CS269582B1 - i Waste Cleaning Purpose - Google Patents

Abstract

Sewage treatment containing one Cg aromatic hydrocarbon. to C, or a mixture of aromatic hydrocarbons with Cík-Cg chlorinated hydrocarbons, is a liquid-liquid extract wherein the extracting agent is an aliphatic hydrocarbon or a mixture of predominantly aliphatic hydrocarbons having a boiling point of from 20 to 350 ° C; The mole ratio of the extractant to the purified water is 1: 2 to 50. The extraction agent may also contain non-toxic antioxidants (2,4-di-tert-butyl-4-methylphenol). The phases are separated while the extract is generally led to the recovery of the extractant.

Description

The invention relates to a method for purifying waste waters containing at least one chlorinated hydrocarbon C1 to C8 and/or at least one aromatic hydrocarbon C8 to _C12 by extraction using technically available and easily regenerable extraction reagents.

Chlorinated hydrocarbons and aromatic hydrocarbons can occur in wastewater in both dissolved and ethylene glycol forms; in extreme cases, they can form a more or less continuous layer on the surface of the wastewater. These need to be removed from wastewater at least to a significant extent, not so much for technical and economic reasons (recovery of chlorinated hydrocarbons and aromatics) as for ecological reasons. Chlorinated hydrocarbons, such as 1,2-dichloroethane, dichloroethylenes, chloroform, carbon tetrachloride, but also trichloroethylene and perchloroethylene and, from the aromatics, mainly benzene, are relatively highly toxic and, moreover, are only very slowly biodegradable.

Relatively widespread methods of refining waste waters from chlorinated hydrocarbons include adsorption either only on activated carbon or additionally on synthetic resins - ion exchangers, such as Amberlite XAD-4, and subsequent desorption with water vapor or air /Dummer G., Séhmidhammer L.: Chem. Ing. Tech. 56. 3, 242 (1984); Chem. Industrie £6, 5, 294 (1984); Grťlnwald A.: Ropa a uhlie 22, 46 (1987); Kočetkova R. P. et al.: Chim. promyšl. δ. 3, 148 (1984)/. The problem, however, is the relatively low capacity of adsorbents. A similar situation is also with the combination of the adsorption effects of activated carbon and the biological stage of wastewater treatment /Stover E. L. et al.: Ozone Sci. Ihg. 1985, 7(3), 195; published application for invention NSR 3 418 074; jap. pat. 86-200 837; Chem. Abstr. 106. 39510 u (1987)/. Powdered coal in activated biological sludge captures toluene and 1,2-dichloroethane, while toluene is biodegradable. Ozonization of purified water enables biological degradation of hydrocarbons captured in this way. Optionally, adsorption on activated carbon is combined with adsorption on Fuller's clay or other microporous sorbents /Saburina E. B. et al.: Ž. fiz. chim. 60 (12), 3038 (1986)/. These methods are so suitable - . more suitable for finishing”. Interesting, but technically and energy-intensive is the removal of chlorinated hydrocarbons from wastewater by desorption / Petrova N. I; et al.: Chim. promyšl. No. 3, 149 (1982); USA pat. 4 544 488; Tomita Sh. et al.: Chem Abstr. 104, 155 583 g (1986), or by stripping, usually with air. Also interesting is the extraction of 1,1,1-trichloroethane and chloroform from wastewater with a non-aromatic paraffinic fraction with a boiling point of 180 to 220 °C /Austrian pat. 373 858 (1984)/, as well as extraction using extraction agents, such as typical oxygenated organic solvents /Earhart J- P. et al.: Chemical Engng. Progress (CEP) 2, 67( 1977)/, which are however technically difficult to regenerate and are also relatively highly soluble in water. Then oxidation with air at a temperature of 500 °C in a reactor filled with limestone, further oxidation with air or ozone at a temperature of around 20 .°C in the presence of ferrous sulfate or hopcalite /Sidorenko J. K. and others: Dokl. AN Ukraj. SSR, ser. B, Geol. Chem. Biol. Nauki 10 (1982); Ropa a uhlie 29.46 (1987)/, or a combination of oxidation of organic substances in water using ozone and ultraviolet radiation with the co-action of hydrogen peroxide as a catalyst or initiator /Masten S. J. and others: Ozone, Sci. Ihg. 8(4), 339(1986)/ is used. However, the energy the complexity of these methods and, in cases of the presence of inhibitors of free radical reactions in wastewater, low refining efficiency.

However, according to the invention, the method for purifying wastewater containing at least one aromatic hydrocarbon Cg to 0θ or a mixture of at least one aromatic hydrocarbon with at least one chlorinated hydrocarbon C^ to Cg is carried out by hydrocarbon extraction, in which at least one aromatic hydrocarbon or a mixture of at least one aromatic hydrocarbon with at least one chlorinated hydrocarbon is extracted from the wastewater by at least one-stage liquid-liquid extraction, by treating with an aliphatic hydrocarbon or a mixture of predominantly aliphatic hydrocarbons from the boiling range of 20 to 350 °C and/or predominantly dialkylbenzenes with a boiling point of 180 to 350 °C, at a weight ratio of extraction agent to purified water of 1:2 to 50, optionally with a content of 0.1 to 5% by weight, anti-

CS 269 5β2 Bl oxidant, such as 2,6-ditert. butyl-4-methylphenol, 2, 6-dimethyl-6-alkylphenol·.: and tris-(2.A-(1-phenylethyl)phenyl)-phosphite, with subsequent separation of the liquid phases. In this case, the extract is generally directed to the regeneration of the extraction agent.

The advantage of the wastewater treatment method according to this invention is the high partition coefficient, or rather the high refining efficiency of the extraction agents, the possibility in one technological stage to extract from wastewater not only chlorinated but also aromatic hydrocarbons and even simultaneously admixtures of other organic substances, such as propylene chlorohydrin, dichlorodiisopropyl ether, propylene oxide, etc. The higher effect is in the minimal energy consumption for extraction and the easy regenerability of both the extraction agents and chlorinated and aromatic hydrocarbons. Last but not least, the fact that the water refined in this way can usually be discharged into streams or retention tanks without further treatment.

According to the present invention, wastewater containing at least one chlorinated hydrocarbon is refined, such as 1,2-dichloroethane, 1,1,1-trichloroethane, tetrachloroethene, pentachloroethane, hexachloroethane, dichloroethylenes, vinylidene chloride, trichloroethylene, perchloroethylene, chloroprene, mixtures of chlorinated hydrocarbons from the production of dichloroethane and vinyl chloride, chloroprene, chlorofluoroolefins. Then chloroform, methylene dichloride, tetrachloromethane, as well as chlorofluoromethanes. They may also contain at least one aromatic hydrocarbon C, to C ₀ , OO, mainly benzene, toluene and xylenes, ethylbenzene, trimethylbenzenes and styrene. Most often they contain mixtures of chlorinated hydrocarbons with aromatics.

Last but not least, the wastewater may also contain admixtures of other organic compounds, such as propylene chlorohydrin, dichlorodiisopropyl ether, dichloromethyl ether, olefin oxides, propylene glycol, dipropylene glycol and other organic compounds, especially oxygenated and chlorinated organic compounds.

For reasons of easier isolation of extracted chlorinated and aromatic hydrocarbons from extracts, as well as regeneration of extraction agents, it is more suitable to use agents differing t. v. from extracted chlorinated and aromatic carbon by 20 to 200 °C, but preferably by 40 to 100 °C. In this case, a suitable extraction agent is petroleum ether, further fractions of light primary gasoline or heavy primary gasoline. Then mainly dealomatized kerosene fraction, but also fraction of diesel fuels, or. light gas oil. Particularly suitable are n-alkanes obtained by dealkalanization of petroleum fractions by adsorption methods, i.e. using molecular sieves, but also hydrocarbon fractions from products of hydrocracking of petroleum vacuum distillates, etc.

Extraction is carried out using conventional extraction equipment.

The separation of liquids - extract and refined water (raffinate) is most often carried out by settling or centrifugation.

The extract is usually used to isolate the extracted aromatic and chlorinated hydrocarbons and regenerate the extraction agents, usually by distillation and rectification. In the case of using hydrocarbons with a high boiling point (but also freezing point) as extraction agents, selective crystallization can also be used for their regeneration.

If the raffinate, i.e. the refined wastewater, needs to be practically completely freed from impurities, this can be done additionally by adsorption, e.g. on activated carbon with subsequent biological degradation, possibly also under the interaction of oxygen, oxygen oligomers and ultraviolet radiation, further by adsorption on hydrophobic aluminosilicate carriers, possibly with biological addition, etc.

However, wastewater treated according to this invention is generally of a purity suitable for discharge into watercourses, retention tanks, etc.

cs:269í 582 Bl

In cases of large quantities of extracted chlorohydrocarbons from wastewater, also to prevent corrosion of equipment by wastewater and extracts containing chlorohydrocarbons, it is appropriate to add non-toxic antioxidants to the extraction agents, such as 2,6-di-tert. butyl-p-cresol, 2,6-dimethyl-4-alkylphenol, tris~/2,4-(1-phenylethyl)phenyl/-phosphite, etc.

The refining process according to the present invention can be carried out batchwise, semi-batchwise and continuously.

Further details on the implementation of the method, as well as further advantages, are apparent from the examples.

Example 1

For extraction, water from the plant premises was used, containing 0.2138% by weight of 1,2-dichloroethane (DCE) and 0.019% by weight of benzene, 27.2 g of this waste water was placed in a separating funnel and 2.99 g of petroleum ether fraction, with a distillation range of 20 to 40 °C, were added to it. The separating funnel was closed with a well-ground stopper and the mixture was shaken intensively for 15 min. Then it was allowed to sediment at a temperature of 20 °C for 2 h. A sample was taken from the lower aqueous phase and analyzed by gas-liquid chromatography ((Chrom 4) using a column of 3 mm diameter, 3,700 mm length, filled with Chromaton NAW, on which 10% FFAP of the anchored phase was applied. Nitrogen was used as a carrier gas at a working temperature of 140 °C. The determined DCE content in the aqueous phase of the extraction was 0.0393 wt%, and benzene 0.0012 wt%. The DCE content in the hydrocarbon phase was determined from the balance to be 1.649 wt%, and benzene 0.1670 wt%.

Distribution coefficient in _ % wt. DCE in the hydrocarbon phase .. · ^DCE % wt. DCE in the aqueous phase ⁴ ' ^{? and} benzene"

Example 2

In a similar manner to Example 1, a mixture containing 0.4 wt. % DCE in water was extracted. 27.0 g of the above-mentioned DCE mixture and 3.0 g of petroleum ether fraction were placed in a separatory funnel for extraction. After extraction, 0.07.7 wt. % DCE was determined in the aqueous phase. The DCE content in the hydrocarbon phase was 2.8719, which corresponds to a partition coefficient of 40.05.

Example 3

Water from the plant object with the composition as in Example 1, in the amount of 27 g, was extracted with n-alkanes C1-C20 _in the amount of 3 g at room temperature. After phase separation, the aqueous phase 4 I 8 contained 0.0364 wt. % DCE and the hydrocarbon phase 1.5723 wt. % DCE.

Distribution coefficient KpQg ⁼ 43.2.

Example 4

Water from a plant object with the composition as in example ', in the amount of 27.04 g, was extracted with i-alkenes C in the amount of 3 g at room temperature. After phase separation, the aqueous phase contained 0.0366% DCE and the hydrocarbon phase 1.573'% by weight DCE. Partition coefficient K _DCE = 43.

CS 269 592 Bl

Example 5

Waste water containing 0.087 wt% trichloroethylene was placed in a separatory funnel in an amount of 27.09 g and 1-alkene-O,θ in an amount of 3.00 g was extracted. After extraction, the aqueous phase - raffinate contained 0.0111 wt% trichloroethylene and the hydrocarbon phase - extract 0.6812 % trichloroethylene.

Distribution coefficient £^$=61.4.

Example 6

Water containing 0.03% by weight of toluene in an amount of 54.05 g extracted 6.02 g of 1-alkenes C1-C4. After extraction, the raffinate contained 0.00195% by weight of toluene and the extract 0.2512% by weight of toluene.

Distribution coefficient K _T0L = 129. ₄

Example 7 l

Water containing 0.03% by weight of toluene in an amount of 54.05 g is extracted with 6.00 g of refined distillation residue from the production of dodecylbenzene, a fraction with a boiling point of 320 to 350 °C, a freezing point of -52 °C, containing mainly dialkylbenzenes with alkyls up to C,^ and diphenylalkanes (phenyls on alkane chains C ₎₀ to 0^) and with an admixture of 0.2% by weight of 2,6-di-tert.butyl-4-methylphenol and 0.05% by weight of tris~/2,4-(1-phenylethyl)phenyl/--phosphite, as antioxidants. After extraction! the raffinate contains 0.00051% by weight of toluene and the extract 0.2601% by weight of toluene.

Under otherwise similar conditions, but at a refined water temperature of 0.3 °C, the raffinate contains 0.00021 wt% toluene and the extract 0.2673 wt% toluene.

Claims (4)

SUBJECT OF THE INVENTION * 1. A method for purifying wastewater containing at least one aromatic hydrocarbon Cg to Cg or a mixture of at least one aromatic hydrocarbon with at least one chlorinated hydrocarbon Cj to Cg, by extraction with hydrocarbons, characterized in that at least one aromatic hydrocarbon or a mixture of at least one aromatic hydrocarbon with at least one chlorinated hydrocarbon is extracted from the wastewater by at least one-stage liquid-liquid extraction, by the action of an aliphatic hydrocarbon or a mixture of aliphatic hydrocarbons in the boiling range of 20 to 350 °C and/or dialkylbenzenes with a boiling point of 160 to 350 °C at a weight ratio of the extraction agent to the purified water of 1:2 to 50, optionally with a content of 0.1 to 5% by weight of an antioxidant, such as 2,6-di-tert. butyl-4-methylphenol, 2,6-dimethyl-4-alkylphenol and tris-(2,4-(1-phenylethyl)phenyl)-phosphite, and subsequent separation of the liquid phases, the extract being generally used for regeneration of the extraction agent. 2. The purification method according to item 1, characterized in that the extraction is carried out with a mixture of aliphatic hydrocarbons from the temperature range of 20 to 170 °C, and preferably 36 to 125 °C »and/or n-alkenes with a boiling point of 220 to 350 °C, and preferably 240 to 300 °C. 3. The purification method according to points 1 and 2, characterized in that the extraction is carried out with a mixture of aliphatic and cycloaliphatic hydrocarbons with a boiling point of 100 to 350 °C and/or dialkylaromatic hydrocarbons with a boiling point of 180 to 350 °C, preferably with a mixture of dialkylbenzenes with alkyls C ₁₀ to C 11 and diphenylalkanes, formed as a by-product in the production of alkylbenzenes. 4. A purification method according to points 1 to 3, characterized in that from wastewater containing a mixture of at least one chlorinated hydrocarbon with an aromatic hydrocarbon, these are extracted by the action of an aliphatic hydrocarbon or a mixture of aliphatic hydrocarbons, differing in boiling point from the extracted chlorinated hydrocarbon of the aromatic hydrocarbon by 20 to 200 °C, preferably by 40 to 100 °C.