DEVICE AND METHOD FOR DEGRADING CHLORINATED HYDROCARBONS IN POLLUTED GROUNDWATER

Abstract

The present disclosure relates to a device and method for degrading chlorinated hydrocarbon (CHC) in polluted groundwater. A preparation method for each of glass tubes and the method for degrading CHCs are as follows: uniformly mixing 55-85 wt % of Bi.sub.2O.sub.3, 5-15 wt % of B.sub.2O.sub.3, and 10-30 wt % of SrCO.sub.3, putting into a corrosion resistant crucible, holding at 1,050-1,300° C. for 15-45 min, forming into a glass tube, and holding the glass tube at 200-400° C. for 1-3 h, followed by annealing; soaking the inner wall of the glass tube for 10-30 min with a HCl solution with a concentration of 0.02-0.2 mol/L, washing with water, and providing an ultraviolet lamp to obtain a self-cleaning glass tube; guiding CHC-containing groundwater to the self-cleaning glass tube, turning on the ultraviolet lamp, and carrying out ultraviolet irradiation for 1-8 h, thereby effectively removing the CHCs.

Claims

1. A device for degrading chlorinated hydrocarbons (CHCs) in polluted groundwater, comprising: multiple Bi.sub.2O.sub.3—B.sub.2O.sub.3—SrCO.sub.3 system glass tubes connected in series and parallel, an ultraviolet lamp provided in each of the glass tubes and a control power supply provided outside the glass tubes, wherein the Bi.sub.2O.sub.3—B.sub.2O.sub.3—SrCO.sub.3 system glass tubes are prepared as follows: 1) preparation of the glass tube: uniformly mixing 55-85 wt % of Bi.sub.2O.sub.3, 5-15 wt % of B.sub.2O.sub.3, and 10-30 wt % of SrCO.sub.3, putting a resulting mixture into a corrosion resistant crucible and holding at 1,050-1,300° C. for 15-45 min, forming molten glass into a glass tube, and holding the glass tube at 200-400° C. for 1-3 h, followed by cooling and annealing, to obtain the glass tube; and 2) etching of a self-cleaning glass tube: soaking an inner wall of the glass tube for 10-30 min with an HCl solution having a concentration of 0.02-0.2 mol/L, washing with water, and providing an ultraviolet lamp in the glass tube to obtain the self-cleaning glass tube.

2. The device for degrading CHCs in polluted groundwater according to claim 1, wherein the glass tube has a length-to-diameter ratio of 20-50 and a wall thickness of 2-5 mm.

3. The device for degrading CHCs in polluted groundwater according to claim 2, wherein the ultraviolet lamp has a cylindrical shape; and a ratio of a diameter of the cylindrical ultraviolet lamp to an inner diameter of the glass tube ranges from 1:2 to 1:10.

4. The device for degrading CHCs in polluted groundwater according to claim 1, wherein the ultraviolet lamp has a power of 100-1,000 W/m.

5. A method for degrading chlorinated hydrocarbon (CHC) in polluted groundwater by using the device according to claim 1, comprising the following steps: A) assembly of the self-cleaning glass tubes: determining the number of parallel-connected glass tubes according to an amount of water, determining the number of series-connected glass tubes according to a CHC content in groundwater, and assembling the glass tubes into a self-cleaning glass tube kit; B) pollutant degradation: guiding the CHC-containing groundwater to the self-cleaning glass tubes, turning on the ultraviolet lamps and carrying out the pollutant degradation for 0.5-8 h, thereby removing the CHCs; and C) regeneration for catalytic performance of the self-cleaning glass tubes: re-etching the glass tubes for 1-10 min with the 0.02-0.2 mol/L HCl etchant, since catalytic performance of BiOCl growing on walls of the tubes becomes weak due to long-time irradiation, the pollutant degradation, and sediment accumulation on inner surfaces of the tubes, thereby recovering the catalytic performance of the self-cleaning glass tubes.

6. The method for degrading CHCs in polluted groundwater according to claim 5, wherein hydrogen peroxide is added in step B), and the hydrogen peroxide has a mass fraction of less than 0.5%.

7. The method for degrading CHCs in polluted groundwater according to claim 5, wherein the device is re-etched after continuous operation of 15-30 d in step C).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a schematic structural view of a device for degrading CHCs in polluted groundwater according to the present disclosure.

DETAILED DESCRIPTION OF THE IMPLEMENTATION EXAMPLES

[0025] The following describe the implementations of the present disclosure in detail with reference to the accompanying drawings and the examples. The following examples are implemented on the premise of the technical solutions of the present disclosure, with the detailed implementations and specific operation processes. However, the protection scope of the present disclosure is not limited to the following examples.

[0026] All agents and raw materials used in the present disclosure are commercially available or prepared according to methods in literature. In the following examples, the experimental methods in which specific conditions are not stated are generally carried out according to conventional conditions or according to the conditions recommended by the manufacturer.

Example 1 for Describing the Device for Degrading CHCs in Polluted Groundwater

[0027] FIG. 1 shows a structure of a single device. The device includes multiple Bi.sub.2O.sub.3—B.sub.2O.sub.3—SrCO.sub.3 system glass tubes 1 connected in series and parallel, an ultraviolet lamp 2 provided in each of the glass tubes and a control power supply 3 provided outside the glass tubes.

[0028] Each of the glass tubes 1 is internally hollow, and has a length-to-diameter ratio of 20-50 and a wall thickness of 2-5 mm. Only the basic structure of the device is shown in the FIGURE. As a matter of fact, there are further connectors provided in front and back as well as on the sidewall of the device to connect different glass tubes in series and parallel. The ultraviolet lamp 2 has a cylindrical shape. A ratio of a diameter of the cylindrical ultraviolet lamp to an inner diameter of the glass tube ranges from 1:2 to 1:10, and the ultraviolet lamp has a power of 100-1,000 W/m, all of which are specifically determined according to a length of the glass tube. The control power supply 3 is used to control the ultraviolet lamps 2.

[0029] The preparation method of the degradation device and the process and effect for degradation of the CHCs will be described respectively in Examples 2-4.

Example 2

[0030] 55 wt % of Bi.sub.2O.sub.3, 15 wt % of B.sub.2O.sub.3, and 30 wt % of SrCO.sub.3 were uniformly mixed, put into a corrosion resistant crucible and held at 1,050° C. for 45 min, molten glass was formed into a glass tube having a length-to-diameter ratio of 20 and a wall thickness of 5 mm, and the glass tube was held at 400° C. for 1 h, cooled and annealed to obtain a glass tube. The inner wall of the glass tube was soaked for 30 min with an HCl solution (i.e., an etchant) having a concentration of 0.02 mol/L and washed by water, and a cylindrical ultraviolet lamp was provided in the glass tube.

[0031] CHC polluted groundwater with a total CHC content of 10 mg/L was taken, the CHC-containing groundwater was guided to the self-cleaning glass tube, the ultraviolet lamp was turned on, and pollutant degradation was carried out. With irradiation of the ultraviolet lamp for 1 h, the total content of CHCs in the groundwater was 0.2 mg/L. After continuous operation of the reaction device for 30 d, the degradation rate of the CHCs declines. The 0.02 mol/L HCl etchant was used to etch the device for 10 min to recover the catalytic degradation performance of the device to the initial state.

Example 3

[0032] 70 wt % of Bi.sub.2O.sub.3, 10 wt % of B.sub.2O.sub.3, and 20 wt % of SrCO.sub.3 were uniformly mixed, put into a corrosion resistant crucible and held at 1,150° C. for 30 min, molten glass was formed into a glass tube having a length-to-diameter ratio of 35 and a wall thickness of 3 mm, and the glass tube was held at 300° C. for 2 h, cooled and annealed to obtain a glass tube. The inner wall of the glass tube was soaked for 20 min with a HCl solution (i.e., an etchant) having a concentration of 0.1 mol/L and washed by water, and a cylindrical ultraviolet lamp was provided in the glass tube.

[0033] CHC polluted groundwater with a total CHC content of 52 mg/L was taken, the CHC-containing groundwater was guided to the self-cleaning glass tube, the ultraviolet lamp was turned on, and pollutant degradation was carried out. With irradiation of the ultraviolet lamp for 4 h, the total content of CHCs in the groundwater was 2.8 mg/L. After continuous operation of the reaction device for 20 d, the degradation rate of the CHCs declines. The 0.1 mol/L HCl etchant was used to re-etch the device for 5 min to recover the catalytic degradation performance of the device to the initial state.

Example 4

[0034] 85 wt % of Bi.sub.2O.sub.3, 5 wt % of B.sub.2O.sub.3, and 10 wt % of SrCO.sub.3 were uniformly mixed, put into a corrosion resistant crucible and held at 1,300° C. for 45 min, molten glass was formed into a glass tube having a length-to-diameter ratio of 50 and a wall thickness of 2.5 mm, and the glass tube was held at 400° C. for 1 h, cooled and annealed to obtain a glass tube. The inner wall of the glass tube was soaked for 10 min with a HCl solution (i.e., an etchant) having a concentration of 0.2 mol/L and washed by water, and a cylindrical ultraviolet lamp was provided in the glass tube.

[0035] CHC polluted groundwater with a total CHC content of 215 mg/L was taken, 0.15 wt % of hydrogen peroxide was added to the CHC polluted groundwater, the CHC-containing groundwater was guided to the self-cleaning glass tube, the ultraviolet lamp was turned on, and pollutant degradation was carried out. With irradiation of the ultraviolet lamp for 8 h, the total content of CHCs in the groundwater was 1.2 mg/L. After continuous operation of the reaction device for 15 d, the degradation rate of the CHCs declines. The 0.2 mol/L HCl etchant was used to etch the device for 1 min to recover the catalytic degradation performance of the device to the initial state.

[0036] The preferred examples of the disclosure have been described in detail above, but the disclosure is not limited to these examples. Those skilled in the art can make various equivalent variations or substitutions without departing from the spirit of the disclosure, and these equivalent variations or substitutions are all included in the scope defined by the claims of this application.