WO2013062398A1

WO2013062398A1 - Synthesis of materials for discolouration and degradation of organic pollutants in water: graphene alone and graphene nanocomposite (graphene-titanium dioxide)

Info

Publication number: WO2013062398A1
Application number: PCT/MA2012/000026
Authority: WO
Inventors: Mohamed ZAHOUILY; Abderrahim SOLHY; Rachid AIT BELALE
Original assignee: Moroccan Foundation For Advanced Science, Innovation & Research (Mascir)
Priority date: 2011-10-26
Filing date: 2012-10-25
Publication date: 2013-05-02
Also published as: MA34204B1; WO2013062398A4

Abstract

The invention relates to a method for treating water containing organic pollutants (dyes and pesticides), in particular with a view to reusing said water for irrigation, in industry or even as drinking water. This method is also applicable to the treatment of industrial effluents rich in organic impurities. The developed method relates to the use of photo-catalysts based on nanostructured carbon and a nanosized metal oxide. The scientific and technological obstacles of this method actually lie in the preparation of nanocomposites based on graphite and functionalised graphene (graphite oxide, graphene, graphene-titanium dioxide nanocomposite (GF@TiO₂)) capable of degrading organic pollutants in water in the absence of ultra-violet (UV) radiation, and the production methods and uses thereof.

Description

SYNTHESIS OF MATERIALS FOR DECOLORATION AND DEGRADATION OF ORGANIC POLLUTANTS IN WATER: GRAPHENE ALONE AND GRAPHENE NANO COMPOSITE (GRAPHENE / TITANIUM DIOXIDE)

State of the art

Carbon is known to have four allotropic forms namely: diamond, graphite, fullerenes and carbon nanotubes. The tubular structure of nanotubes gives them unique mechanical, electrical and chemical properties. As such, they are commonly used in composite materials.

Graphene, long considered a virtual object, has recently acquired a real existence since the work of Novoselov et al. [K. S. Novoselov, AK Geim, SV Morozov, D. Jiang, Y. Zhang, SV Dubonos, IV Grigorieva, and AA Firsov "Electric field effect in atomic thin carbon films", Science, Volume 306, pp 666-669 (2004) ; KS Novoselov, AK Geim, SV Morozov, D. Jiang, MI Katsnelson, IV Grigorieva, SV Dubonos, AA Firsov, "Two-dimensional gas of mass Dirac fermions in graphene", Nature, Volume 438, pp 197-200 (2005) ] which describe the electronic properties of this singular object. Since 2004 and the publication of Novesolov et al., The world of physics is passionate about the electronic properties of graphene or graphite insulated plane (Electric field effect in atomic thin carbon films, Novoselov et al., Science Volume 306, 666 (2004)). )].

On the other hand, conventional water treatments, to make it usable, include, among other steps, a step of removing organic compounds. This step is becoming increasingly important because of increasing contamination of water resources by agriculture, industry and individuals using chemicals. Conventional treatments are not always suitable for solving the problem because some organic pollutants are not completely destroyed. Certain halogenated compounds (in particular chloroform, carbon tetrachloride, etc.) are very refractory to conventional treatments such as activated carbon adsorption or ozonation alone. We have therefore thought of the photocatalytic destruction of organic pollutants. This photocatalytic destruction transforms them into carbon dioxide, water and diluted mineral acids, which are non-toxic substances. In addition, it has been shown that this technique is not selective and can treat most organic pollutants. Conclusive tests have been carried out on chlorinated solvents, polychlorinated biphenyls, dioxides, pesticides and dyes [cf. D. Ollis, E. Pelizetti and N. Serpone, "Photocatalzed Destruction of Water Contaminants", Environmental Science and Technology, Volume 25, No. 9, pp. 1532-1528 (1991); Y. Shaoqing, H. Jun, W. Jianlong "Radiation-inducedcatalyticdegradationofp-nitrophenol (PNP) in the Presence of Ti0 ₂ Nanoparticles", Radiation Physics and Chemistry, Volume 79, pp 1039-1046 (2010); X. Wang, Y. Liu, Z. Hu, Chen Y., Liu W, Zhao G. "Degradation of methyl orange by composite photocatalysts nano-TiO ₂ immobilized on activated carbons of different porosities" Journal of Hazardous Materials, Volume 169 , pp. 1061 - 067 (2009).]. Heterogeneous photocatalysis most often uses TiO ₂ , SrTiO ₃ , Fe ₂ O ₃ , FeTiO ₃ , CrO ₃ , MnO ₂ , Si, Ge, ZnO type semiconductor oxides. Other materials have also been tested, in particular quantum-dots CdS and GaP which have the advantage of absorbing, relative to TiO ₂ , a larger fraction of the solar spectrum. Unfortunately, these semiconductors are degraded during the photocatalytic process. Ti0 ₂ , on the contrary, is stable and constitutes a good compromise between efficiency and stability. Its non-toxicity and its low cost also have considerable advantages.

Semiconductor materials are differentiated from non-semiconductor materials by their physically distinct valence and conduction bands. When the semiconductor is irradiated at an appropriate wavelength, electrons move from the valence band, saturated with electrons, to the electron-free conduction band. This creates positive gaps (holes) in the valence band and the gap between the bands allows the electrons and gaps to keep their excited states longer. The electrons and the gaps rising on the surface of the semiconductor, they can be trapped by the compounds absorbed on the surface and participate in oxidation-reduction reactions. Thus, the organic compounds will be oxidized and converted into non-toxic compounds such as CO ₂ , H ₂ O and HCl. After desorption of non-toxic compounds, the semiconductor material regenerates, the process is, by definition, catalytic.

Photocatalysis is linked to two complementary phenomena, the first being a surface reaction and the other a reaction internal to the cell, due respectively to the presence of free electrons and hydroxyl radicals. In addition to these two phenomena, different factors can modify the reactions catalyzed by a semiconductor and we can, by playing on the presence of acceptors or electron donors, the intensity of the light, the temperature, the nature of the semiconductor, the polarity of the solvent and the semiconductor mass, optimize the photocatalytic transformation.

Photocatalysis is currently used for the treatment of water for distribution as drinking water, by passing water through semiconductor layers in different forms (woven fabric, powder in suspension, ceramic deposit, beds, etc.) irradiated with UV light. The consumption of the semiconductor is very important because of the large volumes of water to be treated. There are several problems with water remediation, both economically and environmentally. Indeed, an expensive filtration step is necessary, in some cases, to recover the catalyst. Under these conditions, the catalyst can only be recovered with a membrane process, which considerably increases the cost of the treatment. In addition, the large catalyst load prevents good radiation transmission.

Currently, photocatalysis processes are a priori not applicable to the treatment of wastewater loaded with suspended solids which increases the UV transmission problems and which would quickly foul both the catalyst bed and the UV lamps immersed in the water to be treated.

The invention solves these problems by providing a water treatment process containing organic pollutants (dyes or pesticides), a process in which the degradation of organic pollutants in water is carried out using materials based on graphite, graphene and others under sunlight and in the absence of ultraviolet (UV) irradiation.

DESCRIPTION OF THE INVENTION

The present invention is specifically intended to meet this need by providing a process for the preparation and use of graphite or graphene-based materials in the degradation of organic pollutants in water in the absence of UV irradiation. The method comprises the following steps:

a) Preparation of Graphite Oxide (GO): chemical oxidation;

b) Exfoliated graphene: exfoliation and chemical reduction with hydrazine hydrate;

c) Functionalization of exfoliated graphene by attacking a mixture of acids;

d) Synthesis of graphene-titanium dioxide nanocomposites in the presence or absence of anionic or cationic suricactant;

e) Degradation of organic pollutants in water in the absence and presence of UV irradiation.

According to one aspect of the invention, there is provided a process for the treatment of aqueous effluents containing industrial pollutants characterized by the use of heterogeneous photocatalysis in the presence of catalysts based on graphite and / or graphene and in the absence or the presence of ultraviolet (UV) irradiation, and preferably under sunlight.

According to a second aspect of the invention, there is provided a process according to claim 1, characterized by the use of graphite oxide as a photo-catalyst for the degradation of organic pollutants in water.

According to a third aspect of the invention, there is provided a process according to claim 1, characterized by the use of functionalized graphene, via the creation of functional groups, as a solid support for the degradation of organic pollutants in water.

According to a fourth aspect of the invention, there is provided a process according to claim 1, characterized by the use of graphene-titanium dioxide nanocomposites as a photo-catalyst for the degradation of organic pollutants in water.

According to a fifth aspect of the invention there is provided a process according to claim 1, characterized by the use of semiconductor doped graphene for the degradation of organic pollutants in water.

According to a sixth aspect of the invention, there is provided a process according to claim 4, characterized by the use of a polar and protic solvent such as ethanol and water.

According to a seventh aspect of the invention, there is provided a process according to claim 4, characterized by the use of an anionic or cationic surfactant.

According to an eighth aspect of the invention, there is provided a process according to claim 4, characterized by the use of ultrasound.

According to a ninth aspect of the invention, there is provided a process according to claim 1, characterized by the fact that the solution to be treated contains industrial dyes of the sodium alizarin sulfonate type, methylene blue, bromophenol blue or equivalent concentrations 3 to 100 ppm.

According to a tenth aspect of the invention, there is provided a process according to claim 1, characterized in that the solution to be treated contains organophosphorus pesticides or equivalent of concentrations 3 to 100 ppm.

According to an eleventh aspect of the invention, there is provided a process according to claim 1, characterized in that the reaction is carried out at atmospheric pressure and at temperatures between 18-30 ° C. According to a twelfth aspect of the invention, there is provided a process according to claim 1, characterized in that the photocatalysts lead to a partial and / or total mineralization of the organic pollutant.

According to a thirteenth aspect of the invention, there is provided a process according to claim 1, characterized in that the photocatalysts degrade other organic pollutants.

According to a fourteenth aspect of the invention, there is provided a process according to claim 1, characterized in that the photocatalysts are reusable several times.

This invention makes it possible to eliminate the technological disadvantages due to the use of semiconductors in the form of powder in suspension and to their degradation. In addition, the radiation of the light source is not an obligation which has a practical advantage, economic and avoids the problems associated with transmissions of UV irradiation.

Other characteristics and advantages of the present invention will appear on reading the detailed description which follows, with reference to the appended figures in which:

Figure 1. Evaluation of the importance of irradiation with ultraviolet radiation during the degradation of organic pollutants;

Figure 2. Kinetic study of the degradation of methylene blue in the presence of different materials (graphite oxide, graphene and functionalized graphene nanocomposite (GF) -Ti0 ₂ (GF @ TiO ₂ );

Figure 3. Kinetic study of the degradation of different organic pollutants (BM:

Methylene Blue, SSA: Alizarin Sodium Sulfonate and BBP: Bromophenol Blue);

Figure 4. Influence of pH on the kinetics of degradation of methylene blue in the presence of functionalized graphene nanocomposite - titanium dioxide (GF @ TiO ₂ );

Figure 5: Study of the reuse of functionalized graphene nanocomposite - Ti0 ₂ (GF @ TiO ₂ ) during the degradation of methylene blue;

Figure 6: Infrared spectra of graphite oxide, graphene and GF ₂ TiO ₂ ;

Figure 7: X-ray diffraction of graphite, graphite oxide and graphene;

Figure 8: X-Ray Diffraction of Graphene, Titanium Dioxide and Graphene Titanium Dioxide (GF @ TiO ₂ );

Figure 9: SEM micrograph of graphite oxide (a) and graphene (b);

Figure 10: MET micrograph of nanoparticles of titanium dioxide alone; Figure 11: MET micrograph of graphene alone;

Figure 12: TEM micrograph of graphene nanocomposite graphite-titanium dioxide in the absence of surfactant;

FIG. 13: TEM micrograph of graphene nanocomposite-titanium dioxide (GF @ TiO ₂ ) in the presence of functionalization;

Figure 14: MET Micrograph of Functionalized Graphene Nanocomposite - Titanium Dioxide

(GF @ Ti0 ₂ ) in the presence of surfactant.

DETAILED DESCRIPTION OF THE INVENTION

1. Reagents

The graphite used is a commercial product which is graphite powder, greater than 45 μm in size and with a greater purity of 99.99%, Sigma-Aldrich. The TiCl ₄ used is also of Aldrich quality with a purity of 99%.

2. Method of degradation of organic pollutants

The catalytic degradation of the organic pollutants was carried out in a Pyrex reactor of 500 ml capacity with openings intended to take samples or which serve for the introduction of oxygen. Before use, it is thoroughly washed with distilled water.

The procedure comprises the following steps:

> Preparation of the solution of the organic pollutant (100 ml);

> Introduction of the photo-catalyst;

> stirring in the absence of UV irradiations;

> Samples taken at different reaction times using a syringe followed by filtration to separate the two phases;

> UV / visible spectrophotometer analysis;

> In both cases, the cleaning of all the glassware was carried out by rinsing with distilled water.

The samples taken are filtered on Millipore membrane type 0.45 pm HA. The absorbance measurements were performed using a spectrometer type ASAP MICROMETERS series 2020, UV / Visible. The maximum absorption wavelength is 510 nm. The degradation of the organic pollutants was followed by liquid chromatography coupled to the spectrophotometer. The concentration of the dyes is determined by spectrophotometric determination in the visible range, using the Beer-Lambert law:

A = Log 10 / I = e.C.L (Eq 1)

With:

A: Absorbance, ε: Specific extinction coefficient of the solute, L: Thickness of the optical cell and C: The concentration of the solute.

The pH measurements of the various solutions were carried out using a laboratory pH meter (Crison model pH 25). Beforehand, the calibration was carried out using commercial buffer solutions of pH 4.7 and 10.

3. Preparation of materials based on graphite and graphene a. Preparation of graphite oxide (GO)

At a temperature of between 0 and 5 ° C., 6 g of graphite and 3 g of sodium nitrate (NaN0 ₃ ) are mixed in 140 ml of sulfuric acid (H ₂ SO ₄ ). After homogenization of the mixture, 18 g of potassium permanganate (KMnO ₄ ) is added. The solution is kept at room temperature with stirring for 30 minutes and then a quantity of distilled water is added to the suspension. The suspension is treated with a solution of hydrogen peroxide and then filtered.

The filtra is re-dispersed, washed with a hydrochloric acid solution and then washed several times with distilled water. Graphite oxide is obtained after filtration and drying in an oven. b. Exfoliated graphene

To an aqueous solution of graphite oxide dispersed by sonication for 1 h 30 min is added, 1 ml of hydrazine hydrate or equivalent products. After 12 hours of heating at 00 ° C., the reduced graphene is washed with distilled water several times and dried under vacuum in an oven. vs. Functionalization of exfoliated graphene

An amount of exfoliated graphene was subjected to acid attack. Said mixture contains at least two different types of acid, and preferably three acids. d. Synthesis of functionalized graphene nanocomposites - titanium dioxide (GF @ Ti0 ₂ )

1) Synthesis of nanoparticles of titanium dioxide To a frozen aqueous solution of titanium tetrachloride (50/50 wt%) is added a cationic or anionic surfactant, after complete dissolution, a solution of titanium tetrachloride and ammonia is added, the pH is maintained at 8. After 30 minutes of sonication, nitric acid (1 M) is added until the pH is 2. After stirring for 1 hour, TiCl ₄ and ammonia are added, the pH is maintained at 8 for 30 hours. min then drop to pH equal to 2 by adding nitric acid (1 M). This step is repeated eight to ten times before washing the white precipitate with ethanol and water, and then dried at 120 ° C. The size of the nanoparticles of titanium dioxide is between 10 and 20 nm.

2) Preparation of Functionalized Graphene Nanocomposite - Titanium Dioxide (GF @ TiO ₂ )

Binary nanocomposites containing by weight 95% of graphene (obtained from graphite) and 5% of nanoparticles of titanium dioxide (prepared from titanium tetrachloride in the presence of a surfactant): With stirring, an aqueous solution of a cationic or anionic surfactant and titanium dioxide nanoparticles are added to a solution of graphene in ethanol / water (50/50 v%). The mixture is placed in an ultrasound bath for 2 h, stirred vigorously for 1 h by a magnetic stirrer and placed in an autoclave and heated at 150 ° C for 3 h. Finally, the mixture is washed successively with ethanol and water. The functionalized graphene nanocomposite - titanium dioxide (GF @ TiO ₂ ) obtained is dried at 120 ° C.

4. Example of degradation of organic pollutants in water in the presence of graphite-based materials and graphene

The determination of degradation reaction kinetics as well as the influence of certain physicochemical parameters on this reaction is an important step for the design of such a photocatalyst and for possible applications at industrial scale. The study of the photocatalytic reaction kinetics of the dye (methylene blue, sodium Alzarine Sulfonate, Bromphenol, etc.) as a function of the initial concentration was carried out by varying the initial dye concentrations (3 - 35 mg / l). at initial pH. When the material (graphite oxide, graphene or functionalized graphene-TiO ₂ ) is added to the solution, the time required for the discoloration is a function of the initial concentration. In addition, the higher the initial concentration of the dye, the longer it takes to disappear. Photocatalysis with our materials, especially graphene and GF ^@ Ti0 ₂ , is therefore a very suitable method for the degradation of pollutants in a very low concentration of aqueous solution.

The degradation kinetics of the dyes (methylene blue, sodium alizarin sulphonate and bromophenol blue, etc.) are monitored using the analysis of samples taken over time by colorimetry. The maximum absorption wavelength of the dyes is 510 nm.

As an example, we present the results of the monitoring of the degradation of methylene blue, by photolysis (UV irradiation only), by GF (in the presence of UV irradiation, photocatalysis) and by GF in darkness (absence of irradiation UV). The results obtained show the effectiveness GF alone and in the absence of UV irradiation in the degradation of the dye. These show that irradiation with ultraviolet radiation is of no importance (Fiaure 1). Figure 1. Evaluation of the importance of irradiation with ultraviolet radiation during the degradation of organic pollutants

The study of degradation reaction kinetics, in the presence of the three graphite oxide materials, GF and GF @ TiO ₂ , of methylene blue as a function of the initial concentration was carried out. Figure 2 reports the kinetics of degradation of the dye as a function of time. The curves of the figures show that the dye, in the presence of the three materials, and in the absence of UV irradiation, is completely eliminated. The time required for total elimination varies according to the materials used.

Note that from a kinetic point of view the GF @ Ti0 ₂ nanocomposite is the most effective followed by GF and graphite oxide.

Figure 2. Kinetic study of the degradation of methylene blue in the presence of different materials (graphite oxide, functionalized graphene (GF) and functionalized graphene nanocomposite-titanium dioxide GF-TiO ₂ )

Figure 3 reports the degradation kinetics of methylene blue, sodium alzarin sulphonate and bromophenol blue, respectively, as a function of time in the presence of GF and nanocomposite GF @ Ti0 ₂ and in the absence of UV irradiation.

Figure 3. Kinetic study of the degradation of the different organic pollutants (BM: Methylene Blue, ASS: Alizarin Sodium Sulfonate and BBP: Bromo-Phenol Blue)

a) before degradation; b) after degradation

PH is an important factor in any degradation study. It can condition both the surface charge of the photocatalyst and the organic pollutant structure. This quantity characterizes the waters and its value will depend on the origin of the effluent. The treatment technique to be adopted will strongly depend on the pH value. This is why, in any degradation study, optimization of the ability to degrade organic pollutants as a function of pH is essential. In our study, we monitored the effect of pH on the degradation of organic pollutants at different initial concentrations of 3-35 mg / l. The acidification of the medium was carried out by adding a few drops of hydrochloric acid. Concentrated soda was used to have basic pHs. The results obtained (Example, case of the degradation of methylene blue (35 mg / l) in the presence of nanocomposite GF @ Ti0 ₂ are shown in FIG.

Figure 4. Influence of pH on the kinetics of degradation of methylene blue in the presence of nanocomposite GF @ Ti0 ₂

The curves in Figure 4 show a rapid decrease in the amount of the dye both in acidic and basic medium. We can therefore conclude that the molecular form has a better retention than the anionic form. This shows that the degradation of organic pollutants by our nanocomoposite materials is not influenced by the hydrophilic or hydrophobic nature of the organic compounds. In addition, under the same conditions we have been able to degrade other organic pollutants such as sodium alzarin sulfonate, bromophenol and organophosphorus pesticides such as fenitrothion, methidathion, malathion, methyl parathion, ethyl parathion).

Our materials have the advantage of being reusable after washing with methanol or water. Figure 5 shows that the catalytic activity of nanocomposite GF @ Ti0 ₂ remains virtually unchanged after 7 cycles.

Figure 5: Study of the reuse of nanocomposite GF @ Ti0 ₂ during the degradation of methylene blue

The characterization of the materials obtained was carried out through different techniques:

> Fourier Transform Infrared (FTIR);

> X-ray diffraction (XRD);

> Transmission electron microscope (TEM);

> Scanning Electron Microscope (SEM).

Characterization procedure

1. Fourier Transform Infrared (FTIR)

Fourier Transform Infrared Spectroscopy (FTIR) analysis was carried out in the range 400-4000 cm ^-1 , using a spectrometer "model FTLA2000-102" marketed by ABB Bomem. measuring device in ATR (Attenuated Total Reflexion) model Golden Gatte, with a diamond crystal model Specac.

The calibration of the FTIR is performed daily and automatically according to a procedure based on a water vapor absorption band in the ambient air. The contact pressure of the sample on the diamond crystal is controlled manually by means of a fastening system which makes it possible to optimize the contact and to have quality spectra. The scanning of the spectra is carried out between 260 and 4000 cm ^-1, a resolution of one point per 4 cm ^-1 is considered optimal for obtaining good spectrum quality in ATR mode.

Figure 6 illustrates the infrared absorption spectra of graphene and functionalized graphene. It shows the appearance of hydroxyl groups on the graphene surface after acid functionalization

Figure 6: Infrared spectra of graphene and functionalized graphene

2. X-ray diffraction (XRD)

X-ray diffraction is an analytical technique based on electron-matter interaction. The diffraction only takes place on the crystalline material. The identification of the crystalline phases by X-ray diffraction is made possible thanks to the periodicity of the atomic arrangement (structure) of the crystals which are unique from one phase to another. The identification of the phases present in a sample is made by comparing its spectrum (positions and intensities of the diffracted lines) with known phase spectra.

The X-ray diffraction spectra of graphite or graphene-based materials were recorded at room temperature using a Bruker AXS D-8 diffractometer using the K _{a line} of a copper anticathode (λ = 1.5405). Â) with Bragg-Brentano geometry (Θ-2Θ).

Figure 7: X-Ray Diffraction of Graphite, Graphite Oxide and Graphene

Figure 7 shows the XRD lines of graphite, graphite oxide and graphene. The high intensity graphite line at 2Θ = 26.1 ° indicates an interfacial spacing of 3.42 Å and characteristic of the plane (0 0 2 ). After oxidation, it is clear that the line has been replaced by a well-defined line in the weak theta areas, exactly at 2Θ = 10.8 °, which shows an intercalation between the graphene sheets. We can estimate this intercalation from 3.42 Å to 8.1 Å.

Oxidation made it possible to establish oxide bonds between the graphite layers, and consequently an increase in the interplanar spaces of the graphite is observed.

The reduction of graphite oxide leads to a total exfoliation of the graphite layers. This is proved by the disappearance of the characteristic lines of the graphite oxide and the appearance of the lines characteristic of the plane (0 0 2).

Figure 8: X-Ray Diffraction of Functionalized Graphene (GF) (a), Titanium Dioxide (TiO ₂ ) (b) and Functionalized Graphene Nanocomposite-Titanium Dioxide (GF-TiO ₂ ) (c)

X-ray diffraction figure 8 clearly shows that titanium dioxide is supported on graphene.

3. Scanning electron microscope

Scanning electron microscopy (SEM) provides microstructural characterization of materials that provides information on morphology, component distribution, crystallography, and composition.

The device used in this study is "Quanta 200" from FEI Company and can reach a resolution of 3.0 nm to 30 kV. It is a microscope that allows high-resolution observation under so-called environmental conditions (ESEM mode) with a gas pressure in the chamber of up to 26 mbar. The solid samples are glued on copper pestles through a sticky double-sided tape and then a thin layer of gold is deposited under vacuum. Figure 9 shows the SEM images of graphite oxide and graphene obtained after total exfoliation of graphite.

Figure 9: SEM micrograph of graphite oxide (a) and functionalized graphene (b) The examination of these images allows us to visualize the morphology and the distribution of its leaves as well as the topography of the surface. 4. Transmission electron microscopy (TEM)

The apparatus used in this work is FEI SIRION-200 Transmission Electron Microscopy. Figures 10 to 13 show the sizes of the nanoparticles of titanium dioxide alone or supported on the functionalized graphene, as well as the size of the graphene sheets.

Figure 10: MET micrograph of nanoparticles of titanium dioxide alone

Figure 11: MET Micrograph of Functionalized Graphene Alone

Figure 12: TEM micrograph of graphene nanocomposite graphite-titanium dioxide in the absence of surfactant

Figure 13: MET micrograph of graphene nanocomposite graphite-titanium dioxide in the absence of fonalisation

FIG. 14: TEM Micrograph of Functionalized Graphene Nanocomposite - Titanium Dioxide in the Presence of Surfactant

Claims

1 - Process for producing nanocomposite materials with potential photocatalytic activity to degrade organic pollutants Said nanocomposites consist of at least one nano-structured carbon material and / or a semiconductor metal oxide, according to the following steps:

at. Preparation of Graphite Oxide (GO) from commercial graphite via chemical oxidation;

b. The exfoliation of the GO mentioned in (a) using a special agitation mode, specifically sonication, and then subsequently a chemical reduction with at least one reducing agent (eg hydrazine hydrate);

vs. Functionalization of the exfoliated graphene obtained according to (b) via an attack with a mixture of acids containing at least two acids and preferably three types of acid and with a certain percentage well defined;

d. Controlling the growth of TiO ₂ nanoparticles by stabilizing them with at least one surfactant of anionic or cationic nature

e. Synthesis of functionalized graphene nanocomposite-titanium dioxide (GF @ TiO ₂ ) via the dispersion of preformed TiO ₂ nanoparticles, according to (d), on the surface of functionalized graphene in the presence or absence of anionic or cationic surfactant;

f. Degradation of organic coloring pollutants or pesticides in water in the absence and presence of UV irradiation and preferably in the absence of the UV source.

2. The process as claimed in claim 1, in which the semiconductor is titanium oxide which has a nano-scopic size supported on a carbon material based on graphite, graphene and / or functionalized graphene, so as to have a remarkable performance. on the photo-catalytic plane.

3. Process according to claim 1, characterized in that the nucleation and growth of the semiconductor oxide is carried out in a controllable manner on the surface of graphite, graphene or functionalized graphene in order to produce a nancomposite material homogeneous in size. , morphology and porosity.

4. Process according to any one of the preceding claims, characterized in that the percentage of the semiconductor between 3 to 50% by weight of the photo-catalyst nanocomposite and preferably in small amounts.

5. Process according to any one of claims 1 to 4, characterized in that the size of the semiconductor is of nanometric dimension included between 5 to 50 nm.

6. Photo-catalytic composition according to one of claims 1 to 4, characterized in that the semiconductor is crystallographically pure and in anatase form or equivalent. 7- Process according to claim 1, characterized by the use of graphite dioxide as a solid support for the degradation of organic pollutants.

8. Process according to claim 1, characterized by the use of graphene as a solid support for the degradation of organic pollutants.

9- Process according to claim 1, characterized by the use of graphene-semiconductor nanocomposites (eg titanium dioxide) as a solid photo-catalyst for the degradation of organic pollutants.

10- Process according to claim 1, characterized in that the solution to be treated is an industrial dye concentrations of 3 to 100 ppm.

11 - Process according to claim 1, characterized in that the reaction is carried out at atmospheric pressure and at a temperature between 18 and 30 ° C.

12- Process according to claim 1, characterized by the fact that these photocatalysts lead to a total mineralization of the organic pollutant.

13- Process according to claim 1, characterized by the fact that these photo-catalysts degrade other organic pollutants such as organophosphorus pesticides of concentrations of 3 to 100 ppm.

14- Process according to claim 1, characterized in that these photocatalysts are reusable several times.