JP2005538268A - Treatment of dye baths with a membrane process for reuse of water and NaCl in the process - Google Patents

Abstract

The present invention relates to a method for treatment and recovery in the value of a bath for dyeing cellulose fibers with reactive dyes including prefiltration, neutralization, nanofiltration and reverse osmosis. The following will be reused after the treatment is finished: on the one hand to colorless water containing the inorganic salts necessary for the new dyeing with reactive dyes; on the other hand, some pure water may be used during nanofiltration or other activities Used for either. For example, the dyed material is washed or rinsed. In addition, a very low volume of aqueous solution is recovered, mainly containing hydrolyzed reactive dyes and dye additives. This, in essence, in saving water, drastically reducing wastewater salinity, and environmental pollution, treating cotton dyed with reactive dyes, simplifying the treatment of wastewater from other baths required, Environmental destruction can be significantly reduced.

Description

  The present invention relates to a method for treating a bath for dyeing cellulose fibers with reactive dyes, including prefiltration, neutralization, nanofiltration and then reverse osmosis.

  It is the exhaustion of cotton with reactive dyes that consumes the most water of any fiber currently dyed and releases an aqueous liquid filled with the greatest amount of different types of pollutants at the end of the cycle. is there. Cotton exhaust dyeing with this type of dye requires a total of about 10 baths, which corresponds to a total of 70-150 L of water per kg of material. Among these about 10 baths, the dye bath is

(A) Hydrolyze the dye that was not fixed to the material. This remaining amount is the cause of unacceptable coloration of the drainage.

(B) Various types of organic substances that act as ingredients in dye additives. Their presence is responsible for the high DCO / DBO of drainage.

(C) Cotton fibrils. Their presence is responsible for the increased suspended solids.

(D) 30-100 g / L electrolyte, in particular sodium chloride and sodium carbonate. These two types of salts are responsible for the very high salinity of the wastewater. Standards regarding the salinity of wastewater are becoming stricter today. Therefore, the total salinity combined with about 10 baths required for cotton processing is still too high to allow release into rivers without negatively affecting the life of freshwater organisms and plankton. . The same situation applies in factories where the presence of electrolytes prevents the activity of bacteria present in biochemically treated sludge.

  Nowadays, in many cases, all baths, including dye baths, are mixed together, resulting in an increase in overall volume and diluting all concentrations of various contaminants. They are then processed in a normal factory, combining physicochemical treatment, followed by decoloring treatment for finishing, if necessary, with biochemical treatment. Unfortunately, at the end of such treatment, the salinity of the effluent is still well above 1 g / L of electrolyte. This limit on sodium chloride or sodium sulfate and whether a dyeing plant may discharge its wastewater into a river is becoming the highest limit allowed for water discharge in most countries.

  After all, the challenge is how to efficiently and economically separate such dangerous low molecular weight compounds.

  The present invention contains on the one hand most of the water in the dyebath which contains no dye and no chemical products but contains most of the salt introduced at the start of dyeing and on the other hand other compounds, in particular hydrolysable reactive dyes. In order to recover the minimum amount of aqueous solution it contains, it is to separate the dyebath and then to filter, neutralize and process it by separate nanofiltration (NF) / reverse osmosis (RO). . The water thus obtained is reused with a new dyeing. The aim of this method is not to allow the drainage of this dye drainage, but to regain its value and process it in order to reuse it. This leads to water and electrolyte savings, and simplification of other bath treatments, especially with respect to their total salinity. The portion of this bath that is separated between the connected NF / RO and that has a very small volume but a high concentration of components will be transported to the landfill in the light of its very small volume, Or it will be sent to incineration.

  Among the various methods of separating inorganic and organic solutes, membrane filtration is efficient in terms of separation, consumes little energy, can be used continuously and can be easily automated, and is extremely small It has a dead volume and a very high specific surface area, and finally has the advantage of performing the desired separation in a single stage by adding a third substance.

  Membrane filtration is therefore advantageous because it can replace the more common biological or physicochemical operations originally used for drainage treatment.

  According to Aptel et al. ("Procedes membranaires" (Proceedings of "Environnement et electricite"), 1993, Paris), when categorizing membrane processes according to the size of the compound to be separated, Most commonly used are reverse osmosis (RO = solute size 0.1-1.2 nm), nanofiltration (NF = solute size 0.5-1.5 nm), ultrafiltration (UF = solute size) 1.2-500 nm) and microfiltration (MF = solute size 500-10,000 nm).

  Since neither UF nor RO can separate inorganic salts from small organic molecules, in these membrane filtration processes operating under pressure, nanofiltration is potentially an organic molecule from inorganic salts, ie the inorganics present. It appears to be the best candidate for separating hydrolyzable reactive dyes from salts.

  These membrane filtration processes performed under pressure operate the feed stream in a tangential filtration arrangement perpendicular to the flow through the membrane. When applied in this manner, it is possible to avoid deposition of materials that increase resistance to movement by washing the film surface.

  In these processes, only a portion of the feed solution (permeate) passes through the membrane as described in the present invention and the appended claims. The feed stream that did not pass through the membrane is known as “concentrated water”. This concentrated water can be collected directly, but in that case it is necessary to use a large membrane surface area (or repeat this operation with several continuous filtration devices) to obtain satisfactory efficiency. This concentrated water can also be recycled to the main tank, which is the most common and most economical procedure and will be described in the present invention.

  In the case of separation of two kinds of solutes O and I (O is an organic compound, I is an inorganic salt or an inorganic salt), the efficiency of the separation process is expressed by the following parameters.

Degree of capture = (([O] _supply− [O] _transmission ) / [O] _supply ) × 100
This same relationship is also used for solute I.
Permeation flux = flow rate of material through the membrane / membrane surface area. This flux, given for a given transmembrane pressure (tmp), is generally corrected to 20 ° C. by taking into account variations in solution viscosity as a function of temperature.

  The filtration membrane is a cross-linked polyamide type chemically aromatic polymer that is deposited as a thin layer (“skin”) that provides selectivity on a porous polymer layer (support) that provides mechanical strength. A composite membrane structure is provided. Such a membrane structure generally indicates a TFC (thin film composite). Nanofiltration and reverse osmosis membranes are available from well known suppliers of reverse osmosis membranes and other membranes operating in pressure processes. Examples include Osmonics, Millipore, Pall, or Filmtec.

  Nanofiltration and reverse osmosis membranes are generally organized in modular form. “Spiral” type modules are often used because of the advantages of this type of module being small, low pressure drop, low dead volume, and reasonable price. It is this type of module that will be used to describe the present invention. However, other types of modules having different profiles such as flat membranes can also be used.

  The main fields of application of nanofiltration are the production of soft or ultrapure water and the selective removal of multivalent ions for monovalent ions. For example, the removal of silica and sulfate in brine is extremely important industrially. This is because the dissolved or suspended silica in the brine supplied to the chlorine production process by electrolysis (especially the membrane electrolytic cell method) causes problems to form a film on or inside the ion exchange membrane separator. is there. In the sodium chlorate manufacturing process, silica also causes insoluble deposits at the anode when it is present in the feed brine, which causes an increase in bath voltage and premature wear of the anode coating.

  Furthermore, sulfate is a common component of commercially available brine and enters and accumulates in the electrolyzer when no special operation is required to remove it. Over time, the sulfate concentration increases and interferes with electrolysis by causing operational problems due to local precipitation in the cell. Therefore, it is desirable to reduce the concentration of sulfate or silica in the concentrated brine as much as possible. This is the reason why the conventional method of precipitating harmful salts is replaced by the nanofiltration method.

  International Publication No. WO 96/33005 thus discloses a nanofiltration method for removing sulfate, silica, and dichromate from brine.

  Similarly, US Pat. No. 5,858,240 discloses a nanofiltration method for reducing the concentration of sulfate, silica, or dichromate in the chlorine production process or chlorate process feed brine. Yes.

  In addition, nanofiltration methods have been used downstream of industrial processes to extract certain inorganic salts present in aqueous solutions. Thus, Ericgaubert's paper (hypothesis) describes the separation of radioactive and non-radioactive elements by nanofiltration assisted by complexation in high saline media.

  K. H. Ahn et al. Describes the removal of ions in an aqueous rinse derived from nickel electrodeposition using low pressure nanofiltration (141446746 Pascal No. 99-0343865).

  Similarly, K.K. Linde et al. Describe nanofiltration of salt solutions (leaching solutions) generated from landfills, which dampen heavy metals that are polyvalent cations such as Cd, Zn, Pb, or Cr and are low toxic substances. It makes it possible to discharge monovalent cations such as Na or K (Desalination, No. 103 (1995) 223).

Some examples of separation between organic compounds and inorganic salts in dilute solutions are also known.
Foster et al. Remove chlorinated organic derivatives and pesticides from drinking water by nanofiltration (J. Inst. Water Environ. 5 (1991) 466-477).

  garema et al. describe the standardization of milk quality by nanofiltration of amino acids through organic membranes (Milk (leLait), 76 (1996), 267-281).

  Trebouet et al. Found that leachate from landfills by nanofiltration and ultrafiltration to achieve the passage of medium-sized organic molecules at the expense of large organic molecules (not necessarily biodegradable molecules). The process is described (Sci. Rev. Water (Rev. Sc. Eau), No. 3 (1993), 365-381).

  Compared to conventional treatment methods of dyeing factory effluents combined with physicochemical treatment and / or decolorization treatment and / or biological treatment, on the one hand it allows the recycling of concentrated sodium chloride and water, on the other hand There is indeed a need for a method that is located at the very core of the dyeing process that makes it possible to concentrate hydrolysable reactive dyes.

  Find a method that can actually recirculate a concentrated solution of sodium chloride in pure water and allow a minimum amount of water containing hydrolysable reactive dyes and dye additives to flow. It should be necessary.

  Thus, it has been found that processes including prefiltration, neutralization, nanofiltration, and then reverse osmosis meet these requirements.

  The object of the present invention is therefore a process for treating a bath for exhaustive dyeing of cellulose fibers with reactive dyes, including prefiltration, neutralization, nanofiltration and then reverse osmosis.

  The method of the present invention includes that the dyebaths are industrial baths and that they preferably contain hydrolyzable reactive dyes belonging to the trichloropyrimidine, difluoropyrimidine, difluoromonochloropyrimidine, monochlorotriazine, and vinylsulfone families. Features.

  Pre-filtration is performed using a filter with a membrane having a preferred cutoff threshold between 80 and 120 microns.

Neutralization is carried out with an acid, preferably hydrochloric acid, in the presence or absence of air bubbles.
The separation during nanofiltration takes place on the one hand in aqueous solutions of inorganic salts present in high concentrations and on the other hand in aqueous solutions of hydrolyzable reactive dyes having a size close to the membrane cutoff threshold.

  The feed liquid was continuously introduced under a positive pressure into a filtration module equipped with a nanofiltration membrane to obtain a liquid that passed through the membrane (permeate) and a liquid that moved without passing through the membrane (concentrated water). The concentrated water is continuously sent to the supply tank.

  During nanofiltration, hydrolyzable reactive dyes are concentrated upstream of the membrane and inorganic salts are removed on this membrane by a concentration step.

  Also during nanofiltration, the concentration of hydrolyzable reactive dye upstream of the membrane is kept constant by the addition of pure water, and inorganic salts are removed in this membrane by a diafiltration step.

The nanofiltration stage is
(I) single step (concentration),
(Ii) 2 steps (diafiltration-concentration), or (iii) 3 steps (concentration-diafiltration-concentration),
Preferably it can be operated in 3 steps.
In the process of the present invention, the initial concentration of inorganic salt is between 30 and 100 g / L.
In the reverse osmosis step, the initial concentration of inorganic salt in the feed solution is between 5 and 70 g / L, preferably between 10 and 15 g / L.

  The concentrated water obtained from the reverse osmosis consists of pure water that is concentrated to between 3 and 8% by weight, does not contain colored waste, and preferably contains inorganic salts with a pH between 5.5 and 6, It can also be reused for staining.

The object of the present invention is to ensure that one compound is present in an aqueous solution in order to recycle as much as possible to one compound as much as possible and to recycle the maximum possible amount of water. It is to provide an innovative method that makes it possible to separate several kinds of compounds. More specifically, the object of the present invention is to separate and concentrate water-soluble inorganic salts, dyes, and organic additives. The dyes in question are reactive dyes that become covalently attached to cellulose or hydrolyzed and remain in the bath. There are a very large number of reactive dyes characterized by the nature of the reactive groups, and they are better classified by names such as dichlorotriazine, monochlorodifluoropyrimidine, dichloroquinoxaline, monochlorotriazine, vinylsulfone and the like. The inorganic salts in question are compounds having sodium cations and Cl ⁻ , SO ₄ ²⁻ or CO ₃ ²⁻ anions. Organic additives in question are partially neutralized compounds based on polyacrylic acid, dispersions of polyethylene wax, or sulfonated polymers.

  The aqueous solution containing only the concentrated inorganic salt not containing the hydrolyzable reactive dye thus obtained can be reused for new dyeing. This leads to water and sea salt savings, simplification of the normal treatment of other baths, and a thorough reduction of drainage salinity. Other separation parts that are small in volume and contain high concentrations of hydrolyzable reactive dyes and chemical products should be readily handled by conventional methods (incineration or in landfills).

In a broad sense, the present invention relates to a prefiltration-neutralization-nanofiltration-reverse osmosis process.
(Preliminary filtration (stage 1))
The aim of this very important step is to remove cotton fibrils and other large compounds that can block the membrane downstream of the process. The formation of these fibrils is essential to the exhaustive dyeing technology using the latest dyeing machines. This depends on the type of material (jersey, interlock, loop, etc.) and yarn quality, ie the average length of the fiber and the degree of twist. A possible cut-off threshold range is 10-200 microns, preferably 80-120 microns. Various preliminary filtration tests have shown that an average cut-off threshold of 100 microns is sufficient to complete this removal.

(Neutralization (stage 2))
The aim of this stage is to convert them in acid, preferably hydrochloric acid, in order to convert alkali salts that are essentially present in carbonate form and also in the form of sodium hydroxide to sodium chloride and carbon dioxide gas. It is to be summed. This is because the presence of alkali salts in the bath water during the first dyeing step is unacceptable. The inventors have shown that it is best to bubble air during neutralization with hydrochloric acid to remove the carbon dioxide gas formed as quickly and completely as possible. If the pH of the water is not sufficient acidic, and if the CO ₂ is present, the sodium bicarbonate is again formed. Don't forget, the presence of this salt in the recirculating water that will be directed to a new dyeing will have an undesirable lasting effect, preventing the bath pH from reaching the value required for optimal dye fixing. Therefore, next time staining is hindered. This leads to a decrease in yield. This water must be characterized by a pH of 5.5-6.0 and a TA of less than 15 degrees Fahrenheit.

  In order to bring together a concentrated solution of the maximum amount of NaCl type inorganic salt that must be recycled, this acidic neutralization (i) removes alkali salts that may impair the yield of the next dyeing, (ii) ) Improving the permeation flux during nanofiltration stage 3, and (iii) adding a solution having a pH (preferably 5.5-6.0) very close to the pH of the solution used for dyeing to the head of the process. It is possible to return to the department.

(Nanofiltration (stage 3))
To filter in two stages, the feed solution is introduced into a filtration module equipped with a membrane under positive pressure and passed through the membrane (permeate), and the solution passed through without passing through the membrane (concentrated water). The concentrated water is then recycled to the tank containing the feed solution.

  The aim of this nanofiltration is to first keep the concentration of the dye in the concentrated water constant, then increase it as much as possible and lower the concentration of the inorganic salt in it as much as possible, and secondly, the concentration of the inorganic salt in the permeate. The maximum possible concentration, the minimum possible concentration of inorganic compounds (hydrolyzable dyes, dye additives) and the maximum amount of water.

  The initial concentration of inorganic salt in the feed is between 30 and 100 g / L. Indeed, the prior art does not provide an example of the separation of a high concentration of hydrolyzable reactive dye / inorganic salt present at high concentration in an actual industrial solution. The reason for this is that when the concentration of inorganic salt increases and reaches a value of 10-20% by weight per volume, the flux is on average one tenth, while the salt capture rate is very low. (M. Nystrom et al., J. Membrane Science, 98 (1995), 249-262).

  We have found that when the dye belongs to the family of, for example, trichloropyrimidine, difluoropyrimidine, difluoromonochloropyrimidine, monochlorotriazine, and vinyl sulfone, and when the inorganic salt is present at a high concentration of 10% by weight, It has been found that it is possible to separate the dye efficiently (or from several inorganic salts).

  In fact, it is surprising that when the size of the organic compound is not very different from the size of the membrane cutoff threshold (300 and 500 Daltons respectively), there is no blockage of the membrane pores by this compound.

  Furthermore, there was concern that the membrane may be modified due to ionization and hydration of the polymer forming the membrane, more specifically, the modification may occur due to adsorption of the hydrolyzable reactive dye onto the membrane. So, these obtained results are unexpected.

  In summary, there was nothing to predict that chemical and / or physical clogging of the membrane could be avoided in terms of product concentration and molecular weight present in the effluent to be treated. These high performances are surprising.

  Thus, such unexpected selectivity of the membrane with high salt concentrations provides an advantageous field of application in the concentration of dyes present in aqueous solutions and the separation of inorganic salts such as NaCl.

  The dye is at a concentration of 0.01-4 g / L (preferably having an average of 2 g / L) and the inorganic salt is at a concentration of 1-100 g / L (preferably having an average of 70 g / L). is there.

  This third stage of the process according to the invention operates at a pressure of 1 to 40 bar, preferably 10 bar, and a circulating flow rate of 100 to 600 L / hour, preferably 250 to 350 L / hour. This can be done at any desired temperature selected between 0 ° C. and the boiling point of the feed. However, this is limited to the recommended temperature range for the membrane (5-70 ° C), preferably 45-55 ° C.

  At the pH specified in neutralization stage 2, the amount of carbonate or bicarbonate is negligible. However, the inventors have shown that in the membranes and pH ranges studied, the transport of inorganic salts downstream of the membrane is much less when the charge of these salts increases (divalent ions). More specifically, if carbonates remain in solution despite neutralization, these carbonates should become concentrated upstream of the membrane and should not be recycled for the next staining.

  This nanofiltration step can be carried out in two or three steps depending on the concentration and nature of the hydrolysable reactive dye, but also depending on the salt concentration. When taking only the concentration of hydrolyzable reactive dye as a reference, the following classification can be proposed.

(A) For very low concentrations of hydrolysable reactive dyes,
(B) For low concentration hydrolyzable reactive dyes, preconcentration-diafiltration-concentration stage;

(C) Diafiltration-concentration for high concentrations of hydrolyzable reactive dyes.
The dye preconcentration stage consists in recovering the maximum amount of salt downstream of the membrane. In practice, the higher the upstream salt concentration, the greater the amount of salt that passes through the membrane. If the concentration of hydrolyzable reactive dye becomes too high upstream of the membrane, i.e. the permeate flux becomes too low, the diafiltration stage is started.

  This diafiltration stage consists in recovering the salt downstream while working with a constant concentration of hydrolysable reactive dye upstream of the membrane. For this purpose, pure water is added to the main reactor at a flow rate equal to the value of the permeate flow rate. The term “purified water” is taken to mean water that has an inorganic salt concentration such that the conductivity does not exceed 1 mS / cm and does not contain any hydrolyzable reactive dyes. The dye concentration stage begins when 80-90% of the salt is recovered downstream of the membrane.

The concentration step consists in concentrating the hydrolyzable reactive dye as much as possible. This concentration step can be performed when the permeate flux is too low or when the clogging is too high, more specifically for solutions described in the present invention, less than about 1 L / hr · m ² · bar ( When it reaches about 20% of the initial transmittance of the membrane, it is heated.

(Reverse osmosis (stage 4))
This step may not be performed if the initial hydrolyzable reactive dye concentration in step 3 is very low. This is the case when it has a light coloration whatever the type of reactive dye used, or when it has a color that occurs with a highly fixed reactive dye, even if it is light, intermediate, even darker. This is because the dye preconcentration step is sufficient. On the other hand, from the standpoint that diafiltration is necessary, it is necessary to recover pure water introduced during diafiltration by reverse osmosis in the osmotic solution, and in the concentrated water, It is necessary to recover brine containing as much salt as possible.

  The aim of reverse osmosis is therefore on the one hand to increase the concentration of inorganic salts as much as possible without decomposing the inorganic salts and on the other hand to obtain as pure water as possible. The initial concentration of inorganic salt in the feed solution depends on this diafiltration stage and is between 5 and 70 g / L, preferably an average of 10 to 15 g / L.

  The inventors have discovered that even when the concentration of inorganic salt (or some inorganic salts) exceeds 1% by weight, it can be efficiently concentrated.

  As a result, the selectivity of such membranes for high concentrations of salt provides an advantageous field of application in the concentration of inorganic salts present in aqueous solutions containing inorganic salts such as NaCl.

  The fourth stage of the process according to the invention operates at a pressure of 1 to 80 bar, preferably 70 bar, and a circulating flow rate of 300 to 800 L / hour, preferably 600 L / hour. This can be done at any desired temperature selected between 0 ° C. and the boiling point of the feed. However, it is limited by the recommended temperature range (5-7 ° C.) for the membrane. The pH used in the process according to the invention is between 5.5 and 6, in fact a function of the second stage conditions. The concentration of the inorganic salt recovered in the reverse osmosis concentrated water is between 30 and 80 g / L, with an average of 60 g / L.

(Next dyeing test)
These next dyeing tests are not mentioned in this process, but they prove that this process is effective. These are described in Appendix Table 1. These comparative next dyeing tests were conducted using laboratory water, reference dyeing, and salt water recycled according to the process described in this patent. Four dyes were tested and there was no difference in dye behavior between the two aqueous systems used.

(Explanation of process)
a. Assumptions In order to better understand the present invention, the optimum machining conditions will be described using the embodiment with reference to FIGS. FIG. 1 is a diagram of the complete process described in the present invention. Steps 1 and 2 are drainage pretreatment stages, which allow stages 3 and 4 to be performed under the best possible conditions. From the outlets of these two pretreatment stages, the solution is carried to stages 3 and 4 which constitute the core of the present invention.

All of these tests were performed in an industrially dyed bath, not a modified bath. Membrane filtration between all membrane surface area 0.4～5M ² study of (nanofiltration and reverse osmosis), preferably performed in 2.5 m ^2.

b. Principle Dye factory effluent is first transported to pre-filtration in stage one. The purpose is to keep the cotton fibrils present to avoid clogging of the membrane in stages 3 and 4. Stage 2 is the stage of neutralizing the sodium carbonate present in the solution. This neutralization is performed using concentrated hydrochloric acid until the pH is between 5.5 and 6. The pre-filtered and neutralized effluent is carried to stage 3. The main aim of this stage is to separate the sodium chloride salt and concentrate the dye. This stage 3 is divided into two. Ie

  1. Diafiltration stage. Here, the inorganic salt is separated while keeping the concentration of the dye constant by adding purified water.

2. Concentration stage. Here, the dye is concentrated as much as possible.
The term “purified water” is understood to mean water that has an inorganic salt concentration such that the conductivity does not exceed 1 mS / cm and does not contain any hydrolyzable reactive dyes. The concentrated dyeing solution is subsequently transported to the landfill or because of its very small volume or incinerated.

  The sodium chloride solution is carried to stage 4 where it is concentrated. This concentrated sodium chloride solution is to be recycled to the head of the dye shop process. The pure water solution obtained downstream of the reverse osmosis membrane can be recycled to stage 3 to provide the purified water needed for the diafiltration step, or recycled to the head of the dyeing process for soft water. provide.

c. Step 1 (Preliminary Filtration) Stage 1 consists solely of a stainless steel pre-filter whose characteristics are stainless steel cut off at 100 μm. The prefilter scheme is shown in FIG.

  Tests with about 15,000 L of an industrial solution of hydrolyzable reactive dyes did not show any clogging of these prefilters or complete capture of fibrils. This capture is demonstrated by the presence of a 70 micron security pre-filter placed downstream and free of any cotton fibrils.

d. Illustration of Stage 2 (Neutralization) The arrangement of FIG. 3 for Stage 2 consists of a holding tank having a capacity of 100 L, an agitation paddle, a pH meter probe, a metering pump, a hydrochloric acid tank, and a vent at the bottom of the vessel for directing air Including equipment. The pH of the staining solution is measured continuously, allowing the metering pump to adjust the pH to a value between 5.5 and 6.0. The amount of concentrated hydrochloric acid (9.05N, ie 33%) is between 5 and 35 mL / L (preferably 20 mL / L) depending on the type of drainage and the concentration of carbonate.

  It can be seen that it is advantageous to replace the carbonate with a mixture of carbonate and sodium hydroxide. This makes it possible to greatly reduce the amount of hydrochloric acid required. The inventors have confirmed that this mixture does not impair the dyeing conditions. In fact, the final yield of the dye, the dyeing speed, and the uniform intensity of the dye are not affected by this modification. Water acidification (pH 5.5), as will be discovered later, provides the second advantage that the permeate flux during nanofiltration is greatly improved.

* Dyeing behavior of reactive dyes in the dye bath containing carbonate 20 g / L is the same as the dyeing behavior obtained in a bath containing sodium carbonate 10 g / L plus ³⁶ 0 Be sodium hydroxide 2 mL / L. In contrast, less hydrochloric acid will be used to neutralize each corresponding bath.

e. Diagram of Stage 3 The arrangement of FIG. 4 includes a 25 L polymethacrylic acid ester tank A containing Stage 2 source feed. This tank is connected to the filtration cartridge D via a stainless steel feed circuit 2, and the temperature is regulated by a thermostatically controlled bath that allows the temperature to be kept constant between 20 ° C and 60 ° C. . The supply circuit 2 includes a high-pressure pump B provided with a speed change drive device, and a discharge circuit 5 provided with a valve C positioned in front of the pump B.

This filtration cartridge D, which consists of a cylinder made of epoxy glass polymerized under high temperature conditions, contains a spiral membrane. This membrane is of the organic type with an exchange surface area of 2.5 m ² made of polyamide / polysulfone. This nanofiltration membrane is sold under the trade name Desal 5 by Osmonics. The permeate passing through this membrane goes to the container H.

  The concentrated water is collected via the circuit 3, passes through the control valve E, and is recirculated to the tank A. To keep the starting solution volume constant and limit membrane clogging, an amount of purified water equal to the volume of permeate removed is optionally added to tank A (diafiltration stage). This water is drawn from the tank G maintained at the same temperature T as the fluid circulating in the circuit 2 and transferred to the tank A via the circuit 4 using the pump F. The choice of this optional addition of water is explained by the presence or absence of a high concentration of hydrolyzable reactive dye (see previous description of the invention).

The circuit also includes a pressure sensor _{P 1} and _{P 2,} whereby the pressure drop at the end of the membrane module _(P 1 -P ₂₎ and transmembrane pressure difference _{(tmp = (P 1 + P} 2) / 2) can be measured become. Furthermore, the conductivity measuring electrode arranged in the tank A makes it possible to continuously monitor the conductivity of the concentrated water over a period of time.

  When the conductivity in tank A reaches a value corresponding to the minimum concentration of the desired sodium salt, diafiltration (addition of water from tank G) is stopped and the filtration operation is continued. The conductivity reflects a decrease in the weight of concentrated water in tank A. When the concentrated water in tank A weighs only 1/10 to 1/40 of the original volume, the filtration operation is stopped and the solution is analyzed. This final concentrated water weight range makes it possible to operate with a permeate flux that is not too low, i.e., without significantly clogging the membrane. This concentrated dye solution is easily processed by conventional methods (incineration or landfill) because it is so small. The NaCl solution recovered in tank H is carried to stage 4 of the process.

f. Illustration of Stage 4 (Reverse Osmosis Process) The arrangement of FIG. 5 includes a 20 L polymethacrylic acid ester tank A ″ containing the permeate from Stage 3. This tank comprises a stainless steel feed circuit 2. The temperature is regulated by a thermostatically controlled bath that allows the temperature to be kept constant between 20 ° C. and 60 ° C. The supply circuit 2 includes a high-pressure pump P ″ and a discharge circuit 5 with a valve C ″ located in front of the pump P ″.

This filtration cartridge D ″ consisting of a stainless steel cylinder contains a spiral membrane. This membrane is of the organic type with an exchange surface area of 2.3 m ² made of polyamide / polysulfone. This reverse osmosis membrane. Is sold by Osmonics under the trade name SC2540C.

The circuit also includes a pressure sensor _{P 1} and _{P 2,} whereby the pressure drop at the end of the membrane module _(P 1 -P ₂₎ and transmembrane pressure difference _{(tmp = (P 1 + P} 2) / 2) can be measured become. Furthermore, the conductivity measuring electrode arranged in the tank A ″ makes it possible to continuously monitor the conductivity of the concentrated water over a period of time.

  The permeate passing through the membrane is recycled to the nanofiltration vessel G and supplied for diafiltration or used as production water in dyeing. Concentrated water is collected via circuit 3 and recirculated to tank A "through control valve E".

  When the conductivity in tank A ″ reaches a value corresponding to the maximum concentration of the desired sodium salt, the concentration is stopped. The concentrated concentrated solution is carried to the head of the process and possibly replenished salt. Add a new stain.

  Stages 1 and 4 can be operated continuously or discontinuously. On the other hand, stages 2 and 3 work discontinuously and very well because of the foaming and concentration steps, respectively.

  The following examples illustrate the invention but do not limit the invention. For all of the following examples, pre-filtration is performed using a stainless steel prefilter. This feature is a stainless steel material that cuts off at 100 μm. Several examples are described in detail in the text, and all these examples are summarized in the table in Appendix 2. Also, the next dyeing test is presented to show the final advantages of the present invention, but does not form part of the present invention.

Example of stage 2 (neutralization) (Example 1: When there is no air bubbling)
A synthesis solution representing a dyebath contains 50 g / L sodium chloride and 5 g / L sodium carbonate. In order to obtain a pH of 5 and a total alkalinity of 2.73, an amount of 9.4 mL / L hydrochloric acid (33%) must be added to the solution, whereby the solution is brought to 0.546 mmol / L HCO. It becomes possible to have ^3- concentration and 2.903 mmol / L free CO ₂ .

(Example 2: Effect of air bubbling)
The same synthesis solution as in Example 1 is used, but this time, after adding the same amount of hydrochloric acid, air is introduced using a venting device. This time the pH of this solution is 7.37 and the total alkalinity is 2.545, so that this solution has an HCO ³ concentration of 1.018 mmol / L and 0.032 mmol / L free CO _2. Is possible.

(Example 3: When there is no foaming of air)
A synthesis solution representative of a dyebath contains 80 g / L sodium chloride and 12 g / L sodium carbonate. In order to obtain a pH of 5 and a total alkalinity of 7.86, hydrochloric acid (33%) in an amount of 22 mL / L must be added to this solution, so that this solution has an HCO ³ concentration of 1.5 mmol / L and It becomes possible to have 2.25 mmol / L of free CO ₂ .

(Example 4: Influence of foaming of air)
The same synthesis solution as in Example 5 is used, but this time, after adding the same amount of hydrochloric acid, air is introduced using a venting device. This time the pH of this solution is 7.25 and the total alkalinity is 6.495, so that this solution has an HCO ³⁻ concentration of 1.3 mmol / L and a free CO ₂ of 0.3 mmol / L. It becomes possible.

Example of stage 3 (nanofiltration) (Example 1)
The bath to be treated results from the industrial dyeing of 250 kg of pure cotton knitwear in a bath ratio of 1: 6.5, ie a volume of 1625 L. The starting formulation is as follows.

  Drimaregolden Yellow K-2R 2.565%, ie 3.93 g / L

Drimarene Red K-8B 2.700%, ie 4.14 g / L
Drimarene Blue K-2RL 0.050%, ie 0.076 g / L

Additive based on ethoxylated fatty alcohol 1g / L
Sodium chloride 80g / L
Sodium carbonate 8g / L
For nature reasons, the dyeing machine cannot be emptied immediately without prior cooling of the material and lowering the pH by supplying fresh water. It is at this stage that the dye bath is withdrawn for the nanofiltration test. Corresponding to the bath, cotton fibrils are removed by pre-filtering an amount of 9000 g of a solution containing 61 g / L of sodium chloride using a 100 μm prefilter. The solution is then neutralized with an amount of 4.9 mL / L hydrochloric acid (33%).

  The resulting solution is placed in a tank and kept at a temperature of 50 ° C. The circulating flow rate of concentrated water is adjusted to 300 L / hour. Take the transmembrane pressure up to 10 bar. Collect the permeate continuously. A constant, same flow of distilled water is added to the tank at 50 ° C. to operate with a constant concentration of hydrolysable dye. That is, this stage is diafiltration.

The conductivity of the downstream and upstream solutions is continuously measured with an electrical conductivity meter. The membrane used is a polypropylene spiral membrane obtained from Osmonics with a filtration area of 2.5 m ² and a cut-off threshold between 200-300 Da.

  At the end of the diafiltration operation with a run time of 18 minutes, a concentration stage with a total run time of 2 minutes is carried out (stopping the addition of distilled water and concentrating the dye remaining in the concentrated water). 39,800 g of permeate having an average composition of NaCl 14 g / L is recovered. Furthermore, 1400 g of concentrated water with a composition of NaCl 5.7 g / L remains in the feed tank.

The instantaneous capture of NaCl varies from 0% to 27% within a concentration range of 61-5.7 g / L. Since the degree of capture of the hydrolyzable reactive dye is 99%, the recovered permeate is colorless and transparent throughout this operation. 91% of the sodium chloride is finally recovered and the mass balance is verified to within the relative accuracy of the measured value of less than 1%. The permeate flux varies from 40 to 51 L / hr / m ² during the diafiltration phase and from 51 to 39 L / hr / m ² during the concentration phase. The membrane module is completely regenerated at the end of the treatment with a simple acid / base wash under high temperature conditions.

(Example 2)
Corresponding to the bath, cotton fibrils are removed by prefiltering an amount of 9477 g of a solution containing 61 g / L of sodium chloride using a 100 μm prefilter. The solution is then neutralized with an amount of 4.9 mL / L hydrochloric acid (33%). The filtration operation is carried out under the same conditions as in Example 1 except that the transmembrane pressure is brought up to 20 bar. At the end of the diafiltration operation with a run time of 9 minutes and the dye concentration operation with a total run time of 1 minute, 35,509 g of permeate with an average composition of NaCl 18 g / L are recovered. In addition, 4452 g of concentrated water with a composition of NaCl 5.55 g / L remain in the feed tank. The instantaneous capture of NaCl varies from 6% to 19% within a concentration range of 61 to 5.55 g / L. Since the degree of capture of the hydrolyzable reactive dye is 99%, the recovered permeate is colorless and transparent throughout this operation. 92% of the sodium chloride is finally recovered and the mass balance is verified to within the relative accuracy of the measured value of less than 1%. Flux of permeate varied from 49 during diafiltration stage to 55L / hr / ^{m 2,} also varies from 55 during the concentration period to 53L / hr / ^{m 2.} The membrane module is completely regenerated at the end of the treatment with a simple acid / base wash under high temperature conditions.

(Example 3)
Corresponding to the bath, cotton fibrils are removed by prefiltering an amount of 9220 g of a solution containing 61 g / L of sodium chloride using a 100 μm prefilter. The solution is then neutralized with an amount of 4.9 mL / L hydrochloric acid (33%). The filtration operation is carried out under the same conditions as in Example 1 except that the transmembrane pressure is brought up to 5 bar. At the end of the diafiltration operation with a run time of 35 minutes and the dye concentration operation with a total run time of 1 minute, 50,696 g of permeate with an average composition of NaCl 11.5 g / L are recovered. In addition, 883 g of concentrated water having a composition of NaCl of 6.14 g / L remain in the feed tank. The instantaneous capture of NaCl varies from 0% to 40% within a concentration range of 61 to 6.14 g / L. Since the degree of capture of the hydrolyzable reactive dye is 99%, the recovered permeate is colorless and transparent throughout this operation. 92% of the sodium chloride is finally recovered and the mass balance is verified to within the relative accuracy of the measured value of less than 10%. Flux of permeate varied from 18 during diafiltration stage to 28L / hr / ^{m 2,} also varies from 28 during the concentration period to 27L / hr / ^{m 2.} The membrane module is completely regenerated at the end of the treatment with a simple acid / base wash under high temperature conditions.

(Example 4)
Corresponding to the bath, cotton fibrils are removed by prefiltering an amount of 9399 g of a solution containing 60 g / L of sodium chloride using a 100 μm prefilter. The solution is then neutralized with an amount of 4.9 mL / L hydrochloric acid (33%). The filtration operation is performed under the same conditions as in Example 1 except that the circulating flow rate of concentrated water is adjusted to 100 L / hour. At the end of the diafiltration operation with a run time of 26 minutes and the dye concentration operation with a total run time of 2 minutes, 54,418 g of permeate with an average composition of NaCl 10.8 g / L are recovered. In addition, 1997 g of concentrated water with a composition of 5.7 g NaCl / L remains in the feed tank. The instantaneous capture of NaCl varies from 5% to 25% within a concentration range of 61-5.7 g / L. Since the degree of capture of the hydrolyzable reactive dye is 99%, the recovered permeate is colorless and transparent throughout this operation. 92% of the sodium chloride is finally recovered and the mass balance is verified to within the relative accuracy of the measured value of less than 5%. Flux of permeate varied from 40 during diafiltration stage to 53L / hr / ^{m 2,} also varies from 53 during the concentration period to 50L / hr / ^{m 2.} The membrane module is completely regenerated at the end of the treatment with a simple acid / base wash under high temperature conditions.

(Example 5)
Corresponding to the bath, cotton fibrils are removed by pre-filtering an amount of 9467 g of a solution containing 61 g / L of sodium chloride using a 100 μm pre-filter. The solution is then neutralized with an amount of 4.9 mL / L hydrochloric acid (33%). The filtration operation is carried out under the same conditions as in Example 1, except that tap water is used instead of distilled water during diafiltration (0.395 mS / cm). At the end of the diafiltration operation with a run time of 22 minutes and the dye concentration operation with a total run time of 2 minutes, 54,663 g of permeate having an average NaCl composition of 11 g / L are recovered. In addition, 3237 g of concentrated water with a composition of NaCl 4.8 g / L remain in the feed tank. The instantaneous capture of NaCl varies from 12% to 23% within a concentration range of 61-4.8 g / L. Since the degree of capture of the hydrolyzable reactive dye is 99%, the recovered permeate is colorless and transparent throughout this operation. 93% of the sodium chloride is finally recovered and the mass balance is verified to within the relative accuracy of the measured value of less than 8%. Flux of permeate varied from 23 during diafiltration stage to 28L / hr / ^{m 2,} also varies from 28 during the concentration period to 26L / hr / ^{m 2.} The membrane module is completely regenerated at the end of the treatment with a simple acid / base wash under high temperature conditions.

Example of Step 4 (Reverse Osmosis) (Example 1)
The bath to be treated results from industrial dyeing of 200 kg of pure cotton knitwear at a bath ratio of 1: 8, ie 1600 L. The starting formulation is as follows.

Drimarene Blue HF-RL 0.8%, ie 1g / L
Drimarene Red HF-G 0.312%, ie 0.39 g / L
Drimarene Yellow HF-R 0.520%, ie 0.65 g / L

Sulfonated polymer 1g / L
Sodium chloride 80g / L
Sodium carbonate 12g / L
The amount of 14,360 g of 25.8 g / L concentrate of permeate resulting from nanofiltration of this dyebath is introduced into the tank as concentrated water and kept at a temperature of 40 ° C. The circulating flow rate of this concentrated water is adjusted to 400 L / hour. Bring the transmembrane pressure up to 50 bar. The conductivity of the downstream and upstream solutions is continuously measured with an electrical conductivity meter. The membrane used is a spiral membrane obtained from Osmonics with a filtration area of 2.5 m ² . The salt concentration step takes place with a duration of 15 minutes. 8178.2 g of permeate having an average composition of NaCl of 2.26 g / L is recovered. In addition, 5247 g of a composition of NaCl 57.36 g / L remain in the feed tank. The instantaneous capture of NaCl varies from 97.57% to 86.44% within a concentration range of 31.75 to 57.36 g / L. 81.23% of the sodium chloride is recovered and the mass balance is verified to within the relative accuracy of the measured value of less than 14%. The permeate flux varies from 26 to 4.5 L / hr / m ² . The membrane module is completely regenerated at the end of the treatment with a simple acid / base wash under high temperature conditions.

(Example 2)
An amount of 14,439 g of a 24.8 g / L concentrate of permeate resulting from nanofiltration of the same dyebath as described in Example 1 is introduced into the tank as concentrated water and kept at a temperature of 40 ° C. The circulating flow rate of this concentrated water is adjusted to 400 L / hour. Bring the transmembrane pressure up to 50 bar. The conductivity of the downstream and upstream solutions is continuously measured with an electrical conductivity meter. The membrane used is a spiral membrane obtained from Osmonics with a filtration area of 2.5 m ² but more tightly packed than the previous one. The salt concentration step takes place with a duration of 20 minutes. 7955 g of permeate with an average composition of 1.37 g / L NaCl are recovered. In addition, 5024 g of a composition of NaCl 57.45 g / L remains in the feed tank. The instantaneous capture of NaCl varies from 98.08% to 85.87% within a concentration range of 26.88 to 57.45 g / L. 80.6% of the sodium chloride is recovered and the mass balance is verified to within the relative accuracy of the measured value of less than 19%. The permeate flux varies from 20.52 to 1.85 L / hr / m ² . The membrane module is completely regenerated at the end of the treatment with a simple acid / base wash under high temperature conditions.

(Example 3)
An amount of 14,161 g of the 26.3 g / L concentrate permeate resulting from nanofiltration of the dyebath described in Example 1 is introduced into the tank as concentrated water and kept at a temperature of 40 ° C. The circulating flow rate of this concentrated water is now adjusted to 600 L / hour. Bring the transmembrane pressure up to 50 bar. The conductivity of the downstream and upstream solutions is continuously measured with an electrical conductivity meter. The membrane used is the same as in Example 2. The salt concentration step takes place with a duration of 16 minutes. 7975 g of permeate having an average composition of NaCl of 1.046 g / L is recovered. In addition, 5287.4 g of a composition of NaCl 57.98 g / L remain in the feed tank. The instantaneous capture of NaCl varies from 98.1% to 90.45% within a concentration range of 29.07 to 57.97 g / L. 82.30% of the sodium chloride is recovered and the mass balance is verified to within the relative accuracy of the measured value of less than 15%. The permeate flux varies from 23.16 to 2.6 L / hr / m ² . The membrane module is completely regenerated at the end of the treatment with a simple acid / base wash under high temperature conditions. A summary of all these tests performed is shown in Appendix 2.

Appendix Table 1
I. Dyeing with reactive dye recycle salt water 1) Purpose of the test To make sure that salt water obtained by prefiltration (neutralization) and nanofiltration / reverse osmosis of reactive dye dye baths can be reused for new dyeing .

2) Formulation of dye bath 0.590% of Dreamare Yellow HF-R
1.400% of Dreamaren Red HF-G
Navy HF-B 0.900%
Sea salt 50g / L
Sodium carbonate 15g / L
Dye additive After a series of treatments carried out using a dye bath of reactive dyes, ie pre-filtration, neutralization, nanofiltration, and reverse osmosis, brine with the following characteristics is recovered.

Sodium chloride 61g / L ± 0.2g / L
pH = 5.15
TA = 6.5
In the next test, this recycled brine will be considered as containing 60 g / L of sodium chloride.

  According to the IR spectrum of the brine, this indicates that it no longer contains the dye additive.

実験用水の場合
ＮａＣｌ

ａ）Ｄｒｉｍａｒｅｎｅ Ｒｅｄ ＣＬ−５Ｂを１％用いた配合
実験用水の場合
Ｄｒｉｍａｒｅｎｅ Ｒｅｄ ＣＬ−５Ｂを１％
塩化ナトリウム４８ｇ／Ｌ
炭酸ナトリウム７ｇ／Ｌ
再循環塩水８０％と実験用水２０％の場合
Ｄｒｉｍａｒｅｎｅ Ｒｅｄ ＣＬ−５Ｂを１％
塩を含まず
炭酸ナトリウム７ｇ／Ｌ
全体積中で再循環した塩水部分起源の塩４８ｇ／Ｌ、すなわちＤｒｉｍａｒｅｎｅ Ｒｅｄ ＣＬ−５Ｂ染料１％に必要な量が回収される。 This brine is colorless.
The experimental water used as a reference is
Permanent hardness 0 ^o F
TA = less than 5 pH = 7 ± 0.5
3) Next time dyeing with Dreamarene material = 15g
Process = bath ratio 1: 1.0, total volume = 150 mL
In the case of recirculated brine

In case of laboratory water NaCl

a) Formulation using 1% of Dreamaren Red CL-5B In the case of experimental water 1% of Dreamaren Red CL-5B
Sodium chloride 48g / L
Sodium carbonate 7g / L
In the case of 80% recirculated salt water and 20% experimental water, 1% of Dreamaren Red CL-5B
Sodium carbonate 7g / L without salt
48 g / L of salt originated from the brine fraction recycled in the entire volume, ie the amount required for 1% of Dreamaren Red CL-5B dye, is recovered.

b) Formulation using 3% of Dreamaren Red CL-5B In the case of experimental water 3% of Dreamaren Red CL-5B
Sodium chloride 70g / L
Sodium carbonate 12g / L
In the case of 100% recirculated brine, 3% of Dreamaren Red CL-5B
Sodium chloride 10g / L
Sodium carbonate 12g / L
100% of the recovered brine is used and 10 g / L of sodium chloride is added to this to reach a concentration of 70 g / L of electrolyte required for staining 3% of Dreamaren Red CL-5B.

c) The results showed no difference (saturation, lightness, fastness) between the colors obtained with laboratory water or recycled brine, whatever the water used.

4) Next time dyeing with Drimareene K Material = 15g
Process = bath ratio 1: 1.0, total volume = 150 mL
In the case of recirculated brine

In case of laboratory water NaCl

a) Formulation using 4% of Dreamaren Red K-4BL In case of experimental water 4% of Dreamaren Red K-4BL
Sodium chloride 60g / L
Sodium carbonate 5g / L, or carbonate 3g / L + ^36o BE NaOH 0.5mL / L

In the case of 100% recirculated brine, 4% of Dreamaren Red K-4BL
Without salt 5g / L sodium carbonate or 0.5g / L carbonate 3g / L + 36 ^o BE NaOH

  It is meaningless to add electrolyte because this recirculated brine already contains sodium chloride 60 g / L, the recommended amount for staining 4% of Drimarene Red K-4BL.

b) The results showed no difference (saturation, lightness, fastness) between the colors obtained with laboratory water or recycled brine, whatever the water used.

5) Next time dyeing with Dreamarene HF Material = 15g
Process = bath ratio 1: 1.0, total volume = 150 mL
In the case of recirculated brine

In case of laboratory water NaCl

a) Formulation using 2% of Dreamaren Red HF-2B For experimental water 2% of Dreamaren Red HF-2B
Sodium chloride 70g / L
Sodium carbonate 10g / L, or carbonate 5g / L + 36 ^o BE NaOH 1mL / L

In the case of 100% recirculated brine 2% of Dreamaren Red HF-2B
Sodium chloride 10g / L
Sodium carbonate 10g / L, or carbonate 5g / L + 36 ^o BE NaOH 1mL / L

  An electrolyte of 10 g / L should be added to a dyebath containing recycled brine instead of the recommended amount for sodium chloride 70 g / L, ie 2% Drimarene Red HF-2B.

b) The results showed no difference (saturation, lightness, fastness) between the colors obtained with laboratory water or recycled brine, whatever the water used.

6) Next time dyeing with Dreamarene XN Material = 15g
Process = bath ratio 1: 1.0, total volume = 150 mL
In the case of recirculated brine

In case of laboratory water NaCl

a) Formulation using 3% of Dreamare Yellow X-4RN In the case of experimental water 3% of Dreamare Yellow X-4RN
Sodium chloride 70g / L
Sodium carbonate 15g / L, or carbonate 8g / L + ^36o BE NaOH 1.5mL / L

In the case of 100% recirculated brine, 3% of Dreamare Yellow X-4RN
Sodium chloride 10g / L
Sodium carbonate 15g / L, or carbonate 8g / L + ^36o BE NaOH 1.5mL / L

  It is necessary to add 10 g / L of electrolyte to the dyebath containing recycled brine instead of the recommended amount of sodium chloride 70 g / L, i.e. 3% Drimarene Yellow X-4RN.

b) The results showed no difference (saturation, lightness, fastness) between the colors obtained with laboratory water or recycled brine, whatever the water used.

II. Overall Conclusion These tests show that it is possible to use brine recovered from an industrial dye bath containing reactive dyes that have been subjected to subsequent treatments, namely pre-filtration-neutralization-reverse osmosis. Standard staining performed with water called “lab water” is identical to the results obtained using recirculated brine after readjustment of the amount of electrolyte found to be necessary. Results are shown. Normal fastness, tone, and saturation are the same regardless of the type of water used.

Appendix Table 2

CC: Concentrated pigment CB: Concentrated salt water B: Salt water PW: Purified water *: Means footnote │: Number not in parentheses means volume g / L: Number in parentheses is concentration Meaning that in the case of nanofiltration, the concentrated pigment is an aqueous solution containing hydrolysable reactive dyes, additives, and inorganic salts that have not passed through the membrane. The concentration represented by g / L is the concentration of residual inorganic salt.

  Concentrated brine is an aqueous solution containing a “very” high concentration of inorganic salt obtained downstream of the membrane when performing only a preconcentration step (prior to the diafiltration-concentration step) or the concentration step.

  Brine is an aqueous solution containing a high concentration of inorganic salt obtained downstream of the membrane when performing a diafiltration step followed by a concentration step.

  In the case of reverse osmosis, salt water is an aqueous solution remaining upstream of the membrane, and purified water is an aqueous solution that has passed through the membrane. In both cases, the concentration is that of an inorganic salt.

DR (dye): Degree of dye capture. The degree of dye capture is defined as DC = (1−Cp / Co) × 100.
Cp / Co: The ratio of the concentration of permeate to the concentration of the solution upstream of the membrane, measured by absorbance.

DFP = difluoropyrimidine TCLP = trichloropyrimidine MCT = monochlorotriazine VS = vinyl sulfone Drimagen E2R: product for chemical dyeing which is an aromatic sulfonated derivative Sandopur R3C: product for chemical dyeing which is a copolymer of partially neutralized carboxylic acid

(Not described in the original)

Claims (12)

  A process for treating a bath for exhaustion dyeing of cellulose fibers with reactive dyes, comprising prefiltration, then neutralization, then nanofiltration and then reverse osmosis.   The dyebaths are industrial baths and they preferably contain hydrolysable reactive dyes belonging to the family of trichloropyrimidine, difluoropyrimidine, difluoromonochloropyrimidine, monochlorotriazine and vinylsulfone. Item 2. The method according to Item 1.   3. A method according to claim 1 or 2, characterized in that the prefiltration is carried out with a filter with a membrane having a preferred cut-off threshold between 80 and 120 microns.   4. Process according to claims 1-3, characterized in that the neutralization is carried out with acid, preferably hydrochloric acid, in the presence or absence of air bubbles.   Separation during the nanofiltration is carried out on the one hand in aqueous solutions of inorganic salts present in high concentrations and on the other hand in aqueous solutions of hydrolyzable reactive dyes having a size close to the membrane cutoff threshold. The method according to claim 1.   The feed liquid is continuously introduced under a positive pressure into a filtration module equipped with a nanofiltration membrane to obtain a liquid that has passed through this membrane (permeate) and a liquid that has moved without passing through this membrane (concentrated water). 6. The method according to claim 5, wherein the concentrated water is continuously sent to a supply tank.   6. The method of claim 5, wherein during the nanofiltration, the hydrolyzable reactive dye is concentrated upstream of the membrane and the inorganic salts are removed by a concentration step at the membrane.   6. The concentration of the hydrolyzable reactive dye upstream of the membrane during the nanofiltration is kept constant by adding pure water, and inorganic salts are removed by the membrane through a diafiltration step. The method described in 1. Said nanofiltration step,
(I) single step (concentration),
(Ii) 2 steps (diafiltration-concentration), or (iii) 3 steps (concentration-diafiltration-concentration),
6. Method according to claim 5, characterized in that it can be operated preferably in 3 steps.   6. Process according to claim 5, characterized in that the initial concentration of inorganic salt is between 30 and 100 g / L.   Method according to claims 1-10, characterized in that the initial concentration of inorganic salts of the feed solution is between 5 and 70 g / L, preferably between 10 and 15 g / L in the reverse osmosis step. .   The concentrated water obtained from the reverse osmosis is composed of pure water which is concentrated to between 3 and 8% by weight, does not contain colored waste, and preferably contains an inorganic salt having a pH of between 5.5 and 6. The method according to claim 1, wherein the method can be reused for dyeing.

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