A total phosphorus rapid digestion device packaged with a micro-channel catalyst and a manufacturing method thereof

Abstract

The application relates to a total phosphorus rapid digestion device encapsulating a micro-channel catalyst and a manufacturing method, which is composed of two parts, i.e. an inner layer part encapsulating a micro-channel catalyst and an outer layer part filled with sandwiched silicon carbide electric heating filler. The inner layer part encapsulates a micro-channel catalyst strip, and the catalyst is synthesized, aged, calcined and then pressed; the sandwiched silicon carbide electric heating filler is arranged in the inner layer part, and heat can be generated to heat the inner layer part when direct current is applied to both sides. The inner layer part and the outer layer part need to be respectively manufactured and encapsulated, and then the two parts are secondarily encapsulated into one. The device has the characteristics of compact structure, good digestion effect and fast digestion speed, and the micro-channel catalyst has the advantages of low manufacturing cost and good catalytic effect, and can accurately and efficiently complete the total phosphorus test in practical application.

Description

TECHNICAL FIELD

[0001] The application relates to a total phosphorus rapid digester packaged with a micro-channel catalyst and a manufacturing method, and belongs to the field of environmental protection rapid detection devices. BACKGROUND

[0002] As one of the core indicators of water quality, the determination of the total phosphorus indicator is throughout the water quality evaluation and monitoring, pollution detection and tracing, water safety and inspection, sewage treatment and discharge and many other fields of various types of surface water and wastewater. In the process of determining the total phosphorus parameter, the digestion treatment of the related phosphorus pollutants in water is the most critical and indispensable link. The digestion process is the process of converting non-orthophosphate pollutants in wastewater, such as various organic phosphorus, condensed phosphates (pyrophosphate, metaphosphate and polyphosphate) and the like into orthophosphate, and then the test of the total phosphorus is realized by testing the color development result of the orthophosphate and the color developer after digestion. The digestion process is a very complex chemical reaction. Generally, persulfate, hydrogen peroxide, perchlorate and the like are used as oxidizing agents, and high temperature, high pressure, high radiation ultraviolet and the like are used to promote the oxidation of the orthophosphate in the total phosphorus to orthophosphate. In the "Determination of Phosphate and Total Phosphorus in Water - Continuous Flow-Ammonium Molybdate Spectrophotometric Method" (HJ670-2013), potassium superphosphate is used as an oxidizing agent, and ultraviolet digestion and 107 DEG C sulfuric acid acid hydrolysis are used for a total of 2-step digestion, and then reacted with ammonium molybdate in the presence of antimony salt to form phosphomolybdic acid, and then reduced to blue complex with ascorbic acid, and then the absorbance at 880 nm was determined to convert into the concentration of total phosphorus. Although the standard determination method has high accuracy and sensitivity for the total phosphorus test, there are still some disadvantages such as high investment cost of the related equipment digester, complex process operation, long test time, complicated maintenance of the digestion unit and the like, which seriously restrict the demand for rapid test of total phosphorus in special scenes such as river inspection, environmental supervision and evidence, pollution accident emergency detection and the like.

[0003] In recent years, the research on using catalytic PS to accelerate the digestion of total phosphorus has gradually become a hot spot, and the use of transition metal as raw material to prepare cheap catalysts to improve the reaction efficiency has become a trend. However, compared with the catalysts prepared by using traditional noble metal elements such as gold, platinum and iridium, the transition metal catalysts are limited by the catalytic activity of the material itself, and it is difficult to completely achieve the purpose of rapidly improving the digestion of total phosphorus even under the condition of adding 107 DEG C temperature. There are many reports on total phosphorus digestion devices in the prior art, for example: CN114577588A discloses a total phosphorus and total nitrogen integrated and automatic measurement system and an automatic measurement method thereof, CN217605451U discloses a rapid digestion device for detecting total phosphorus in soil, and CN113125425A discloses a water quality multi-parameter online monitoring device based on a micro-fluidic chip. However, the existing devices still rely on the process of ultraviolet digestion and acid hydrolysis, and cannot shorten the test time of total phosphorus to achieve rapid determination of total phosphorus.

[0004] Therefore, developing a digestion device that meets the national standard test requirements, shortens the digestion time, reduces the extreme digestion conditions and has low manufacturing cost becomes an urgent problem to be solved in the field of rapid total phosphorus testing. SUMMARY

[0005] In view of the deficiencies of the prior art, especially the low performance of the catalyst prepared by using transition metal as raw material, which is difficult to meet the demand of rapid digestion, and in order to reduce the manufacturing cost and improve the digestion effect, the application provides a total phosphorus rapid digester packaged with a micro-channel catalyst and a manufacturing method. The device has the characteristics of compact structure, good digestion effect and fast digestion speed, and the micro-channel catalyst has the advantages of low manufacturing cost and good catalytic effect.

[0006] The technical scheme of the application is as follows:

[0007] A total phosphorus rapid digester packaged with a micro-channel catalyst, comprising an inner layer component packaged with a catalyst and an outer layer component filled with a silicon carbide electric heating filler interlayer, the inner layer component being sleeved in the outer layer component;

[0008] The shell of the inner layer component is a high boron glass tube, the catalyst is filled in the high boron glass tube, and the catalyst is provided with a micro-channel for material transmission; the active component of the catalyst is composed of Co@C, Co@SiC, CoO@C, CoO / SiC and C / SiC;

[0009] The shell of the outer layer component is a high boron glass tube, the silicon carbide electric heating filler is filled in the inner wall of the high boron glass tube and arranged in an annular interlayer, the outer layer component is provided with a conductive ring in contact with the silicon carbide electric heating filler at both ends, and the conductive ring is connected with a lead wire through a hole.

[0010] According to the application, preferably, the average channel diameter of the micro-channel is 0.5-0.6 μm.

[0011] According to the application, preferably, the total phosphorus rapid digester is packaged by high boron glass tubes at both ends and is provided with a tube opening for material transmission; further preferably, the tube opening diameter at both ends of the total phosphorus rapid digester is smaller than the tube opening diameter of the high boron glass tube of the outer layer component.

[0012] According to the application, preferably, the catalyst is a catalyst strip matched with the high boron glass tube of the inner layer component.

[0013] According to the application, preferably, the conductive ring is a copper ring, and the lead wire is a copper wire.

[0014] According to the application, preferably, the high-boron glass tube of the inner layer component has an inner diameter of 8-12 mm, an outer diameter of 10-14 mm, a wall thickness of 1 mm, and a length of 50-100 mm;

[0015] Preferably, the high-boron glass tube of the outer layer component has an inner diameter of 12-16 mm, an outer diameter of 14-18 mm, a wall thickness of 1 mm, and a length of 55-105 mm.

[0016] According to the application, the total phosphorus rapid digestion device can be composed of two or more total phosphorus rapid digestion devices connected in series. In this way, the length of the digestion device is lengthened, the heating and catalytic reaction time is prolonged, and the catalytic reaction effect is improved, thereby further improving the accuracy of total phosphorus detection.

[0017] In the application, the outer layer component is internally provided with a silicon carbide electric heating filler layer. The silicon carbide electric heating filler is a heating body. When the wires of the total phosphorus rapid digestion device are connected to the positive and negative poles of a power supply, an electric current is generated to generate heat and heat the inner layer component.

[0018] According to the application, a catalyst for total phosphorus rapid digestion is also provided. The active component of the catalyst is composed of Co@C, Co@SiC, CoO@C, CoO / SiC and C / SiC.

[0019] According to the application, the preparation method of the catalyst comprises the following steps:

[0020] (a) preparing a water-soluble cellulose solution at a temperature of 80-85 DEG C, then adding cobalt acetate and zinc acetate to the solution, and stirring to obtain a mother liquor A;

[0021] (b) continuously keeping the temperature of the mother liquor A at 80-85 DEG C, adding silicon carbide to the mother liquor A, and ultrasonically treating to obtain a slurry B;

[0022] (c) adding deionized water to the slurry B, and ultrasonically treating at 80-85 DEG C until uniform to obtain a slurry C;

[0023] (d) aging the slurry C at a constant temperature to obtain a precursor D;

[0024] (e) freeze-drying the precursor D to a constant weight, and pressing the dried powder into a strip;

[0025] (f) calcining the strip at 450-550 DEG C under vacuum conditions to obtain the catalyst.

[0026] According to the application, preferably, the solvent of the water-soluble cellulose solution in step (a) is anhydrous ethylene glycol, and the mass concentration of the water-soluble cellulose solution is 2%.

[0027] Preferably, the molar ratio of Co:Zn in step (a) is (1-2):1, most preferably 1.5:1; the Co concentration in mother liquor A is controlled to be 0.06-0.09 mol / L;

[0028] Preferably, the mixture in step (a) is allowed to stand until it is clear and free of impurities and a distinct Tyndall phenomenon appears.

[0029] According to the present application, preferably, the silicon carbide in step (b) is absolutely dry silicon carbide with a purity of more than 98% and a particle size of less than 10,000 mesh (1.3 μm);

[0030] Preferably, the mass concentration of silicon carbide in slurry B is 100 g / L, and the silicon carbide is added in 5-10 portions.

[0031] Preferably, slurry B is prepared when the mixture in step (b) is uniform and free of lumps and does not separate after standing for 1 h.

[0032] According to the present application, preferably, the amount of deionized water used in step (c) is 2 times the total molar amount of Co+Zn ions.

[0033] Preferably, the pH of the mixed slurry in step (c) is adjusted to 7-8 using NaOH in ethylene glycol in multiple portions.

[0034] According to the present application, preferably, the aging temperature in step (d) is 160-200°C, most preferably 180°C; and the aging time is more than 3 days.

[0035] Preferably, the volume of the precipitate after aging in step (d) is less than 20% of the total volume of slurry C, and the supernatant is clear and free of a Tyndall phenomenon to obtain precursor D.

[0036] According to the present application, preferably, the powder in step (e) is pressed at a pressure of 0.5-0.8 MPa.

[0037] Preferably, the size of the solid rod in step (e) is φ 10 mm x 40 mm.

[0038] According to the present application, preferably, step (f) is performed under vacuum, the vacuum degree is an absolute pressure of 20 KPa or less, and the temperature is raised from ambient temperature to the calcination temperature at a rate of 5 K / min.

[0039] Preferably, the calcination temperature is 500°C, and the calcination time is 5 h.

[0040] According to the present application, the above-mentioned method for preparing a catalyst, in one preferred embodiment, comprises the following steps:

[0041] (a) Preparation of a 2% aqueous solution of water-soluble cellulose in a Teflon bottle at 80-85°C, then adding anhydrous cobalt acetate and anhydrous zinc acetate into the solution, followed by closing the Teflon bottle and stirring vigorously until the solution is clear to obtain mother liquor A;

[0042] (b) Continuing to keep the temperature of mother liquor A at 80-85°C, adding silicon carbide into mother liquor A at an amount of 100 g / L in 10 times, closing the Teflon bottle and starting ultrasonic treatment to obtain slurry B;

[0043] (c) Adding deionized water into slurry B, and ultrasonically treating at 80-85°C until uniform to obtain slurry C;

[0044] (d) Stopping ultrasonic treatment, closing the Teflon bottle and transferring it into a constant-temperature aging oven for aging for more than 3 days to obtain precursor D;

[0045] (e) Placing the Teflon bottle containing precursor D into a freeze vacuum dryer at -30°C for freeze drying until constant weight, and using a mold with an inner diameter of 10 mm to press the dried powder into a solid rod;

[0046] (f) Transferring the rod into a vacuum sintering furnace, purging with nitrogen for several times, vacuumizing to an absolute pressure of 20 KPa or below, heating from ambient temperature to 500°C at a rate of 5 K / min and keeping for 5 h, and stopping heating to naturally cool, thereby obtaining a catalyst rod containing microchannels.

[0047] According to the present application, the preparation method of the total phosphorus rapid decomposer packaged with the microchannel catalyst comprises the following steps:

[0048] (1) Preparation of the inner layer component

[0049] Uniformly brushing the inner layer component with silane coupling agent, inserting the catalyst rod, and using an electric heating clamp to heat the two ends of the high-boron glass tube after the silane coupling agent is cured to obtain the inner layer component packaged with the microchannel catalyst;

[0050] (2) Preparation of the outer layer component

[0051] (a) Mixing silicon carbide into anhydrous ethylene glycol uniformly, and placing it into a mold tube to press into a hollow tube;

[0052] (b) Placing the pressed hollow tube into a vacuum sintering furnace, vacuumizing to an absolute pressure of 20 KPa or below and keeping for 2 h, heating from ambient temperature to 500°C at a rate of 5 K / min and keeping for 1 h, continuing to heat to 2000°C at a rate of 3 K / min and keeping for 5 h, and then stopping heating to naturally cool, thereby obtaining a silicon carbide tube;

[0053] (c) using conductive silica gel, two conductive rings are adhered to the two sides of the silicon carbide tube and fixed to the conductive silica gel hardening, and then two wires are welded on the conductive rings on the two sides of the silicon carbide tube, to obtain a sandwiched silicon carbide hollow tube;

[0054] (d) the outer layer component is obtained by uniformly brushing silane coupling agent in the high boron glass tube of the outer layer component size, inserting the sandwiched silicon carbide hollow tube, punching at the conductive ring, and passing the wire connected to the conductive ring through the high boron glass tube of the outer layer component.

[0055] (3) Preparation of total phosphorus rapid digester

[0056] The outer layer component is obtained by uniformly brushing silane coupling agent in the high boron glass tube of the outer layer component size, inserting the sandwiched silicon carbide hollow tube, punching at the conductive ring, and passing the wire connected to the conductive ring through the high boron glass tube of the outer layer component.

[0057] According to the application, the inner layer component of the total phosphorus rapid digester packaged with a micro-channel catalyst is the core reaction site of the total phosphorus rapid digester, which is composed of a high boron glass tube of the inner layer component and a catalyst with a micro-channel, the average diameter of the micro-channel is 0.5-0.6 μm, and the catalytic active components are Co@C, Co@SiC, CoO@C, CoO / SiC and C / SiC. In the preparation process of the catalyst, zinc acetate is used as an activator and a pore-forming agent to make water-soluble cellulose form graphene C, and in the calcination process under a vacuum negative pressure environment at 500 DEG C, Zn is volatilized to form a micro-channel, the Co hydrate formed by the hydrolysis of the Sol-gel principle of cobalt acetate in the ethylene glycol system is dehydrated to form CoO, and the contact part of the graphene C and SiC is further reduced to elemental Co, and these Co and CoO are attached to the graphene C and SiC to form the above-mentioned five active substances.

[0058] The application has the following beneficial effects:

[0059] 1. In the application, based on the national standard "Determination of Phosphate and Total Phosphorus in Water - Continuous Flow Ammonium Molybdate Spectrophotometric Method" (HJ670-2013), a total phosphorus rapid digester packaged with a micro-channel catalyst and a manufacturing method are proposed, which are composed of an inner layer component packaged with a micro-channel catalyst and an outer layer component filled with sandwiched silicon carbide electric heating filler. The preparation materials of the inner and outer layers of the device are cheap and easy to obtain, the structure is simple and the manufacturing is convenient, which reduces the manufacturing cost, and in the test of total phosphorus, the combination with the continuous flow method can realize the automation, high efficiency and low reagent consumption of the test.

[0060] 2. The total phosphorus rapid digestion device with micro-channel catalyst encapsulated has the advantages that catalysis and heating can be realized at the same time, two-step digestion in total phosphorus determination is simplified into one, test conditions are greatly reduced, test time is shortened, in practical application, the device is simple to operate, high in accuracy and sensitivity for total phosphorus test, and the demand for rapid total phosphorus test is realized.

[0061] 3. The catalyst in the application does not use traditional noble metal elements such as gold and platinum, selects a low-cost transition metal element cobalt, and is prepared into a micro-channel catalyst strip, so that the specific surface area is increased, the effective amount of active substances is improved, and the catalytic performance is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 It is a preparation flow chart of the micro-channel catalyst strip in the application.

[0063] Figure 2 It is a perspective structural schematic diagram of the inner layer component of the total phosphorus rapid digestion device with micro-channel catalyst encapsulated.

[0064] Figure 3 It is a longitudinal section schematic diagram of the inner layer component of the total phosphorus rapid digestion device with micro-channel catalyst encapsulated.

[0065] Figure 4 It is a transverse section schematic diagram of the inner layer component of the total phosphorus rapid digestion device with micro-channel catalyst encapsulated.

[0066] Figure 5 It is a perspective structural schematic diagram of the outer layer component of the total phosphorus rapid digestion device with micro-channel catalyst encapsulated.

[0067] Figure 6 It is a longitudinal section schematic diagram of the outer layer component of the total phosphorus rapid digestion device with micro-channel catalyst encapsulated.

[0068] Figure 7 It is a transverse section schematic diagram of the outer layer component of the total phosphorus rapid digestion device with micro-channel catalyst encapsulated.

[0069] Figure 8 It is a perspective structural schematic diagram of the total phosphorus rapid digestion device with micro-channel catalyst encapsulated after inner and outer layer encapsulation.

[0070] Figure 9 It is a longitudinal section schematic diagram of the total phosphorus rapid digestion device with micro-channel catalyst encapsulated after inner and outer layer encapsulation.

[0071] Figure 10 It is a transverse section schematic diagram of the total phosphorus rapid digestion device with micro-channel catalyst encapsulated after inner and outer layer encapsulation.

[0072] Figure 11 The reference workflow chart for determination of total phosphorus by the continuous flow-ammonium molybdate spectrophotometry after ultraviolet digestion and 107 ℃ sulfuric acid hydrolysis is replaced by the total phosphorus rapid digester packaged with the microchannel catalyst of the present application.

[0073] Figure 12 The SEM, TEM photos and EDS element spectrum of the microchannel catalyst prepared in Example 1 of the present application.

[0074] In the figure, 1 is a catalyst, 2 is a high boron glass tube, 3 is a microchannel, 4 is a silicon carbide electric heating filler, 5 is a conductive ring, 6 is a hole, 7 is a lead wire, 8 is a peristaltic pump, 9 is a mixed reaction ring, 10 is a dialyzer, 11 is a heating ring, 12 is a total phosphorus rapid digester packaged with the microchannel catalyst, 13 is bubble removal, 14 is a flow detection cell, 15 is a sample, 16 is air, 17 is waste liquid, 18 is potassium persulfate digestion reagent, 19 is a surfactant solution, 20 is an ammonium molybdate solution, 21 is an ascorbic acid solution, and 22 is a secondary sample. DETAILED DESCRIPTION

[0075] In order to make the technical route and advantages of the present application clearer and more apparent, the technical solutions of the present application will be completely described below through examples and in combination with the accompanying drawings, but not as a limitation of the present application.

[0076] Example 1: Preparation of the microchannel catalyst, the specific process is shown in Figure 1

[0077] In a polytetrafluoroethylene bottle at 80-85 ℃, 500 ml of a water-soluble cellulose ethylene glycol solution with a mass concentration of 2% was prepared with anhydrous ethylene glycol as a solvent; then 90 mM of anhydrous cobalt acetate and 60 mM of anhydrous zinc acetate were added, the polytetrafluoroethylene bottle was closed and stirred vigorously until the solution was clear. When the mixture was clear and free of impurities and a clear Tyndall phenomenon appeared, mother liquor A was prepared;

[0078] The temperature of mother liquor A was continuously maintained at 80-85 ℃, and 10000 mesh (1.3 μm) absolutely dry silicon carbide with a purity of more than 98% was added to mother liquor A in 10 times with an addition amount of 100 g / L, the polytetrafluoroethylene bottle was closed and ultrasonic oscillation treatment was started. When the mixture was uniform and free of agglomeration and did not produce segregation after 1 h, slurry B was prepared;

[0079] 2.7 ml of deionized water was added to slurry B, and ultrasonic oscillation was performed at 80-85 ℃ until uniform, and the pH of the mixed slurry was adjusted to 7-8 in multiple times with a NaOH ethylene glycol solution, at which time slurry C was obtained;

[0080] ​Stop the ultrasonic oscillation, close the polytetrafluoroethylene bottle and transfer it into a constant temperature aging oven at 180℃ for aging for more than 3 days until the volume of the precipitate in the bottle is less than 20% of the total volume of the slurry C and the upper layer is clear and free of Tyndall phenomenon to obtain a precursor D;

[0081] Put the polytetrafluoroethylene bottle containing the precursor D into a refrigerated negative pressure vacuum dryer at -30℃ and freeze dry to a constant weight, and use a mold with an inner diameter of 10 mm to press the dry powder into a solid rod with a diameter of 10 mm and a length of 40 mm at a pressure of 0.5-0.8 MPa;

[0082] Transfer the rod to a vacuum sintering furnace, purge with nitrogen several times, and then vacuum to an absolute pressure of 20 KPa or below, heat from ambient temperature to 500℃ at a rate of 5 K / min and keep for 5 h, stop heating and cool naturally to obtain a micro-channel catalyst rod.

[0083] The SEM, TEM and EDS spectra of the catalyst in this embodiment are shown in Figure 12 , which shows that Figure 12 the cobalt atoms are dispersed in the entire structure, and C, O, Si and Co are uniformly distributed on the catalyst, and there are numerous micro-channels in the catalyst, with an average diameter of 0.5-0.6 μm.

[0084] In this embodiment, the catalytically active components are Co@C, Co@SiC, CoO@C, CoO / SiC and C / SiC.

[0085] During the preparation of the catalyst, zinc acetate acts as an activator and pore former, allowing water-soluble cellulose to form graphene C, and during calcination at 500℃ in a vacuum negative pressure environment, zinc ions volatilize to form micro-channels, and the Co hydrate formed by the Sol-gel principle of cobalt acetate in the ethylene glycol system undergoes dehydration and forms CoO, and the contact part with graphene is further reduced to elemental Co, which adheres to the graphene C and SiC to form the above-mentioned five active substances.

[0086] Example 2

[0087] As shown in Figures 9-10 , a total phosphorus rapid decomposer packaged with a micro-channel catalyst includes an inner layer component packaged with the catalyst 1 prepared in Example 1 and an outer layer component filled with a silicon carbide electric heating filler 4 interlayer, and the inner layer component is sleeved in the outer layer component.

[0088] The outer shell of the inner layer component is a high boron glass tube 2, and the catalyst 1 is filled in the high boron glass tube 2, and the catalyst 1 is provided with micro-channels 3 for material transmission.

[0089] The outer shell of the outer layer component is a high boron glass tube 2, and the silicon carbide electric heating filler 4 is filled in the inner wall of the high boron glass tube 2 and arranged in an annular interlayer, and the outer layer component is provided with a conductive ring 5 in contact with the silicon carbide electric heating filler 4 at both ends, and the conductive ring 5 is connected to the lead wire 7 through the hole 6.

[0090] In this embodiment, the total phosphorus rapid digester is packaged by high boron glass tubes 2 at both ends and provided with tube openings for material transmission; the diameters of the tube openings at both ends of the total phosphorus rapid digester are smaller than the diameters of the tube openings of the high boron glass tubes 2 of the outer layer component; the conductive ring 5 is a copper ring, and the lead wire 7 is a copper wire.

[0091] The high boron glass tube 2 of the inner layer component has an inner diameter of 10 mm, an outer diameter of 12 mm, a wall thickness of 1 mm, and a length of 100 mm.

[0092] The high boron glass tube 2 of the outer layer component has an inner diameter of 14 mm, an outer diameter of 16 mm, a wall thickness of 1 mm, and a length of 102 mm.

[0093] Example 3: Preparation of a total phosphorus rapid digester packaged with a microchannel catalyst

[0094] The preparation method of the total phosphorus rapid digester packaged with a microchannel catalyst in Example 2 comprises the following steps:

[0095] (1) Preparation of the inner layer component

[0096] As shown in Figures 2-4 , the inner layer component packaged with a microchannel catalyst is mainly composed of a catalyst 1 and a high boron glass tube 2, and the high boron glass tube 2 has an inner diameter of 10 mm, an outer diameter of 12 mm, a wall thickness of 1 mm, and a length of 100 mm. The inner wall of the high boron glass tube 2 is uniformly brushed with a silane coupling agent, and a catalyst 1 is inserted into the tube opening from both left and right sides and placed at a distance of 0.5 cm from the tube opening. After the silane coupling agent is solidified, an electric heating tongs is used to heat the middle of the high boron glass tube 2 to a tube inner diameter of 5 mm, and the two ends of the high boron glass tube 2 are heat sealed to a diameter of 5 mm at a distance of 0.5 cm from the tube opening. At this time, the inner layer component packaged with a microchannel catalyst is obtained, and the longitudinal and transverse cross-sectional view thereof is shown in Figure 3 、 Figure 4 .

[0097] (2) Preparation of the outer layer component

[0098] As shown in Figures 5-7 , the outer layer component filled with a silicon carbide electric heating filler 4 interlayer is mainly composed of a high boron glass tube 2, a silicon carbide electric heating filler 4, a conductive ring 5, a hole 6, and a lead wire 7. The conductive ring 5 is a copper ring, and the lead wire 7 is a copper wire.

[0099] The 10000 mesh (1.3 μm) absolutely dry silicon carbide with purity of 98% or more was mixed with 10% anhydrous ethylene glycol, and then pressed into a hollow tube with an outer diameter of 14 mm, an inner diameter of 12 mm, a thickness of 1 mm, and a length of 40 mm under a pressure of 10 MPa. The tube was placed in a vacuum sintering furnace, vacuumized to an absolute pressure of 20 KPa or less and kept for 2 h, heated from ambient temperature to 500°C at a heating rate of 5 K / min and kept for 1 h, and then heated to 2000°C at a heating rate of 3 K / min and kept for 5 h. The heating was stopped and the tube was naturally cooled to obtain a silicon carbide tube;

[0100] Two copper rings with an inner diameter of 12 mm, an outer diameter of 14 mm, and a thickness of 1 mm were adhered to the two sides of the silicon carbide tube by using conductive silica gel. The copper rings were fixed by using a pressure clamp with a clamping pressure of 2 MPa and kept for 2 h or more until the conductive silica gel hardened. Then, two copper wires were welded to the two sides of the silicon carbide tube to obtain a sandwiched silicon carbide hollow tube.

[0101] A high boron glass tube 2 with an inner diameter of 14 mm, an outer diameter of 16 mm, a wall thickness of 1 mm, and a length of 102 mm was uniformly coated with a silane coupling agent. Two sandwiched silicon carbide hollow tubes were inserted into the high boron glass tube 2 from the left and right sides, respectively. Two holes 6 were punched at a distance of 1.5 cm and 4.6 cm from the tube openings using a punching tool. The copper wires connected to the sandwiched silicon carbide hollow tubes were passed through the high boron glass tube 2. The copper wire passing through the hole 1.5 cm from the tube opening was connected to the positive electrode of an external DC power supply, and the copper wire passing through the hole 4.6 cm from the tube opening was connected to the negative electrode of the external DC power supply. At this time, the outer layer component filled with the sandwiched silicon carbide electric heating filler 4 was completed, and its longitudinal and transverse cross-sectional views are shown in Figure 6 、 Figure 7 The silicon carbide electric heating filler 4 sandwiched is a heating body that can generate heat to heat the inner layer component when a DC current is applied to both sides.

[0102] (3) Preparation of total phosphorus rapid digester

[0103] As shown in Figures 8-10 , the inner layer component high boron glass tube 2 was uniformly coated with a silane coupling agent, and then inserted into the outer layer component filled with the sandwiched silicon carbide electric heating filler 4. The central positions of the inner and outer layer components were kept aligned, and the outer layer component high boron glass tube 2 was heated and softened by using a heating clamp, and adhered to the wall of the inner layer component high boron glass tube 2. Then, the two ends of the outer layer component high boron glass tube 2 were softened and adhered to the tube openings of the inner layer component high boron glass tube 2, respectively, by using the heating clamp, to realize the packaging between the inner and outer layer components. The longitudinal and transverse cross-sectional views of the packaged total phosphorus rapid digester are shown in Figure 9 、 Figure 10 .

[0104] Test Example 1

[0105] For "determination of phosphorus and total phosphorus in water continuous flow-ammonium molybdate spectrophotometric method" (HJ670-2013), the principle is that the non-orthophosphate in wastewater is digested by ultraviolet and 107 DEG C sulfuric acid acid hydrolysis to obtain orthophosphate, and then reacts with ammonium molybdate to form phosphorus molybdenum heteropoly acid in the presence of antimony salt, followed by reduction with ascorbic acid to form a blue complex, and the absorbance is measured at 880 nm to convert the concentration of total phosphorus.

[0106] Based on this, the total phosphorus rapid digester packaged with the microchannel catalyst is connected with an additional direct current power supply, which replaces the two-step digestion position in "determination of phosphorus and total phosphorus in water continuous flow-ammonium molybdate spectrophotometric method" (HJ670-2013), and the working process of the continuous flow-ammonium molybdate spectrophotometric method for determining total phosphorus is as shown in the figure. Figure 11 The specific operation is as follows:

[0107] 1, turn on the power supply of the chemical reaction unit, lock the peristaltic pump 8 pressure plate, insert different reagents into the corresponding reagent bottles, start the computer, automatic sampler and data converter in turn, and open the analysis software. First, use water instead of reagent, and walk for 5 minutes, check the tightness of the whole analysis flow path and the smoothness of the liquid flow. Then turn on the direct current power supply of the total phosphorus rapid digester, wait for the baseline to be stable, and then set the parameters, including the measurement wavelength 880 nm, the sampling time 80 s, the cleaning time 100 s, and the air time 1 s.

[0108] 2, drawing of standard curve. As described in HJ670-2013, 0.00 ml, 0.05 ml, 0.50 ml, 1.00 ml, 2.50 ml and 5.00 ml of potassium dihydrogen phosphate standard solution (100 mg / L) are respectively removed, diluted with water to 100 ml, and a standard series of 6 concentration points is prepared. The corresponding total phosphorus concentrations are: 0.00 mg / L, 0.05 mg / L, 0.50 mg / L, 1.00 mg / L, 2.50 mg / L and 5.00 mg / L. An appropriate amount of standard series solution is measured and placed in a sample cup, and the sampler is programmed to take samples and measure in turn, and the calibration curve is y=1.0097x-0.0028, R 2 =0.9999, the linear fitting is good.

[0109] 3, the stored surface water and wastewater samples are determined, and 6 parallel samples are respectively prepared, and the determination results are shown in Table 1.

[0110] Table 1

[0111]

[0112] At the same time, the stored surface water and wastewater samples were subjected to standard addition recovery experiment, and the determination results are shown in Table 2.

[0113] Table 2

[0114]

[0115] From Tables 1 and 2, it can be seen that the total phosphorus rapid digester packaged with the microchannel catalyst can simultaneously perform catalytic oxidation and heating on the sample water, the preheating time is short, the digestion speed is faster, and thus the test can be completed in a short time, the automation program is higher, the operation is simple, the test results show that the precision of the method for determining the total phosphorus is higher, the standard addition recovery rate is better, and the method meets the national standard.

[0116] Test Example 2

[0117] In Test Example 1, the samples with standard values of 1.45 mg / L and 0.351 mg / L in the standard sample GSB07-3169-2014 of the Environmental Protection Department were determined, and the determination results are shown in Table 3.

[0118] Table 3

[0119]

[0120] From the test results in Table 3, it can be seen that the total phosphorus rapid digester packaged with the microchannel catalyst has higher accuracy for determining the total phosphorus, and meets the national standard.

Claims

1. A method for preparing a catalyst for rapid digestion of total phosphorus, characterized in that, The active components of the catalyst consist of Co@C, Co@SiC, CoO@C, CoO / SiC, and C / SiC, and the steps include the following: (a) Prepare a water-soluble cellulose solution at 80-85℃, then add cobalt acetate and zinc acetate to the solution and stir to obtain mother liquor A; (b) Continue to maintain the temperature of mother liquor A at 80-85℃, add silicon carbide to mother liquor A, and obtain slurry B after ultrasonic vibration treatment; (c) Add deionized water to slurry B and ultrasonically vibrate at 80-85℃ until homogeneous to obtain slurry C; (d) The slurry C was aged at a constant temperature to obtain the precursor D; (e) Precursor D is freeze-dried to constant weight and the dried powder is pressed into strips; (f) The material strip is calcined under vacuum at 450-550℃ to obtain the catalyst.

2. The method for preparing the catalyst for rapid digestion of total phosphorus according to claim 1, characterized in that, The solvent for the water-soluble cellulose solution in step (a) is anhydrous ethylene glycol, and the mass concentration of the water-soluble cellulose solution is 2%.

3. The method for preparing the catalyst for rapid digestion of total phosphorus according to claim 1, characterized in that, In step (a), the molar ratio of Co to Zn is (1-2):1; the Co concentration in mother liquor A is controlled at 0.06-0.09 mol / L.

4. The method for preparing the catalyst for rapid digestion of total phosphorus according to claim 1, characterized in that, The silicon carbide in step (b) is oven-dried silicon carbide with a purity of 98% or higher and a particle size of less than 10,000 mesh.

5. The method for preparing the catalyst for rapid digestion of total phosphorus according to claim 1, characterized in that, In step (b), the mass concentration of silicon carbide in slurry B is 100 g / L, and it is added in 5-10 portions.

6. The method for preparing the catalyst for rapid digestion of total phosphorus according to claim 1, characterized in that, The amount of deionized water used in step (c) is twice the total molar amount of Co+Zn ions.

7. The method for preparing the catalyst for rapid digestion of total phosphorus according to claim 1, characterized in that, In step (c), the pH of the mixed slurry needs to be adjusted to 7-8 multiple times using a NaOH-glycol solution.

8. The method for preparing the catalyst for rapid digestion of total phosphorus according to claim 1, characterized in that, The aging temperature in step (d) is 160-200℃, and the aging time is more than 3 days.

9. The method for preparing the catalyst for rapid digestion of total phosphorus according to claim 1, characterized in that, In step (e), the powder is pressed under a pressure of 0.5-0.8 MPa.

10. The method for preparing the catalyst for rapid digestion of total phosphorus according to claim 1, characterized in that, In step (f), calcination is carried out under vacuum conditions, with the vacuum level being an absolute pressure of 20 kPa or less; the temperature is increased from the ambient temperature to the calcination temperature at a heating rate of 5 K / min.

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