Preparation of activated carbon modified adsorbent and application of activated carbon modified adsorbent in removing iodine in ionic membrane caustic soda raw material brine

Abstract

The invention relates to application of an activated carbon modified adsorbent to iodine removal in ionic membrane caustic soda raw material brine. The active carbon adsorbent is subjected to heteroatom modification and cyclodextrin grafting, so that the removal capacity of active carbon on trace iodine in ionic membrane caustic soda raw material brine is improved. According to the present invention, different nitrogen sources are adopted to modify the active carbon, and in the ionic membrane caustic soda raw material brine with the iodine initial concentration of 2.5 mg / L, the iodine removal rate of the pyridine-modified active carbon is 43.6%, and the iodine removal rate is increased by 11.2% compared with the non-modified active carbon; beta-cyclodextrin is grafted to the surface of pyridine modified activated carbon, the removal rate of iodine by the adsorbent is 73.2%, and compared with unmodified activated carbon, the removal rate of iodine is improved by 41.2%, and the adsorption performance is greatly improved. The invention provides an effective method for removing trace iodine in industrial ionic membrane caustic soda raw material brine, and has good economic benefit and operability.

Description

Technical Field

[0001] The invention relates to a method for removing trace iodine in salt water. Background Art

[0002] Caustic soda is one of the most basic chemical raw materials and is widely used in papermaking, detergents, petrochemical products and other fields. By the end of 2022, my country's annual total production capacity of caustic soda reached 39.8 million tons, making it the world's largest producer and consumer of caustic soda. At present, the main production methods of caustic soda are the diaphragm method and the ion membrane method. The diaphragm method is gradually being replaced by the ion membrane method due to its high energy consumption and severe environmental pollution.

[0003] The ion membrane method is the most advanced caustic soda production method at present. It has many advantages such as high concentration of liquid caustic soda, low comprehensive energy consumption and environmental pollution, and is adopted by many chlor-alkali manufacturers at home and abroad. However, the ion membrane caustic soda process has strict requirements on the content of iodine in the electrolytic brine. When the iodine content in the brine is higher than 0.2mg / L, once it enters the alkaline environment of the ion membrane, it can be oxidized to a high valence state and generate extremely insoluble Ba3H4(IO6)2 and other precipitations, which are deposited on the surface of the ion membrane, resulting in a decrease in current efficiency and shortening the service life of the ion membrane. At present, the ion membrane used in the ion membrane caustic soda device of my country mainly relies on imports and is expensive, so the shortening of the service life of the ion membrane will directly lead to an increase in the production cost of the enterprise. In view of this, it is very important for chlor-alkali enterprises to remove trace iodine in the brine to the maximum extent, and it is also a problem that the current salt and salt chemical industry urgently need to solve. Therefore, the research and development of trace iodine removal technology in the raw material brine of ion membrane caustic soda has great practical significance.

[0004] At present, the main methods for extracting iodine from brine include air blowing, ion exchange, adsorption (activated carbon method, starch method), solvent extraction, precipitation (copper method, silver method), electrolysis and new technology liquid membrane method. Among these methods, except for precipitation and electrolysis, most of them are based on the extraction of molecular iodine. The pretreatment principle of iodine in the raw material liquid is the same. From the perspective of process alone, ion exchange is more advanced. However, which method to use depends on many factors, so the above methods are applied to varying degrees.

[0005] The principle of the adsorption method is to use the advantages of the adsorbent such as being porous, having a large surface area, having good water filtration performance, and having strong adsorption properties, to adsorb iodine through the adsorbent, thereby achieving the effect of removing iodine. The adsorption method has attracted much attention from domestic researchers due to its simple process, low cost, clean and pollution-free. Huang Yuying conducted a preliminary study on the iodine removal performance of several domestic coal-based activated carbons, and the results showed that most activated carbons had good iodine removal effects. Wu Gang used hydrogen peroxide, sodium hypochlorite, chlorine, ferric chloride, sodium chlorate, etc. as oxidants, and activated carbon, molecular sieves, clay, diatomaceous earth, etc. as adsorbents, and reduced the iodine content from 0.21 mg / L to below 0.05 mg / L under acidic conditions. Gao Shubao used sodium nitrite as an oxidant and activated carbon fiber to remove iodine under pH 2-3 conditions, with an iodine removal rate of more than 90%. Although the adsorbent can reduce the iodine concentration to below 0.05 mg / L, the initial iodine concentration in the original brine is not high.

[0006] Although the reported use of adsorption to remove iodine has achieved good research results in the laboratory stage, our preliminary experimental results show that when saturated salt water is used to prepare iodine elemental solution for commercially available activated carbon to remove iodine, the adsorption capacity of the activated carbon drops sharply at the studied flow rate, and the iodine removal rate is only about 30%. It is speculated that this may be because chlorine and iodine belong to the same main group, and the presence of a large amount of chloride ions in the salt water seriously inhibits the selective adsorption capacity of activated carbon for iodine.

[0007] In summary, considering production cost, operation difficulty, environmental impact and many other aspects, adsorption method is currently the most suitable method for domestic chlor-alkali enterprises to remove trace iodine from ion membrane caustic soda raw material brine. However, the inhibitory effect of chloride ions in brine on the selective removal of iodine limits the specific application of this method in industry. Summary of the invention

[0008] The technical problem solved by the present invention is: to propose a method for removing trace iodine in ion-exchange membrane caustic soda raw material brine using a heteroatom-modified and grafted cyclodextrin adsorbent. The present invention performs heteroatom modification on commercially available activated carbon and grafts cyclodextrin to improve its iodine removal rate. The innovation of this method is that the activated carbon is modified by using pyridine, pyrrole, vitamin B1, EDTA, imidazole, quinoline, trichloroisocyanuric acid, etc., and cyclodextrin is grafted on the modified adsorbent to improve the activated carbon's ability to remove trace iodine in brine. In the ion-exchange membrane caustic soda raw material brine with an initial iodine concentration of 2.5 mg / L, the iodine removal rate of the activated carbon modified by pyridine is 43.6%, which is 11.2% higher than that of the unmodified activated carbon. β-cyclodextrin was grafted onto the surface of activated carbon. In the ion-exchange membrane caustic soda raw material brine with an initial iodine concentration of 2.5 mg / L, the iodine removal rate of the β-cyclodextrin grafted activated carbon was 46.7%, which was 14.3% higher than that of the unmodified activated carbon. When β-cyclodextrin was grafted onto the surface of the activated carbon modified by pyridine, the iodine removal rate of the adsorbent was 73.2%, which was 41.2% higher than that of the unmodified activated carbon, and the adsorption performance was greatly improved. The present invention provides a unique and effective method for removing trace iodine in the raw material brine of ion-exchange membrane caustic soda in industry.

[0009] In order to solve the technical problem of the present invention, the proposed technical solution is: a method for removing trace iodine in ion-exchange membrane caustic soda raw material brine using a heteroatom-modified and grafted cyclodextrin adsorbent, comprising the following steps:

[0010] (1) Place 100g of activated carbon in a beaker and add 500mL of deionized water; add 40mL of glacial acetic acid while stirring at room temperature, and continue stirring for 30min at a speed of 350rpm; weigh the required mass of modifier, the mass ratio of nitrogen content of the modifier to activated carbon is 2%-6%, and 40mL of 30% hydrogen peroxide, add them to the above beaker in sequence, continue stirring for 24h at room temperature and in the dark, filter, and dry in a 90℃ oven for 12-24h;

[0011] The modifier described in step (1) is any one of pyridine, pyrrole, vitamin B1, EDTA, imidazole, quinoline, and trichloroisocyanuric acid;

[0012] (2) placing the dried sample in a tube furnace, maintaining a nitrogen flow rate of 50 mL / min, heating the sample to 400-900°C at a heating rate of 5°C / min and calcining the sample for 2 h to obtain a modified adsorbent;

[0013] (3) 100 g of the adsorbent in step (2) was placed in a beaker, 500 mL of nitric acid was added, and stirring was continued at room temperature for 3 h at a speed of 150 rpm; the solid phase was filtered and separated, and the solid phase was repeatedly washed in distilled water until the pH value was 7.0, and the adsorbent was dried in an oven at 80 ° C for 4 h;

[0014] (4) 50 g of the adsorbent described in step (3) was mixed with 200 mL of DMF by ultrasonication, and 25 g of cyclodextrin and 1 mL of bifunctional linker HMDI were added after mixing. The mixture was placed in a round-bottom flask, and the mixture was heated in an oil bath at 70°C for 6 h under a nitrogen atmosphere and a rotation speed of 350 rpm, and filtered for separation;

[0015] (5) washing the adsorbent in step (4) with ethanol and pure water for multiple times, and drying in an oven at 80° C. for 4 h;

[0016] (6) The grafted adsorbent prepared in step (5) is used to remove trace iodine in the raw material brine of ion-exchange membrane caustic soda.

[0017] Preferably, the modifier in step (1) is pyridine.

[0018] Preferably, the calcination temperature in step (2) is 600°C.

[0019] Preferably, the mass ratio of the nitrogen content of the modifier to the activated carbon is 4%.

[0020] Preferably, the cyclodextrin in step (4) is β-cyclodextrin.

[0021] Preferably, the activated carbon in step (1) is in the shape of a column or a sheet, with a particle size of 4-6 mesh and a specific surface area of ​​1000-1200 m 2 / g.

[0022] Preferably, the method comprises the following steps:

[0023] (1) Place 100g of activated carbon in a beaker and add 500mL of deionized water; add 40mL of glacial acetic acid while stirring at room temperature, and continue stirring for 30min at a speed of 350rpm; weigh the required mass of modifier, the mass ratio of nitrogen content of the modifier to activated carbon is 4%, and 40mL of 30% hydrogen peroxide, add them to the above beaker in sequence, continue stirring for 24h at room temperature and in the dark, filter, and dry in a 90℃ oven for 12-24h;

[0024] The modifier described in step (1) is pyridine;

[0025] (2) placing the dried sample in a tube furnace, maintaining a nitrogen flow rate of 50 mL / min, heating to 600 °C at a heating rate of 5 °C / min and calcining for 2 h to obtain a modified adsorbent;

[0026] (3) 100 g of the adsorbent in step (2) was placed in a beaker, 500 mL of nitric acid was added, and stirring was continued at room temperature for 3 h at a speed of 150 rpm; the solid phase was filtered and separated, and the solid phase was repeatedly washed in distilled water until the pH value was 7.0, and the adsorbent was dried in an oven at 80 ° C for 4 h;

[0027] (4) 50 g of the adsorbent described in step (3) was mixed with 200 mL of DMF by ultrasonication, and 25 g of β-cyclodextrin and 1 mL of bifunctional linker HMDI were added after mixing. The mixture was placed in a round-bottom flask, and the mixture was heated in an oil bath at 70°C for 6 h under a nitrogen atmosphere and a rotation speed of 350 rpm, and filtered for separation;

[0028] (5) washing the adsorbent in ethanol and pure water for multiple times, and drying in an oven at 80°C for 4 h;

[0029] (6) The adsorbent prepared in step (5) is used to remove trace iodine from the raw material brine of ion-exchange membrane caustic soda.

[0030] Preferably, the specific steps of using the adsorbent in step (6) to remove trace iodine in the raw material brine of ion-exchange membrane caustic soda are:

[0031] (1) The raw material brine of ion membrane caustic soda is introduced into the reaction tower, and hydrochloric acid is added to adjust the pH of the brine to 2, and the brine is stirred for 30 minutes using a stirring paddle, and hydrogen peroxide is added and stirred for 30 minutes for standby use;

[0032] (2) The adsorbent is placed in an adsorption tower, and the upper end of the adsorption tower is connected to a pressure pump. While the system remains sealed, the adsorption tower is pumped at a pressure of 0.5 m 3 The treated brine is added into the adsorption tower at a flow rate of / h.

[0033] (3) Collect 50 mL of brine flowing out of the adsorption column and test the iodine content in the resulting brine using the bromine water method.

[0034] The invention discloses a preparation method of an activated carbon modified adsorbent and its application in removing iodine from ion membrane caustic soda raw material brine, comprising the following steps:

[0035] (1) Place 100g of activated carbon in a beaker and add 500mL of deionized water; add 40mL of glacial acetic acid while stirring at room temperature, and continue stirring for 30min at a speed of 350rpm; weigh the required mass of modifier, the mass ratio of nitrogen content of the modifier to activated carbon is 2%-6%, and 40mL of 30% hydrogen peroxide, add them to the above beaker in sequence, continue stirring for 24h at room temperature and in the dark, filter, and dry in a 90℃ oven for 12-24h;

[0036] The modifier described in step (1) is any one of pyridine, pyrrole, vitamin B1, EDTA, imidazole, quinoline, and trichloroisocyanuric acid;

[0037] (2) placing the dried sample in a tube furnace, maintaining a nitrogen flow rate of 50 mL / min, heating the sample to 400-900°C at a heating rate of 5°C / min and calcining the sample for 2 h to obtain a modified adsorbent;

[0038] (3) Place 100g of activated carbon in a beaker, add 500mL of nitric acid, and stir continuously at room temperature for 3h at a speed of 150rpm. Filter and separate, wash the solid phase repeatedly in distilled water until the pH is close to 7.0, and then dry the activated carbon in an oven at 80℃ for 4h;

[0039] (4) Take 50 g of activated carbon and 200 mL of DMF, mix them evenly by ultrasonication, add a certain amount of cyclodextrin (the amount of cyclodextrin is 5 g, 10 g, 15 g, 20 g, 25 g, and 30 g, respectively) and 1 mL of bifunctional linker HMDI, put them into a round-bottom flask, heat the mixture in a 70 °C oil bath under a nitrogen atmosphere and a rotation speed of 350 rpm for 6 h, and filter and separate;

[0040] (5) The adsorbent was washed several times with ethanol and pure water and then dried in an oven at 80 °C for 4 h.

[0041] (6) The adsorbent prepared in step (5) is used to remove trace iodine from the raw material brine of ion-exchange membrane caustic soda.

[0042] The mass ratio of the nitrogen content of the modifier to the activated carbon is 4%; the mass ratio of cyclodextrin to the activated carbon is 50%.

[0043] The beneficial effects of the present invention are as follows:

[0044] The present invention provides a method for preparing an activated carbon modified adsorbent. Compared with other methods, the method greatly reduces the preparation cost, is simpler to operate and can be expanded. The technical scheme adopted by the present invention is: by using one of pyridine, pyrrole, vitamin B1, EDTA, imidazole, quinoline, and trichloroisocyanuric acid as an activated carbon surface modifier to modify the activated carbon, and grafting one of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin to the surface of the activated carbon, an activated carbon adsorbent modified with heteroatom nitrogen and grafted with cyclodextrin is prepared, which has excellent adsorption performance for iodine in brine. At the same time, compared with the prior art: the modifier selected in the present invention is non-toxic and harmless, and the price is low; secondly, the amount of the modifier used in the present invention is small, and the utilization rate is high, so the modification cost is lower than other technologies. The present invention will provide an important theoretical basis and practical basis for solving the problem of trace iodine removal that is common in the ion membrane caustic soda industry, and provide a strong technical guarantee for the healthy and sustainable development of the ion membrane caustic soda industry.

[0045] Based on the selective adsorption capacity of heteroatoms and cyclodextrin for elemental iodine, the activated carbon adsorbent was modified with heteroatoms and grafted with cyclodextrin to improve the removal capacity of activated carbon for trace iodine in the raw brine of ion-exchange membrane caustic soda. The activated carbon was modified with different nitrogen sources. In the raw brine of ion-exchange membrane caustic soda with an initial iodine concentration of 2.5 mg / L, the iodine removal rate of the activated carbon modified with pyridine was 43.6%, which was 11.2% higher than that of the unmodified activated carbon. β-cyclodextrin was grafted onto the surface of activated carbon. In the raw brine of ion-exchange membrane caustic soda with an initial iodine concentration of 2.5 mg / L, the iodine removal rate of the β-cyclodextrin grafted activated carbon was 47.7%, which was 15.3% higher than that of the unmodified activated carbon. When β-cyclodextrin is grafted onto the surface of pyridine-modified activated carbon, the removal rate of iodine by the adsorbent is 73.2%. Compared with the unmodified activated carbon, the removal rate of iodine is increased by 41.2%, and the adsorption performance is greatly improved. The present invention provides a unique and effective method for removing trace iodine in industrial ion-exchange membrane caustic soda raw material brine, which has good economic benefits and operability.

[0046] As shown in Table 1, activated carbon has better removal performance for iodine in saturated salt water than other adsorbents, with a removal rate of 42.4%. The adsorbent is preferably activated carbon.

[0047] As shown in Table 2, the adsorbent (N1AC) modified with N1=pyridine in Example 1 has a better removal effect on iodine in brine than other modifiers, with a removal rate of 43.6%. Compared with the unmodified activated carbon adsorbent, the iodine removal rate is increased by 11.2%.

[0048] It can be seen from Table 3 that when the nitrogen doping amount is 4%, the iodine removal performance of the adsorbent is the best, and the removal rate reaches 43.6%. The nitrogen doping amount is preferably 4%.

[0049] It can be seen from Table 4 that when the calcination temperature is 600°C, the iodine removal performance of the adsorbent is the best, and the removal rate reaches 55.6%. The calcination temperature is preferably 600°C.

[0050] As shown in Table 5, the adsorption effect of N1AC grafted β-cyclodextrin adsorbent (N1AC-2) in Example 2 is better than that of other cyclodextrin adsorbents (N1AC-1 and N1AC-3), and the iodine removal rate reaches 73.2%. The iodine removal rate of N1AC is 41.4%, and the iodine removal rate of activated carbon grafted with cyclodextrin only (AC-2) is 47.7%.

[0051] It can be seen from Table 6 that when the amount of cyclodextrin is 25 g, the iodine removal performance of the adsorbent is the best, and the removal rate reaches 73.2%. The optimal amount of cyclodextrin is 25 g. DETAILED DESCRIPTION

[0052] Example 1 Adsorbent Preparation

[0053] Take 100g of untreated 4-6 mesh with a specific surface area of ​​1200m 2 / g activated carbon was placed in a beaker, and 500mL of deionized water was added; 40mL of glacial acetic acid was added while stirring at room temperature, and stirring was continued for 30min (speed was 350rpm); 22.6g of pyridine and 40mL of hydrogen peroxide (mass concentration 30%) were weighed, and added to the above beaker in turn, and stirred for 24h at room temperature and in the dark, filtered, and dried in a 90℃ oven for 12-24h. The dried sample was placed in a tubular furnace, the nitrogen flow rate was maintained at 50mL / min, and the temperature was raised to 600℃ at a heating rate of 5℃ / min and calcined for 2h to obtain the modified adsorbent N1AC.

[0054] Place the modified adsorbent in a beaker, add 500 mL of nitric acid, and stir continuously at room temperature for 3 hours at a speed of 150 rpm. Filter and separate, wash the solid phase repeatedly in distilled water until the pH is close to 7.0, and then dry the adsorbent in an oven at 80°C for 4 hours. Take 50 g of the above adsorbent and 200 mL of DMF in a round-bottom flask, mix them evenly by ultrasound, add 25 g of α-cyclodextrin and 1 mL of bifunctional linker HMDI after mixing, heat the mixture in a 70°C oil bath at a speed of 350 rpm under a nitrogen atmosphere for 6 hours, and filter and separate. Wash the above adsorbent several times in ethanol and pure water, and dry it in an oven at 80°C for 4 hours. Obtain N1AC-1.

[0055] The iodine adsorption experiment of the modified adsorbent N1AC-1 includes the following steps:

[0056] (1) Take 500 mL of ion-exchange membrane caustic soda raw material brine with an iodine concentration of 2.5 mg / L (the main components are 300 g / L sodium chloride, 2-3 g / L sodium chlorate and trace amounts of other impurity ions), add hydrochloric acid to adjust the pH of the brine to 2, stir with a magnetic stirrer for 30 min, add 0.05 mL of hydrogen peroxide (mass concentration 30%) and stir for 30 min, and set aside.

[0057] (2) Take 70g of adsorbent and place it in an adsorption column with a diameter of 3cm. Fix the adsorption column. Connect the upper end of the adsorption column to a flow pump. While keeping the system airtight, pump the adsorbent at a rate of 0.5m 3 500 mL of the treated brine was added into the adsorption column at a flow rate of / h.

[0058] (3) Collect 50 mL of brine flowing out of the adsorption column and test the iodine content in the resulting brine using the bromine water method.

[0059] Example 2 Adsorbent Preparation

[0060] Take 100g of untreated 4-6 mesh with a specific surface area of ​​1200m 2 / g activated carbon was placed in a beaker, and 500mL of deionized water was added; 40mL of glacial acetic acid was added while stirring at room temperature, and stirring was continued for 30min (speed was 350rpm); 22.6g of pyridine and 40mL of hydrogen peroxide (mass concentration 30%) were weighed, and added to the above beaker in turn, and stirred for 24h at room temperature and in the dark, filtered, and dried in a 90℃ oven for 12-24h. The dried sample was placed in a tubular furnace, the nitrogen flow rate was maintained at 50mL / min, and the temperature was raised to 600℃ at a heating rate of 5℃ / min and calcined for 2h to obtain the modified adsorbent N1AC.

[0061] Place the modified adsorbent in a beaker, add 500 mL of nitric acid, and stir continuously at room temperature for 3 hours at a speed of 150 rpm. Filter and separate, wash the solid phase repeatedly in distilled water until the pH is close to 7.0, and then dry the adsorbent in an oven at 80°C for 4 hours. Take 50 g of the above adsorbent and 200 mL of DMF in a round-bottom flask, mix them evenly by ultrasound, add 25 g of β-cyclodextrin and 1 mL of bifunctional linker HMDI after mixing, heat the mixture in a 70°C oil bath at a speed of 350 rpm under a nitrogen atmosphere for 6 hours, and filter and separate. Wash the above adsorbent several times in ethanol and pure water, and dry it in an oven at 80°C for 4 hours. Obtain N1AC-2.

[0062] The experimental steps for adsorbing iodine by the adsorbent are the same as those in Example 1.

[0063] In this embodiment, the modified adsorbent grafted with β-cyclodextrin has a better adsorption effect than the adsorbent grafted with other cyclodextrins, and the adsorption rate reaches 73.2%.

[0064] Example 3 Adsorbent Preparation

[0065] Take 100g of untreated 4-6 mesh with a specific surface area of ​​1200m 2 / g activated carbon was placed in a beaker, and 500mL of deionized water was added; 40mL of glacial acetic acid was added while stirring at room temperature, and stirring was continued for 30min (speed was 350rpm); 22.6g of pyridine and 40mL of hydrogen peroxide (mass concentration 30%) were weighed, and added to the above beaker in turn, and stirred for 24h at room temperature and in the dark, filtered, and dried in a 90℃ oven for 12-24h. The dried sample was placed in a tubular furnace, the nitrogen flow rate was maintained at 50mL / min, and the temperature was raised to 600℃ at a heating rate of 5℃ / min and calcined for 2h to obtain the modified adsorbent N1AC.

[0066] Place the modified adsorbent in a beaker, add 500mL nitric acid, and stir continuously at room temperature for 3h at a speed of 150rpm. Filter and separate, wash the solid phase repeatedly in distilled water until the pH is close to 7.0, and then dry the adsorbent in an oven at 80℃ for 4h. Take 50g of the above adsorbent and 200mL DMF in a round-bottom flask, mix them evenly by ultrasound, add 25g γ-cyclodextrin and 1mL bifunctional linker HMDI after mixing, heat the mixture in a 70℃ oil bath at 350rpm under nitrogen atmosphere for 6h, and filter and separate. Wash the above adsorbent several times in ethanol and pure water, and dry it in an oven at 80℃ for 4h. Obtain N1AC-3.

[0067] The experimental steps for adsorbing iodine by the adsorbent are the same as those in Example 1.

[0068] Comparative Example 1

[0069] The adsorbent selection and modification condition screening experiment includes the following steps:

[0070] (1) Take 70g of untreated adsorbent (activated carbon, diatomaceous earth, molecular sieve, kaolin) and place it in an adsorption column with a diameter of 3cm. Fix the adsorption column. Connect the upper end of the adsorption column to a flow pump. While keeping the system closed, pump the adsorption column at a speed of 0.5m 3 500 mL of saturated saline solution containing 2.5 mg / L iodine was added to the adsorption column at a flow rate of / h.

[0071] (2) Collect 50 mL of brine flowing out of the adsorption column and test the iodine content in the brine using the ferric thiocyanate-sodium nitrite catalytic kinetic method.

[0072] The comparison of iodine removal efficiency of various adsorbents in saturated salt water is shown in Table 1.

[0073] Table 1 Effect of different adsorbents on iodine removal rate

[0074] Adsorbent Concentration after removal (mg / L) Removal rate (%) Activated carbon 1.70 32.0 diatomite 1.82 27.2 Molecular sieve 1.74 30.3 Kaolin 1.83 26.7

[0075] As shown in Table 1, activated carbon has better removal performance for trace iodine in brine than other adsorbents, with a removal rate of 32.0%. The adsorbent is preferably activated carbon.

[0076] Comparative Example 2

[0077] The adsorbent selection and modification condition screening experiment includes the following steps:

[0078] (1) Place 100g of activated carbon in a beaker and add 500mL of deionized water; add 40mL of glacial acetic acid while stirring at room temperature, continue stirring for 30min, and then rotate at 350rpm; weigh the required mass of modifier, the mass ratio of nitrogen content of the modifier to activated carbon is 4%, and 40mL of 30% hydrogen peroxide, add them to the above beaker in turn, continue stirring for 24h at room temperature and in the dark, filter, and dry in a 90℃ oven for 12-24h.

[0079] The modifier described in step (1) is any one of pyridine, pyrrole, vitamin B1, EDTA, imidazole, quinoline, and trichloroisocyanuric acid;

[0080] (2) placing the dried sample in a tube furnace, maintaining a nitrogen flow rate of 50 mL / min, heating the sample to 500-900°C at a heating rate of 5°C / min and calcining the sample for 2 h to obtain a modified adsorbent;

[0081] (3) Take 500 mL of ion-exchange membrane caustic soda raw material brine with an iodine concentration of 2.5 mg / L, add hydrochloric acid to adjust the pH to 2, stir with a magnetic stirrer for 30 min, add 0.05 mL of hydrogen peroxide (30%), stir for 30 min, and set aside.

[0082] (4) Take 70g of the above modified adsorbents (activated carbon, N1AC, N2AC, N3AC, N4AC, N5AC, N6AC, N7AC) and place them in an adsorption column with a diameter of 3cm. Fix the adsorption column. Connect the upper end of the adsorption column to a flow pump and pump the adsorption column at a speed of 0.5m / s while keeping the system airtight. 3 The above-mentioned ion membrane caustic soda raw material brine is added into the adsorption column at a flow rate of / h.

[0083] (5) Collect 50 mL of brine flowing out of the adsorption column and test the iodine content in the brine using the bromine water method.

[0084] Table 2 Effect of different modifiers on iodine removal rate

[0085] The effects of different modifiers on the iodine removal performance of the adsorbent were investigated. As shown in Table 2 above, the adsorbent (N1AC) modified with N1=pyridine in Example 1 has a better removal effect on iodine in brine than other modifiers, with a removal rate of 43.6%. Compared with the unmodified activated carbon adsorbent, the iodine removal rate is increased by 11.2%.

[0086] Comparative Example 3

[0087] Take 100g of untreated 4-6 mesh with a specific surface area of ​​1200m 2 / g activated carbon is placed in a beaker, and 500mL of deionized water is added; 40mL of glacial acetic acid is added while stirring at room temperature, and stirring is continued for 30min (speed is 350rpm); 11.3g, 22.6g and 34g of pyridine and 40mL of hydrogen peroxide (mass concentration 30%) are weighed respectively, and added to the above beaker in turn, and stirred for 24h at room temperature and light-proof conditions, filtered, and dried in a 90℃ oven for 12-24h. The dried sample is placed in a tubular furnace, the nitrogen flow rate is maintained at 50mL / min, and the temperature is increased to 600℃ at a heating rate of 5℃ / min and calcined for 2h to obtain the modified adjuvant.

[0088] The effect of nitrogen doping on iodine removal efficiency of ion-exchange membrane caustic soda raw brine containing 2.5 mg / L iodine was investigated.

[0089] Table 3 Effect of different nitrogen doping amounts on iodine removal rate

[0090] Nitrogen doping amount Concentration after removal (mg / L) Removal rate (%) 2% 1.56 37.6 4% 1.41 43.6 6% 1.49 40.4

[0091] The effect of different nitrogen doping amounts on the iodine removal performance of the adsorbent was investigated. As shown in Table 3 above, the effect of different nitrogen doping amounts (nitrogen element to activated carbon mass ratio of 2%, 4%, 6%) on the removal of trace iodine from brine by the adsorbent was compared. When the nitrogen doping amount was 4%, the iodine removal performance of the adsorbent was the best, and the removal rate reached 43.6%. The nitrogen doping amount is preferably 4%.

[0092] Comparative Example 4

[0093] Take 100g of untreated 4-6 mesh with a specific surface area of ​​1200m 2 / g of activated carbon was placed in a beaker, and 500mL of deionized water was added; 40mL of glacial acetic acid was added while stirring at room temperature, and stirring was continued for 30min (speed was 350rpm); 22.6g of pyridine and 40mL of hydrogen peroxide (mass concentration 30%) were weighed, and added to the above beaker in turn, and stirring was continued for 24h at room temperature and light-proof conditions, filtered, and dried in a 90℃ oven for 12-24h. The dried sample was placed in a tubular furnace, the nitrogen flow rate was maintained at 50mL / min, and the temperature was increased to 400℃, 500℃, 600℃, 700℃, 800℃ and 900℃ at a heating rate of 5℃ / min, and calcined for 2h to obtain the modified adsorbent.

[0094] Table 4 Effect of different calcination temperatures on iodine removal rate

[0095] Calcination temperature (℃) Concentration after removal (mg / L) Removal rate (%) 400 1.52 39.2 500 1.47 41.2 600 1.41 43.6 700 1.55 38.0 800 1.61 35.6 900 1.56 37.6

[0096] The effect of different calcination temperatures on the iodine removal performance of the adsorbent was investigated. As shown in Table 4 above, the effect of different calcination temperatures (400°C, 500°C, 600°C, 700°C, 800°C, 900°C) on the removal of trace iodine from the raw brine of ion-exchange membrane caustic soda by the adsorbent was compared. When the calcination temperature was 600°C, the iodine removal performance of the adsorbent was the best, and the removal rate reached 43.6%. The calcination temperature is preferably 600°C.

[0097] Comparative Example 5

[0098] The iodine adsorption experiment of the modified adsorbent includes the following steps:

[0099] (1) Take 500 mL of ion-exchange membrane caustic soda raw material brine with an iodine concentration of 2.5 mg / L, add hydrochloric acid to adjust the pH to 2, stir with a magnetic stirrer for 30 min, add 0.05 mL of hydrogen peroxide (30%), stir for 30 min, and set aside.

[0100] (2) Take 70g of adsorbent (activated carbon, N1AC, AC-2, N1AC-1, N1AC-2, N1AC-3) and place it in an adsorption column with a diameter of 3cm. Fix the adsorption column. Connect the upper end of the adsorption column to a flow pump. While keeping the system closed, pump the adsorption column at a speed of 0.5m 3 500 mL of the treated industrial brine was added to the adsorption column at a flow rate of / h. The activated carbon was untreated 4-6 mesh with a specific surface area of ​​1200 m 2 / g of activated carbon, AC-2 is activated carbon directly grafted with β-cyclodextrin.

[0101] (3) 50 mL of brine was collected from the adsorption column and the iodine content in the brine was tested by the bromine water method. The results are shown in Table 5.

[0102] Table 5 Effect of different adsorbents on iodine removal rate

[0103] Adsorbent Iodine concentration after removal (mg / L) Removal rate (%) Activated carbon 1.70 32.0% N1AC 1.47 41.2% AC-2 1.31 47.6% N1AC-1 1.10 56.0% N1AC-2 0.67 73.2% N1AC-3 0.86 65.6%

[0104] The iodine removal performance of different adsorbents was investigated. It can be seen from Table 5 that the N1AC grafted β-cyclodextrin adsorbent (N1AC-2) in Example 2 has a better adsorption effect than other grafted cyclodextrin adsorbents (N1AC-1 and N1AC-3), with an iodine removal rate of 73.2%. The iodine removal rate of N1AC is 41.2%, and the iodine removal rate of activated carbon grafted with cyclodextrin only (AC-2) is 47.6%.

[0105] Comparative Example 6

[0106] Take 100g N1AC and place it in a beaker, add 500mL nitric acid, and stir continuously at room temperature for 3h at a speed of 150rpm. Filter and separate, wash the solid phase repeatedly in distilled water until the pH is close to 7.0, and then dry it in an oven at 80℃ for 4h. Take 50g of the above adsorbent and 200mL DMF, mix them evenly by ultrasonic, add 5g, 10g, 15g, 20g, 25g, 30g β-cyclodextrin and 1mL bifunctional linker HMDI respectively after mixing, put them into a round-bottom flask, heat the mixture in a 70℃ oil bath under a nitrogen atmosphere and a speed of 350rpm for 6h, and filter and separate. Wash the above adsorbent several times in ethanol and pure water, and then dry it in an oven at 80℃ for 4h.

[0107] Table 6 Effect of different β-cyclodextrin amounts on iodine removal rate

[0108] β-cyclodextrin amount Concentration after removal (mg / L) Removal rate (%) 0g 1.47 41.2 5g 1.19 52.4 10g 1.05 58.0 15g 0.93 62.8 20g 0.77 69.2 25g 0.67 73.2 30g 0.69 72.4

[0109] The effect of different amounts of cyclodextrin grafted to the modified adsorbent on the iodine removal performance was investigated. As shown in Table 6 above, the effect of different amounts of cyclodextrin (0g, 5g, 10g, 15g, 20g, 25g, 30g) on ​​the adsorbent removing trace iodine from the caustic soda raw material brine was compared. When the amount of cyclodextrin was 25g, the adsorbent had the best iodine removal performance, with a removal rate of 73.2%. The optimal amount of cyclodextrin was 25g.

Claims

1. An application of an activated carbon modified adsorbent in removing iodine from ion membrane caustic soda raw material brine, characterized in that: The following steps are involved: (1) Place 100g of activated carbon in a beaker and add 500mL of deionized water; add 40mL of glacial acetic acid while stirring at room temperature, and continue stirring for 30min at a speed of 350rpm; weigh the required mass of modifier and 40mL of 30% hydrogen peroxide, the mass ratio of nitrogen content of the modifier to activated carbon is 2%-6%, add the modifier and hydrogen peroxide to the above beaker in turn, continue stirring for 24h at room temperature and in the dark, filter, and dry in a 90℃ oven for 12-24h; The modifier described in step (1) is any one of pyridine, pyrrole, vitamin B1, EDTA, imidazole, quinoline, and trichloroisocyanuric acid; (2) placing the dried sample in a tube furnace, maintaining a nitrogen flow rate of 50 mL / min, heating the sample to 400-900°C at a heating rate of 5°C / min and calcining the sample for 2 h to obtain a modified adsorbent; (3) 100 g of the adsorbent in step (2) was placed in a beaker, 500 mL of nitric acid was added, and stirring was continued at room temperature for 3 h at a speed of 150 rpm; the solid phase was filtered and separated, and the solid phase was repeatedly washed in distilled water until the pH value was 7.0, and the adsorbent was dried in an oven at 80 ° C for 4 h; (4) 50 g of the adsorbent described in step (3) was mixed with 200 mL of DMF by ultrasonication, and a certain amount of cyclodextrin and 1 mL of bifunctional linker HMDI were added after mixing. The mixture was placed in a round-bottom flask, and the mixture was heated in an oil bath at 70°C for 6 h under a nitrogen atmosphere and a rotation speed of 350 rpm, and filtered for separation; (5) washing the adsorbent in ethanol and pure water for multiple times, and drying in an oven at 80°C for 4 h; (6) The adsorbent prepared in step (5) is used to remove trace iodine from the raw material brine of ion-exchange membrane caustic soda.

2. The use of the activated carbon modified adsorbent in deiodination of ion membrane caustic soda raw material brine according to claim 1, characterized in that: The modifier in step (1) is pyridine.

3. The use of the activated carbon modified adsorbent in deiodination of ion membrane caustic soda raw material brine according to claim 1, characterized in that: The calcination temperature in step (2) is 600°C.

4. The use of the activated carbon modified adsorbent in deiodination of ion membrane caustic soda raw material brine according to claim 1, characterized in that: The mass ratio of nitrogen content of the modifier to activated carbon is 4%.

5. The use of the activated carbon modified adsorbent according to claim 1 for removing iodine in ion membrane caustic soda raw material brine, characterized in that; The grafted cyclodextrin in step (4) is β-cyclodextrin.

6. The use of the activated carbon modified adsorbent according to claim 1 in removing iodine from ion membrane caustic soda raw material brine, characterized in that: The activated carbon in step (1) is in the shape of a column or a flake, with a particle size of 4-6 mesh and a specific surface area of ​​1000-1200m 2 / g.

7. The use of the activated carbon modified adsorbent according to claim 1 in removing iodine from ion membrane caustic soda raw material brine, characterized in that: The following steps are involved: (1) Place 100g of activated carbon in a beaker and add 500mL of deionized water; add 40mL of glacial acetic acid while stirring at room temperature, and continue stirring for 30min at a speed of 350rpm; weigh the required mass of modifier, the mass ratio of nitrogen content of the modifier to activated carbon is 4%, and 40mL of 30% hydrogen peroxide, add them to the above beaker in sequence, continue stirring for 24h at room temperature and in the dark, filter, and dry in a 90℃ oven for 12-24h; The modifier described in step (1) is pyridine; (2) placing the dried sample in a tube furnace, maintaining a nitrogen flow rate of 50 mL / min, heating to 600 °C at a heating rate of 5 °C / min and calcining for 2 h to obtain a modified adsorbent; (3) 100 g of the adsorbent in step (2) was placed in a beaker, 500 mL of nitric acid was added, and stirring was continued at room temperature for 3 h at a speed of 150 rpm; the solid phase was filtered and separated, and the solid phase was repeatedly washed in distilled water until the pH value was 7.0, and the adsorbent was dried in an oven at 80 ° C for 4 h; (4) 50 g of the adsorbent described in step (3) was mixed with 200 mL of DMF by ultrasonication, and 25 g of β-cyclodextrin and 1 mL of bifunctional linker HMDI were added after mixing. The mixture was placed in a round-bottom flask, and the mixture was heated in an oil bath at 70 °C for 6 h under a nitrogen atmosphere and a rotation speed of 350 rpm, and filtered for separation; (5) washing the adsorbent in step (4) with ethanol and pure water for multiple times, and drying in an oven at 80° C. for 4 h; (6) The adsorbent prepared in step (5) is used to remove trace iodine from the raw material brine of ion-exchange membrane caustic soda.

8. The use of the activated carbon modified adsorbent according to claim 1 in removing iodine from ion membrane caustic soda raw material brine, characterized in that: The specific steps of using the adsorbent in step (6) to remove trace iodine in the raw material brine of ion-exchange membrane caustic soda are: (1) Pass industrial brine into the reaction tower, add hydrochloric acid to adjust the pH of the industrial brine to 2, stir with a stirring paddle for 30 minutes, add hydrogen peroxide and stir for 30 minutes, and set aside; (2) The adsorbent is placed in an adsorption tower, and the upper end of the adsorption tower is connected to a pressure pump. While the system is kept airtight, the adsorbent is pumped at a pressure of 0.5 m 3 The treated industrial brine is added into the adsorption tower at a flow rate of / h; (3) Collect 50 mL of brine flowing out of the adsorption column and test the iodine content in the brine using the bromine water method.

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