CN101249385B - A method for purifying amphoteric surfactants by electrodialysis desalination - Google Patents

Abstract

The invention discloses a method for purifying amphoteric surfactants by electrodialysis desalination, which belongs to the technical field of membrane separation. The invention utilizes the characteristic that the amphoteric surfactant does not move to the two poles when it is in the range of isoelectric point. After the electrodialysis treatment, the small molecules of the inorganic salt enter the concentrated chamber, and the molecules of the amphoteric surfactant stay in the dilute chamber, thereby separating and removing the inorganic salt. Remove and purify amphoteric surfactants. Suitable amphoteric surfactants have an amino acid or betaine structure or have an imidazoline-type structure. The invention can effectively remove the inorganic salts in the amphoteric surfactants, and the separation process has no phase change, no pollution, low cost and low energy consumption, and solves the limitation of the development of the amphoteric surfactants due to the difficulty in purifying the inorganic salts to a certain extent. problems, and provide an economical and effective way for the separation of inorganic salts in the production of amphoteric surfactants.

Description

A method for purifying amphoteric surfactants by electrodialysis desalination

technical field

The invention discloses a method for purifying amphoteric surfactants by electrodialysis desalination, which belongs to the technical field of membrane separation. Specifically, it is a method in which small inorganic salt molecules in an amphoteric surfactant solution move directionally under the action of an electric field and selectively pass through an ion exchange membrane to separate from the amphoteric surfactant.

Background technique

Amphoteric surfactants have both non-ionizable positive and negative charge centers (or dipole centers) in the same molecule, and have low toxicity and low irritation, good biodegradability, effective bactericidal properties and excellent compatibility. In the process of synthesizing amphoteric surfactants, small inorganic salt molecules are often unavoidably produced, resulting in negative effects such as high product viscosity, unstable pH value, or decreased chemical stability, which affect the excellent performance of amphoteric surfactants. Since the solubility of amphoteric surfactants is very similar to that of inorganic salts, it is very difficult to separate them from inorganic electrolytes. At present, there is no easy, economical and satisfactory separation method to remove small molecules of inorganic salts in amphoteric surfactants.

Electrodialysis desalination technology has been widely used in seawater desalination and sewage treatment processes. It has the advantages of simple operation, no environmental pollution, low cost and easy realization of large-scale operation. Amphoteric surfactants exist as electrically neutral molecules in the form of internal salts at their isoelectric points, and neither move to the anode nor to the cathode in an external electric field. If within the isoelectric point range of the purified amphoteric surfactant, the amphoteric surfactant solution containing inorganic salt impurities is used as the weak room solution, and sodium salt such as sodium chloride or sodium nitrate solution is used as the initial solution of the concentrated room, and the hydrogen oxidized Sodium and sulfuric acid solutions are used as the cathode and anode chamber solutions respectively. Adjust the flow rate and operating voltage of the dilute chamber to carry out electrodialysis, and the anions in the dilute chamber liquid such as Cl ^- migrate to the anode through the negative membrane and enter the concentrated chamber, and are blocked by the positive membrane to stay in the concentrated chamber; the cations in the dilute chamber liquid such as After Na ⁺ migrates to the cathode through the positive membrane, it also enters the concentrated chamber, and is blocked by the negative membrane and is trapped in the concentrated chamber; while the amphoteric surfactant in the form of inner salt does not migrate significantly under the action of an electric field and stays in the weak chamber. chamber to separate and remove inorganic salts and to purify amphoteric surfactants. By controlling the operating conditions such as the pH value of the amphoteric surfactant solution in the dilute chamber, the flow rate of the dilute chamber, and the operating voltage, the amphoteric surfactant can be circulated and desalted in the electrodialyzer. Because amphoteric surfactants have good water solubility and no membrane fouling problem, they can be purified by electrodialysis. At present, there is no research report in this area in China.

Contents of the invention

The purpose of the present invention is aimed at the characteristics of amphoteric surfactants, and proposes a method for purifying amphoteric surfactants by electrodialysis desalination, which can effectively remove inorganic salts in amphoteric surfactants, and has The characteristics of material separation under variable conditions, low cost, no pollution, low energy consumption, to a certain extent, solve the problem of limiting the development of amphoteric surfactants due to the difficulty in the purification of inorganic salts.

Technical scheme of the present invention: a method for purifying amphoteric surfactants by electrodialysis, within the range of the isoelectric point of the purified amphoteric surfactants, amphoteric surfactants containing inorganic salt impurities (mass percentage not exceeding 15%) Surfactant solution (mass percentage content not exceeding 35%) is used as the light room solution, and 0.05mol/L sodium salt such as sodium chloride or sodium nitrate solution 1L is used as the initial solution of the concentrated room, and the concentration is 0.05mol/L. 1L each of sodium hydroxide and sulfuric acid solution was used as the cathode and anode chamber solution respectively. Adjust the flow rate of the dilute chamber to 10L/h to 40L/h. Under the action of a DC electric field with an operating voltage of 8V to 18V, perform electrodialysis for a period of time, and stop dialysis when the conductivity of the dilute chamber liquid no longer decreases.

The purified amphoteric surfactant has an alkylamino acid or betaine structure with the following general formula:

Wherein R ₁ represents an alkyl group having 8 to 22 carbon atoms or an alkylamidopropyl group having 11 to 25 carbon atoms, R ₂ , R ₃ and R ₄ represent the same or different groups each having 1 to 3 carbon atoms The alkyl group, M is carboxyl or sulfo group; when at least one of R ₂ or R ₃ is a hydrogen atom, it is an alkyl amino acid type amphoteric surfactant.

Or the amphoteric surfactant that is purified has imidazoline type structure, has following general formula:

Wherein R ₁ represents an alkyl or alkenyl group with 7 to 21 carbon atoms, R ₂ and R ₃ represent the same or different alkylene groups with 1 to 3 carbon atoms, X represents a hydrogen atom or R ₃ COO ^- group .

Beneficial effects of the present invention:

(1) The present invention can effectively remove the inorganic salts in the amphoteric surfactants, solve the problem that the amphoteric surfactants cover up their excellent performance and limit their development due to the difficulty in the purification of inorganic salts to a certain extent, and are amphoteric surfactants. The separation of inorganic salts in the production of pharmaceuticals provides a cost-effective way.

(2) The purification of amphoteric surfactants by electrodialysis has the advantages of simple operation, no phase change in the separation process, no pollution, low cost, low energy consumption, and easy to realize large-scale operation.

Description of drawings

淡室，口浓室)；3、淡室储槽；4、阴极室储槽；5、阳极室储槽；6、浓室储槽；7、泵；8、流量计。Figure 1 Schematic diagram of the working of the electrodialysis device. Among them: 1, electrode; 2, membrane stack (,

3. Dilute room storage tank; 4. Cathode room storage tank; 5. Anode room storage tank; 6. Concentrated room storage tank; 7. Pump; 8. Flowmeter.

Detailed ways

A specific embodiment of the present invention will be described below with reference to FIG. 1 .

The electrodialyzer used in the present invention is assembled by 50 pairs of anion and cation exchange membranes, the membranes are heterogeneous ion exchange membranes of sulfonic acid type styrene system and quaternary amine type styrene system, and the effective membrane area of a single membrane is 210mm×65mm.

Illustrate by following several groups of embodiments:

The electrodialysis desalination of embodiment 1 α-decyl betaine solution

The pH value of the α-decyl betaine solution containing NaCl was adjusted to 7.5. It is measured that the mass percentages of α-decyl betaine and inorganic salts are 10% and 3% respectively. Put 1L of the above solution into the storage tank of the dilute chamber, use 1L of 0.05mol/L NaCl solution as the initial solution of the concentrated chamber, and use 1L of sodium hydroxide and sulfuric acid solutions with a concentration of 0.05mol/L as the cathode and anode chambers respectively Solution, under the operating conditions of 10V operating voltage and 20L/h flow rate of the dilute chamber, the α-decyl betaine solution is desalted in a cycle. The dialysis ends when the conductivity of the dilute solution no longer decreases. The desalination rate was 97%, and the recovery rate of α-decyl betaine was 82.7%.

Embodiment 2 Electrodialysis desalination of dodecylsulfopropyl betaine solution

Adjust the pH value of the dodecylsulfopropyl betaine solution containing unknown inorganic salt to 7.2. The mass percentages of dodecylsulfopropyl betaine and inorganic salts were measured to be 31% and 13% respectively. Put 0.9L of the above solution plus 0.1L of water into the storage tank of the dilute chamber, use 1L of 0.05mol/L NaCl solution as the initial solution of the concentrated chamber, and use 1L each of sodium hydroxide and sulfuric acid solutions with a concentration of 0.05mol/L As the cathode and anode chamber solutions, the dodecyl sulfopropyl betaine solution is desalted in circulation under the operating conditions of 14V operating voltage and 23L/h dilute chamber flow rate. The dialysis ends when the conductivity of the dilute solution no longer decreases. The desalination rate is 95%, and the recovery rate of dodecyl sulfopropyl betaine is 73.6%.

Embodiment 3 Electrodialysis desalination of lauryl amidopropyl betaine solution

Adjust the pH of the lauryl amidopropyl betaine solution containing unknown inorganic salts to 6.5, and measure the mass percentages of lauryl amidopropyl betaine and inorganic salts to be 5% and 1% respectively. Put 1L of the above solution into the storage tank of the dilute chamber, use 1L of 0.05mol/L _NaNO3 solution as the initial solution of the concentrated chamber, and use 1L of sodium hydroxide and sulfuric acid solutions with a concentration of 0.05mol/L as the cathode and anode respectively. Chamber solution, under the operating conditions of 8V operating voltage and dilute chamber flow rate of 25L/h, the solution is desalted in circulation. The dialysis ends when the conductivity of the dilute solution no longer decreases. The desalination rate was 97%, and the recovery rate of lauryl amidopropyl betaine was 78.2%.

Example 4 Electrodialysis desalination of hexadecanoylaminopropyl sulfopropyl betaine solution

Adjust the pH of the cetylamidopropylsulfopropylbetaine solution containing the unknown inorganic salt to 7.0. It is measured that the mass percentages of cetylamidopropylsulfopropyl betaine and inorganic salt are 17% and 5.5% respectively. Put 1L of the above solution into the storage tank of the dilute chamber, use 1L of 0.05mol/L _NaNO3 solution as the initial solution of the concentrated chamber, and use 1L of sodium hydroxide and sulfuric acid solutions with a concentration of 0.05mol/L as the cathode and anode respectively. Chamber solution, under the operating conditions of 10V operating voltage and 35L/h dilute chamber flow rate, the hexadecanoylaminopropyl sulfopropyl betaine solution is desalted in circulation. The dialysis ends when the conductivity of the dilute solution no longer decreases. The desalination rate was 97%, and the recovery rate of hexadecylamidopropyl sulfopropyl betaine was 85.3%.

Example 5 Electrodialysis desalination of 2-undecyl-N-carboxymethyl-N-(2-hydroxyethyl) imidazoline solution

Adjust the pH value of the 2-undecyl-N-carboxymethyl-N-(2-hydroxyethyl)imidazoline solution containing an unknown inorganic salt to 7.0. The mass percentages of 2-undecyl-N-carboxymethyl-N-(2-hydroxyethyl)imidazoline and inorganic salts were measured to be 31% and 8.0%, respectively. Put 1 L of the above solution into the storage tank of the dilute chamber, use 1 L of 0.05 mol/L NaCl solution as the initial solution of the concentrated chamber, and 1 L of sodium hydroxide and sulfuric acid solutions with a concentration of 0.05 mol/L as the cathode and anode chamber solutions respectively , under the operating conditions of 18V operating voltage and 25L/h dilute chamber flow rate, the 2-undecyl-N-carboxymethyl-N-(2-hydroxyethyl) imidazoline solution was desalted in circulation. The dialysis ends when the conductivity of the dilute solution no longer decreases. The desalination rate was 95%, and the recovery rate of 2-undecyl-N-carboxymethyl-N-(2-hydroxyethyl)imidazoline was 76.4%.

Example 6 Electrodialysis desalination of N-dodecyl-β-alanine sodium solution

Adjust the pH of the sodium N-dodecyl-β-alanine solution containing the unknown inorganic salt to 7.0. The mass percentages of N-dodecyl-β-alanine sodium and inorganic salts were measured to be 30% and 5.6% respectively. Put 1L of the above solution into the storage tank of the dilute chamber, use 1L of 0.05mol/L _NaNO3 solution as the initial solution of the concentrated chamber, and 1L each of sodium hydroxide and sulfuric acid solutions with a concentration of 0.05mol/L as the cathode and anode chambers respectively solution, under the operating conditions of 18V operating voltage and 20L/h dilute chamber flow rate, the N-dodecyl-β-alanine sodium solution is desalted in circulation. The dialysis ends when the conductivity of the dilute solution no longer decreases. The desalination rate was 95%, and the recovery rate of sodium N-dodecyl-β-alanine was 76.4%.

Claims (4)

1. method with electrodialysis desalination purifying ampholytic surfactant, it is characterized in that in purified amphoteric surfactant isoelectric point scope, the amphoteric surfactant solution that will contain inorganic salts impurity is as light chamber liquid, the quality percentage composition of inorganic salts is no more than 15% in the liquid of light chamber, the quality percentage composition of surfactant is no more than 35%, with the sodium salt solution 1L of 0.05mol/L as dense chamber initial soln, concentration is the NaOH of 0.05mol/L and each 1L of sulfuric acid solution respectively as cloudy, anode chamber's solution, regulating light chamber flow is 10L/h～40L/h, be to carry out electrodialysis desalination under the DC electric field effect of 8V～18V at operating voltage, dialysis finished when the electrical conductivity for the treatment of light chamber liquid no longer reduced.

2. according to the method for the described electrodialysis desalination purifying ampholytic of claim 1 surfactant, it is characterized in that the used sodium salt solution in dense chamber is sodium chloride or sodium nitrate.

3. the application of the described electrodialysis desalination purifying ampholytic of claim 1 surface-active agent method is characterized in that the amphoteric surfactant that is purified has betaine structure, has following general formula:

R wherein ₁Representative has the alkyl of 8～22 carbon atoms or the alkylamide propyl of 11～25 carbon atoms, R ₂, R ₃And R ₄Represent identical or different each to have the alkyl of 1～3 carbon atom, M is carboxyl or sulfo group.

4. the application of the described electrodialysis desalination purifying ampholytic of claim 1 surface-active agent method is characterized in that the amphoteric surfactant that this process is fit to be purified equally has the imidazoline type structure, has following general formula:

R wherein ₁Represent the alkyl or alkenyl of 7～21 carbon atoms, R ₂And R ₃Represent the identical or different alkylidene with 1～3 carbon atom, X represents hydrogen atom or R ₃COO ^-Group.

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