CA1096069A - Process for the detoxication of waste water containing phenol, phenol derivatives or phenol and formaldehyde (ii) - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention provides a process for the purification of waste water which contains phenol, phenol derivatives or phenol plus formaldehyde which comprises adding 0.5 to 2 g of the complex salt sodium-iron (III)-ethylene diamine-tetracetate trihydrate (summation formula C10H12N2O8 FeN.3H2O) per litre of waste water to the waste water to be treated and then adding hydrogen peroxide thereto.

Description

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The present invention relates to a process for the detoxication of waste water containing phenol, phenol derivatives or phenol and formaldehyde.
Phenol-containing waste water with varying concentra-tions is ohtained in the phenol synthesis, in coke plants and gas plants, in lignite-coking plants and last not least in the production of phenol-formaldehyde resins (phenolic plastics).
The total removal of the toxically reacting phenol and of the likewise toxically reacting formaldehyde from waste water of the industrial branch mentioned last, particularly for a suhsequent kiological purification of this kind of waste water is as much as ever a very important problem, which could not yet be satisfactorily solved within a wide range of concentrations.
In the case of the phenolic plastics mentioned here-inbefore, for example, in the so-calle~ "reaction water" which ` reacts either alkaline or acid depending on the condensation process, the content of volatile phenol can be of the order of ~l 1700 to 15000 mg per litre and that of free formaldehyde between 1200 and 8100 mg per litre (F. Meinck, H. Stoff, H. Kohlschutter Industrie-Abwasser, 4th edition, Gustav Fischer-Verlag, Stutt-, gart, 1968, page 619).
~, A larae number of processes for the purification of waste water are known. However, the~ are not universally applicable over a wide range of concentrations.
In cases of high phenol concentra-tions, for example, ., i - .~ .
for the recovery of phenol, a distillation with steam can be suitable. ~oreover several extraction processes in which an extraction of the phenol is carriecl out with the aid of e.g.
benzene, toluene or tricresyl phosphate is known. I~owever, these processes have the disadvantage that certain residual components of the extracting agent get into the waste water. Furthermore, the "degree of washing out" of the different processes varies-so ~-, ' .

that a total removal of the phenol is not possible.
A total dephenolization can be attained by evaporating the waste water and by burnin~ the residues. However, this process requires a high consumption of energy.
In cases of low phenol concentrations an adequate ! removal of the phenol can also be attained with the aid of special active carbons However, the effect depends on amount, type and granulation of-the carbon as well as on the process (duration of action, pH value and temperature of the waste water).
! lo Depending on composition and concentration of the phenol-containing waste water the effect of adsorption varies 1 greatly and at medium ancl high concentrations, for example, at ' 1000 p.p.m. and higher, said process is too costly.
i; Another adsorption process comprises the use of specific synthetic resins, for example, polymethacrylates and ;~ polyvinyl benzenes.
` Thus, for example, in a phenol-containing waste water the phenol content could be reducecl from 6700 p.p.m. to approx-imately 0.1 p.p.m. (U.S. Patents 3,663,467 and 3,531,463).
However, these adsorption processes cannot be applied - .
to phenol-formaldehyde-containinq waste water of the synthetic resin industry since, now the same as ever, the toxically reacting formaldehyde remains in the waste water.
In individual cases waste water rich in phenol can also be treated biologically by means of the so-called "Nocardia process." Pure cultures of these types of organism, which are related to the actinomyces, are settled in tricklina-filter or activated sludge plants.
In the most favourable case a purifying effect of 99 can he attained so that even with biological de~radation a certain residual amount remains, -~ The effect depends largely on the other conditions.
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Thus, the flora is severely damaged by a phenol shock which is too severe or by other waste-water toxins and possibly the flora is even destroyed.
The process thus does not reliably detoxicate waste water, Moreover, for the adaptation of such a special film or activated sludge N- and P-containing nutrient salts must be added (Gesundh.-Ing. 81 (1960), 205 ff). These measures require the relatively costly operation of a special biological purifi- ~
cation plant. ~-~ well-known process is that of oxidizing the phenol by means of chlorine dioxide, which is obtained either ~y the action of acids on chlorite, preferably Na chlorite, or hy reacting chlorine with sodium chlorite, for example, in a sul-phuric-acid medium.
~lowever, the latter process involves the risk that the phenol is chlorinated to the even more toxically reacting chloro phenols. Furthermore the reaction is not 100~. This also applies to the generation of chlorine dioxide by the action of acid on chlorite. In this case, too, an extensive oxidation can be attained. However, this kind of tests performed by the applicant and the gas-chromatgraphical analysis of waste water thus treated have shown that after the oxidation greatly varying residual contents of phenol of the order of more than 10 to above 100 p.p.m. are still present. Moreover, the gas chromatograms show entraneous peaks which have not yet been identified. How-ever, it must be assumed that they are intermediate oxidation produc-ts (quinones, hydroquinones or possibly even chlorinated ~-products) (see H. Thielemann, Gesundh.-Ing. 92 (1971) No. 10, 297).
Corrosion problems due to intense acidifica-tion of the waste water should also be taken into account. ;
According to references in the literature (Klossawski, ~ 3 -. . ;.

Jerzy, Gaz, Woda Tech. Sanit. (1968) 42, 197-200) phenols and its derivatives are destroyed by gaseous chlorine dioxide (generated from Na chlorite and sulphuric acid) in amounts of only 83~
In the acid to neutral range the oxidation of phenol by chlorine dioxide results in p-benzoquinone as the final product of the phenol oxidation while in the alkaline medium a mixture of organic acids, primarily maleic acid and oxalic acid, is formed due to a high excess of chlorine dioxide (5 mg `
of CLO2 per 1 mg of phenol)(Chemical Abstracts 79, 232 66m).
In the U.S.S.R. Patent 141,814 the purification of waste water of the phenol-formaldehyde-resin product is described - ~`
and the formaldehyde is to be removed by treating the waste water with "~uick lime" at room temperature or at 98C and the phenol is to be removed by oxidation either electrochemically or with MnO2. BY "~ui~k lime" ;s me~nt ~alcium nxJ.de~ ~ .

In another process the removal o~ phenol, methanol and formaldehyde from waste water is carried out by means of a so-called "liquid-phase oxidation" (I.S. Stepanyan, I.A. Vinokur, G.M. Padaryan, khim. prom. (1972), 6, 30/31 and Int. Chem. Eng.
12 (1972), 4, 649/651). In this process the waste water is fed into an electrically heated reactor by means of air under a `-pressure of 40 bars and at 200C. However, test data have only shown degrees of oxidation of approximately 95% for phenol, 77 for methanol and 93~ for formaldehyde, In another series of tests the degrees of oxidation were only at 80% for said substances. The process is technically -very expensive.

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~esidues of the toxically reaCtin~J substances remain.
A process Eor the prepurification of ~aste water which contains phenol, formaldehyde and their reaction products is described in the laid-open German Specification 2,404,264.
According to this process water-soluble aminoplast-resin precon-densates or their aqueous solutions are added to the waste water. ~;
The reaction mixture is kept in the alkaline ran~e at boiling temperature for 2 to 8 hours and the precipitated reaction pro-ducts are separated.
As is evident from the cited examples only a prepurif-ication of this kind of waste water can be attained with this process, a complete removal of phenol and formaldehyde is ~ -impossible.
It has also been proposed to treat phenol-containing waste water and phenol- and formaldehyde-containing waste water wi-th alkali or alkaline-earth chlorites in the presence of specific amounts oE formaldehyde(~erman Patent .... /Patent . ..~,;
Application P 26 57 192.6).
A complete elimination of phenol and formaldehyde is achieved with this process, but the waste water thus treated is salted by the alkali or alkaline earth chlorites. If required, the waste water thus treated can then be subjected to an after-treatment with active carbon.
It is also known to remove phenol from waste water with hydrogen peroxide, that is to say, in the presence of ferric chloride. In this case the pH value of the waste water is adjusted to 2.5-3.5 prior to the treatment and to 10 àfter the treatment. After clarifying the suspension with corresponding agents the waste water still contains 0.3 p.p.m. of phenol (Japanese Patent Application 118 8902/72 - laid open under No.
77449/74-).
In yet another process or the detoxication of phenol-and forrnalcdcilydc--containin~ waste water hydrogen per~xide is also used, namely ln amount of rnore than 1.5 times the COD value of the waste water, as well as ferrous sulphate.
On adding the hydrogen peroxide and the ferrous salt the pH value of the waste water is reduced to 3-4 (Japanese Patent Application 44906/72 to Shinto Kogyo Co. Ltd. - published under ~o. 6763/74 on January 21, 1974).
The two processes mentioned last relate to low phenol and formaldehyde contents of up to 100 p.p.m.
In order to assure comple-te oxidation in the case of high phenol contents, the amount of iron salts must be increased correspondingly and this results in an intolerable salt burden.
Moreover, in the process mentioned last a residual formaldehyde content of at least 50 p.p.m. remains.
Furthermore the processes mentioned hereinbefore had no detoxicating effect on waste water which contained phenol derivatives such as pyrocatechol, resorcinol, pyrogallol, cresols, chloro phenol and hydroquinone.
It is the aim of the invention to eliminate completely phenol, phenol deriva-tives or phenol plus formaldehyde from waste water even in the case of high concentrations but without burdening the waste water with salt.
By high concentrations are meant contents of phenol or phenol derivatives up to a maximum of 0.5% and formaldehyde contents of up to a maximum of 5% since the process is not so economical at higher concentrations.
In copending application No. 295,737 filed on even date herewith there is disclosea a process for the purification ;
of phenol-, phenol derivatives- and phenol- and formaldehyde-containing was~e water with hydrogen peroxide in the presence ' of metallic iron or copper is preferably used for neutral- or weakly acid-reacting waste water.
~or alkaline-reacting waste water said process is not 50 favourable since the oxidation reaction is substantially retarded in an alkaline medium. It usually takes several hours until the phenol and formaldehyde are completely eliminated as `
compared with the reaction in an acid medium or in a neutral medium, in which the oxidation process is completed within 30 to 60 minutes.
Of course, in the case of alkaline waste water the process could be accelerated by adding mineral acids, but this would result in an undesirable increase in the salt content of the waste water.
It has now been ~ound that alkaline-reactiny waste water which contains phenol, phenol deriva~:ives and phenol plus formaldehyde can also be relatively fast detoxicated with hydroqen peroxide if 0.5 to 2 y of the complex salt sodium-iron (III)-e-thylene-diamine--tetracetate trihydrate (summation formula ClOH12N2O8FeNa . 3112O) per litre of waste water are added to the waste water to be treated prior to the addition of the hydro~en peroxide.
Accordiny to the present invention therefore there is provided a process for the purification of waste water which contains phenol, phenol derivatives or phenol plus formaldehyde which comprises addiny 0.5 to 2 g of the complex salt sodium-iron (III)-ethylene diamine-tetracetate trihydra-te (summation formula CloH12N2O8 FeN.3H2O) per litre of waste water to the waste water to be treated and then addin~ hydroyen peroxide thereto. ~ :
Of course, said complex salt can also be added as an agueous solution to the waste water to be treated.
The amount of hydro~en peroxide per mole of phenol or phenol derivative which must be used for the oxidation of phenol or phenol derivative is 8 moles.
If formaldehyde is present at the same time, then 2 ,, .- : , ,-: ..

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moles of hydrogen peroxide are additionally re~uired, Irrespective of the content of phenol and formaldehyde in the waste water l to a maximum 2 g of the complex salt sodium-iron (III)-ethylene-diamine-tetracetate-trihydrate are sufficient for 1 litre of waste water. The pH value of the waste water should be at least 8.
Neutral or acid waste water can also be treated by means of the process according to the invention if its pH is adjusted to at least 8 prior to the treatment, for example, with alkali liquor. However, the pH value should not exceed 12.
In general, the procedure is such that the co~plex salt to be used according to the invention is added first to the alkaline-reacting waste water to be treated, while stirring, whereupon the required amount of hydrogen-peroxide solution is added corresponding -to the conccntration of phenol, phenol derivative and formaldehyde.
Within a few minutes, usually about 5 to 10 minutes after the addition of -the hydro~en peroxide, the oxidation reaction starts. The oxidation reaction is evident from the darkening of the waste water, the increase in temperature, the generation of carbon dioxide and the decrease of the p~l value.
~ t the end of the reaction the pH is not higher than

2, the reaction time is approximately 30 minutes.
For the neutralization of the acid, dark-colored waste water any known alkali or alkaline-earth hydroxide is suitable, but calcium hydroxide in the form of milk of lime is preferred.
On neutralizing the waste water obtained by means of the process according to the invention its colour brightens and the alkaline-earth-hydroxide precipitate settles. Said pre-cipitate contalns small amounts of ferric hydroxide.

The quantitative determination of phenol and possibly ~6~
of phenol derivatives is carried out hy ~as chroma-tography under the followiny condit;ons:
Gas chromatograph Perkin-Elmer F 7 with FID. Temper-ature of the column 180C, in~ection block 230~, flow approx-imately 24 ml per minute, column 1 m of Poropak P, No, 85, amount of sample 1 ,u litre per minute, paper feed 0.5 cm per minute.
The analysis is carried out colorimetrically with the aid of the very sensitive condensation reaction between formaldehyde, acetyl acetone and ammonia or ammonium acetate to the yellow-colored diacetyl-dihydro lutidine/T, Nash, Nature (London) 170 (1952), 976.) The analysis for phenol and formaldehyde, that is to say, of acid waste water samples and of neutralized waste water samples showed that after applying the process according to the invention neither phenol, phenol derivative nor formaldehyde were present. Their elimination thus was complete.
The process of the present invention will be further illustrated by way of the following Examples.
Example 1 Alkaline-reacting waste water having pH values between 8 and 9 and phenol contents of 100, 1000 and 5000 p.p.m.
were mixed with sodium-iron (III)-ethylene diamine-tetracetate trihydrate while stirring, The amount of complex salt, relative to one litre of waste water, were between 1 and 2 g, After dissolving the complex salt the amounts of 10% hydrogen-peroxide solution required for the phenol content were added while stirring. For 100 p.p.m, of phenol 2.8 ml of 10% hydrogen-peroxide solution were required per litre of waste water, for -1000 p.p.m~ of phenol 27.4 ml of 10% H2O2 per litre and for 5000 p.p.m, of phenol 137 ml of 10% H2O2 solution were required per litre of waste water.
The same test series was carried out with a 35 t~
`t' . ~ , . . , . ! `, hydrogen-peroxide solution so tha-t corrcspondingly 1.5 ml of 35% hydrogen-peroxide solution were required for 100 p.p.m. of phenol ! 7,2 ml of 35% hydrogen-peroxide solution were required for 1000 p.p.m. of phenol per litre of waste water and for 5000 p.p.m. of phenol 36.2 ml of 35% hydrogen-peroxide solution per litre of waste water.
The reaction started within a few minutes. This was evident from the darkening of the waste water, the increase in temperature, the decrease of the pH value ana the generation of C02.
After 30 minutes the oxidation was completed. The acid-reacting waste water samples were neutralized by the addition of milk of lime. The brightened clear waste water above the settled precipitate was analyzed. The analysis showed that the samples were free from phenol.
Example 2 Waste water samples having pH values between 8 and 9 and containing formaldehyde in addit:ion to phenol, i.e., 100 p.p.m. oE phenol plus 100 p.p.m. of formaldehyde, 1000 p.p.m. of phenol plus 1000 p.p.m. of formaldehyde and 5000 p.p.m. of phenol plus 5000 p.p.m. of formaldehyde, were mixed with sodium-iron (III)-ethylene diamine-tetracetate trihydrate while stirr-ing, 1 to 2 g of complex salt per litre of waste water being dissolved in the samples.
The 35% hydrogen-peroxide solution was then added in the following amounts:
For waste water containing 100 p.p.m. of phenol plus 100 p.p.m. of formaldehyde 2.7 ml of 35% hydrogen-peroxide solution per litre of waste water, for waste water samples containing 1000 p.p.m. of phenol plus 1000 p.p.m. of formalde-hyde 13.4 ml of 35% hydrogen-peroxide solution per litre of waste water, for waste water samples containing 5000 p.p.m. of phenol . ,~

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plus 5000 p.p.m. of formaldehyde 66.4 ml of 35% hydrogen-peroxide solution per litre oE waste water.
After the addition of the hydrogen-peroxide solution the oxidation reaction proceeded in the manner described in Example l.
The oxidation reaction was completed within 30 minutes.
The acid-reacting waste water sarnples (pH value approximately 2) were neutralized with milk of lime. After the precipitate had settled the brightened clear waste water was analyzed again.
The analyses showed that all the samples were completely free from phenol and in some cases only traces of formaldehyde of -lO p.p.m. were present.
Example 3 The analysis of an industrial effluent obtained in the alkaline condensation of phenol and Eormaldehyde (one-stage resin) showed a phenol content of 0.15~ and a formaldehyde content of 0.04%.
The formaldehy~e was in a combined form. The pH value of the waste water was 8.9. Moreover this waste water also contained amines and ammonia. ~ ;
A large of amount of 400 litres of this industrial effluent was mixed with 400 g of an aqueous solution of the complex salt of Example 1 (concentration 1 g per litre of waste -water). After dissolving the complex salt 6.3 litres of 35%
hydroqen-peroxide solution were added to the waste water in 2 batches. The first batch comprised two thirds of the total amount to be applied and the second batch the rest. The temper-ature increased on adding the first batch. After approximately 15 to 20 minutes the oxidation reaction was distinctly notice- ~
able. It was evident from the decrease of the pH value and ;
from the generation of CO2, which was weak at first but then intensified increasingly, The temperature rose to 35C. After r adding the second ba~ch the temperature s-till increased slightly and the pl-l val~le decreased to approximately 3.
After approximately 1 hour the oxidation reaction was completed and the waste water had a brown coloration. ~-The waste water samples were then neutralized by the addition of milk of lime and the waste water brightened. After the lime precipitate, which still contained small amounts of ferric hydroxide, the clear waste water could be analyzed.
The analysis showed that the waste water was completely free from phenol and that formaldehyde was present only in traces of the order of 10 p.p.m.

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Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the purification of waste water which contains phenol,phenol derivatives or phenol plus formaldehyde which comprises adding 0.5to 2g per litre of waste water of the complex salt sodium-iron (III)-ethylene diamine-tetracctate trinydrate (summation formula C10H12N2O8FeN.3H2O) per litre of waste water to the waste water to be treated and then adding hydrogen peroxide thereto.

2. A process according to claim 1 in which the pH
value of the waste water is at least 8.

3. A process as claimed in claim 1 in which the pH
value of the waste water is adjusted to be at least 8.

4. A process according to claim 1, 2 or 3 in which 1 to 2 g of sodium-iron (III)-ethylene diamine-tetracetate trihydrate are added per litre of was-te water.

5. A process as claimed in claim 1, 2 or 3 in which the hydrogen peroxide is added in an amount from 8 to 10 moles.