Background
The natural organic high molecular compounds such as cellulose and the like have wide sources and abundant reserves, can obtain various products through dissolution, regeneration, processing and other treatments, and are widely applied to the fields of chemical industry, textile, food, medicine, biological materials and the like. At present, organic reagents such as N-methylmorpholine-N-oxide (NMMO), formaldehyde, acetone, carboxylic acid and the like and inorganic reagents such as sulfite, sodium sulfide, sulfuric acid, zinc sulfate, carbon disulfide and the like are mainly used as solvents and additives in the production of natural organic high molecular compounds, however, the organic reagents have volatility, can generate adverse effects on the environment and the health of operators, and the inorganic reagents have strong corrosiveness, so that equipment is seriously depreciated and lost; in addition, chemical reagents generated in production cannot be directly discharged, subsequent recovery and treatment processes are complicated, and the recovery utilization rate is extremely low.
The ionic liquid is a green solvent with great application prospect emerging in recent years, is widely applied to the research in the fields of electrochemistry, organic synthesis, chemical separation, material preparation and the like by virtue of unique excellent performances of strong polarity, non-volatility, stability to water and air and the like, and is known as an environment-friendly solvent capable of replacing volatile solvents in a plurality of fields.
In a production process of dissolving an organic polymer compound such as cellulose in an ionic liquid, a degradation process of the organic polymer compound and a water addition process required for organic matter regeneration are accompanied, so that a large amount of an ionic liquid aqueous solution containing metal ions is generated and accumulated in the recycled ionic liquid. After reaching a certain amount, the foreign metal ions will affect the strength and performance of the regenerated organic matter. Therefore, the metal ions in the ionic liquid aqueous solution must be removed.
However, in existing ionic liquid recovery processes, little consideration is given to the removal of metal ions from ionic liquid systems. Therefore, the method for removing the metal ions in the ionic liquid system, which has the advantages of high efficiency, low energy consumption and simple process, is developed to realize the efficient recycling of the ionic liquid, and is the research focus in the field.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for removing metal ions in an ionic liquid system aiming at the defects of the prior art. The method can effectively remove the metal ions in the ionic liquid aqueous solution to obtain the purified ionic liquid. Provides technical support for the resource recycling of the ionic liquid, and has the advantages of high efficiency, simple process, low energy consumption and the like.
The method comprises the steps of firstly introducing an ionic liquid aqueous solution containing metal ions into a purification device containing a metal ion remover for adsorption reaction, and then separating the metal ion remover adsorbed with the metal ions from feed liquid removed with the metal ions; the metal ion remover adsorbed with metal ions is recycled after regeneration; wherein the metal ion remover is cellulose-chitosan microspheres.
In the invention, the preparation process of the cellulose-chitosan microsphere comprises the following steps: placing cellulose, chitosan and ionic liquid into a reaction kettle, stirring and dissolving, controlling the reaction temperature to be 90-100 ℃, after the cellulose and the chitosan are completely dissolved, dropwise adding the dissolved ionic liquid-cellulose-chitosan mixed solution into water, and replacing the water once every 6 hours until the ionic liquid is completely replaced, thus obtaining cellulose-chitosan beads; and (3) drying the prepared cellulose-chitosan microspheres in a drying oven at the temperature of 80-100 ℃ for 6 hours to obtain the cellulose-chitosan microspheres.
In the invention, the ionic liquid used in the preparation process of the cellulose-chitosan microsphere is the same as the ionic liquid in the ionic liquid aqueous solution containing metal ions.
In the preparation process of the cellulose-chitosan microsphere, the mass ratio of cellulose to chitosan to ionic liquid is 1:1 (30-40).
As a preferred technical scheme, in the preparation process of the cellulose-chitosan microsphere, the loss of ionic liquid in an ionic liquid aqueous solution containing metal ions in a purification stage can be avoided by dissolving cellulose and chitosan by using the ionic liquid, and meanwhile, the introduction of impurities can also be prevented; the addition of the cellulose increases the specific surface area of the microspheres and improves the removal rate of impurity metal ions; the addition of chitosan provides functional groups that coordinate to metal ions.
Preferably, the mass ratio of the cellulose to the chitosan to the ionic liquid in the preparation process of the cellulose-chitosan microspheres is 1:1 (30-40). If the mass ratio of the cellulose to the chitosan to the ionic liquid is lower than 1:1:30, the cellulose and the chitosan are not completely dissolved, which is not beneficial to the preparation of the follow-up microspheres; moreover, the cellulose and chitosan are not completely dissolved, so that the prepared microspheres are not uniform; if the mass ratio of the cellulose to the chitosan to the ionic liquid is higher than 1:1:40, the ionic liquid proportion in the obtained cellulose-chitosan pellets is too high, and the subsequent ionic liquid replacement process and energy consumption are increased.
In the present invention, the temperature of the adsorption reaction is 20 to 100 ℃, preferably the temperature of the adsorption reaction is 25 to 50 ℃, for example, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, and the specific values therebetween are limited by space and in the light of conciseness, and the specific values included in the range are not exhaustive.
According to the invention, a cellulose-chitosan microsphere fixed bed reactor is used as a purification device, the number of the cellulose-chitosan microsphere fixed bed reactors is more than or equal to 1, and preferably 2-3. The flow rate of the ionic liquid aqueous solution containing the metal ions introduced into the purification device is 1-30 times of bed layer volume per hour, and preferably the flow rate of the ionic liquid aqueous solution containing the metal ions introduced into the purification device is 2-20 times of bed layer volume per hour. In addition, the purification apparatus of the present invention may employ a stirred tank reactor.
In the present invention, the metal ion is any 1 or 2 combination of iron metal ion and copper metal ion.
In the invention, the concentration of the ionic liquid in the ionic liquid aqueous solution containing metal ions is 0-15 g/L, such as 0g/L, 2g/L, 5g/L, 7g/L, 10g/L, 12g/L or 15g/L, and the specific values therebetween are limited by space and in the light of conciseness, and the invention does not exhaust the specific values included in the range.
In the present invention, the ionic liquid in the ionic liquid aqueous solution containing metal ions is selected from any 1 or 2 combinations of alkyl imidazolium salts and alkyl pyridinium salts.
In the invention, after metal ions are adsorbed and saturated on the cellulose-chitosan microspheres, the cellulose-chitosan microspheres which adsorb the metal ions to be saturated need to be regenerated by hydrochloric acid solution; preferably, the concentration of the hydrochloric acid solution is 0.01-0.02 mol/L.
As a preferable technical scheme of the invention, the concentration of the hydrochloric acid solution is 0.01-0.02 mol/L. If the concentration of the hydrochloric acid solution is lower than 0.01mol/L, the metal ions in the regenerated cellulose-chitosan microspheres are incompletely removed, so that the removal effect of the regenerated cellulose-chitosan microspheres on the metal ions is poor; if the concentration of the hydrochloric acid solution is higher than 0.02mol/L, the cellulose chitosan microspheres are lost in the regeneration process, and the service life of the cellulose-chitosan microspheres is shortened.
The invention has the beneficial effects that: the method is suitable for an ionic liquid system containing metal ions, and the metal ions are adsorbed by the cellulose-chitosan microspheres under specific adsorption conditions, so that the content of the metal ions in the ionic liquid is obviously reduced, the loss of the ionic liquid in the system is avoided, and the utilization rate of the ionic liquid is improved.
Detailed Description
In order that the invention may be readily understood, a detailed description of the invention is provided below.
The inventor researches and discovers that when the ionic liquid aqueous solution containing metal ions is contacted with the cellulose-chitosan microspheres for adsorption reaction, a large amount of metal ions can be adsorbed by the cellulose-chitosan microspheres, so that the metal ions in the ionic liquid aqueous solution containing the metal ions can be effectively removed. The invention is based on the above method.
Therefore, the method for removing the metal ions comprises the steps of introducing the ionic liquid aqueous solution containing the metal ions into a purification device containing a metal ion remover to perform adsorption reaction, and then separating the metal ion remover adsorbed with the impurity metal ions from the feed liquid removed with the impurity metal ions.
The metal ion remover used in the invention is prepared cellulose-chitosan microspheres, and the mechanism of the cellulose-chitosan microspheres for absorbing metal ions is mainly that a stable structure similar to a chelate can be formed by the coordination reaction of functional groups on the cellulose-chitosan microspheres and the metal ions, so that the metal ions are absorbed. The inventor researches and discovers that metal ions are removed by using the cellulose-chitosan microspheres, and the ionic liquid in the feed liquid is not lost.
In the embodiment of the invention, the ionic liquid used in the preparation process of the cellulose-chitosan microsphere is the same as the ionic liquid in the ionic liquid aqueous solution containing metal ions, and the mass ratio of cellulose to chitosan to the ionic liquid in the preparation process of the cellulose-chitosan microsphere is 1:1 (30-40).
In an embodiment of the present invention, cellulose-chitosan microspheres are placed in a cellulose-chitosan microsphere fixed bed reactor, and an ionic liquid aqueous solution containing metal ions is brought into sufficient contact with the cellulose-chitosan microspheres to adsorb the metal ions therein. An ionic liquid aqueous solution containing metal ions is passed through the fixed bed at a flow rate such that the metal ions are adsorbed by the cellulose-chitosan microspheres.
In the invention, 2-3 cellulose-chitosan microsphere fixed bed reactors are preferably used.
In some embodiments of the present invention, the temperature of the adsorption reaction is 20 to 100 ℃, and preferably, the temperature of the adsorption reaction is 25 to 50 ℃. Such as 25 deg.c, 30 deg.c, 35 deg.c, 40 deg.c, 45 deg.c, 50 deg.c, and specific values therebetween, are not intended to be exhaustive or to be in the interests of brevity and conciseness.
According to other embodiments of the present invention, a cellulose-chitosan microsphere fixed bed reactor is used as the purification device, the flow rate of the ionic liquid aqueous solution containing metal ions introduced into the purification device is 1 to 30 times of bed volume per hour, and preferably the flow rate of the ionic liquid aqueous solution containing metal ions introduced into the purification device is 2 to 20 times of bed volume per hour.
In the present invention, the metal ion is any 1 or 2 combination of iron metal ion and copper metal ion.
In the invention, the concentration of the ionic liquid in the ionic liquid aqueous solution containing metal ions is 0-15 g/L, such as 0g/L, 2g/L, 5g/L, 7g/L, 10g/L, 12g/L or 15g/L, and the specific values therebetween are limited by space and in the light of conciseness, and the invention does not exhaust the specific values included in the range.
In the present invention, the ionic liquid in the ionic liquid aqueous solution containing metal ions is selected from any 1 or 2 combinations of alkyl imidazolium salts and alkyl pyridinium salts.
In the invention, after the adsorption saturation of metal ions on the cellulose-chitosan microspheres, a hydrochloric acid solution is needed for regeneration; preferably, the concentration of the hydrochloric acid solution is 0.01-0.02 moL/L.
Examples
In order that the invention may be more readily understood, reference will now be made in detail to the present embodiments of the invention. It will be appreciated by persons skilled in the art that the examples described are merely illustrative of the invention and should not be construed as limiting the invention in any way.
In the following examples, the concentrations of iron ions and copper ions in the materials were each 100 ppm.
The experimental materials used in the following examples of the invention include:
the sample to be treated and cellulose are originated from a chemical fiber factory in the new country city of Henan province; chitosan was purchased from the national pharmaceutical group chemical agents limited.
The model of an apparatus used for ICP analysis in the following examples of the invention was Shimadzu ICPE-9000.
Example 1
The ionic liquid in the embodiment is 1-allyl-3-methylpyridine chloride ionic liquid.
The preparation process of the cellulose-chitosan microsphere in this embodiment is as follows: placing cellulose, chitosan and ionic liquid in a reaction kettle according to the mass ratio of 1:1:30, stirring and dissolving, controlling the reaction temperature to be 90 ℃, after the cellulose and the chitosan are completely dissolved, dropwise adding the dissolved ionic liquid-cellulose-chitosan mixed solution into water, and replacing water every 6 hours until the ionic liquid is completely replaced, thus obtaining cellulose-chitosan microspheres; and (3) drying the prepared cellulose-chitosan microspheres in a drying oven at the temperature of 80 ℃ for 6 hours to obtain the cellulose-chitosan microspheres for later use.
And (3) filling the prepared cellulose-chitosan microspheres into a cellulose-chitosan microsphere fixed bed reactor. Under the condition that the temperature is 25 ℃, the feed liquid to be treated, which does not contain the ionic liquid, is introduced into the cellulose-chitosan microsphere fixed bed reactor at the flow rate of 2 times of the bed layer volume, ICP analysis is carried out on the effluent solution, the removal condition of iron ions and copper ions is determined, and the result is shown in table 1.
Example 2
The ionic liquid in this example is 1-ethyl-3-methylimidazolium diethyl phosphate ionic liquid.
The preparation process of the cellulose-chitosan microsphere in this embodiment is as follows: placing cellulose, chitosan and ionic liquid in a reaction kettle according to the mass ratio of 1:1:40, stirring and dissolving, controlling the reaction temperature to be 100 ℃, after the cellulose and the chitosan are completely dissolved, dropwise adding the dissolved ionic liquid-cellulose-chitosan mixed solution into water, and replacing water every 6 hours until the ionic liquid is completely replaced, thus obtaining cellulose-chitosan microspheres; and (3) drying the prepared cellulose-chitosan microspheres in a drying oven at the temperature of 100 ℃ for 6 hours to obtain the cellulose-chitosan microspheres for later use.
And (3) filling the prepared cellulose-chitosan microspheres into a cellulose-chitosan microsphere fixed bed reactor. Under the condition of the temperature of 25 ℃, the feed liquid to be treated with the ionic liquid concentration of 5g/L is introduced into the cellulose-chitosan microsphere fixed bed reactor at the flow rate of 2 times of the bed layer volume, ICP is carried out on the effluent solution, and the removal conditions of iron ions and copper ions are determined, wherein the results are shown in Table 1.
Example 3
The ionic liquid in this example is 1-ethyl-3-methylimidazolium diethyl phosphate ionic liquid.
The preparation process of the cellulose-chitosan microsphere in this embodiment is as follows: placing cellulose, chitosan and ionic liquid in a reaction kettle according to the mass ratio of 1:1:35, stirring and dissolving, controlling the reaction temperature to be 100 ℃, after the cellulose and the chitosan are completely dissolved, dropwise adding the dissolved ionic liquid-cellulose-chitosan mixed solution into water, and replacing water every 6 hours until the ionic liquid is completely replaced, thus obtaining cellulose-chitosan microspheres; and (3) drying the prepared cellulose-chitosan microspheres in a drying oven at the temperature of 80 ℃ for 6 hours to obtain the cellulose-chitosan microspheres for later use.
And (3) filling the prepared cellulose-chitosan microspheres into a cellulose-chitosan microsphere fixed bed reactor. Under the condition that the temperature is 50 ℃, the feed liquid to be treated with the ionic liquid concentration of 15g/L is introduced into the cellulose-chitosan microsphere fixed bed reactor at the flow rate of 2 times of the bed layer volume, ICP is carried out on the effluent solution, and the removal condition of iron ions and copper ions is determined, wherein the results are shown in Table 1.
Example 4
The ionic liquid in this example is a mixture of 1-ethyl-3-methylimidazolium diethyl phosphate ionic liquid and 1-allyl-3-methylpyridine chloride ionic liquid.
The preparation process of the cellulose-chitosan microsphere in this embodiment is as follows: placing cellulose, chitosan and ionic liquid in a reaction kettle according to the mass ratio of 1:1:30, stirring and dissolving, controlling the reaction temperature to be 90 ℃, after the cellulose and the chitosan are completely dissolved, dropwise adding the dissolved ionic liquid-cellulose-chitosan mixed solution into water, and replacing water every 6 hours until the ionic liquid is completely replaced, thus obtaining cellulose-chitosan microspheres; and (3) drying the prepared cellulose-chitosan microspheres in a drying oven at the temperature of 100 ℃ for 6 hours to obtain the cellulose-chitosan microspheres for later use.
And (3) filling the prepared cellulose-chitosan microspheres into a cellulose-chitosan microsphere fixed bed reactor. Under the condition of the temperature of 25 ℃, the feed liquid to be treated with the ionic liquid concentration of 15g/L is introduced into the cellulose-chitosan microsphere fixed bed reactor at the flow rate of 20 times of the bed layer volume, ICP is carried out on the effluent solution, and the removal conditions of iron ions and copper ions are determined, wherein the results are shown in Table 1.
Example 5
The ionic liquid in this example is 1-ethyl-3-methylimidazolium diethyl phosphate ionic liquid.
The preparation process of the cellulose-chitosan microsphere in this embodiment is as follows: placing cellulose, chitosan and ionic liquid in a reaction kettle according to the mass ratio of 1:1:30, stirring and dissolving, controlling the reaction temperature to be 100 ℃, after the cellulose and the chitosan are completely dissolved, dropwise adding the dissolved ionic liquid-cellulose-chitosan mixed solution into water, and replacing water every 6 hours until the ionic liquid is completely replaced, thus obtaining cellulose-chitosan microspheres; and (3) drying the prepared cellulose-chitosan microspheres in a drying oven at the temperature of 100 ℃ for 6 hours to obtain the cellulose-chitosan microspheres for later use.
And (3) filling the prepared cellulose-chitosan microspheres into a cellulose-chitosan microsphere fixed bed reactor. Under the condition of the temperature of 25 ℃, the feed liquid to be treated with the ionic liquid concentration of 10g/L is introduced into the cellulose-chitosan microsphere fixed bed reactor at the flow rate of 20 times of the bed layer volume, ICP is carried out on the effluent solution, and the removal conditions of iron ions and copper ions are determined, wherein the results are shown in Table 1.
Table 1: the change conditions of iron ions and copper ions before and after the removal of the feed liquid to be treated
| |
Iron (ppm)
|
Copper (ppm)
|
| Before the experiment
|
100
|
100
|
| After the experiment
|
—
|
—
|
| Example 1
|
<0.01
|
<0.01
|
| Example 2
|
<0.01
|
<0.01
|
| Example 3
|
<0.01
|
<0.01
|
| Example 4
|
1.12
|
0.38
|
| Example 5
|
1.16
|
0.37 |