SU865123A3 - Method of phenol extraction from waste water - Google Patents

Abstract

1480018 Semi-permeable membrane separation MONSANTO CO 4 Aug 1975 [5 Aug 1974] 32502/75 Heading B1X A process for separating a phenolic material from an aqueous mixture containing it comprises contacting the mixture with a first surface of a non-porous organic polymeric membrane selectively permeable to the phenolic material and maintaining the other surface of the membrane under conditions such that the phenolic material has a lower chemical potential there than at the first surface, so that at least a portion thereof permeates into and through the membrane. The low chemical potential may be brought about by maintaining the second side of the membrane at reduced pressure or by contacting it with a solvent or reagent for the phenolic material. The membrane may be a sheet supported by mesh, porous metal, porous polymer or ceramic in a plate-and-frame press, or a hollow tube or fibre.

Description

(54) METHOD FOR ISOLATION OF PHENOLS FROM SEWAGE WATER

one, ; . . .

The invention relates to a process 4 for wastewater treatment, in particular to methods for separating phenols from wastewater streams. 5

A known method for the separation of phenols from wastewater contaminated with pheno-. It consists in that the wastewater is treated with a mixture of a solvent of phenols containing carbon-10 prenatal of the aromatic series, and from. dehydroabiethylamine, and phenols. dissolved in a solvent, and the mixture is discharged from wastewater 1.

However, this method is not sufficiently effective, especially with a low content of phenol in the feed stream. The result of the methods of selective eq. It often consists in replacing one solvent with another, as a result of which it is constantly necessary to isolate phenol from the mixture or solution. In many cases, these mixtures ,. for example a mixture of phenol - water, form azeotropic mixtures. Since these 25 azeotropic mixtures form vapors with the same composition as the liquid, the individual components of the mixture cannot be isolated by ordinary distillation methods. .thirty

Closest to the present invention, there is a method for separating phenol from dilute wastewater, which is carried out with the penetration of a liquid emulsion in the form of droplets through a membrane. In order to carry out the process of continuous processing in this method, it is required to separate and regenerate the organic liquid of the membranes of the material containing surfactant 2.

The aim of the invention is to simplify the method of separation of phenols from wastewater.

This goal is achieved in that the method involves passing a wastewater stream through a membrane, which uses an organic hydrophobic polymer membrane selectively permeable to phenols, on one side of which is a purified stream of water with a pH of 1-5, and on the other - a solution consisting of phenol solvents or a complexing agent solution.

It is preferable to use a membrane selected from the group consisting of polyethylene, nylon, aether, polyethylene, polybutadiene, polyvinyl fluoride, natural rubber, ethylene-vinyl acetate copolymer, ethylene-tetrafluoroethylene copolymer, polyisoprene, chlorotrifluoro ethyrene, and a pattern for an organic hydrophobic polymer membrane. and tetrafluoroethylene, urethane and methyl silicone resins.

Phenols are separated from streams of water containing various concentrations of phenol by bringing streams of water containing phenols in contact with the first side of an organic hydrophobic polymer membrane that is selectively permeable to phenols, maintaining the reverse side of the membrane at a lower chemical potential than before the membrane, chemically, part of the phenols penetrate into and through the membrane, and a mixture is formed behind the membrane that has a higher concentration of phenols than the flow of water.

To maintain a lower chemical potential behind the membrane, a solution is used which may be potential phenol solvents and / or phenolic complexing solutions.

The continuity of the process is achieved by the fact that the flow of water passes through one side of the selective membrane, with which it is in contact, and there is a solution with a lower chemical potential on the other side of the membrane.

A lower chemical potential, a solution of phenol solvents and a stream of water containing phenols provide a force that absorbs phenols through a selective membrane in order to enrich the solution with phenols. The solution is enriched with phenols, i.e. phenolic components, solvents or steam can be physically further processed and thus facilitated the recycling of solvents or complex solutions

For each stage, the separation efficiency is indicated by a separation factor, which is defined as the ratio of the concentration of two separated substances A and B divided by the ratio of the concentration of the corresponding substances in the medium after passing through the membrane:

 (- after passing through the membrane)

If -. .

 before passing

through the membrane) de c and Cg - concentration preferably passing

component and any other component of the mixture or the sum of other components, respectively.

The expression chemical potential refers to the propensity of a substance to transition from any phase to another. For an ideal vapor or gas, this tendency is equal to the partial pressure, as a result of which it fluctuates. (Significantly depending on the changes in the total pressure. In a liquid, the change in the tendency to transition to another phase, as a function of the total pressure, is small.

The tendency to transition to another phase of a liquid always depends on temperature and concentration. The delivery substance is usually a liquid solution, and the other side of the membrane is supported so that there is a vapor or liquid phase. The substance can be supplied in the form of steam, if the divided mixture is obtained in this form as a result of an industrial process or if it is necessary to save heat during multi-stage processing,

In this process, the first or the supply side of the membrane is brought into contact with the phenol-containing stream of water in the liquid phase, and the other side of the membrane with the solvent of phenol or a solution of a complexing agent. However, the feed stream of water may be in the vapor phase, and it is preferable when the first side of the membrane is under positive pressure compared to the second side. In order to realize the flow of phenols, a chemical potential gradient between the two zones and, i.e. between the supply (first) side of the membrane and the second side. The chemical potential in the supply zone must be higher than the chemical potential in the second zone of the membrane. Under these conditions, part of the phenols in the feed stream of water dissolves in the membrane and passes through it.

The extent of the passage is that the phenol containing feed stream of water in the liquid or vapor phase is brought into contact with the membrane and the fraction enriched with phenols is collected on the other side. membranes. The fraction passing through the membrane is a phenol vapor, a solution of phenol, or a solution of phenol complexes. To facilitate the rapid passage of phenols, the chemical potential of the passed phenols on the surface of the membrane to the second side can be kept low by quickly removing fractions containing phenols, for example, by a continuous process in which enriched phenol Fp, a phenol solvent or a solution of phenol complexes are constantly removed and replace the non-enriched HfcOM with a solvent and / or complexing agent.

Solutions used on the second side of the membrane include solvents of phenols or solutions of phenolic complexing agents or a mixture of them. Suitable solvents for phenol phenols are solvents in which the total concentration of phenolic substances on the second side of the membrane is higher than on the first supply side.

In tab. Tables 1 and 2 list suitable solvents.

Solutions of complexing agents for phenols suitable for use on the second side of the furniture are, for example, those complexing agents that, when dissolved, allow one to study the total concentration of the phenolic parts on the second side higher than on the first or feeding side of the membrane. Complexing agents, such as alkaline earth and alkali metal hydroxides, form easily phenols in dissolved form and are sufficient for use on the second side of the membrane. Different concentrations of solutions can be used, for example, sodium hydroxide, potassium hydroxide, etc., but it is necessary that the solutions are combined with the membrane and do not cause swelling, rupture OR, other physical defects during operation and do not penetrate to the membrane to a significant extent.

Phenols should be understood to mean aromatic organic compounds in which one or more hydroxy groups are directly bound to a benzene ring, for example, phenol, cresols, cumylphenols, nrnylphenol, XYLONOL, resorcinol, naphthols, and the like, as well as substituted phenols.

The flow of water can be supplied continuously or intermittently to the supply zone of the membrane. Phenols that have passed through are removed from the opposite side in portions or in a continuous manner, using different removal media, such as steam, solutions of complex formation agents or solvents. The flow rate of the water flow and the removal rate of the passed fraction can be adjusted so as to obtain the required ratio of passing and passing fractions. Multiple stages can be applied and both of these fractions can be recycled to different stages. In each passage zone, a membrane can be applied in the form of sheets, tubes, empty fibers or other structures that preferably provide the maximum area of the membrane surface with minimal dimensions.

The absolute pressures in the inlet (first) and outlet (second) side zones can vary significantly. T1 can be applied negative and positive pressure ranging from a few millimeters of mercury to 35-70 kg / cm- or more, depending on the strength of the membrane and the conditions of release.

If there is a liquid phase in the exit zone, pressure does not play an important role. However, if gaseous or vaporous feed mixtures are used, an increase in pressure in the feed zone may cause a higher chemical potential.

The penetration through the membrane is carried out in a large temperature range in the range of about 0-150 s or more, depending on the application.

Phenols, solutions and water temperature of the feed mixture. Often, elevated operating temperatures are necessary due to increased penetration rates.

5 The permeable membrane used is non-porous, i.e. free from holes, cracks, etc. that destroy the integrity of the membrane surface.

JQ Useful membranes consist of an organic hydrophobic polymeric material. Membranes should be as thin as possible and have sufficient strength and stability.

e for use in the penetration process. Membranes of a thickness of 2.54x10 -0.0381 cm or slightly larger are usually used. High penetration rates are obtained with thin membranes that can be supported, for example, with fine wire mesh, grill, porous metal, porous polymers and ceramic materials. The membrane may be a simple disk or a sheet of membrane material, suitably installed on a pipeline or pipe, in an equal or plate filter press. Other forms of membranes can be used, for example hollow

0 pipes and fibers through which or

around which the feed stream is fed or recirculated and the phenol passed through is removed on the other side of the pipe as a solution or complex enriched with phenols. In industrial

5 devices can use membranes of other shapes and sizes. Polymeric membrane contacts can be linear or crosslinked, and their molecular weight can

0 fluctuates in a large range.

The membrane must be insoluble in an aqueous medium, in various solvents or complexed: with their reagents used 5 to remove the Phenols. By membrane insolubility it is understood that the membrane material does not dissolve if the substance of the solvent is dissolved in the solvent or in the aqueous mixture to such an extent that it takes on rubber-like properties that can cause plastic deformation and destruction under working conditions. , the inclusion of high awl. The membranes used can be prepared in a known manner, for example, by casting a film or spinning hollow fibers from a mixture containing an organic polymer and a solvent. The control of the separation capacity of a specific organic membrane is carried out by the method used to form and cure the membrane, i.e. by casting from a & ps into a controlled gaseous environment or from a solution with different concentrations and temperatures. The membrane must be thin enough to allow penetration, but also thick enough to prevent destruction under operating conditions. The membrane must be selectively permeable to phenols 25 compared with other components of the feed stream of water or absorbing solutions and complexing agents.

Examples 1-5 illustrate the use of different membranes, provided that there is a liquid on both sides, the results and conditions are given in table. 3 (penetration from the liquid into the liquid of 1% phenol in water,, tributyl phosphate as a solution on the second side of TBP, saturated with water).

Separation of phenol from water streams using a selective membrane in the presence of a solution on the second side of the membrane has advantages over direct liquid extraction of the liquid, since the solvent is in solution and emulsification is generally prevented. 5 tests of six solvents suitable for release of phenols by passage through the membrane, which are listed in table. 4. The minimum value of the separation factor (K) for JQ phenol between water and solvents is 10 and remains unchanged in the range of 1-7% phenol for all solvents. K is calculated assuming that the volumes of the components are completely additive; the solubility of 1WODY in solvents is negligible; the density of the phenol component passed is uniform; the solubility of the solvent in water is so low that FY can be neglected. tO

Examples 6-12. The flow of industrial wastewater, having approximately the following composition, weight -.%: NaCl9,3

Water35,565

Ethers 2.5

Phenols 2.7

treated with concentrated, i.e. 37% HCl, to obtain a pH of 4.2. When the pH is lowered, the phenolic derivatives are released and a clear liquid remains. This clear liquid is used as a water feed for Examples 6-12, which are listed in Table. five.

The feed water contains approximately the following ratio of phenols, ppsh:

Methylpyrrolidone 420

Phenol15,600

Cumylphenol 180

Nonylphenol 20

The pH of the samples of the two feed-containing phenols was adjusted to 1-2 with hydrochloric acid, and the samples were precipitated. The passage is carried out with both of the resulting clear floating liquids using 30% NaOH and 40% sodium phenate plus G0% NaOH as solvent. The first stream contains phenol, cumylphenol, Nonylphenol, partial esters and salts. The second stream contains phenol, butyl alcohol, partial esters and salts. Low-density polyethylene with a thickness of 0.00254 cm is chosen as the material for the membrane.

Example13. Aqueous feed stream, content 1.8 wt. % phenol is treated by the method described and it is found that the permeability (P) of the system is 2

8.8 X CM / CM.c (AVF) and is the same for both main solvents, supplying the pH nesmeiyen after 150 hours (UVF is the difference in the volume fraction used to denote the diffusion force; all densities are taken per unit). After this time, the phenol content is reduced from the initial value of 18.300 to 200-300 Rrga and the content of nonylphenol and cumylphenol is less than 10 ppm. IP will be the same when using 30% NaOH as a solvent. In each case, the film remains intact and in .pactBOpax there are no solids or only a small amount at 70 C.,

EXAMPLE 14 A water feed stream containing 0.75% by weight of phenol is treated according to the conditions described and the permeability of the system is found to be

9.5 x 108 cm-cm / cm c (AVFj, the pH does not change, and the phenol content decreases from 7500 to 200 ppm in .150 h (DOUR is the difference in volume; the fractions used to denote the diffusion force are all unit). Solutions are crystal clear at 70 ° C. Films are strong, but when 30% NaOH is used, there is a slight dotting, rupture and other use of phenol with NaOH reveals severe damage. Obviously, a certain film is damaged, because repetition of the reaction with the use of a new film and solvent of phenate and NaOH No traces of damage to the polyethylene film were detected for 120 hours. The film immersed in the second feed stream for 360 hours was left to exalted and had no signs of damage. In Examples 15-27 listed in Table 6, the results of experiments with different membranes, feed streams and concentrations of sodium hydroxide in the complexing solution, the pH of the aqueous phenolic feeds was adjusted to about 2-4 and did not change during the passage. The flow rate of caustic soda does not vary, however, small amounts of NaOIJ and water penetrate during the selective passage of phenols. Testing of the membrane to penetrate from different types of polyethylene and one type of siloxane carbonate. Results are given in P {eimera 28-33 in tab. 7 (all feed streams contain about 1% phenol in water, the pH is set to 1). Hollow fibers made of low density polyethylene are used to selectively transfer phenols from liquid to liquid. Examples 34-42 in the table. 8 shows and compares the use of flat, films and hollow fibers of two low density polyethylene polymers. 8 Examples 34-42 apply feed. stream containing 3 wt. % phenol, 97% w / w water, and a 40% sodium hydroxide solution is used on the second side of the membrane. Given in Table. 8 the results show that the selective membrane can be applied in any physical form, for example in the form of a hollow fiber. Table

0.66

1-Methylnaphthalene Simple Diphenyl-C (cf) (, / (Cp JK, moreover, c is the concentration of the (aqueous) phase, g / cm

Table 2

0.411

1.60

Lower phenol in O (organic) and

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The melt index is P 126 30, the melt index is P 127 55. P is the intrinsic permeability coefficient, which should be independent of the thickness and shape of the membrane, if it is calculated by assuming an isotropic structure. The defining relations are OD - the outer diameter of the hollow fibers and ID - the inner diameter. For films and fibers, PdDV, where I is the flow of phenol, g / cm-s and & volume fraction (equal to the weight fraction, if the density is the same) of the diffusional strength of the phenol.

For films Р Рд-1, where 1 - membrane thickness.

For fibers, P (Pd / 2) / (ID) ln (OD / lD), where Pd is expressed on the basis of the fiber ID and In is the natural logarithm.

Claims (2)

Invention Formula 1, Method for separating phenols from wastewater by passing through a membrane, which is based on the fact that, in order to simplify the method of separation, an organic hydrophobic polymer membrane selectively permeable to phenols is used as a membrane, on one side of which there is a stream to be cleaned. water with a pH of 1-5, and on the other - a solution consisting of phenol solvents or a complexing agent solution. 2. The method according to claim 1, is also distinguished by the fact that, as an organic hydrophobic polymeric mem table, 2 branes are used to choose from resin. Sources of information taken into account in the examination 1, US Patent No. 2808375, kl.210-21, published. 1957. 2. The patent of the USA 3617546, kl.210-21, published. 1971 (prototype).