EP2126023A1

EP2126023A1 - Decontamination, stripping and/or degreasing foam containing solid particles

Info

Publication number: EP2126023A1
Application number: EP08716848A
Authority: EP
Inventors: Sylvain Guignot; Sylvain Faure
Original assignee: Areva NC SA; Commissariat a lEnergie Atomique CEA
Current assignee: Orano Cycle SA; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2007-02-15
Filing date: 2008-02-14
Publication date: 2009-12-02
Anticipated expiration: 2028-02-14
Also published as: KR101524655B1; CA2678112A1; RU2009134115A; ZA200905366B; CA2678112C; JP5663170B2; EP2126023B1; RU2470068C2; US20100069281A1; KR20090114441A; FR2912668A1; CN101605880A; ES2525618T3; US8772357B2; FR2912668B1; CN101605880B; JP2010518250A; WO2008101855A1

Abstract

The present invention relates to a stabilized foam that comprises a foaming aqueous solution containing from 0.1 to 7 moles of one or more decontamination, stripping and/or degreasing reagents per litre of solution, and from 0.01 to 15 wt % of a solid stabilising agent of the solid-particle type relative to the total weight of the solution. The invention also relates to a method for preparing said stabilised foam, to the use thereof for decontaminating, stripping and/or degreasing a surface, and to a method for decontaminating, stripping and/or degreasing a surface.

Description

DECONTAMINATION, STRIPPING AND / OR DEGREASING FOAM WITH SOLID PARTICLES.

DESCRIPTION

TECHNICAL AREA

The present invention relates to the field of decontamination, stripping and degreasing surfaces. The surfaces to be treated in the context of the present invention may be metal surfaces or not, more or less accessible and contaminated with grease, by radioactive mineral deposits, by an oxide layer or in the mass.

Thus, the present invention provides a solution, a composition and a foam for decontaminating, etching and degreasing such surfaces. The composition and the solution according to the present invention make it possible to obtain a foam capable of decontaminating, pickling and / or degreasing any type of surface and, more particularly, a foam containing a solid stabilizing agent such as solid particles. The present invention also relates to a process for preparing said foam and its use.

STATE OF THE PRIOR ART

In the state of the art, numerous decontamination, pickling and / or degreasing compositions are known for the treatment of surfaces. These compositions can be in the form of both gels and foams.

The applicant's previous work has notably made it possible to develop a gelled (or viscose) decontamination foam containing from 0.2 to 2% by weight of organic surfactant (s) foaming agent (s) from 0.1 to 1.5% by weight of gelling agent and from 0.2 to 7 M of acid (s) or inorganic base (s) for radioactive decontamination. Such a gelled foam is described in international application WO2004 / 008463. This foam has many advantages vis-à-vis the compositions and, especially, vis-à-vis the decontamination compositions of the state of the art. These advantages include an increased life span, better efficiency in the treatment of surfaces and a decrease in the amount of effluent produced.

An object of the present invention is to provide a foam having properties further improved over the foams described in the international application WO2004 / 008463. The improvements relate, in particular, the amount of surfactant (s) necessary (s) to form a given volume of foam, the amount of gelling agent to stabilize the foam and the treatment of products obtained at the end of the life of the foam once the decontamination, stripping and / or degreasing performed. SUMMARY OF THE INVENTION

Thus, the work of the Applicant has made it possible to develop a foam useful in the decontamination, stripping and degreasing of surfaces which has not only the properties of the gelled foams of the state of the art (such as increased service life). , a better efficiency in the treatment of surfaces and a decrease in the amount of effluents produced) but also the improvements described above. This objective is achieved by means of a stabilized foam comprising a solid stabilizing solid particle type agent.

Indeed, the stabilized foam of the present invention has a long life, between 1 and 24 hours, ensuring a prolonged contact time with the surface to be treated and a maintenance on this surface of a foam having a certain humidity. These advantages are particularly interesting when the surface to be treated includes hot spots. The life time of the stabilized foam according to the invention makes it possible to obtain a decontamination, pickling and / or significant degreasing efficiency and to find the same decontamination efficiencies as in the case of washes with decontaminating solutions.

Moreover, in the case of the decontamination by projection of a stabilized foam according to the invention on surfaces, the extension of the duration The life of this foam makes it possible to reduce the projected quantities, which is particularly advantageous.

The foam consists of a dispersion of air bubbles in liquid and is often characterized by its expansion (F), defined under normal conditions of temperature and pressure, by the following relation: foam / liquid \ liquid gas The stabilized foam according to the invention has initial expansion at the generator outlet of the order of 5 to 20, and, in the case of nuclear decontamination, 10 to 15, which makes it possible to treat a large volume ( for example 100 m ³ ) with less than 10 m ³ of liquid.

Finally, after the natural drainage of the foam, the contaminated liquid is recovered, and the wall is rinsed with very little water (about 1 1 / m ² ). In this way, few liquid effluents are produced, which allows a simplification in terms of overall treatment stream thereafter (less evaporation to achieve to meet the specifications of the storage packages).

Furthermore, the stabilized foam according to the invention makes it possible, like the gelled foams described in the international application WO2004 / 008463, to eliminate the radioactivity of inaccessible installations, of large size, or of complex geometry, by filling ("static" action ") , by circulation, or by spraying on an accessible surface.

To treat, for example, the internal surfaces of large volume fission product tanks (20 to 100 m ³ ), where the dose rate is very high (up to 40 Gy / h) and the reduced access possibilities , the use of a decontaminating foam filling the tank is particularly recommended. Indeed, the foam limits the dead volumes of liquid, occupying the entire space and wetting all surfaces such as cooling coils and other equipment in the middle or in the tank.

The introduction of a solid solid-type stabilizing agent into the foam according to the invention has, in addition to the advantages developed above, the following original and unexpected advantages: the reduction or even the suppression of the amount of surfactants necessary for to form a given volume of foam, reducing or eliminating the amount of conventional biodegradable organic gelling agent, the possibility of sorption of chemical entities, such as pollutants or radioelements, detached from the surface to be treated,

- the treatment of products at the end of the life of the foam once decontamination, stripping and / or degreasing. Indeed, the stabilized foam of the invention can be stabilized only by the mineral and / or organic particles it contains. The quantities of reagents necessary for the mineralization of the liquid effluent generated and the duration of the treatment (cost) are thus reduced.

When the stabilized foam according to the present invention additionally contains a conventional organic stabilizer (or viscosifier) stabilizer of the prior art, the amount of said gelling agent is less thanks to the compensating action of the particles. This compensatory gain in stability provided by the particles comes either from the clogging of the flow channels in the foam retarding the drainage of the liquid, or, for large concentrations of particles (and depending on the nature of the particle and the foaming medium), by proper viscosification of the liquid. The solid stabilizing agent of the solid particle type of the stabilized foam according to the invention can be positioned at the gas / liquid interfaces by partly replacing the foaming surfactants, which allows a reduction in the amount of surfactant used.

The solid stabilizing agent of the solid particle type can capture chemical entities and in particular the unhooked elements of the surface to be treated. This capture may consist of a conventional sorption (if the solid particles are present in the solution), or of a coprecipitation (if the solid particles are formed in situ). As part of the decontamination of nuclear facilities, the decontamination factors obtained with such particles are often greater than 100. Moreover, the sorption takes place in the foam and can also be continued in the drained liquid.

In addition, after drainage, the solid particles that have or have not captured chemical entities are easily recovered, for example, by decantation or filtration.

The present invention therefore relates to a stabilized foam consisting of an aqueous foaming solution containing: from 0.1 to 7 moles of one or more reagents for decontamination, pickling and / or degreasing per liter of solution, and

from 0.01 to 25% by weight of a stabilizing solid agent relative to the total weight of the solution.

In the context of the present invention, the term "solid stabilizing agent" means any solid substance which, incorporated in the aqueous foaming solution, makes it possible to improve the stability of the foam obtained from the latter. The stabilizing effect obtained can cause not only the formation of a large volume of foam but also lead to a greater persistence of the formed foam. The solid stabilizing agent in the context of the present invention may be a single solid stabilizing agent or a mixture of solid stabilizing agents of the same or different nature. Advantageously, the solid stabilizing agent used in the context of the present invention is in the form of solid particles. Solid particles of the same nature or mixtures of solid particles of different types can be used in the present invention.

The stabilized foam consisting of an aqueous foaming solution object of the present invention contains at least one foaming and / or sorbent solid agent.

In a first embodiment of the present invention, the solid stabilizing agent, in the form of solid particles, may also have foaming and / or sorbing properties. Thus, in this first case, the use of foaming stabilizing solid agents, sorbent stabilizing solid agents, solid stabilizing, foaming and sorbating agents and mixtures thereof is particularly contemplated. In a second embodiment of the present invention, a solid agent having foaming and / or sorbing properties is added to a solid stabilizing agent. Thus, in this second case, the use of a mixture comprising at least one solid stabilizing agent and at least one foaming solid agent is particularly contemplated; a mixture comprising at least one stabilizing solid agent and at least one solid sorbent agent; and a mixture comprising at least one solid stabilizing agent and at least one solid foaming and sorbing agent. The following definitions concerning the solid stabilizing agent (solid particles, nature and form) also apply to solid foaming and / or sorbing agents.

The cesium-sorbent nickel ferrocyanides ppFeNi are an example of a solid agent with sorbent properties. The colloidal silica particles with a diameter of 650 nm, at 54 g / l, and grafted with aminopropyltriethoxysilane at the rate of 15 molecules per nm ² are an example of a solid agent with foaming properties.

In the context of the present invention, it is also envisaged to use compounds as defined in the first embodiment combined with mixtures as defined in the second embodiment.

The stabilizing solid agent such as solid particles is present in the foaming aqueous solution constituting the stabilized foam according to the invention, in a content ranging from 0.01% to 25%, especially from 0.05% to 10% by weight. weight, in particular from 0.1% to 5% by weight and more particularly from 0.5% to 3% by weight, relative to the total weight of the solution. When foaming and / or sorbent solids are added in addition to pure solid agents stabilizers, the percentage by total weight of solid agents is less than or equal to 30%.

The solid stabilizing agent such as the solid particles may be spherical or perfectly arbitrary and have a monodisperse or polydisperse size distribution. Advantageously, the solid particles have characteristic dimensions of between 2 nm and 200 μm and in particular between 5 nm and 30 μm. The solid stabilizing agent may be in the form of fully inorganic (i.e. entirely inorganic), all-organic, solid particles or inorganic-organic hybrid particles or a mixture of at least two of these types of the same or different particles. The hybrid character may consist of an organic core and a mineral surface, or vice versa.

In addition, that the solid particles used in the present invention are mineral and / or organic as explained above, their surface may be either homogeneous hydrophilic or homogeneous hydrophobic, or have hydrophilic surface areas and representing 0, 01 to 99.99% of the total area, the remainder of the surface (99.99 to 0.01% of the total area) being hydrophobic. In the case where these two types of zones are distinctly separated, the particles are called "amphiphilic particles".

Finally, the solid particles according to the invention can be functionalized by grafting organic molecules. Organic molecules to be grafted onto the solid particles according to the invention have the advantage in particular to improve the sorption properties of chemical entities, such as radioelements, detached from the surface to be treated. In this case, the organic molecules may be organic extracting and / or complexing molecules such as polydentate ligands (for example EDTA-ethylenediaminetetraacetic acid), calixarenes or crown ethers. In a variant, the organic molecules grafted onto the solid particles may be used to modify or improve the hydrophilic, hydrophobic or amphiphilic nature of said particles. Those skilled in the art know different organic molecules that can be used to obtain these different results.

Listed below are various types of solid particles that can be used in the context of the present invention and given as non-limiting examples. Among the inorganic solid particles according to the invention, there are particles of phosphotungstic acid, nickel ferrocyanide, oxide, hydroxide, carbonate, sulfate, nitrate, oxalate and / or titanate of one or more (for example, a mixed aluminosilicate oxide) species selected from alkali metals (e.g.

Na 2 <0. Al2O3.4SiO2), alkaline earth (for example

CaO-Fe ₂ O ₃ , CaCO ₃ , BaSO ₄ , BaTiO ₃ , Ca ₃ (PO ₄ ) ₂ ), transition

(for example TiO ₂ , Fe ₂ O ₃ , ZrO ₂ , MnO ₂ ), and metalloids (for example SiO ₂ ). Such solid particles are in particular available from ACROS ORGANICS. Advantageously, as solid inorganic particles sorbent radioelements and usable in the context of the present invention, mention may be made of particles Ca ₃ (PO ₄ ) 2, CaCo 3, MnO 2, phosphotungstic acid (H ₃ PO ₄ .12WO3. xH ₂ O) and nickel ferrocyanide (ppFeNi). Indeed, the strontium is captured in basic medium (pH> 11) by Ca ₃ (PO ₄ ) 2, CaCO ₃ or MnO ₂ . Cesium is taken up in an acid medium by phosphotungstic acid (H ₃ PO ₄ .12WO ₃ · xH ₂ 0), and in a moderately basic medium (pH <10) with nickel ferrocyanide ppFeNi. Apart from nickel ferrocyanide, formed in situ by the reaction between potassium ferrocyanide and nickel sulphate, all these reagents are available for example from ACROS ORGANICS.

In the context of the present invention, the entirely organic particles are composed of thermoplastic and / or thermosetting polymers and copolymers and / or of biopolymers. Advantageously, the organic solid particles are solid particles of thermoplastic polymers or copolymers of the following families:

Table 1: Polymers composing the organic particles used

To this list are added the families of thermosetting polymers or copolymers, such as aminoplasts (urea-formaldehyde resins), polyurethanes, unsaturated polyesters, phenoplasts (phenol-formaldehyde resins), polysiloxanes, epoxy resins, allylic resins. and vinylesters, alkyds (glycerophthalic resins), polyureas, polyisocyanurates, poly (bismaleimide), and polybenzimidazoles. The particles resulting from these polymers are synthesizable by radical, anionic or cationic polymerization, polycondensation, copolymerization / copoly-condensation, thermally, photochemically, radiochemically, and this in emulsion, in suspension, and by precipitation. The precursors at the base of these polymers are available from ALDRICH, ACROS ORGANICS, FLUKA and ARKEMA. Finally to this list, add biopolymers, such as microbial biopolymers

(polyhydroxyalkanoates and derivatives), biopolymers derived from plants (eg starch, cellulose, lignin and derivatives), and biopolymers derived from the chemical polymerization of biological entities

(polylactics).

The organic solid particles may also consist of copolymers containing the monomer units at the base of the above polymers, for example poly (vinylidene chloride) -co-poly (vinyl chloride) or poly (styrene / poly) copolymers. acrylonitrile).

In the context of the present invention, the organic / inorganic hybrid solid particles may have a surface at least a portion of which is mineral and an organic core, or vice versa. Advantageously, these inorganic-organic hybrid particles have either an organic core consisting of at least one chemical compound chosen from the compounds usable for the organic solid particles previously described and a surface of which at least a part is mineral and composed of at least one chemical compound chosen from the compounds that can be used for the mineral solid particles previously described,

or a mineral core consisting of at least one chemical compound chosen from the compounds usable for the mineral solid particles previously described and a surface of which at least one part is organic and consists of at least one chemical compound selected from the compounds usable for organic solid particles previously described. It is clear that, in the present invention, variants are envisaged both hybrid particles with an organic core and whose entire surface is mineral (or the opposite, namely a mineral heart and the entire organic surface) that the particles hybrids which have an organic (or mineral) core and whose surface has a hydrophilic mineral part and a hydrophobic organic part. The latter type of particles corresponding in particular to amphiphilic particles which are also hybridized is described in Reculusa S., Poncet-Legrand C. Hybrid dissymetrical colloidal particles - Chem. Mater. 2005, 17, 3338-3344. The hybrid particles may have an organic surface portion and a mineral surface portion. These hybrid particles may, for example, be prepared by epitaxial growth in the vapor phase (or chemical vapor deposition) or liquid (by chemical precipitation of a mineral layer on an organic particle). In the latter case, mention may be made of hybrid particles polystyrene (or polyisoprene) coated with TiO 2 or SiO 2 described in patent No. EP 1 053 277. The particles of opposite configuration (mineral core and organic surface) can be easily formed by coating mineral particles by the previously detailed polymers. On the other hand, these synthetic techniques make it possible to form amphiphilic heterogeneous inorganic or organic particles, included in the list of particles that may be suitable for formulating the foams of the present patent.

Finally, the hybrid particles may also be, for example, mesoporous silica particles on the surface of which are grafted organic extractant or complexing molecules such as polydentate ligands (for example EDTA - ethylenediaminetetraacetic acid), calixarenes or ethers crowns.

The foaming aqueous solution constituting the stabilized foam according to the invention comprises a decontamination, pickling and / or degreasing agent. Such an agent is chosen according to the use for which the foam is intended. When the foam is a decontamination foam, the active agent is chosen in particular according to the nature of the contamination and the surface to be decontaminated.

Advantageously, the decontamination, pickling and / or degreasing agent is chosen from an acid or a mixture of acids, a base or a mixture of bases, an oxidizer (for example H 2 O 2), a reducing agent, a disinfectant, a antioxidant, antiseptic, etc. Those skilled in the art will know how to choose the decontamination, pickling and / or degreasing agent according to the treatment to be carried out. More particularly, the decontamination, stripping and / or degreasing agent can be chosen from a mineral or organic acid

("Acid foam"), an inorganic base ("alkaline foam"), an oxidizing agent ("oxidizing foam") or mixtures thereof and, most particularly, an acid-oxidizing mixture or a base-oxidizing mixture. Thus, in the context of a decontamination treatment according to the present invention, an acidic or alkaline foam may have either radiation-dissolving properties of radioactive deposits, for example for the elimination of non-fixed contamination on a surface, or Controlled corrosion properties of the surface for a fixed contamination on it.

According to a first variant, the decontamination, pickling and / or degreasing agent is a mineral acid chosen from hydrochloric acid, nitric acid, hydrofluoric acid, sulfuric acid, phosphoric oxalic acid, formic acid, citric acid, ascorbic acid, and mixtures thereof. According to the invention, the acid is advantageously present at a concentration of from 0.1 to 7 moles, especially from 0.2 to 6 moles, in particular from 0.5 to 5 moles and more particularly from 1 to 4 moles. These concentration ranges naturally relate to the H ⁺ ion concentration given for the preparation of 1 liter of foaming solution.

According to a second variant, the decontamination, pickling and / or degreasing agent is a mineral base chosen from soda, potassium hydroxide, sodium or potassium carbonate and mixtures thereof. According to the invention, the base is advantageously present at a lower concentration 4 mol.l ^"" ^", preferably from 0.5 to 1, 5 mol.l ^λ. These concentration ranges relate, of course OH ion ^{concentration"} given for the preparation of 1 liter of foaming solution.

The foaming aqueous solution constituting the stabilized foam according to the invention may further comprise a surfactant, a mineral oxidizing agent, a complexing agent and / or an organic gelling agent.

Indeed, the foaming aqueous solution constituting the stabilized foam according to the invention may comprise at least one surfactant, and, more particularly, a single surfactant or a mixture of at least two surfactants chosen from foaming surfactants. nonionic surfactants, anionic or cationic foaming surfactants, amphoteric surfactants, Bolaform type surfactants, Gemini type surfactants and polymeric surfactants. More particularly, the stabilized foam according to the invention may comprise a single surfactant or a mixture of at least two surfactants chosen from alkylpolyglucosides, sulfobetaines, alkanolamides and block copolymer surfactants (such as block copolymers). based on ethylene oxide or propylene), ethoxylated alcohols and amine oxides.

In a first variant of the present invention, the surfactant used is a foaming nonionic surfactant. Such a surfactant Foaming nonionic is described in international application WO2004 / 008463. It is, for example, chosen from the family of alkylpolyglucosides or alkylpolyetherglucosides, natural derivatives of glucose and biodegradable. These are, for example, the "ORAMIX CG-110" from the company SEPPIC, or the "Glucopon 215 CS" from the company COGNIS.

In a second variant of the present invention, the surface-active agent used is an amphoteric surfactant, for example from the family of sulphobetaines or alkylamidopropylhydroxy-sulphobetaines, such as the "AMONYL 675 SB" marketed by the company SEPPIC, or from the family of amine-oxides such as "AROMOX MCD-W", cocodimethylamine oxide marketed by the company Akzo Nobel.

In the foaming aqueous solution constituting the stabilized foam according to the invention, the surface-active agent is present in a proportion of from 0.01 to 2% by weight, in particular from 0.1 to 1.8% by weight, in particular from 0, 2 to 1.5% by weight, and most preferably from 0.5 to 1% by weight relative to the total weight of the solution.

In addition, the foaming aqueous solution constituting the stabilized foam according to the invention may also contain a mineral oxidizing agent, advantageously chosen from potassium permanganate, cerium (IV) salts, potassium dichromate and mixtures thereof. According to the invention, the concentration of oxidizing agent in the foaming solution is less than or equal to 1 M, in particular between 0.05 to 0.5 M, in particular between 0.1 to 0.4 M and more particularly between 0.2 to 0.3 M.

In addition, the foaming aqueous solution constituting the stabilized foam according to the invention may also contain a complexing agent advantageously chosen from carbonates and polydentate ligands such as EDTA at concentrations of less than or equal to 1 M, in particular between 0, 01 and 0.5 M, in particular between 0.02 and 0.1 M and more particularly between 0.05 and 0.1 M.

Finally, according to the present invention, the foaming solution constituting the stabilized foam may comprise, in addition to the components mentioned above, an organic gelling agent (or viscosizing agent) in a content of less than or equal to 0.05% by weight, in particular less than or equal to to 0.04% by weight and in particular less than or equal to 0.02% by weight relative to the total weight of the solution.

This gelling agent is advantageously a biodegradable gelling agent, more particularly, chosen from heterogeneous polyholosides such as pectins, alginates, agars, carrageenans, locust bean meal, guar meal and xanthan gum.

The stabilized foam according to the present invention can be prepared in different ways. The present invention relates to a method for preparing a stabilized foam as defined above. In a first embodiment of this preparation method, the various components of the foaming aqueous solution constituting said foam ie the active agent for decontamination, pickling and / or degreasing, the solid stabilizing agent and, optionally, the surfactant, the oxidizing agent, the complexing agent, the gelling agent and / or the solid foaming and / or sorbing agent are mixed together to form an aqueous solution prior to generating the foam. The introduction of these different components into the mixture can be carried out in any order. In case of particularities in the introduction of these agents, the skilled person will know how to choose, thanks to this knowledge, the order of introduction according to the agents implemented.

In a variant of this first embodiment of the preparation process, the solid stabilizing agent may be formed in situ in the mixture. As previously explained, this is particularly the case when the solid stabilizing agent consists of solid particles of nickel ferrocyanide. This in situ training can be more or less fast. It can in particular take place in the presence of the contaminating chemical entities which, therefore, can be coprecipitated with the solid particles thus formed. In a second embodiment of this preparation method, the various components of the foaming aqueous solution constituting said foam ie the active agent for decontamination, pickling and / or degreasing and, optionally, the surfactant, the agent solid stabilizer, the solid foaming and / or sorbing agent, the oxidizing agent, the complexing agent and / or the gelling agent are mixed together, all or part of the solid stabilizing agent and / or all of the solid foaming agent and / or sorbent being brought directly into the gas to form a smoke contacted with the foaming liquid and generate the foam.

In a first alternative of this second embodiment of the preparation method according to the invention, the solid stabilizing agent is not present in the initial aqueous mixture and is provided only by the gas.

In a second alternative of this second embodiment of the preparation method according to the invention, the solid stabilizing agent is not only brought directly by the gas but also present in the aqueous mixture as in the conditions as presented in the first embodiment. implementation of the preparation process (ie stabilizing solid agent mixed with the other components or product in situ during mixing).

The same alternatives as those described above for the solid stabilizing agent apply to the solid foaming agent and / or sorbent.

However, in order to better highlight the various alternatives envisaged with regard to the processes for preparing the stabilized foam according to the present invention, Table 2 below shows the various possibilities when the stabilized foam comprises in addition to an agent solid stabilizer at least one solid foaming agent and / or sorbent. In Table 2 below, we mean: "stabilizer" means a stabilizing solid agent, a foaming stabilizing solid, a solid stabilizing sorbent, a solid stabilizing, foaming and sorbing agent or mixtures thereof;

- "Foaming and / or sorbent", a foaming solid agent, a solid sorbent, a foaming and sorbent solid or mixtures thereof; a type of solid agent (i.e., stabilizer, or foaming agent and / or sorbent) quoted twice on a line of Table 2 may be the same or different.

Table 2

In the various preparation methods described above, the foam can be generated by any Foam generation system of the prior art and known to those skilled in the art. This is any device ensuring the gas-liquid mixture, in particular by mechanical stirring, by bubbling, by static mixer containing balls or not, devices described in patent FR-A-2,817,170, or devices using a spray nozzle or spray, etc.

The present invention also relates to the use of a stabilized foam as defined above or a stabilized foam prepared according to a method as previously defined for decontaminating, etching and / or degreasing a surface. Advantageously, the decontamination of a surface is carried out by dissolving irradiating surface deposits or by corrosion over a few millimeters of the contaminated wall. In addition, this use is applicable to cleaning but will be of particular interest for the decontamination of contaminated metal surfaces either by fatty deposits or radioactive minerals, or by a layer of oxides. The contamination can also be located in a layer of several tens or hundreds of microns in the mass of the material to be treated.

This use is perfectly applicable to the decontamination of large volume nuclear installations and / or complex or inaccessible geometries, and for which the quantities of chemical reagents and ultimate liquid effluents to be treated are important. The present invention also relates to a method for decontaminating, etching and / or degreasing a surface comprising the steps of: a) preparing a stabilized foam according to the previously defined preparation methods, b) applying the stabilized foam obtained to the step (a) on the surface to be treated. Advantageously, in step (b) of the method for decontaminating, stripping and / or degreasing a surface, the stabilized foam is used statically, in pseudostatic (or in rise-rest cycles), in circulation or spray. According to the invention, the method for decontaminating, stripping and / or degreasing a surface may also include an additional step of recovering the foam and / or the liquid constituting the foam after it has been drained. In a first variant, this additional step consists in recovering by suction or suction the foam having not finished draining. The foam is then sent to a device for recovering the solid stabilizing agent of the solid particle type it contains, for example a particulate filter.

In a second variant, this additional step consists in recovering the liquid constituting the foam after its drainage, in order to separate the solid stabilizing agent of the solid particle type from the liquid. This separation can advantageously be carried out by decantation, preceded or not by flocculation, centrifugation, filtration, or any other device making it possible to recover a solid dispersed in a liquid. The solid-solid stabilizing agent thus recovered from the drained liquid may then be: reused in the decontamination, pickling and / or degreasing (recycling) process, or regenerated, in particular by desorption of the captured chemical entities,

- is removed by vitrification, asphalting or incineration.

According to the invention, the effluent without the stabilizing solid agent recovered after the separation step as previously defined has a lower contamination and a lower foamability. Indeed, such advantages are obtained thanks to the foaming and sorbent properties of the solid agents present in the decontamination, pickling and / or degreasing foam according to the invention. The effluent thus recovered can be more easily treated, possibly after a mineralization step, vitrified or asphalted. The various techniques used during the decontamination, pickling and / or degreasing process according to the invention, such as asphalting, vitrification, centrifugation, filtration, etc., are techniques well known to the skilled person. job. Other features and advantages of the present invention will become apparent on reading the examples given below by way of illustration and not limitation and with reference to the appended figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the apparatus used to generate foams according to the invention or the state of the art, and whose drainage is quantified by turbidity measurements over time.

Figure 2 shows the drainage kinetics obtained with the phosphonitic acid foams of the state of the art or according to the invention. More particularly, FIG. 2 shows the evolution over time of the standardized liquid heights at the bottom of the test piece, for foams of the state of the art (phosphonitric acid foams containing 1, 2, or 3 g / l of xanthan gum or 0 g / l of silica particles) and phosphonitic acid foams according to the invention ie containing 10, 15 or 20 g / l of silica particles.

Figure 3 shows the drainage kinetics obtained with the alkaline foams of the state of the art or according to the invention. More particularly, FIG. 2 shows the evolution over time of the standardized liquid heights at the bottom of the test piece, for an alkaline foam of the state of the art containing 1 g / l of xanthan gum and for an alkaline foam according to the invention containing 10 g / 1 of silica particles. EXAMPLE 1 Comparison of the Drainage Kinetics of Viscous Foams and Particulate Foams

I. Phosphonic acid foams.

The drainage properties of phosphonitric foams prepared: from a foaming solution of

GLUCOPON 215 CS (COGNIS company) at 1.5 M H ₃ PO ₄ , 1.5 M HNO 3, and containing a biodegradable organic viscosity agent, xanthan gum; from a foamable solution containing the same concentrations of surfactant and acid, but in which the viscosity modifier is replaced with particles of Aerosil 380 ^® in concentrations of 0, 10, 15, and 20 g / 1. The particles of Aerosil ^® 380 marketed by DEGUSSA (or Stochem) are hydrophilic fumed silica particles having a specific surface area of 380 m ² / g ± 30 m ² / g. These foaming solutions were used to generate controlled expansion foams using a static generator containing glass beads, according to the protocol detailed in FIG.

The solutions prepared are still very foaming since foaming foams of the order of 10 have thus been prepared.

The kinetics of the drainage of these mosses is followed by the turbidimetry of the mosses as a function of time. The principle of this measure is based on the difference in behavior of a foam and a liquid when they are illuminated by a beam of near infrared light: the foam reflects it while the liquid transmits it. Thus the appearance of the liquid at the bottom of the sample tubes containing the foams results in a signal that increases with time.

Figure 2 shows the evolution over time of liquid heights at the bottom of the specimen, for foams containing 1, 2, or 3 g / 1 of xanthan gum, and 0, 10, 15, or 20 g / 1 1 of silica particles.

The addition of approximately 10 g / l of silica makes it possible to obtain a delay in drainage of the order of 8 min, and it is even possible to reach times of the order of 30 minutes for a concentration. of 20 g / 1. By way of comparison, the foam whose base solution contains 1 g / l of xanthan gum has a delay time of about 2 minutes.

The silica particles introduced thus perfectly fulfill their role of stabilizer of the foam.

II. Alkaline foams.

The drainage properties of two alkaline foams composed of 1M NaHCO ₃ sodium hydrogencarbonate were also studied with the same experimental design.

One solution contains Aerosil 380 silica particles at 10 g / l, and the other contains xanthan gum at 1 g / l. The foaming surfactant is, in both cases, GLUCOPON 215 CS (company COGNIS) at a rate of 10 grams of active ingredient per liter.

Figure 3 shows the evolution over time of the liquid heights at the bottom of the test tube, for the alkaline foam containing 1 g / 1 of xanthan gum or 10 g / 1 of silica particles.

As shown in Figure 3, the addition of solid particles to the formulation of the alkaline foam again leads to a clear stabilization thereof. This stabilization is more pronounced than in the case of acidic foams, since 10 g / l of Aerosil correspond to approximately 2 g / l of xanthan gum.

EXAMPLE 2 Comparison of Foam Heights Formed with Different Types of Particles

The foamability of particle suspensions containing no molecular surfactants has been studied.

The particles studied all have a silica core. They are synthesized by the method developed by Kang et al. Some have a functionalized surface saturated with aminopropyltriethoxysilane (APTES), which enhances their hydrophobicity.

Formula 1 'APTE S The studied systems are:

The Aerosil 380 particles are marketed by STOCHEM The primary particle diameter is 7 nm In solution, the silica adopts a fractal aggregate structure of 60 to 600 nm.

The size of the naked or grafted colloidal silica particles is determined by spectroscopic correlation of photons on a Zetasizer Nano-ZS marketed by MALVERN.

The foam is generated in a column similar to that developed by JJ Bikerman. It is a cylindrical column made of glass, with a height of 70 cm and a diameter of 3 cm. It is equipped at its base with a sinter of size 4, for bubbling compressed air to 3 bars in the suspension. For each of the characterization experiments, we introduce 30 ml of the suspension, previously sonicated for 10 minutes. The air flow is imposed at 40 lh ^"1. The height of foam formed above the liquid is measured after 5 minutes of bubbling. The results obtained are as follows

Water containing Aerosil 380 does not abound during the passage of air. On the other hand, a start of expansion is obtained with the bare colloidal particles. This expansion becomes very important when these same particles are grafted.

The functionalization of the surface of colloidal particles thus favors the foamability of the suspension.

Claims

1) Stabilized foam consisting of a foaming aqueous solution containing: from 0.1 to 7 moles of one or more reagents for decontamination, pickling and / or degreasing per liter of solution, and

2) stabilized foam according to claim 1, characterized in that it contains at least one foaming and / or sorbent solid agent.

3) stabilized foam according to any one of claims 1 or 2, characterized in that said solid stabilizing agent is in the form of solid particles of the same nature or mixtures of solid particles of different nature.

4) Stabilized foam according to any one of the preceding claims, characterized in that said stabilizing solid agent is in the form of fully inorganic solid particles, entirely organic, or inorganic-organic hybrid particles or a mixture of at least two of these types of identical or different particles. Stabilized foam according to claim 4, characterized in that the all-mineral particles are phosphotungstic acid, nickel ferrocyanide, oxide, hydroxide, carbonate, sulfate, nitrate, oxalate and / or titanate. one or more species selected from alkali, alkaline earth, transition and metalloid metals.

6) Stabilized foam according to claim

4, characterized in that the fully organic particles are composed of thermoplastic and / or thermosetting polymers and copolymers and / or biopolymers.

7) Stabilized foam according to claim 6, characterized in that the thermoplastic polymers or copolymers are chosen from the following families: polyolefins, polyvinyls, polyvinylidenics, polystyrenic, acrylic / methacrylic, polyamides, polyesters, polyethers, poly (arenesulfones), polysulfides, polyfluoro, poly (aryletherketones), polyimides, polyetherimides, and cellulosic polymers.

8) Stabilized foam according to claim 6, characterized in that the thermosetting polymers or copolymers are chosen from the following families: aminoplasts, polyurethanes, unsaturated polyesters, phenoplasts, polysiloxanes, epoxy resins, allyl and vinylesters, alkyds, polyureas, polyisocyanurates, poly (bismaleimide), and polybenzimidazoles.

9) stabilized foam according to claim 6, characterized in that the biopolymers are microbial biopolymers, biopolymers derived from plants or biopolymers derived from the chemical polymerization of biological entities.

10) stabilized foam according to claim 4, characterized in that the mineral-organic hybrid particles have either an organic core consisting of at least one chemical compound as defined in any one of claims 6 to 9 and a surface of which at at least one part is mineral and consists of at least one chemical compound as defined in claim 5,

or a mineral core consisting of at least one chemical compound as defined in claim 5 and a surface of which at least a part is organic and consisting of at least one chemical compound as defined in any one of claims 6 to 9.

11) Stabilized foam according to any one of claims 3 to 10, characterized in that the surface of the solid particles is either homogeneous hydrophilic or homogeneous hydrophobic or has hydrophilic surface areas and representing from 0.01 to 99.99 % of the total area, the the remainder of the surface (99.99 to 0.01% of the total area) being hydrophobic.

12) Stabilized foam according to any one of claims 3 to 11, characterized in that said solid particles are functionalized by grafting organic molecules.

13) stabilized foam according to any one of the preceding claims, characterized in that said foaming aqueous solution comprises a decontamination agent, pickling and / or degreasing selected from an acid or a mixture of acids, a base or a mixture bases, an oxidizer, a reducing agent, a disinfectant, an antioxidant, an antiseptic and their mixtures.

14) Stabilized foam according to any one of the preceding claims, characterized in that said foaming aqueous solution further comprises a surfactant, a mineral oxidizing agent, a complexing agent and / or an organic gelling agent.

15) Stabilized foam according to claim 14, characterized in that said foaming aqueous solution comprises a single surfactant or a mixture of at least two surfactants chosen from nonionic foaming surfactants, anionic or cationic foaming surfactants, amphoteric surfactants, surfactants with a Bolaform type structure, Gemini type surfactants and polymeric surfactants.

16) Process for preparing a stabilized foam according to any one of the preceding claims, characterized in that the active agent for decontamination, pickling and / or degreasing, the solid stabilizing agent and, optionally, the agent surfactant, the oxidizing agent, the complexing agent, the gelling agent and / or the solid foaming and / or sorbing agent as defined in any one of the preceding claims are mixed together before generation of the foam.

17) A method of preparation according to claim 16, characterized in that the stabilizing solid agent is formed in situ in the mixture.

18) Process for preparing a stabilized foam according to any one of claims 1 to 15, characterized in that the active agent for decontamination, pickling and / or degreasing and, optionally, the surfactant, the stabilizing solid agent, the solid foaming agent and / or sorbent, the oxidizing agent, the complexing agent and / or the gelling agent as defined in any one of claims 1 to 15 are mixed together, all or part of of the solid stabilizing agent and / or all or part of the solid foaming and / or sorbing agent being fed directly into the gas to form a smoke contacted with the foaming liquid and generate the foam.

19) Use of a stabilized foam according to any one of claims 1 to 15 or a stabilized foam prepared by a process according to any one of claims 16 to 18 for decontaminating, etching and / or degreasing a surface.

20) A process for decontaminating, etching and / or degreasing a surface comprising the steps of: a) preparing a stabilized foam by a method according to any one of claims 16 to 18, b) applying the stabilized foam obtained in step (a) on the surface to be treated.

21) Method according to claim 20, characterized in that said method includes an additional step of recovering the foam and / or the liquid constituting the foam after its drainage.

22) A method according to claim 21, characterized in that the foam is recovered by suction or suction before being sent to a device for recovering the solid stabilizer it contains.

23) Method according to claim 21, characterized in that the liquid constituting the foam after its drainage is recovered in order to separate the solid stabilizing agent from the liquid.

24) Method according to claim 23, characterized in that said separation is carried out by decantation preceded or not by flocculation, by centrifugation, by filtration, or by any other device for recovering a solid dispersed in a liquid.

25) Method according to any one of claims 23 or 24, characterized in that the stabilizing solid agent recovered after the separation step as defined in claim 24 is: is reused in the decontamination process, stripping and / or degreasing (recycling), or regenerated, in particular by desorption of the captured chemical entities,

- is removed by vitrification, asphalting or incineration.

26) Method according to any one of claims 23 or 24, characterized in that the effluent recovered after the separation step as defined in claim 24 has a lower contamination and foamability.