Pigmented decontaminating gel and method for decontaminating surfaces using said gel

Abstract

A decontamination gel is provided consisting of a colloidal solution comprising 0.1% to 30% by mass, preferably 0.1% to 25% by mass, still more preferably from 5% to 25% by mass, even more preferably 8% to 20% by mass, based on the mass of the gel, of at least one inorganic viscosifying agent; 0.1 to 10 mol/L of gel, preferably 0.5 to 10 mol/L of gel, still more preferably 1 to 10 mol/L of gel of at least one active decontamination agent; 0.01% to 10% by mass, preferably 0.1% to 5% by mass based on the mass of the gel of at least one mineral pigment; optionally, 0.1% to 2% by mass based on the mass of the gel, of at least one surfactant; optionally, 0.05% to 5% by mass, preferably 0.05% to 2% by mass, based on the mass of the gel, of at least one super-absorbent polymer; and the balance of solvent.

Claims

1. A decontamination gel consisting of a colloidal solution comprising: 0.1% to 30% by mass, based on the mass of the gel, of at least one inorganic viscosifying agent; 0.1 to 10 mol/L of gel, of at least one active decontamination agent; 0.01% to 0.1% by mass, based on the mass of the gel, of an iron oxide pigment; optionally, 0.1% to 2% by mass based on the mass of the gel, of at least one surfactant; optionally, 0.05% to 5% by mass, based on the mass of the gel, of at least one super-absorbent polymer; and the balance of solvent.

2. The decontamination gel according to claim 1, wherein the iron oxide pigment is selected so that it gives the gel a color different from the color of a surface to be decontaminated on which the gel is applied.

3. The decontamination gel according to claim 1, wherein the iron oxide pigment is a micronized pigment and the average size of the particles of the iron oxide pigment is from 0.05 to 5 m.

4. The decontamination gel according to claim 1, wherein the inorganic viscosifying agent is selected from a group consisting of oxides of metals, oxides of metalloids, hydroxides of metals, hydroxides of metalloids, oxyhydroxides of metals, oxyhydroxides of metalloids, aluminosilicates, clays, and mixtures thereof.

5. The decontamination gel according to claim 4, wherein the inorganic viscosifying agent is selected from a group consisting of pyrogenated silicas, precipitated silicas, hydrophilic silicas, hydrophobic silicas, acid silicas, basic silicas, and mixtures thereof.

6. The decontamination gel according to claim 5, wherein the inorganic viscosifying agent consists of a mixture of precipitated silica and of a pyrogenated silica.

7. The decontamination gel according to claim 4, wherein the inorganic viscosifying agent consists of one or several aluminas representing from 5% to 30% by mass, based on the mass of the gel.

8. The decontamination gel according to claim 1, wherein the active decontamination agent is selected from a group consisting of bases, acids, oxidizers, quaternary ammonium salts, reducing agents, and mixtures thereof.

9. The decontamination gel according to claim 1, wherein the super-absorbent polymer is selected from a group consisting of sodium poly(meth) acrylates, starches grafted with a (meth)acrylic polymer, hydrolysed starches grafted with a (meth)acrylic polymer; polymers based on starch, on a gum, and on a cellulose derivative; and mixtures thereof.

10. The decontamination gel according to claim 1, wherein the surfactant is selected from non-ionic surfactants and mixtures thereof.

11. The decontamination gel according to claim 1, wherein the solvent is selected from a group consisting of water, organic solvents and mixtures thereof.

12. A method for decontaminating at least one surface of a substrate made of a solid material, said surface being contaminated with at least one contaminating species found on said surface and optionally under said surface in the depth of the substrate, wherein at least one cycle is carried out, comprising the following successive steps: a) applying the gel according to claim 1 on said surface; b) maintaining the gel on the surface for at least a sufficient duration so that the gel destroys and/or inactivates and/or absorbs the contaminating species, and so that the gel dries and forms a dry and solid residue containing said contaminating species; c) removing the dry and solid residue containing said contaminating species.

13. The method according to claim 12, wherein the iron oxide pigment contained in the gel is selected so that it gives the gel a color different from the color of the surface to be decontaminated on which the gel is applied.

14. The method according to claim 12, wherein the substrate is a porous substrate, optionally, a porous mineral substrate.

15. The method according to claim 12, wherein the solid material is selected from a group consisting of metals and metal alloys; polymers; glasses; cements and cement materials; mortars and concretes; plasters; bricks; natural or artificial stone; and ceramics.

16. The method according to claim 12, wherein the contaminating species is selected from chemical, biological, nuclear or radioactive contaminating species.

17. The method according to claim 16, wherein the contaminating species is a biological species.

18. The method according to claim 12, wherein the gel is applied on the surface in an amount from 100 g to 2,000 g of gel per m.sup.2 of surface.

19. The method according to claim 12, wherein during step b), drying is carried out at a temperature of 1 C. to 50 C., and under relative humidity from 20% to 80%.

20. The method according to claim 12, wherein the gel is maintained on the surface for a duration from 2 to 72 hours.

21. The method according to claim 12, wherein the gel is maintained on the surface until it exhibits a reduction of its visible and ultraviolet absorbance.

22. The method according to claim 12, wherein the dry and solid residue appears as particles with a size from 1 to 10 mm.

23. The method according to claim 12, wherein the dry and solid residue is removed from the solid surface by brushing and/or suction.

24. The method according to claim 12, wherein the described cycle is repeated from 1 to 10 times by using the same gel during all the cycles or by using different gels during one or several cycle(s).

25. The method according to claim 12, wherein during step b), the gel, before total drying, is re-wetted with a solution of the active decontamination agent of the gel of step a) in the solvent of this gel.

26. The decontamination gel according to claim 1, wherein upon being sprayed and thereafter maintained on a surface for 3 to 24 hours such that the decontamination gel dries, the dried decontamination gel exhibits a relative decrease in visible and ultraviolet light absorbance from 30 to 99% compared to the decontamination gel as sprayed.

27. The decontamination gel according to claim 8, wherein the active decontamination agent is a base selected from the group consisting of sodium hydroxide, potassium hydroxide, and mixtures thereof.

28. The decontamination gel according to claim 8, wherein the active decontamination agent is an acid selected from the group consisting of nitric acid, phosphoric acid, hydrochloric acid, sulfuric acid, hydrogenoxalates, and mixtures thereof.

29. The decontamination gel according to claim 8, wherein the active decontamination agent is an oxidizer selected from the group consisting of peroxides, permanganates, persulfates, ozone, hypochlorites, salts of cerium IV, and mixtures thereof.

30. The decontamination gel according to claim 8, wherein the active decontamination agent is a quaternary ammonium salt selected from the group consisting of hexadecylpyridinium salts.

31. The decontamination gel according to claim 10, wherein the non-ionic surfactants are selected from the group consisting of block, sequenced copolymers and ethoxylated fatty acids.

32. The decontamination gel according to claim 31, wherein the block, sequenced copolymers are copolymers of ethylene oxide and propylene oxide.

33. The method according to claim 15, wherein the solid material is a metal or metal alloy selected from the group consisting of stainless steel, painted steels, aluminum and lead.

34. The method according to claim 15, wherein the solid material is a polymer selected from the group consisting of plastic materials and rubbers.

35. The method according to claim 17, wherein the biological species is selected from the group consisting of bacteria, fungi, yeasts, viruses, toxins, spores and protozoa.

36. The method of claim 17, wherein the biological species is a biotoxic species.

37. The method of claim 36, wherein the biological species is a pathogenic spore.

38. The method of claim 37, wherein the pathogenic spore is Bacillus anthracis.

39. The method of claim 36, wherein the biological species is a toxin.

40. The method of claim 39, wherein the toxin is selected from the group consisting of botulinic toxin and ricin.

41. The method of claim 36, wherein the biological species is a bacteria.

42. The method of claim 41, wherein the bacteria is Yersinia pestis bacteria.

43. The method of claim 36, wherein the biological species is a virus.

44. The method of claim 43, wherein the virus is selected from the group consisting of virus of vaccine or virus of haemorrhagic fevers.

45. The method of claim 44, wherein the virus of haemorrhagic fever is of the Ebola- type.

Description

SHORT DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 (A, B) shows schematic sectional views illustrating the main steps of the method according to the invention for decontaminating a solid material.

(2) FIG. 2 (A, B, C) shows schematic sectional views showing the mode of action of a gel without any super-absorbent polymer on a cement material contaminated in depth by a contamination in liquid form.

(3) FIG. 3 (A, B, C) shows schematic sectional views showing the mode of action of a gel containing a super-absorbent polymer on a cement material contaminated in depth by a contamination in liquid form.

(4) FIG. 4 is a photograph which shows the spraying of a conventional non-pigmented white decontamination gel on a support to be decontaminated consisting of white ceramic tiles. This photograph shows that it is difficult to distinguish the areas covered by the gel, whether they are dry or wet, from the areas which are not covered by the gel.

(5) FIG. 5 is a photograph which shows a wall of ceramic tiles of the Paris Metro covered with a white non-pigmented gel.

(6) FIG. 6 is a photograph which shows a ceramic tile covered with pigmented gel according to the invention, dry and fractured.

(7) FIG. 7 is a graph which illustrates the UV and visible absorbance curves of the alkaline pigmented gel GB62 according to the invention, wet (curve A), of the pigmented gel GB62 according to the invention, dry (curve B), and of the wet white gel without any pigment GB61, wet (curve C).

(8) The wavelength (in nm) is plotted in abscissas, and the absorbance is plotted in ordinates.

(9) FIG. 8 is a graph which illustrates the UV and visible absorbance curves of the alkaline pigmented gel GB63 according to the invention, wet (curve A), of the pigmented gel GB63 according to the invention, dry (curve B), and of the wet white gel GB61 without any pigment, wet (curve C).

(10) The wavelength (in nm) is plotted in abscissas, and the absorbance is plotted in ordinates.

(11) FIG. 9 is a graph which illustrates the UV and visible absorbance curves of the acid pigmented gel GB75 according to the invention, wet (curve A), of the pigmented gel GB75 according to the invention, dry (curve B), and of the wet white gel GB61 without any pigment, wet (curve C).

(12) The wavelength (in nm) is plotted in abscissas, and the absorbance is plotted in ordinates.

(13) FIG. 10 is a graph which illustrates in a logarithmic scale, the viscosity (in Pa.Math.s) of the GB61 (curve 1), GB62 (curve 2) and GB63 (curve 3) gels versus the shear rate (in s.sup.1).

(14) FIG. 11 is a graph which illustrates the threshold stress of the GB61 gel.

(15) The curves 1, 2, 3, and 4 respectively represent the stress measured for pre-shearing at 100 s.sup.1 for 100 s, and then a rest period of 10 s (curve 1), a rest period of 100 s (curve 2), a rest period of 500 s (curve 3), and a rest period of 1,000 s (curve 4).

(16) The deformation is plotted in abscissas and the stress (in Pa) is plotted in ordinates.

(17) FIG. 12 is a graph which illustrates the threshold stress of the GB62 gel.

(18) The curves 1, 2, 3, and 4 respectively illustrate the measured stress for pre-shearing at 100 s.sup.1 for 100 s, and then a rest period of 10 s (curve 1), a rest period of 100 s (curve 2), a rest period of 500 s (curve 3), and a rest period of 1,000 s (curve 4).

(19) The deformation is plotted in abscissas and the stress (in Pa) is plotted in ordinates.

(20) FIG. 13 is a graph which illustrates the drying kinetics of the GB61 (curve A), GB62 (curve B), and GB63 (curve C) gels.

(21) The drying time (in mins) is plotted in abscissas and the mass loss (in %) is plotted in ordinates.

(22) FIG. 14 is a graph which shows the fracturation of the GB61, GB62, and GB63 gels.

(23) For each gel GB61, GB62, and GB63, the average area of the flakes (left bar), the number of flakes (middle bar), and the median area of the flakes (right bar) are given.

(24) On the left scale, the number of flakes is plotted, and on the right scale the area of the flakes (in mm.sup.2) is plotted.

(25) FIG. 15 is a graph which illustrates the UV and visible absorbance of the pigmented alkaline gel GB62 according to the invention, wet, fresh which has just been prepared (curve 2), of the pigmented alkaline gel GB62 according to the invention, wet, after storage for 4 months after its preparation (curve 1) and of the wet non-pigmented alkaline gel GB61 (curve 3).

(26) The wavelength (in nm) is plotted in abscissas, and the absorbance is plotted in ordinates.

(27) FIG. 16 shows photographs of Petri dishes in which were produced cultures from the decontamination of supports made of stainless steel contaminated by Bacillus thuringiensis with the pigmented gel GB62 according to the invention (16A) and by a non-pigmented white gel (16B).

(28) In each of FIGS. 16A and 16B, the left Petri dish is a Petri dish containing a culture from the decontaminated support cleared of the flakes, while the right Petri dish is a Petri dish containing a culture from dry gel flakes recovered on the support.

DETAILED DISCUSSION OF PARTICULAR EMBODIMENTS

(29) The gel according to the invention may easily be prepared at room temperature.

(30) For example, the gel according to the invention may be prepared by preferably gradually adding the inorganic viscosifying agent(s), for example the alumina(s) and/or the silica(s), to a mixture of the active decontamination agent, of the optional surfactant(s), and of mineral pigment(s) such as iron oxides.

(31) This mixture may be produced by mechanical stirring, for example by means of a mechanical stirrer equipped with a three-blade propeller. The speed of rotation is for example 200 revolutions/minute, and the duration of the stirring is for example from 3 to 5 minutes.

(32) The addition of inorganic viscosifying agent(s) to the mixture containing the active biological decontamination agent, the optional surfactant(s), and the pigment(s) may be carried out by simply pouring the viscosifying agent(s) into the mixture. During the addition of the inorganic viscosifying agent(s), the mixture containing the active biological decontamination agent, the optional surfactant(s) and the pigment(s) is generally maintained with mechanical stirring.

(33) This stirring may for example be produced by means of a mechanical stirrer equipped with a three-blade propeller.

(34) The stirring speed is generally gradually increased as the viscosity of the solution increases, in order to finally attain a stirring rate comprised for example between 400 and 600 rpm, without there having been projections.

(35) After the end of the addition of the mineral viscosifying agent(s), stirring is further maintained, for example for 2 to 5 minutes, so as to obtain a perfectly homogenous gel.

(36) It is quite obvious that other procedures for preparing gels according to the invention may be applied with addition of the components of the gel in a different order from that mentioned above.

(37) Generally, the gel according to the invention should have a viscosity of less than 200 mPa.Math.s under shearing of 1,000 s.sup.1 so as to allow spraying onto the surface to be decontaminated, at a distance (for example at a distance from 1 to 5 m) or near (for example at a distance of less than 1 m, preferably from 50 to 80 cm). The viscosity resumption time should generally be less than one second and the viscosity under low shearing should be greater than 10 Pa.Math.s so as to not run over a wall.

(38) It should be noted that the surfactant of the gel according to the invention favorably influences notably the flow properties of the gel according to the invention. This surfactant notably gives the possibility of being able to apply the gel according to the invention by spraying and avoiding spreading or run-off risks upon treating vertical surfaces and ceilings.

(39) The thereby prepared gel according to the invention is then applied (1) (FIG. 1A) on the solid surface (2) to be decontaminated of a substrate in a solid material (3), in other words on the surface (2) having been exposed to contamination for example to biological contamination (4). This contamination has already been described above. In particular, the biological contamination (4) may consist of one or several of the biological species already defined above.

(40) As already indicated above, the active decontamination agent, for example the active biological decontamination agent, is selected according to the contaminating species, for example to the biological species to be removed (eliminated), destroyed, or inactivated.

(41) Optionally except for light weight metal alloys of the aluminium type, in the case when basic or acid gels are applied, no limitation exists as to the material which constitutes the surface (2) to be decontaminated, indeed, the gel according to the invention gives the possibility of treating without any damage all kinds of material even brittle materials.

(42) The gel according to the invention does not generate any alteration, erosion, chemical, mechanical or physical attack of the treated material. The gel according to the invention is therefore by no means detrimental to the integrity of the treated materials and even allows their reuse. Thus, sensitive equipment such as military equipment are preserved and may after their decontamination be reused, while monuments treated with the gel according to the invention are absolutely not degraded and their visual and structural integrity is preserved.

(43) This material of the substrate (3) may therefore be selected from for example metals and alloys such as stainless steel, aluminium, and lead; polymers such as plastic materials or rubbers from among which mention may be made of PVC, PP, PE notably HDPE, PMMA, PVDF, PC; glasses; cements and cement materials; mortars and concretes; plasters; bricks; natural or artificial stone; ceramics.

(44) In every case, regardless of the material, the decontamination efficiency with the gel according to the invention is total.

(45) The treated surface may be painted or not painted.

(46) In a particularly surprising way, it was found that the gel according to the invention, when it contained a super-absorbent polymer, was particularly efficient on porous materials such as cement matrices like slurries, mortars and concretes, bricks, plasters or further natural or artificial stone.

(47) Indeed, the presence in the gel according to the invention of a super-absorbent polymer allows decontamination of a porous material over a much larger depth than with an equivalent gel without any super-absorbent polymer.

(48) In other words, the presence of a super-absorbent polymer in the gel according to the invention facilitates the diffusion of the active decontamination agent, for example of the biocidal agent in the depth of the material when the question is to treat porous, notably mineral substrates.

(49) The efficiency of the treatment with the gel according to the invention is generally total, including on materials contaminated over several millimetres of depth; in the latter case, a super-absorbent polymer is then preferably included in the gel.

(50) Also there is no limitation as to the shape, the geometry and the size of the surface to be decontaminated, the gel according to the invention and the method applying it gives the possibility of treating surfaces of large size, with complex geometries, for example having cavities, recesses, angles, corners.

(51) The gel according to the invention ensures efficient treatment not only of horizontal surfaces such as floors, but also of vertical surfaces such as walls, or of tilted or overhanging surfaces such as ceilings.

(52) As compared with decontamination methods, for example existing biological decontamination methods which apply liquids such as solutions, the decontamination method according to the invention which applies a gel is particularly advantageous for treating materials with a large surface, which are not transportable and implanted outdoors. Indeed, the method according to the invention because of the application of the gel, allows decontamination in situ by avoiding the spreading of chemical solutions in the environment and dispersion of the contaminating species.

(53) The gel according to the invention may be applied on the surface to be treated with any application methods known to the man skilled in the art.

(54) Standard methods are spraying for example with a gun or application by means of a brush, a trowel.

(55) For applying the gel according to the invention by spraying on the surface to be treated, the colloidal solution may for example be conveyed via a low pressure pump, for example a pump which applies a pressure of less than or equal to 7 bars, i.e. about 7.Math.10.sup.5 Pascals.

(56) The bursting of the gel jet on the surface may for example be obtained by means of a nozzle with a flat jet or with a round jet.

(57) The distance between the pump and the nozzle may be any distance, for example it may be from 1 to 50 m, notably from 1 to 25 m.

(58) The sufficiently short viscosity recovery time of the gels according to the invention allow the sprayed gels to adhere to any surfaces, for example walls.

(59) The amount of gel deposited on the surface to be treated is generally from 100 to 2,000 g/m.sup.2, preferably from 500 to 1,500 g/m.sup.2, still preferably from 600 to 1,000 g/m.sup.2.

(60) The deposited gel amount per unit surface and consequently the thickness of the deposited gel has an influence on the drying rate.

(61) Thus, when a gel film, layer with a thickness of 0.5 mm to 2 mm is sprayed on the surface to be treated, the effective contact time between the gel and the materials is then equivalent to its drying time, a period during which the active ingredient contained in the gel will interact with the contamination.

(62) In the case of porous substrates, for example cement matrices, the action time of the decontamination solution, for example of the biocidal solutionwhich in this case preferably contains a super-absorbent polymer having penetrated the core of the materialfollowing the action of the super-absorbent polymer may be greater than the drying time of the gel, in which case it is generally necessary either to produce re-wetting with the contamination solution, for example with the biocidal solution, or repeat spraying of the gel.

(63) Further, it was shown surprisingly that the deposited amount of gel when it is located in the ranges mentioned above and in particular when it is greater than 500 g/m.sup.2 and notably in the range from 500 to 1,500 g/m.sup.2, which corresponds to a minimum thickness of deposited gel for example greater than 500 m for a deposited amount of gel of more than 500 g/m.sup.2, after drying the gel gave the possibility of obtaining fracturation of the gel in the form of millimetric flakes, for example with a size from 1 to 10 mm, preferably from 2 to 5 mm, and vacuumable.

(64) The deposited amount of gel and therefore the thickness of deposited gel preferably greater than 500 g/m.sup.2 i.e. 500 m, is the fundamental parameter which influences the size of the dry residues formed after drying the gel and which thus ensures the formation of dry residues with millimetric size and not powdery residues, such residues being easily removed by a mechanical method and preferably by suction.

(65) However, it should also be noted that by means of the surfactant agent at a low concentration, generally from 0.1% to 2% of the total mass of the gel, the drying of the gel is improved and leads to a homogenous fracturation phenomenon with a size of mono-dispersed dry residues and increased capability of the dry residues to be detached from the support.

(66) The gel is then maintained on the surface to be treated during the whole period required for its drying. During this drying step, which may be considered as the active phase of the method according to the invention, the solvent contained in the gel, i.e. generally the water contained in the gel evaporates until a dry and solid residue is obtained.

(67) The drying duration depends on the composition of the gel in the concentration ranges of its constituents given above, but also, as already specified, on the deposited amount of gel per unit of area, i.e. the thickness of deposited gel.

(68) The drying duration also depends on weather conditions, i.e. the temperature and the relative wetity of the atmosphere in which the solid surface is found.

(69) The method according to the invention may be applied under extremely wide weather conditions, i.e. at a temperature T from 1 C. to 50 C. and at a relative wetity RH from 20% to 80%.

(70) The drying duration of the gel according to the invention is therefore generally from 1 hour to 24 hours at a temperature T from 1 C. to 50 C. and at a relative wetity RH from 20% to 80%.

(71) It should be noted that the formulation of the gel according to the invention essentially because of the presence of surfactants such as Pluronics generally ensures a drying period which is substantially equivalent to the contact time (between the decontamination agent, such as a biocidal agent, and the contaminating species, for example the notably biotoxic biological species to be removed) which is necessary, required for inactivating and/or absorbing the contaminating species polluting the material, and/or for carrying out sufficiently the reactions for erosion of the surface of the material.

(72) In other words, the formulation of the gel ensures a drying period time which is nothing else than the inactivation period time of the contaminating species, for example of the biological species, which is compatible with the contamination inhibition kinetics, for example of the biological contamination.

(73) Or else the formulation of the gel ensures a drying period time which is nothing else than the period time required for the erosion reactions to remove a contaminated surface layer of the material.

(74) In the case of radioactive contaminating species, the contamination is removed by dissolving irradiating deposits or by corrosion of the materials supporting the contamination. Therefore there is really a transfer of the nuclear contamination to the flakes of dry gels.

(75) The specific surface area of the mineral filler generally used which is generally from 50 m.sup.2/g to 300 m.sup.2/g, preferably 100 m.sup.2/g and the absorption capacity of the gel according to the invention give the possibility of trapping the labile contamination (surface contamination) and attached to the material constituting the surface to be treated.

(76) If required, the contaminating species, for example the contaminating biological species are inactivated in the gel phase. After drying the gel, the contamination, for example the inactivated biological contamination, is removed (eliminated) upon recovering the dry gel residue described below.

(77) At the end of the drying of the gel, the gel homogeneously fractures and gives millimetric solid dry residues, for example with the size from 1 to 10 mm, preferably from 2 to 5 mm, which are not powdery, and generally are as solid flakes (5) (FIG. 1B).

(78) The dry residues may contain the inactivated contaminating species (6).

(79) The dry residues, such as flakes (5), obtained at the end of the drying have low adherence to the surface (2) of the decontaminated material. Consequently, the dry residues obtained after drying the gel may easily be recovered by simple brushing and/or suction.

(80) However, the dry residues may also be discharged by a gas jet, for example by a compressed air jet.

(81) Thus, no rinsing with a liquid is generally necessary, and the method according to the invention does not generate any secondary effluent.

(82) However, it is possible, although this is not preferred, and if this is desired, to remove the drying residues by means of a liquid jet.

(83) The method according to the invention thus therefore achieves first of all significant savings in chemical reagents as compared with a decontamination method by washing with a solution. Subsequently, because a waste as a dry residue which is directly vacuumable is obtained, a rinsing operation with water or with a liquid generally required for removing trace amounts of chemical agents from the part is generally avoided. The result of this is quite obviously a reduction in the amount of produced effluents but also a notable simplification in terms of waste treatment system and outlet.

(84) Because of the in majority mineral composition of the gel according to the invention and of the small amount of produced wastes, the dry waste may be stored or directed to a discharge system (outlet) without any prior treatment.

(85) The dry gel flakes obtained at the end of the method according to the invention have been approved at ANDRA as a heterogeneous waste which may be immobilized in an HTC mortar grout.

(86) At the end of the method according to the invention, a solid waste is recovered as flakes which may be conditioned as such, directly conditioned, the result of this, as already indicated above is a significant reduction in the amount of produced effluents as well as notable simplification in terms of waste treatment system and outlet.

(87) Further, in the nuclear field, the fact of not having to reprocess the flakes after conditioning the waste is a considerable advantage; this authorizes the use of active performing agents which were banned up to now, in decontamination liquids because of the constraints on operating stations for processing liquid effluents (LETS).

(88) The gel may therefore contain powerful oxidizers such as cerium IV which may very easily be regenerated from electrolysis of cerium III.

(89) As an example, in the current case where 1,000 grams of gel per m.sup.2 of treated surface are applied, the produced dry waste mass is less than 200 grams per m.sup.2.

(90) In FIG. 2, the decontamination with a gel not containing any super-absorbent polymer of a porous substrate (21) for example contaminated with spores in an aqueous solution (22) is illustrated. The contamination front (23) extends into the depth of the substrate (FIG. 2A). When a decontamination gel, for example a biocidal gel (24) is applied on the surface (25) of the substrate, the diffusion front (26) of the decontamination agent, for example the biocidal agent, does not extend much into the depth of the substrate and remains below the contamination front (23) (FIG. 2B). Consequently, when the gel is removed (FIG. 2C), the cleaned-up area (27) does not extend much in depth and a residual contamination (28) remains in the porous substrate (21).

(91) In FIG. 3, the decontamination with the gel according to the invention containing a super-absorbent polymer, of a contaminated porous substrate (31), for example with spores in an aqueous solution (32) is illustrated. The contamination front (33) extends into the depth of the substrate (FIG. 3A). When a decontamination gel, for example a biocidal gel containing the super-absorbent (34) is applied on the surface (35) of the substrate, the diffusion front (36) of the decontamination agent, for example of the biocidal agent extends into the depth of the substrate and goes beyond the contamination front (33) (FIG. 3B). Consequently, the cleaned-up area (37) extends in depth (P) and there no longer remains any residual contamination in the porous substrate.

(92) The invention will now be described with reference to the following examples given as an illustration and not as a limitation.

EXAMPLES

Example 1

(93) In this example, the discoloration of basic gels is studied during their drying.

(94) The gels analyzed in this example are basic mineral gels consisting of 14% of Aeroxide Alu C alumina marketed by EVONIK INDUSTRIES and having a specific surface area of 100 m.sup.2/g (BET), of 0.2% of surfactants (Pluronic PE6200 from BASF, and Empilan KR8 from HUNTSMAN), and the balance 1M soda.

(95) According to these gels (Table 1), the formulation may also contain a pigment, i.e. 0.1% by mass of micronized red iron oxides Ferroxide from Rockwood Pigments Ltd of formula Fe.sub.2O.sub.3 with an average particle size of 0.1 m or 0.5 m.

(96) The surfactants, the optional iron oxides, and the soda are first of all mixed by means of a mechanical stirrer provided with a three-blade stirrer at a rate of 200 rpm for 3 to 5 minutes.

(97) The alumina is then gradually added into the reaction mixture by gradually increasing the stirring as the viscosity increases so as to reach about 400 to 500 rpm without there being any projections. The gel is then maintained with stirring for 5 minutes.

(98) The thereby manufactured gels are then analyzed in the wet condition and in the dry condition by means of a UV-3600 Shimadzu spectrometer in order to measure their UV-Visible light absorbance by reflection. The measurements are conducted in the wavelength range from 240 to 800 nm. The base line is produced on a barium sulfate tablet.

(99) Three gels designated as GB61, GB62, and GB63 were prepared, the coloration of these gels is indicated in Table 1 below.

(100) TABLE-US-00001 TABLE 1 Coloration of the tested gels. GEL PIGMENT COLOR GB61 0% White gel GB62 0.1% Ferroxide Rockwood 212M Red gel (average particle size: 0.1 m) GB63 0.1% Ferroxide Rockwood 228M Violet/mauve gel (average particle size: 0.5 m)

(101) The absorbance of the GB61 white gel without any pigment is measured only in the wet condition.

(102) On the other hand, for the two colored gels GB62 and GB63 according to the invention, the absorbance of the wet gels but also that of the flakes obtained at the end of their drying is measured.

(103) In order to achieve analyses on wet gels, they are deposited on the support of the spectrometer placed vertically for the period of analysis. The gels adhere to the walls of the analysis chamber.

(104) In order to achieve the analyses on dry flakes, the latter are milled with a mortar in order to obtain a powder. The powder is then deposited on a barium sulfate tablet, and then compacted before being placed vertically in the analysis chamber.

(105) The results of the analyses are shown in FIGS. 7 and 8.

(106) First of all, it obviously appears that the pigmented, colored gels GB62 and GB63, according to the invention, have higher absorbances than the white gel GB61 without any pigment.

(107) In spite of a low concentration of pigments (0.1%), it is easy to appreciate the strong coloration of these gels according to the invention, related to the strong coloring power of red iron oxide pigments.

(108) Depending on the surface to be decontaminated which has to be covered with the gel, this strong coloration of the gels according to the invention is a particularly advantageous property for operators in NRBC overalls. Indeed, it for example gives the possibility of avoiding the shade-over-shade effect in the areas with reduced visibility and it thus facilitates visual detection of the areas either covered or not by the gel.

(109) Moreover, comparison of the absorbance of the wet gels and of the dry flakes obtained after drying these gels, gives the possibility of demonstrating that the desired goal in terms of decontamination has actually been reached.

(110) Indeed, the absorbance of the dry gel flakes is not as strong as that of wet gels, the absorbance curves however having completely similar aspects.

(111) This lower absorbance of the flakes expresses a discoloration of the gel during drying, and confirms the results of the visual observations.

(112) This discoloration, related to the addition of pigments in the gels according to the invention, is one of the main advantageous effects obtained with the gels according to the invention, since it gives the possibility of easily and rapidly identifying the wet areas and the dry areas on the surfaces covered with the decontamination gels according to the invention.

(113) It should be noted that the aspect of the absorbance curves depends on the pigment present in the gel.

(114) Indeed, the absorbance curves obtained with the gel containing the wet or dry red Ferroxide 212M pigment as flakes have the same aspect, and this aspect is different from that of the absorbance curves obtained with the gel containing the wet or dry violet Ferroxide 228M pigment as flakes.

Example 2

(115) In this example, the discoloration of an acid gel according to the invention is studied during its drying.

(116) A colored acid gel is formulated, containing red iron oxide pigments in order to show that discoloration during drying also occurs when the gel is an acid gel.

(117) This gel, called gel GB75, consists of 14% of silica Tixosil 331 marketed by RHODIA which has a specific surface area of 200 m.sup.2/g (BET), 0.2% of surfactants (Pluronic PE6200 from BASF, and Empilan KR8 from HUNTSMAN), 0.1% of micronized red iron oxides Ferroxide 212M from ROCKWOOD PIGMENTS LTD of formula Fe.sub.2O.sub.3, and the balance 1N nitric acid.

(118) The gel is manufactured according to the same method as in Example 1.

(119) The wet and dry GB75 gels are analyzed with a spectrometer UV-3600 Shimadzu according to the same method as in Example 1.

(120) The results of these analyses are shown in FIG. 9.

(121) It appears, like in Example 1, that the acid gel GB75 is more colored than the white basic gel GB61 without any pigment.

(122) Further, the GB75 acid gel flakes have lower absorbance than that of the same wet gel, which again shows the discoloration of the gel subsequent to drying.

(123) This example shows that the gels according to the invention may both be basic gels and acid gels which in both cases have the same advantageous properties.

Example 3

(124) In this example, the rheology of the pigmented gels according to the invention is studied.

(125) More specifically, in this example the flow properties of both colored basic gels GB62 (red) and GB63 (violet) according to the invention described in Example 1 are compared, as well as the flow properties of the GB61 white basic gel without any pigments described in Example 1, in order to observe the impact of the addition of pigments at 0.1% by mass on the viscosity of the gel.

(126) Indeed, it is indispensable that the rheological properties of the gel, which is a so called sprayable gel should be retained so that said gel may be sprayed and always adheres to the support.

(127) Thus, it should be checked that the addition of micronized particlesin this case pigmentsdoes not modify at all the viscosity of the colloidal gel which itself consists of alumina aggregates of a micrometric size.

(128) For this, two viscosimetric and rheological measurements are conducted.

(129) The first measurement which may be described as a viscosimetric measurement, consists of measuring the viscosity versus the shearing rate by means of a viscosimeter Rheomat RM100 from LAMY RHEOLOGY.

(130) The viscosimeter is equipped with a measurement system of the MS-R3 anchor type. After 10 second pre-shearing at a shearing rate of 1 s.sup.1, 15 plateaus of a shear rate ranging from 1 s.sup.1 to 100 s.sup.1 are carried out with a measurement of the viscosity every 20 seconds.

(131) The second measurement, which may be described as a rheological measurement, consists of measuring the threshold stress of the GB61 and GB62 gels by means of a rheometer TA Instruments AR-1000 in a Vane geometry.

(132) A low shearing rate, i.e. 6.710.sup.3 s.sup.1, is applied to the gels in a constant way in order to deform them from rest, and thus determine their flow threshold.

(133) The results of the viscosimetric measurements on the GB61, GB62, and GB63 gels are illustrated in a logarithmic scale in FIG. 10.

(134) FIGS. 11 and 12 as for them illustrate the results of rheological measurements.

(135) In FIG. 10 it appears that the three curves are very close and parallel.

(136) In this range of shearing rates, it is therefore impossible to perceive a difference from a rheological point of view, between the white gel without any pigment and the gels according to the invention containing 0.1% by mass of red iron oxide pigments.

(137) Thus, the addition of a small amount of micronized pigments does not fundamentally change the rheology of the colloidal mineral gels.

(138) FIG. 11 and FIG. 12 illustrate the shear stress, versus deformation for the gels GB61 (FIG. 11) and GB62 (FIG. 12) respectively.

(139) In both cases, two regimes may be observed.

(140) First of all, the stress increases linearly, the material is under a solid regime (elastic deformation).

(141) A jump is then observed, the shear attains the flow threshold and the material switches to the liquid regime (stationary flow).

(142) The threshold shear corresponds to the shear at the flow threshold, i.e. a maximum of 43 Pa for the GB61 gel, and a maximum of 40 Pa for the GB62 gel.

(143) It should be noted that the measurements were conducted four times for each gel, i.e. for pre-shearing at 100 s.sup.1 for 100 s, followed by a rest period of 10 s (curve 1), 200 s (curve 2), 500 s (curve 3), and 1,000 s (curve 4). The reproducibility of the measurements is good.

(144) Thus, it appears that the addition of pigment to the formulation has little influence on the threshold stress, and that the gel always meets the requirements sheet of vacuumable gels, i.e. a threshold stress of more than 15-20 Pa so that the gel does not flow under the effect of gravity on a vertical wall for applied gel thicknesses of 0.5-2 mm.

Example 4

(145) In this example, the drying kinetics of the pigmented gels according to the invention are studied.

(146) Indeed, another fundamental characteristic of the decontamination gels is their drying time which is very closely related to the weather conditions of the drying environment, i.e. temperature, relative wetity, ventilation/aeration.

(147) In this example, three basic gels GB61 (white, without any pigment), GB62 (red, pigmented according to the invention) and GB63 (violet, pigmented according to the invention), are dried one after the other in a weathering chamber Binder adjusted to 25 C. and to 50% of relative wetity.

(148) The gels are spread out on machined stainless steel boats, nacelles so as to obtain a controlled thickness of 0.5 mm of gel in the boat, nacelle.

(149) In the weathering chamber, precision scales Sartorius are installed, as well as a Moticam camera surrounded by a circular LED lamp (VWR) which is placed above the scales. The scales and the Moticam camera are connected to a computer placed outside the weathering chamber thereby allowing simultaneous acquisition, during drying in a controlled atmosphere, of the mass and of the images of the boat, nacelle filled with gel.

(150) It should be noted that the nacelle, boat, containing the gel is placed in the precision scales, and that all the doors of the scales are closed, except for the door opposite to the fan which is opened by 3 cm in order to maintain the controlled atmosphere in the chamber of the scales while limiting the air flow related to the operation of the weathering chamber.

(151) The results, shown in FIG. 13, show a mass loss completely identical between the white GB61 gel without any pigment and the Ferroxide 228M gel GB63 according to the invention.

(152) Indeed, within 200 minutes, i.e. 3 h 20 min, the gel is completely dry and has lost at least a little less than 80%, i.e. 78% of its initial mass.

(153) As regards the gel GB62 with Ferroxide 212M according to the invention, the gel dries slightly more rapidly but the 78% mass loss plateau is attained within less than 200 minutes. This difference between the times required for attaining this plateau of mass loss of 78%, may be related to a slight variation in the opening of the door of the scale for example.

(154) This example therefore shows that the addition of a small concentration of pigment to gels does not fundamentally change the drying kinetics of these gels both as regards the total drying time and the general aspect of the curves illustrating the drying kinetics of the gels.

Example 5

(155) In this example, the fracturation of the pigmented gels according to the invention is studied.

(156) Indeed, in addition to their rheology (so that they are sprayable and adherent) and their drying time, a third important feature of the decontamination gels, so called vacuumable gels, is their fracturation in the dry condition, in the form of non-powdery millimetric solid flakes.

(157) Therefore in this example the question is of making sure that the addition of pigments in a gel does not modify in any way its fracturation.

(158) This experiment is conducted in parallel with measurements conducted in Example 4 in a weathering chamber under a controlled atmosphere.

(159) Indeed, during drying, according to the procedure and with the device detailed in Example 4, the images (FIG. 14) and the mass of the gel (FIG. 13) are simultaneously recorded during the drying of the gel in the nacelle. The Moticam camera regularly shoots images over time.

(160) The photograph of the totally dry gel is then analyzed by means of an image processing piece of software which detects flakes and counts them while calculating their area.

(161) The results are illustrated in FIG. 14.

(162) Of course, the number of flakes is slightly greater for both gels GB62 and GB63 according to the invention which contains 0.1% of pigments than for the GB61 gel which does not contain any.

(163) Nevertheless, the difference in terms of the number of flakes and of average area is not significant. The flakes have a millimetric size with an average size around 1 mm.sup.2 as this is desired in the requirements specification of vacuumable gels.

(164) According to this example, the red iron oxide pigments therefore do not fundamentally alter, at such concentrations, the fracturation of the gel.

Example 6

(165) In this example, it is shown that the coloration of the gels according to the invention is preserved over time.

(166) More exactly, in this example, the question is to show that the coloration is constant between a gel stored for several weeks and a fresh gel which has just been prepared.

(167) For this, two GB62 gels (red) are made according to the method described in Example 1, and they are then analyzed in the wet condition with the UV-3600 spectrometer according to the same method as in Example 1.

(168) The first of these GB62 gels (red) is stored, kept for 4 months following its making, before conducting the analysis. This gel is called an old stored gel.

(169) The second of these gels GB62 is made the day before the measurement. This gel is called a new, fresh gel.

(170) The results of the analyses are shown in FIG. 15.

(171) Both curves, respectively for the preserved gel and the fresh gel have a similar aspect since these gels contain the same Ferroxide 212M pigment at the same concentration.

(172) However, the fresh gel has much less significant absorbance than the old gel. This may be due to the strong coloring power of micronized red iron oxide pigments. Indeed, a very small difference in the mass of the added pigment (and this up to 0.1% by mass) may strongly modify the coloration of the pigmented gel.

Example 7

(173) In this example, the biocidal properties of the gel according to the invention are studied.

(174) Indeed, it should be checked that the biocidal properties of the gel are not altered by adding pigments in its formulation.

(175) To do this, the biocidal efficiency of the GB62 pigmented gel according to the invention and of the GB61 white gel without any pigment are tested on a contaminating biological species, i.e. spores of Bacillus thuringiensis, non-pathogenic similar to the spores of Bacillus anthracis.

(176) Under a hood with lamina flow and in a sterile way, two autoclaved stainless steel supports are contaminated with 10.sup.7 spores of Bacillus thuringiensis by carrying out a deposition of 100 l of a liquid contaminating solution containing 10.sup.8 spores of Bacillus thuringiensis (B.T.) per ml.

(177) Once the supports are dry, the gels to be tested are spread out on the supports with an average thickness of 0.6 mm and are left to dry under the hood for 3 h-3 h30 mins. Next, the dry gel flakes are brushed and recovered in 30 ml of a nutrient medium LB. Also, the supports cleared of the flakes are placed in tubes with 30 ml of nutrient medium LB. After 1 h of incubation of the tubes at 30 C. with stirring, 30 l of LB are sampled in each of the tubes, and then spread at the centre of Petri dishes containing gelled LB. The dishes are then placed in the incubator at 30 C. for 24 h.

(178) The obtained results are shown in FIG. 16 (A, B). It appears that the number of colonies present after 24 h of incubation on the surface of the gelled LB of the different dishes is of the same order of magnitude. Indeed, the development of a colony corresponds to the growth of a spore not inactivated by the biocidal gel.

(179) By knowing that 30 l on the 30 ml of the recovered LB medium were spread on the dishes, i.e. 1/1,000.sup.th, it may be estimated that on the 4 dishes shown, there remains after decontamination of the supports by the gel, about 10.sup.4 spores of active B.T. over the 10.sup.7 spores initially deposited on the supports, i.e. a lowering of 3 on a logarithm scale due to the effect of the gels, which are either pigmented or not (these biological counts have an accuracy to within a power of ten).

(180) This example shows that the biocidal efficiency of the basic gel is therefore not significantly altered by the addition of red iron oxide pigments.

CONCLUSION FROM THE EXAMPLES

(181) The examples provided above show that the addition of micronized iron oxide pigments to a decontamination gel provides an actual improvement for the application of the vacuumable gel technology within the scope of a post-event use, for example subsequent to an industrial accident, or a terrorist attack.

(182) Indeed, the addition in the gels according to the invention of a small amount of pigments gives the possibility of improving viewing, by intervention teams in NRBC overalls, of areas of the surface of a contaminated material covered with the gel as compared with the other areas of the surface of this material.

(183) Moreover, possible discoloration of the pigmented gel following the drying of the latter is another of the advantages of the pigmented gels according to the invention. Indeed, this discoloration gives the possibility of clearly and specifically evaluating the state of progression of the drying of the gel which goes together with the progress of the decontamination method. It is thus possible to ensure total and complete drying of the decontamination gel before its suction/conditioning.

(184) These advantageous properties of the gels according to the invention, due to the presence in the gels according to the invention of mineral pigments and notably of micronized iron oxide pigments, are obtained without altering the physico-chemical properties of these gels which make them applicable within the scope of a so called vacuumable gel method. Indeed, the properties of fracturation and of drying the gels according to the invention as well as their viscosity and their threshold stress are not deteriorated by adding pigments.

REFERENCES

(185) [1] CUER F., FAURE S., Gel de dcontamination biologique et method de dcontamination de surfaces utilisant ce gel, FR-A1-2962046 and WO-A1-2012/001046. [2] HOFFMAN D., Mc GUIRE R., Oxidizer gels for detoxification of chemical and biological agents, U.S. Pat. No. 6,455,751. [3] HARPER B., LARSEN L., A comparison of decontamination technologies for biological agents on selected commercial surface materials, Biological weapons improved response program, April 2001. [4] FAURE S., FOURNEL B., FUENTES P., LALLOT Y., Method de traitement d'une surface par un gel de traitement, et gel de traitement, FR-A1-2 827 530. [5] FAURE S., FUENTES P., LALLOT Y., Gel aspirable pour la dcontamination de surfaces et utilisation, FR-A1-2 891 470.