CN101139130B - The preparation method of the Fenton's reagent that lasts for a long time and does not need hydrogen peroxide - Google Patents

Abstract

The invention discloses a preparation method of Fenton's reagent which lasts for a long time and does not need hydrogen peroxide. Fenton's reagent is a reagent with strong oxidizing ability formed by combining hydrogen peroxide and ferrous ions, but the use of hydrogen peroxide will greatly increase the cost of application. The invention utilizes semiconductor material cuprous oxide to generate a large amount of hydrogen peroxide under the irradiation of visible light, and utilizes the photogenerated H ₂ O ₂ and Fe ²⁺ to form Fenton's reagent. Under visible light irradiation, cuprous oxide is excited to generate electrons and holes. Since the conduction band position of Cu ₂ O is very negative, its electrons have a strong reducing ability, which can reduce the oxygen adsorbed on the surface of cuprous oxide to hydrogen peroxide. , together with Fe ²⁺ forms Fenton's reagent. The advantage of the Fenton's reagent is that the cuprous oxide as a photocatalyst is stable and can be used continuously for a long time, and hydrogen peroxide does not need to be used in the actual use process; the source of visible light is sufficient and cheap. Therefore, the cuprous oxide Fenton's reagent under visible light can completely replace the traditional Fenton's reagent in practical applications.

Description

The preparation method of the Fenton's reagent that lasts for a long time and does not need hydrogen peroxide

technical field

The present invention relates to photocatalytic oxidation technology, particularly a kind of preparation method of continuous and long-acting Fenton reagent without adding hydrogen peroxide. The method is to prepare Fenton reagent with cuprous oxide-ferrous ion system irradiated by visible light. It has a wide range of applications in the degradation of substances, sterilization, and algae killing.

Background technique

Photooxidation technology mainly uses strong oxidants to generate hydroxyl radicals (·OH) with strong oxidizing ability to completely mineralize organic pollutants or kill bacteria and algae, which belongs to advanced oxidation technology. The Fenton's reagent (H ₂ O ₂ +Fe ²⁺ ) composed of hydrogen peroxide (H ₂ O ₂ ) and Fe ²⁺ is one of the photooxidation techniques. Esplugas.S (Water Res.2002, 36(4), 1034) group research shows that in advanced oxidation technologies such as O ₃ , O ₃ /H ₂ O ₂ , UV, UV/O ₃ , UV/H ₂ O ₂ , In the process of degrading phenol by O ₃ /UV/H ₂ O ₂ and electrochemical process, Fent on reagent is the fastest. In addition to wastewater treatment, it can also be used for waste residue, sedimentation, soil purification, dehydration of biologically active sludge, etc., and can also be used for chemical preparation. However, H ₂ O ₂ is expensive, and during the reaction process, the intermediate product will undergo self-consumption reaction with hydroxyl radicals, which eventually leads to low utilization rate of H ₂ O ₂ and needs to be replenished quickly, which will quickly increase the cost of use . Although, people also try to combine the Fenton reagent with ultraviolet (UV), but it still needs to add H ₂ O ₂ to make the photo-Fenton reaction, and the use of ultraviolet light increases the equipment cost on the one hand, on the other hand due to the UV light radiation It may also affect human health. Therefore, replacing UV light with visible light or sunlight will be more in line with future development trends.

Heterogeneous photocatalysis is a process that converts light into chemical energy. Among them, TiO ₂ is a photocatalyst that has been studied the most, but it can only work under UV light. Although people have used methods such as doping, compounding, and transplanting metals to make it absorb light wavelengths red-shifted, the final effect is not satisfactory. not so obvious. The semiconductor cuprous oxide (Cu ₂ O) has a direct bandgap of about 2.0eV and can completely generate electrons and holes under the radiation of visible light. It has important applications in hydrogen production, superconductivity, solar cells and electrode materials. It has also been used for visible light degradation of organic pollutants (Appl. Cata. A: Gen. 2006, 299, 292). It has been reported that Cu ⁺ is deposited on the surface of zeolite to decompose NOx into N ₂ and O ₂ under visible light irradiation (Appl.Surf.Sci.2001, 174, 177). In the research of heterogeneous photocatalysis of Cu ₂ O, we found that as a semiconductor material, the valence band potential and conduction band potential of Cu ₂ O are very different from those of titanium dioxide. We believe that its working principle must be very different from that of titanium dioxide. This also prompted us to further think about the combination of photocatalytic technology and photooxidation technology, and make full use of visible light, especially sunlight, to realize the practical application of photocatalytic oxidation of Cu ₂ O.

Contents of the invention

The present invention utilizes the very negative conduction band potential of Cu ₂ O, which leads to the strong reducibility of conduction band electrons, and oxidizes the oxygen adsorbed on the surface to H ₂ O ₂ in the presence of visible light, and forms Fenton’s reagent together with Fe ²⁺ , It is used to degrade organic pollutants that are difficult to degrade by general methods, and to kill bacteria and algae.

Principle of the present invention is:

Semiconductor photocatalysis is completed by the combined action of photo-excited free electrons and holes. Effective separation of electrons and holes, thereby reducing their recombination is an important way to improve photon quantum efficiency. Cu ₂ O is one of the semiconductors with the most negative conduction band potential known so far, which is -1.4V and the energy band gap is 2.0eV. Cu ₂ O has a strong ability to absorb oxygen, and they exist in the state of O ^- or O ₂ ^- (J.Catal.1969, 15, 355; J.Phys.Chem.B 1933, 197; Electrochem.Commun. 2004, 6, 940), these two factors determine that Cu ₂ O has a strong oxygen reduction ability, or photo-oxygen cathode activity. Under visible light irradiation, electrons transition from the valence band of Cu ₂ O to the conduction band, and the holes left in the valence band recombine with the weakly reducing hole sacrificial agent, leaving the electrons in the conduction band to participate in the surface of Cu ₂ O reduction reaction. When the size of Cu ₂ O is smaller, the specific surface area is larger, the amount of oxygen adsorbed on the surface is larger, and the amount of hydrogen peroxide produced by participating in the reduction reaction is larger. When there are ferrous ions in the system, the chain oxidation reaction that produces hydroxyl radicals begins to take place. Concrete processes of generating hydrogen peroxide and hydroxyl radicals are shown in the following simplified formulas (1) and (2) respectively:

The scheme that realizes the object of the present invention is:

The preparation method of cuprous oxide or cuprous oxide composite Fenton reagent under visible light irradiation is to absorb photons in a certain wavelength range in visible light through cuprous oxide of suitable size or cuprous oxide of suitable size and other material composites, and its valence band The electrons in the cuprous oxide jump to the conduction band, because the conduction band potential of cuprous oxide is very negative, and the reducing ability of electrons is very strong, which can reduce the oxygen adsorbed on the surface of cuprous oxide to hydrogen peroxide in the presence of water molecules; at a certain concentration In the presence of a hole sacrificial agent and at a certain pH value, the hydrogen peroxide and a certain concentration of ferrous ions form a Fenton reagent. The Fenton's reagent is long-lasting and does not require additional H ₂ O ₂ .

The specific method is:

A preparation method of Fenton's reagent that lasts for a long time without hydrogen peroxide, and is characterized in that the preparation method does not add hydrogen peroxide, adopts the _Cu2O -Fe2 ⁺ _-O2 system under visible light irradiation, and utilizes visible light to irradiate cuprous oxide Or react hydrogen peroxide generated by the cuprous oxide complex with ferrous ions to prepare Fenton's reagent, add a hole sacrificial agent to the reaction system, the addition amount is 0-100 g/L, and the pH of the system is 3-10.

The visible light is composed of light with a wavelength of 400-800nm, and the visible light includes sunlight and light emitted by lamps for daily lighting. The lighting lamps include lamps, bulbs, industrial halogen lamps, xenon lamps and light-emitting diodes.

The method for preparing the above-mentioned Fenton reagent, the cuprous oxide as a visible light catalyst is an amorphous structure of granular, whisker-like, rod-like, linear, ribbon-like, disk-like, sheet-like, flower-like, empty sphere or cubic shape, Or crystalline structure, or cuprous oxide with both amorphous and crystalline structures, the size range of the cuprous oxide is 3nm-10cm, preferably at least one-dimensional nanomaterials with a particle size between 3nm-100nm.

The method for preparing the above-mentioned Fenton reagent, the cuprous oxide complex as a visible light catalyst includes a compound that can be combined with cuprous oxide in any proportion by all physical or chemical methods, wherein cuprous oxide is at least one-dimensional particle size in Nanomaterials between 3nm-100nm.

The ferrous ion required in the preparation method of above-mentioned Fenton's reagent, owing to be used in neutral or acidic medium, described ferrous ion can be in the ferrous ion in complex or chelated state compound, or be in Ferrous ions in covalent compound iron phthalocyanine, iron porphyrin, iron gallate or iron catechol, or ferrous ions immobilized by adsorption or ion exchange, or ferric ions added to the system Instead of ferrous ions, and then converted into ferrous iron under photochemical reaction, the materials used for the immobilization of ferrous ions include silicon oxide, iron oxide, Nafion film, chitosan, various soils and natural minerals, ferrous ions The concentration range is 1×10 ^-5 -100 g/L.

The ferrous ion in the preparation method of above-mentioned Fenton's reagent can replace with transition metal Ag(I), Ce(III), Co(II), Mn(II), Ni(II), Ru(III) and V(III), The ion concentration range is 1×10 ^-5 -100 g/L.

In the preparation method of the above-mentioned Fenton reagent, the hole sacrificial agent substances include organic and inorganic reducing agents, organic substances such as alcohols, acids, aldehydes, glucose, ethylenediaminetetraacetic acid (EDTA), inorganic substances such as Fe ²⁺ , Soluble sulfides, sulfites.

Description of drawings

Fig.1 The trend of hydrogen peroxide precipitation of Cu ₂ O/multi-walled carbon nanotube composites under visible light irradiation in the presence of Fe ²⁺ and sodium formate

Figure 2 Cu ₂ O/multi-walled carbon nanotube composite-Fe ²⁺ -sodium formate-salicylic acid system, the concentration of 2,3-dihydroxybenzoic acid changes with time under visible light irradiation

The comparison of two kinds of Fenton's reagent degradation dye reactive brilliant red effects of Fig. 3

In Fig. 3, A is the traditional Fenton's reagent (4 mmol/L H ₂ O ₂ +10 mmol/L Fe ²⁺ -EDTA), and B is the Cu ₂ O/multi-walled carbon nanotube described in the present invention The composite is Fenton's reagent of photocatalyst (visible light + 1 g/L nano-sized Cu ₂ O/multi-walled carbon nanotube composite + 10 mmol/L Fe ²⁺ -EDTA).

Detailed ways

Example 1

Precipitation of Hydrogen Peroxide from Cu ₂ O/Multi-walled Carbon Nanotube Composite-Fe ²⁺ -Sodium Formate System Irradiated by Xenon Lamp

The composite (3nm-2000nm) of Cu ₂ O and multi-walled carbon nanotubes prepared by electrochemical method is used as photocatalyst, under the irradiation of 300W xenon lamp and Fe ²⁺ (10 mmol/L), sodium formate (1 mmol/L) exists, the hydrogen peroxide trend that the system separates out in neutral (pH=7) environment is as shown in Figure 1. It can be seen from the figure that the precipitation of H ₂ O ₂ is a gradual process. In the first 100 minutes, H ₂ O ₂ precipitated at a constant rate, and then the precipitation rate gradually decreased. After 180 minutes, the precipitation of H ₂ O ₂ The concentration is basically stable and remains unchanged. It can be seen that the precipitation of H ₂ O ₂ in this system is a constant process, and the amount of H ₂ O ₂ will not decrease due to the loss of the reaction. Compared with the traditional Fenton's reagent, there is no need to replenish the consumed H ₂ O ₂ .

Example 2

2,3-dihydroxybenzoic acid concentration change test of Cu ₂ O/multi-walled carbon nanotube composite (preparation in Example 1)-Fe ²⁺ -sodium formate-salicylic acid system under visible light irradiation.

According to bibliographical reports (EFEBS Lett.1978,92,321) free hydroxyl radical can oxidize salicylic acid into 2,3-dihydroxybenzoic acid, so determine 2,3-dihydroxybenzoic acid by colorimetric method Concentration The concentration of hydroxyl radicals can be indirectly measured semi-quantitatively. Figure 2 shows the changes in the concentration of 2,3-dihydroxybenzoic acid measured under visible light irradiation in the presence of Cu ₂ O/multi-walled carbon nanotube composites, Fe ²⁺ , sodium formate, and salicylic acid trend. It is obvious that at the beginning, the concentration of 2,3-dihydroxybenzoic acid rises rapidly with the increase of irradiation time, which indirectly shows that a large number of hydroxyl radicals are generated in the above-mentioned Fenton reagent system. With the further increase of time, the concentration of 2,3-dihydroxybenzoic acid decreases, because the precipitated hydroxyl radicals are highly oxidizing, and can attack 2,3-dihydroxybenzoic acid to degrade it, which also indirectly proves that A large number of hydroxyl radicals are continuously produced in the system.

Example 3

Cu ₂ O/multi-walled carbon nanotube composite (preparation of embodiment 1) Fenton's reagent and traditional Fenton's reagent degradation dye reactive brilliant red comparative test

The Cu ₂ O/multi-walled carbon nanotube composite Fenton reagent and the traditional Fenton reagent were used to degrade the dye reactive brilliant red, and the comparison results are shown in FIG. 3 . In Fig. 3, A is the traditional Fenton's reagent (4 mmol/L H ₂ O ₂ +10 mmol/L Fe ²⁺ -EDTA), and B is the Cu ₂ O/multi-walled carbon nanotube described in the present invention The composite is Fenton's reagent of photocatalyst (visible light + 1 g/L nano-sized Cu ₂ O/multi-walled carbon nanotube composite + 10 mmol/L Fe ²⁺ -EDTA).

It can be seen from the figure that in the early stage of the reaction, the degradation dye of the traditional Fenton reagent leads to a good decolorization effect, but after 30 minutes, due to the consumption of hydrogen peroxide, the decolorization effect even tends to decline at a certain level. For the Cu ₂ O/multi-walled carbon nanotube composite Fenton’s reagent, although the decolorization effect of the dye was poor due to the low concentration of hydrogen peroxide at the initial stage of the reaction, as time went on, the decolorization rate increased rapidly after 50 minutes, and exceeded 80 minutes. The decolorization effect of traditional Fenton's reagent, and further decolorization of the dye over time. It shows that there is continuous hydrogen peroxide precipitation in the system, so this new Fenton reagent is also more durable and long-acting.

Example 4

Precipitation of Hydrogen Peroxide in Cu ₂ O Flower-like Super Nanostructure-Fe ²⁺ -EDTA System

With Cu ₂ O flower-like super nanostructure prepared by chemical deposition method as photocatalyst (3nm-10cm), in the irradiation of 300W halogen lamp and have Fe ²⁺ (20 mmol/liter), EDTA (5 mmol/ liter) in the presence of hydrogen peroxide in the weakly acidic (pH=6) environment is similar to that shown in Figure 1. The precipitation of H ₂ O ₂ is also a gradual process. In the first 90 minutes, H ₂ O ₂ precipitated at a constant rate, and then, the precipitation rate gradually decreased. After 200 minutes, the concentration of H ₂ O ₂ was basically stable. constant. It can be seen that the precipitation of H ₂ O ₂ in this system is also a constant process, and the amount of H ₂ O ₂ will not decrease due to the loss of the reaction, and the reaction process does not need to supplement H ₂ O ₂ .

Example 5

Comparison of the effect of the Fenton reagent system of Cu ₂ O nanoparticles-Fe ²⁺ -Na ₂ S (hole sacrificial agent) and the system of only Cu ₂ O nanoparticles in degrading dye reactive brilliant red

Fent on reagent system of Cu ₂ O nanoparticles (3nm-100nm)-Fe ²⁺ -Na ₂ S (visible light + 1 g/L nano-sized Cu ₂ O + 30 mmol/L Fe ²⁺ -Na ₂ S) The trend of degradation dye reactive brilliant red (500 ml, 100 mg/L solution) is similar to Cu ₂ O/multi-walled carbon nanotube composite Fenton reagent system, although the decolorization effect of the dye is poor due to the low concentration of hydrogen peroxide at the initial stage of the reaction, but As time goes by, after 60 minutes, the decolorization rate increases rapidly, surpasses the decolorization effect of traditional Fenton reagent in 100 minutes, and further decolorizes the dye as time goes by, and the final decolorization rate can reach 95%. It shows that there is continuous hydrogen peroxide precipitation in the system. For the Cu ₂ O nanoparticle system with only 1 g/L, Reactive Brilliant Red had a 20% decolorization rate in the first 30 minutes, and there was no further degradation of the dye as the irradiation proceeded. Therefore, the semiconductor Cu ₂ O alone cannot produce hydrogen peroxide, nor can it effectively degrade organic pollutants, because the holes generated by Cu ₂ O excited by light are not oxidizable enough, and the utilization rate of electrons generated is not high.

Claims (8)

1. continue the preparation method of long lasting Fenton reagent, it is characterized in that, this preparation method does not add hydrogen peroxide, adopts the Cu under the radiation of visible light ₂O-Fe ²⁺-O ₂System, the hydrogen peroxide and the ferrous ion prepared in reaction Fenton reagent that utilize radiation of visible light Red copper oxide or Red copper oxide mixture to generate add the hole sacrifice agent in the reaction system, and add-on is and 1 * 10 ^-5Concentration-100 grams per liter of ferrous ion concentration correspondence, system pH is 3-10.

2. the preparation method who continues long lasting Fenton reagent as claimed in claim 1, it is characterized in that, described visible light is made up of 400～800nm wavelength light, its visible light comprises the light that sunlight, normal lighting send with light fixture, and described lighting comprises fluorescent tube, bulb, industrial halogen lamp, xenon lamp and photodiode.

3. the preparation method who continues long lasting Fenton reagent as claimed in claim 1, it is characterized in that described Red copper oxide is amorphous structure or the crystalline texture or the amorphous and simultaneous Red copper oxide of crystalline texture of particulate state, whisker shape, bar-shaped, wire, band shape, disc-shaped, sheet, flower-shaped, empty ball or cubes pattern.

4. the preparation method who continues long lasting Fenton reagent as claimed in claim 3 is characterized in that described Red copper oxide size range is 3nm-10cm, has the nano material of one dimension granularity between 3nm-100nm at least.

5. the preparation method who continues long lasting Fenton reagent as claimed in claim 1, it is characterized in that, described Red copper oxide mixture comprises the mixture that can be combined with each other and form by physics or chemical process in any ratio with Red copper oxide, and wherein Red copper oxide is to have the nano material of one dimension granularity between 3nm-100nm at least.

6. the preparation method who continues long lasting Fenton reagent as claimed in claim 1, it is characterized in that, described ferrous ion is the ferrous ion that is in complexing or the chelating attitude compound, or be in the blue or green iron of covalent compound phthalein, ferrous porphyrin, ferrous ion in gallic acid iron or the pyrocatechol iron, or be adsorbed or the immobilized ferrous ion of ion-exchange, or adding ferric ion in system replaces ferrous ion, under photochemical reaction, change into ferrous iron then, be used for the immobilized material of ferrous ion and comprise silicon oxide, ferric oxide, the Nafion film, chitosan, various soil and natural mineral, ferrous ion concentration scope are 1 * 10 ^-5-100 grams per liters.

7. the preparation method who continues long lasting Fenton reagent as claimed in claim 1, it is characterized in that, described ferrous ion or replace with Transition Metal Ag (I), Ce (III), Co (II), Mn (II), Ni (II), Ru (III) or V (III), described ionic concn scope is 1 * 10 ^-5-100 grams per liters.

8. the reagent method that continues long lasting Fenton reagent as claimed in claim 1, it is characterized in that, described hole sacrifice agent material comprises organic, inorganic reducing agent, and the organism reductive agent comprises alcohol, acid, aldehydes, glucose, ethylenediamine tetraacetic acid (EDTA), and the inorganics reductive agent comprises Fe ²⁺, dissolvable sulfide, sulphite.

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