CN102636446B - On-line detection device for detecting total nitrogen and total phosphorus through ozone ultraviolet collaborative oxidative digestion - Google Patents

Abstract

The invention relates to an on-line detection device for detecting total nitrogen and total phosphorus by ozone ultraviolet synergistic oxidation and digestion, comprising a glass reaction tube, and an ultraviolet lamp is hung outside the glass reaction tube; the feature is: a water sample inlet and a Exhaust gas outlet, the water sample inlet is connected to the water sample storage tank; the bottom of the glass reaction tube is provided with an outlet, and the outlet is respectively connected to two pipelines arranged in parallel; the first pipeline is connected with the electrolysis method The ozone generator is connected, and a needle nozzle and a one-way valve are set at the gas output end of the electrolytic ozone generator; the second pipeline is connected to the first inlet port of the detection cell, and the second inlet port of the detection cell is connected to the total phosphorus color development port. The reagent supply tank is connected; the first outlet of the detection pool is connected with the spectrophotometer and the third injection pump, and the second outlet of the detection pool is connected with the waste liquid bucket. In the invention, ozone and water samples are irradiated with an ultraviolet lamp to oxidize and digest to generate hydroxyl radicals, so as to avoid the loss of some hydroxyl radicals.

Description

On-line detection device for detection of total nitrogen and total phosphorus by ozone ultraviolet synergistic oxidation digestion

technical field

The invention relates to a detection device for on-line detection of total nitrogen and total phosphorus in water quality, in particular to an on-line detection device for detecting total nitrogen and total phosphorus by ozone ultraviolet coordinated oxidation and digestion.

Background technique

The eutrophication of lakes and reservoirs is becoming more and more serious, which is closely related to the nitrogen and phosphorus content in the water. Excessive nitrogen and phosphorus content in water bodies will cause abnormal reproduction and growth of various aquatic plants. Large-scale cyanobacteria outbreaks have occurred in Taihu Lake, Chaohu Lake and other places.

At present, the detection of the content of nitrogen, phosphorus and other substances in water samples mainly adopts the method of artificial analysis in a simulated laboratory: firstly, some oxidation and digestion method is selected to digest the organic matter, and oxidize the elements to be detected in various valence states in the water sample into The unified highest valence form, and then use the difference in the ultraviolet absorption spectrum characteristics of various element ions to detect the content of the substance to be tested with an ultraviolet spectrophotometer. Among them, the oxidative digestion methods for water samples mainly include the following methods:

1. Add oxidant method:

(1) Adding potassium persulfate method: For the determination of total nitrogen in water samples, the national standard (GB 11894-89) "Determination of total nitrogen in water quality by alkaline potassium persulfate digestion UV spectrophotometry" (GB 11894-89) It is stipulated that under the condition of alkaline medium at 120~124°C, using potassium persulfate as an oxidant can not only oxidize ammonia nitrogen and nitrite nitrogen in water samples to nitrate, but also oxidize most of the organic nitrogen compounds in water samples. for nitrate. This method needs to consume the potassium persulfate reagent under the condition of heating and adding alkali, and needs to change the reagent frequently, the operation is complicated and the efficiency is low.

(2) Ozone addition method: Ozone is a strong oxidant with an oxidation potential of 2.07V, and reacts quickly with organic matter. Ozone is mixed with water samples through aeration or jet flow, and can react with various forms of pollutants in water, transform complex organic matter into simple compounds, and gradually oxidize low-valence ions to high-valence forms. The solubility of ozone in water is low, and it is selective to organic substances, so it is difficult to fully exert its oxidation and digestion effect.

(3) Hydrogen peroxide addition method: Hydrogen peroxide is a colorless viscous liquid. Its aqueous solution is commonly known as hydrogen peroxide. It is also a strong oxidant commonly used in water treatment. The oxidation potential is 1.77V, which can oxidize inorganic and organic pollution in water. thing. The chemical properties of hydrogen peroxide are unstable, and it is generally stored in the form of 30% or 60% aqueous solution. The storage and use of hydrogen peroxide are not easy to control, and it is difficult to apply to on-site testing.

2. Electrolytic oxidation method:

Wastewater electrolysis treatment is one of wastewater chemical treatment methods. The basic principle of electrolysis is applied to convert harmful substances in water samples into harmless substances through electrolysis to achieve purification. Wastewater electrolysis treatment includes electrode surface electrochemical action, indirect oxidation and indirect reduction, and electrocoagulation processes, which remove pollutants in wastewater with different functions. The disadvantage is that the power consumption and electrode metal consumption are relatively large when treating a large amount of wastewater, and the separated sediment is not easy to process and utilize. At the same time, metal cation interference will be generated in the solution, which is difficult to apply to water quality detection.

3. Synergistic digestion method of ozone and ultraviolet light:

The synergy of ozone and ultraviolet light is an advanced oxidation technology that can generate hydroxyl radicals. It has the characteristics of strong oxidation, mild reaction conditions, fast rate, and no need for catalysts. Patent 200710016757 is proposed based on this principle: use an ozone generator to generate a stable concentration of ozone and mix it with distilled water to form an ozone solution. After being irradiated by an ultraviolet lamp, the ozone solution is partially decomposed to produce hydroxyl radicals, which are then in non-dynamic equilibrium with the water sample. Oxidative digestion reaction takes place under these conditions. The disadvantage of this patent is that ozone is not easy to dissolve in water, so the content of ozone in the ozone solution and the hydroxyl radicals generated by decomposition under ultraviolet light may not be enough to completely oxidize the water sample; secondly, because hydroxyl radicals are the most active The active substance cannot exist stably. After some hydroxyl radicals are generated by ultraviolet lamp irradiation in the ozone solution balance tube, they are mixed with water samples in the serpentine coil reactor by flow injection. This process may have lost part of the hydroxyl radicals. free radicals. In addition, the continuous flow method cannot ensure that the water sample has sufficient time for oxidation and digestion reactions, resulting in low oxidation efficiency.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, and provide an online detection device for detecting total nitrogen and total phosphorus by ozone ultraviolet synergistic oxidation and digestion, which uses ozone and water samples to mix together and irradiate ultraviolet lamps together for oxidation and digestion to produce hydroxyl The structure of free radicals solves the situation in the prior art that ozone and its hydroxyl radicals are mixed with water samples in the reactor by flow injection, resulting in the loss of part of the hydroxyl radicals.

Another object of the present invention is to send ozone into the reaction tube by means of aeration to solve the problems in the prior art that ozone is not easily soluble in water and the content of hydroxyl radicals is not enough to completely oxidize the water sample.

According to the technical solution provided by the present invention, the on-line detection device for detecting total nitrogen and total phosphorus by ozone ultraviolet coordinated oxidation digestion includes a glass reaction tube, and a first ultraviolet lamp and a second ultraviolet lamp are suspended on both sides of the glass reaction tube; The feature is: a water sample inlet and an exhaust gas outlet are arranged at the upper end of the glass reaction tube, and the water sample inlet is connected to a water sample storage tank; a discharge port is provided at the bottom of the glass reaction tube, and the discharge ports are respectively connected to Two pipelines arranged in parallel; the first pipeline is connected with the electrolytic ozone generator, and a needle nozzle and a one-way valve are set at the gas output end of the electrolytic ozone generator; the second pipeline is connected with the first One inlet end is connected, and the second inlet end of the detection pool is connected with the supply tank of total phosphorus chromogenic agent; the first outlet end of the detection pool is connected with the spectrophotometer and the third syringe pump, and the second outlet end of the detection pool is connected with the waste Tank connection.

The spectrophotometer only outputs absorbance values at 220nm, 275nm and 700nm wavelengths.

A second solenoid valve is arranged between the second outlet end of the detection pool and the waste liquid barrel.

A first injection pump is arranged between the water sample inlet of the glass reaction tube and the water sample storage tank.

A first solenoid valve is arranged at the first inlet end of the detection cell.

A second injection pump is arranged between the second inlet end of the detection pool and the total phosphorus chromogen supply tank.

The on-line detection method of detecting total nitrogen and total phosphorus by the ozone ultraviolet synergistic oxidation digestion adopts an on-line detection device to carry out according to the following steps:

(1) Send 10ml of the water sample to be tested into the glass reaction tube from the water sample inlet;

(2) The electrolytic ozone generator produces ozone gas with a mass concentration of 18-20%. The ozone gas enters the glass reaction tube through the aeration method of the one-way valve and the needle nozzle, and the aeration rate is 630-770mg/h; An ultraviolet lamp is set on the outside of the glass reaction tube, and the ozone gas and the water sample to be tested are oxidized and digested under the irradiation of the ultraviolet lamp to obtain the digested water sample to be tested, and the time is 25 to 30 minutes;

(3) After oxidation and digestion are completed, the digested water samples to be tested are discharged into the detection pool;

(4) Test the total nitrogen content: 5ml of the digested water sample to be tested is drawn by the syringe pump into the spectrophotometer, and the remaining water sample to be tested is discharged into the waste liquid bucket; the spectrophotometer tests the digested water sample to be tested in the Absorbance values at 220nm and 275nm wavelengths are calculated to obtain the total nitrogen content;

(5) After the total nitrogen detection is completed, the syringe pump will return the water sample in the spectrophotometer to the detection pool, add 0.2ml of ascorbic acid solution to the detection pool, and add 0.4ml of molybdate solution after 30 seconds; After 10-20 minutes of medium color development, the digested water sample is sent to the spectrophotometer again, and the spectrophotometer detects the absorbance value of the water sample after color development at a wavelength of 700nm, and calculates the total phosphorus content.

The present invention is suitable for the oxidation and digestion treatment of water samples in the online continuous detection system of environmental water quality, which gets rid of the shortcomings of traditional laboratory analysis methods, does not need to consume chemical oxidants, is convenient to operate, simple and compact in equipment, simplified in process flow, and low in cost. Oxidation and digestion, and timely detection and display of total nitrogen and total phosphorus content in water samples, especially suitable for online detection system of total phosphorus and total nitrogen in environmental water quality. The present invention adopts the structure in which ozone and water samples are mixed in the reactor and then irradiated with ultraviolet lamps to oxidize and digest to generate hydroxyl radicals, which avoids the mixing of ozone and its hydroxyl radicals in the reactor by flow injection, resulting in The case where some hydroxyl radicals are lost. The invention injects the ozone into the reaction tube by means of aeration, which solves the problem that the ozone is not easy to dissolve in water and the content of the hydroxyl radical is not enough to completely oxidize the water sample.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Detailed ways

The present invention will be further described below in conjunction with specific drawings.

As shown in Figure 1: the online detection device for detection of total nitrogen and total phosphorus by ozone ultraviolet coordinated oxidation digestion includes a water sample storage tank 1, a first syringe pump 2, a glass reaction tube 3, an exhaust outlet 4, a first ultraviolet lamp 5, and a second Two ultraviolet lamps 6, needle nozzles 7, one-way valve 8, electrolytic ozone generator 9, first solenoid valve 10, total phosphorus chromogen supply tank 11, second injection pump 12, detection pool 13, third injection Pump 14, spectrophotometer 15, second solenoid valve 16, waste liquid bucket 17, etc.

The present invention includes a glass reaction tube 3 for oxidative digestion, the glass reaction tube 3 adopts a straight tube type quartz glass tube, the inner diameter of the glass reaction tube 3 is 8 mm, the outer diameter is 10 mm, and the length is 550 mm; The first ultraviolet lamp 5 and the second ultraviolet lamp 6 are hung on both sides of the outside respectively, and the first ultraviolet lamp 5 and the second ultraviolet lamp 6 can adopt a 14W single-ended straight ultraviolet lamp with a wavelength of 254nm; in the glass reaction tube The upper end of 3 is provided with a water sample inlet and an exhaust gas outlet 4, the water sample inlet is connected with the water sample storage tank 1 through a silicone hose, and the first syringe pump 2 is set between the water sample inlet and the water sample storage tank 1; The bottom of described glass reaction tube 3 is provided with discharge outlet, and this discharge outlet connects respectively the pipeline that two parallels are arranged; A needle nozzle 7 and a one-way valve 8 for aeration are arranged at the end; the second pipeline is connected with the first inlet end of the detection pool 13, and the first electromagnetic valve 10 is set on the first inlet end of the detection pool 13, The second inlet end of the detection pool 13 is connected with the supply tank 11 of the total phosphorus chromogenic agent, and the second injection pump 12 is set between the second inlet end of the detection pool 13 and the supply tank 11 of the total phosphorus chromogenic agent; the detection pool 13 The first outlet port of the detection tank is connected with the spectrophotometer 15 and the third syringe pump 14, and the second outlet port of the detection pool 13 is connected with the waste liquid bucket 17;

A second electromagnetic valve 16 is set between the second outlet end of the detection pool 13 and the waste liquid bucket 17;

Described spectrophotometer 15 adopts miniature spectrometer, only outputs the absorbance value of 220 nm, 275nm and 700nm wavelength.

The online detection method of detecting total nitrogen and total phosphorus in ozone ultraviolet coordinated oxidation digestion of the present invention adopts an online detection device to carry out according to the following steps:

(1) inject 10ml of the water sample to be tested from the water sample storage tank 1 into the glass reaction tube 3 via the first syringe pump 2;

(2) The electrolytic ozone generator 9 produces ozone gas with a mass concentration of 18-20%. The electrolytic ozone generator 9 uses electrolytic deionized water, and the ozone output is 700±10% mg/h; the ozone gas is supplied by the one-way valve 8 and the needle nozzle 7 enter the bottom of the glass reaction tube 3 by means of aeration, the aeration rate is 630~770mg/h, the small bubbles rise slowly along the pipeline of the glass reaction tube 3, and the gas bubbles in the glass reaction tube 3 to be tested After the water sample is fully contacted, the tail gas is discharged from the tail gas outlet 4 at the top of the glass reaction tube 3; an ultraviolet lamp is set outside the glass reaction tube 3, and the ozone gas and the water sample to be tested are oxidized and digested under the irradiation of the ultraviolet lamp to obtain the digested The water sample to be tested, the time is 25~30 minutes;

(3) After oxidation and digestion are completed, the digested water samples to be tested are discharged into the detection pool;

(4) Test the total nitrogen content: firstly, the third syringe pump 14 draws 5ml of the digested water sample to be tested into the spectrophotometer 15, and the remaining water sample to be tested is discharged into the waste liquid bucket 17 through the second solenoid valve 16 ; Spectrophotometer 15 tests the absorbance value of the water sample to be tested at 220nm and 275nm wavelength after the digestion, and calculates the total nitrogen content;

(5) After the total nitrogen detection is completed, the third syringe pump 14 returns the water sample in the spectrophotometer 15 to the detection pool 13, adds 0.2ml of ascorbic acid solution to the detection pool 13, and then adds 0.4ml of molybdenum in 30 seconds Salt solution (ascorbic acid solution and molybdate solution used here are both ascorbic acid solution and molybdate solution mentioned in GB11893-89 Determination of Total Phosphorus in Water Quality - Ammonium Molybdate Spectrophotometry); in the detection pool After developing the color for 10 to 20 minutes (the best color developing time is 15 minutes), the digested water sample is sent to the spectrophotometer 15 again, and the spectrophotometer 15 detects the absorbance value of the water sample after the color development at a wavelength of 700 nm, and calculates Get the total phosphorus content.

The invention adopts the structure that ozone and water samples are mixed together in the reactor and irradiated with ultraviolet lamps to oxidize and digest to generate hydroxyl radicals, which avoids the mixing of ozone and its hydroxyl radicals with water samples in the reactor by flow injection, Causes the loss of some hydroxyl radicals. The invention injects the ozone into the reaction tube by means of aeration, which solves the problem that the ozone is not easy to dissolve in water and the content of the hydroxyl radical is not enough to completely oxidize the water sample.

Claims (2)

1. An online detection device for detecting total nitrogen and total phosphorus by ozone ultraviolet coordinated oxidation digestion, comprising a glass reaction tube (3), and a first ultraviolet lamp (5) and a second ultraviolet lamp (5) are suspended on both sides of the glass reaction tube (3). Ultraviolet lamp (6); it is characterized in that: a water sample inlet and an exhaust gas outlet (4) are arranged on the upper end of the glass reaction tube (3), and the water sample inlet is connected to the water sample storage tank (1); The bottom of the glass reaction tube (3) is provided with a discharge port, which is respectively connected to two pipelines arranged in parallel; the first pipeline is connected to the electrolytic ozone generator (9), and the electrolytic ozone generator ( 9) The gas output end of the gas outlet is provided with a needle nozzle (7) and a one-way valve (8); the second pipeline is connected to the first inlet port of the detection pool (13), and the second inlet port of the detection pool (13) is connected to the total The phosphorus chromogen supply tank (11) is connected; the first outlet of the detection pool (13) is connected with the spectrophotometer (15) and the third syringe pump (14), and the second outlet of the detection pool (13) Connect with the waste liquid bucket (17); The spectrophotometer (15) only outputs absorbance values at wavelengths of 220nm, 275nm and 700nm; A second electromagnetic valve (16) is set between the second outlet end of the detection pool (13) and the waste liquid barrel (17); A first syringe pump (2) is arranged between the water sample inlet of the glass reaction tube (3) and the water sample storage tank (1); A first solenoid valve (10) is set at the first inlet end of the detection cell (13); A second injection pump (12) is arranged between the second inlet end of the detection pool (13) and the total phosphorus chromogen supply tank (11). 2. a kind of online detection method that ozone ultraviolet coordinated oxidation digestion detects total nitrogen and total phosphorus, it is characterized in that, described method adopts on-line detection device to carry out according to the following steps: (1) Send 10ml of the water sample to be tested into the glass reaction tube from the water sample inlet; (2) The electrolytic ozone generator produces ozone gas with a mass concentration of 18-20%. The ozone gas enters the glass reaction tube through the aeration method of the one-way valve and the needle nozzle, and the aeration rate is 630-770mg/h; An ultraviolet lamp is set on the outside of the glass reaction tube, and the ozone gas and the water sample to be tested are oxidized and digested under the irradiation of the ultraviolet lamp to obtain the digested water sample to be tested, and the time is 25 to 30 minutes; (3) After oxidation and digestion are completed, the digested water samples to be tested are discharged into the detection pool; (4) Test the total nitrogen content: 5ml of the digested water sample to be tested is drawn by the syringe pump into the spectrophotometer, and the remaining water sample to be tested is discharged into the waste liquid bucket; the spectrophotometer tests the digested water sample to be tested in the Absorbance values at 220nm and 275nm wavelengths are calculated to obtain the total nitrogen content; (5) After the total nitrogen detection is completed, the syringe pump will return the water sample in the spectrophotometer to the detection pool, add 0.2ml of ascorbic acid solution to the detection pool, and add 0.4ml of molybdate solution after 30 seconds; After 10-20 minutes of medium color development, the digested water sample is sent to the spectrophotometer again, and the spectrophotometer detects the absorbance value of the water sample after color development at a wavelength of 700nm, and calculates the total phosphorus content.

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