CN112225295B

CN112225295B - Tubular microporous titanium-based ruthenium oxide film anode applied to wastewater treatment and preparation method thereof

Info

Publication number: CN112225295B
Application number: CN202011115517.7A
Authority: CN
Inventors: 韩卫清; 王祎; 魏卡佳; 谷青青; 刘润; 沈锦优; 李健生; 孙秀云
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2020-10-19
Filing date: 2020-10-19
Publication date: 2021-10-15
Anticipated expiration: 2040-10-19
Also published as: CN112225295A

Abstract

The invention discloses a tubular microporous titanium-based ruthenium oxide film anode applied to wastewater treatment and a preparation method thereof, belonging to the field of electrochemical electrode preparation. The surface of the tubular microporous titanium-based ruthenium oxide film anode and the inner wall of a microporous pore passage are covered with ruthenium oxide layers, wherein the ruthenium oxide layers on the inner wall of the microporous pore passage are realized through a pore passage filling process. The anode disclosed by the invention has the advantages that the active sites of the electrode are increased, the collision probability of pollutants in the wastewater and the electrode is improved, the pollutants are effectively oxidized and degraded when passing through the micropores, and the degradation efficiency is improved; meanwhile, the aperture of the micropores is reduced after the ruthenium oxide layer is covered, the pollutant interception effect is improved, and the method can be better applied to the treatment of wastewater containing refractory organic pollutants.

Description

Tubular microporous titanium-based ruthenium oxide film anode applied to wastewater treatment and preparation method thereof

Technical Field

The invention belongs to the field of electrochemical electrode preparation, and particularly relates to a tubular microporous titanium-based ruthenium oxide film anode applied to wastewater treatment and a preparation method thereof.

Background

The electrochemical oxidation technology is an important branch of the prior advanced oxidation technology in wastewater treatment, and has the advantages of environmental friendliness, high reaction speed, simple and convenient equipment, easiness in realizing automatic control, no secondary pollution and the like because electrons are provided by an external power supply and are used as a reactant for reaction. Compared with other advanced oxidation technologies, the electrochemical oxidation technology has mild reaction conditions, can be carried out at normal temperature and normal pressure, and does not need to add any chemical reagent. Therefore, the electrochemical oxidation technology has gained wide attention and research at home and abroad in the last two decades, and has entered the practical application and engineering stage for treating the pollutants difficult to degrade in the chemical wastewater.

The electrode, which is the core of the electrochemical oxidation technology, is an important factor limiting the efficiency of electrochemical oxidation. In terms of electrode materials, metal oxide coated electrodes have been widely studied and applied in recent years due to their high stability and electrochemical activity. Wherein, ruthenium dioxide (RuO)₂) The earliest material found in the electrochemical technology and the longest application time has long service life, stable properties, thin metal layer, small particles, easy preparation on a tubular structure by a brush coating method, and the highest industrialization degree of electronic preparation, but the amount of generated OH is relatively limited, so that the treatment efficiency of the ruthenium dioxide electrode can be further improved.

In addition to electrode materials, the efficiency of electrochemical oxidation also depends greatly on the mass transfer of contaminants from solution to the surface of and near the electrode, and thus if the mass transfer process can be optimized, the mass transfer efficiency can be improved, and the treatment efficiency can be improved from another aspect. In terms of mass transfer efficiency of a system, a general electrochemical reactor usually adopts a plate-type counter electrode structure, so that the contact probability of pollutants and an electrode is smaller, and the mass transfer efficiency is not improved due to the fact that the water flow direction is perpendicular to the action direction of the electrode. Therefore, the electrode structure needs to be further optimized, and the introduction of the porous structure can realize 'close contact' between the pollutants and the electrode, stress the pollutants to pass through the pore channel, and also realize the function of membrane filtration.

The traditional preparation method of the titanium-based ruthenium oxide electrode usually adopts a brush coating method, and has no special step of modifying the pore channel. In the process of brushing, on one hand, the probability of the brush head penetrating into pores is very limited, and the brushing liquid (precursor liquid) cannot be uniformly smeared on the pore wall; on the other hand, due to the surface tension effect of the liquid, a concave liquid film is formed at the pore opening of the pore by the brushed precursor, so that the process that the precursor liquid enters the pore is further hindered, and the precursor liquid hardly flows into the pore through the gravity effect due to the existence of the liquid film caused by the surface tension effect. In conclusion, the traditional brush coating preparation method has limited modification on the inner wall of the pore channel, and the inner wall of the pore channel does not have a uniform metal oxide electrocatalytic active layer, so that the oxidation efficiency of the tubular microporous electrode is limited.

In addition, the microporous electrode has a membrane filtration effect. Micropores formed by titanium powder die-casting are large in aperture, if the aperture is controlled through a die-casting process, the pressure required to be applied is larger, and the particle size of the titanium powder is smaller, but the electrode preparation cost is greatly improved, meanwhile, higher requirements are provided for the die-casting process, the electrode preparation cost is more difficult to achieve, and the preparation process is more complicated.

Based on the above, there is a need to develop a titanium-based ruthenium oxide anode with better performance and a preparation method thereof, so as to be used for treating refractory wastewater.

Disclosure of Invention

1. Problems to be solved

Aiming at the problem that the modification of the inner wall of a microporous pore channel cannot be finished by adopting a traditional brush coating method in the preparation process of the tubular microporous titanium-based ruthenium oxide electrode, so that a ruthenium oxide layer cannot cover the inner wall of the microporous pore channel, and an active site and an electrochemical active layer are not arranged in the pore channel; meanwhile, under the condition that the aperture is large and the interception of macromolecular organic pollutants is not facilitated, the anode with the ruthenium oxide layer loaded on the surface of the microporous titanium substrate and the inside of the microporous pore channel is prepared by adopting a pore channel filling method.

2. Technical scheme

In order to solve the problems, the technical scheme adopted by the invention is as follows:

the invention provides a tubular microporous titanium-based ruthenium oxide film anode applied to wastewater treatment, which comprises a titanium substrate with a tubular structure and a ruthenium oxide layer, wherein micropores are distributed on the surface of the titanium substrate, and the ruthenium oxide layer is loaded on the surface of the titanium substrate and the inner wall of a pore passage of the micropores.

Preferably, the diameter of the micropores of the tubular microporous titanium-based ruthenium oxide film anode is 0.5-3 μm.

The invention provides a preparation method of a tubular microporous titanium-based ruthenium oxide film anode applied to wastewater treatment, which is characterized by adding a pore channel filling procedure, namely immersing a microporous titanium tube obtained after drying and shaping into a container filled with brush coating liquid for pore channel filling, and enabling the brush coating liquid to enter the inner wall of a pore channel of the titanium tube from the outer side of the titanium tube through micropores on the surface of the titanium tube by means of pressure difference between the outer side and the inner side of the titanium tube and the like, and contacting with the inner wall of the pore channel; and then, carrying out high-temperature sintering process treatment at higher temperature, so that the ruthenium oxide layer on the inner wall of the pore canal can stably exist.

Preferably, the pore filling procedure adopts a negative pressure induction mode, and specifically comprises the following steps: the titanium pipe is immersed into a container filled with the brush coating liquid, a water outlet pipe head of the titanium pipe and a vacuum pump are connected through a connecting pipe, the brush coating liquid is pumped into the connecting pipe in a vacuumizing mode, and the brush coating liquid can be repeatedly used.

Preferably, the pore filling process adopts a pressure propulsion mode, and specifically comprises the following steps: immersing the titanium tube in a container filled with the brush coating liquid, connecting the water outlet tube head of the titanium tube with a vacuum pump by a connecting tube, filling the tube with the brush coating liquid, starting a diaphragm pump to apply pressure inwards, and repeating for many times.

Preferably, the high-temperature sintering comprises two times, the first sintering temperature is 450-; and after repeated pore channel filling, performing secondary sintering at the temperature of 550-600 ℃ for 60-90 min.

Preferably, the high temperature sintering is performed in a muffle furnace.

Preferably, the tubular microporous titanium-based ruthenium oxide film anode preparation method comprises the steps of: titanium powder die casting, surface washing and etching, liquid preparation brushing, drying and shaping:

titanium powder die casting: casting titanium powder with a certain particle size into a tubular structure with a hole diameter and a closed end, and installing a water outlet pipe head;

surface washing and etching: soaking the die-cast titanium powder tube in ethanol, ultrasonically cleaning for a certain time, then placing the die-cast titanium powder tube in a heated oxalic acid solution for a certain time, repeatedly washing the die-cast titanium powder tube with deionized water, then soaking the die-cast titanium powder tube in the deionized water overnight, and cleaning to remove a surface oxide layer to obtain a bright silver color;

liquid preparation and brush coating: mixing and stirring isopropanol, hydrochloric acid with certain concentration and ruthenium trichloride tetrahydrate according to a certain proportion to prepare a brush coating liquid, and repeatedly brushing the brush coating liquid on the surface of the washed and corroded titanium tube until the surface of the titanium tube is brownish red;

drying and shaping: drying in a drying oven for a certain time to volatilize the solvent, and shaping the brush coating liquid on the surface of the titanium tube.

Preferably, before high-temperature sintering, liquid preparation brushing, drying and shaping, and pore filling are repeated for 3-5 times, and/or the pore filling is repeated for more than or equal to 5 times.

Preferably, in the titanium powder die-casting process, the particle size of titanium powder particles is 43-46 μm, the aperture of the prepared titanium tube is 3-5 μm, and the ratio of the diameter to the height of the tubular structure is less than or equal to 0.5;

and/or in the surface washing and etching procedure, the ultrasonic washing time is 0.5-1h, the volume concentration of the oxalic acid solution is 20-50%, the heating temperature is 60-100 ℃, and the duration time is 1-3 h;

and/or in the liquid preparation brush coating procedure, preparing a ruthenium trichloride isopropanol solution with the mass concentration of 15-20g/L, adding 15-20mL of 37% (mass concentration) hydrochloric acid into each liter of isopropanol, stirring for 24-36h, and rotating speed of more than 300 rpm;

and/or in the drying and shaping process, the drying temperature is 75-85 ℃, and the drying time is 10-15 min.

The invention provides a using method of a tubular microporous titanium-based ruthenium oxide film anode applied to wastewater treatment, which is characterized by comprising the following steps: the anode with ruthenium oxide layer loaded on the inner wall of the microporous pore passage is placed in a tubular reactor and used together with a metal cathode.

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) according to the tubular microporous titanium-based ruthenium oxide film anode, the ruthenium oxide active layers are loaded on the inner wall of the microporous pore passage and the surface of the titanium-based membrane, so that on one hand, the active sites of the electrode are increased, and the oxidation efficiency can be greatly increased when the tubular microporous titanium-based ruthenium oxide film anode is used for electrochemical wastewater treatment; on the other hand, the aperture is reduced, more macromolecular pollutants can be intercepted, the filtration function of the intercepting membrane is further enhanced, and the effluent quality is further optimized.

(2) The preparation method of the tubular microporous titanium-based ruthenium oxide film anode realizes the stable contact of the brush coating liquid and the inner wall of the pore passage by means of pressure difference and the like, overcomes the barrier effect of liquid surface tension and ensures that the ruthenium oxide layer can be attached to the inner wall of the pore passage.

(3) The preparation method of the tubular microporous titanium-based ruthenium oxide film anode optimizes the temperature in the sintering process, so that the ruthenium oxide layer in the pore canal can be effectively roasted, a stable metal oxide coating is formed on the inner wall of the microporous pore canal, the process operation is simple, and the conditions are easy to achieve.

Drawings

FIG. 1 is a tubular microporous titanium-based ruthenium oxide film anode of the present invention;

FIG. 2 is a comparison of a microporous titanium substrate with a tubular microporous titanium-based ruthenium oxide film anode;

FIG. 3 is an SEM image of the surface of a tubular microporous titanium-based ruthenium oxide film anode;

FIG. 4 is a comparison of XRD spectra of the surface of the tubular microporous titanium-based ruthenium oxide film anode, pure ruthenium oxide and titanium substrate, wherein (a) is a detection diagram of pure ruthenium oxide; (b) a detection picture of the titanium substrate; (c) the prepared tubular microporous titanium-based ruthenium oxide film anode;

FIG. 5 is a pore size distribution diagram of the surface of a tubular microporous titanium-based ruthenium oxide film anode;

FIG. 6 shows the removal of COD from chemical wastewater from pesticide production under the conditions of example 1;

FIG. 7 shows the removal of ammonia nitrogen from chemical wastewater from pesticide production under the conditions of example 1;

FIG. 8 shows the removal of COD from a dye wastewater under the conditions of example 2;

FIG. 9 shows the removal of chromaticity from a dye wastewater under the conditions of example 2;

FIG. 10 is a graph showing the comparison of the effect of treating COD in medical intermediate wastewater by using the tubular microporous titanium-based ruthenium oxide film anode of the present invention and a microporous titanium-based anode of the same size without filling via holes under the conditions of comparative example 1;

FIG. 11 is a comparison of the effect of the tubular microporous titanium-based ruthenium oxide membrane anode of the present invention on ammonia nitrogen in the medical intermediate wastewater treated by the same-sized microporous titanium-based anode without via filling under the conditions of comparative example 1.

In the figure: 1. a ruthenium oxide film anode; 2. a water outlet pipe head.

Detailed Description

The invention is further described with reference to specific examples.

It should be noted that the terms "upper", "lower", "left", "right" and "middle" used in the present specification are for the sake of clarity, and are not intended to limit the scope of the present invention, and changes or adjustments of the relative relationship thereof may be made without substantial technical changes.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs; as used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

As used herein, the term "about" is used to provide the flexibility and inaccuracy associated with a given term, measure or value. The degree of flexibility for a particular variable can be readily determined by one skilled in the art.

As used herein, at least one of the terms "is intended to be synonymous with one or more of. For example, "at least one of A, B and C" explicitly includes a only, B only, C only, and combinations thereof, respectively.

Concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a numerical range of about 1 to about 4.5 should be interpreted to include not only the explicitly recited limit values of 1 to about 4.5, but also include individual numbers (such as 2, 3, 4) and sub-ranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges reciting only one numerical value, such as "less than about 4.5," which should be construed to include all of the aforementioned values and ranges. Moreover, such an interpretation should apply regardless of the breadth of the range or feature being described.

Any steps recited in any method or process claims may be executed in any order and are not limited to the order presented in the claims.

Example 1

The tubular microporous titanium-based ruthenium oxide film anode is used as an anode, stainless steel is used as a cathode, and chemical wastewater from pesticide production is treated by the method, which comprises the following steps:

step one, preparing a tubular microporous titanium-based ruthenium oxide film anode, wherein the preparation steps are as follows:

the first step is as follows: casting titanium powder with the grain diameter of 43-46 mu m into a microporous titanium pipe with the aperture of 3-5 mu m;

the second step is that: placing the tubular microporous titanium substrate in ethanol, ultrasonically cleaning for 0.5h, placing in a 20% oxalic acid solution, heating to 80 ℃, maintaining for 1h, leaching for 3 times by using deionized water, and then soaking in the deionized water overnight;

the third step: preparing 15g/L ruthenium trichloride isopropanol solution, adding 37% hydrochloric acid according to the concentration of 15mL/L, stirring for 24h, dipping the brush-coating solution with a brush, and slowly and repeatedly coating until the titanium matrix is uniformly brownish red;

the fourth step: drying in 75 deg.C oven for 10min to volatilize solvent;

the fifth step: placing the anode titanium substrate in a container filled with brush coating liquid, connecting a water outlet of a transparent hose with a vacuum pump, pumping until the brush coating liquid appears in the hose, and repeating for 5 times;

and a sixth step: heating to 450 ℃ in a muffle furnace at a heating rate of 15 ℃/min, and sintering for 15 min;

the seventh step: repeating the processes of liquid preparation brushing, drying and shaping, and pore canal filling for 3 times, and sintering at 550 ℃ for 60 min; obtaining a prepared tubular microporous titanium-based ruthenium oxide film anode, as shown in figure 1, which comprises a closed end and an open end, wherein the open end is provided with a water outlet pipe head, wherein 1 is the ruthenium oxide anode; 2 is a water outlet pipe head;

the comparison of the microporous titanium matrix and the tubular microporous titanium-based ruthenium oxide film anode is shown in FIG. 2, wherein the surface of the titanium matrix and the inner wall of the microporous pore channel are both covered with ruthenium oxide layers;

FIG. 5 is a pore size distribution diagram of the surface of a tubular microporous titanium-based ruthenium oxide film anode.

Step two, assembling a tubular electrochemical treatment device and treating wastewater

The stainless steel tube is used as a cathode, and the current density is 15mA/cm²The COD of the pesticide wastewater is 13160mg/L and the ammonia nitrogen is 262.8mg/L, FIG. 6 shows the treatment effect of the COD in the example, FIG. 7 shows the removal effect of the ammonia nitrogen in the example, which is formed byAs can be seen, the electrode of the invention has excellent treatment effect on COD and ammonia nitrogen.

Example 2

The tubular microporous titanium-based ruthenium oxide film anode applied to wastewater treatment of the invention treats dye wastewater by taking stainless steel as a cathode, and comprises the following steps:

the second step is that: placing the tubular microporous titanium substrate in ethanol, ultrasonically cleaning for 1h, placing the tubular microporous titanium substrate in 30% oxalic acid solution, heating to 100 ℃, maintaining for 1.5 hours, leaching for 5 times by using deionized water, and then soaking in the deionized water overnight;

the third step: preparing 20g/L ruthenium trichloride isopropanol solution, adding 37% hydrochloric acid according to 20mL/L, stirring for 36h, dipping the brush-coating solution with a brush, and slowly and repeatedly coating until the titanium matrix is uniformly brownish red;

the fourth step: drying in oven at 85 deg.C for 15min to volatilize solvent;

and a sixth step: heating to 500 ℃ in a muffle furnace at a heating rate of 20 ℃/min, and sintering for 10 min;

the seventh step: repeating the processes of liquid preparation brushing, drying and shaping, and pore channel filling for 3 times, and sintering at 600 ℃ for 90 min; and obtaining the prepared tubular microporous titanium-based ruthenium oxide film anode.

The stainless steel tube is used as a cathode, and the current density is 10mA/cm²The COD of the dye wastewater is 1820mg/L, the chroma is 256 times, the treatment effect of the COD in the embodiment is shown in figure 8, the removal effect of the chroma in the embodiment is shown in figure 9, and the electrode of the invention has excellent treatment effect on both the COD and the chroma. .

Example 3

the second step is that: placing the tubular microporous titanium substrate in ethanol, ultrasonically cleaning for 0.8h, placing in 50% oxalic acid solution, heating to 60 ℃, maintaining for 3 hours, leaching with deionized water for 5 times, and then soaking in deionized water overnight;

the third step: preparing 18g/L ruthenium trichloride isopropanol solution, adding 37% hydrochloric acid according to 18mL/L, stirring for 24-3630h, dipping the brush coating liquid on the surface of the treated titanium matrix, and slowly and repeatedly coating until the titanium matrix is uniformly brownish red;

the fourth step: drying in 80 deg.C oven for 13min to volatilize solvent;

and a sixth step: heating to 480 ℃ in a muffle furnace at a heating rate of 20 ℃/min and sintering for 12 min;

the seventh step: repeating the processes of liquid preparation brushing, drying and shaping, and pore canal filling for 3 times, and sintering at 580 ℃ for 75 min; and obtaining the prepared tubular microporous titanium-based ruthenium oxide film anode.

Comparative example

Compared with the traditional microporous titanium-based anode which is not filled with pore channels, the tubular microporous titanium-based ruthenium oxide film anode prepared by the embodiment 1 of the invention is actually applied under the same conditions, and stainless steel is used as a cathode.

The preparation steps of the microporous titanium-based anode without pore channel filling are basically the same as those of the embodiment 1, except that: the process of filling the pore canal is not carried out.

Using two electrodes simultaneouslyThe actual wastewater of the medical intermediate with COD of about 10000mg/L and ammonia nitrogen of about 300mg/L is treated. All use 5mA/cm²Fig. 10 is a comparison of the removal effect of COD in the actual treatment in the comparative example, and fig. 11 is a comparison of the removal effect of ammonia nitrogen in the actual treatment in the comparative example. After the electrode is treated for 60min under the same conditions, the COD removal rate of the electrode after the electrode is filled by adopting the pore channels is 73.2%, and the ammonia nitrogen removal rate is 95.4%, compared with the COD removal rate of the electrode without the pore channels being filled by adopting the electrode without the pore channels being 54.8%, and the ammonia nitrogen removal rate being 85.3%, so that the electrode can obviously improve the wastewater treatment efficiency after the electrode is filled by the pore channels.

Claims

1. A preparation method of a tubular microporous titanium-based ruthenium oxide film anode applied to wastewater treatment is characterized by comprising the following steps: and (3) immersing the dried and shaped microporous titanium pipe into a container filled with brush coating liquid for pore channel filling, and making the brush coating liquid enter the inner side of the titanium pipe from the outer side of the titanium pipe through micropores on the surface of the titanium pipe by utilizing the pressure difference between the outer side and the inner side of the titanium pipe so as to make the brush coating liquid contact with the inner wall of the microporous pore channel, and then performing high-temperature sintering process treatment.

2. The method for preparing tubular microporous titanium-based ruthenium oxide film anode applied to wastewater treatment according to claim 1, which is characterized in that: the filling of pore channels adopts a negative pressure induction mode, which specifically comprises the following steps: and immersing the titanium pipe into the brush coating liquid, connecting the water outlet pipe head of the titanium pipe with a vacuum pump by using a connecting pipe, and pumping the titanium pipe into the connecting pipe by adopting a vacuumizing mode to generate the brush coating liquid.

3. The method for preparing tubular microporous titanium-based ruthenium oxide film anode applied to wastewater treatment according to claim 1, which is characterized in that: the pressure propulsion mode is adopted for pore channel filling, and the method specifically comprises the following steps: immersing the titanium tube into the brush coating liquid, connecting the water outlet tube head of the titanium tube with the diaphragm pump by using a connecting tube, filling the tube with the brush coating liquid, and starting the diaphragm pump to apply pressure inwards.

4. The method for preparing tubular microporous titanium-based ruthenium oxide membrane anode for wastewater treatment according to any one of claims 1 to 3, wherein the method comprises the following steps: the high-temperature sintering comprises two times, the first sintering temperature is 450-500 ℃, the sintering time is 10-15min, and the temperature rising speed is 15-20 ℃/min; and repeating the pore channel filling procedure, and then performing secondary sintering at the temperature of 550-600 ℃ for 60-90 min.

5. The method for preparing tubular microporous titanium-based ruthenium oxide film anode applied to wastewater treatment according to claim 4, which is characterized in that: the method also comprises the procedures of titanium powder die casting, surface washing and etching, liquid preparation and brush coating, drying and shaping before the pore filling procedure.

6. The method for preparing tubular microporous titanium-based ruthenium oxide film anode applied to wastewater treatment according to claim 5, which is characterized in that: before high-temperature sintering, repeatedly preparing liquid, brushing, drying and shaping, and filling in the pore canal for 3-5 times, and/or repeating the filling in the pore canal for more than or equal to 5 times.

7. The method for preparing tubular microporous titanium-based ruthenium oxide membrane anode for wastewater treatment according to any one of claims 5 to 6, wherein the method comprises the following steps:

in the titanium powder die-casting process, the particle size of titanium powder particles is 43-46 mu m, the aperture of the prepared titanium tube is 3-5 mu m, and the ratio of the diameter to the height of the tubular structure is less than or equal to 0.5;

8. The use method of the tubular microporous titanium-based ruthenium oxide film anode prepared by the preparation method according to any one of claims 1 to 7, which is characterized in that: the anode was placed in a tubular reactor and used with a metal cathode.