Seawater bromine extraction device and method for producing bromine by coupling photoelectrocatalytic oxidation with resin adsorption

Abstract

The present application relates to a kind of seawater bromine extraction device and method for producing bromine by photoelectrocatalytic oxidation coupling resin adsorption method;Dissolved particles are removed from seawater by filtration pretreatment, into photoelectrocatalytic oxidation zone, add acid to adjust pH=4-5, then in the graphite plate cathode, tungsten carbide / cadmium sulfide photocatalyst supported platinum-based anode, catalytic oxidation reaction occurs under the joint action of visible light source, bromide ion becomes free bromine;Afterwards, seawater rich in free bromine enters resin adsorption column filled with D201 macroporous resin for adsorption, then water vapor is introduced into bromine-loaded resin to directly evaporate free bromine, and bromine is obtained by condensation, separation and refining process.The present application also provides a preparation method of tungsten carbide / cadmium sulfide photocatalyst with nanoflower ball microtopography.The present application effectively improves the oxidation and separation efficiency of bromine, while avoiding the use of strong acid and chlorine, making the seawater bromine extraction process more green and more efficient.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of seawater resource utilization; in particular, it relates to a seawater bromine extraction device and method for producing bromine by photoelectrocatalytic oxidation coupled with resin adsorption. BACKGROUND

[0002] Bromine is a very important fine chemical raw material and is widely used, playing an important role in the development of national economy and science and technology. The natural resources of bromine mainly exist in seawater, oil and gas field brine, underground brine, salt lake water and sedimentary rock salt mines of ancient oceans. The reserves of bromine in seawater are huge, about 99% of bromine on earth exists in seawater. Using seawater and concentrated seawater produced by seawater desalination as the main bromine extraction raw material can not only provide a new bromine source for China's bromine production industry, but also greatly reduce the pollution caused by the direct discharge of by-product concentrated seawater, which has great significance for the resource utilization of seawater.

[0003] The current widely used industrial bromine extraction methods are steam distillation and air blowing. The steam distillation method mainly uses high-grade bromine-containing brine as raw material (brine containing bromine of more than 3000 g / m3). The main process of the method is to pass Cl2 into the reaction tower to oxidize Br-in the preheated acidified brine into Br2, and then pass the oxidized liquid into the distillation tower. In the distillation tower, Br2 is volatilized with water vapor under certain pressure and temperature, and then sent to the condenser for condensation to obtain crude bromine containing a small amount of water and chlorine. After rectification, refined bromine is obtained. Too high or too low chlorine ratio will negatively affect the yield or quality of bromine; the temperature of the distillation tower outlet must be strictly controlled during the distillation process. Too high temperature will increase the water content in the crude bromine, and too low temperature will reduce the yield of bromine due to incomplete evaporation. The steam distillation method is only economical when the raw material contains a high amount of bromine. As the bromine content of the raw material decreases, the steam consumption increases rapidly, and the production cost of bromine rises. In addition, the high operating temperature during bromine evaporation will cause many side reactions, such as the hydrolysis of free bromine, the oxidation of free bromine to bromate ions by excess chlorine, or the formation of bromine chloride with chlorine, which will affect the quality of the product and reduce the oxidation rate and blowing rate of the process. The main principle of the air blowing method is that after the bromine-containing liquid is acidified and Cl2 is introduced, Br-in the liquid is oxidized to Br2, and then the oxidized liquid is introduced into the blowing tower and dripped from the top. Compressed air is introduced from the bottom to blow out the Br2 in the liquid and send it to the absorption tower, and then an appropriate absorbent is used for absorption to separate and concentrate bromine from the brine. According to the different absorbents, the air blowing method can be divided into air blowing acid liquid absorption method and air blowing alkali liquid absorption method. The acidification and oxidation processes of the two processes are similar, except for the use of different absorbents and post-processing steps. In the former, H2SO3 acid mist is used in the absorption tower to absorb the blown-out Br2, which is reduced to HBr. Then Cl2 is introduced into the HBr-rich absorption completion liquid to convert Br-into Br2. Finally, through the stripping action of water vapor, crude bromine is obtained after concentration and condensation. In the latter, alkali (such as NaOH) is used as the absorbent, and NaOH reacts with Br2 to form sodium bromide and sodium bromate. After absorption, the bromine is re-freed by adding sulfuric acid to the absorption liquid, and then water vapor distillation, condensation and separation are used to obtain bromine. The air blowing method has the disadvantages of high energy consumption, large equipment, high investment, low resource utilization rate, great influence of local climate such as temperature on bromine production, easy occurrence of tower blocking phenomenon caused by calcium sulfate crystallization, and impurities such as mud and sand. SUMMARY

[0004] In order to solve the problems of the prior art, the method innovatively uses photoelectrocatalytic oxidation coupled with resin adsorption to produce bromine, which can not only shorten the process flow and improve the oxidation efficiency, but also solve the problems of low efficiency and acid pollution in the current seawater acidification oxidation reaction system, and is expected to realize large-scale production.

[0005] The application is a seawater bromine extraction method for producing bromine by photoelectrocatalytic oxidation coupled with resin adsorption, and tungsten carbide / cadmium sulfide (WC / CdS) photocatalyst is applied to seawater photoelectrocatalysis for the first time, and a new simple preparation method of WC / CdS nanoflower ball photocatalyst is provided. In order to better implement the method, a seawater bromine extraction device for producing bromine by photoelectrocatalytic oxidation coupled with resin adsorption is also invented, which is composed of a photoelectrocatalytic oxidation device and a resin adsorption device. The photoelectrocatalytic oxidation is generally applied to the degradation of organic pollutants in wastewater, and the application is the first to apply photoelectrocatalysis to seawater bromide ion oxidation. The photoelectrocatalytic oxidation method is coupled with the existing resin adsorption method to achieve excellent bromine extraction efficiency and realize the green environmental protection of the process.

[0006] The specific technical solutions of the application are as follows:

[0007] A seawater bromine extraction method for producing bromine by photoelectrocatalytic oxidation coupled with resin adsorption; under the conditions of light, photocatalyst and electrode, bromide ions in seawater are oxidized into bromine, and the oxidized seawater enters resin adsorption, and the resin is regenerated by steam stripping while bromine is concentrated and separated, to obtain bromine.

[0008] The seawater filtered and pretreated to remove insoluble particles enters a photoelectrocatalytic oxidation zone, and acid is added to adjust pH to 4-5, then catalytic oxidation reaction occurs under the joint action of a graphite plate cathode, a platinum-based anode loaded with tungsten carbide / cadmium sulfide photocatalyst and a visible light source, and bromide ions become free bromine; then the seawater rich in free bromine enters a resin adsorption column filled with D201 macroporous resin for adsorption, and water vapor is introduced into the bromine-loaded resin to directly steam out the free bromine, and the steamed-out liquid is subjected to condensation, separation and refining processes to obtain bromine.

[0009] The catalyst is a tungsten carbide / cadmium sulfide photocatalyst with nanoflower ball micro-morphology.

[0010] The catalyst preparation method is as follows:

[0011] 1) Add cadmium acetate and thiourea to a mixed solution of diethylene triamine and ethanol, stir and dissolve to form a cadmium sulfide suspension;

[0012] 2) Add tungsten carbide powder to a mixed solution of diethylene triamine and ethanol, and ultrasonically disperse to form a tungsten carbide suspension;

[0013] 3) The tungsten carbide suspension obtained in step 2) is added dropwise into the cadmium sulfide suspension obtained in step 1) to obtain a mixed suspension; the mixed suspension is reacted in a polytetrafluoroethylene-lined autoclave; after the reaction is completed, the light yellow product is collected by centrifugation, washed with deionized water and ethanol, and dried in vacuum to obtain a tungsten carbide / cadmium sulfide photocatalyst with nanoflower ball microtopography.

[0014] The molar ratio of cadmium acetate to thiourea in step 1) is 1:5.

[0015] The volume ratio of diethylenetriamine to ethanol is 2:1.

[0016] The mass ratio of the amount of tungsten carbide powder added in step 2) to the cadmium sulfide generated in step 1) is 0.5-5:100.

[0017] The seawater device for producing bromine by photoelectrocatalytic oxidation coupling resin adsorption method comprises a photoelectrocatalytic oxidation device and a resin adsorption device; the photoelectrocatalytic oxidation device is composed of a graphite plate cathode, a platinum-based anode loaded with tungsten carbide / cadmium sulfide photocatalyst, and a visible light source; the graphite plate cathode is connected to the negative electrode of a direct current stabilized power supply, and the platinum-based anode loaded with the photocatalyst is connected to the positive electrode of the direct current stabilized power supply; the visible light source directly irradiates the platinum-based anode loaded with the photocatalyst, and the visible light source and the anode are required to be at the same height, and the reaction container at the same height is made of transparent material; a drain is arranged below the photoelectrocatalytic reaction device and is connected to the resin adsorption device by a water pump; the resin adsorption device comprises a seawater storage tank, and the seawater storage tank is connected to an adsorption column filled with D201 macroporous resin; a waste liquid outlet and a steam inlet are arranged below the adsorption column, and an oxidized seawater inlet, a steam outlet, and a bromine water reflux inlet are arranged above the adsorption column; the steam outlet is connected to a condensation separation tank, the condensation separation tank is provided with a bromine water reflux port on the side and is connected to the bromine water reflux inlet above the adsorption column; a crude bromine outlet is arranged below the condensation separation tank and is connected to a crude bromine storage tank; a bromine refining device is connected to the outlet of the crude bromine storage tank, and finally connected to a refined bromine storage tank.

[0018] Seawater enters the photoelectrocatalytic oxidation device, and bromide ions in the seawater are oxidized into free bromine; the oxidized seawater enters the resin adsorption device, first enters the seawater storage tank, and then enters the adsorption column filled with D201 macroporous resin to adsorb free bromine; then the steam stripping method is used to regenerate the resin and separate and concentrate bromine; the steam-out liquid passes through the condensation separation tank, then enters the crude bromine storage tank, and then is refined to obtain refined bromine.

[0019] The prepared WC / CdS nanoflower ball photocatalyst is ground into powder and fixed on a platinum electrode sheet; the platinum electrode with the fixed catalyst is used as a working electrode, and a direct current stabilized power supply is applied under the irradiation of a xenon lamp light source.

[0020] Sulfuric acid is added to adjust pH to 4-5; the resin adsorption column filled with D201 macroporous resin is used for adsorption with a maximum adsorption capacity of 30 kg / m 3 .

[0021] The seawater bromine extraction method for producing bromine by photoelectrocatalytic oxidation coupled with resin adsorption is a method for oxidizing bromide ions in seawater into bromine under the conditions of light, photocatalyst and electrode, and then the oxidized seawater is subjected to resin adsorption, and the resin is regenerated by steam stripping while concentrating and separating bromine to obtain high-concentration bromine. The specific steps are shown in Figure 1 The seawater after filtration pretreatment to remove insoluble particles is introduced into a photoelectrocatalytic oxidation zone, sulfuric acid is added to adjust pH to 4-5, and then catalytic oxidation reaction occurs under the joint action of a graphite plate cathode, a platinum-based anode loaded with WC / CdS photocatalyst and a visible light source, and bromide ions are converted into free bromine. Subsequently, the seawater rich in free bromine is introduced into a resin adsorption column filled with D201 macroporous resin for adsorption (the maximum adsorption capacity of the resin is 30 kg / m 3 ), and then water vapor is introduced into the bromine-loaded resin to directly strip the free bromine, and the stripped liquid is subjected to condensation, separation and refining processes to obtain refined bromine.

[0022] The core of the photoelectrocatalytic oxidation technology is the research and development of high-efficiency photocatalyst, and the present application provides a WC / CdS photocatalyst with unique nanoflower ball micro-morphology, and the morphology diagram is shown in Figure 2 .

[0023] In order to better implement the method, a seawater bromine extraction device for producing bromine by photoelectrocatalytic oxidation coupled with resin adsorption is also invented, which is composed of a photoelectrocatalytic oxidation device and a resin adsorption device. The photoelectrocatalytic oxidation device is composed of a graphite plate cathode, a platinum-based anode loaded with WC / CdS photocatalyst and a visible light source. The graphite plate cathode is connected to the negative electrode of a direct current stabilized power supply, and the platinum-based anode loaded with photocatalyst is connected to the positive electrode of the direct current stabilized power supply. The visible light source directly irradiates on the platinum-based anode loaded with photocatalyst, and the visible light source and the anode are required to be at the same height, and the reaction vessel at the same height is made of transparent material to facilitate direct irradiation of the light source. A drainage port is arranged below the photoelectrocatalytic reaction device and is connected to the resin adsorption device by a water pump. First connected is a seawater storage tank, and then connected is an adsorption column filled with D201 macroporous resin, and a waste liquid outlet and a steam inlet are left below the adsorption column, and an oxidized seawater inlet, a steam outlet and a bromine water reflux inlet are left above the adsorption column. The steam outlet is connected to a condensation and separation tank. A bromine water reflux port is arranged on the side of the condensation and separation tank and is connected to the bromine water reflux inlet above the adsorption column. A crude bromine outlet is arranged below the condensation and separation tank and is connected to a crude bromine storage tank. A bromine refining device is connected to the outlet of the crude bromine storage tank, and after a series of refining means, it is finally connected to a refined bromine storage tank, and a device schematic diagram is shown in Figure 3 .

[0024] The device operation sequentially comprises the following steps: the seawater after simple pretreatment enters the photoelectrocatalytic oxidation device, sulfuric acid is added to adjust pH to 4-5, bromide ions in the seawater are oxidized into free bromine, the seawater after oxidation enters the resin adsorption device, first enters a seawater storage tank, then enters an adsorption column filled with D201 macroporous resin, and adsorption of free bromine is carried out (the maximum adsorption capacity of the resin is 30 kg / m 3 ), then the resin is regenerated by using steam stripping method, and at the same time, bromine is concentrated and separated, the steam out of the process enters a condensation separation tank, then enters a crude bromine storage tank, and then, through a series of refining means, refined bromine is obtained.

[0025] The pretreatment is carried out by using a filtration method, and the purpose is to remove insoluble particles in the seawater.

[0026] The photoelectrocatalytic reaction needs to add sulfuric acid to adjust pH to 4-5.

[0027] The photoelectrocatalytic oxidation needs WC / CdS photocatalyst, and the preparation method is as described above.

[0028] The photoelectrocatalytic oxidation zone is composed of a graphite plate cathode, a platinum-based anode loaded with WC / CdS photocatalyst, and a visible light source. The platinum electrode loaded with WC / CdS photocatalyst is prepared by grinding the prepared WC / CdS nanoflower ball photocatalyst into powder and fixing it on a platinum electrode sheet. The platinum electrode with the fixed catalyst serves as a working electrode, and under the irradiation of a xenon lamp light source, a direct current stabilized power supply is applied. This process is mainly to solve the problem of bromide ion oxidation efficiency.

[0029] The resin desorption and regeneration is carried out by using a water vapor stripping method, water vapor is introduced into the bromine-loaded resin to strip out free bromine, so as to realize separation of bromine and regeneration of the resin.

[0030] The method for oxidizing bromide ions in seawater provided by the application greatly improves the efficiency of bromide ion oxidation, and provides a new idea and method for seawater bromine extraction.

[0031] The method provided by the application constructs a photoelectrocatalytic oxidation coupled resin adsorption method for producing bromine, effectively improves the oxidation and separation efficiency of bromine, and the seawater bromine extraction device for producing bromine by the photoelectrocatalytic oxidation coupled resin adsorption method has an oxidation rate of more than 95% and a resin adsorption rate and elution rate of more than 90% for seawater containing high, medium and low bromide ion concentrations. It is far higher than the existing chlorine oxidation process with an oxidation efficiency of 80%, effectively improves the oxidation and separation efficiency of bromine, and avoids the use of strong acid and chlorine, so that the seawater bromine extraction process is more green and more efficient. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 : Process flow chart of bromine production by photoelectrocatalytic oxidation coupled with resin adsorption method

[0033] Figure 2 : Scanning electron microscope (SEM) image of WC / CdS nanoflower ball photocatalyst

[0034] Figure 3 : Schematic diagram of seawater bromine extraction device for bromine production by photoelectrocatalytic oxidation coupled with resin adsorption method

[0035] Wherein: 1. pH detector, 2. reaction vessel, 3. direct current stabilized power supply, 4. graphite plate cathode, 5. WC / CdS photocatalyst loaded platinum-based anode, 6. visible light source, 7. pump, 8. resin adsorption column, 9. condensation separation tank, 10. seawater storage tank after acidification and oxidation, 11. D201 macroporous resin, 12. crude bromine storage tank, 13. bromine refining device, 14. refined bromine storage tank. DETAILED DESCRIPTION

[0036] The preparation of the photocatalyst, the catalytic effect and the operation effect of the device will be further described below in combination with typical examples.

[0037] The photoelectrocatalytic oxidation zone is composed of a graphite plate cathode, a WC / CdS photocatalyst loaded platinum-based anode and a visible light source. The prepared WC / CdS nanoflower ball photocatalyst is ground into powder and fixed on a platinum electrode sheet. The platinum electrode with the fixed photocatalyst serves as a working electrode. Under the irradiation of a xenon lamp light source, a direct current stabilized power supply is applied.

[0038] The seawater bromine extraction method for bromine production by photoelectrocatalytic oxidation coupled with resin adsorption method refers to the oxidation of bromide ions in seawater into bromine under the conditions of light, photocatalyst and electrode. The oxidized seawater enters resin adsorption, and then the resin is regenerated by steam stripping, which is also the concentration and separation of bromine, to obtain high-concentration bromine. The process flow is shown in Figure 1 The seawater raw material is first pretreated, then subjected to photoelectrocatalytic oxidation, and then subjected to resin adsorption. The resin is desorbed by steam stripping, and then the target product refined bromine is obtained through condensation, separation and refining. The specific steps are as follows: seawater after filtration pretreatment to remove insoluble particles enters the photoelectrocatalytic oxidation zone, sulfuric acid is added to adjust pH = 4-5, then catalytic oxidation reaction occurs under the joint action of graphite plate cathode, tungsten carbide / cadmium sulfide (WC / CdS) photocatalyst loaded platinum-based anode and visible light source, bromide ions become free bromine. The seawater rich in free bromine then enters the resin adsorption column filled with D201 macroporous resin for adsorption (the maximum adsorption capacity of the resin is 30 kg / m 3 ), then water vapor is introduced into the bromine-loaded resin to directly strip out the free bromine, and the stripped liquid is subjected to condensation, separation and refining processes to obtain refined bromine.

[0039] The core of photoelectrocatalytic oxidation technology is the research and development of high-efficiency photocatalyst, and the application provides a novel simple preparation method of WC / CdS photocatalyst with unique nanoflower ball micro morphology.

[0040] 1) cadmium acetate and thiourea (molar ratio 1:5) are added into a mixed solution of diethylene triamine and ethanol (volume ratio 2:1), and after stirring and dissolving, cadmium sulfide (molar amount equal to that of cadmium acetate) is generated to form a cadmium sulfide suspension;

[0041] 2) tungsten carbide powder (tungsten carbide powder is added in an amount of 0.5-5:100 of the mass ratio of the cadmium sulfide generated in step 1) is added into a mixed solution of diethylene triamine and ethanol (volume ratio 2:1) to be ultrasonically dispersed to form a tungsten carbide suspension;

[0042] 3) the tungsten carbide suspension obtained in step 2) is added dropwise into the cadmium sulfide suspension obtained in step 1) to obtain a mixed suspension; the mixed suspension is sealed in a polytetrafluoroethylene-lined autoclave for reaction; after the reaction is completed, the light yellow product is collected by centrifugation, washed with deionized water and ethanol, and vacuum dried to obtain the WC / CdS photocatalyst with unique nanoflower ball micro morphology.

[0043] The device operation sequentially comprises the following steps: the seawater after simple pretreatment enters the photoelectrocatalytic oxidation device, sulfuric acid is added to adjust pH to 4-5, the bromide ions in the seawater are oxidized into free bromine, the oxidized seawater enters the resin adsorption device, first enters a seawater storage tank, then enters an adsorption column filled with D201 macroporous resin, and adsorption of free bromine is carried out (the maximum adsorption capacity of the resin is 30kg / m 3 ), then the resin is regenerated by steam stripping and bromine is concentrated and separated at the same time, the steam stripping liquid passes through a condensation separation tank, then enters a crude bromine storage tank, and then a series of refining methods are used to obtain refined bromine.

[0044] The photoelectrocatalytic oxidation zone is composed of a graphite plate cathode, a platinum-based anode loaded with the WC / CdS photocatalyst, and a visible light source. The platinum electrode loaded with the WC / CdS photocatalyst is prepared by grinding the prepared WC / CdS nanoflower ball photocatalyst into powder and fixing it on a platinum electrode sheet. The platinum electrode with the catalyst fixed thereon serves as a working electrode under the irradiation of a xenon lamp light source and an external direct-current stabilized power supply. This process is mainly to solve the problem of bromide ion oxidation efficiency.

[0045] The resin is D201 macroporous resin, and the maximum adsorption capacity of the resin is 30kg / m 3 .

[0046] The resin desorption and regeneration method uses steam distillation, where steam is passed into the bromine-supported resin to directly distill off the free bromine, thus achieving bromine separation and resin regeneration.

[0047] In Example 1, 0.52 g (2 mmol) of cadmium acetate and 0.76 g (10 mmol) of thiourea were added to 60 ml of a mixed solution of diethylenetriamine and ethanol in a volume ratio of 2:1. After stirring and dissolving, 0.29 g (2 mmol) of cadmium sulfide (CdS) was generated, forming a cadmium sulfide suspension. 0.0015 g (WC / CdS = 0.5:100 = 0.5%) and 0.0029 g of cadmium sulfide were then added to the solution.

[0048] (WC / CdS=1.0:100=1.0%), 0.0087g (WC / CdS=3.0:100=3.0%), 0.0145g

[0049] Tungsten carbide (WC) was added to a 2:1 (WC / CdS = 5.0:100 = 5.0%) mixed solution of diethylenetriamine and ethanol in 60 ml of water and sonicated for 3 h to disperse and form a tungsten carbide suspension. The tungsten carbide suspension was then added dropwise to a cadmium sulfide suspension to obtain a mixed suspension. This mixed suspension C was sealed in a polytetrafluoroethylene-lined autoclave and reacted at 80 °C for 48 h. After the reaction, the pale yellow product was collected by centrifugation, washed three times with deionized water and ethanol, and vacuum dried at 60 °C to obtain a WC / CdS photocatalyst with a unique nano-flower-like microstructure. Depending on the amount of WC added, the resulting composite photocatalyst was named xwt.%WC / CdS (the ratio of tungsten carbide mass to cadmium sulfide mass), where x was 0.5, 1, 3, or 5. The photocatalysts with different WC contents were applied to the photocatalytic oxidation of bromide ions in seawater. 50 ml of seawater (bromine ion concentration 60 mg / ml) was placed in a 50 ml U-shaped electrolytic cell. 30 mg of photocatalyst was loaded onto a platinum-based anode, and a graphite plate was used as the cathode. The anode and cathode were connected to the positive and negative terminals of a DC regulated power supply, respectively. Then, a xenon lamp equipped with an ultraviolet cutoff filter (λ>420 nm) was turned on, and condensate was introduced to maintain the reaction system at 20°C. The reaction was carried out for 2 hours, and the results were analyzed after the reaction was completed. The oxidation rate data of different WC / CdS photocatalysts applied to the photoelectrocatalytic oxidation of bromide ions in seawater are shown in Table 1.

[0050] Table 1. Effects of different catalysts on the oxidation of bromide ions in seawater.

[0051]

[0052] As can be seen from the examples, the prepared WC / CdS photocatalyst has a good effect on the photoelectrocatalytic oxidation of bromide ions.

[0053] The seawater bromine extraction device for producing bromine by photoelectrocatalytic oxidation coupling resin adsorption method comprises a photoelectrocatalytic oxidation device and a resin adsorption device; the photoelectrocatalytic oxidation device is composed of a graphite plate cathode 4, a WC / CdS photo catalyst loaded platinum-based anode 5 and a visible light source 6; the graphite plate cathode 4 is connected to the negative pole of a direct current stabilized power supply 3, and the photo catalyst loaded platinum-based anode 5 is connected to the positive pole of the direct current stabilized power supply 3; the visible light source 6 directly irradiates on the photo catalyst loaded platinum-based anode 5, and the visible light source 6 and the anode 5 are required to be at the same height, and the reaction container at the same height is made of transparent material, so that the light source directly irradiates. A drainage port is arranged below the photoelectrocatalytic reaction device, and is connected to the resin adsorption device through a water pump 7; the resin adsorption device comprises a seawater storage tank 10, the seawater storage tank 10 is connected to an adsorption column 8 filled with D201 macroporous resin, and a waste liquid outlet and a steam inlet are arranged below the adsorption column, and an oxidized seawater inlet, a steam outlet and a bromine water reflux inlet are arranged above the adsorption column; the steam outlet is connected to a condensation separation tank 9, the condensation separation tank is provided with a bromine water reflux port on the side, and is connected to the bromine water reflux inlet above the adsorption column; a crude bromine outlet is arranged below the condensation separation tank, and is connected to a crude bromine storage tank 12; a bromine refining device 13 is connected to the outlet of the crude bromine storage tank, and is finally connected to a refined bromine storage tank 14.

[0054] When the device is running, seawater from which insoluble particles are removed through pretreatment is introduced into the photoelectrocatalytic oxidation area 2, sulfuric acid is first added to adjust the pH to 4-5, and then catalytic oxidation reaction occurs under the joint action of the graphite plate cathode 4, the WC / CdS photo catalyst loaded platinum-based anode 5 and the visible light source 6, and bromide ions become free bromine. After that, seawater rich in free bromine flows into the acidified and oxidized seawater storage tank 10, and then enters the resin adsorption column 8 filled with D201 macroporous resin 11, and adsorption of free bromine is carried out, then water vapor is introduced into the bromine-loaded resin to directly evaporate the free bromine, and the evaporated liquid reaches the condensation separation tank 9, and then refined bromine is obtained through separation and refining processes.

[0055] Example 2 uses the above treatment device to treat seawater containing bromine, the concentration of bromide ions is 20 mg / L, sulfuric acid is added to adjust the pH to 5, the photoelectrocatalytic oxidation reaction time is 1 h, the power of the visible light source is 500 W, and the oxidation rate of bromide ions is about 96%. The oxidized seawater is subjected to resin adsorption, and the flow rate is controlled at 4 BV / h. The concentration of free bromine in the effluent is detected, and no free bromine is detected in the first two hours. After 5 h of adsorption, the resin is subjected to steam elution, and the adsorption rate and the elution rate are both greater than 90%.

[0056] Example 3: The seawater containing bromine ions with a concentration of 60-70 mg / L was treated by the above-mentioned treatment device, sulfuric acid was added to adjust the pH to 4.5, the photoelectrocatalytic oxidation reaction time was 2 h, the visible light source power was 500 W, and the oxidation rate of bromine ions was about 98%. The oxidized seawater entered the resin adsorption, the flow rate was controlled at 4 BV / h, and the free bromine concentration of the effluent was detected. No free bromine was detected in the first two hours. The resin after 3 h of adsorption was subjected to steam elution, and the adsorption rate and elution rate were both greater than 90%.

[0057] Example 4: The seawater containing bromine ions with a concentration of 200 mg / L was treated by the above-mentioned treatment device, sulfuric acid was added to adjust the pH to 4, the photoelectrocatalytic oxidation reaction time was 3 h, the visible light source power was 500 W, and the oxidation rate of bromine ions was about 95%. The oxidized seawater entered the resin adsorption, the flow rate was controlled at 4 BV / h, and the free bromine concentration of the effluent was detected. No free bromine was detected in the first two hours. The resin after 2 h of adsorption was subjected to steam elution, and the adsorption rate and elution rate were both greater than 90%.

[0058] As can be seen from the examples, the seawater bromine extraction device for producing bromine by photoelectrocatalytic oxidation coupled with resin adsorption has an oxidation rate of more than 95% and a resin adsorption rate and elution rate of more than 90% for seawater containing high, medium and low concentrations of bromine ions. This far exceeds the oxidation efficiency of 80% of the existing chlorine oxidation process, effectively improves the oxidation and separation efficiency of bromine, and avoids the use of strong acid and chlorine, making the seawater bromine extraction process more green and more efficient.

[0059] The technical solutions disclosed and presented in the present application can be implemented by referring to the content of the present application, appropriately changing the conditions and routes, etc. Although the methods and preparation techniques of the present application have been described by preferred examples, relevant technical personnel can obviously modify or recombine the methods and technical routes described in the present application without departing from the content, spirit and scope of the present application, to realize the final preparation technique. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art, and they are considered to be included in the spirit, scope and content of the present application.

Claims

1. A method for bromine extraction from seawater using photoelectrocatalytic oxidation coupled resin adsorption; characterized in that, Under conditions of light, photocatalyst, and electrode presence, acid is added to adjust the pH to 4-5, oxidizing bromide ions in seawater to elemental bromine. The oxidized seawater then enters the resin for adsorption. The resin is regenerated by steam stripping, and bromine is concentrated and separated to obtain bromine. The catalyst is a tungsten carbide / cadmium sulfide photocatalyst with a nano-flower-like microstructure.

2. The seawater bromine extraction method for producing bromine by photoelectrocatalytic oxidation coupled resin adsorption as described in claim 1; characterized in that: Seawater, after being pretreated by filtration to remove insoluble particles, enters the photoelectrocatalytic oxidation zone. Acid is added to adjust the pH to 4-5. Then, under the combined action of a graphite cathode, a platinum-based anode supported by a tungsten carbide / cadmium sulfide photocatalyst, and a visible light source, a catalytic oxidation reaction occurs, converting bromide ions into free bromine. Subsequently, the seawater rich in free bromine enters a resin adsorption column filled with D201 macroporous resin for adsorption. Water vapor is then passed through the bromine-supported resin to directly distill off the free bromine. The distillate undergoes condensation, separation, and purification processes to obtain bromine.

3. The seawater bromine extraction method for producing bromine by photoelectrocatalytic oxidation coupled resin adsorption as described in claim 1; characterized in that, Includes the following steps: 1) Add cadmium acetate and thiourea to a mixed solution of diethylenetriamine and ethanol, stir to dissolve, and a cadmium sulfide suspension is generated. 2) Add tungsten carbide powder to a mixed solution of diethylenetriamine and ethanol and sonicate until dispersed to form a tungsten carbide suspension; 3) The tungsten carbide suspension obtained in step 2) is added dropwise to the cadmium sulfide suspension obtained in step 1) to obtain a mixed suspension; the mixed suspension is sealed in a high-pressure reactor lined with polytetrafluoroethylene for reaction; after the reaction is completed, the pale yellow product is collected by centrifugation, washed with deionized water and ethanol, and vacuum dried to obtain a tungsten carbide / cadmium sulfide photocatalyst with a nano-flower-like microstructure.

4. The seawater bromine extraction method for producing bromine by photoelectrocatalytic oxidation coupled resin adsorption as described in claim 3; characterized in that, Step 1) The molar ratio of cadmium acetate to thiourea is 1:

5.

5. The seawater bromine extraction method for producing bromine by photoelectrocatalytic oxidation coupled resin adsorption as described in claim 3; characterized in that, In steps 1) and 2), the volume ratio of diethylenetriamine to ethanol is 2:

1.

6. The seawater bromine extraction method for producing bromine by photoelectrocatalytic oxidation coupled resin adsorption as described in claim 3; characterized in that, The mass ratio of tungsten carbide powder added in step 2) to cadmium sulfide generated in step 1) is 0.5~5:

100.

7. A seawater bromine extraction apparatus for producing bromine using the photoelectrocatalytic oxidation coupled resin adsorption method of claim 1, characterized in that, The system includes a photoelectrocatalytic oxidation device and a resin adsorption device. The photoelectrocatalytic oxidation device consists of a graphite cathode, a platinum-based anode supported on a tungsten carbide / cadmium sulfide photocatalyst, and a visible light source. The graphite cathode is connected to the negative terminal of a DC regulated power supply, and the platinum-based anode supported on the photocatalyst is connected to the positive terminal of the DC regulated power supply. The visible light source directly illuminates the platinum-based anode supported on the photocatalyst, requiring the visible light source to be at the same height as the anode, and the reaction container at the same height to be made of transparent material. A drain outlet is located at the bottom of the photoelectrocatalytic reaction device, which is connected to the resin adsorption device via a water pump. The resin adsorption device includes a seawater storage tank, which is connected to an adsorption column filled with D201 macroporous resin. The adsorption column has a waste liquid outlet and a steam inlet at the bottom, and an oxidation seawater inlet, a steam outlet, and a bromine water reflux inlet at the top. The steam outlet is connected to a condensation separation tank, which has a bromine water reflux outlet on its side, connected to the bromine water reflux inlet above the adsorption column. A crude bromine outlet is located at the bottom of the condensation separation tank, connected to a crude bromine storage tank. A bromine purification device is connected to the outlet of the crude bromine storage tank, which is finally connected to a refined bromine storage tank.

8. The apparatus as claimed in claim 7, characterized in that, Seawater enters the photoelectrocatalytic oxidation device, where bromide ions are oxidized into free bromine. The oxidized seawater then enters the resin adsorption device, first into a seawater storage tank, and then into an adsorption column filled with D201 macroporous resin for the adsorption of free bromine. The resin is then regenerated by steam stripping, which also concentrates and separates the bromine. The distillate from this process passes through a condensation separation tank and then into a crude bromine storage tank. After a series of refining processes, refined bromine is obtained.

9. The apparatus as claimed in claim 7, characterized in that, The prepared WC / CdS nanoflower photocatalyst was ground into powder and fixed on a platinum electrode sheet. The platinum electrode with the catalyst fixed was used as the working electrode. Under the illumination of a xenon lamp light source, an external DC regulated power supply was applied.

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