent on top of the precipitated precipitate. According to 35 analyzes, the wastewater was phenol-free.

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Example 2 For effluent samples with pH values of 8-9 and containing in addition to phenol formaldehyde in amounts of 100 ppm phenol + 100 ppm formaldehyde, 5 1,000 ppm phenol + 1,000 ppm formaldehyde and 5,000 ppm phenol + 5,000 ppm formaldehyde, sodium ferric ethylenediamine tetraacetate trihydrate per liter of wastewater was added with stirring 1-2 g.

A 35% solution of hydrogen peroxide-10 was then added, which was used in the following amounts per liter of effluent: 2.7 ml to effluent with 100 ppm phenol + 100 ppm formaldehyde, 13.4 ppm to effluent with 1000 ppm phenol + 1 000 ppm formaldehyde and 66.4 ml to wastewater with 5,000 ppm phenol + 5,000 ppm formaldehyde. After the addition of hydrogen peroxide-15, the oxidation took place as described in Example 16.

After 30 minutes, the oxidation reaction was complete. Acidic wastewater samples with a pH of about 2 were neutralized with lime milk. After the precipitate settled, the bleached, clear 20 effluents were analyzed. Analyzes showed that the samples did not contain any phenol and in some cases only small amounts, 10 ppm formaldehyde.

Example 3

Alkaline industrial wastewater from the condensation of phenol and formaldehyde (resolihart-25 sit) contained 0.15% phenol and 0.04% formaldehyde by analysis. Formaldehyde was in bound form. The pH of the wastewater was 8.9. In addition, there were still amines and ammonia in this effluent.

To 400 liters of this wastewater was added with stirring 400 g of the complex salt of Example 1 as an aqueous solution (1 g / liter of wastewater). After dissolving the complex salt in the wastewater, 6.3 L of a 35% hydrogen peroxide solution was added in two portions. The first dose was 2/3 of the total and the second dose was 1/3. After the first dose, the temperature rose. After about 15-20 35 minutes, the oxidation reaction could be clearly observed from a decrease in pH and initially a weak CCl 2 evolution, 1, 70872 which was later confirmed. The temperature rose to 35 ° C. As the final amount of hydrogen peroxide solution was added, the temperature rose slightly, the pH dropped to about 3. It was then neutralized by the addition of lime milk, which whitened the effluent. After settling of the lime sludge containing small amounts of iron hydroxide, the clear wastewater on top was analyzed. The analysis showed that the phenol was completely absent and the formaldehyde was in small amounts on the order of 10 ppm.

Claims (4)

12 70872 Process for the treatment of effluents containing phenol, phenol derivatives or phenol + formaldehyde by treatment with hydrogen peroxide, characterized in that 0.5 to 2 g per liter of effluent are added to the effluent before treatment with hydrogen peroxide. Process according to Claim 1, characterized in that activators, such as sodium chloride or insoluble silicic acids, are used in the purification treatment. Process according to Claim 1, characterized in that 1-2 g of sodium ferriethylenediamine tetraacetate trihydrate are added to the effluent per liter of effluent. Method according to Claim 1 or 3, characterized in that the pH of the waste water is adjusted to 8.