CN1259255C - Reactor for efficient removing organic pollutanti in water by catalysis and ozonization - Google Patents

Abstract

The invention provides a reactor for catalytic ozonation to remove organic pollutants in water. The reactor consists of a glass reaction column, an ozone inlet pipe, a porous quartz sand gas distribution system, a catalyst column and a constant temperature control system. A certain concentration of ozone gas is passed into the reaction column pre-installed with a certain concentration of organic pollutants, and under the combined action of the catalyst, it can achieve a greater degree of mineralization and removal of organic pollutants than ozone oxidation alone. When the herbicide alachlor is used as the target organic pollutant for catalytic ozonation treatment, more than 98% of alachlor can be removed after 30 minutes of catalytic ozonation treatment, and the removal rate of TOC can reach about 90% after 180 minutes of treatment . This reactor can control the treatment time of catalytic ozonation. After the catalyst is regenerated, it can be used repeatedly without affecting the treatment effect, and the metal dissolution during use is less than 2ppb, which will not cause secondary pollution to the treated water.

Description

A high-efficiency catalytic ozonation reactor for removing organic pollutants in water

technical field

The invention relates to a reactor for catalyzing ozone oxidation to remove organic pollutants in water. Specifically, a certain concentration of ozone gas is evenly distributed to a loaded Cu/Al ₂ O ₃ catalyst filled with water through a porous gas distribution plate. In the reactor where the honeycomb ceramic body exists, the organic matter in the water is oxidized under the catalysis of Cu/Al ₂ O ₃ .

Background technique

Source water, groundwater, surface water and industrial wastewater contain various refractory organic pollutants to varying degrees, such as various insecticides, herbicides, fungicides, macromolecule humus, small molecule organic carboxylic acids, etc. Existing water treatment processes are difficult to remove them completely. In addition, oxidation methods such as Cl ₂ and ClO ₂ will form a series of by-products that are still toxic and endocrine disrupting, causing secondary pollution to the treated water; O ₃ is highly oxidizing and unstable. After decomposition, it becomes oxygen, so ozonation is a safer water treatment technology. Studies have proved that ozone oxidation alone can effectively remove a variety of refractory organic pollutants, but under different pH conditions, the O ₃ oxidation reaction has a strong selectivity, and most substances cannot be completely mineralized into CO ₂ and H ₂ O, these substances still exist in the form of organic compounds containing aromatic rings or small molecule organic carboxylic acids, and their pollution to water cannot be completely eliminated. The UV/O ₃ method _and TiO ₂ photocatalytic method developed in recent years have proven to be effective in treating refractory organic pollutants in water. The separation of the catalyst is difficult, and the processing cost is high, so it is difficult to apply to the actual water treatment process. Therefore, a simple, efficient, and low-cost treatment method is the key to ozone treatment of water containing refractory organic pollutants. Studies have proved that a Cu/Al ₂ O ₃ catalyst can be used to catalyze the process of ozonation of refractory organic pollutants to obtain a high TOC removal rate. Organic carboxylic acids (oxalic acid, acetic acid, propionic acid, etc.) can be removed to a greater extent, making the ozone oxidation removal of refractory organic pollutants in water more thorough and complete.

Contents of the invention

The purpose of the present invention is to solve the problem that some organic matter in water cannot be completely mineralized and removed by ozone oxidation alone, overcome the defects of high cost and difficult separation of existing powder TiO ₂ heterogeneous catalytic ozonation, and invent a high-efficiency catalytic ozonation A reactor that removes refractory organic pollutants in water, improves the utilization rate of ozone in water, and achieves higher organic matter mineralization efficiency.

The reactor structure of the present invention is as shown in the accompanying drawings. The honeycomb ceramic catalyst 4 loaded with Cu/Al ₂ O ₃ and the ozone reaction column 5 are in the circulating water constant temperature system 6; the ozone gas generated by the ozone generator is evenly distributed in the reaction column through the intake pipe 1 and through the porous quartz sand gas distribution plate 3 , the air volume is controlled by the intake valve 2; the ozone gas fully reacts with the organic matter in the water; the remaining ozone gas enters the exhaust gas absorption device through the outlet pipe 9, and the air output can be controlled by adjusting the intake valve 2 and the outlet valve 8 as required; Samples are taken out from the sampling port 7 at regular intervals for analysis of alachlor concentration and TOC.

The ozone reaction column of the reactor is a glass column with a diameter of 30 mm and a height of 200 mm. The bottom is fixed with a porous gas distribution plate of quartz sand (aperture 10 μm), and the gas distribution plate is a honeycomb ceramic loaded with Cu/Al ₂ O ₃ catalyst. Body (diameter 29mm, height 100mm). Ozone is in full contact with organic matter and catalysts in the gaps of the honeycomb ceramic body through the porous gas distribution plate to complete the catalytic ozonation reaction.

Since the solubility of ozone gas in water is greatly affected by temperature, the change of temperature will also greatly affect the mass transfer of O ₃ in water, which in turn will greatly affect the reaction process of O ₃ oxidative degradation of organic matter. Therefore, in the present invention, the influence of temperature on the catalytic ozonation reaction is considered. The invention adopts a constant temperature circulating water bath to keep the temperature constant in the treatment process, so that the treatment can achieve a stable treatment effect within a predetermined time under the same water quality condition.

The reactor can also be made of stainless steel, and the gas distribution device is then replaced by a titanium porous gas distribution plate (pore size 10 μm), which is tightly fixed to the bottom of the reactor with a flange. It can make ozone gas dissolve in water more uniformly and efficiently, and then make ozone gas, water and catalyst more fully contact, and improve the efficiency of catalytic ozonation reaction. The diameter of the reactor is 70 mm, and the height is 300 mm. The upper cover of the reactor is also connected to the column of the reactor with a flange, so that the reaction can be carried out under airtight conditions. The remaining ozone gas enters the tail gas absorption device through the gas outlet for tail gas absorption.

The operation process of the reactor of the _present invention is as follows: the reactor is continuously rinsed several times with ultra-pure water, and continues to lead O in the empty reactor about 10 minutes to oxidize and remove organic or inorganic impurities remaining on the reactor to avoid _O3 is consumed during catalytic ozonation. Catalytic ozonation removes alachlor as a representative target organic pollutant, prepares a certain concentration of alachlor solution and adds it to the reaction column, seals the reactor, adjusts the inlet and outlet valves of the reactor to the required size, and turns on the ozone generation The device controls a certain ozone flow rate and concentration. At this time, as the zero time of the catalytic ozonation reaction, samples are taken at different reaction times for analysis. About 98% of alachlor can be removed after catalytic ozonation reaction for 30 minutes, and more than 90% of alachlor can be completely mineralized and removed after 180 minutes.

The determination method of the remaining _O concentration in water during the treatment process is as follows: use a syringe pre-installed with a certain concentration of Indigo reagent to draw an appropriate amount of water dissolved in O in the reactor from the sampling port, mix it _evenly immediately, and measure it colorimetrically at 600nm.

Features of the present invention are as follows:

1. The quartz sand porous gas distribution plate is used, which has no organic dissolution, and can evenly and effectively distribute ozone gas in the solution, improving the utilization rate of ozone.

2. The operation method is simple, the equipment is compact and easy to operate.

3. Various parameters are easy to control, and the reaction parameters can be adjusted at any time according to the needs, and the gas volume required for the reaction can be controlled through various methods.

4. The catalytic effect of the catalytic ozonation process is remarkable, which can realize the complete mineralization and removal of refractory organic pollutants in water.

5. The metal dissolution of Cu/Al ₂ O ₃ solid catalyst is extremely small, and will not cause secondary pollution to the treated water.

6. Cu/Al ₂ O ₃ solid catalyst can be used several times continuously after high temperature regeneration without reducing the catalytic effect.

7. The reactor is simple and low in investment, and the catalyst and the treated water are naturally separated after treatment.

8. The reactor has no special restrictions on the pH value of the water to be treated, which can be acidic, neutral or alkaline, and the treatment effect obtained is better than that of the single ozone oxidation treatment under the same water quality conditions.

9. The reactor can also be made of stainless steel, and the gas distribution device is replaced by a titanium porous gas distribution plate (pore size 10 μm), which can make the ozone gas dissolve in the water more uniformly and efficiently, and then make the ozone gas, water Contact with the catalyst more fully to improve the efficiency of catalytic ozonation reaction.

Description of drawings

The accompanying drawing is a schematic structural view of the reactor involved in the present invention.

Reference signs:

1. Intake pipe; 2. Intake valve; 3. Porous gas distribution plate; 4. Catalyst column; 5. Ozone reaction column; 6. Circulating water constant temperature system; 7. Sampling port; 8. Outlet valve; 9. Outlet pipe .

Detailed ways

Example 1:

Add 75ml of alachlor solution into the glass reactor, adjust each parameter of the O ₃ generator to the set value, generate O ₃ at a flow rate of 40ml/min, connect the gas inlet of the reactor after the gas flow is stable for 2 minutes, and start timing , the airtight oxidation reaction is carried out, and this time is regarded as 0 time. Carry out catalytic ozonation treatment under the following conditions:

Reaction target solution volume: 75ml

Reaction target solution concentration: Alachlor: 100mg/L, TOC: 60mg/L

Reaction target solution temperature: 20°C

Reaction solution system: 0.001M phosphate buffer solution

Solution initial pH: 7.00

O ₃ generation concentration: 12.2mg/L/min

Catalytic material: a cylindrical material formed by catalyst powder loaded on the surface of a honeycomb ceramic body

Sampling time points: 10min, 30min, 60min, 120min, 180min, alachlor and corresponding TOC removal rate after treatment are shown in Table 1.

Table 1 Example 1 Alachlor and TOC removal rate after treatment time (min) 10 30 60 120 180 Alachlor removal rate (%) non-catalytic 52.3 85.6 90.5 91.4 92.8 catalytic 68.5 97.6 98.5 99.0 99.3 TOC removal rate (%) non-catalytic 4.61 21.4 31.4 38.6 49.3 catalytic 5.22 36.9 56.4 82.2 87.3

Example 2:

Add 75ml of alachlor solution into the glass reactor, adjust each parameter of the O ₃ generator to the set value, generate O ₃ at a flow rate of 40ml/min, connect the gas inlet of the reactor after the gas flow is stable for 2 minutes, and start timing , the airtight oxidation reaction is carried out, and this time is regarded as 0 time. Carry out catalytic ozonation treatment under the following conditions:

Reaction target solution volume: 75ml

Reaction target solution concentration: Alachlor: 100mg/L, TOC: 60mg/L

Reaction target solution temperature: 20°C

Reaction solution system: 0.001M phosphate buffer solution

Solution initial pH: 4.30

O ₃ generation concentration: 12.2mg/L/min

Catalytic material: a cylindrical material formed by catalyst powder loaded on the surface of a honeycomb ceramic body

Sampling time points: 10min, 30min, 60min, 120min, 180min, alachlor and corresponding TOC removal rate after treatment are shown in Table 2.

Table 2 Example 2 Alachlor and TOC removal rate after treatment time (min) 10 30 60 120 180 Alachlor removal rate (%) non-catalytic 45.3 75.6 84.9 87.3 89.9 catalytic 59.4 85.7 93.8 95.6 95.8 TOC removal rate (%) non-catalytic 1.52 21.2 26.2 38.0 48.1 catalytic 3.93 28.7 47.2 74.1 80.8

Example 3:

Add 75ml of alachlor solution into the glass reactor, adjust each parameter of the O ₃ generator to the set value, generate O ₃ at a flow rate of 40ml/min, connect the gas inlet of the reactor after the gas flow is stable for 2 minutes, and start timing , the airtight oxidation reaction is carried out, and this time is regarded as 0 time. Carry out catalytic ozonation treatment under the following conditions:

Reaction target solution volume: 75ml

Reaction target solution concentration: Alachlor: 100mg/L, TOC: 60mg/L

Reaction target solution temperature: 20°C

Reaction solution system: 0.001M phosphate buffer solution

Solution initial pH: 9.10

O ₃ generation concentration: 12.2mg/L/min

Catalytic material: a cylindrical material formed by catalyst powder loaded on the surface of a honeycomb ceramic body

Sampling time points: 10min, 30min, 60min, 120min, 180min, alachlor and corresponding TOC removal rate after treatment are shown in Table 3.

Table 3 Example 3 Alachlor and TOC removal rate after treatment time (min) 10 30 60 120 180 Alachlor removal rate (%) non-catalytic 63.7 89.5 92.5 94.1 95.3 catalytic 70.5 98.2 98.7 99.2 99.5 TOC removal rate (%) non-catalytic 5.05 23.2 37.7 48.9 58.4 catalytic 10.3 40.6 66.9 86.8 89.7

It can be seen from Table 1-3 that no matter under acidic, alkaline or neutral conditions, the catalytic ozonation process under the action of Cu/Al ₂ O ₃ catalyst can show better alachlor than that under the action of O ₃ alone And TOC removal effect.

Example 4:

Add 75ml of alachlor solution into the glass reactor, adjust each parameter of the O ₃ generator to the set value, generate O ₃ at a flow rate of 40ml/min, connect the gas inlet of the reactor after the gas flow is stable for 2 minutes, and start timing , the airtight oxidation reaction is carried out, and this time is regarded as 0 time. Carry out catalytic ozonation treatment under the following conditions (catalyst is used several times continuously at 500°C for high temperature regeneration and then reused):

Reaction target solution volume: 75ml

Reaction target solution concentration: Alachlor: 100mg/L, TOC: 60mg/L

Reaction target solution temperature: 20°C

Reaction solution system: 0.001M phosphate buffer solution

Solution initial pH: 7.00

O ₃ generation concentration: 12.2mg/L/min

Catalytic material: a cylindrical material formed by catalyst powder loaded on the surface of a honeycomb ceramic body

Sampling time points: 10min, 30min, 60min, 120min, 180min, alachlor and corresponding TOC removal rate after treatment are shown in Table 4.

Table 4 Example 4 Alachlor and TOC removal rate after treatment time (min) 10 30 60 120 180 Alachlor removal rate (%) 68.3 97.2 98.3 89.8 99.0 TOC removal rate (%) 5.03 35.4 55.9 81.7 87.1

It can be seen from Table 4 that when the Cu/Al ₂ O ₃ catalyst is continuously used and regenerated at high temperature for several times, it can still show a strong catalytic effect. In addition, it can be seen from the results of the determination of the metal leaching of the catalyst that the metal leaching of the Cu/Al ₂ O ₃ catalyst during use is very small (less than 2ppb), indicating that the catalyst is firmly fixed on the surface of the carrier. This result explains well Its continuous catalytic performance.

Example 5:

Add 75ml of humic acid, oxalic acid and acetic acid mixed solution into the glass reactor, adjust each parameter of the O ₃ generator to the set value, generate O ₃ at a flow rate of 40ml/min, and connect the reactor gas after the gas flow is stable for 2 minutes At the entrance, start timing, and seal it to carry out the oxidation reaction. At this time, it is regarded as 0 time. Carry out catalytic ozonation treatment under the following conditions:

Reaction target solution volume: 75ml

Reaction target solution concentration: humic acid 20mg/L (DOC), oxalic acid and acetic acid 20mg/L each

Reaction target solution temperature: 20°C

O ₃ generation concentration: 12.2mg/L/min

Catalytic material: a cylindrical material formed by catalyst powder loaded on the surface of a honeycomb ceramic body

Sampling time points: 10min, 30min, 60min, 120min, 180min, and the corresponding TOC removal rates after treatment are shown in Table 5.

TOC removal rate after table 5 embodiment 5 treatment time (min) 10 30 60 120 180 TOC removal rate (%) non-catalytic 2.3 4.8 10.6 15.9 16.2 catalytic 11.0 31.9 43.6 52.8 65.7

From the results in Table 5, it can be seen that for humic acid, oxalic acid and acetic acid that are extremely difficult to be mineralized and removed by various oxidation methods, this Cu/Al ₂ O ₃ catalytic ozonation method has obvious advantages, and can combine several The mixed TOC removal rate of the substance is increased by about 50%. If the catalytic ozonation time is long enough, it should be able to remove all the TOC and achieve complete mineralization.

Embodiment 6:

Add 75ml of alachlor solution into a glass reactor with a volume of 100ml, adjust each parameter of the O ₃ generator to the set value, generate O ₃ at a flow rate of 40ml/min, and connect the reactor gas after the gas flow is stable for 2 minutes At the entrance, start timing, and seal it to carry out the oxidation reaction. At this time, it is regarded as 0 time. Carry out catalytic ozonation treatment under the following conditions:

Reaction target solution volume: 75ml

Reaction target solution concentration: Alachlor: 100mg/L, TOC: 60mg/L

Reaction target solution temperature: 20°C

Reaction solution system: 0.001M phosphate buffer solution

Solution initial pH: 7.00

O ₃ generation concentration: 12.2mg/L/min

Catalytic material: catalyst particles (dosing amount: 250mg/L)

Sampling time points: 10min, 30min, 60min, 120min, 180min, alachlor and corresponding TOC removal rate after treatment are shown in Table 6.

Table 6 Example 6 Alachlor and TOC removal rate after treatment time (min) 10 30 60 120 180 Alachlor removal rate (%) non-catalytic 52.3 85.6 90.5 91.4 92.8 catalytic 66.5 96.7 96.9 97.8 98.0 TOC removal rate (%) non-catalytic 4.61 21.4 31.4 38.6 49.3 catalytic 4.91 30.8 45.2 68.3 72.4

From the results in Table 6, it can be seen that when the catalyst is added in the state of particles, it can also achieve a relatively obvious catalytic effect, but it is slightly lower than that applied in the state of supported solid. The disadvantage of particle dosing is that it is difficult to separate the treated catalyst.

Embodiment 7:

Add 1200ml of alachlor solution into a stainless steel reactor with a volume of 1400ml, adjust each parameter of the O ₃ generator to the set value, generate O ₃ at a flow rate of 40ml/min, and connect the reactor gas after the gas flow is stable for 2 minutes At the entrance, start timing, and seal it to carry out the oxidation reaction. At this time, it is regarded as 0 time. Carry out catalytic ozonation treatment under the following conditions:

Reaction target solution volume: 1200ml

Reaction target solution concentration: Alachlor: 100mg/L, TOC: 60mg/L

Reaction target solution temperature: 20°C

Reaction solution system: 0.001M phosphate buffer solution

Solution initial pH: 7.00

O ₃ generation concentration: 12.2mg/L/min

Catalytic material: a cylindrical material formed by catalyst powder loaded on the surface of a honeycomb ceramic body

Sampling time points: 10min, 30min, 60min, 120min, 180min, alachlor and corresponding TOC removal rate after treatment are shown in Table 7.

Table 7 Example 7 Alachlor and TOC removal rate after treatment time (min) 10 30 60 120 180 Alachlor removal rate (%) non-catalytic 50.1 82.3 88.2 92.5 93.7 catalytic 73.5 98.2 98.8 99.3 99.5 TOC removal rate (%) non-catalytic 5.45 23.8 35.2 40.0 50.7 catalytic 10.4 40.1 58.9 84.2 89.0

From the results in Table 7, it can be seen that in a stainless steel and slightly enlarged reactor, a good catalytic ozonation treatment effect can also be obtained, and the removal rate of alachlor and TOC is slightly higher than that of the glass reactor, which may be due to Because the titanium porous gas distribution system can obtain smaller, more uniform and more stable bubbles than the quartz sand porous gas distribution plate, the gas-liquid contact area is increased and the processing efficiency is improved.

Claims (3)

1. A reactor for efficient catalytic ozonation to remove organic pollutants in water, characterized in that a Cu/Al ₂ O ₃ catalyst is evenly loaded on the surface of the honeycomb ceramic body, as the core part of the catalytic ozonation reaction, in the reaction The catalytic ozonation reaction carried out in the device can completely mineralize the organic pollutants in the water. 2. According to the reactor according to claim 1, the solid Cu/Al ₂ O ₃ catalyst powder can be uniformly coated on the surface of the honeycomb ceramic body or other porous solid carriers in a single layer or multiple layers, with little dissolution, no falling off, and good resistance to ozonation. The reaction has a strong catalytic effect. 3. The reactor according to claim 1, characterized in that the quartz sand porous gas distribution system or titanium porous gas distribution plate at the bottom of the reactor makes the ozone gas more evenly distributed in the reaction solution.