JPH0256956B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for treating an aqueous solution containing phenols and formaldehyde, and by removing phenols and formaldehyde from an aqueous solution containing phenols and formaldehyde, the BOD (biological oxygen demand) and COD of the aqueous solution are reduced. The present invention relates to a method for treating an aqueous solution containing phenols and formaldehyde for the purpose of reducing (chemical oxygen demand). More specifically, the present invention provides the following methods for removing phenols and formaldehyde from an aqueous solution containing at least phenols and formaldehyde: 1. Phenols are removed using a phenol extractant or adsorbent; 2. Formaldehyde is removed using an alkali. The present invention relates to a method for treating an aqueous solution containing at least phenols and formaldehyde, characterized in that formaldehyde is decomposed and removed mainly into formate and methanol by bringing it into contact with a copper compound in the presence of phenols and formaldehyde. Aqueous solutions containing phenols and formaldehyde are mainly generated during the production of phenolic resins and the like. The wastewater usually contains several percent or more of phenols, several percent or more of formaldehyde, and organic compounds such as methanol, and the COD usually reaches more than 100,000 ppm. In this way, wastewater from the production of phenolic resins and other products contains large amounts of phenols,
As is well known, there are strict regulations on the disposal of these wastewaters from the perspective of preventing environmental pollution, as they contain formaldehyde, methanol, etc. Therefore, it is necessary to perform some kind of purification treatment on these wastewaters. The activated sludge method is generally adopted as a treatment method for wastewater containing phenols and formaldehyde, but due to the strong toxicity of phenols and formaldehyde, even when the sludge is sufficiently acclimatized, phenols can reach several hundred ppm. , treatment with formaldehyde is possible only at low concentrations of several hundred to several thousand ppm. Therefore, wastewater containing several percent or more of phenols and formaldehyde must be treated as dilution, which requires a large amount of water and equipment. Activated sludge also has the disadvantage that it is extremely sensitive to changes in concentration, making treatment management extremely difficult. There is also a method of burning an aqueous solution containing phenols and formaldehyde as it is, but this method is difficult to call effective as it increases processing costs and results in a loss of resources. The present inventors have completed the present invention as a result of intensive study on the above-mentioned problems. In the present invention, when removing phenols and formaldehyde from an aqueous solution containing phenols and formaldehyde, the phenols contained in the aqueous solution are extracted using an extractant or removed using an adsorbent. The present invention further provides a method for treating an aqueous solution containing phenols and formaldehyde, which comprises removing formaldehyde by bringing the formaldehyde into contact with a copper compound in the presence of an alkali and decomposing it into methanol and formate. Phenols in the present invention include phenol,
Examples include alkylphenols (cresol, xylenol, trimethylphenol, etc.), allylphenols, alkenylphenols, polyhydric phenols (resorcinol, etc.), chlorophenols, nitrophenols, and low molecular weight condensates of phenols and formaldehyde.
Further, according to the present invention, phenols can be removed regardless of the concentration of phenols, although phenols are contained in general phenolic resin wastewater in an amount of several percent or more. Further, formaldehyde in the present invention refers to formalin and paraformaldehyde, which can be treated regardless of concentration. When carrying out the present invention, an aqueous solution containing phenols and formaldehyde may contain organic substances such as methanol, amines, fatty acids, sulfuric acid, inorganic salts, etc. in addition to phenols and formaldehyde. In the present invention, when extracting phenols from an aqueous solution of phenols and formaldehyde using an extractant, the extractant is a general organic extractant for phenols or a diluted version of this with a water-insoluble organic solvent. Phenols can be extracted by contacting with an aqueous solution. Specifically, organic extractants for phenols include hydrocarbons such as benzene, toluene, and xylene;
Alcohols such as octyl alcohol, ethers such as isopropyl ether, esters such as butyl acetate and ethyl acetate, ketones such as methyl isobutyl ketone and acetophenone, neutral phosphoric acid esters such as tributyl phosphoric acid and trioctylphosphine oxide Any organic extractant can be employed, such as tertiary amines such as trioctylamine, dibenzylamine, phenylpropylpyridine, or mixtures thereof. From the viewpoint of the phenol extraction effect, suitable organic extractants include ethers having 6 or more carbon atoms, esters having 6 or more carbon atoms, and tertiary amines having 10 or more carbon atoms. Furthermore, as an adsorbent for phenols, a basic ion exchange resin or a high porous resin can be used. Specifically, examples of basic ion exchange resins include strong basic ion exchange resins such as Duolite A-101 (manufactured by Diamond Shamrock Co., Ltd.), Amberlite IRA-400 (manufactured by Rohm and Haas Co., Ltd.), or KEX-212 (manufactured by Koei Co., Ltd.). (manufactured by Kagaku Kogyo Co., Ltd.), Amberlite IRA-45 (manufactured by Rohm and Haas)
Examples include weakly basic ion exchange resins such as or,
XAD-2 and XAD-4 as high porous resins
(manufactured by Rohm and Haas), ES-862 (manufactured by Diamond Shamlok), etc. Among these, it is particularly preferable to use weakly basic ion exchange resins or high porous resins from the viewpoint of adsorption amount of phenols and elubility of adsorbed phenols. As the weakly basic ion exchange resin, an anion exchange resin having a pyridine skeleton structure in the main chain is desirable. Next, in order to remove formaldehyde from a treated aqueous solution containing phenols and formaldehyde, in which phenols have been removed using an extractant or an adsorbent, the treated aqueous solution is brought into contact with a copper compound in the presence of an alkali to mainly undergo a Cannitzaro reaction. to decompose formaldehyde into methanol and formate and remove formaldehyde. As the alkali used in this case, it is preferable to use sodium hydroxide or potassium hydroxide. It is usually sufficient that the amount of alkali is at least 0.5 times the stoichiometric amount necessary for carrying out the Cannziaro reaction, that is, 0.5 times the molar amount of formaldehyde. The copper compound is cuprous oxide, cupric oxide, or activated copper, and these may contain other metals or metal oxides. Further, it is also possible to use silica, alumina, ion exchange resin, activated carbon, etc., in which these copper compounds are supported.
Activated copper means activated copper oxide obtained by activating copper oxide with an alkali in an aqueous formaldehyde solution. Further, the temperature at which formaldehyde is decomposed and removed is 30°C to 80°C, preferably 60°C to 75°C. In addition, either the batch method or the distribution method can be adopted as this decomposition removal method, but in the distribution method, the rate at which the formaldehyde-containing aqueous solution is distributed to the copper compound is 50 hr ^-1
The following is sufficient, preferably 1hr ^-1 to 10hr ^-1
It is. The copper compound is gradually reduced during use, and eventually loses its ability to decompose formaldehyde, but the reduced copper compound can be activated and reused by heating it in the presence of air at a temperature of 200°C or higher for over 1 hour. can do. By implementing the present invention, an aqueous solution obtained by removing phenols and formaldehyde from an aqueous solution containing phenols and formaldehyde contains methanol produced during formaldehyde removal. If the concentrations of formaldehyde and methanol contained in this aqueous solution are low, it can be further treated with activated sludge to form a completely purified aqueous solution and reused as industrial water. When the methanol concentration is high, the aqueous solution can be distilled to recover methanol and reused. Compared to conventional methods, the present invention is a method for removing phenols and formaldehyde from an aqueous solution containing phenols and formaldehyde, and is economical and simple, and can be recovered and reused as a resource. From this point of view, it can be said to be an extremely effective method. The present invention will be specifically explained below using examples. In addition, % in Examples means weight %. Example 1 Phenol resin wastewater (PH6.8, COD22%) containing 4.5% phenol, 11.7% formaldehyde, 7% methanol and 500 ppm of amines (PH6.8, COD22%) 40
The solution was passed through a 160 mmφ x 1000 mmL stainless steel column packed with anion exchange resin KEX-212 "manufactured by Koei Chemical Industry Co., Ltd." 11 at a passing rate of SV = 1.5 hr ^-1 . The composition of the treatment liquid was as shown in Table-1.

[Table] Next, 2574 g of caustic soda (0.55 times the mole of formaldehyde) was added to this treatment solution 30, and then 28 mmφ
When the liquid was passed through a 300 mmL stainless steel column at a temperature of 72°C and a flow rate of 5 hr ^-1 (500 ml/hr) for 60 hours,
The results shown in Table 2 were obtained.

[Table] Furthermore, 550g of treatment liquid 5 shown in Table-2 was distilled.
of methanol was recovered. The methanol concentration in the treated solution after methanol distillation was 0.01%, and the COD was measured to be 6500 ppm. Example 2 Wastewater containing 4.5% formaldehyde, 3.0% cresol and 0.05% mirabilite (PH5.0, COD 90800ppm)
8, strongly basic anion exchange resin Amberlite IRA-400 (manufactured by Rohm and Haas) 2
The liquid was passed through a 60 mmφ x 1200 mmL stainless steel column packed with the solution at a flow rate of SV=1.5 hr ^-1 . The composition of the treatment liquid was as shown in Table 3.

[Table] Next, 157.5 g of caustic soda (0.525 times the mole of formaldehyde) was added to this treatment solution 5, and then 28 mmφ
When the liquid was passed through a 300 mmL stainless steel column at a temperature of 65°C and a flow rate of 7 hr ^-1 (350 ml/hr) for 14 hours, the following results were obtained.
The results shown in 4 were obtained.

[Table] Furthermore, 91 g of methanol was recovered by distilling the treated solution 4 shown in Table 4. The COD in the treated solution after methanol distillation was measured and found to be 2100 ppm. Example 3 Using 10 phenolic resin wastewater (PH 5.0, COD 17.7%) containing 7.50% phenol, 0.98% formaldehyde and 3.70% methanol and 5 phenol extractants isopropyl ether, the volume ratio of waste water and isopropyl ether was 2: When phenol was removed using a continuous extraction column in step 1, the composition of the raffinate was as shown in Table 5.

[Table] Next, put this raffinate 1 into a four-necked flask,
9.6 g of caustic potash (0.525 for formaldehyde)
mol) and various copper compounds shown in Table 6 below were added, and the temperature was maintained at 60°C for 1 hour while stirring. The composition of the treatment solution and the COD of the solution after methanol was distilled off from the treatment solution were measured. Table 6 shows the results.

[Table] Example 4 The same phenolic resin wastewater as in Example 1 was used, and as extractants for phenols, benzene, octyl alcohol, 4-propylphenylpyridine-xylene (30%-70%) mixed solution, and butyl acetate were used. , methyl isobutyl ketone, tributyl phosphate (TBP), trioctylamine-xylene (20%-80%) mixed solution, trioctylphosphine oxide-paracymene (20%-80%)
Phenols were removed by batch extraction using the mixed solution, and the composition of the treated solution was as shown in Table 7.

【table】

[Table] 〓Operation method〓 After thoroughly stirring the extractant and waste water in a container, separate the liquids and repeat the extraction of the raffinate phase with fresh extractant.
Caustic soda (0.525 times the number of moles of formaldehyde) was added to each of these treatment solutions to oxidize the second
20ml of copper slices was packed into a 10mmφ x 300mmL stainless steel column, and the treatment temperature was 70°C and the liquid flow rate was 5hr ^-1
ml/hr) for 10 hours, the results shown in Table 8 were obtained. Table 8 also shows the results of measuring COD after distilling off methanol in each treatment solution.

[Table] Example 5 The same phenolic resin wastewater as in Example 1 was mixed with 1.5
High porous resin Amberlite XAD-4 used
(manufactured by Rohm and Haas) 30mm filled with 0.5
Liquid passing speed SV through φ x 1200mmL stainless steel column
The solution was passed for an hour of = 15 hr ^-1 . The treatment liquid composition is shown in Table-
It was as shown in 9.

[Table] Next, 86.1 g of caustic soda (0.525 mole times the number of moles of formaldehyde) was added to 1.5 of this treatment solution, and then 10 mmφ
When the solution was passed through a 300 mmL stainless steel column at a treatment temperature of 65°C and a pass rate of 3 hr ^-1 (60 ml/hr) for 25 hours, the results shown in Table 10 were obtained.

[Table] Next, distill the treatment liquid 1 shown in Table 10 and make 101g of it.
of methanol was recovered. The COD of the treated solution after methanol distillation was measured and found to be 3700 ppm. Example 6 An aqueous solution containing 0.3% dinitrocresols and 0.5% formaldehyde was added to an anion exchange resin.
KEX-212 [manufactured by Koei Chemical Industry Co., Ltd.] 30 filled with 400ml
Liquid flow rate through mmφ x 2000mmL glass tube column
Fluid passage was performed using SV3hr ^-1 . The composition of the treatment liquid is shown in Table 11.

[Table] Next, after adding caustic soda (0.55 times the molar amount to formaldehyde) to this treatment solution, a 28 mmφ x 300 mm L stainless steel column filled with 100 ml of cupric oxide was heated at a temperature of 72°C and a flow rate of 5 hr ^-1 . When the liquid was passed for a period of time, the results shown in Table 12 were obtained.

[Table] Example 7 After adding 208.8 g of caustic soda (1.3 times the mole of formaldehyde) to the treatment solution 1 after phenol removal shown in Table 1 of Example 1, 10.64 g of cupric oxide was added and stirred. While at a temperature of 65℃ 1
Holds time. The formaldehyde concentration and methanol concentration of the treated solution were measured. The results shown in Table 13 were obtained.

【table】

Claims (1)

[Scope of Claims] 1. When removing phenols and formaldehyde from an aqueous solution containing at least phenols and formaldehyde, 1. The phenols are removed using an extractant or adsorbent for phenols; 2. The treated solution 1. A method for treating an aqueous solution containing phenols and formaldehyde, which comprises bringing the formaldehyde contained therein into contact with a copper compound in the presence of an alkali to decompose and remove the formaldehyde mainly into formate and methanol. 2. The method according to claim 1, wherein the aqueous solution containing phenols and formaldehyde is phenolic resin wastewater. 3. The method according to claim 1, wherein the extractant for phenols is an organic extractant. 4. The method according to claim 3, wherein the organic extractant is an ether having 6 or more carbon atoms, an ester having 6 or more carbon atoms, or a tertiary amine having 10 or more carbon atoms. 5. The method according to claim 1, wherein the phenol adsorbent is an anion exchange resin or a high porous resin. 6. The method according to claim 5, wherein the anion exchange resin has a pyridine skeleton structure in its main chain. 7. The method according to claim 1, wherein the copper compound is cuprous oxide, cupric oxide, or activated copper. 8. The method according to claim 1, wherein the copper compound is cupric oxide, activated copper, or the like supported on silica, alumina, ion exchange resin, or activated carbon. 9. The method according to claim 7 or 8, wherein the copper compound is a mixture with another metal compound containing at least copper.