Iodine removal process of carnallite

Abstract

The embodiment of the invention discloses an iodine removal process for carnallite. The process comprises the following steps: dissolving sodium chloride carnallite in water, and filtering to remove insoluble substances to obtain filtrate; adding sodium hydroxide into the filtrate, adjusting the pH value to be alkaline, and removing heavy metals, calcium and magnesium through adsorption to obtain an adsorbed feed liquid; adding hydrochloric acid into the adsorbed feed liquid, and adjusting the pH to be acidic to obtain an acidic solution; carrying out oxidation treatment on the acid solution by adopting an advanced oxidation technology to obtain an oxidized solution; and adding modified activated carbon into the oxidized solution, stirring, carrying out solid-liquid separation, and collecting a liquid phase. The method provided by the invention can effectively remove iodine in sodium chloride carnallite, does not introduce new impurities, prolongs the service life of the ionic membrane, and has good application value.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of iodine removal process, in particular to an iodine removal process of miscellaneous salt. BACKGROUND

[0002] Since the existence of iodine in brine will have a serious impact on the service life of ion-exchange membrane, the iodine removal process of salt plays an important role in the process of ion-exchange membrane caustic soda production. The iodine in the brine exists in the form of I - in the refined brine to be electrolyzed, and after entering the electrolytic cell, I - is oxidized to IO3 - in the anode chamber. Once IO3 - enters the alkaline environment, it will be oxidized to IO6 5- , which will affect the cell voltage of the electrolytic cell as the electrolysis time goes on. In addition, when the mass fraction of IO3 - in the electrolytic cell is higher than 1*10 -6 , IO3 - will combine with Na + to form a precipitate attached to the ion-exchange membrane. When the mass fraction of IO3 - is less than 1*10 -6 , the perrhenate (IO6 5- ) can combine with barium ions, magnesium ions, calcium ions and strontium ions in the electrolyte to form Ba5(IO6)2, Mg5(IO6)2, Ca5(IO6)2, Sr5(IO6)2 precipitates, which will have different degrees of impact on the current efficiency and increase the energy consumption. At the same time, the accumulation of these precipitates in the ion-exchange membrane will destroy the carboxylic acid layer structure of the ion-exchange membrane and shorten the service life of the membrane.

[0003] There are many methods for removing iodine in ion-exchange membrane caustic soda process brine, including oxidation method, ion exchange method, air blowing method, electrolysis method, solvent flotation method and precipitation method, etc.

[0004] (1) For the oxidation of iodine ions in brine, the commonly used oxidants are chlorine, sodium hypochlorite, hydrogen peroxide, sodium nitrite, etc. Chlorine is cheap and easy to prepare, and is often used as an oxidant in industry, but chlorine has strong oxidizing properties and is easy to cause over-oxidation in the oxidation process of iodine ions, oxidizing iodine ions to iodate ions, and its addition amount is difficult to control in practical application. Under acidic conditions, sodium hypochlorite and hydrogen peroxide can exhibit good oxidizing properties and have been applied in industry. Sodium nitrite is relatively expensive, and the use of sodium nitrite will introduce impurities. (2) Ion exchange resin is easily affected by other ions in the raw material, has poor anti-interference ability, has complex desorption operation, high cost, and will also generate a large amount of waste during use, so it is not recommended for large-scale application in industrial production. (3) The air blowing method has relatively wide application in iodine recovery, has relatively high recovery rate, and is suitable for the enrichment of iodine in high-iodine-content liquid to be treated, but this method requires large-scale equipment such as large air blowers, which has high equipment cost and high power consumption, and has relatively limited application in the removal of trace iodine in ion membrane caustic soda dilute brine in industry. (4) The electrolysis method has high operation cost and high energy consumption, and is not suitable for industrial production of ion membrane caustic soda raw water deiodination. (5) The solvent flotation method shows good effect on iodine recovery, but the recovered solution still contains a high concentration of iodine, which does not meet the requirement that the iodine content in the brine for ion membrane production process should be less than 0.4 mg / L. (6) The precipitation method has simple operation and low cost, but it will introduce other impurities in the application process and generate a large amount of waste liquid, and there are still many problems to be discussed in the application of this method in industry.

[0005] In the actual deiodination process, because the brine contains a high concentration of chloride ions, and the iodine ions and chloride ions are in the same main group and have similar properties, it is difficult to separate and remove trace iodine from the brine containing high-concentration chloride ions. The difficulty in actual treatment is to remove trace iodine from the brine containing high-concentration chloride ions under the premise of not introducing other impurities by optimizing the experimental conditions, so as to be applied to industrial application. Since the brine in the production process is recycled, the deiodination treatment of the process brine of any production process can achieve the purpose of protecting the ion membrane. Huang Lina mentioned in the paper "Removal Technology of Trace Iodine in Salt (Brine) Water" that in the process of ion membrane caustic soda production, the iodine content in the electrolysis brine is greater than 0.4 mg / L, which will seriously affect the service life of the ion membrane, thereby increasing the cost of alkali production, and therefore the iodine content in the brine needs to be reduced to below 0.4 mg / L before the refined brine is put into the electrolysis tank. SUMMARY

[0006] Therefore, the embodiments of the present application provide a deiodination process for miscellaneous salt.

[0007] To achieve the above object, the embodiment of the present application provides the following technical scheme:

[0008] A process for removing iodine from a mixed salt, the process comprising the following steps:

[0009] (1) dissolving sodium chloride mixed salt in water, removing insoluble substances by filtration to obtain a filtrate;

[0010] (2) adding sodium hydroxide to the filtrate to adjust the pH to be alkaline, removing heavy metals and calcium and magnesium by adsorption to obtain an adsorbed solution;

[0011] (3) adding hydrochloric acid to the adsorbed solution to adjust the pH to be acidic to obtain an acidic solution;

[0012] (4) oxidizing the acidic solution by using a high-level oxidation technology to obtain an oxidized solution;

[0013] (5) adding modified activated carbon to the oxidized solution, stirring, solid-liquid separation, and collecting the liquid phase.

[0014] Further, in step (1), the mass ratio of the sodium chloride mixed salt to water is 0.15-0.2:1;

[0015] The temperature for dissolving is 15-35℃.

[0016] Further, in step (2), the pH is 9-10;

[0017] The adsorption uses an adsorption column with chelating resin as filler, and the chelating resin includes D401, D402, PM401, and D851.

[0018] Further, in step (3), the concentration of the hydrochloric acid is 30%-37%, and the pH is 2-4.

[0019] Further, in step (4), the high-level oxidation technology includes one or a combination of several of the following: reagent oxidation, ozone oxidation, and ozone catalytic oxidation.

[0020] Further, the reagent or ozone is slowly added to the acidic solution, the reagent is NaClO or H2O2, the molar ratio of the reagent or ozone to I - in the acidic solution is 1:1.95-2.05, the stirring is performed at 10-35℃ for 1-2h, and the oxidation-reduction potential of the oxidation system is controlled to be 520mV-550mV.

[0021] Further, in step (5), the addition amount of the modified activated carbon is 1g / L-5g / L;

[0022] The stirring condition is 10-35℃ for 1-2h.

[0023] Further, the preparation method of the modified activated carbon is as follows:

[0024] (1) The powder activated carbon is decocted in hot water, filtered, and dried to obtain activated carbon;

[0025] (2) The activated carbon is prepared into an activated carbon water suspension, a zirconium salt solution and an acid are synchronously added dropwise, after the dropwise addition is completed, stirring is performed, water washing is performed until neutral, and activated carbon loaded with zirconium is obtained;

[0026] (3) The activated carbon loaded with zirconium is dispersed in water, polyethyleneimine is added and ultrasonically dispersed, air is exposed, heating is performed at the same time, and then lye is added dropwise to perform alkalization;

[0027] (4) After the dropwise addition is completed, air exposure is continuously performed, stirring is performed, solid-liquid separation, water washing, and drying to constant weight are performed, and the modified activated carbon is obtained.

[0028] Further, in step (1), the powder activated carbon is selected from one or more of coconut shell activated carbon, wooden activated carbon, and coal activated carbon, and the particle size is 150-500 mesh; the decoction conditions are 90-100 DEG C for 2-4 h; and the drying conditions are 100-110 DEG C for 2-3 h;

[0029] In step (2), the concentration of the activated carbon water suspension is 10-40 g / L; the zirconium salt solution is an aqueous solution of zirconium salt, the concentration is 0.1-1 mol / L, the zirconium salt is selected from one or more of zirconium sulfate, zirconium nitrate, zirconium chloride, and zirconium acetate; the acid is selected from one or more of sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid; the mass ratio of the activated carbon to the zirconium salt is 100:0.05-3, the amount-of-substance ratio of the acid to the zirconium salt is 1-5:5-1, and the dropwise addition temperature is 50-70 DEG C; and the stirring conditions are 60-90 DEG C for 3-6 h.

[0030] Further, in step (3), the air exposure amount is 20-30 L / min; the heating condition is that the temperature is increased from room temperature at an increase rate of not more than 1 DEG C / min to 50-70 DEG C; the lye is an aqueous solution of alkali, the concentration is 0.05-3 mol / L, and the alkali is selected from one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide; and the alkalization condition is 30-60 DEG C, pH=10-12, and the mass ratio of the activated carbon to polyethyleneimine is 100:0.01-1.

[0031] In step (4), the air exposure amount is 5-15 L / min, and the stirring condition is 70-95 DEG C for 5-10 min.

[0032] The embodiment of the application has the following advantages:

[0033] (1) The present application removes most of the calcium, magnesium and heavy metals in the salt through chelating resin, avoids excessive calcium, magnesium and heavy metals reacting with oxidized iodine in the brine to form insoluble precipitates attached to the surface of the ion exchange membrane, affecting the service life of the ion exchange membrane, on the other hand, the iodine in these insoluble precipitates is difficult to remove by subsequent oxidation and adsorption combination process.

[0034] (2) The process units in the route of the present application, such as resin adsorption, advanced oxidation and adsorption material adsorption, do not introduce new impurities, and the purity of the treated salt can be maintained.

[0035] (3) The modified activated carbon loaded with metal oxides prepared has high dispersity, thereby having good adsorption performance.

[0036] (4) In the implementation process, acid and alkali resistant activated carbon is selected as the carrier, so that the modified activated carbon has good stability in strong acid and alkali conditions, and the skeleton structure of the carrier is not destroyed.

[0037] (5) The activated carbon used in the adsorption unit is modified by zirconium, which strengthens the adsorption selectivity of activated carbon to iodine, and also improves the adsorption capacity of activated carbon. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only exemplary, and for those skilled in the art, other drawings can be obtained from the provided drawings without creative labor.

[0039] Figure 1 The flow chart of the deiodination process of miscellaneous salt provided by the embodiment of the present application. DETAILED DESCRIPTION

[0040] The embodiments of the present application will be described below by specific specific embodiments, and those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in the specification. Obviously, the described embodiments are part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0041] Reference Figure 1 The present application provides a deiodination process for miscellaneous salt, which comprises the following steps.

[0042] (1) Dissolving and filtering: Dissolve sodium chloride mixed salts in water at a mass ratio of 0.15~0.2:1. This water can be tap water, pure water, evaporation condensate, etc. The water temperature is 15~35℃. Sodium chloride mixed salts dissolve in water, filter to remove insoluble matter, and the filtrate is then processed in the next step.

[0043] (2) Removal of heavy metals and calcium and magnesium: The pH of the filtrate from step (1) is controlled at 9-10 using liquid alkali or caustic soda flakes, and heavy metals and calcium and magnesium are adsorbed using resin. In some preferred embodiments, an adsorption column with chelating resin as the packing material is selected. For example, the chelating resin can be D401, D402, PM401, D851, etc. The influent flow rate is controlled at 1-3 BV / h, and the influent can be in a bottom-in, top-out or top-in, bottom-out manner. Resin regeneration: 1) Drain the feed solution in the adsorption column, then backwash with pure water at a flow rate of 3-5 BV / h for 0.5-1h, then drain; 2) Regenerate with 1-3 mol / L hydrochloric acid at a flow rate of 1-3 BV / h at the bottom and a time of 0.5-2h, then soak for 2-3h; 3) Drain, rinse with pure water to remove residual hydrochloric acid at a flow rate of 3-5 BV / h at the bottom and a time of 1-2h; 4) Drain, introduce 1-3 mol / L sodium hydroxide at a flow rate of 1-3 BV / h at the bottom and a time of 0.5-2h, then soak for 2-3h; 5) Drain, rinse with pure water to remove residual alkali at a flow rate of 3-5 BV / h at the bottom and a time of 1-2h; 6) Drain, regeneration complete. Using the above adsorption treatment, the removal rates of heavy metals and calcium and magnesium can both reach over 90%, with heavy metals in the effluent (post-adsorption solution) <1 mg / L and calcium <1 mg / L. 2+ +Mg 2+ <1 mg / L.

[0044] (3) Adjusting pH: Iodine in sodium chloride mixed salt solution is mainly in the form of I. - It exists in the form of I in an acidic environment. - and IO3 - They cannot coexist; iodine in an acidic environment exists as I. - It can restore IO3 - To convert I2, adjust the pH of the post-adsorption solution to 2-4 so that the iodine in the salt solution is converted to I2. - It exists in the form of I2.

[0045] (4) Advanced oxidation: The acidic solution from step (3) is subjected to advanced oxidation to remove I - To convert to I₂, advanced oxidation can employ one or a combination of reagent oxidation, ozone oxidation, and ozone-catalyzed oxidation. Reagent oxidation can use NaClO or H₂O₂ as the oxidant, while ozone catalysts can include granular activated carbon, metal oxides, etc. (Based on 2I₂...) - + ClO - +2H+ = I2 + Cl - + H2O;2I - + H2O2 + 2H + = I2 + 2H2O;2I - + O3 + 2H + = I2 + H2O + O2. The dosage of the agent such as NaClO or H2O2 can control the molar ratio of the dosage of NaClO or H2O2 to the I - in the acidic solution of step (3) to be 1:1.95~2.05, preferably 1:2, and the reaction is carried out at room temperature for 1~2h after the agent is added. If O3 is used to oxidize I - , the molar ratio of the dosage of O3 to the I - in the acidic solution of step (3) is 1:1.95~2.05, preferably 1:2, and the reaction is carried out at room temperature for 1~1.5h after the O3 is introduced. It is particularly emphasized that the dosage of the above agent or the dosage of O3 is theoretically just enough to oxidize I - to I2, but in actual application, when the agent or O3 is added to the solution, other substances in the brine will affect the reaction of the oxidizing agent and the iodine ion at the theoretical molar ratio, so in the reaction process, not only the molar ratio of the oxidizing agent to the iodine ion should be 1:2 as much as possible, but also the change of the ORP (oxidation-reduction potential) of the solution should be concerned throughout the whole process, and the ORP of the system should be controlled to be between 520mV and 550mV at any time, so as to ensure that I - is not oxidized to IO3 - -. - If the oxidizing agent forms peroxide in the oxidation process and makes I - become IO3 - , it will seriously affect the adsorption of iodine by the modified activated carbon in the subsequent process.

[0046] (5) Adsorption of iodine: the effluent of step (4) is adsorbed by one or two stages of adsorption material according to the water quality of the raw water and the effluent requirements, wherein the adsorption material is activated carbon modified by zirconium (the activated carbon can be one or more of wood-based activated carbon, coal-based activated carbon and coconut shell activated carbon), and the dosage of the adsorption material is 1~5g / L, and the stirring is carried out at room temperature (such as 10~35℃) for 1~2h. After adsorption, the effluent is filtered, and the total iodine in the effluent is <0.3mg / L. It is particularly emphasized that the zirconium modified activated carbon has the best adsorption effect on I2, the second best adsorption effect on I - , and the worst adsorption effect on IO3 - , so in step 4, the change of the ORP of the solution should be strictly concerned, and the ORP of the solution should be maintained between 520mV and 550mV at any time, so as to ensure that I - is not oxidized to IO3 -In general, the advanced oxidation unit itself has no ability to remove iodine, and its role is to convert I - into the form of I2, which is the most efficient for modified activated carbon adsorption, so that the subsequent modified activated carbon can play the best effect on the adsorption of iodine elements, and the effluent can meet the requirements of ion exchange membrane.

[0047] I2 first interacts with the inner wall of the modified activated carbon to form I3 - with a negative charge, while zirconium, as a high-valence metal, has a large positive charge and easily adsorbs I3 - The iodine that enters later interacts with iodine molecules themselves and tends to form a dense packed structure of iodine molecules, which can be well fixed in the pore diameter of the activated carbon due to the rich pore diameter of the activated carbon.

[0048] In the following examples and comparative examples, the preparation method of the modified activated carbon used includes the following steps:

[0049] Step one: activated carbon pretreatment

[0050] After 100 g of wood activated carbon is cooked in 95℃ water for 3h, it is filtered and dried in an oven at 100℃ for 3h to obtain activated carbon for standby use.

[0051] Step two: preparation of zirconium-loaded activated carbon

[0052] The activated carbon prepared in step one is prepared into a water suspension with 250 mL of water, and then 15 mL of 0.5 mol / L zirconium chloride aqueous solution and 1 mL of sulfuric acid are added simultaneously at 60℃. After the addition is completed, it is stirred at 80℃ for 4.5h, filtered, and washed with water until neutral to obtain zirconium-loaded activated carbon.

[0053] Step three: the zirconium-loaded activated carbon prepared in step two is dispersed in 200 mL of water, 0.8 g of polyethyleneimine is added and ultrasonically dispersed, and air is introduced at an aeration rate of 25 L / min, while the solution system is heated to 70℃ at a heating rate not exceeding 1℃ / min from room temperature, and then 2 mL of 2 mol / L sodium hydroxide solution is added.

[0054] Step four: after the addition of the solution in step three is completed, it is stirred at an aeration rate of 12 L / min and a temperature of 90℃ for 10 min, separated, washed with water, and dried to constant weight to obtain the zirconium oxide-loaded activated carbon adsorption catalyst material, i.e., the modified activated carbon.

[0055] Example 1

[0056] The composition analysis of the miscellaneous salt of a factory in Shaanxi is as follows:

[0057]

[0058] The iodine removal process of the mixed salt provided in the embodiment comprises the following steps:

[0059] Step 1: The mixed salt is added into water with a water temperature of 20℃ according to the ratio of mixed salt: water = 0.16:1 by mass, and after being fully stirred for 15 min, filtration is performed, and the filtrate is very light yellow and transparent, and the iodine content in the solution is 13.55 mg / L;

[0060] Step 2: Liquid alkali is added into the filtrate of step 1, the pH of the water sample is controlled to be 9.5, and the water flows into the adsorption column filled with chelating resin D401 in a downward-upward mode at a flow rate of 2 BV / h, the heavy metal content in the effluent is less than 1 mg / L, the Ca content in the effluent is 0.198 mg / L, and the Mg content in the effluent is 0.213 mg / L;

[0061] Step 3: Concentrated hydrochloric acid with a concentration of 37% is added into the effluent of step 2, and the pH of the effluent is controlled to be 2.5;

[0062] Step 4: At 25℃, a NaClO solution with a concentration of 12% is added dropwise into the effluent of step 3, and the molar ratio of NaClO:I - =1:2, and after the NaClO solution is added, the solution is stirred for 1 h, during which the oxidation-reduction potential (ORP) of the solution system needs to be focused on, and by controlling the adding speed of the NaClO solution, the ORP of the solution is ensured to be always within the range of 520 mV~550 mV;

[0063] Step 5: Modified activated carbon with a concentration of 2 g / L is added into the effluent of step 4, and the water sample is stirred at 25℃ for 1.5 h, and then filtration is performed, and the iodine content in the filtrate is 0.24 mg / L.

[0064] Example 2

[0065] The composition analysis of the mixed salt of a factory in Ningxia is as follows:

[0066]

[0067] The iodine removal process of the mixed salt provided in the embodiment comprises the following steps:

[0068] Step 1: The mixed salt is added into water with a water temperature of 25℃ according to the ratio of mixed salt: water = 0.2:1 by mass, and after being fully stirred for 20 min, filtration is performed, and the filtrate is light yellow and transparent, and the iodine content in the water is 11.85 mg / L;

[0069] Step 2: Liquid alkali is added into the filtrate of step 1, the pH of the water sample is controlled to be 9, and the water flows into the adsorption column filled with chelating resin D851 in a downward-upward mode at a flow rate of 1.5 BV / h, the heavy metal content in the effluent is less than 1 mg / L, the Ca content in the effluent is 0.163 mg / L, and the Mg content in the effluent is 0.174 mg / L;

[0070] Step 3: Add hydrochloric acid with a concentration of 30% to the effluent of Step 2 to control the pH of the effluent to 2.8;

[0071] Step 4: At 20°C, add H2O2 solution dropwise to the effluent of Step 3 at a molar ratio of H2O2 : I - =1:2, and stir the reaction for 1.5 h after adding H2O2. During this period, pay special attention to the oxidation-reduction potential (ORP) of the solution system. By controlling the addition rate of H2O2, ensure that the ORP of the solution is always between 520 mV and 550 mV.

[0072] Step 5: Add 2.5 g / L of modified activated carbon to the effluent of Step 4, stir for 1.5 h at 30°C, and then filter the water sample. The iodine content in the filtrate is 0.18 mg / L.

[0073] Example 3

[0074] The composition of the miscellaneous salt in a factory in Xinjiang is as follows:

[0075]

[0076] The iodine removal process of the miscellaneous salt provided in this example includes the following steps:

[0077] Step 1: Add miscellaneous salt to water with a temperature of 30°C according to the ratio of miscellaneous salt: water = 0.18:1, stir thoroughly for 15 min, and then filter. The filtrate is colorless and transparent, and the iodine content in the water is 12.19 mg / L.

[0078] Step 2: Add liquid alkali to the filtrate of Step 1 to control the pH of the water sample to 9.8. Flow into the adsorption column filled with chelating resin PM401 at a flow rate of 2.5 BV / h in an up-down manner. The heavy metal content in the effluent is <1 mg / L, the Ca content in the effluent is 0.204 mg / L, and the Mg content in the effluent is 0.237 mg / L.

[0079] Step 3: Add hydrochloric acid with a concentration of 37% to the effluent of Step 2 to control the pH of the effluent to 2.1.

[0080] Step 4: Slowly pass O3 into the effluent of Step 3 at 22°C at a molar ratio of O3 : I - =1:2, and stir the reaction for 1.5 h after adding O3. During this period, pay special attention to the oxidation-reduction potential (ORP) of the solution system. By controlling the flow rate of O3, ensure that the ORP of the solution is always between 520 mV and 550 mV.

[0081] Step 5: Add 3 g / L of modified activated carbon to the effluent of Step 4, stir for 2 h at 30°C, and then filter the water sample. The iodine content in the filtrate is 0.21 mg / L.

[0082] Example 4

[0083] The composition of the miscellaneous salt of a factory in Shandong Province is as follows:

[0084]

[0085] The iodine removal process of the miscellaneous salt provided in this embodiment includes the following steps:

[0086] Step 1: Add miscellaneous salt to water with a water temperature of 27°C according to the ratio of miscellaneous salt: water = 0.15:1 by mass, fully stir for 20 min, and then filter. The filtrate is light yellow and transparent, and the iodine content in the water is 11.43 mg / L;

[0087] Step 2: Add liquid alkali to the filtrate of Step 1, control the pH of the water sample to be 9.8, and flow into the adsorption column filled with chelating resin D402 in a down-up manner at a flow rate of 3 BV / h. The heavy metal content in the effluent is <1 mg / L, the Ca content is 0.231 mg / L, and the Mg content is 0.197 mg / L;

[0088] Step 3: Add hydrochloric acid with a concentration of 37% to the effluent of Step 2, and control the pH of the effluent to be 3.5;

[0089] Step 4: Slowly introduce O3 into the effluent of Step 3 at 28°C, with a molar ratio of O3: I - =1:2, and react for 2 h after the introduction of O3. During this period, pay special attention to the oxidation-reduction potential (ORP) in the water. By controlling the flow rate of O3 introduction, the ORP of the solution is always maintained at 520 mV~550 mV;

[0090] Step 5: Add 2 g / L of modified activated carbon to the effluent of Step 4 for adsorption, stir at 20°C for 2 h, filter the water sample, and continue to add 1 g / L of modified activated carbon to the filtered water sample. Stir at 20°C for 1.5 h and filter. The iodine content in the filtrate is 0.15 mg / L.

[0091] Example 5

[0092] The composition of the miscellaneous salt of a factory in Shandong Province is as follows:

[0093]

[0094] The iodine removal process of the miscellaneous salt provided in this embodiment includes the following steps:

[0095] Step 1: Add miscellaneous salt to water with a water temperature of 27°C according to the ratio of miscellaneous salt: water = 0.15:1 by mass, fully stir for 20 min, and then filter. The filtrate is light yellow and transparent, and the iodine content in the water is 11.43 mg / L;

[0096] Step 2: Add liquid alkali to the filtrate of Step 1, control the pH of the water sample to 9, flow into the adsorption column filled with chelating resin PM401 in the way of up-in and down-out at the flow rate of 2.1 BV / h, the heavy metal in the effluent is less than 1 mg / L, the Ca in the effluent is 0.207 mg / L, and the Mg in the effluent is 0.211 mg / L;

[0097] Step 3: Add hydrochloric acid with the concentration of 37% to the effluent of Step 2, control the pH of the effluent to 2.8;

[0098] Step 4: At 28℃, add NaClO solution with the concentration of 15% to the effluent of Step 3 drop by drop, the molar ratio of NaClO : I - = 1:2, stir the reaction for 1.5 h after adding the NaClO solution, and pay attention to the oxidation-reduction potential (ORP) of the solution system during the period, and ensure that the ORP of the solution is always between 520 mV and 550 mV by controlling the adding speed of NaClO.

[0099] Step 5: Add 3 g / L modified activated carbon to the effluent of Step 4, stir at 25℃ for 1.5 h, then filter the water sample, and the iodine content in the filtrate is 0.2 mg / L.

[0100] Example 6

[0101] The composition analysis of the miscellaneous salt of a factory in Gansu is as follows:

[0102]

[0103] The deiodization process of the miscellaneous salt provided in the embodiment includes the following steps:

[0104] Step 1: Add the miscellaneous salt to the water with the water temperature of 27℃ according to the ratio of miscellaneous salt: water = 0.17:1, stir thoroughly for 20 min, and then filter, the filtrate is light yellow and transparent, the iodine content in the water is 14.39 mg / L, and the fluorine content in the water is 16.15 mg / L;

[0105] Step 2: Add liquid alkali to the filtrate of Step 1, control the pH of the water sample to 9.5, flow into the adsorption column filled with chelating resin D401 in the way of up-in and down-out at the flow rate of 1.8 BV / h, the heavy metal in the effluent is less than 1 mg / L, the Ca in the effluent is 0.176 mg / L, and the Mg in the effluent is 0.188 mg / L;

[0106] Step 3: Add hydrochloric acid with the concentration of 37% to the effluent of Step 2, control the pH of the effluent to 2.5;

[0107] Step 4: At 22℃, add NaClO solution to the effluent of Step 3 drop by drop, the molar ratio of NaClO : I -=1:2, after adding NaClO solution, stirring the reaction for 2h, during which the solution system's oxidation reduction potential (ORP) needs to be focused on, by controlling the adding speed of NaClO, ensuring that the solution ORP is always between 520mV~550mV;

[0108] Step 5: 2g / L of modified activated carbon was added to the effluent of step 4, after stirring for 2h at 25℃, the water sample was filtered, the iodine content of the filtrate was 0.21mg / L, and the fluorine content was 14.67mg / L.

[0109] Example 7

[0110] The composition of the miscellaneous salt of a certain factory in Henan Province is as follows:

[0111]

[0112] The deiodization process of the miscellaneous salt provided in this example includes the following steps:

[0113] Step 1: Add miscellaneous salt to water with a water temperature of 21℃ according to the mass ratio of miscellaneous salt:water=0.17:1, stir thoroughly for 20min, and then filter. The filtrate is very light yellow and transparent, and the iodine content in the solution is 14.4mg / L;

[0114] Step 2: Add liquid alkali to the filtrate of step 1, control the water sample pH=9.5, and flow into the adsorption column filled with chelating resin D401 at a flow rate of 2BV / h in a down-up mode. The heavy metal content of the effluent is <1mg / L, the Ca content of the effluent is 0.164mg / L, and the Mg content of the effluent is 0.197mg / L;

[0115] Step 3: Add 37% hydrochloric acid to the effluent of step 2, and control the effluent pH=3.5;

[0116] Step 4: Add 15% NaClO solution to the effluent of step 3 drop by drop, and control the molar ratio of NaClO:I - =1:2, after adding NaClO solution, stirring the reaction for 2h, during which the solution system's oxidation reduction potential (ORP) needs to be focused on, by controlling the adding speed of NaClO, ensuring that the solution ORP is always between 520mV~550mV;

[0117] Step 5: Add 2g / L of modified activated carbon to the effluent of step 4, stir for 1.5h at 35℃, and then filter the water sample. The iodine content of the effluent is 0.18mg / L.

[0118] Comparative Example 1

[0119] This comparative example provides a deiodization process for miscellaneous salt, which is only different from Example 5 in that:

[0120] Step 4: To the effluent of Step 3, a NaClO solution with a concentration of 15% was added at 28°C, with a molar ratio of NaClO : I - =1:2. After the addition of the NaClO solution, the reaction was stirred for 1.5 h, during which the oxidation-reduction potential (ORP) of the solution system was not controlled by adjusting the addition rate of NaClO. It was monitored that the ORP of the solution exceeded 550 mV.

[0121] The water sample was filtered, and the iodine content in the filtrate was 2.98 mg / L.

[0122] Comparative Example 2

[0123] This comparative example provides a process for removing iodine from a mixed salt, which is only different from Example 6 in that:

[0124] Step 5: 2 g / L of activated carbon (not zirconium-modified) was added to the effluent of Step 4, and after stirring at 25°C for 2 h, the water sample was filtered. The iodine content in the filtrate was 3.92 mg / L, and the fluorine content was 15.35 mg / L.

[0125] Comparative Example 3

[0126] This comparative example provides a process for removing iodine from a mixed salt, which is only different from Example 7 in that:

[0127] Step 5: 3 g / L of activated carbon (not zirconium-modified) was added to the effluent of Step 4, and after stirring at 35°C for 1.5 h, the water sample was filtered. The iodine content in the filtrate was 2.55 mg / L.

[0128] Although the present application has been described in detail above with general description and specific examples, some modifications or improvements can be made on the basis of the present application, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not deviating from the spirit of the present application, all belong to the scope of the present application claimed.

Claims

1. A process for the removal of iodine from a hetero salt characterized in that, The process comprises the following steps: (1) Dissolve sodium chloride impurities in water, filter out insoluble substances to obtain a filtrate; (2) Add sodium hydroxide to the filtrate to adjust the pH to alkaline, remove heavy metals and calcium and magnesium by adsorption to obtain an adsorbed solution; (3) Add hydrochloric acid to the adsorbed solution to adjust the pH to acidic to obtain an acidic solution; (4) Oxidize the acidic solution by advanced oxidation technology to obtain an oxidized solution; (5) Add modified activated carbon to the oxidized solution, stir, separate the solid and liquid phases, and collect the liquid phase.

2. The process for deiodination of a hetero salt according to claim 1, characterized in that, In step (1), The mass ratio of sodium chloride impurities to water is 0.15-0.2:1; The temperature of the dissolution is 15-35°C.

3. The process for deiodination of a hetero salt according to claim 1, characterized in that, In step (2), The pH is 9-10; The adsorption uses an adsorption column filled with chelating resin, and the chelating resin includes D401, D402, PM401, and D851.

4. The process for deiodination of a hetero salt according to claim 1, characterized in that, In step (3), The concentration of the hydrochloric acid is 30%-37%, and the pH is 2-4.

5. The process for deiodination of a hetero salt according to claim 1, characterized in that, In step (4), the advanced oxidation technology includes one or a combination of several of the following: reagent oxidation, ozone oxidation, and ozone catalytic oxidation.

6. The process for deiodination of a hetero salt according to claim 5, characterized in that, Slowly adding a medicament or slowly passing ozone into an acidic solution, the medicament being NaClO or H2O2, the medicament or ozone and I - in the acidic solution are in a molar ratio of 1:1.95~2.05, stirring for 1~2h at 10~35℃, and controlling the oxidation-reduction potential of the oxidation system to be 520mV~550mV at all times.

7. The process for deiodination of a hetero salt according to claim 1, characterized in that, In step (5), The amount of the modified activated carbon added is 1 g / L-5 g / L; The stirring conditions are 10-35°C and 1-2 h.

8. The process for deiodination of a hetero salt according to claim 1, characterized in that, The preparation method of the modified activated carbon is as follows: (1) Steam the powdered activated carbon in hot water, filter, and dry to obtain activated carbon; (2) Prepare an activated carbon water suspension from the activated carbon, simultaneously add a zirconium salt solution and an acid, after the addition is complete, stir, filter, and wash with water until neutral to obtain activated carbon loaded with zirconium; (3) Disperse the activated carbon loaded with zirconium in water, add polyethyleneimine for ultrasonic dispersion, expose to air while heating, and then add a lye solution for alkalization; (4) After the addition is complete, continue to expose to air, stir, separate the solid and liquid phases, wash with water, and dry to constant weight to obtain the modified activated carbon.

9. The process for removing iodine from impurities according to claim 8, wherein In step (1), the powdered activated carbon is selected from one or more of coconut shell activated carbon, wood-based activated carbon, and coal-based activated carbon, and the particle size is 150-500 mesh; the steaming conditions are 900-100°C for 2-4 h; and the drying conditions are 100-110°C for 2-3 h; In step (2), the concentration of the activated carbon water suspension is 10 g / L-40 g / L; the zirconium salt solution is an aqueous solution of a zirconium salt, and the concentration is 0.1-1 mol / L; the zirconium salt is selected from one or more of zirconium sulfate, zirconium nitrate, zirconium chloride, and zirconium acetate; the acid is selected from one or more of sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid; the mass ratio of the activated carbon to the zirconium salt is 100:0.05-3, and the amount-of-substance ratio of the acid to the zirconium salt is 1-5:5-1; the temperature of the addition is 50-70°C; and the stirring conditions are 60-90°C for 3-6 h.

10. The process for removing iodine from impurities according to claim 8, wherein In step (3), the aeration amount of air is 20-30 L / min; the heating condition is that the temperature is increased from room temperature to 50-70℃ at a temperature increase rate of not more than 1 degree / min; the alkali solution is an aqueous solution of alkali, the concentration is 0.05-3 mol / L, and the alkali is selected from one or more of sodium hydroxide, potassium hydroxide and calcium hydroxide; the alkalization condition is that the temperature is 30-60℃, the pH is 10-12, and the mass ratio of activated carbon to polyethyleneimine is 100:0.01-1. In step (4), the aeration amount of air is 5-15 L / min, and the stirring condition is that the temperature is 70-95℃ for 5-10 min.

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