CS269346B1 - Wastewater treatment process for anthrachnine dyes - Google Patents

Abstract

Wastewater containing anthraquinone derivatives substituted with an amino group in the alpha position and a sulpho group in the beta position is treated by the action of sodium dithionite and possibly formaldehyde in an alkaline medium. The dissolved anthraquinone derivatives form a solid precipitate which is separated. Up to 96% of the anthraquinone sulphocyanate content can be removed by this process.

Description

The invention relates to the reduction of the content of organic substances in wastewater after the production of dyes or intermediate intermediates which contain at least 1 anthraquinone nucleus and an amino group in the alpha position and a sulpho group in the beta position and do not contain further solubilizing groups in other molecules.

There are a number of methods for removing worms or reducing their circulation in wastewater, or for their discoloration, and it is described in numerous sources and patents.

One of the most common methods is the adsorption of bervives from solution on activated carbon, kaolin, montmorillonite, anthracite and the like. Another method widely used is electrolytic treatment. Other methods include extraction, gamma ray treatment, oxidation with oxygen, hydrogen peroxide, flocculation with ferric chloride or other reagent (cyrene chloride), ion exchange treatment, treatment with bentonite and polymeric coagulent, reduction with iron and sulphite, or treatment with special agents such as polyalkylene polyamines, guanylhydrazonium salts and the like.

Suitable treatment of wastewater containing alpha-aminoanthraquinone-beta-sulfonic acids is not described in the literature. As far as the processes described in the literature are concerned, the adsorption process using activated carbon is relatively expensive, moreover, due to the considerable solubility of anthraquinone sulfoic acids, perfect adeorption does not occur. Activated carbon with adsorbed dyes must be disposed of or regenerated and then the released soluble substances disposed of. Cheap adsorbents (kaolin, montmorillonite, anthracite) do not guarantee effective adsorption, they do not consider regeneration and thus with the deposition of these color-saturated adeorbents, environmental problems with leaching and penetration into the soil can arise. Regenerative adsorption methods produce dye concentrates which must be disposed of again. Good capture occurs on ion exchange adsorbents (annexes), while in the case of aminoanthraquinone sulfoic acids there is practically irreversible adsorption, thus degrading the relatively expensive preparation, which cannot then be regenerated. · Electrolytic wastewater treatment requires a sufficiently large current source and a special electrolyser. The investment costs in this way are therefore quite high. Extraction of aminoanthraquinone sulfonic acids requires an extractor, circulation of an expensive extractant, and separation of the aqueous and organic phases. In this case, the wastewater is contaminated with an extraction agent. Purification by oxidation with oxygen or another reagent (ozone, hydrogen peroxide) is ineffective here because said sulfoic acids are relatively resistant to oxidation or, if oxidized, their oxidation products are soluble.

Various special precipitating agents used to remove colorants from solution by chemical reaction are expensive and readily available. Flocculants such as ferric chloride, aluminum chloride, aluminum sulfate are commonly used. However, they are required in large quantities in order to achieve the desired effect in wastewater with concentrations. Increasing their amount for water treatment will increase the circulation of the oil, or even change the pH of the water.

The disadvantages of the above-mentioned processes are eliminated by the process according to the invention. It consists in adding to the waste water from the production of anthraquinone dyes which contain anthraquinone derivatives with at least one · anthraquinone nucleus · substituted in the alpha position by an amino group and in the beta position by a sulpho group, sodium dithionite in an amount of 1 to 2 l of Na ₂ S ₂ 0 ₄ no 1 eulfoakupine present in dissolved anthraquinone derivatives and the pH is adjusted to greater than 9 by the addition of an aqueous solution. This gives a reduced form which cleaves the sulphogroup and precipitates the anthraquinone derivatives. These can then be easily removed by conventional methods, such as filtration. ·

The process can be modified by adding, in addition to sodium dithionate, an aqueous solution of formaldehyde containing 1 to 2 moles of formaldehyde per 1-epofoupine present in the dissolved anthraquinone derivatives to the waste water to be treated under the same conditions. The reaction can take place at normal or elevated temperatures, the preferred order of addition of the components to the waste water is such that the addition of formaldehyde follows a batch of Na 2 S 2 O. · 2 2 4

The process according to the invention is illustrated in more detail in the following examples.

Example 1

To 1 L of wastewater after Ullman condensation of 1-amino-4-bromanthraquinone-2-sulfonic acid was added 5 g of N ₂ N ₂ O _{4 at 50 ° C. The slurry was} cooled and filtered at this temperature for 3 hours. 1.05 g of precipitate was obtained, i.e. approximately 93% of the anthraquinone sulfoic acid content originally contained in the solution. The absorbance of the solution decreased at a wavelength of 477 to 12.9 times, at 580 to 18.3 times, at 592 to 17.3 times and at 610 to 21.9 times.

Example 2

2.5 g of NagS ₂ 0 ₄ and 3. at 35 ° C 20 ml of 7% NaOH solution. It was stirred for 1.5 h until cooled and filtered. 1.79 g of organic substances were precipitated, i.e. 96% of their original content. The absorption of the solution decreased at wavelength 477 to 10.5 x, at 592 nm 3.4 x, at 610 to 3.03 x, at 638 to 6.75 x.

The advantage of the new process is the low and need for precipitating agents, which are easily available, while even lower quality substances can be used. The process can wipe off up to 96% of the aminoanthraquinone sulfocyeline content dissolved in the wastewater and obtain a precipitate in solid form. There is no need for other operations such as regeneration, disposal of concentrate and the like. By simple processes such as precipitation and filtration, it is thus possible to remove substances from the waste water which, due to their poor oxidizability and very good solubility, have withstood hitherto conventional separation processes.

Claims (1)

OBJECT OF THE INVENTION Process for the treatment of waste water in the production of anthraquinone dyes containing anthraquinone derivatives with at least one anthraquinone nucleus substituted by an amino group in the alpha position and a sulfoupine in the beta position, characterized in that the waste water is treated with sodium dithionite added in an amount of 1 to 2 moles per liter. eulfo group present in the dissolved anthraquinone derivatives and optionally with aqueous formaldehyde solution, subsequently added in the same solar amount relative to the sulfo groups present, the pH is adjusted to more than 9 with sodium hydroxide solution and the precipitate formed is separated.