Material for detecting phenol derivatives and applications thereof

Abstract

Monolithic nanoporous material, which is self-standing (i.e. self-supported or cohesive), solid and transparent, essentially devoid of cracks, transparent to UV radiation, obtained by the Sol-Gel process, the material having a basic nature and including a reagent capable of generating a stained product by forming a bond with phenol, a basic compound or mixture of basic compounds and a compound or mixture of oxidant compounds, method for preparation and use in the detection and in the selective depollution of phenol or one of its derivatives.

Claims

1. A monolithic nanoporous material, which is self-standing (i.e. self-supported or cohesive), solid and transparent, essentially devoid of cracks, transparent to UV radiation, and obtained by the Sol-Gel process, said material having a basic nature and comprising: a reagent capable of generating a stained product by forming a bond with phenol or a phenol derivative, a basic compound or mixture of basic compounds, and an oxidant compound or mixture of oxidant compounds, wherein the ratio by weight of the reagent capable of generating a stained product by forming a bond with phenol or a phenol derivative: the oxidant compound or mixture of oxidant compounds is 15:1 to 1:3.

2. The monolithic nanoporous material according to claim 1, wherein the reagent capable of generating a stained product is 4-aminoantipyrine (AAP) or a derivative of AAP having formula I ##STR00002## wherein: R1 is an alkyl radical containing 1 to 30 carbon atoms, linear or branched, or an aryl radical; R2 is a phenyl or para-aminophenyl radical; and R3 is an alkyl radical containing 1 to 30 carbon atoms, linear or branched.

3. The monolithic nanoporous material according to claim 1, wherein the oxidant compound or oxidant compounds are chosen in the group consisting of potassium persulphate, potassium peroxomonosulphate, hydrogen peroxide and potassium hexacyanoferrate.

4. The monolithic nanoporous material according to claim 1, wherein the basic compound or mixture of basic compounds are chosen in the group consisting of a borate, phosphate, 2-amino-2-(hydroxymethyl)-1,3-propanediol, carbonate, glycine-sodium hydroxide, or sodium hydroxide buffer.

5. The monolithic nanoporous material according to claim 1, wherein the reagent capable of generating a stained product by forming a bond with phenol or a phenol derivative is AAP, the basic compound or mixture of basic compounds is chosen among borate ions and sodium hydroxide, and the oxidant compound or oxidant compounds are selected from the group consisting of potassium hexacyanoferrate, potassium persulphate, potassium peroxomonosulphate, hydrogen peroxide, and a mixture of potassium hexacyanoferrate and one or a plurality of further oxidant compounds.

6. The monolithic nanoporous material according to claim 1, containing by weight 25% to 0.005% of probe molecule, 5% to 0.05% of basic compound or mixture of basic compounds, and 15% to 0.01% of oxidant compound or mixture of oxidant compounds.

7. The monolithic nanoporous material according to claim 1, containing by weight 50% to 0.05% of probe molecule, 5% to 0.05% of basic compound or mixture of basic compounds, and 25% to 0.01% of oxidant compound or mixture of oxidant compounds.

8. The monolithic nanoporous material according to claim 1, wherein the reagent capable of generating a stained product is 4-aminoantipyrine (AAP) or a derivative of AAP having formula I ##STR00003## wherein: R1 is an alkyl radical containing 1 to 30 carbon atoms, linear or branched, or an aryl radical; R2 is a phenyl or para-aminophenyl radical; and R3 is a substituted phenyl of an alkyl radical containing 1 to 30 carbon atoms, linear or branched.

9. The monolithic nanoporous material according to claim 1, wherein the ratio by weight of the reagent capable of generating a stained product by forming a bond with phenol or a phenol derivative: the oxidant compound or mixture of oxidant compounds is 10:1 to 1:3.

10. A monolithic nanoporous material according to claim 1, wherein the ratio by weight of the reagent capable of generating a stained product by forming a bond with phenol or a phenol derivative: the oxidant compound or mixture of oxidant compounds is 5:1 to 1:2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The file of this patent contains at least one drawing executed in color. Copies of this patent with color drawings will be provided by the Patent and Trademark Office upon request and payment of the necessary fee.

(2) The examples which follow illustrate the present application.

(3) The invention will be understood more clearly if reference is made to the appended drawings wherein

(4) FIG. 1 represents a top view photograph of a block of material from example 1 placed on a ruler. FIG. 2 represents the progression of the absorption spectra of experiment 1 for a matrix of example 1.

(5) FIG. 2A represents the progression of the absorption spectra of experiment 1 for a matrix of example 1A.

(6) FIG. 3 represents the progression of the absorbance over time at 510 nm in experiment 1 for a matrix of example 1.

(7) FIG. 3A represents the progression of the absorbance over time at 510 nm in experiment 1 for a matrix of example 1A

(8) FIG. 4 represents a photograph of a block of material from example 1 after exposure to phenol.

(9) FIG. 5 represents a calibration curve for the detection/assay of phenol.

(10) FIG. 6 represents photographs of blocks of material from example 1 after exposure to various phenol derivatives.

(11) FIG. 7 represents a calibration curve for the detection of phenol, in aqueous solution.

DETAILED DESCRIPTION OF THE INVENTION

Example 1: Preparation of a Sol Gel Matrix

(12) In 11.74 mL of methanol stirred and cooled to approximately 25 C., 300 L of 0.1 M AAP is added. 10.74 mL of tetramethyl-orthosilicate is then added, followed by 0.528 mL of aminopropyl-triethoxysilane. 300 L of 0.1 M potassium hexacyanoferrate and 6.396 mL of 0.05 M borate buffer solution at pH 9 are then added.

(13) The sol is removed to pour it into moulds which are sealed hermetically for 48 hours, and the solvents are progressively evaporated in a nitrogen atmosphere.

Example 1A: Preparation of a Sol Gel Matrix (with Another Formulation)

(14) In 6.926 mL methanol stirred and cooled to approximately 25 C., 300 L of 0.1 M AAP is added. 6.447 mL of tetramethyl-orthosilicate is then added, followed by 0.252 mL of (3-chloropropyl)trimethoxysilane. 300 L of 0.1 M potassium hexacyanoferrate, 9.776 mL of H.sub.2O and 6.0 mL of 0.05 M borate buffer solution at pH 9 are the added.

(15) The sol is removed to pour it into moulds which are sealed hermetically for 48 hours, and the solvents are progressively evaporated in a nitrogen atmosphere.

(16) For the matrices of Examples 1 and 1A, various shapes were obtained according to the mould used. The following moulds were used: a. Parallelepipedic moulds having the dimensions 2*10*20, in mm. b. Parallelepipedic moulds having the dimensions 4*10*50 in mm.

(17) They were filled with a volume of approximately 400 L for type a moulds and 1 mL for type b moulds.

(18) The materials according to the invention obtained are sol gel matrices. They are transparent and free from cracks. Protected from light, they can be stored for several months.

(19) FIG. 1 is a photograph of a material according to the invention placed on a ruler. The matrix measures in this case approximately 5 mm wide by 8.2 millimeters long. The thickness thereof is approximately 1 millimeter.

Experiment 1: Exposure of a Matrix to a Gas Stream Containing Phenol

(20) The function of the materials according to the invention is based on a chemical reaction taking place in the matrix which generates an optically detectable signal. Tracking this optical signal over time makes it possible to determine the reaction rate, which can then be correlated with the concentration of gaseous compound under test by means of a calibration curve. The optical detection is rapid and feasible in situ in a single step.

(21) A Sol-Gel matrix, according to example 1 or example 1A, prepared using a type a mould is exposed to a continuous gas stream of 500 mL/min containing a fixed concentration of 100 ppb of phenol in 50% relative humidity. The gaseous phenol is generated using a permeation oven, and then diluted with air to the concentration sought, and conveyed to the input of a measurement cell housing the Sol-Gel matrix using a tube approximately 3 mm in diameter, and having a gas input and output suitable for such tubes, along with an optical input and output for connecting the optical fibres. To limit interfering light, the cell is embodied in such a way that the ambient light does not enter the cell.

(22) During exposure, the pollutant circulates in the cell while a deuterium-halogen source (Ocean Optics, DH-2000-BAL) illuminates the matrix via the optical input and absorption spectra are recorded by a UV-Visible spectrophotometer (Ocean Optics, QE65000). Tracking of the variation of the absorbance over the exposure time makes it possible to observe the appearance of a characteristic peak at 510 nm of the reaction product between phenol and the reagent capable of generating a stained product by forming a bond with phenol incorporated in the material according to the invention.

(23) The intensity of this peak increases in the course of the exposure. The spectra are recorded in FIG. 2 for the matrix of example 1 and in FIG. 2A for the matrix of example 1A and the progression of the absorbance over time at 510 nm in FIG. 3 for the matrix of example 1 and in FIG. 3A for the matrix of example 1A. The photo of a matrix after exposure is shown in FIG. 4.

(24) The progression of the spectra (FIGS. 2 and 2A) demonstrates that the absorbance of the material increases in the presence of phenol. The slope at 510 nm (FIGS. 3 and 3A) shows that the increase in absorbance can be correlated at a given wavelength with the interaction of a certain concentration of phenol with the material. The comparison of the photo in FIG. 4 and the photo in FIG. 1 shows that the increase in absorbance is visible to the naked eye.

Experiment 2: Calibration Curve of Phenol

(25) The same method as in experiment 3 is repeated for different phenol concentrations at a flow rate of 500 mL/min. The rate of formation of the reaction product between phenol and the matrix doped with probe molecules is dependent on the phenol concentration contained in the gas stream. As such, plotting the value of the slopes as a function of the concentration gives the calibration curve for phenol detection; such a calibration curve is represented in FIG. 5. The results obtained demonstrate that it is possible to measure the concentration of phenol in a gas mixture using a sol gel matrix according to the invention.

Experiment 3: Application of the Method to Other Phenol Derivatives

(26) The procedure as described in experiment 1 was followed, but using various phenol derivatives, i.e. 4-methoxyphenol, 2-nitrophenol, 2,4-dichlorophenol, and naphthol. The results obtained are shown in FIG. 6.

(27) The phenol derivatives can also be detected equally well, but the maximum absorption wavelength differs slightly from that observed for phenol.

(28) Consequently, the colour of the matrix after exposure is also different, as shown by the comparison of FIG. 1 and FIG. 6. As such, the detection can be qualitative (which is possible with the naked eye) or quantitative (by making a measurement by absorbance or reflectance for example).

Experiment 4: Calibration of Detection of Phenol in Aqueous Solution with a Sol-Gel Matrix

(29) A Sol-Gel matrix according to example 1 was placed in an aqueous phenol solution at a known concentration. The progression of the absorbance of the solution over time was monitored at 506 nm using a UV-Vis spectrophotometer. This method was repeated for different phenol concentrations. The rate of reaction between the probe molecules of the matrix and phenol is dependent on the phenol concentration. The plot of the value of the slopes as a function of the concentration constitutes the calibration curve for the detection of phenol; the result obtained is represented in FIG. 7. The results obtained demonstrate that it is possible to measure the concentration of phenol in an aqueous solution using a sol gel matrix according to the invention.

(30) Comparative Experiment:

(31) When phenol is added last for the reaction in aqueous solution, in the presence of a significant excess of potassium hexacyanoferrate, the change of colour does not OMIT.

(32) Even slightly below the typical ratio described in the literature, i.e. with a ratio of [AAP]:[potassium hexacyanoferrate]=1:5, the change of colour is not significant.

(33) The change of colour with the addition of phenol last becomes significant only by modifying the ratio used in the reference method. The reaction works properly when phenol is added last if the different constituents are used under the conditions indicated above in the description. Notably the use either of a slight excess of oxidant compounds such as potassium hexacyanoferrate, an excess of reagent capable of generating a stained product by forming a bond with phenol, or an equivalent quantity of reagent capable of generating a stained product by forming a bond with phenol and oxidant compounds and the relationship between these ratios and the possibility of adding phenol as the final reagent, had never been envisaged.

(34) As such in conclusion, the colorimetric method according to the present invention provides a certain number of innovations including the addition of phenol last (essential for performing detection using a matrix incorporating all the reagents in advance), the incorporation of basic components, the incorporation of an oxidant in the same matrix which can be stored for over 6 months, and in some cases an original ratio of [stained reagent]/[oxidant].