IT202000004138A1 - Ring contactor. - Google Patents

Description

Ring contactor

Technical field of the Invention

The present invention? relating to a three-phase annular contactor for liquid membranes made in a single module. In particular the? Invention? relating to its operation and related methods? of construction.

Known art

The liquid membrane technology allows to separate a target compound, present in liquid or gaseous phase, from the mixture in which? content. In the following you will do? reference only to the separation of compounds present in solution.

Liquid membrane technology? note [1] how it? contactor technology using confined liquid membranes [2,3].

Liquid membranes generally consist of a volume of liquid that is immiscible with the two working solutions with which it comes into contact. The two solutions are called solution? Source? (feed or source) and solution? receiver? (receiving). The source solution? the mixture from which you want to extract a component, the receiver? the solution that welcomes the separated species. In the vast majority of cases the membranes are based on hydrophobic liquids and the solutions? Source? and? receiver? they are generally watery. Therefore the only constraint of technology? that the membranes are immiscible in the target solutions? source? and? receiver ?.

In the generally organic solvent which constitutes the membrane? usually dissolved a suitable solute (carrier) capable of selectively interacting with the substances to be separated, facilitating their transport from the source solution to the receiving solution.

Compared to other separation techniques, such as chromatography, the use of liquid membranes offers the advantage, relevant in some industrial applications, of allowing separation without involving the dilution of the separated species or even allowing a concentration. For these reasons, liquid membranes have received considerable scientific and technological attention in recent decades [1, 4-7].

Liquid membranes can be used in different configurations [1]. From the application point of view, the systems of greatest interest are those of liquid emulsion membranes (ELM), in which the membrane constitutes a liquid film between its source and receiver solutions; and flow systems, which, generally through the use of suitable contactors, allow a continuous separative process [2,6].

Among the flow systems we find those in which the liquid membranes are supported on hollow fibers supported membranes [8-11]. In such systems a thin film of membrane solution? adsorbed on the porous walls of a hollow fiber made of inert polymeric material, inside and outside of which the source and receiver solutions flow. In these systems the membrane solution? adsorbed and enters the pores of the hollow fiber, minimizing the volume of the membrane. The main drawback of this technology? the poor stability? of the membrane solution, which over time is slowly solubilized in the source and receiving solutions. No organic solvents? in fact completely insoluble in water. Furthermore, since? the system works in flow, the mechanical action tends to remove the membrane solution soaked in the hollow fiber.

The separation through the membrane can? take place by reverse osmosis with possible application, for example, in recycling through purification of leachate and sewage [8]. These systems offer the great advantage of a very fast transmembrane transport, with a mechanism very similar to that of solid membranes [12], with respect to which they are more versatile, given the enormous variety? of membrane solvents and carriers that can be used. The weak point of these systems? their poor stability, due to the partial solubility? of the membrane solvent and of the carrier in the source and receiver solutions [6]. Such a problem? amplified by the high values of the volume ratios between the source and receiver solutions and the membrane solution. Therefore these types of membranes do not easily find application.

Systems pi? advantageous are the so-called liquid confined membrane systems [13,14], which provide for the movement (generally assisted by peristaltic pumps) of all the solutions involved in the process, and which can work continuously like systems based on solid membranes, in how much do they have the stability problems? of the membrane characteristic of emulsion and supported membranes. In these systems, the solutions are made to flow inside suitable contactors, generally consisting of hollow fibers which have the function of containing the membrane solutions, separating them from the source and receiving solutions by means of porous surfaces, and allowing permeability. to the solutes [15].

A liquid membrane contactor contained can? be constituted for example by a perforated central tube covered by a first membrane consisting of hollow fibers each having the ends? open, by a second membrane also made up of hollow fibers, and so on? away in order to have a series of sheets consisting of fibers that cover the tube [15]. This single module system can? be used as a gas and liquid separation device and allows the source and receiver solutions to remain separate. Being a single module contactor, it has the disadvantage of allowing only one extraction or removal step of the entire transport process.

Most of the known systems with confined liquid membranes concern the use of double module hollow fiber contained liquid membranes [9]. In these systems, which differ from each other in terms of geometry and modality? fixing fibers [1619], each module? a contactor consisting of a container in which the hollow fibers are housed. In each of the two different modules, two different interfaces are created:? Source? / Membrane in a first module and membrane /? Receiver? in a second module, respectively responsible for the action of extracting the target compound from the source solution and removing it from the membrane solution by the receiving solution [1,5-7]. These systems have the advantage of having a great versatility? of use, given that the transported species can? be varied simply by changing the composition of the three solutions (source, membrane and receiver) and a remarkable stability? system, since all solutions can be easily reintegrated [20-24]. The main disadvantages, on the other hand, are represented by a transport efficiency strongly influenced by the volume of the solutions and by the extension of the contact surfaces. In fact, these systems require large volumes of membrane solution (generally consisting of organic solvents, often toxic and / or harmful to the environment) and suffer from a slowdown of the entire process, due to discontinuity. of the extraction and removal operations, which requires the transfer from the extraction module to the recovery module.

Summary of the invention

AND? A device which overcomes the disadvantages of the prior art has now been developed and constitutes the object of the present invention.

The device of the invention? a single module annular geometry contactor that allows the transport of a solute between two liquid phases consisting of a source solution (F) and a receiving solution (R) by means of a liquid membrane solution confined in the annular geometry compartment created from a pair of coaxial hollow fibers, such that the source solution (F), the receiving solution (R) and the membrane solution flow inside a single module, all in countercurrent with respect to each other. In this way, two interfaces are created and the membrane solution, which constitutes separation between the source solution (F) and the receiving solution (R), is made to flow inside the annular ring formed / bounded by the two tubular fibers or coaxial hollows between them.

Another object of the invention? a process for transporting / transferring a solute from a source solution (F) to a receiving solution (R) by means of a membrane solution confined in the annular contactor according to the invention. This process includes the stages of:

- transfer the solute from the source solution (F) to the membrane solution;

- transfer the solute from the membrane solution to the receiving solution (R).

Said stages being performed in succession.

The process can? be a process of concentration of the solute and in this case the receiving solution (R) will flow? inside the inner / small fiber and the source solution (F) will flow? outside the large fiber.

The process can? be a process of removing the solute and in this case the source solution (F) will flow? inside the internal / small fiber and the receiving solution (R) will flow? outside the large fiber.

Brief description of the figures

Further objects and advantages of the present invention will become clear from the following detailed description of an example of its embodiment (and its variants) and from the annexed drawings given purely for explanatory and non-limiting purposes, in which:

in Figure 1? illustrated a schematic longitudinal section of the contactor A with three units? of treatment;

in Figure 2? illustrated a schematic view of the circled part of Figure 1 which constitutes the end? top of contactor A;

in Figure 3? shown a section along XX of Figure 1, Figures 3a and 3b show two different arrangements of solutions (F) and (R);

in Figure 4? illustrated the variation of the concentration of Cr (VI) (mg / L) as a function of time (min) in the feed solution (in continuous supply) and in the receiving solution (in recirculation) at the output of the contactor.

Detailed description of the invention

Within the scope of the present invention the following definitions are given:

Contactor: device that allows to carry out gas / liquid or liquid / liquid mass transfers, allowing direct contact between two phases without one of the two being dispersed in the other.

Annular geometry: geometry defined by a region bounded by two concentric circles. Unit? of treatment: unit? which includes a pair of coaxial tubular or hollow fibers, the fiber pi? internal being the first fiber, the fiber pi? external being the second fiber. In said unit? the transport of a solute is carried out between two phases consisting of a source solution (F) and a receiving solution (R) by means of a membrane solution. The membrane solution will be? confined in the annular geometry compartment that characterizes the unit? treatment while the source and receiver solutions may be outside the second fiber or inside the first, independently of each other depending on the type of solute transport to be carried out. In this way in the unit? three phase separations are made between the three solutions (source / membrane / receiver) said three solutions being made to flow in countercurrent with respect to each other.

Module: the module? defined as the pi? small unit? containing one or more? unit? treatment and the corresponding support structures, which can? operate independently of the rest of the system.

Confined liquid membrane: liquid membrane in which inert porous supports act as a physical barrier against the mixing of source or feed (F), receiving (R) and membrane solutions.

Carrier: solute soluble in the membrane solution capable of selectively interacting with the compounds to be separated, facilitating their transport from the source solution to the receiving solution.

Pertration: term commonly used in literature [25]. The pertraction can? be defined as an extraction and transport through liquid membranes and consists in the transfer of a solute between two aqueous phases with pH values or other properties. different chemicals, phases separated by a solvent layer of varying volume. The efficiency and selectivity? of the pertraction can be significantly improved by adding one or more? carriers, substances capable of binding the solute in the membrane phase, such as organophosphorus compounds, long-chain amines or corona ethers, in the liquid membrane. The separation process is called facilitated or synergistic pertraction.

The proposed device? it can be used with all possible aqueous solutions and with polar and apolar solvents that comply with the specifications indicated by the manufacturer of the fibers used. By way of non-limiting example, a list of possible compounds that can be used and related applications is given. For example solvents suitable for use as membrane solutions can be: dichloromethane, kerosene and 1,2-dichloroethane and carriers: Aliquat 336 and (-)? Dodecyl bromide? N? Methyl? Ephedrinium).

The proponents have gained experience in optimizing transport conditions in liquid membranes supported by hollow fibers readily available commercially at affordable costs. For example the company

provides polypropylene fibers in the 0.6 range? 1.8 mm inner diameter and firm polypropylene fibers with 0.2 inner diameter? 0.4mm.

In these studies, bulk liquid membrane systems for the selective transport of chiral molecules [26,27] and aromatic amino acids [28] were considered and yes? mainly investigated on the influence exerted by the type and strength of intermolecular carrier-analyte interactions on selectivity? and on the speed? of the transmembrane transport. In particular, cinconidine has shown a good capacity? enantioselective especially towards the D, L-mandelic acid, which has, in addition to the functional groups necessary to give rise to the formation of the hydrogen bond and the electrical interaction of the dipolar type, also a carboxylic group which, following an acid reaction -base with the carrier, can? provide ion pair interaction with quinuclidine nitrogen.

The use of carriers capable of exploiting the simultaneous action of electric interaction of the dipolar type and ion pair has made it possible to obtain, even in the facilitated transport of aromatic amino acids, a better selectivity. compared to the use of pi? conventional ion carriers. The electric interactions of the dipolar and ion pair type are known to those skilled in the art.

On the basis of their own experience, the proponents have studied and developed a single module annular contactor, which is much more? efficient of the two-stage contactors known in the art. The single module contactor? been studied in order to minimize the disadvantages of dual-module liquid membrane systems (such as the slowness of the process and the large amount of membrane solution required due to the discontinuity between the extraction and removal operations) and, at the same time , maintain flexibility? d? use and ease? of use that? characteristic of hollow fiber contactors.

The annular geometry of the device of the invention allows, in fact, to reduce the membrane / exchange surface ratio to a minimum and to vary the volume ratios between the source or feed and receiving solutions simply by alternating the feeding of the solutions inside the fibers. , giving the system great flexibility. The two operations of extraction and removal are then carried out without resorting to the use of double module systems, speeding up the transport process and considerably reducing the volume of membrane solution.

A non-limiting embodiment of the single-module annular contactor according to the invention is described below. The description will far? reference to the attached figures and to the components listed in the following legend:

1, 1?) Cap available in polytetrafluoroethylene (PTFE);

2) first hollow fiber with a smaller diameter;

3a, 3b, 3c, 3? A, 3? B, 3? C) threaded spouts (which can be made of steel) for the supply (inlet / outlet) of the source, receiver and membrane solutions;

4) second hollow fiber with larger diameter;

5) first cylinder (achievable in glass) with a smaller diameter;

6) second cylinder (made of glass) with larger diameter;

7) perforated disc (achievable in polyisobutylene) for the separation between the receiving solution and the membrane solution when the receiving solution flows inside the first fibers with a smaller diameter, vice versa for the separation between the membrane solution and the source solution when the source solution flows inside the first fibers with a smaller diameter;

8) o-rings (available in Viton);

9) perforated disc (available in PTFE) to support the first fiber with a smaller diameter;

10) ferrule with o-ring (available in Viton);

11, 11?) Source or feed solution;

12, 12?) Receiving or receiving solution;

13, 13?) Annular chamber in which the membrane solution flows.

Is the proposed device illustrated in the attached figures? an annular contactor A for pertraction in confined liquid membranes. The device ? characterized by the presence of at least one, generally a plurality? of unit? of treatment which include pairs of coaxial hollow fibers of different diameters which create an annular geometry and which are housed in a shell of material inert towards the working solutions, for example glass or Plexiglas.

The shell? made with a geometry with a regular section, for example, it has a circular section and can? be made as a single element or portioned into a plurality of of coaxial elements and sealed to each other. Advantageously, the shell can? have two elements, made in such a way as to slide longitudinally together in a sealed manner. The shell? also equipped with power supply means for one of the solutions, chosen between source (F) and receiver (R) according to the operation? of contactor A.

Inside the shell are housed, longitudinally arranged, said pairs of coaxial hollow fibers of different diameter between them, such as to create a hollow chamber with annular geometry. In the following, the fiber pairs will be referred to as first and second hollow fibers. They are made to contain the membrane solution tightly.

The extremities bottom and top of the shell are shaped in such a way as to realize, each independently from the other, two chambers or compartments, advantageously superimposed on each other. The two compartments are substantially similar to each other, varying only in size. A first of each of the two compartments houses the ends? of the first hollow fibers and one of the two solutions, chosen between source (F) and receiver (R). A second of each of the two compartments houses the ends? of the second hollow fibers and the membrane solution. The two compartments are equipped with systems for feeding the source (F) and membrane solutions and are equipped with means that allow the source (F), receiving (R) and membrane solutions not to mix with each other.

As mentioned above and with particular reference to the attached figures, the device comprises at least a pair of hollow fibers of different diameters so that the small hollow fibers or first fibers (with a smaller diameter) 2 are inserted inside the large hollow fibers or second fibers (with larger diameter) 4 in a coaxial way to obtain an annular chamber 13 between the pairs of fibers 2, 4 for the entire length of the contactor A in order to house the solution that will go inside the annular chamber 13? to constitute the liquid membrane for the operation of the contactor. Hydrophobic hollow polypropylene fibers with an internal diameter of 1.8 mm (Accurel pp q 3/2) and 0.6 mm (Accurel pp s 6/2) produced by Membrana- GMBH (Wuppertal, Germany) can be used in the device . The fibers with a diameter of 0.6 mm constitute the first hollow fibers with a lower diameter 2 and are inserted inside the fibers with a diameter of 1.8 mm, which constitute the second hollow fibers with a greater diameter 4. At the end? fibers with a larger diameter or second fibers can be advantageously inserted into Tefzel ferrules (ETFE, Upchurch Scientific Oak Harbor, WA, USA) to give them a suitable conical shape; the estate can? be obtained by means of Viton o-rings and other additional elements such as a Teflon disc 9 suitably perforated to allow the flow of the membrane solution and the passage of the smaller diameter fibers.

The smaller diameter fibers or first fibers can be anchored to two polyisobutylene discs 7. These also have the function of separator of the sealed chambers for the introduction of the source and membrane solutions. The correct positioning of the fibers of smaller diameter in the septum can? be obtained with methods within the reach of the person skilled in the art. As an example, the positioning? was obtained by the proponents through the use of syringe needles for veterinary use of sufficient diameter so that, inserted in the septum, they can accommodate the fibers inside them and, once removed, release them in the right position.

This fixing system allows you to easily control the length of the fibers, in order to respect the coaxial configuration.

The pairs of fibers 2, 4 are then inserted into a shell which in the figures? made as a double cylinder consisting of a first cylinder with a lower diameter 5, inserted coaxially into a second cylinder with a higher diameter 6 (cylinders 5, 6 can be made of glass) so as to allow the three solutions (source, membrane and receiver) to flow independently in three confined spaces: the membrane solution is made to flow into the annular chamber 13, 13? between the first and second fibers, while both the source and receiving solutions can be made to slide inside the first fibers 2 (with a diameter of 0.6 mm) or outside the second fibers 4 (with a diameter of 1.8 mm). In this way, the two source / membrane and membrane / receiver interfaces responsible for the extraction and removal processes, characteristic of the transport process using liquid membranes, take place within a single module.

How already? illustrated, the selectivity? of the membrane? obtained through the use of carriers, chosen in such a way as to guarantee efficient extraction at the feed / membrane interface, by means of the formation of stable molecular adducts, and an efficient release at the membrane / receiving interface, regulated above all by kinetic parameters. The expert in the field? able to choose carriers and membranes according to the operations to be conducted in the contactor.

In the proposed device since? the membrane solution flows in the annular cavity, while the source or feed (F) and receiving (R) solutions can alternatively flow inside the first fibers 2 or outside the second fibers 4,? It is possible to have the feed / membrane and membrane / receiving interfaces in a single module.

The annular geometry allows to optimize the ratio between the exchange surface and the volume of the membrane solution, maximizing the transport efficiency. Basically, the annular geometry allows to obtain a transport process similar, in terms of mechanism and efficiency, to that of membranes supported on hollow fibers, while maintaining stability? and flexibility? of use typical of double module systems, mentioned above.

The operation? of the device and the sizing of its parts are within the reach of the expert in the art who, on the basis of his experience and the detailed indications in this description,? capable of realizing the device of the invention and making it work properly, as for example indicated below.

The device of the invention can? be used with different modes? of work that are obtained by inverting the power supply of the source (F) and receiver (R) solutions. These different modes, characterized by different ratios between the volumes of the source and receiver solutions, are suitable for different types of applications. Indeed:

a) by sliding the source solution (F) inside the first fibers 2 with a smaller diameter, the extraction processes are favored and the device can? be used for an efficient removal of chemical species from the source solution (F) towards the receiving solution (R), located outside the second fibers 4 with larger diameter;

b) by sliding the receiving solution (R) inside the first fibers 2 you can? rapidly reaching a condition of transport against a concentration gradient. In this way the concentration of the extracted species in the receiving solution (R) becomes higher than that initially present in the source solution (F). This process ? possible through the use of reagents that in the receiving solution are able to continuously subtract the permeate from equilibrium and maintain thermodynamically favorable transmembrane transport. In this case the transport from the membrane solution to the receiving solution (R) will be? advantageously integrated and assisted by a counter-transport mechanism. To have a thermodynamically favored process, it will be? it is necessary that in the receiving solution there is a strong acid (HNO3 or HCl) capable of subtracting the analyte by protonation; in this way the anion (NO3 <-> or Cl-) could? guarantee counter-transport.

The use of the contactor in the mode? b) can therefore be advantageous in cases where it is necessary to combine the separation and pre-concentration operations.

A favorite embodiment of the invention? shown in Figure 1. In order to give the device the necessary chemical inertness, the terminal elements of the device for fixing the fibers and for introducing the solutions into the contactor can be made in Teflon. They can be designed in such a way as to guarantee easy assembly and a perfect seal, obtained with the aid of commercial Viton gaskets. The construction details are within the reach of the person skilled in the art.

The external part (shell or shell) can? be constituted by two cylinders connected to each other in a telescopic way or through another system that allows to obtain an adjustable tension of the fibers so as to be able to adjust and if necessary restore the good alignment of the fibers but without causing twisting to said fibers, which would cause the device to malfunction.

The power supply of the solutions inside the contactor? obtained by means of peristaltic pumps connected to the chamber outlets of the various solutions. The pumps maintain the proper pressure and speed. flow of the various solutions in order to optimize the transfer processes. The identification of the optimal conditions? within the reach of the person skilled in the art.

MAIN AREAS OF APPLICATION

The contactor? extremely versatile and can? be used with all solvents that comply with the specifications relating to the fibers and materials used (for example solvents suitable for use as membrane solutions can be: dichloromethane, kerosene and 1,2-dichloroethane and carriers: Aliquat 336 and (-) ? Dodecyl bromide? N? Methyl? Ephedrinium).

The dimensions of the device are scalable and it can? be used both for analytical purposes, for example as a separation and purification system, and as a selective preconcentration system. The three-phase operating principle (source (F) and receiver (R) solutions and membrane solution) of the contactor, based on the use of pairs of coaxial hollow fibers, can? be easily transferred on an industrial scale, and? therefore potentially able to cover applications in all fields of interest of liquid membrane technologies (chemical, pharmaceutical, biotechnological, environmental etc).

The main advantages of the proposed device are:

- flexibility that is, it allows to purify a mixture or to pre-concentrate a species present in a dilute solution

- speed? the process of transferring the target compound (which takes place in a single step / module)

- savings in the volume of solvent used

- possibility? to eliminate the target species from very diluted solutions

Another advantage of the annular contactor, described in the preferred embodiment of the invention,? given by the fact that for the fixing of the fibers not? the use of adhesive substances is foreseen, which are generally chemically attacked by the organic solvents used for the membrane solution.

Without what there? is considered to be limiting of its scope, hereinafter a preferred embodiment of the device of the invention is described.

Description of a preferred embodiment of the invention

The device ? formed by three units? treatment comprising pairs of coaxial hollow fibers (2 and 4, Figures 1 and 2) which are arranged in a glass shell sectioned into two units? telescopic sliding seal (5 and 6, Figure 1).

The 0.6 mm fibers (2, Figures 1 and 2) were interlocked onto a polyisobutylene disc (7, Figure 2).

Ferrules were inserted at the ends of the 1.8 mm fibers (4, Figure 2) (10, Figure 2). Viton O-rings <? > (8, Figure 2) sealed the various parts and a PTFE disc (9, Figure 2) exerted the necessary pressure on each ferrule (10, Figure 2). The use of steel threaded nozzles (3a, b, c and 3? A, b, c, Figures 1 and 2) made it possible to mechanically create the necessary thread in the PTFE parts; also to fill the gaps at the steel / PTFE interface? a suitable filler was used, which adhered to the steel better than the glue.

In the device, the membrane solution flows in the annular cavity, while the feed and receiving solutions can alternatively flow inside the 0.6 mm diameter fiber and outside the 1.8 mm diameter fiber (Figures 3a and 3b).

In particular, when the feed solution passes inside the 0.6 mm diameter fibers (Figure 3a), the transport from the feed to the receiving leads to a strong dilution of the analyte, while when the same solution flows outside the 1.8 mm fibers mm (Figure 3b), the transport itself tends to concentrate the analyte in the receiving solution. In this way, the device can? facilitate the enrichment of the permeate in the receiving solution or facilitate the efficiency of extraction of the permeate from the feed solution. All the solutions flow inside the contactor, thus making a continuous flow separation possible.

Implementation variants of the described non-limiting example are possible, without however departing from the scope of protection of the present invention, including all the embodiments equivalent for a person skilled in the art, to the content of the claims.

DEVICE OPERATION EXAMPLE: SEPARATION OF Cr (III) and Cr (VI)

A selective procedure is described for the determination of trivalent and hexavalent chromium in liquid samples through the use of the annular liquid membrane contactor of the invention and analysis with an inductively coupled plasma spectroscope with optical detection.

The performance of the proposed method was evaluated in terms of extraction efficiency of hexavalent chromium (E%) and percentage variation coefficient (relative standard deviation, expressed as a percentage); these were found to be above 85% and below 5%, respectively.

1,2-dichloroethane? was chosen as a membrane solvent why? it does not damage the parts of the annular contactor and provides a good solubilization of the carrier [(-) - N-dodecyl-N-methylephedrinium bromide] and a poor solubility? of Cr (VI). As a receiving solution,? HNO3 was chosen which, by protonating the Cr (VI), favors its passage from the membrane to the receiving solution. The maximum extraction efficiency? was achieved with an HNO3 concentration of 0.75 M.

Figure 4 shows the concentrations of Cr (VI) measured in the feed and receiving solutions at the device outlet by making the receiving solution flow inside the first fiber (with a smaller diameter). After about 1 hour of operation, the concentration in the receiving solution was equal to that of the source solution, and then increased almost linearly for longer times. This characteristic ? particularly interesting for another possible application, namely as a system for the pre-concentration of the analyte.

The data in Table 1 refer to the percentages of solute removal from the source solution by making the receiving solution flow inside the first fiber (with a smaller diameter). By examining the percentage of extraction efficiency (Table 1), one can? note an almost quantitative yield for flow rates lower than or equal to 0.30 mL / min. The annular contactor? able to operate with a good extraction efficiency even in the range of Cr (VI) concentrations typical of different environmental matrices, such as groundwater, lake water, tap water and waste water. Cr (III) is not removed from the source solution since? the transportation process? selective.

Table 1. Percentage extraction efficiency (E%) depending on the concentration of Cr (III) and Cr (VI) and the flow rate (mL / min) of the annular contactor with feed inside the first fibers with a smaller diameter and receiving al outside the second larger diameter fibers, with membrane solution and receiving solutions in recirculation.

Claims (13)

CLAIMS 1. Contactor (A) provided with a shell (5, 6) with ends (1, 1?) Comprising at least one? Unit? treatment for the transport of a solute between two phases consisting of a source solution (F) and a receiving solution (R) by means of a membrane solution, confined in the annular geometry compartment of the unit? of treatment and what? made between a pair of tubular or hollow fibers coaxial with each other, the fiber pi? internal (2) being the first fiber, the fiber pi? external (4) being the second fiber and the source and receiving solutions being placed independently of each other inside the fiber pi? inside and outside the fiber pi? external. 2. Contactor according to claim 1 in which the source solution (F), the receiving solution (R) and the membrane solution flow inside a single module, all in countercurrent with respect to each other, the solution of membrane, which constitutes separation between the source solution (F) and the receiving solution (R), being made to slide inside the annular ring formed by the coaxial fibers. 3. Contactor according to claims 1-2 in which the contactor? provided with means for feeding the source (F), receiving (R) and membrane solutions. 4. Contactor according to any one of claims 1-3, inside which are housed, longitudinally arranged, the pairs of coaxial hollow fibers of different diameters, consisting of a first and a second hollow fiber and such as to create a hollow chamber with annular geometry. 5. A contactor according to claim 4 wherein the pairs of hollow fibers are made so as to hermetically contain the membrane solution. 6. Contactor according to any one of claims 1-5 wherein the shell (5, 6)? made in at least two concentric sections sliding together and sealed. 7. Contactor according to any one of claims 1-6 wherein each of the ends? bottom and top of the contactor? shaped in such a way as to create, each independently from the other, two overlapping chambers or compartments that are sealed against each other and with respect to the shell. 8. Contactor according to any one of claims 1-7 wherein each end is ? provided with two compartments; a first of each of the two compartments houses the extremities? of the first hollow fibers and one of the two solutions, chosen between source (F) and receiver (R); a second of each of the two compartments houses the ends? of the second hollow fibers and the membrane solution. 9. Contactor according to claim 8 in which the two compartments are provided with systems for feeding the source (F) and membrane solutions and are separated from each other and with respect to the shell so that the source (F), receiving ( R) and membrane do not mix with each other. 10. Contactor according to any one of claims 1-9 wherein said shell? made with a geometry with a regular section, and? portioned in a plurality? of elements coaxial with each other, at least two elements, made in such a way as to slide longitudinally together in a sealed manner. Process for transporting a solute from a source solution (F) to a receiving solution (R) by means of a membrane solution confined in an annular contactor according to any one of claims 1-10 comprising the steps of: - Transfer the solute from the source solution (F) to the membrane solution; - Transfer the solute from the membrane solution to the receiving solution (R) said stages being performed in succession. 12. Process according to claim 11 that? a solute concentration process and the receiving solution (R) flows inside the first fiber and the source solution (F) flows outside the second fiber. 13. Process according to claim 11 that? a solute removal process and the source solution (F) flows inside the first fiber and the receiving solution (R) flows outside the second fiber.