RU2347611C1 - Catalyst and heterogeneous photocatalystic fenton process for sewage water treatment - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: present invention is an efficient heterogeneous photocatalytic Fenton system for neutralisation of organic impurities in sewage water using heterogeneous catalysts, based on powdered or textured perovskite at room temperature and atmospheric pressure. The system is used for decomposing acetic acid, methyl-tert-butyl-ether (MTBE), methanol, ethanol, their mixtures and wine production wastes. Organic substances are removed through oxidation to gaseous CO₂. The effect of H₂O₂ concentration and pH is established. Further increase in efficiency of treatment is achieved through dosed supply of H₂O₂. The heterogeneous photocatalytic Fenton system allows for widening the operating pH range (2-8) compared to a homogeneous system (pH 2-4) without precipitation.

EFFECT: increased efficiency of treatment and widening of the operating range.

15 cl, 10 ex, 4 tbl, 5 dwg

Description

The invention relates to wastewater treatment processes using a Fenton photocatalytic system. Photocatalytic decomposition of organic pollutants using the Fenton photocatalytic system can be more effective when the process is carried out in a heterogeneous mode and becomes important for modern oxidative technologies (COT).

Fenton's homogeneous photocatalytic system (H ₂ O ₂ + Fe + hν) has been extensively studied and described in the literature as a promising method for wastewater treatment (Hislop, K. and Bolton, J. (1999). Environ. Sci. Technol., 33, 3119 -3126; Trapido, M., Kallas, J. (2000). Environ. Technol. 21, 799-808; Vicente, J., Rosal, R. and Diaz, M. (2002). Ind. Eng. Chem. Res., 41, 46-51; Kavitha, V., Palanivelu, K. (2004). Chemosphere 55, 1235-1243). The main disadvantage of such a system is the need for reactions in an acidic medium (pH <3) and the difficulty of separating the precipitate containing Fe ions after treatment.

A good alternative to Fenton's homogeneous photocatalytic system can be heterogeneous photocatalysis. The effectiveness of the systems is compared by measuring the decomposition of acetic acid under different experimental conditions. Studies of heterogeneous Fenton photocatalytic systems, in particular Fe on zeolite HY, for the decomposition of polyvinyl alcohol (Bossmann, SH, Oliveros, E., Gob, S., Kantor, M., Goppert, A., You, L., Yue, PL, Braun, AM (2001), Water Sci. Technol. 44 (5), 257.262). Studies of Nafion membranes with fixed Fe ions as photocatalysts for the decomposition of organic impurities have also been reported (Maletzky, P .; Bauer, R .; Lahnsteiner, J .; Pouresmael, B. (1999) Chemosphere, 38 (10), 2315-2325; Sabhi and Kiwi (2001). Water Research 35 (8), 1994-2001); clay, bentonite and laponite with fixed Fe ions for neutralizing the azo dye Orange II (Feng, J .; Hu, X .; Yue, P. L. (2005). Water Research 39, 89.96).

The closest is the use of Nafion membranes with fixed Fe ions as photocatalysts for the decomposition of organic impurities (Maletzky, P .; Bauer, R .; Lahnsteiner, J .; Pouresmael, B. (1999) Chemosphere, 38 (10), 2315-2325; Sabhi and Kiwi (2001). Water Research 35 (8), 1994-2001).

The disadvantage is the instability of the catalyst in acidic environments and a low degree of conversion.

The invention is directed to the development of a heterogeneous Fenton photocatalytic process for wastewater treatment using environmentally friendly catalysts with high stability and a high degree of conversion.

Another object of the invention is to provide a more complete decomposition of impurities in a heterogeneous photocatalytic system compared to a Fenton homogeneous photocatalytic system, as well as to ensure controllability of decomposition based on an analysis of the composition of the gas released during photooxidation.

Finally, the invention allows the regeneration of the catalyst at a low cost without the formation of precipitation.

The essence of the invention is the use of a stable heterogeneous perovskite-containing Fenton photocatalyst for the decomposition of harmful industrial emissions, including the decomposition of biodegradable organic compounds.

The problem is solved by two options for the composition of the catalyst.

According to the first option.

The catalyst for the Fenton heterogeneous photocatalytic process for wastewater treatment, including biodegradable organic compounds, is a powder or monolith containing perovskite LnFeO ₃ , where Ln = La, Ce, Pr, Nd, Sm, and a structure-forming additive or binder.

The perovskite content in the catalyst is 2.0-90.0 wt.%, The rest is a structure-forming additive (binder), in which it contains aluminum oxide (Al ₂ O ₃ ).

The perovskite content is preferably 45.0-90.0 wt.%, Best of all 48.0-88.0 wt.%.

A massive catalyst in the form of a powder or a monolith is prepared by mixing.

According to the second option.

The catalyst for the Fenton heterogeneous photocatalytic process for wastewater treatment, including biodegradable organic compounds, is perovskite LaMeO ₃ , or Pt / LaMeO ₃ , where Me = Mn, Co, Fe, Ni, Cu, supported on a structured support, for example cordierite in the form of honeycomb blocks, alumina-based foam or silicon carbide (SiC).

The perovskite content in the supported catalyst is 2.0-30.0 wt.%, Preferably 3.0-10.0 wt.%, Most preferably 4.0 wt.%.

The platinum content in the supported catalyst is 0.05-10.0 wt.%, Preferably 0.05-3.0 wt.% And most preferably 0.1 wt.%.

The supported catalysts are prepared by applying perovskite LaMeO ₃ or Pt / LaMeO ₃ onto a structured support, for example cordierite in the form of honeycomb blocks, foam based on alumina or SiC.

The noble metal (Pt) is applied by impregnation from a solution of platinum chloride salt on a cordierite substrate, either pure or with pre-applied perovskite. After platinum was applied, the samples were either dried in air or subjected to hydrazine hydrate treatment before drying.

Fenton's structured photocatalysts for oxidation have not been investigated.

The use of perovskites for Fenton photooxidation has not been studied.

A brief description of the drawings.

Figure 1 is a diagram of a single-pass reactor for photocatalytic oxidation of Fenton.

Pollution neutralization is achieved in one pass of the neutralized water and the catalyst crushed to powder through the region of the reactor irradiated with light. The contaminated water through the flow sensor enters the photoreactor, then the catalyst is separated and again enters the reactor, and the purified water leaves the system.

Figure 2 is a diagram of a batch reactor for photocatalytic oxidation of Fenton.

The reactor operates as follows. Contaminated water is collected in the reservoir, then it circulates through the photoreactor and, after cleaning, is drained from the reservoir.

Figure 3 is a diagram of a laboratory setup for photocatalytic oxidation of Fenton.

Installation works as follows. In a reactor with a structured catalyst illuminated by a mercury lamp, a solution is poured through which air is supplied. The temperature of the solution is controlled by a thermocouple. The released products of the oxidation of organic impurities (CO and CO ₂ ) after drying the exhaust gas are analyzed by gas analyzers. A liquid sample is taken for analysis from a circulation circuit.

Figure 4. represents the photocatalytic oxidation of Fenton in a nitrogen stream on a supported catalyst — LaMnO ₃ (3.67%) on cordierite.

The degree of decomposition of acetic acid (left axis,%) and the degree of decomposition of peroxide (right axis,%) along the ordinate axis, the reaction time (hour) along the abscissa. Experimental conditions: V total 100 ml; m _cat = 4.9 g; C ⁰ _CH3COOH = 0.021 mol / L; C ⁰ _H2O2 = 0.083 mol / L; P = 1 atm; T = 25 ° C; pH-3.9; Q _N2 = 250 cm ³ / min.

Figure 5 represents the change in the concentration of carbon dioxide (ordinate axis) formed during the photocatalytic oxidation of Fenton in a nitrogen stream on a supported catalyst — LaMnO ₃ (3.67%) on cordierite — versus time (abscissa, min). Experimental conditions: V total 100 ml; m _cat = 4.9 g; C ⁰ _CH3COOH = 0.021 mol / L; C ⁰ _H2O2 = 0.083 mol / L; P = 1 atm; T = 25 ° C; pH = 3.9; Q _N2 = 250 cm ³ / min.

The catalytic activity is investigated using acetic acid as a model compound. Optimal reaction conditions are determined by changing the experimental characteristics.

The presence of perovskite has a beneficial effect on the photodegradation of impurities due to the adsorption of pollutant molecules on the surface of the catalyst, thereby facilitating their excretion using hydroxyl radicals formed during the photodecomposition of H ₂ O ₂ .

Two types of catalysts are used:

a) a massive (non-supported) catalyst, which is prepared by mixing powders of mixed oxides containing perovskite LnMeO ₃ , lanthanide oxides (e.g. La, Ce, Nd, Pr, Sm, etc.) and a transition metal (Me = Fe) with a binder (or a structure-forming additive) based on aluminum oxide in an acidic medium followed by extrusion of a plastic mass in the form of monoliths (honeycomb blocks), drying at T = 120 ° C and calcination at T = 900 ° C for 4 hours with the general formula LnMeO ₃ · NAl ₂ About ₃ , where n varies from 10 to 98%. The catalytic activity of the LnFeO ₃ -containing catalyst was investigated using acetic acid as a model compound. The optimal reaction conditions are determined by changing the experimental characteristics;

b) the supported catalyst is prepared by applying the active phase to a refractory honeycomb carrier (cordierite) or foam based on aluminum oxide or SiC. Perovskites (LaMeO ₃ ), where Me = Mn and / or Co, and / or Fe, and / or Ni, and / or Cu are prepared by impregnating carriers with solutions of metal nitrate salts in ethylene glycol with citric acid additives. Samples are removed from the solution, dried in air and calcined at 900 ° C for 4 hours. The supported catalyst may additionally contain platinum, which is additionally applied from H ₂ PtCl ₆ after perovskite is applied. After platinum is applied, the samples are either dried in air or subjected to hydrazine hydrate or other reducing agents before drying.

The problem is also solved by the method of conducting / implementing the heterogeneous Fenton photocatalytic process for the decomposition of wastewater containing biodegradable organic compounds, such as acetic acid, and, in general, organic wastewater pollution using the catalysts described above, including with a metered supply of H ₂ O ₂ during the process. Dosed feed contributes to a more complete decomposition of organic impurities.

The Fenton process is carried out at room temperature and atmospheric pressure.

It can also be carried out at elevated temperature and pressure.

The process is carried out at pH greater than 5.

Wastewater may contain acetic acid, methyl tert-butyl ether (MTBE), ethanol, methanol, mixtures thereof, winemaking waste.

The process is carried out in a tubular irradiated Fenton photoreactor with a fixed layer and recirculation, or in a single-pass reactor of continuous action, or periodic action, or continuous-recirculation.

The gradual addition of H ₂ O _{2 is} carried out by introducing small volumes of a concentrated solution of H ₂ O ₂ every hour.

The gradual addition of H ₂ O ₂ can be carried out by the continuous introduction of a concentrated solution of H ₂ O ₂ .

Fenton's photocatalytic reaction hardware requires technically simple equipment.

For the implementation of the Fenton photocatalytic reaction, suspension reactors with a suspension of catalyst particles in contaminated water can be used.

Such a system has the following main advantages:

- high dispersion of the catalyst, the particles of which have a developed surface;

- good uniform irradiation of the catalyst;

- effective transfer of decomposable substances to the surface of the catalyst.

Next, it is necessary to separate the product (purified water) from the catalyst particles, for which additional sumps and filters are needed.

For the implementation of the Fenton photocatalytic reaction, reactors with a fixed layer of a perovskite-containing catalyst in the form of tablets, honeycomb blocks or foams, or thin films fixed on mechanically permeable carriers can also be used. In this case, there is no need to use separators. Moreover, such a reactor may be:

- single pass continuous operation;

- periodic action;

- continuous recirculation.

In a single-pass reactor (Figure 1), the neutralization of pollution is achieved in one pass of wastewater through the area of the reactor irradiated with light. In this case, it is necessary to optimize the control of the space velocity of water in order to reduce the length of the reactor.

In the batch reactor (FIG. 2), the contaminated water is stored in the tank and is continuously recycled through the photoreactor.

The reaction block in figure 3 is a tubular sealed reactor with a structured fixed layer of irradiated catalyst.

A UV radiation source with a wavelength greater than or equal to 254 nm is used in the reaction system. The catalytic activity in the decomposition of acetic acid, methyl tert-butyl ether (MTBE, СН ₃ ОС (СН ₃ ) ₃ ), methanol, ethanol, their mixtures and synthetic wine-making wastewater is evaluated (diluted Chianti red wine is used). Next, the effect of the dosed supply of H ₂ O ₂ and pH on the Fenton photocatalytic reaction is investigated.

The obtained results clearly indicate that the catalyst based on LaFeO _{3 is the} most effective in the photocatalytic Fenton reaction in comparison with a homogeneous reaction.

A higher reaction rate indicates perovskite activity. Moreover, the heterogeneous method of the Fenton photocatalytic reaction provides a wider pH range of the reaction compared to the narrow pH characteristic of a homogeneous reaction. In this case, a slight leaching of metals from perovskite after use in the process was established.

To study the catalytic activity of the Fenton photocatalyst, a fragment of the block honeycomb supported catalyst (2.5 g) based on LaFeO ₃ (2.24 wt.%) Was placed in 100 ml of acetic acid solution (0.021 mol / L, total organic carbon content (СОУ) ) = 500 mg / L) and hydrogen peroxide (0.083 mol / L) (in a molar ratio of H ₂ O ₂ / CH ₃ COOH = 4) under a lamp in a sealed stainless steel photoreactor. The gas released during the reaction from the sealed photoreactor is analyzed to determine the degree of decomposition. The initial pH of the solution is 3.9.

Before starting experiments with irradiation, the solution was passed through the reactor without irradiation for 10 minutes. The solution is then irradiated with UV light using an 8 W mercury lamp. Samples for analysis are taken in very small batches (500 μl) at regular intervals. The selected samples are filtered off and analyzed for the total content of organic carbon (СОУ) by the combustion method at Т = 850 ° С. To analyze the content of H ₂ O ₂ , spectrophotometric analysis in the ultraviolet and visible regions (UV-Vis) for the H ₂ O ₂ / TiOSO ₄ complex (λ = 405 nm), performed on a Perkin-Elmer lambda 35 spectrometer, is used.

Preliminary photolysis experiments (CH ₃ COOH / H ₂ O ₂ / UV) show an approximately 32% reduction in SDA.

In the presence of a massive block catalyst based on LnFeO ₃ and upon UV irradiation, a decrease in the SOA by ≈54% is observed with an un dosed supply of H ₂ O ₂ and ≈100% with the dosing of H ₂ O ₂ . In the presence of H ₂ O ₂ and irradiation, the reaction proceeds very quickly. The reaction rate increases due to the generation of OH ^. radicals under the influence of a catalyst. The reduction in SDA is very small in the absence of UV radiation.

Next, comparative studies of the heterogeneous photocatalytic Fenton reaction in the presence of a catalyst based on LaFeO ₃ and a homogeneous system with iron oxalate (C _{Fe3 +} = 0.0296 mol / L) as a catalyst are carried out.

The data in table 1 clearly indicate that the use of a heterogeneous system increases the degree of purification from organic carbon and the efficiency of hydrogen peroxide compared with a homogeneous system.

This is due to the adsorption of organic substrates on the surface of the catalyst. Indeed, contamination molecules adsorbed on the surface of the catalyst more easily react with OH radicals generated ^. with their subsequent decomposition.

It was found that iron is very slightly soluble in solution during the reaction.

Table 1 The influence of various experimental characteristics on the decomposition of acetic acid; (A) UV + LaFeO ₃ + CH ₃ COOH + H ₂ O ₂ ; (B) UV + solution of iron oxalate (C _{Fe3 +} = 0.0296 M) + CH ₃ COOH + H ₂ O ₂ ; (C) LaFeO ₃ + CH ₃ COOH + H ₂ O ₂ ; (D) UV + CH ₃ COOH + H ₂ O ₂ Time h The decrease in SDA,% BUT AT FROM D 0 0 0 0 0 one 13 fifteen four 7 2 41 twenty four 16 3 49 21 four 24 four 55 24 four 32

Examples

Examples 1-10 demonstrate the catalytic activity results obtained for the Fenton photocatalytic oxidation reaction on bulk LnFeO ₃ based catalysts and supported catalysts based on LaMnO ₃ , LaFeO ₃ , LaNiO ₃ , LaCoO ₃ , LaCuO ₃ and Pt / LaMnO ₃ .

Materials and Reagents

Glacial acetic acid (CH ₃ COOH) with a purity of 99.8% was provided by Carlo Erba, iron oxalate (Fe ₂ (C ₂ O ₄ ) ₃ · 6H ₂ O) with a purity of 99% by Aldrich, methyl tert-butyl ether ( CH ₃ OS (CH ₃ ) ₃ ) 99.9% purity by Aldrich, ethanol (C ₂ H ₅ OH) 99.9% purity provided by JT Baker, and methanol (CH ₃ OH) 99.9% purity by Aldrich .

Synthetic winemaking waste is prepared by diluting commercial red wine (Chianti) with ultrapure water to obtain an organic content of 500 mg C / l (as SDA). All solutions are prepared using ultrapure water (18 µS · cm ^-1 ).

Perovskite-based cell catalysts developed by the Institute of Catalysis named after G.K. Boreskov SB RAS, have a surface of 4-6 m ² / g for supported catalysts and 4-18 m ² / g for non-supported catalysts.

Solutions of organic compounds (e.g., CH ₃ COOH, CH ₃ OS (CH ₃ ) ₃ , C ₂ H ₅ OH, CH ₃ OH and winemaking waste) and hydrogen peroxide are prepared immediately before experiments to study the Fenton reaction and the Fenton photocatalytic reaction. For photocatalytic experiments, an 8 W mercury lamp with a wavelength greater than or equal to 254 nm is used. Prior to the beginning of experiments with irradiation, experiments were carried out in the dark with constant stirring.

In a typical experiment, 100 ml of a solution of an organic compound (for example, CH ₃ COOH, CH ₃ OS (CH ₃ ) ₃ , C ₅ H ₅ OH, CH ₃ OH) (SOU 500 mg / L) is placed in a photoreactor with a block honeycomb catalyst. Then add a concentrated solution of H ₂ O ₂ to obtain a stable ratio of H ₂ O ₂ / organic compound.

Catalytic tests are carried out with air supply (250 cm ³ / min) to the lower part of the sealed stainless steel photoreactor. The gas evolved from the photoreactor during the reaction is analyzed using an IR CO / CO ₂ analyzer. Catalytic tests are carried out at a temperature of 25 ° C and atmospheric pressure. The initial pH of the solution is adjusted by adding HCl or NaOH to achieve the desired value.

The total content of organic compounds (SOS) is estimated by the release of CO _X during catalytic combustion at a temperature of T = 850 ° C. The concentration of H ₂ O ₂ is determined by the complex of H ₂ O ₂ / TiOSO ₄ (λ = 405 nm) using a Perkin-Elmer Lambda 35 UV-Vis spectrometer. The leaching tests are carried out to determine the likelihood of metal leaching from perovskite during catalytic tests; for this, a model solution or synthetic wastewater from winemaking is analyzed using ICP-AES Varian "Liberty II".

Example 1. The effect of pH.

The effect of pH on the decomposition of acetic acid in the presence of a LaMnO ₃ catalyst (4 wt%) supported on a cordierite is shown in Table 2. The experiments were carried out at pH = 3.9, 6.0, and 8.0 and a molar ratio of R = H ₂ O ₂ / CH ₃ COOH = 4. The maximum degree of purification from organic compounds (decrease in SOS,% = 57%) is observed at pH = 6.0. A further increase in pH (to 8) leads to a decrease in the degree of purification to 22%. At pH = 6, the conversion of H ₂ 0 ₂ is slower than at pH = 9, while under more alkaline conditions the decomposition proceeded faster, but was incomplete (70%).

It is known that in homogeneous systems the optimal pH for the Fenton photocatalytic reaction is 3-4.

With changes in pH, a slight dissolution of Mn from perovskite is observed.

table 2 The effect of pH on the decrease in the total content of organic carbon on the catalyst 4 wt.% LaMnO ₃ / cordierite in the Fenton photocatalytic reaction Time h The decrease in SDA,% pH = 3.9 pH = 6.0 pH = 8.0 0 0 0 0 one 10 32 10 2 34 42 22 3 47 55 22 four 52 57 22

Example 2. The effect of the concentration of H ₂ About ₂ on the Fenton photocatalytic reaction.

The decomposition of acetic acid on a LaMnO ₃ catalyst supported on a cordierite (4%) at pH = 3.9 was studied by changing the initial concentration of hydrogen peroxide, in particular, changing the molar ratio R = H ₂ O ₂ / CH ₃ COOH from 2 to 8 (see table 3).

With an increase in the molar ratio R, the SOS removal rate decreases, while the final neutralization increases due to an increase in the content of OH radicals ^. in solution. At the same time, after the reaction, a slight dissolution of Mn perovskite is observed.

Table 3 The effect of the concentration of hydrogen peroxide on the photocatalytic Fenton reaction on the catalyst 4 wt.% LaMnO ₃ / cordierite Time h The decrease in SDA,% R = 2 R = 4 R = 8 0 0 0 0 one 21 10 7 2 31 34 24 3 33 47 35 four 33 52 53 5 33 54 60

Example 3. The effect of dosing of H ₂ About ₂ .

For the competitiveness of Fenton's photocatalytic processes, it is important that their application does not require large expenditures and is usually realized with low H ₂ O ₂ expenditures. An adjustable change in the concentration of H ₂ O ₂ allows you to achieve a greater decrease in the SOA in a shorter time due to the effect of "self-absorption" of H ₂ O ₂ , in which OH radicals are captured ^. generated by photolysis. The radicals OH ^. react with H ₂ O ₂ to form HO ₂ , which are less reactive than OH radicals ^. , and therefore unsuitable for the destruction of contaminants in solutions.

As a result, high initial concentrations of H ₂ O ₂ do not allow the use of OH ^. in the Fenton photoreaction, while their low concentrations do not give enough OH radicals for the reaction ^. . Thus, it is necessary to carry out the reaction with a controlled concentration of H ₂ O ₂ throughout the reaction. Therefore, the aim of the study is to select the dosage amount of H ₂ O ₂ optimal for the implementation of the Fenton photocatalytic reaction.

For the Fenton photocatalytic oxidation of acetic acid on a bulk / non-supported LnFeO ₃ catalyst containing 88 wt.% LnFeO ₃ and 12 wt.% Alumina, the total amount of gradually added hydrogen peroxide is C _H2O2 / t = 0.01 ÷ 0.1 mol / h, preferably C _H2O2 / t = 0.022 mol / h, which increases the total removal of organic compounds from 29% at an initial molar ratio of H ₂ O ₂ / CH ₃ COOH = 4 to 100% with a minimum specific consumption of H ₂ O ₂ (cm table 4); in particular, it varies in the region of 1 g of H ₂ O ₂ / g C - 10 g of H ₂ O ₂ / g C. After the reaction, an insignificant yield of iron from perovskite is noted.

Table 4 The cost of peroxide in the process of photocatalytic decomposition of acetic acid on a massive LnFeO ₃ catalyst (88 wt.%) With dosed and one-time (with the ratio of N ₂ O ₂ / CH ₃ COOH = 4) supply Decrease in SOU The amount of peroxide at a metered supply of N ₂ O ₂ , ppm Unit costs of Н ₂ O ₂ for the decomposition of organic matter at a metered supply, g _H2O2 / g _s The amount of peroxide in a single feed of H ₂ O ₂ , ppm Unit costs of H ₂ O ₂ for the decomposition of organic matter at a single feed, g _H2O2 / g _s twenty 446 4,5 2604 26,4 60 2453 8.2 - - one hundred 3814 7.6 - -

Example 4. Evaluation of decomposition in the photocatalytic Fenton reaction.

To assess the degree of decomposition, a study is carried out of the catalytic oxidation of acetic acid (R = 4) in the presence of a supported catalyst of 4 wt.% LaMnO ₃ / cordierite with a nitrogen supply (250 cm ³ / min) to the lower part of the sealed stainless steel photoreactor. After 5 hours of irradiation, the degree of purification from SDA is 30% (Figure 4).

The change in the concentration of CO ₂ in the gas phase during the Fenton photocatalytic reaction on the supported LaMnO ₃ / cordierite catalyst is shown in FIG. 5. No formation of CO is observed. The concentration of CO ₂ reaches a maximum level of approximately 850 ppm. after irradiation for 150 min and then decreases to zero after 500 min of irradiation, indicating complete removal of the extracted CO ₂ .

Further, based on the data on the reduction of SOA and the concentration of carbon dioxide formed, the material balance for carbon is close to 98%. This indicates that the complete decomposition of acetic acid was achieved in the Fenton photocatalytic oxidation reaction.

Example 5. Evaluation of the stability of the catalyst.

The stability of the catalytic system is studied by the example of a supported LaMnO ₃ (2 wt.%) / Cordierite catalyst in various cycles (up to 250 hours of experiment) of photooxidation of acetic acid on the same catalyst under the same experimental conditions (H ₂ O ₂ / CH ₃ COOH = 4) . It was noted that the catalyst reduced at T = 120 ° C and used repeatedly for the oxidation of acetic acid exhibits the same activity as a freshly prepared catalyst. The dissolution of Mn from perovskite after the reaction was negligible.

Example 6. The effect of the composition of the catalyst in a metered supply of peroxide.

For the Fenton photocatalytic oxidation of acetic acid on a bulk / non-supported (description of the preparation method on page 4) LnFeO ₃ catalyst containing 55 wt.% LnFeO ₃ and 45 wt.% Alumina, the total amount of gradually added hydrogen peroxide is C _H2O2 / t = 0.01 ÷ 0.1 mol / h, preferably C _H2O2 / t = 0.022 mol / h, the total removal of organic compounds at the initial molar ratio of H ₂ O ₂ / CH ₃ COOH = 4 is 100%. After the reaction, an insignificant yield of iron from perovskite is noted.

Example 7. The effect of the composition of the catalyst in a metered supply of peroxide.

For the Fenton photocatalytic oxidation of acetic acid on a bulk / non-supported (description of the preparation method on page 4) LnFeO ₃ catalyst containing 25 wt.% LnFeO ₃ and 75 wt.% Alumina, the total amount of gradually added hydrogen peroxide is C _H2O2 / t = 0.01 ÷ 0.1 mol / h, preferably With _H2O2 / t = 0.022 mol / h, the total removal of organic compounds at the initial molar ratio of H ₂ O ₂ / CH ₃ COOH = 4 is 100%. After the reaction, an insignificant yield of iron from perovskite is noted.

Example 8. The effect of the composition of the catalyst.

The decomposition of acetic acid in the presence of LaMnO ₃ catalyst deposited on SiC (6 wt.%) Was performed at pH = 6.0 and a molar ratio of R = H ₂ O ₂ / CH ₃ COOH = 4 (without dosing). The degree of purification from organic compounds is 60%. Perovskite dissolution is not observed.

Example 9. The effect of the composition of the catalyst.

The decomposition of acetic acid in the presence of a LaMnO ₃ catalyst supported on a cordierite (16 wt.%) Was performed at pH = 6.0 and a molar ratio of R = H ₂ O ₂ / CH ₃ COOH = 4 (without dosing). The degree of purification from organic compounds is 70%. Perovskite dissolution is not observed.

Example 10. The effect of the composition of the catalyst.

The decomposition of acetic acid in the presence of a 0.1% Pt / 4% LaMnO ₃ catalyst supported on a foam from Al ₂ O ₃ (ceramic foam) was performed at pH = 6.0 and a molar ratio of R = H ₂ O ₂ / CH ₃ COOH = 4 ( without dosing). The degree of purification from organic compounds is 70%. Perovskite dissolution was not observed.

Example 11. The effect of the composition of the catalyst.

The decomposition of acetic acid in the presence of LaMnO ₃ catalyst (25 wt.%) Supported _on alumina foam was performed at pH = 6.0 and a molar ratio of R = H ₂ O ₂ / CH ₃ COOH = 4 (without dosing). The degree of purification from organic compounds is 70%. Perovskite dissolution is not observed.

Advantages of the Invention

- A simple method for the preparation of perovskite-based catalysts for the Fenton photocatalytic reaction.

- The activity of perovskite-based catalysts was evaluated based on the results of studies on the decomposition of acetic acid, MTBE, methanol, ethanol, mixtures thereof and winemaking wastewater.

- Various reaction parameters such as the influence of pH, concentration of H ₂ O ₂ and dosing H ₂ O _2, are optimized; They are applicable for the processing of biodegradable wastewater.

- Perovskite-based catalysts exhibit high activity in the decomposition of acetic acid at pH = 6.

- Perovskite-based catalysts exhibit a high ability to decompose organic contaminants at room temperature and atmospheric pressure.

- Honeycomb-based perovskite catalysts are more effective in the Fenton photocatalytic reaction than homogeneous photo-Fenton systems.

- The synergistic effect of perovskite and H ₂ O ₂ is manifested in the adsorption of pollution molecules, thereby facilitating the decomposition of organic pollutants.

- The invention makes it possible to create an environmentally friendly method for the preparation of heterogeneous Fenton photocatalytic systems using a stable and effective Fenton photocatalyst for the disposal of biodegradable wastewater.

Photocatalytic decomposition of organic pollutants using the Fenton photocatalytic system can be more effective when the process is carried out in a heterogeneous mode and becomes important for modern oxidative technologies (COT). In particular, this invention is an effective technology for the removal of organic contaminants without the formation of precipitation and with short start times using structured heterogeneous catalysts.

Claims (15)

1. The catalyst for the heterogeneous photocatalytic process of Fenton for wastewater treatment, including biodegradable organic compounds, containing iron, characterized in that it is a powder or monolith containing perovskite LnFeO ₃ , where Ln = La, Ce, Pr, Nd , Sm, and a structure-forming additive. 2. The catalyst according to claim 1, characterized in that the perovskite content is 2.0-90.0 wt.%, The rest is a structure-forming additive, in which it contains aluminum oxide. 3. The catalyst according to claim 2, characterized in that the perovskite content is preferably 45.0-90.0 wt.%, Best of all 48.0-88.0 wt.%. 4. A catalyst for the heterogeneous Fenton photocatalytic process for wastewater treatment, including biodegradable organic compounds, containing perovskite and a carrier, characterized in that it is LaMeO ₃ or Pt / LaMeO ₃ perovskite, where Me = Mn, Co, Fe , Ni, Cu, deposited on a structured carrier, for example cordierite in the form of blocks of a honeycomb structure, foam based on aluminum oxide or SiC. 5. The catalyst according to claim 4, characterized in that the content of perovskite in the supported catalyst is 2.0-30.0 wt.%, Preferably 3.0-10.0 wt.%, Most preferably 4.0 wt.%. 6. The catalyst according to claim 4, characterized in that the platinum content in the supported catalyst is 0.05-10.0 wt.%, Preferably 0.05-3.0 wt.% And most preferably 0.1 wt.% 7. Fenton's heterogeneous photocatalytic process for wastewater treatment, including biodegradable organic compounds, characterized in that it is carried out when H ₂ O _{2 is} supplied during the process proceeding in the presence of a heterogeneous catalyst according to any one of claims 1 to 6, mainly when dosed supply of hydrogen peroxide. 8. The Fenton process according to claim 7, characterized in that it is carried out at room temperature and atmospheric pressure. 9. The Fenton process according to claim 7, characterized in that it is carried out at elevated temperature and pressure. 10. The Fenton process according to claim 7, characterized in that it is carried out at a pH of more than 5. 11. The Fenton process according to claim 7, characterized in that the wastewater may contain acetic acid, MTBE, ethanol, methanol, mixtures thereof, wine-making waste. 12. The Fenton process according to claim 7, characterized in that it is carried out in a tubular irradiated Fenton photoreactor with a fixed layer and recirculation, or in a single-pass reactor of continuous operation, or batch, or continuous-recirculation. 13. The Fenton process according to claim 7, characterized in that it is carried out at a dosed supply of H ₂ O ₂ during the process. 14. The Fenton process according to claim 7-9, characterized in that the gradual addition of H ₂ O _{2 is} carried out by introducing small volumes of a concentrated solution of H ₂ O ₂ every hour. 15. The Fenton process according to any one of claims 7 to 9, characterized in that the gradual addition of H ₂ O _{2 is} carried out by the continuous introduction of a concentrated solution of H ₂ O ₂ .

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