Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D11/00—Solvent extraction
  • B01D11/04—Solvent extraction of solutions which are liquid
  • B01D11/0446—Juxtaposition of mixers-settlers
  • B01D11/0457—Juxtaposition of mixers-settlers comprising rotating mechanisms, e.g. mixers, mixing pumps
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D11/00—Solvent extraction
  • B01D11/04—Solvent extraction of solutions which are liquid
  • B01D11/0492—Applications, solvents used
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/26—Treatment of water, waste water, or sewage by extraction
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/20—Heavy metals or heavy metal compounds
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/30—Organic compounds
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2303/00—Specific treatment goals
  • C02F2303/16—Regeneration of sorbents, filters

Definitions

• the present invention relates to the field of the treatment of polluted waters loaded with organic and metal compounds, based on phase separation extraction techniques.
• It relates to an aqueous effluent treatment process, using a liquid / liquid extraction without organic solvent, for extracting organic and metal compounds through their solubilization in mixed micelles.
• Hazardous pollutants are those with the characteristics of toxicity, bioaccumulation and persistence. These are mainly organic pollutants and heavy metals.
• Organic pollution resulting from natural biological reactions and agricultural, industrial or domestic activities, is characterized by its insidious appearance and complexity. It is generally in dissolved form, can be more or less biodegradable, and has a great diversity, including phenolic derivatives especially from the chemical and pharmaceutical industries, pesticides and related products such as plasticizers, lubricants, hydraulic fluids, etc. or the hydroxyl and amine compounds which are widely used in the manufacture of varnishes, paints, inks, or in the perfume and aroma industry. Toxic phenomena induced are extremely variable from one substance to another and are related to the stability of the product, its ability to accumulate, etc.
• Metallic pollutants often called “heavy metals”, or more frequently now “trace elements”, are in turn present in water in the form of electrolytes. They are well targeted by regulation: they are essentially mercury, cadmium, lead, silver, copper, chromium, nickel and zinc, coming from the rejections of various industrial activities, such as surface, electroplating, hydro metallurgy, mining, chemical, petrochemical, pharmaceutical, etc. They are particularly harmful because they are not biodegradable and accumulate in the tissues as one moves up the food chain. Their toxic effects may include the nervous system, blood or bone marrow, and they are usually carcinogenic.
• the increase of the temperature above the cloud point of the solution therefore allows the concentration in the coacervate of a hydrophobic or amphiphilic substance solubilized by the surfactant.
• the two-phase separation - the concentrated extract and the raffinate - is carried out by decantation.
• Heavy metals can be removed from aqueous effluents by coagulation, sand filtration, activated carbon or ion exchange, electrodialysis, or reverse osmosis techniques.
• the most widely used method for the treatment of heavy metal effiuents is, as for organic pollutants, liquid / liquid separation using a solvent.
• the solvent must be accompanied by a complexing agent of the metal to be extracted, which increases the cost.
• the problem arises of the subsequent evolution of the solvent and the complexing agent, their recycling or their elimination.
• the extraction of the metals is carried out using a nonionic surfactant by phase separation at cloud point.
• a nonionic surfactant by phase separation at cloud point.
• solubilization of the metals in the surfactant micelles can only be done with the aid of lipophilic complexing agents (such as Lix®, Kelex®) whose price is extremely high and which are rarely recyclable.
• lipophilic complexing agents such as Lix®, Kelex®
• the present invention provides a solution to this problem by providing a simple and inexpensive aqueous effluent treatment process, using a liquid / liquid extraction without organic solvent metal pollutants, through their solubilization in mixed micelles consisting of surfactants associated nonionic and ionic
• These mixed micelles formed of two types of surfactants are used for the first time in an industrial application of extraction of metal pollutants. They fulfill several functions related to the combined properties of nonionic and ionic surfactants.
• the surfactant molecules are capable of self-associating into aggregates (among which micelles), in which molecules of variable polarity interacting with the hydrophilic or hydrophobic solubilization sites of said aggregates can be trapped. .
• nonionic surfactants have the property of causing separation of their aqueous solutions in two phases, one of reduced volume fraction containing most of the nonionic surfactant in the form of micellar aggregates ( concentrated phase or coacervate), and the other diluted in surfactant relative to the initial solution.
• This phenomenon however occurs under certain conditions of surfactant concentration and temperature, the medium may also play a role.
• the ternary system consisting of a solute dissolved in water in the presence of a nonionic surfactant at equilibrium can be characterized by a temperature / concentration phase diagram.
• the diagram of a given system has a demixing curve indicating for each composition, the corresponding cloud temperature Tc.
• the subject of the invention is thus a method for treating aqueous effluents using a liquid / liquid extraction without organic solvent, for extracting the metal pollutants alone or simultaneously with the organic pollutants, thanks to their solubilization in mixed micelles consisting of associated nonionic and ionic surfactants.
• This extraction makes it possible to eliminate the two pollutants at the same time, if they are present together in the effluent.
• it can also be used if one of the pollutants (singularly a metallic pollutant) is only present in the effluent.
• the method according to the invention has multiple technical advantages and meets a number of current regulatory and economic constraints. Industrialists concerned by the problem of the elimination of toxic discharges will now have a suitable, efficient and economical technique, applicable on a large scale to the depollution of their aqueous effluents, and allowing them to respect all the regulatory texts of more in more strict.
• the process according to the invention is applicable to aqueous mixtures containing very diverse pollutants. It is thus adapted to the treatment of waste water from various industrial activities, consisting of homogeneous aqueous fluids or loaded with droplets of immiscible liquid and / or solid material. It can therefore be used to treat dispersed pollutants and soluble pollutants present in complex mixtures of contaminants.
• the reduction of polluted volumes without producing a new pollution is a very interesting result of the claimed process.
• the water consumption is in fact minimal or even zero, and the final volume is not significantly increased.
• Purified water also represents a high fraction of the final volume, while a small fraction concentrated in pollutants remains to be reprocessed. Since only surfactant compounds are added, there is no problem of solvent reprocessing.
• the diversity of existing surfactants makes it possible to choose the least toxic and preferably also biodegradable.
• Another advantage of the process according to the invention is that, in certain cases (when the pollutant has an acidic or basic character), the surfactants can be regenerated for later use from the coacervates (low volumes, concentrated in pollutants), but also to be able to recover extracted compounds that can be directly stored as ultimate waste, or better, recovered in other uses if the objective is their reuse.
• a decisive advantage of the process according to the invention is that it is possible to achieve it in a continuous process, at the production site itself, which avoids having to transport the effluents. It does not require heavy equipment and easily adapts to the particular conditions that may vary from one industrial site to another.
• the nonionic surfactant may be chosen as a function of the initial temperature of the effluent to be treated, so that no heating is required to reach the minimum temperature required for phase separation.
• the subject of the present invention is a method for treating an aqueous effluent containing metal pollutants alone or in combination with organic pollutants, essentially comprising the steps of: a) - preparing a solution consisting of an ionic surfactant and at least one nonionic surfactant, b) - contacting the effluent with said solution, c) - stirring the mixture, and if necessary heating to a temperature greater than minus 1 ° C at the cloud point of said mixture, d) - decant until separation into two aqueous phases, one being the concentrated phase of metal pollutants and possibly organic pollutants, and the other being the dilute phase, e) - recover the two phases separately.
• the mixture obtained in b) has a temperature below the cloud temperature, in which case a homogeneous mixture is obtained, which must be heated during step c) to reach the cloud point and cause phase separation.
• the mixture obtained in step b) has a temperature at least greater than 10 ° C. above the cloud temperature of said mixture. Indeed, in this case no heat input is necessary to reach a temperature slightly above the cloud point of the mixture, the latter then dividing spontaneously into two phases.
• This advantageous situation is encountered when the industrial processes lead to the discharge of rather hot effluents (that is, when the cloud temperature of the mixture is lower than the temperature of the effluent), since it is the temperature of the effluent which contributes mainly to the temperature of the mixture.
• the effluent volume is generally much greater than the volume of surfactant solution entering the mixture.
• One way of obtaining an effluent / surfactant solution mixture at a temperature above the cloud point, even when the effluent to be treated is relatively cold, is to choose a nonionic surfactant having a fairly weak cloud point, which is that is several degrees Celsius lower than the temperature of the effluent. In this way, it gives the mixture a cloud temperature lower than the working temperature after mixing, avoiding here also having to heat it.
• the addition of the ionic surfactant increasing the cloud point the choice of the nonionic surfactant giving the mixture the lowest possible cloud temperature will allow to have an operating temperature for the extraction without having to heat.
• the cloud point value measured under standard conditions is available for many known surfactants.
• the cloud temperature of the nonionic surfactant mixed with an industrial effluent can be clearly different from its standard value.
• the choice of the nonionic surfactant must take into account this shift towards generally higher temperatures.
• the inventors have established that the difference ⁇ Tc between these two values is most often less than 5 ° C, and can go up to 10 0 C under certain particular conditions. This observation makes it possible to quickly define the specific conditions for carrying out the process according to the invention for a given effluent.
• the nonionic surfactant may advantageously be chosen from compounds having a cloud point, measured as a 1% solution in water, which is at least 5 ° C., preferably less than 5 ° C. at least 10 0 C, at the initial temperature of the effluent.
• the nonionic surfactant is chosen as a function of the initial temperature of the effluent, among the compounds conferring on the mixture obtained in step b) a lower cloud temperature at least 1 ° C at the temperature of said mixture.
• the cloud point of the effluent to be treated / surfactant solution mixture is determined on test mixtures of the effluent and surfactant solutions. Then The values obtained are compared with those of a model equilibrium diagram, established from ternary mixtures of water / pollutant / surfactant. It is of course advantageous to have a data bank comprising the phase diagrams of many ternary water / pollutant / surfactant mixtures. These diagrams, when they are not available, can be made by measurement on some ternary mixtures.
• the nonionic surfactant is a compound having one or, preferably, several unfilled functional groups containing heteroatoms such as nitrogen or oxygen, for example alcohol, ether, ester, amide groups.
• heteroatoms such as nitrogen or oxygen
• polyethers in alkoxylated surfactants and polyols in surfactants derived from sugars.
• the nonionic surfactant is advantageously chosen from polyethoxylated compounds having a hydrocarbon chain of length
• C 10 to C 16 preferably from polyethoxylated alcohols, pure or in mixtures.
• a number of carbon atoms between 10 and 16 leads to good properties of detergency, adsorption, wetting and solubilization.
• the structural variations of the different alcohols in this mixture play either on the length of the hydrophobic chain, on its degree of branching, or on the degree of ethoxylation of the mixture. hydrophilic part.
• commercial surfactants, non-specific synthetic products are almost always mixtures of compounds: the hydrophobic parts are most often hydrocarbon chains of different lengths.
• the hydrophilic parts have a variable number of ethylene oxide units distributed in a Gaussian or lognormal distribution.
• Formula of a linear polyethoxylated pure alcohol n-CiH 21 + 1 (OCH 2 CH 2 ) j OH, abbreviated n-QE ,, with according to the invention 10 ⁇ i ⁇ 16 and 3 ⁇ j ⁇ 10.
• the nonionic surfactant is an ethoxylated alcohol obtained by fixing the ethylene oxide on a fatty alcohol or oxo in the presence of an alkaline catalyst. It is preferably freed of the residual polyols by washing.
• An oxo alcohol is obtained by the process of the same name allowing the hydroformylation of olefins. It provides a mixture of linear and branched alcohols.
• Ethylene oxide reacts with the various alcohols, without it being possible to obtain a very precise, pure molecule. Hydrophilic parts consisting of mixtures with a normal log distribution of the number of ethoxy units, designated by the formula of the middle alcohol, are finally obtained.
• Formula of a polyethoxylated alcohol oxo OXO-C 1 H 21 + I (OCH 2 CH 2 ) J OH, abbreviated to OXO-C 1 E j , with according to the invention 10 ⁇ i ⁇ 16 and 3 ⁇ j ⁇ 10 .
• the preferred surfactants are those of lower toxicity, especially since their concentration at the end of the extraction is very low (around the CMC, less than 100 ppm). They are indeed at the same time efficient in small dose and biodegradable, they do not induce carcinogenic, mutagenic or teratogenic effect (Ho Tan Ho Tan, 1999, Dunod, Paris). In addition they are also cheap.
• the surfactant solution used in the present process also includes an ionic surfactant.
• an ionic surfactant used alone, plays no direct role in the phase separation process, but in a mixture, it participates in the micellar structure, inserting itself between the molecules of the nonionic surfactant, so that the metal ions are attracted enough to be fixed and concentrated in the coacervate. Its presence also induces a change in the cloud point of the mixture. It must be emphasized that such micelles, known as “mixed micelles" have never been used for the extraction of dissolved metals in effluents.
• the present process can very well be implemented for the depollution of media containing only metal pollutants.
• the ionic surfactants act as complexing agents for the metal ions, whereas the nonionic surfactants make it possible to obtain two phases.
• the ionic surfactant may be an anionic surfactant. It is then preferably chosen from alkylbenzenesulphonates and alkane sulphonates. alpha-olefin sulphonates, petroleum sulphonates, or alkyl sulphates.
• the ionic surfactant is sodium dodecyl sulphate of formula C12H25OSO3 " Na + , or sodium dodecylbenzenesulphonate, a mixture containing, for example, the species of formula CgHi 9 -CH (C 2 H 5 ) -C eH 4 SO 3 " Na + .
• the use of an anionic surfactant will lead to the formation of negatively charged mixed micellar structures which will complex the metal cations by electrostatic interactions.
• the ionic surfactant used in the process according to the invention may be a cationic surfactant. It is then preferably chosen from alkyltrimethylammonium halides, benzethonium halides and cationic derivatives of nitrogenous heterocycles.
• the cationic surfactant is hexadecyltrimethylammonium bromide of the empirical formula CH 3 (CH 2) IS N + (CH S) 3 Br. "The use of a cationic surfactant will lead to the formation of mixed micellar structures positively charged which will complex the metal anions by electrostatic interactions.
• Both types of surfactants are used together, in solution in water or even pure. It is therefore a mixed solution of nonionic surfactant / ionic surfactant which is introduced into the effluent.
• the surfactants constitute mixed micelles, the ionic molecules being inserted into the nonionic micellar structure.
• concentration of nonionic and ionic surfactants must be greater than the Critical Micellar Concentration (CMC) of the mixture.
• CMC Critical Micellar Concentration
• a certain proportion of ionic surfactant relative to the nonionic surfactant will allow the optimal formation of mixed micelles.
• the two types of surfactants must be in concentrations such that the solution of surfactants gives to the mixture, in mass per unit volume of the mixture:
• ionic surfactant from 1% to 10%, preferably from 2% to 5%, of nonionic surfactant, and from 0.1% to 1%, preferably from 0.4% to 0.6%, of ionic surfactant.
• the nonionic surfactant NI and the ionic surfactant I are in an NI / I mass ratio of between 2 and 12.
• an advantage of the process according to the invention lies in the minimal increase of the liquid volumes.
• the effluent E and the solution of surfactants S are mixed in a ratio by volume S / E as low as possible, generally between 0.01 and 0.1.
• steps a) to e) are repeated at least once to treat the diluted phase recovered in step e). Since the distribution of pollutants is based on the same distribution coefficient during each cycle, we obtain raffinates that are increasingly diluted in pollutants. It is therefore possible to take up the dilute phase (the raffinate) until a satisfactory reduction of the pollutants.
• a solution of different surfactants is used. Indeed, it may be interesting to treat the effluent by different surfactants, having a different affinity for the various polluting substances. This is obviously the case for anions and metal cations, which can be extracted in successive cycles of treatment, thanks to the use of cationic and anionic surfactants, respectively.
• the raffinate obtained in step e) is reprocessed or not, it is possible, in certain cases, to recycle the concentrated surfactants in the coacervate, which makes it possible in particular to make the extraction process according to the invention profitable, economically but also ecologically.
• the pollutant has an acidic or basic character
• a method has been developed consisting of the addition of an acid / base pair, which makes it possible to dissociate the pollutant from the coacervate, and then to regenerate the non-surfactant.
• ionic surfactant the ionic surfactant remains complexed with the extracted metal.
• This recycling has the double advantage of ensuring a more thorough depollution and to allow the recycling of useful compounds.
• the term "pollutant" will therefore designate here as well compounds for which the effluent must be disposed of for ecological reasons, as compounds that it is desired to recover in order to enhance them, the two purposes being sometimes confused.
• the surfactants and the pollutant compounds of the concentrated phase obtained in step e) are separated by acid-base de-extraction according to the following procedure.
• the weak acidic pollutant (or weak base) is displaced by the addition of a strong base (or a strong acid).
• the dissociated species no longer interact with the micelle, the complex with the surfactant breaks and the pollutant dissolves preferentially in the water.
• two phases are formed, one containing the concentrated surfactant, the other containing the pollutant (as well as diluted surfactant). The pollutant can then be either destroyed or recovered.
• the nonionic surfactant concentrated in the coacervate is regenerated by neutralization-precipitation. Indeed, at basic pH (or acid), it contains hydroxyl ions (or hydroniums) in high concentration which are ineffective for effiuent treatment. To restore its effectiveness, it is necessary to reduce the pH to a neutral value and also to precipitate the added base (or acid) in the form of salt to eliminate it.
• the coacervate is thus regenerated and, if necessary, constitutes a solution of surfactants according to the invention, active for a new treatment cycle.
• the non-dissociated species (PhOH) is more easily extracted than the ionic species, since it is less hydrophilic. It is therefore the molecular form PhOH which is preferentially retained in the coacervate.
• the acid / base pair used for the desextraction may be oxalic acid / calcium hydroxide.
• De-extraction consists of dissociating the phenol from the nonionic surfactant. Since the ionic form PhO " does not interact with the surfactant head, increasing the pH by adding a base to the surfactant / PhOH complex separates the surfactant from the phenolate. extinguished), to raise the pH sufficiently (by at least two units above the pKa of phenol) to release the phenolate ion which dissolves most of the time in the water. The dilute phase is neutralized with oxalic acid to precipitate its calcium salt, for example phenol, solubilized by the surfactant known as the phenolate. Triton X-114 ® denomination, then desextracted as indicated above, could thus be recovered with a level of 80% phenol.
• step f) for recycling the surfactants in which:
• step e) the surfactants and pollutant compounds of the concentrated phase obtained in step e) are separated by acid-base de-extraction, and
• the surfactants are regenerated by neutralization-precipitation.
• the surfactants regenerated in step f) of the process are used in step a) of a new treatment cycle.
• the present method can be implemented for a very wide range of effiuents to be treated.
• the effluent can be stored in a tank, then treated with a solution of surfactants as described above, after which the two phases are recovered separately.
• the treatment is carried out as and when the effluent production, the different stages of the process taking place in different tanks.
• the steps a) to d) are carried out in separate compartments, according to a continuous process.
• the present process is particularly designed to be applied to the extraction of metal ions, alone or simultaneously with organic compounds contained in aqueous effluents.
• effluents may for example be from industrial activities of manufacturing, cleaning, transport or cooling, including the following industrial activities: metallurgy, mechanics, surface treatment, screen printing, fine chemicals, pharmaceuticals, textile, dyeing, wood.
• a solution Sl, containing 2 g / l of phenol and 1.5 g / l of lead was treated with a solution of surfactants S (TA) according to the following protocol.
• Ionic surfactant sodium dodecyl sulfate (SDS), 288.38 g / mol (Sigma-Aldrich). It contains in its hydrophobic chain 12 carbon atoms.
• Nonionic surfactant OXO-C 10 E 3 ;
• the nonionic surfactant OXO-C10E3 used herein is an ethoxylated alcohol obtained by fixing the ethylene oxide on an oxo alcohol (linear-branched mixture) in the presence of an alkaline catalyst. The presence in the sample of residual polyols that can affect the properties of the surfactant, the latter is preferably washed out. To do this, 25% of water and 75% of the surfactant to be washed are mixed and then heated to 95 ° C. Two phases are then obtained, one rich in surfactant (of the order of 98-99%) and the other rich in polyols.
• the coacervate of surfactant OXO-C 10 E 3 is used directly for extraction. Its standard cloud temperature, measured before washing according to the NFT 1890D standard (10% of surfactant in 75% water + 25% butyldiglycol), is 54-58 ° C. This surfactant is virtually insoluble in water at all temperatures.
• the S (TA) solution is introduced into 25 ml of pollutant-loaded solution S1, so that the surfactant OXO-C10E3 is added to the mixture at a concentration of 4% by weight and SDS at a concentration of 0.38% by weight.
• This mixture is stirred at 800 rpm for 10 minutes. Its initial temperature is 20 0 C (room temperature). The mixture is then heated at 45 ° C. for at least 15 minutes, which allows good phase separation.
• the volume fraction of the coacervate (light phase) is of the order of 0.18.
• the efficiency of the extraction E% of a solute is expressed by the percentage of solute initially dissolved extracted by the coacervate.
• E% (m s (i N ) - HIs (D) / m s ( iN)) x 100 with Hi 8 (DVf) and Hi 8 (D) representing the solute masses respectively in the initial solution and in the phase diluted after extraction.
• Lead was assayed in the diluted phase by Induced Plasma Atomic Emission Spectroscopy (ICP). There is a lead extraction rate of 81%. The phenol content in the diluted phase was measured by reverse phase high performance liquid chromatography (HPLC). A phenol extraction rate of 72% is found.
• ICP Induced Plasma Atomic Emission Spectroscopy
• Ionic surfactant sodium dodecylbenzenesulphonate (SDBS), 348.25 g / mol (Rhodacal DS-10, Rhodia France).
• - Nonionic surfactant OXO-C 10 E 3 , as in Example 1.
• Extraction It is introduced into 25 ml of solution Sl, so that the surfactant OXO-C10E3 is added to the mixture at a rate of 4% by weight and SDBS at a rate of 0.6% by mass.
• the procedure is as in Example 1.
• the initial temperature of Sl is 20 ° C.
• the mixture is heated at 45 ° C. for at least 15 minutes, which allows a good separation.
• the volume fraction of the coacervate is of the order of 0.15.
• a control of the efficiency of the extraction was carried out as previously. There is a lead extraction rate of 80% and a phenol extraction rate of 71.5%.
• a solution S2 containing 1.3 g / l of 2,4-dimethylaniline (DMA) and 1.5 g / l of lead was treated with a surfactant solution according to the following protocol.
• DMA 2,4-dimethylaniline
• Nonionic surfactant oxo-CioE 3
• SDS sodium dodecyl sulphate
• Example 1 The procedure is as in Example 1.
• the initial temperature of S2 is 20 0 C, the mixture is heated to 45 ° C for at least 15 minutes, which allows good phase separation.
• the volume fraction of the coacervate is of the order of 0.25.
• Cationic TA benzethonium chloride.
• Nonionic TA OXO-C 10 E 3 and
• Cationic TA hexadecyltrimethylammonium bromide or CTABr.
• Various tests have been carried out with varying contents of cationic surfactants.
• the nonionic surfactant is provided in all tests at a rate of 0.625 g, or 2.5% by weight, based on the working volume of 25 ml.
• the operating procedure is identical to that described in Example 1.
• the initial temperature of Sl is 20 ° C.
• the mixture is maintained at 50 ° C. for at least 15 minutes.
• the desextraction was conducted on the coacervate as follows.
• the acid / base pair used for the desextraction is here oxalic acid / calcium hydroxide.
• the coacervate was taken up and the oxalic acid added to pH 2 and then heated to 50 0 C to remove the maximum of water hydration molecules. A new separation is then observed in two phases: one rich in solute (new diluted phase), the other rich in surfactant

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