Cobalt-titanium composite oxide catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of environmental catalytic purification, and discloses a cobalt-titanium composite oxide catalyst and a preparation method and application thereof. The preparation method comprises the following steps: firstly, preparing a precursor solution from tetrabutyl titanate and cobalt nitrate; then, the precursor solution is subjected to sol and gel treatment and then roasted in an air atmosphere or an inert atmosphere, and a cobalt-titanium composite oxide is obtained; and finally, carrying out heating activation treatment on the cobalt-titanium composite oxide in a hydrogen-nitrogen mixed atmosphere, and then carrying out plasma treatment in an argon-nitrogen mixed atmosphere to obtain the cobalt-titanium composite oxide catalyst. The cobalt-titanium composite oxide catalyst has unique oxidation-reduction activity and stability, can efficiently and continuously catalyze and decompose phenols, cyanides and thiocyanides in wastewater under the conditions of low temperature, normal pressure and wide pH range, is easy to regenerate and can be repeatedly used, and has remarkable advantages compared with a traditional catalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental catalytic purification, and specifically relates to a cobalt-titanium composite oxide catalyst and a preparation method and application thereof. Background Art

[0002] Industrial wastewater contains many toxic and harmful substances, which not only pollute the environment but also endanger human health. Its treatment has always been valued. With the development of industry, the discharge of phenol-cyanide wastewater is also increasing. They come from industries such as coal gas, coking, metallurgy, and pesticides. For example, coking desulfurization wastewater and coking phenol-cyanide wastewater contain phenols, cyanide, thiocyanide and other toxic and harmful substances. Traditional treatment processes, such as adding chemical agents to precipitate pollutants for removal, or adding adsorbents to adsorb pollutants to purify wastewater, but these methods consume a lot of chemicals and adsorbents, and the treatment efficiency is not high.

[0003] Biological treatment is a new type of wastewater treatment method. Its treatment principle is to convert organic matter in wastewater into harmless substances through the metabolic activities of microorganisms, thereby achieving the purpose of purifying pollutants. Coking desulfurization wastewater contains complex organic and inorganic substances, some of which are resistant to biodegradation. Traditional biological methods are difficult to completely decompose these substances, resulting in unsatisfactory treatment effects. In addition, substances such as cyanide and thiocyanate contained in wastewater have a toxic effect on biological processes, further reducing treatment efficiency.

[0004] Catalytic oxidation technology is one of the important means of treating wastewater. This method uses strong oxidants (such as ozone, hydrogen peroxide, etc.) to oxidize and decompose pollutants in wastewater, converting them into harmless substances, and accelerating the oxidation reaction through catalysts, thereby achieving the purpose of purifying wastewater. However, existing catalysts often need to work under high temperature and high pressure conditions, with high processing costs, and the catalysts are easily deactivated, resulting in a gradual decrease in the treatment effect. The catalysts need to be frequently replaced or supplemented, which increases the operating and maintenance costs. The treatment effect also fluctuates over time, making it difficult to maintain long-term stability. Therefore, the development of an economical, efficient and long-lasting catalyst is of great significance for improving the performance of phenol-containing and cyanide-containing wastewater treatment processes. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a cobalt-titanium composite oxide catalyst and its preparation method and application in view of the deficiencies in the prior art. The catalyst has unique redox activity and stability, can efficiently and continuously catalyze the decomposition of phenols, cyanide and thiocyanide in wastewater at low temperature, normal pressure and a wide pH range, and is easily regenerated and reusable, which has significant advantages over traditional catalysts.

[0006] In order to solve the technical problem proposed by the present invention, the present invention provides a method for preparing a cobalt-titanium composite oxide catalyst, comprising the following steps:

[0007] 1) dissolving tetrabutyl titanate in ethanol to obtain a tetrabutyl titanate solution; dissolving cobalt nitrate in ethanol to obtain a cobalt solution; and mixing the tetrabutyl titanate solution and the cobalt solution dropwise to obtain a precursor solution;

[0008] 2) heating and stirring the precursor solution to form a sol, then cooling to room temperature and standing to form a gel, drying the gel and calcining it in an air atmosphere or an inert atmosphere to obtain a cobalt-titanium composite oxide;

[0009] 3) The cobalt-titanium composite oxide is firstly heated in a hydrogen-nitrogen mixed atmosphere for activation treatment, and then subjected to plasma treatment in an argon-nitrogen mixed atmosphere to obtain a cobalt-titanium composite oxide catalyst.

[0010] In the above scheme, when the tetrabutyl titanate is dissolved in ethanol, the volume ratio of the tetrabutyl titanate to the ethanol is 1:(5-10).

[0011] In the above scheme, when the cobalt nitrate is dissolved in ethanol, the mass ratio of the cobalt nitrate to the volume of ethanol is 1 g: (10-20) mL.

[0012] In the above scheme, the molar ratio of tetrabutyl titanate to cobalt nitrate is 1:(1-3).

[0013] In the above scheme, during the mixing process of the tetrabutyl titanate solution and the cobalt solution, a solvent may be gradually added to control the viscosity of the precursor solution to avoid the formation of precipitation.

[0014] Furthermore, the solvent is one of ethylene glycol, diethylene glycol, propylene glycol, N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0015] Furthermore, the volume of the solvent accounts for 5-10% of the total volume of the precursor solution.

[0016] Furthermore, the viscosity of the precursor solution is 1 to 5 mPa·s.

[0017] In the above scheme, the heating temperature of the heating and stirring is 70 to 90° C., and the processing time is 1 to 2 hours.

[0018] In the above scheme, the room temperature is 20-30° C., at which temperature the solvent gradually evaporates to form a gel.

[0019] In the above scheme, the drying temperature is 60-100° C. and the drying time is 6-12 hours.

[0020] In the above scheme, the calcination temperature is 500-800° C. and the calcination time is 4-6 hours.

[0021] In the above scheme, the volume fraction of hydrogen in the hydrogen-nitrogen mixed atmosphere is 5-10%.

[0022] In the above scheme, the heating temperature of the activation treatment is 300-400° C., and the treatment time is 2-4 hours.

[0023] In the above solution, the volume fraction of argon in the argon-nitrogen mixed atmosphere is 50-80%.

[0024] In the above scheme, the specific parameters of the plasma treatment are: power 50-200W, excitation frequency 30-50kHz, temperature 100-200°C, pressure 0.1-0.5MPa, and treatment time 10-30min.

[0025] The present invention also provides a cobalt-titanium composite oxide catalyst, which is prepared by the above method.

[0026] In the above scheme, the chemical formula of the cobalt-titanium composite oxide catalyst is Co x TiO y , where 0.5≤x≤2, 2.5≤y≤5.

[0027] In the above scheme, the particle size of the cobalt-titanium composite oxide catalyst is 20-50 nm, and the specific surface area is 100-150 m 2 / g, pore density is 0.5~1.5cm 3 / g, pore size is 2~10nm.

[0028] The present invention also provides an application of a cobalt-titanium composite oxide catalyst in catalytic oxidation treatment of phenol-cyanide-containing wastewater, and the application method is:

[0029] The cobalt-titanium composite oxide catalyst is fully contacted with the phenol-cyanide-containing wastewater, and then an auxiliary oxidant is added to the phenol-cyanide-containing wastewater to start the oxidation reaction, so as to catalyze and oxidize and decompose the phenol compounds, cyanide and thiocyanide in the phenol-cyanide-containing wastewater.

[0030] In the above scheme, the total suspended solid content of the phenol-cyanide-containing wastewater is ≤100 mg / L, the concentration of phenolic compounds is ≤200 mg / L, the concentration of cyanide is ≤50 mg / L, and the concentration of thiocyanide is ≤500 mg / L.

[0031] In the above scheme, the cobalt-titanium composite oxide catalyst is added through a fixed bed reactor or a stirred reactor, and the added amount is 5 to 15 g / L.

[0032] In the above scheme, the auxiliary oxidant is one of ozone and hydrogen peroxide.

[0033] In the above scheme, the addition amount of the auxiliary oxidant is 10 to 200 mg / L.

[0034] Furthermore, the amount of ozone added is 10 to 50 mg / L.

[0035] Furthermore, the added amount of hydrogen peroxide is 50 to 200 mg / L.

[0036] In the above scheme, the reaction temperature of the oxidation reaction is 30-50° C., and the reaction time is 0.5-1 h.

[0037] In the above scheme, the oxidation reaction process controls the wastewater pH to be 7-9 and the dissolved oxygen concentration to be greater than 6 mg / L.

[0038] In the above scheme, the cobalt-titanium composite oxide catalyst has a removal rate of phenol compounds in phenol-cyanide-containing wastewater of more than 95%, a cyanide removal rate of more than 98%, and a thiocyanide removal rate of more than 90%.

[0039] In the above scheme, the cobalt-titanium composite oxide catalyst can be regenerated after use by the following method:

[0040] The used cobalt-titanium composite oxide catalyst is washed and dried, and then heated and regenerated in a hydrogen-containing atmosphere to obtain a regenerated cobalt-titanium composite oxide catalyst.

[0041] Furthermore, the washing uses water or a dilute acid solution as a detergent, and the mass ratio of the cobalt-titanium composite oxide catalyst to the detergent after use is 1:(10-15).

[0042] Furthermore, the dilute acid solution is dilute hydrochloric acid or dilute nitric acid, with a concentration of 0.5 to 1 mol / L.

[0043] Furthermore, the washing temperature is 25 to 50° C. and the washing time is 10 to 20 minutes.

[0044] Furthermore, the drying temperature after washing is 60-80° C., and the product is dried until there is no residual moisture on the surface.

[0045] Furthermore, the volume fraction of hydrogen in the hydrogen-containing atmosphere is 5-10%, and the rest is inert gas.

[0046] Furthermore, the heating regeneration temperature is 300-400° C. and the time is 2-4 hours.

[0047] The technical concept of the present invention is:

[0048] 1. Composition design of the cobalt-titanium composite oxide catalyst of the present invention

[0049] The chemical formula of the cobalt-titanium composite oxide catalyst of the present invention is Co x TiO y , where cobalt (Co) and titanium (Ti) exist in multiple valent states in the oxide lattice to form a stable composite oxide structure. 2+ / Co 3+ ) and titanium ions (Ti 4+ ) provide abundant active sites, thus enhancing the redox ability of the catalyst. These active sites can effectively react with pollutants during wastewater treatment and promote the oxidative degradation of organic pollutants. By controlling the ratio of cobalt and titanium, the redox performance and surface characteristics of the catalyst can be adjusted to optimize its catalytic efficiency. The specific ratio adjustment can not only improve the degradation effect of the catalyst on different organic matter, but also adjust the stability and durability of the catalyst.

[0050] 2. Design of the preparation method of the cobalt-titanium composite oxide catalyst of the present invention

[0051] The present invention adopts a sol-gel method to prepare a cobalt-titanium composite oxide catalyst, and adopts tetrabutyl titanate and cobalt nitrate to prepare a precursor solution. By precisely controlling the ratio of titanium to cobalt, a catalyst with a high specific surface area is formed at low temperature, and then heating activation and plasma treatment are further introduced to modify the surface of the catalyst to optimize its catalytic performance. Among them, the heating activation process can promote the multivalent state transformation of cobalt without destroying the catalyst structure, increase the available redox active centers on the catalyst surface, and this treatment helps to enhance the catalytic activity of the catalyst in a low temperature environment, ensure its efficient operation in actual wastewater treatment, and extend the service life of the catalyst; plasma treatment further improves the surface activity of the catalyst by exciting the active sites on the catalyst surface, increases the contact and reaction rate between the catalyst and the organic pollutants, and the high-energy particles and free radicals of the plasma can effectively destroy the chemical structure of the pollutants and accelerate the oxidative decomposition of organic matter.

[0052] Through component design and surface modification technology, the active sites on the catalyst surface are more abundant and the catalytic performance has been significantly improved. In particular, the synergistic effect of heating activation and plasma treatment enables the catalyst to operate efficiently at room temperature and pressure, and has high stability, and can effectively treat complex organic pollutants.

[0053] 3. Mechanism of the cobalt-titanium composite oxide catalyst of the present invention for degrading pollutants

[0054] Cyanide (CN - ) degradation mechanism: Cyanide first reacts with the high valence state of cobalt (Co 3+) undergoes oxidation reaction to form nitrogen (N2) and water. Cobalt ions are reduced to a low-valent state (Co 2+ ), and then the low-valent cobalt reacts with water or oxygen to be oxidized to a high-valent state again. The continuation of this redox cycle allows cyanide to be efficiently oxidized and decomposed. In the reaction, the alternating multivalent states of cobalt form a redox cycle, which can effectively oxidize cyanide in wastewater into harmless nitrogen, avoiding the long-term residue of cyanide and the occurrence of secondary pollution.

[0055] Degradation mechanism of phenolic (C6H5OH) compounds: Phenolic compounds undergo oxidation reactions on the catalyst surface, generating intermediates (such as quinones) through the active sites of cobalt. These intermediates are further oxidized to carbon dioxide (CO2) and water (H2O) by the oxides produced on the catalyst surface. Cobalt-titanium composite oxide catalysts effectively destroy the benzene ring structure of phenolic compounds by providing active oxygen (such as hydroxyl radicals OH·), converting them into harmless small molecule compounds. This catalytic process fully utilizes the redox ability of cobalt-titanium composite oxides, ensuring the thoroughness of the reaction, and greatly improving the degradation rate of phenolic substances in water.

[0056] SCN - ) degradation mechanism: Thiocyanide molecules react with the active sites of cobalt on the catalyst surface to generate harmless sulfur and nitrogen. In this reaction, the redox cycle of cobalt still plays a key role, oxidizing thiocyanide into harmless gases. Due to the cyclic changes between the high and low valence states of cobalt, it can provide continuous redox ability, allowing thiocyanate to be rapidly degraded. In addition, oxygen defects on the catalyst surface further enhance the degradation efficiency of thiocyanate. Oxygen defects increase the number of active sites on the catalyst surface, making it more selective and efficient in degrading thiocyanate.

[0057] In summary, the cobalt-titanium composite oxide catalyst of the present invention achieves rapid degradation of pollutants through redox cycles, oxygen defect enhancement and effective utilization of active sites on the catalyst surface when degrading these pollutants. In addition, the catalyst of the present invention also produces a synergistic effect with an auxiliary oxidant (such as ozone or hydrogen peroxide), and the generated hydroxyl radicals (OH·) further improve the degradation efficiency. Ozone gas combines with the active sites on the catalyst surface to generate strong oxidizing free radicals (such as OH·), which react with organic pollutants to promote their degradation. By introducing hydrogen peroxide (H2O2), the catalyst can play a role in the Fenton reaction system to form OH· free radicals, further enhancing the degradation ability of cyanide, phenols and thiocyanate.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The present invention adopts a sol-gel method to prepare a cobalt-titanium composite oxide catalyst. By controlling the preparation conditions and calcination temperature of the sol-gel, the catalyst has a high specific surface area, which is beneficial for adsorbing pollutants in wastewater and improving the reaction rate. Then, heating activation and plasma treatment are introduced to modify the surface of the catalyst, and the active sites on the surface of the catalyst are further optimized, so that the catalyst has unique redox activity and stability. The catalyst can efficiently and continuously catalyze and decompose phenols, cyanides and thiocyanides in wastewater at low temperature, normal pressure and a wide pH range, and the catalyst is easily regenerated and can be reused, which has significant advantages over traditional catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is an EDS spectrum analysis diagram of the cobalt-titanium composite oxide catalyst obtained in Example 1 of the present invention.

[0061] Figure 2 This is an EDS spectrum analysis diagram of the cobalt-titanium composite oxide catalyst obtained in Example 2 of the present invention.

[0062] Figure 3 This is an EDS spectrum analysis diagram of the cobalt-titanium composite oxide catalyst obtained in Example 3 of the present invention. DETAILED DESCRIPTION

[0063] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0064] Example 1

[0065] A method for preparing a cobalt-titanium composite oxide catalyst comprises the following steps:

[0066] 1) dissolving tetrabutyl titanate in anhydrous ethanol, wherein the volume ratio of tetrabutyl titanate to anhydrous ethanol is 1:7, to obtain a tetrabutyl titanate solution; dissolving cobalt nitrate in anhydrous ethanol, wherein the mass ratio of cobalt nitrate to ethanol is 1 g:12 mL, to obtain a cobalt solution; mixing the tetrabutyl titanate solution and the cobalt solution dropwise, wherein the molar ratio of tetrabutyl titanate to cobalt nitrate is 1:1.5, and adding ethylene glycol during the mixing process to control the viscosity of the mixed solution to 3 mPa·s, and controlling the volume of the solvent to account for 6% of the total volume of the final mixed solution, to obtain a precursor solution;

[0067] 2) heating the precursor solution to 80° C. and stirring for 1.5 h to form a sol, then cooling to room temperature (25° C.) and standing to form a gel, drying the gel at 80° C. for 8 h, and then calcining in an argon atmosphere at a calcination temperature of 700° C. for 5 h to obtain a cobalt-titanium composite oxide;

[0068] 3) The cobalt-titanium composite oxide was first heated to 350°C in a hydrogen-nitrogen mixed atmosphere with a hydrogen volume fraction of 7% for activation treatment for 3 hours, and then plasma treated in an argon-nitrogen mixed atmosphere with an argon volume fraction of 60%. The specific parameters of the plasma treatment were: power 150 W, excitation frequency 40 kHz, temperature 150°C, pressure 0.3 MPa, and treatment time 20 min to obtain a cobalt-titanium composite oxide catalyst.

[0069] Figure 1 The EDS spectrum analysis diagram of the cobalt-titanium composite oxide catalyst obtained in this example. Through EDS spectrum quantitative analysis, the chemical formula of the cobalt-titanium composite oxide catalyst obtained is Co 0.9 TiO 2.8 .

[0070] The particle size of the cobalt-titanium composite oxide catalyst obtained in this example is 20-30 nm, and the specific surface area is 120.31 m 2 / g, pore density is 1.1cm 3 / g, pore size is 2~5nm.

[0071] Example 2

[0072] A method for preparing a cobalt-titanium composite oxide catalyst comprises the following steps:

[0073] 1) dissolving tetrabutyl titanate in anhydrous ethanol, wherein the volume ratio of tetrabutyl titanate to anhydrous ethanol is 1:8, to obtain a tetrabutyl titanate solution; dissolving cobalt nitrate in anhydrous ethanol, wherein the mass ratio of cobalt nitrate to ethanol is 1 g:15 mL, to obtain a cobalt solution; dropwise mixing the tetrabutyl titanate solution and the cobalt solution, wherein the molar ratio of tetrabutyl titanate to cobalt nitrate is 1:2, and during the mixing process, adding glycerol to control the viscosity of the mixed solution to 4 mPa·s, and controlling the volume of the solvent to account for 7% of the total volume of the final mixed solution, to obtain a precursor solution;

[0074] 2) heating the precursor solution to 85° C. and stirring for 1 h to form a sol, then cooling to room temperature 22° C. and standing to form a gel, drying the gel at 85° C. for 7 h, and calcining in an air atmosphere at a calcination temperature of 650° C. for 4 h to obtain a cobalt-titanium composite oxide;

[0075] 3) The cobalt-titanium composite oxide was first heated to 320°C in a hydrogen-nitrogen mixed atmosphere with a hydrogen volume fraction of 6% for activation treatment for 2 hours, and then plasma treated in an argon-nitrogen mixed atmosphere with an argon volume fraction of 55%. The specific parameters of the plasma treatment were: power 120 W, excitation frequency 35 kHz, temperature 120°C, pressure 0.2 MPa, and treatment time 15 min to obtain a cobalt-titanium composite oxide catalyst.

[0076] Figure 1 The EDS spectrum analysis diagram of the cobalt-titanium composite oxide catalyst obtained in this example. Through EDS spectrum quantitative analysis, the chemical formula of the cobalt-titanium composite oxide catalyst obtained is Co 1.6 TiO 3.8 .

[0077] The particle size of the cobalt-titanium composite oxide catalyst obtained in this example is 30-40 nm, and the specific surface area is 131.44 m 2 / g, pore density is 1.28cm 3 / g, pore size is 7-10nm.

[0078] Example 3

[0079] A method for preparing a cobalt-titanium composite oxide catalyst comprises the following steps:

[0080] 1) dissolving tetrabutyl titanate in anhydrous ethanol, wherein the volume ratio of tetrabutyl titanate to anhydrous ethanol is 1:6, to obtain a tetrabutyl titanate solution; dissolving cobalt nitrate in anhydrous ethanol, wherein the mass ratio of cobalt nitrate to ethanol is 1 g:18 mL, to obtain a cobalt solution; mixing the tetrabutyl titanate solution and the cobalt solution dropwise, wherein the molar ratio of tetrabutyl titanate to cobalt nitrate is 1:3, and during the mixing process, adding DMF to control the viscosity of the mixed solution to 2 mPa·s, and controlling the volume of the solvent to account for 5% of the total volume of the final mixed solution, to obtain a precursor solution;

[0081] 2) heating the precursor solution to 75° C. and stirring for 2 h to form a sol, then cooling to room temperature 28° C. and standing to form a gel, drying the gel at 70° C. for 10 h, and calcining in a helium atmosphere at a calcination temperature of 750° C. for 6 h to obtain a cobalt-titanium composite oxide;

[0082] 3) The cobalt-titanium composite oxide was first heated to 380°C in a hydrogen-nitrogen mixed atmosphere with a hydrogen volume fraction of 5% for activation treatment for 4 hours, and then plasma treated in an argon-nitrogen mixed atmosphere with an argon volume fraction of 70%. The specific parameters of the plasma treatment were: power 180 W, excitation frequency 50 kHz, temperature 180°C, pressure 0.4 MPa, and treatment time 25 min to obtain a cobalt-titanium composite oxide catalyst.

[0083] Figure 1 The EDS spectrum analysis diagram of the cobalt-titanium composite oxide catalyst obtained in this example. Through EDS spectrum quantitative analysis, the chemical formula of the cobalt-titanium composite oxide catalyst obtained is Co 1.8 TiO 4.6 .

[0084] The particle size of the cobalt-titanium composite oxide catalyst obtained in this example is 40-50 nm, and the specific surface area is 145.26 m 2 / g, pore density is 1.33cm 3 / g, pore size is 4 to 8 nm.

[0085] Application Example 1

[0086] The total suspended solids content of a coking desulfurization waste liquid to be treated is 80.6 mg / L, the concentration of phenolic compounds is 198.5 mg / L, the concentration of cyanide is 47.6 mg / L, the concentration of thiocyanate is 486.4 mg / L, the pH is 6.2, and the dissolved oxygen concentration is 4 mg / L.

[0087] The cobalt-titanium composite oxide catalyst prepared in Example 1 was applied to the catalytic oxidation treatment of the coking desulfurization waste liquid. The application method was as follows: the coking desulfurization waste liquid was pre-adjusted to pH 7.5 using a sodium hydroxide solution, and then added into a stirred reactor together with the cobalt-titanium composite oxide catalyst. Then, ozone was introduced into the stirred reactor to start the oxidation reaction. The amount of ozone introduced was 30 mg / L. During the reaction process, the dissolved oxygen was increased to 6.5 mg / L through an air oxygenation system, and the reaction temperature was controlled to 40°C. Samples were taken for detection after the reaction for 0.75 h.

[0088] Application Example 2

[0089] The total suspended solids content of a coking phenol-cyanide wastewater to be treated is 95 mg / L, the concentration of phenolic compounds is 180.5 mg / L, the concentration of cyanide is 44.6 mg / L, the concentration of thiocyanate is 453.1 mg / L, the pH is 6.2, and the dissolved oxygen concentration is 3.5 mg / L.

[0090] The cobalt-titanium composite oxide catalyst prepared in Example 2 is applied to the catalytic oxidation treatment of the coking phenol-cyanide wastewater, and the application method is as follows: the cobalt-titanium composite oxide catalyst is placed in a fixed bed reactor, the coking phenol-cyanide wastewater is pre-adjusted to pH 7.8 using a sodium hydroxide solution and then passed into the fixed bed reactor, and then hydrogen peroxide is added to start the oxidation reaction, the amount of hydrogen peroxide added is 100 mg / L, the dissolved oxygen is increased to 7 mg / L by an aeration pump during the reaction process, and the reaction temperature is controlled to 50°C, and sampling is carried out after the reaction for 1 hour.

[0091] Application Example 3

[0092] The total suspended solids content of a coking desulfurization waste liquid to be treated is 64.6 mg / L, the concentration of phenolic compounds is 169.7 mg / L, the concentration of cyanide is 48.1 mg / L, the concentration of thiocyanate is 473 mg / L, the pH is 5.8, and the dissolved oxygen concentration is 2.8 mg / L.

[0093] The cobalt-titanium composite oxide catalyst prepared in Example 3 was applied to the catalytic oxidation treatment of the coking desulfurization waste liquid. The application method was as follows: the coking desulfurization waste liquid was pre-adjusted to pH 7.2 using sodium hydroxide solution, and then added into a stirred reactor together with the cobalt-titanium composite oxide catalyst. Then, ozone was introduced into the stirred reactor to start the oxidation reaction. The ozone introduction amount was 40 mg / L. During the reaction process, the dissolved oxygen was increased to 6.2 mg / L through a microbubble oxygenation system, and the reaction temperature was controlled to 45°C. Samples were taken for detection after the reaction for 0.5 h.

[0094] Comparative Example 1

[0095] The difference between Comparative Example 1 and Application Example 1 is only that:

[0096] No cobalt-titanium composite oxide catalyst is added, that is, the coking desulfurization waste liquid is treated only by ozone oxidation.

[0097] Comparative Example 2

[0098] The difference between Comparative Example 2 and Application Example 1 is only that:

[0099] The cobalt-titanium composite oxide obtained in step 2) of Example 1 was used to catalytically oxidize and treat the coking desulfurization waste liquid.

[0100] Table 1

[0101]

[0102] As can be seen from Table 1, the cobalt-titanium composite oxide catalyst prepared in the embodiment of the present invention has a removal rate of phenol compounds in phenol-cyanide-containing wastewater of >95%, a cyanide removal rate of >98%, and a thiocyanate removal rate of >90%, showing excellent catalytic oxidation performance.

[0103] The cobalt-titanium composite oxide catalysts used for 6 months in Application Examples 1 to 3 were regenerated respectively by the following regeneration method: the used cobalt-titanium composite oxide catalysts were washed with a detergent, dried at 60 to 80° C. until there was no residual moisture on the surface, and then heated and regenerated in a hydrogen-containing atmosphere, wherein the volume fraction of hydrogen in the hydrogen-containing atmosphere was 5 to 10%, and the rest was nitrogen or helium, to obtain a regenerated cobalt-titanium composite oxide catalyst.

[0104] Table 2

[0105]

[0106] The cobalt-titanium composite oxide catalyst regenerated in Application Examples 1 to 3 was again applied to the catalytic oxidation treatment of coking desulfurization waste liquid or coking phenol-cyanide waste water. The application conditions were the same as the first application. The removal rate of phenols, cyanide and thiocyanate in the waste water by the regenerated cobalt-titanium composite oxide catalyst was tested.

[0107] Table 3

[0108] Experimental Group Removal rate of phenolic compounds Cyanide removal rate Thiocyanide removal rate Application Example 1 96.30％ 98.90％ 92.40％ Application Example 2 95.80％ 98.20％ 91.90％ Application Example 3 96.50％ 98.40％ 92.10％

[0109] As can be seen from Table 3, the impurities on the catalyst surface are first removed by washing, and then heated in a hydrogen-containing atmosphere for reduction treatment. The active sites of the catalyst are restored and can participate in the catalytic reaction again. After regeneration, its original excellent catalytic oxidation performance is maintained.

[0110] The above embodiments are merely examples for clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above descriptions. It is not necessary and impossible to list all the implementation methods here, and the obvious changes or modifications derived therefrom are still within the protection scope of the invention.

Claims

1. A method for preparing a cobalt-titanium composite oxide catalyst, characterized in that: The following steps are involved: 1) dissolving tetrabutyl titanate in ethanol to obtain a tetrabutyl titanate solution; dissolving cobalt nitrate in ethanol to obtain a cobalt solution; and mixing the tetrabutyl titanate solution and the cobalt solution dropwise to obtain a precursor solution; 2) heating and stirring the precursor solution to form a sol, then cooling to room temperature and standing to form a gel, drying the gel and calcining it in an air atmosphere or an inert atmosphere to obtain a cobalt-titanium composite oxide; 3) The cobalt-titanium composite oxide is firstly heated in a hydrogen-nitrogen mixed atmosphere for activation treatment, and then subjected to plasma treatment in an argon-nitrogen mixed atmosphere to obtain a cobalt-titanium composite oxide catalyst.

2. The method for preparing the cobalt-titanium composite oxide catalyst according to claim 1, characterized in that: The molar ratio of tetrabutyl titanate to cobalt nitrate is 1:(1-3); during the mixing process of the tetrabutyl titanate solution and the cobalt solution, a solvent is added to adjust the viscosity of the precursor solution to 1-5 mPa·s; the solvent is one of ethylene glycol, diethylene glycol, propylene glycol, N,N-dimethylformamide, and dimethyl sulfoxide, and the volume of the solvent accounts for 5-10% of the total volume of the precursor solution.

3. The method for preparing the cobalt-titanium composite oxide catalyst according to claim 1, characterized in that: The heating and stirring temperature is 70-90° C., and the time is 1-2 hours; the drying temperature is 60-100° C., and the time is 6-12 hours; the calcining temperature is 500-800° C., and the time is 4-6 hours.

4. The method for preparing the cobalt-titanium composite oxide catalyst according to claim 1, characterized in that: The volume fraction of hydrogen in the hydrogen-nitrogen mixed atmosphere is 5-10%; the heating temperature of the activation treatment is 300-400°C, and the treatment time is 2-4h; the volume fraction of argon in the argon-nitrogen mixed atmosphere is 50-80%; the specific parameters of the plasma treatment are: power 50-200W, excitation frequency 30-50kHz, temperature 100-200°C, pressure 0.1-0.5MPa, and treatment time 10-30min.

5. A cobalt-titanium composite oxide catalyst prepared by the preparation method according to any one of claims 1 to 4.

6. The cobalt-titanium composite oxide catalyst according to claim 5, characterized in that The chemical formula of the cobalt-titanium composite oxide catalyst is Co x TiO y , wherein 0.5≤x≤2, 2.5≤y≤5; the particle size of the cobalt-titanium composite oxide catalyst is 20-50 nm, and the specific surface area is 100-150 m 2 / g, pore density is 0.5~1.5cm 3 / g, pore size is 2~10nm.

7. A method for using the cobalt-titanium composite oxide catalyst as claimed in claim 5, characterized in that: The following steps are involved: The cobalt-titanium composite oxide catalyst is fully contacted with the phenol-cyanide-containing wastewater, and then an auxiliary oxidant is added to the phenol-cyanide-containing wastewater to start the oxidation reaction, so as to catalyze and oxidize and decompose the phenol compounds, cyanide and thiocyanide in the phenol-cyanide-containing wastewater.

8. The method for using the cobalt-titanium composite oxide catalyst according to claim 7, characterized in that: The concentration of phenolic compounds in the phenol-cyanide-containing wastewater is ≤200 mg / L, the concentration of cyanide is ≤50 mg / L, and the concentration of thiocyanate is ≤500 mg / L; the addition amount of the cobalt-titanium composite oxide catalyst is 5-15 g / L, and the removal rate of phenolic compounds in the phenol-cyanide-containing wastewater is greater than 95%, the removal rate of cyanide is greater than 98%, and the removal rate of thiocyanate is greater than 90%.

9. The method for using the cobalt-titanium composite oxide catalyst according to claim 7, characterized in that: The auxiliary oxidant is one of ozone and hydrogen peroxide, and the addition amount is 10-200 mg / L; the reaction temperature of the oxidation reaction is 30-50°C, the reaction time is 0.5-1h, and the pH value of the wastewater is controlled to be 7-9 during the oxidation reaction, and the dissolved oxygen concentration is greater than 6 mg / L.

10. The method for using the cobalt-titanium composite oxide catalyst according to claim 7, characterized in that: The cobalt-titanium composite oxide catalyst can be regenerated after use by the following method: The used cobalt-titanium composite oxide catalyst is washed and dried, and then heated and regenerated in a hydrogen-containing atmosphere at a heating temperature of 300 to 400° C. for 2 to 4 hours to obtain a regenerated cobalt-titanium composite oxide catalyst.

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