BIOMASS DEGRADATION PROCESSES USING A TIO2-BASED PHOTOCATALYST LEADING TO ACTIVATED BIOMASS

Abstract

Process for the preparation of a TiO.sub.2 photocatalyst/biomass carrier, with TiO.sub.2/M.sub.xO.sub.y nanocrystals, of at least nanometric size and photocatalysis-active at least in visible light, consisting of the following steps: a) preparation and heating of an aqueous solution of hydrochloric acid with a given pH, between 0 and 6, and at a temperature between 20° C. and 60° C., with no surfactant, b) addition to the acidic aqueous solution of the titanium oxide precursor, or the mixture of a TiO.sub.2 titanium oxide precursor and at least one other precursor of another M.sub.xO.sub.y oxide, consisting, 80% to 100%, of TiO.sub.2 moles and 0% to 20% of moles of another metal or semi-metal M.sub.xO.sub.y oxide, a precipitate then forming, and stirring of the acidic aqueous reaction medium obtained, so as to dissolve the precipitate; c) an immersing step of the carrier in the acidic aqueous reaction medium, d) a heating step of the acidic aqueous reaction medium, the carrier for crystallizing the titanium oxide precursors, or the mixture of the titanium oxide precursor and at least one other precursor of the other metal or semi-metal oxide, e) a possible water rinse step and a biomass carrier recovery step with TiO.sub.2/M.sub.xO.sub.y nanocrystals, bound by covalent bonds to the biomass carrier.

Claims

1. A preparation process of a TiO.sub.2 photocatalyst/biomass carrier, with TiO.sub.2/M.sub.xO.sub.y nanocrystals, of at least nanometric size and photocatalysis active at least in visible light, comprising the following substeps: a) preparation and heating of an acidic aqueous solution (1) to a given pH between 0 and 6, and with no surfactant, b) addition to the aqueous acid solution (1) of a titanium oxide precursor, or a mixture of a TiO.sub.2 titanium oxide precursor and at least one other precursor of another M.sub.xO.sub.y oxide, consisting, 80% to 100%, of TiO.sub.2 moles and 0% to 20% of moles of another metal or semi-metal M.sub.xO.sub.y oxide, a precipitate then forming, and stirring of the acidic aqueous reaction medium (3) obtained, so as to dissolve the precipitate; c) immersion of a biomass carrier (2) in the acidic aqueous reaction medium to condense the precursors of the acidic aqueous reaction medium on its surface, which bind to this surface by covalent bonds, d) heating of the acidic aqueous reaction medium (3) at a temperature between 30° C. and 90° C., the biomass carrier (2) for crystallizing the titanium oxide precursors, or the mixture of a titanium oxide precursor and at least one other precursor of the other metal or semi-metal oxide on its surface, the crystallizing precursors, once bound to the biomass surface; e) recovery of the biomass carrier (4) with TiO.sub.2/M.sub.xO.sub.y nanocrystals, bound to the biomass carrier by covalent bonds.

2. The process according to claim 1, wherein the titanium precursor is selected from the group comprising titanium isopropoxide, Na.sub.2Ti.sub.3O.sub.7 sodium titanate or a derivative.

3. The process according to one of claim 1, wherein the metal oxide is selected from the group comprising SiO.sub.2, ZrO.sub.2, Al.sub.2O.sub.3, Fe.sub.2O.sub.3, CeO.sub.2, MgO, CuO, NiO, Cu.sub.2O, SnO.sub.2, RuO.sub.2, Bi.sub.2O.sub.3, WO.sub.3, V.sub.2O.sub.5, Ag.sub.3PO.sub.4.

4. The process according to claim 1, wherein the steps are performed in open air without any organic co-solvent.

5. The process according to claim 1, wherein in step a), the pH is chosen equal to 5 so as to obtain nanocrystals on the biomass carrier having a stable brookite crystalline form, or the pH is between 0 and 2 so as to obtain nanocrystals on the biomass carrier having a rutile crystalline form.

6. The process according to claim 1, wherein the first step a) of adding a titanium precursor is performed with the addition of a WO.sub.3 metal oxide, the pH of the reaction medium being between 0 and 5.

7. The process according to claim 1, in the heating step a) of the aqueous solution of hydrochloric acid, the heating temperature is between 20° C. and 60° C.

8. The process according to claim 1, wherein the step of heating d) the acidic aqueous reaction medium comprising the biomass carrier is performed between 30° C. and 100° C.

9. The process according to claim 1, wherein the step of heating d) the acidic aqueous reaction medium (3) comprises heating at a temperature between 30° C. and 60° C. for a given first duration, and heating at a temperature between 50° C. and 90° C. for a given second duration, the first duration being several hours, the second duration being several hours.

10. A photocatalyst biomass carrier (4), which is photocatalysis active at least in visible light and which is at least nanometric in size with TiO.sub.2/M.sub.xO.sub.y nanocrystals, bound to its surface by covalent bonds, produced by the method of claim 1, these nanocrystals being composed 80 to 100% of TiO.sub.2 moles and 0 to 20% of other M.sub.xO.sub.y metal or semi-metal oxide moles.

11. A biomass carrier with TiO.sub.2/M.sub.xO.sub.y nanocrystals according to claim 10, wherein the biomass carrier (2) is selected from the group comprising: glucose, sorbitol, monocrystalline cellulose.

12. A biomass carrier with TiO.sub.2/M.sub.xO.sub.y nanocrystals according to claim 10, wherein the biomass carrier (2) is selected from the group comprising algae and wood.

13. The biomass carrier with TiO.sub.2/M.sub.xO.sub.y nanocrystals according to claim 9, of micrometric, millimetric, centimetric size or greater.

14. A degradation process of TiO.sub.2 photocatalysts/non-degraded biomass carrier with TiO.sub.2/M.sub.xO.sub.y nanocrystals, from a first biomass carrier performed according to claim 9, said process comprising: a step f) of photocatalytic degradation at least in visible light, of the first biomass carrier (4) with TiO.sub.2/M.sub.xO.sub.y nanocrystals, to obtain a residue (7) and decomposition products; a step g) of treatment of the residue (7) in an aqueous acidic solution (8), to obtain a recycled photocatalyst solution with TiO.sub.2/M.sub.xO.sub.y nanoparticles reactive for the graft, forming a new aqueous acidic reaction medium, the reactive TiO.sub.2/M.sub.xO.sub.y nanoparticles of the residue being created from the first biomass carrier degraded into decomposition products; a step h) adding a new biomass carrier (2) to the recycled photocatalyst solution; a step i) heating the new aqueous acidic reaction medium, a drying step j), to form a new biomass carrier (4) with TiO.sub.2/M.sub.xO.sub.y nanoparticles, bound by covalent bond on the surface, the new biomass carrier (4) being photocatalysis active at least in visible light.

15. The degradation process according to claim 14, wherein: the new biomass carrier (4) with TiO.sub.2/M.sub.xO.sub.y nanoparticles, from step j), is degraded during a new step f), the degradation process of the biomass carrier being performed again in new steps g) to j) to obtain a new biomass carrier (4) with TiO.sub.2/M.sub.xO.sub.y nanoparticles from step j), which is degraded again in another new step f) and so on, the process operating following a cycle enabling the recovery of the TiO.sub.2/M.sub.xO.sub.y nanoparticles from the residue (7) that are reactive for the grafting, and that are bound by covalent bonds to each new biomass carrier (4), added in the acidic aqueous reaction medium (3) containing them.

16. The degradation process according to claim 14, wherein step f) of photocatalytic degradation is performed in natural light or under visible radiation.

17. The degradation process according to claim 14, wherein the photocatalytic degradation step is performed by contact with air oxygen, at atmospheric pressure.

18. The degradation process according to claim 14, wherein the decomposition products are alcohol-type.

19. The degradation process according to claim 14, wherein the decomposition products are selected from the following list: acetone, isopropanol, methanol, glycerol, acetic acid, glyoxal, ethanol.

20. The degradation process according to claim 14, wherein the decomposition products comprise biogases such as hydrogen and/or methane

21. The degradation process according to claim 14, wherein the decomposition products are carried out without agitation of the aqueous solution during step f).

22. A photocatalysis-active biomass carrier at least in visible light, produced by grafting of nanoparticles from the degradation process defined according to claim 14.

23. The carrier according to claim 22, wherein the carrier is a biomass of a different nature than the biomass used during the defined degradation process of claim 14.

24. The carrier according to claim 23, wherein the first biomass used in the degradation process is pine or algae, and the second biomass used is algae or pine respectively.

25. A degradation process of a solid element with a carrier described according to claim 8, presenting the following steps: a) preparation of an aqueous solution comprising a biomass carrier with a titanium oxide precursor, or a mixture of a TiO.sub.2 titanium oxide precursor and at least one other precursor of another M.sub.xO.sub.y oxide or nanoparticles from a first degradation, to obtain a carrier according; b) immersion of a solid element to undergo degradation in the solution of step a); c) radiation or darkening of the solution; d) degradation of the biomass carrier and solid element.

Description

[0078] Other objects and advantages of the invention will be seen from the description of embodiments given below, with reference to the appended drawings, in which:

[0079] FIG. 1 is a diagram representing the steps of the biomass carrier degradation process by a TiO.sub.2 catalyst, showing the recycling of the residue from the photocatalysis;

[0080] FIG. 2 is a diagram showing changes in methyl orange concentration by various reactive biomasses (TiO.sub.2/pine, TiO.sub.2/Al.sub.2O.sub.3/pine) compared to degradations obtained with commercial titanium dioxide (Aeroxide TiOP25), and degradations obtained with photocatalysts not supported by biomass (TiO.sub.2/Al.sub.2O.sub.3), photocatalyst binding (TiO.sub.2 or TiO.sub.2/Al.sub.2O.sub.3) to biomass such as crushed pine increasing the degradation capacities of methyl orange;

[0081] FIG. 3a represents the absorbance variations for activated biomass (TiO.sub.2/Pine (crushed pine)) before and after two weeks of exposure to natural light;

[0082] FIG. 3a-1 represents an enlargement of FIG. 3a in the 1,800-800 cm.sup.−1 region;

[0083] FIG. 3b represents the absorbance variations for activated biomass (TiO.sub.2/Al.sub.2O.sub.3 95/5 pine (crushed pine)) before and after one week of exposure to light;

[0084] FIG. 4 represents the absorbance variations for activated glucose, before and after one week of exposure to natural light;

[0085] FIG. 4-1 and FIG. 4-2 represent the enlargements of FIG. 4 in the 3,750-2,750 cm.sup.−1 and 1,150-900 cm.sup.−1 regions, respectively;

[0086] FIG. 5 represents the absorbance variations for sorbitol, before and after one week of exposure to natural light;

[0087] FIG. 6 represents the absorbance variations for activated biomass of brown algae (Pelvetia canaliculata), before and after one week of exposure to natural light;

[0088] FIG. 7 represents the gas chromatography tracking data with flame ionization detector, during treatment of crushed pine biomass in aqueous solution, concentration of 1 g/L of activated biomass being dissolved and exposed to natural light;

[0089] FIGS. 7-1, 7-2, 7-3 represent the enlargements of FIG. 7 in the 2.55-2.80 min, 3.10-3.50 min, and 10.1-11 min regions, respectively;

[0090] FIG. 8 represents the gas chromatography tracking data with flame ionization detector, during treatment of crushed pine activated biomass, the activated biomass supporting recycled titanium dioxide;

[0091] FIGS. 9 to 12 are electron microscopy images of composite materials transmission TiO.sub.2/biomass according to the invention, FIG. 9 being a TiO.sub.2/WO.sub.3/crushed pine material, FIG. 10 a TiO.sub.2/cellulose material, FIG. 11 a TiO.sub.2/crushed pine material and FIG. 12 a TiO.sub.2/glucose material;

[0092] FIGS. 13a, 13b and 13c, respectively, are photographs of a Teflon stir bar (new PTFE, FIG. 13a), a stir bar after 78 hours of stirring in an aqueous solution of TiO.sub.2/pine (FIG. 13b), [and] a beaker containing the supernatant isolated from the solution after 78 hours of radiation (FIG. 13c);

[0093] FIG. 14 represents the absorbance of the supernatant, perfectly corresponding with the absorbance of the PFTE;

[0094] FIG. 15 represents the monitoring of the degradation of the pine in the TiO.sub.2/pine carrier by following the variations in absorbance, degradation of the Teflon after 21 hrs;

[0095] FIG. 16 is a photograph, representing a new Pyrex stir bar (left of the image), and a Pyrex stir bar in the presence of degradation of the TiO.sub.2/pine carrier (right of the image);

[0096] FIGS. 17a and 17b show the monitoring of the degradation of the pine in the TiO.sub.2/pine carrier by following the variations in absorbance, degradation of the Pyrex glass (borosilicate) after 96 hrs;

[0097] FIG. 18 represents the characteristic absorbance of borosilicate;

[0098] FIG. 19 is a photograph that represents a new polypropylene stopper (left) and a polypropylene stopper after having been in contact with splashed algae degradation solution from a TiO.sub.2/algae carrier (right of image);

[0099] FIG. 20 shows the monitoring of the degradation of the algae in the TiO.sub.2/algae carrier by following the variations in absorbance, degradation of the polypropylene after 80 hrs;

[0100] FIG. 21 is a photograph that represents a new septum (left) and a septum after being placed in a pine degradation of a TiO.sub.2/pin carrier (right of the image);

[0101] FIG. 22 represents the characteristic FTIR spectrum of polypropylene;

[0102] FIGS. 23a, 23b and 23c represent the GC-MS analysis chromatogram of the degradation of 3-fold concentrated pine, algae and pine, respectively;

[0103] FIGS. 24a to 24g represent images of paperclips placed in aqueous solution (water) for 78 hours by visible light (8,0001 m) with respectively: a) nothing; b) TiO.sub.2/pine; c) TiO.sub.2 of patent EP3393975A1; d) TiO.sub.2 P25 Degussa (Aeroxide); e) TiO.sub.2 P25 Degussa (Aeroxide)+pine; f) TiO.sub.2/algae and g) algae+TiO.sub.2 nanoparticles from a first pine degradation;

[0104] FIGS. 25a to 25g represent images of paperclips placed in aqueous solution (water) for 78 hours in darkness with: a) nothing; b) TiO.sub.2/pine; c) TiO.sub.2 of patent EP3393975A1; d) TiO.sub.2 P25 Degussa (Aeroxide); e) TiO.sub.2 P25 Degussa (Aeroxide)+pine; f) TiO.sub.2/algae and g) algae+TiO.sub.2 nanoparticles from a first pine degradation;

[0105] FIG. 26 is a photograph of a comparison between two pieces of aluminum foil immersed in irradiated aqueous solution for 3 days respectively on the left alone and on the right in contact with the TiO.sub.2/pine carrier;

[0106] FIG. 27 represents the monitoring of the degradation of a methyl orange solution at 10 ppm by UV-Visible spectrophotometry irradiated for 1 hour by visible light (8,0001 m) in the presence of a TiO.sub.2/biomass carrier and TiO.sub.2 of patent EP3393975A1 and TiO.sub.2 P25 Degussa (Aeroxide);

[0107] FIGS. 28a and 28b represent the monitoring of the absorption of methyl orange at 10 ppm by UV-Visible spectrophotometry in the dark for 48 hours in the presence of the TiO.sub.2/biomass carrier and TiO.sub.2 of patent EP3393975A1 and TiO.sub.2 P25 Degussa (Aeroxide);

[0108] FIG. 29 represents the monitoring of the degradation of a solution of rhodamine b (RhB) at 10 ppm by UV-Visible spectrophotometry irradiated for 1 hour by visible light (8,0001 m) in the presence of TiO.sub.2/biomass carrier and TiO.sub.2 of patent EP3393975A1 and TiO.sub.2 P25 Degussa (Aeroxide);

[0109] FIGS. 30a and 30b represent the monitoring of the absorption of rhodamine b (RhB) at 10 ppm by UV-Visible spectrophotometry in the dark for 48 hours in the presence of TiO.sub.2/biomass carrier and TiO.sub.2 of patent EP3393975A1 and TiO.sub.2 P25 Degussa (Aeroxide);

[0110] FIG. 31 is an image obtained by scanning electron microscopy of a sample of algae;

[0111] FIGS. 32a and 32b represent the results of EDX analyses of an algae sample.

[0112] First, refer to FIG. 1.

[0113] In a first step, in an acidic aqueous solution, a titanium precursor is incorporated.

[0114] This aqueous solution is, for example, prepared by heating an acidic aqueous solution at a given pH between 0 and 6, at a temperature between 20° C. and 60° C., by adding hydrochloric acid.

[0115] In a particular implementation, the aqueous solution is at pH 0, and is formed by the addition of 10 g of 35% hydrochloric acid in 50 mL of water.

[0116] The preparation of the aqueous solution is advantageously carried out without the use of a surfactant.

[0117] In one implementation, the titanium precursor is 98% titanium isopropoxide (TTIP, tetraisopropyl orthotitanate CAS 546-68-9). Titanium isopropoxide (Ti(O-i-Pr).sub.4) is a titanium alkoxide.

[0118] In other implementations, the titanium precursor is chosen from Na.sub.2Ti.sub.3O.sub.7 sodium titanate or a derivative.

[0119] In other implementations, a mixture of titanium precursor and metal oxide is used. Metal oxide is selected from SiO.sub.2, ZrO.sub.2, Al.sub.2O.sub.3, Fe.sub.2O.sub.3, CeO.sub.2, MgO, ZnO, NiO, Cu.sub.2O, SnO.sub.2, RuO.sub.2, Bi.sub.2O.sub.3, WO.sub.3, V.sub.2O.sub.5, Ag.sub.3IN.sub.4.

[0120] In a particular implementation, the incorporation of the titanium precursor or the mixture of titanium precursor and a metal oxide is carried out at 50° C., under stirring.

[0121] Preferably, the stirring is strong, for example, magnetic stirring of the order of 800 rpm.

[0122] This stirring dissolves the precipitate that forms instantly.

[0123] Depending on the pH of the acid solution, the TiO.sub.2 obtained is essentially in the form of brookite (when the pH is close to 5), or rutile (when the pH is chosen around 0-2).

[0124] In a particular implementation, the metal oxide is WO.sub.3, and the pH of the reaction medium being between 0 and 5, the TiO.sub.2 obtained is mainly in an anatase form.

[0125] Upon total dissolution of the precipitate that forms instantly, a biomass product (biomass carrier) is added.

[0126] For example, 300 mg of biomass are added to the acidic aqueous solution formed by adding 10 g of 35% hydrochloric acid in 50 mL of water, and containing the titanium precursor and possibly metal oxide.

[0127] Biomass is organic matter of plant (including microalgae), animal, bacterial or fungal (fungi) origin, which can be used as a source of energy (bioenergy).

[0128] It can be worked, crushed, etc., to be used as a carrier.

[0129] In one implementation, the biomass carrier is chosen from the group comprising glucose, sorbitol, monocrystalline cellulose.

[0130] In another implementation, the biomass carrier is crushed pine, an algae.

[0131] Advantageously, biomass is not charcoal.

[0132] Stirring then becomes moderate at the onset of a new precipitate.

[0133] In one implementation, stirring is performed using a magnetic stirrer at approximately 300 rpm.

[0134] For this precursor solution, the temperature is maintained at 50° C. for 24 hours and then increased to 90° C. for 24 hours.

[0135] After cooling, the reaction medium is filtered under vacuum and then dried in the oven, advantageously between 30 and 60° C.

[0136] Vacuum filtration makes it possible to isolate an activated biomass 4 that is advantageously presented in the form of a carrier with TiO.sub.2 nanocrystals, the carrier being at least micrometric or millimetric in size.

[0137] Activated biomass 4 can be degraded in two ways.

[0138] In a first way, the activated biomass 4 is degraded into gas, by contact with oxygen from the air under visible radiation (for example, performed by a halogen lamp 500 W 8,550 lumens).

[0139] In a second way, the activated biomass 4 is dispersed in water 6, at a concentration of about 1 g/L under visible radiation (for example, performed by a halogen lamp 500 W 8,550 lumens).

[0140] When the activated biomass 4 is altered, [upon appearance of the degradation compounds] and decrease in their intensity, the residue 7 is immersed in an acidic aqueous solution.

[0141] In one implementation, the acidic aqueous solution 8 is obtained by mixing 10 g of HCl 35% in 50 mL of water, at 90° C.

[0142] Biomass 2 is then incorporated into the reaction medium under vigorous stirring.

[0143] For example, 300 mg of biomass 2 are incorporated into the acidic aqueous solution 8 obtained by mixing 10 g of HCl 35% in 50 mL of water, at 90° C.

[0144] After 48 hours, the reaction medium is filtered and the solid activated biomass obtained is rinsed with water and then dried in an oven, for example, from 30° C. to 60° C., or between 40° C. and 50° C.

[0145] The activated biomass obtained can then undergo photocatalysis as described above (dry or aqueous), the process operating in a cycle.

[0146] Now refer to FIG. 2.

[0147] The degradation of a dye by photocatalysis, for example, methyl orange or rhodamine B, may create titanium dioxide sensitization, the dye being a conjugate compound. This mechanism is known as a model for photodegradation.

[0148] FIG. 2 is a diagram showing changes in methyl orange MO concentration by various reactive biomasses (TiO.sub.2/pine, TiO.sub.2/Al.sub.2O.sub.3/pine) compared to the degradations obtained with commercial titanium dioxide (Aeroxide TiOP25), and the degradations obtained with photocatalysts not supported by biomass (TiO.sub.2/Al.sub.2O.sub.3), photocatalyst binding (TiO.sub.2 or TiO.sub.2/Al.sub.2O.sub.3) to a biomass such as crushed pine increasing the degradation capabilities of methyl orange.

[0149] As shown in FIG. 2, the binding of the photocatalyst to a biomass improves the degradation of methyl orange. The results obtained for titanium dioxide bound to crushed pine are higher than those obtained with unbound titanium dioxide, or commercial titanium dioxide. The results obtained for the TiO.sub.2/Al.sub.2O.sub.3photocatalyst bound to crushed pine are higher than those obtained with this same photocatalyst unbound to biomass.

[0150] FIGS. 3 to 6 represent the results of absorbance measurements during biomass photocatalytic degradation tests, with 40 mg of activated biomass left in the open, under natural radiation.

[0151] FIG. 7, 7-1, 7-2, 7-3 represent the gas chromatography tracking data with flame ionization detector, during treatment of crushed pine biomass in aqueous solution, concentration of 1 g/L of activated biomass being dissolved and exposed to natural light. Peaks appear: at 2.6 minutes for acetone (see FIG. 7-1); at 3.1 minutes for methanol and at 3.3 minutes for isopropanol (see FIG. 7-2), then decreases in acetone and isopropanol peaks, and other peaks appear: at 10.4 minutes for glyoxal or glycerol (see FIG. 7-3).

[0152] FIG. 8 represents the gas chromatography tracking data with flame ionization detector, during treatment of crushed pine activated biomass, the activated biomass carrying recycled titanium dioxide. Comparison of results obtained before exposure to natural light and after 1,100 minutes of exposure to natural light shows the attenuation of typical pine biomass peaks, with recycled titanium dioxide retaining its photocatalytic capabilities.

[0153] The process has numerous advantages.

[0154] Metal oxides are bound to micro or millimetric surfaces, without the risk of dissemination in the environment and without loss of reactivity.

[0155] Metal oxide carriers can undergo degradation by photocatalysis.

[0156] Composite materials enable the treatment and recovery of biomass products, such as for example, algae, wastewater treatment plant sludge.

[0157] The process enables the production of usable decomposition products such as alcohol (isopropanol, methanol, ethanol, glycerol) or others (acetone, acetic acid, etc.) or biogas (hydrogen, methane, syngas).

[0158] The process uses natural light, visible light, and UV light.

[0159] Advantageously, the degradation process works in the dark.

[0160] The process is integrated in situ, all process steps can be performed at a single site.

[0161] The process does not use solvent and the working temperatures are moderate.

[0162] In another aspect of the invention, a biomass carrier is photocatalysis-active at least in visible light, by bonding of the nanoparticles from the degradation process.

[0163] Advantageously, the carrier is a biomass of a different nature than the biomass used during the degradation process.

[0164] Advantageously, the first biomass used during the degradation process is pine or algae, and the second biomass used is algae or pine, respectively.

[0165] The invention proposes, according to another aspect, a process of degradation of a solid element with one of the carriers described in this invention, the process presenting the following steps: [0166] a) preparation of an aqueous solution comprising a biomass carrier with a titanium oxide precursor, or a mixture of a TiO.sub.2 titanium oxide precursor and at least one other precursor of another M.sub.xO.sub.y oxide or nanoparticles from a first degradation, to obtain a carrier according to one of the processes described in the present invention; [0167] b) immersion of a solid element to undergo degradation in the solution of step a); [0168] c) radiation or darkening of the solution; [0169] d) degradation of the biomass carrier and solid element.

[0170] The solid element can be metal, polymer such as plastic, Teflon etc.

[0171] Advantageously, the degradation process for a solid element works in the dark.

[0172] As shown in FIG. 15, biomass degradation leads to Teflon degradation (erosion), a supernatant in the solution appears.

[0173] As shown in FIGS. 17a and 17b, biomass degradation leads to Pyrex glass degradation.

[0174] As shown in FIG. 19, biomass degradation leads to degradation of the cap coating, i.e. of the polypropylene.

[0175] As shown in FIG. 22, the septum degrades after the passage of the TiO.sub.2/biomass carrier (pine and brown algae), as shown in FIGS. 23a, 23b and 23c. The chromatograms show a peak of benzothiazole, this compound is used as an additive in the manufacture of rubbers, the compound is not present in crushed pine or brown algae.

[0176] In FIGS. 24, we note very different oxidations: a) the presence of a TiO.sub.2 material that leads to oxidation, b) the addition of biomass in TiO.sub.2/biomass accelerates oxidation, c) synthesized materials superior to commercial material, d) the addition of algae to the TiO.sub.2 [pine] material (pine degraded by photocatalysis a first time) does not decrease oxidation (no loss of reactivity).

[0177] In FIGS. 25, two findings are observed: [0178] a) the presence of oxidation (thus reactivity) in the dark; [0179] b) the reactivity is more intense for synthesized materials and even more in the presence of biomass, including by exchanging the type of biomass in the recycling step (TiO.sub.2 [pine]+algae).

[0180] In FIG. 26, the bleaching of the surface of the aluminum foil is observed after immersion in an aqueous solution of TiO.sub.2/pine radiated for 48 hours. This phenomenon seems to indicate the presence of oxidized aluminum. Aluminum foil alone in solution has no bleaching.

[0181] In FIG. 27, several observations: [0182] a) the commercial material even with biomass has a very low reactivity; [0183] b) reactivity is dependent on the type of biomass used (TiO.sub.2/algae<TiO.sub.2/pine) [0184] c) this specificity of biomasses for the dye is always present in cycle 2 (recycling step) [0185] d) pine provides a better biomass source in TiO.sub.2-based materials for methyl orange degradation.

[0186] In FIG. 28, several observations: [0187] a) synthesized materials>commercial material even in the presence of biomass; [0188] b) lower reactivity than light but present (mild shift in the maximum absorbance wavelength, and different spectra below 300 nm); [0189] c) the specificity of the biomasses is always present, including in cycle 2 (recycling step).

[0190] In FIG. 29, several observations: [0191] a) commercial material even with biomass has very low reactivity; [0192] b) reactivity is dependent on the type of biomass used, rhodamine B does not degrade in the same way according to TiO.sub.2/algae and TiO.sub.2/pine; [0193] c) This specificity is related to the presence of metal (Mg, Al and Si) in algae; [0194] d) Specificity for the dye still present in cycle 2 (recycling step).

[0195] The photodegradation of the elements by reduction or oxidation in the presence of TiO.sub.2 in aqueous solution is known. On the other hand, there is no information in the literature on the degradation of dark elements in the presence of TiO.sub.2 or TiO.sub.2 with a biomass carrier in aqueous solution.

[0196] Reactivity in the dark is remarkable for TiO.sub.2 materials with a specific biomass carrier.

[0197] In the method of the present invention, the aqueous solution of TiO.sub.2 or TiO.sub.2 with a biomass carrier is prepared in daylight.

[0198] During the reaction, the electrons formed by radiation and then trapped on the surface of TiO.sub.2 can continue to react even when the radiation stops. Radiation of TiO.sub.2 nanoparticles (rutile) with 4K UV-Visible light gives weak signals of electrons trapped on the surface of TiO.sub.2; however, after the light was stopped, very strong EPR signals corresponding to the Ti.sup.3+ cation were observed.

[0199] In addition, radicals formed during light exposure may benefit from stabilization due to the presence of biomass. Radical stabilization by steric protection due to the presence of macromolecular systems. These systems are found in biomass either in wood (lignin, cellulose, hemicellulose) or in algae (polysaccharides, chlorophylls, carotenoids, etc.).