CN105399179A - A method of removing ionic liquid in a water body by activated carbon adsorption promoted by utilization of phosphates - Google Patents

Abstract

The invention relates to a method for using phosphate to promote active carbon adsorption to remove ionic liquid in water, belonging to the field of water pollution control. The method is as follows: add phosphate to the water body containing ionic liquid, fully mix and dissolve; use activated carbon to adsorb the ionic liquid in the water body, and after reaching adsorption equilibrium or adsorption saturation, firstly use an acidic eluent to elute the ionic liquid, and then Adjust the pH of the activated carbon to weak alkaline with alkaline solution, so that the activated carbon can be reused in the next round of adsorption. Compared with the prior art, the invention significantly improves the ability of the activated carbon to adsorb and remove the ionic liquid by utilizing the phosphate. The present invention does not need to perform other additional operations, and the adsorption and removal effect on the ionic liquid is significantly improved, and the activated carbon can be reused for many times, thus having a good promotion and application prospect.

Description

The method of using phosphate to promote the adsorption of activated carbon to remove ionic liquid in water

technical field

The invention relates to an ionic liquid treatment method, in particular to a method for using phosphate to promote the adsorption of activated carbon to remove the ionic liquid in water, belonging to the field of water pollution control.

Background technique

Ionic liquids refer to molten salt compounds that are liquid at room temperature and are completely composed of anions and cations. It is difficult to volatilize, stable to water and air, and has excellent solubility for various substances, so it is called "green solvent" and is widely used in chemical, pharmaceutical, biotechnology, agriculture and food fields. The ionic liquids entering the environmental water body are not easy to be degraded by microorganisms, and have certain toxicity to animals, plants and microorganisms. Therefore, reasonable and effective disposal of ionic liquids contained in industrial water bodies must be carried out.

At present, there are two main methods for the treatment of ionic liquid solutions. One is to destroy the structure of ionic liquids and convert ionic liquids into other harmless or low-toxic small molecules. Relevant measures include pyrolysis, chemical oxidation, and biological treatment; such methods cannot effectively recover resources of ionic liquids in water bodies. Another method is to effectively separate and recover ionic liquids from water, and the main measures include vacuum distillation, crystallization, extraction, and adsorption. Among them, the methods of vacuum distillation, crystallization and extraction are not suitable for large-scale treatment of water containing ionic liquids. Therefore, adsorption is the recommended method. At present, although there are reports in the literature on the use of activated carbon to adsorb and treat ionic liquid water, the ability of activated carbon to adsorb ionic liquid is generally very low. If it is applied industrially with the existing technical parameters, the treatment cost will remain high.

Contents of the invention

What the present invention needs to solve is the problem that the adsorption capacity of ionic liquids (especially hydrophilic ionic liquids) on activated carbon is not high. At present, the main improvement method is to increase the amount of activated carbon, which will lead to an increase in treatment costs. In the present invention, by adding a small amount of phosphate into the water body, the activated carbon can significantly improve the adsorption capacity of the ionic liquid without changing other technical parameters.

The purpose of the present invention can be achieved through the following technical solutions:

Using phosphate to promote the adsorption of activated carbon to remove ionic liquids in water, add phosphate to the water containing ionic liquids, fully mix and dissolve; use activated carbon to adsorb ionic liquids in water, after reaching adsorption equilibrium or adsorption saturation, first use The acidic eluent elutes the ionic liquid, and then the pH of the activated carbon is adjusted to a weak alkalinity greater than 8.0 with an alkaline solution, so that the activated carbon can be reused in the next round of adsorption.

The ionic liquid in water includes imidazole ionic liquid, pyridine ionic liquid, quaternary ammonium ionic liquid, quaternary phosphine ionic liquid, pyrrolidine ionic liquid or piperidine ionic liquid.

The phosphate includes sodium phosphate, potassium phosphate or ammonium phosphate.

After the phosphate is added, the ratio of the molar concentration of the phosphate in the water to the molar concentration of the ionic liquid is maintained in the range of 1/500 to 1/50.

The acid eluent includes hydrochloric acid or sulfuric acid solution with pH=1-3.

The alkaline solution includes sodium hydroxide or potassium hydroxide aqueous solution with pH=11-13.

The way activated carbon adsorbs ionic liquids in water is static equilibrium adsorption mode or dynamic column adsorption mode.

The static equilibrium adsorption mode is: add a small amount of phosphate to a certain amount of water containing ionic liquids, further add a certain quality of activated carbon, fully oscillate to make the activated carbon adsorb ionic liquids to reach equilibrium, filter out the activated carbon, and put in an acidic eluent In the process, the ionic liquid adsorbed by the activated carbon will be desorbed into the acidic eluent, then the activated carbon is taken out from the acidic eluent, placed in an alkaline solution, and the pH of the activated carbon is adjusted to be weakly alkaline, so that the activated carbon can be reused.

The dynamic column adsorption mode is as follows: a certain quality of activated carbon is filled in the column, and under the condition of a stable flow rate, the water containing ionic liquid and a small amount of phosphate flows through the activated carbon-filled column for column adsorption. 1 bed volume of acidic eluent is used to elute the adsorption column, and then 1 bed volume of distilled water is used to elute the adsorption column. The pH is adjusted back to weak alkaline, so that the activated carbon can be reused.

The adsorption conditions of static equilibrium adsorption mode or dynamic column adsorption mode can refer to the conventional activated carbon adsorption process.

The principle of the invention is: the trivalent phosphate has a salting-out effect, and can strongly hydrate the water molecules of the free solvent through electrostatic action, thereby effectively reducing the hydration between the water molecules and the ionic liquid, and further reducing the solubility of the ionic liquid in the water body.

Compared with the prior art, the present invention only needs to add a small amount of phosphate solution into the water body to greatly promote the adsorption effect of the activated carbon on the ionic liquid, and the cost is low and the effect is remarkable.

detailed description

The present invention will be described in detail below in conjunction with specific embodiments.

Example 1:

Sodium Phosphate Promotes Static Adsorption of Ionic Liquids (1-Ethyl-3-methylimidazolium Tetrafluoroborate) on Activated Carbon

[Dosing sodium phosphate experiment] The specific steps are: add a small amount of sodium phosphate to the 1mmol/L 1-ethyl-3-methylimidazolium tetrafluoroborate aqueous solution to be treated, and the concentration of sodium phosphate after stabilization is 0.01 mmol/L. A certain amount of powdered commercial activated carbon was further added and oscillated for 24 hours. After the adsorption reached equilibrium, the saturated adsorption capacity of activated carbon for 1-ethyl-3-methylimidazolium tetrafluoroborate was measured to be 40.6 mg/g. When placed in a hydrochloric acid solution with pH=1, 1-ethyl-3-methylimidazolium tetrafluoroborate can be completely desorbed by the acid solution. Put the activated carbon in the sodium hydroxide aqueous solution with pH = 13, and the pH of the activated carbon can be adjusted to a weak alkalinity of 10. Activated charcoal can be reused many times.

[Comparative experiment without adding sodium phosphate] The specific steps are: add a certain amount of powdered commercial activated carbon to the 1mmol/L 1-ethyl-3-methylimidazolium tetrafluoroborate aqueous solution to be treated, shake for 24h, After the adsorption reached equilibrium, it was measured that the saturated adsorption capacity of activated carbon to 1-ethyl-3-methylimidazolium tetrafluoroborate was 16.2 mg/g, and then the activated carbon was taken out and washed with distilled water. Putting it into a hydrochloric acid solution with pH=1, all the adsorbed ionic liquid will be desorbed into the acid solution.

Comparing the adsorption capacity of activated carbon before and after adding sodium phosphate, the adsorption capacity of activated carbon on ionic liquids before and after adding sodium phosphate was increased by about 2.5 times, which proved that phosphate can effectively promote the adsorption of activated carbon on ionic liquids.

Example 2:

Ammonium Phosphate Facilitated Static Adsorption of Ionic Liquids on Activated Carbon (N-Butyl-3-methylpyridine Hexafluorophosphate)

[Ammonium phosphate addition experiment] The specific steps are: add a small amount of ammonium phosphate to the 1mmol/L N-butyl-3-methylpyridine hexafluorophosphate aqueous solution to be treated, and the concentration of ammonium phosphate after stabilization is 0.01mmol /L. Further add a certain amount of powdered commercial activated carbon and oscillate for 24 hours. After the adsorption reaches equilibrium, the saturated adsorption capacity of activated carbon for N-butyl-3-methylpyridine hexafluorophosphate is measured to be 56.6 mg/g. When placed in a sulfuric acid solution with pH=1, N-butyl-3-picoline hexafluorophosphate can be completely desorbed by the acid solution. Put the activated carbon in the potassium hydroxide aqueous solution with pH = 13, and the pH of the activated carbon can be adjusted to 9.5 weakly alkaline. Activated charcoal can be reused many times.

[Comparative experiment without adding ammonium phosphate] The specific steps are: add a certain amount of powdered commercial activated carbon to the 1mmol/L N-butyl-3-picoline hexafluorophosphate aqueous solution to be treated, shake for 24 hours, and wait for After the adsorption reaches equilibrium, the saturated adsorption capacity of N-butyl-3-picoline hexafluorophosphate measured by activated carbon is 29.0 mg/g, and then the activated carbon is taken out and washed with distilled water. Putting it into a sulfuric acid solution with pH=1, all the adsorbed ionic liquid will be desorbed into the acid solution.

Comparing the adsorption capacity of activated carbon before and after adding ammonium phosphate, the adsorption capacity of activated carbon on ionic liquids before and after adding ammonium phosphate was increased by about 2.0 times, which proved that phosphate can effectively promote the adsorption of activated carbon on ionic liquids.

Example 3:

Dynamic adsorption of ionic liquid (1-ethyl-3-methylimidazolium hexafluorophosphate) on activated carbon column

[Dosing potassium phosphate experiment] The specific steps are: add a small amount of potassium phosphate to the 1mmol/L 1-ethyl-3-methylimidazolium hexafluorophosphate aqueous solution to be treated, and the concentration of potassium phosphate after stabilization is 0.01mmol /L. Take 10g of granular activated carbon to fill a glass column with an inner diameter of 1cm and a height of 10cm. Under the condition of a steady flow rate, the above solution was flowed through an activated carbon packed column for column adsorption, and it was measured that the volume of the solution that reached adsorption saturation was 1600ml. Drain the solution in the column, add 1 bed volume of hydrochloric acid solution with pH=1 to elute, then use 1 bed volume of distilled water to elute the adsorption column, 1-ethyl-3-methylimidazole hexafluorophosphate can be completely desorbed. Then add 1 bed volume of potassium hydroxide aqueous solution with pH=13, the pH of activated carbon can be adjusted to weak alkalinity of 9.0. Activated charcoal can be reused many times.

[Comparative experiment without adding potassium phosphate] The specific steps are: without adding potassium phosphate, other treatment operations are the same as [experiment of adding sodium phosphate].

Comparing the solution treatment volume before and after adding phosphate, the treatment water volume before dosing is 500ml, and the treatment water volume after dosing is 1600ml, and the adsorption treatment volume is increased by about 3.2 times.

Example 4:

Dynamic adsorption of ionic liquid (N-butyl-3-picoline chloride) on activated carbon column

[Dosing sodium phosphate experiment] The specific steps are: add a small amount of sodium phosphate to the 1mmol/L aqueous solution of N-butyl-3-picoline chloride to be treated, and the concentration of sodium phosphate after stabilization is 0.01mmol/L . Take 10g of granular activated carbon to fill a glass column with an inner diameter of 1cm and a height of 10cm. Under the condition of a steady flow rate, the above solution was flowed through an activated carbon packed column for column adsorption, and it was measured that the volume of the solution that reached adsorption saturation was 2000 ml. Drain the solution in the column, add 1 bed volume of sulfuric acid solution with pH=1 for elution, then use 1 bed volume of distilled water to elute the adsorption column, N-butyl-3-picoline can be completely removed attached. Then add 1 bed volume of sodium hydroxide aqueous solution with pH=13, the pH of activated carbon can be adjusted to the weak alkalinity of pH9.5. Activated charcoal can be reused many times.

[Comparative experiment without adding sodium phosphate] The specific steps are: without adding sodium phosphate, other treatment operations are the same as [experiment of adding sodium phosphate].

Comparing the solution treatment volume before and after adding phosphate, the treatment water volume before dosing is 600ml, and the treatment water volume after dosing is 2000ml, and the adsorption treatment volume is increased by 3.3 times.

Example 5

Utilize phosphate to promote activated carbon adsorption to remove the method of ionic liquid in water body,

Sodium Phosphate Promotes Static Adsorption of Ionic Liquids (1-Ethyl-3-methylimidazolium Tetrafluoroborate) on Activated Carbon

[Dosing sodium phosphate experiment] The specific steps are: add a small amount of sodium phosphate to the 1mmol/L 1-ethyl-3-methylimidazolium tetrafluoroborate aqueous solution to be treated, and the concentration of sodium phosphate after stabilization is 0.002 mmol/L. A certain amount of powdered commercial activated carbon was further added and oscillated for 24 hours. After the adsorption reached equilibrium, the saturated adsorption capacity of activated carbon for 1-ethyl-3-methylimidazolium tetrafluoroborate was measured to be 28.8 mg/g. When placed in a sulfuric acid solution with pH=3, 1-ethyl-3-methylimidazolium tetrafluoroborate can be completely desorbed by the acid solution. Put the activated carbon in the potassium hydroxide aqueous solution with pH = 13, and the pH of the activated carbon can be adjusted to a weak alkalinity of 10. Activated charcoal can be reused many times.

[Comparative experiment without adding sodium phosphate] The specific steps are: add a certain amount of powdered commercial activated carbon to the 1mmol/L 1-ethyl-3-methylimidazolium tetrafluoroborate aqueous solution to be treated, shake for 24h, After the adsorption reached equilibrium, it was measured that the saturated adsorption capacity of activated carbon to 1-ethyl-3-methylimidazolium tetrafluoroborate was 16.2 mg/g, and then the activated carbon was taken out and washed with distilled water. When placed in a sulfuric acid solution with pH=3, all the adsorbed ionic liquids are desorbed into the acid solution.

Comparing the adsorption capacity of activated carbon before and after adding sodium phosphate, the adsorption capacity of activated carbon on ionic liquids before and after adding sodium phosphate was increased by about 1.8 times, which proved that phosphate can effectively promote the adsorption of activated carbon on ionic liquids.

Example 6

Utilize phosphate to promote activated carbon adsorption to remove the method of ionic liquid in water body,

Sodium Phosphate Promotes Static Adsorption of Ionic Liquids (1-Ethyl-3-methylimidazolium Tetrafluoroborate) on Activated Carbon

[Dosing sodium phosphate experiment] The specific steps are: add a small amount of sodium phosphate to the 1mmol/L 1-ethyl-3-methylimidazolium tetrafluoroborate aqueous solution to be treated, and the concentration of sodium phosphate after stabilization is 0.002 mmol/L. A certain amount of powdered commercial activated carbon was further added and oscillated for 24 hours. After the adsorption reached equilibrium, the saturated adsorption capacity of activated carbon for 1-ethyl-3-methylimidazolium tetrafluoroborate was measured to be 50.5 mg/g. When placed in a hydrochloric acid solution with pH=2, 1-ethyl-3-methylimidazolium tetrafluoroborate can be completely desorbed by the acid solution. Put the activated carbon in the sodium hydroxide aqueous solution with pH = 12, and the pH of the activated carbon can be adjusted to a weak alkalinity of 10. Activated charcoal can be reused many times.

[Comparative experiment without adding sodium phosphate] The specific steps are: add a certain amount of powdered commercial activated carbon to the 1mmol/L 1-ethyl-3-methylimidazolium tetrafluoroborate aqueous solution to be treated, shake for 24h, After the adsorption reached equilibrium, it was measured that the saturated adsorption capacity of activated carbon to 1-ethyl-3-methylimidazolium tetrafluoroborate was 16.2 mg/g, and then the activated carbon was taken out and washed with distilled water. When placed in a hydrochloric acid solution with pH=2, all the adsorbed ionic liquids are desorbed into the acid solution.

Comparing the adsorption capacity of activated carbon before and after adding sodium phosphate, the adsorption capacity of activated carbon on ionic liquids before and after adding sodium phosphate was increased by about 3.1 times, which proved that phosphate can effectively promote the adsorption of activated carbon on ionic liquids.

The above descriptions of the embodiments are for those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described here to other embodiments without creative efforts. Therefore, the present invention is not limited to the above-mentioned embodiments. Improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims (9)

1. Utilize phosphate to promote the method for activated carbon adsorption to remove ionic liquid in water body, it is characterized in that, Add phosphate to the water body containing the ionic liquid, mix well and dissolve; Use activated carbon to adsorb the ionic liquid in the water body. After reaching the adsorption equilibrium or adsorption saturation, first use the acidic eluent to elute the ionic liquid, and then use the alkaline solution to adjust the pH of the activated carbon to a weak alkaline range greater than 8.0, so that the activated carbon can be reused in the next round of adsorption. 2. the method utilizing phosphate to promote activated carbon adsorption and removal of ionic liquid in water according to claim 1, is characterized in that, the ionic liquid in water comprises imidazole ionic liquid, pyridine ionic liquid, quaternary ammonium ionic liquid, quaternary ionic liquid Phosphine-based ionic liquid, pyrrolidine-based ionic liquid or piperidine-based ionic liquid. 3. The method for utilizing phosphate to promote activated carbon adsorption and removal of ionic liquid in water according to claim 1, wherein said phosphate comprises sodium phosphate, potassium phosphate or ammonium phosphate. 4. the method utilizing phosphate to promote activated carbon adsorption and removal of ionic liquid in water according to claim 1, is characterized in that, after adding phosphate, the ratio of the molar concentration of phosphate and the molar concentration of ionic liquid in the water body is 1/ 500 to 1/50. 5 . The method for utilizing phosphate to promote adsorption and removal of ionic liquids in water by activated carbon according to claim 1 , wherein the acidic eluent comprises hydrochloric acid or sulfuric acid solution with a pH of 1-3. 6. The method for utilizing phosphate to promote adsorption of activated carbon to remove ionic liquids in water according to claim 1, wherein the alkaline solution comprises an aqueous solution of sodium hydroxide or potassium hydroxide with a pH of 11-13. 7. The method for utilizing phosphate to promote activated carbon adsorption and removal of ionic liquids in water bodies according to claim 1, characterized in that the mode of activated carbon adsorption of ionic liquids in water bodies is a static equilibrium adsorption mode or a dynamic column adsorption mode. 8. the method for utilizing phosphate to promote activated carbon adsorption and removal of ionic liquid in water according to claim 7, characterized in that, the static equilibrium adsorption mode is: add a small amount of phosphate to a certain amount of water containing ionic liquid, and further add Add a certain amount of activated carbon, fully oscillate to make the activated carbon adsorb the ionic liquid to reach equilibrium, filter the activated carbon, put it into the acidic eluent, the ionic liquid adsorbed by the activated carbon will be desorbed into the acidic eluent, and then remove the activated carbon from the acidic eluent Take it out from the eluent, place it in an alkaline solution, and adjust the pH of the activated carbon to a weak alkaline greater than 8.0, so that the activated carbon can be reused. 9. the method for utilizing phosphate to promote activated carbon adsorption and removal of ionic liquids in water according to claim 7, characterized in that, the dynamic column adsorption mode is: fill a certain quality of activated carbon in the column, under the condition of steady flow rate, use The water body of ionic liquid and a small amount of phosphate flows through the activated carbon packed column for column adsorption. After the adsorption reaches saturation, the water body is drained, and the adsorption column is eluted with 1 bed volume of acidic eluent, and then 1 bed volume of distilled water. The adsorption column, the ionic liquid is completely desorbed, and the adsorption column is further rinsed with a bed volume of alkaline solution, and the pH of the activated carbon is adjusted back to a weak alkalinity greater than 8.0, so that the activated carbon can be reused.