CN115465925A - Polyvinyl alcohol-based gel composite membrane electrode and preparation method thereof - Google Patents
Polyvinyl alcohol-based gel composite membrane electrode and preparation method thereof Download PDFInfo
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- 239000004372 Polyvinyl alcohol Substances 0.000 title claims abstract description 52
- 229920002451 polyvinyl alcohol Polymers 0.000 title claims abstract description 52
- 239000002131 composite material Substances 0.000 title claims abstract description 41
- 239000012528 membrane Substances 0.000 title claims abstract description 36
- 238000002360 preparation method Methods 0.000 title claims abstract description 9
- 238000005342 ion exchange Methods 0.000 claims abstract description 34
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 31
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 24
- 238000002242 deionisation method Methods 0.000 claims abstract description 21
- 239000010410 layer Substances 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims abstract description 18
- 229920001467 poly(styrenesulfonates) Polymers 0.000 claims abstract description 18
- SXRSQZLOMIGNAQ-UHFFFAOYSA-N Glutaraldehyde Chemical compound O=CCCCC=O SXRSQZLOMIGNAQ-UHFFFAOYSA-N 0.000 claims abstract description 13
- 238000001179 sorption measurement Methods 0.000 claims abstract description 13
- 238000005516 engineering process Methods 0.000 claims abstract description 12
- 229940006186 sodium polystyrene sulfonate Drugs 0.000 claims abstract description 12
- 239000002344 surface layer Substances 0.000 claims abstract description 8
- 239000003153 chemical reaction reagent Substances 0.000 claims abstract description 5
- 239000003431 cross linking reagent Substances 0.000 claims abstract description 4
- 239000011159 matrix material Substances 0.000 claims abstract description 4
- 239000000758 substrate Substances 0.000 claims abstract description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 33
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 16
- 239000002243 precursor Substances 0.000 claims description 16
- 238000004132 cross linking Methods 0.000 claims description 13
- 239000002033 PVDF binder Substances 0.000 claims description 10
- 239000008367 deionised water Substances 0.000 claims description 10
- 229910021641 deionized water Inorganic materials 0.000 claims description 10
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 10
- 238000003756 stirring Methods 0.000 claims description 10
- 238000000576 coating method Methods 0.000 claims description 9
- 239000011248 coating agent Substances 0.000 claims description 8
- 238000001816 cooling Methods 0.000 claims description 5
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 4
- 239000011267 electrode slurry Substances 0.000 claims description 3
- 239000003014 ion exchange membrane Substances 0.000 abstract description 11
- 239000000243 solution Substances 0.000 description 40
- 239000000499 gel Substances 0.000 description 32
- 208000021343 peeling skin syndrome 5 Diseases 0.000 description 24
- 238000012360 testing method Methods 0.000 description 24
- 238000002484 cyclic voltammetry Methods 0.000 description 15
- 108010025899 gelatin film Proteins 0.000 description 15
- 238000010612 desalination reaction Methods 0.000 description 14
- 230000008569 process Effects 0.000 description 13
- 230000008859 change Effects 0.000 description 10
- 238000011033 desalting Methods 0.000 description 10
- 239000007864 aqueous solution Substances 0.000 description 9
- 238000007599 discharging Methods 0.000 description 8
- 150000002500 ions Chemical class 0.000 description 8
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 7
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 6
- 229960002796 polystyrene sulfonate Drugs 0.000 description 6
- 239000011970 polystyrene sulfonate Substances 0.000 description 6
- 230000008929 regeneration Effects 0.000 description 6
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- 238000009792 diffusion process Methods 0.000 description 4
- 230000007774 longterm Effects 0.000 description 4
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- 238000002479 acid--base titration Methods 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 230000018109 developmental process Effects 0.000 description 3
- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical class Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 3
- 125000000524 functional group Chemical group 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- 230000002572 peristaltic effect Effects 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 239000011734 sodium Substances 0.000 description 3
- 239000011780 sodium chloride Substances 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
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- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000006136 alcoholysis reaction Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
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- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
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- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- 229920000867 polyelectrolyte Polymers 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
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- 238000000746 purification Methods 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
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- -1 salt ions Chemical class 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
- C02F1/4691—Capacitive deionisation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
- B01J13/0052—Preparation of gels
- B01J13/0065—Preparation of gels containing an organic phase
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
- C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
- C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2425/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Derivatives of such polymers
- C08J2425/18—Homopolymers or copolymers of aromatic monomers containing elements other than carbon and hydrogen
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/04—Oxygen-containing compounds
- C08K5/07—Aldehydes; Ketones
Abstract
The invention relates to a gel composite membrane electrode based on polyvinyl alcohol and a preparation method thereof, wherein the composite membrane electrode is of a multilayer composite structure which takes a carbon electrode as an adsorption substrate layer and a composite gel layer as an ion exchange surface layer, the composite gel layer takes the polyvinyl alcohol as a matrix, takes sodium polystyrene sulfonate as an ion exchange reagent and takes glutaraldehyde as a cross-linking agent. Compared with the traditional membrane capacitance deionization technology, the invention does not need to additionally add an ion exchange membrane, can reduce the contact resistance between the carbon electrode and the ion exchange membrane, improves the affinity between the membrane and the electrode, avoids leakage, and provides a new idea and method for developing the membrane capacitance deionization electrode with good circulation stability and higher charge efficiency.
Description
Technical Field
The invention relates to the technical field of capacitive deionization, in particular to a polyvinyl alcohol ion exchange gel membrane composite electrode for capacitive deionization technology and a preparation method thereof.
Background
The Capacitive deionization technology is a novel clean, energy-saving, and chemical-addition-free Capacitive Desalination (CDI). The principle is that external voltage is applied to electrodes, and salt ions in aqueous solution are adsorbed by utilizing the electrostatic action, so that desalination is realized. The regeneration of the electrode is completed in situ through the discharge of the electrode, no secondary pollution is caused, the energy-saving performance is remarkable, the service life of the capacitor material is long, and the capacitor material is anti-scaling. The advantages are obvious compared with other desalination technologies. However, the low charge efficiency and salt adsorption capacity caused by the co-ion effect limit the further development of CDI. The membrane capacitive deionization is an enhancement process of a capacitive desalination technology, and is characterized in that an ion exchange membrane is introduced on the surface of an electrode in a CDI (capacitance-capacitance deionization) assembly, and when a solution flows through a flow channel of an MCDI (micro-coupled ion detector) assembly, ions in the solution penetrate through the ion exchange membrane and then diffuse to the surface of the electrode, and then are adsorbed on the electrode. Due to the use of the ion exchange membrane, the occurrence of Faraday side reaction is effectively avoided, and the circulation stability of the electrode is improved. Finally, because of no interference of the same ions, the regeneration efficiency of the electrode is improved, and the service life of the membrane electrode is effectively prolonged.
However, MCDI requires a strong physical pressure to ensure intimate contact of the membrane with the surface of the CDI electrode material. This results in an increase in the interfacial resistance and diffusion layer resistance of the film, a decrease in ion mobility, and further affects overall performance.
Disclosure of Invention
The invention provides a gel composite membrane electrode based on polyvinyl alcohol and a preparation method thereof, and aims to solve the problems that the interface resistance and the diffusion layer resistance of a membrane in MCDI are increased, the ionic mobility is reduced, and the overall performance is further influenced.
In order to solve the above technical problem, the embodiments of the present invention provide the following technical solutions:
the composite membrane electrode is a multilayer composite structure which takes a carbon electrode as an adsorption substrate layer and a composite gel layer as an ion exchange surface layer, wherein the composite gel layer takes polyvinyl alcohol as a matrix, sodium polystyrene sulfonate as an ion exchange reagent and glutaraldehyde as a cross-linking agent.
A preparation method of a gel composite membrane electrode based on polyvinyl alcohol comprises the following preparation steps:
(1) Dissolving polyvinyl alcohol in deionized water, stirring uniformly at 90 +/-2 ℃, and naturally cooling to room temperature to obtain 5-7% polyvinyl alcohol solution;
(2) Slowly adding sodium polystyrene sulfonate into a polyvinyl alcohol solution, wherein the concentration ratio of the sodium polystyrene sulfonate to polyvinyl alcohol is 5-15;
(3) Adjusting the precursor solution to acidity, adding 10% glutaraldehyde for crosslinking to prepare gel surface solution;
(4) And uniformly coating the gel surface solution on the surface of the carbon electrode to form a composite gel layer, standing and crosslinking for 1h at room temperature to prepare the ion exchange gel membrane composite electrode.
Preferably, the carbon electrode is prepared by uniformly coating electrode slurry prepared from activated carbon, PVDF and conductive carbon black according to the mass ratio of 8.
Preferably, the concentration ratio of the sodium polystyrene sulfonate to the polyvinyl alcohol in the step (2) is 15-7.
Preferably, hydrochloric acid is used to adjust the precursor solution to a pH of 2.50 ± 0.05 in step (3).
Compared with the prior art, the invention has the beneficial effects that:
the invention uses chemical cross-linking and coating method to prepare an ion exchange gel membrane composite electrode used in capacitance deionization technology. The polyvinyl alcohol is used as a hydrophilic binder, the affinity of the electrode and water is strong, and charged ions easily enter the pore canal of the electrode material through an interface, so that the adsorption capacity is improved; the composite membrane can not only block the permeation of dissolved oxygen, thereby reducing the degradation of the carbon electrode and solving the problem of diffusion resistance increase caused by adding a membrane additionally in MCDI; the gel membrane prevents the permeation of the co-ions, and improves the desalination efficiency of the electrode in the adsorption process.
Compared with the traditional membrane capacitance deionization technology, the invention does not need to additionally add an ion exchange membrane, can reduce the contact resistance between the carbon electrode and the ion exchange membrane, improves the affinity between the membrane and the electrode, simultaneously avoids leakage, and provides a new idea and a new method for developing the membrane capacitance deionization electrode with good circulation stability and higher charge efficiency.
Drawings
FIG. 1 is an optical photograph showing the PVA gel film composite electrode appearance;
FIG. 2 is a scanning electron microscope image of the cross section of the PVA gel film composite electrode;
FIG. 3 is a picture of the real-time effluent concentration change curve obtained by the regeneration of the PVA5-PSS5/10/15 electrode of example 1 after the complete charging and discharging process;
FIG. 4 is a picture of the real-time charging current variation curve obtained by regenerating the PVA5-PSS5/10/15 electrode of example 1 after such a complete charging and discharging process;
FIG. 5 is a cyclic voltammetry test for PVA5-PSS5/10/15 electrodes of example 1;
FIG. 6 is a cyclic voltammetry test after 50 cycles of the PVA5-PSS15 electrode of example 1;
FIG. 7 is a graph showing that the PVA6-PSS5/10/15 electrode of example 2 is regenerated after such a complete charging and discharging process, and a real-time effluent concentration change curve is obtained;
FIG. 8 is a picture of the real-time charging current variation curve obtained by the regeneration of the PVA6-PSS5/10/15 electrode of example 2 after such a complete charging and discharging process;
FIG. 9 is the cyclic voltammetry tests for PVA6-PSS5/10/15 electrodes of example 2;
FIG. 10 is a cyclic voltammetry test after 50 cycles of the PVA6-PSS15 electrode of example 2;
FIG. 11 is a picture of the real-time effluent concentration change curve obtained by the regeneration of the PVA7-PSS5/10/15 electrode of example 3 after such a complete charging and discharging process;
FIG. 12 is a picture of the real-time charging current variation curve obtained by the regeneration of the PVA7-PSS5/10/15 electrode of example 3 after such a complete charging and discharging process;
FIG. 13 shows the cyclic voltammetry tests for PVA7-PSS5/10/15 electrodes of example 3;
FIG. 14 is a cyclic voltammetry test after 50 cycles of the PVA7-PSS15 electrode of example 3.
Detailed Description
The following examples are further illustrative of the present invention and are not intended to limit the scope of the present invention.
In order to improve charge efficiency and adsorption capacity, polyanion is added into cross-linked polymer gel and coated on the surface of a carbon electrode, and a gel membrane composite electrode with an ion exchange surface layer is developed. The electrode performance is improved by improving the electrode gel membrane formula and the forming condition, so that the electrode is more stable and efficient in the capacitive deionization and desalination process, and the development of the capacitive deionization technology is promoted.
Polyvinyl alcohol (PVA) is a relatively cheap polymer material, and has the advantages of good biocompatibility, strong film forming capability and good hydrophilicity. As a polymer matrix of an ion exchange membrane, its mechanical properties and thermal stability can be improved by freezing, heat treatment, irradiation and chemical crosslinking.
In order to improve charge efficiency and adsorption capacity, polyanion is added into cross-linked polymer gel and coated on the surface of a carbon electrode, and a gel membrane composite electrode with an ion exchange surface layer is developed. The electrode performance is improved by improving the electrode gel membrane formula and the forming condition, so that the electrode is more stable and efficient in the capacitive deionization and desalination process, and the development of the capacitive deionization technology is promoted.
The invention takes polyvinyl alcohol (PVA) as a substrate, adds polyelectrolyte sodium polystyrene sulfonate (PSS), takes Glutaraldehyde (GA) as a cross-linking agent to prepare gel with ion exchange characteristics, and takes composite gel as an ion exchange surface layer to coat the ion exchange surface layer on the surface of a carbon electrode to prepare the composite electrode with the ion exchange surface layer. So as to improve the charge efficiency and hydrophilicity of the electrode, inhibit Faraday reaction, and reduce the diffusion resistance caused by additional MCDI film.
The PVA in the examples of the present invention is a commercially available product from Shanghai Allandin reagent, inc., and the alcoholysis degree is 98.0 to 99.0 mol% solids. Wherein, PVA is polyvinyl alcohol.
PSS in the examples of the present invention is sodium polystyrene sulfonate ((C) commercially available from Sigma reagent Ltd 8 H 7 NaO 3 S)n）。
Glutaraldehyde (GA) in the examples of the invention is a commercial product from Meclin, 50wt%.
The activated carbon in the embodiment of the invention is a commercial product of Fuzhou Yihuan carbon Co., ltd, and the specific surface area is 2000-2500m 2 D50 is 8 to 20 < 13211 >, and the formula is shown in the specification.
The conductive carbon black in the examples of the present invention is commercially available from Cabot corporation, USA, and the particle size is 40nm.
The polyvinylidene fluoride (PVDF) in the examples of the invention is a commercially available powder solid from alcoma, france.
Example 1
10g of polyvinyl alcohol is dissolved in 100ml of deionized water, mechanically stirred for 5 hours at 90 +/-2 ℃, and after complete dissolution, the stirring is stopped. And (4) standing at normal temperature and cooling to room temperature (25 ℃) to obtain 10% PVA aqueous solution for later use. Taking a certain amount of PVA aqueous solution, adding water to dilute the PVA aqueous solution to 5%, adding PSS (the mass fraction of the PSS is 5%, 10% and 15% (relative to PVA) (when the concentration of sodium polystyrene sulfonate is more than 15%, the solution is too sticky and silk causes poor gel appearance), magnetically stirring the solution for 30 min to prepare a precursor solution, adjusting the pH of the precursor solution to 2.50 +/-0.05 by using 1.0M hydrochloric acid, taking the solution to stand at room temperature, taking 8mL of the solution after defoaming, putting the solution into a small beaker, and respectively adding 800 microliter of glutaraldehyde to carry out crosslinking to form a compact crosslinking reticular system, wherein the crosslinking reaction of less than 10% of glutaraldehyde is incomplete, and free sulfonic groups are not reacted, so that a gel film cannot be formed; above this concentration the crosslinked network is denser, resulting in poor gel film performance. And ultrasonically oscillating for 1 min to obtain gel film solution. And uniformly coating the film-forming solution on the surface of the carbon electrode by using an I-shaped scraper with the thickness of 750 mm, standing and crosslinking for 1h at room temperature to prepare a gel film composite electrode, namely a PVA5-PSS5/10/15 electrode. Fig. 1 shows the molding state of the gel electrode, and the gel electrode after cross-linking is put into deionized water for soaking for standby.
The carbon electrode is prepared by uniformly coating electrode slurry prepared from activated carbon, PVDF and conductive carbon black according to the mass ratio of 8.
The morphology of example 1 was observed using a scanning electron microscope, as shown in fig. 2. The surface of the gel film electrode is smooth, the electrode is divided into two layers in a cross section diagram, the upper layer is a smooth and compact gel layer, the lower layer is a carbon electrode layer, and the gel layer and the carbon electrode layer are tightly compounded together. Since the interface of the gel film composite electrode has a staggered boundary, it is advantageous to reduce the contact resistance.
The desalination performance test is mainly realized by a CDI module, which is disclosed in the paper of Continuous circulation of carbon-based purification systems of the electrode performance and stability published in the subject group, and consists of a capacitive deionization module, a peristaltic pump, a potentiostat and a conductivity meter. The capacitive deionization module consists of a pair of parallel electrodes, a silica gel sheet with the thickness of 2 mm is placed between the two electrodes to keep a gap between the two electrodes, and the silica gel has elasticity, can be in better contact with the electrodes, and has certain sealing property. Two ends of the module are fixed by two organic glass partition plates and used for supporting the electrodes, the lower end of the module is provided with a water inlet, the upper end of the module is provided with a water outlet, and the water outlet and the water inlet are consistent with the titanium plate. The capacitive deionization module is an electro-adsorption desalting main working area of the whole CDI system; the peristaltic pump provides a stable water inlet flow rate for the whole CDI system; the constant potential rectifier provides 1.2V constant working voltage for the CDI system; and the conductivity meter monitors the change of the NaCl solution at the water outlet of the capacitive deionization module in real time.
The operation mode of one complete desalination-salt discharge cycle period of the CDI desalination test apparatus is as follows: after the equipment is connected, a peristaltic pump is started, naCl solution with the concentration of 250ppm is introduced into the CDI module, a constant voltage power supply is started after the effluent concentration is stable (electrode physical adsorption is saturated), the power supply voltage is 1.2V, and the CDI module starts to remove salt. And after the outlet water concentration is reduced and then is increased to the inlet water conductivity concentration, the power supply is closed, the CDI module starts backwashing, and after the outlet water conductivity is increased and then is reduced until the outlet water conductivity is equal to the inlet water conductivity, the backwashing is finished. The whole process is defined as a complete cycle of desalination and salt discharge. The PVA5-PSS5/10/15 electrode can be regenerated after the complete charging and discharging process, and real-time effluent concentration change and charging current change curves are obtained, as shown in figures 3 and 4. The desalting amount of CDI gradually becomes stable after five cycles, and the final electrode desalting amount is divided into 13.94 mg/g, 17.47 mg/g and 13.41mg/g. The charge efficiency of the desalting test gradually stabilized after five cycles, and the final electrode charge efficiency was divided into 52.60, 65.51 and 53.13%. The performance of example 1 is significantly improved compared to the original PVDF carbon electrode. This indicates that negatively charged groups on the gel film accelerate Na in water + The adsorption of ions substantially improves the charge efficiency.
In the voltage interval of-0.8 to 0.8V and the scanning speed of 0.005v/s, the cyclic voltammetry test was carried out on the sample 1 by using an electrochemical workstation of the model CHI660E, as shown in FIG. 5. And (3) testing conditions: the scanning speed is 0.005v/s, the NaCl solution concentration is 1M, the scanning voltage range is-0.8V to 0.8V, the test environment is a constant-temperature water bath at 20 ℃, the test system is a three-electrode system, wherein the working electrode is the electrode (1 multiplied by 1 cm) of example 1 2 ) The counter electrode is a platinum electrode (2X 2 cm) 2 ) And the auxiliary electrode is a saturated calomel electrode. The CV curve after 50 cycles still exhibits a rectangular-like shape, and no significant redox reaction occurs. According to the formula: f/g (= integral (i)) a -i b )/(2×△v×V×Y electrode ) Wherein F/g is specific capacitance, i a Is the current charged during the positive scan, i b Is the current of discharge in the negative sweep process, with unit A; y is electrode Is the mass of the electrode in g; v is the scanning speed (V/s); deltav is a scanning voltage interval, and the specific capacitance of the electrode cyclic voltammetry test in the example 1 is calculated to be 93.01, 101.28 and 113.55F/g respectively. To examine the long-term cyclic stability of the electrodes, cyclic voltammetry tests after 50 cycles of the relatively optimal PVA5-PSS15 electrodes are shown in FIG. 6. Through calculation of the specific capacitance of 112.73F/g, the electrode capacitance is only slightly lost after 50 cycles, which shows that the PVA5-PSS15 gel composite membrane electrode shows excellent long-term cycling stability and higher capacitance capacity in electrochemical performance.
The ion exchange capacity of example 1 was tested using acid-base titration. The gel was formed into a cylinder having a diameter of 15 mm and a thickness of about 5mm, and the gel was immersed in 1 mol/L hydrochloric acid, and the hydrochloric acid solution was changed every 8 hours. After the solution was sufficiently equilibrated, the hydrochloric acid adhered to the surface was removed by washing with pure water. Soaking the gel in 0.5 mol/L sodium chloride solution for sufficient balance, and adding H in the gel + And (4) completely exchanging. Finally, titrating the amount of hydrogen ions exchanged by sodium ions by using 0.1M NaOH solution, and according to a formula:
the Ion Exchange Capacity (IEC) of the PVA5-PSS5/10/15 electrode was calculated to be 1.05, 1.11, 1.19mmol/g, respectively. The ion exchange capacity of the ion exchange membrane is an important factor affecting the performance of MCDI devices. The ion exchange capacity is determined by the number of active sites or the number of functional groups having ion exchange capacity.
Example 2
Reference is made to example 1 with the following differences: the initial concentration of polyvinyl alcohol was 6%.
Respectively weighing the required deionized water and polyvinyl alcohol, adding the deionized water and the polyvinyl alcohol into a 500 mL three-neck flask according to the sequence of firstly adding water and then adding a polymer, mechanically stirring for 5 hours at a constant temperature of 90 ℃, and stopping stirring after the deionized water and the polyvinyl alcohol are completely dissolved. And standing at normal temperature and cooling to room temperature to obtain 10% PVA water solution for later use. Taking a certain amount of PVA aqueous solution, adding water to dilute the PVA aqueous solution to 6%, adding PSS with mass fractions of 5%, 10% and 15% (relative to PVA), magnetically stirring for 30 min to prepare a precursor solution, adjusting the pH of the precursor solution to 2.50 +/-0.05 by using 1.0M hydrochloric acid, taking the precursor solution to stand at room temperature, taking 8mL of the precursor solution after defoaming, putting the precursor solution into a small beaker, respectively adding 800 mu L of glutaraldehyde for crosslinking, and ultrasonically oscillating for 1 min to prepare a gel film solution. And uniformly coating the film-forming solution on the surface of a PVDF carbon electrode by using an I-shaped scraper with the thickness of 750 mm, standing and crosslinking for 1h at room temperature to prepare a gel film composite electrode, namely a PVA6-PSS5/10/15 electrode.
The desalting performance test was mainly performed by the CDI module, as in example 1. The operation mode of a complete desalination-salt discharge cycle period of the CDI desalination test apparatus is the same as that of the example 1, and the pva6-PSS5/10/15 electrode is regenerated after such a complete charging and discharging process, so as to obtain real-time effluent concentration change and charging current change curves, as shown in fig. 7 and 8. The desalting amount of CDI gradually becomes stable after five cycles, and the final electrode desalting amount of the PVA6-PSS5/10/15 electrode is divided into 12.55, 10.57 and 18.70mg/g. The charge efficiency of the desalting test gradually becomes stable after five cycles, and the final electrode charge efficiency of the PVA6-PSS5/10/15 electrode is divided into 51.10, 49.27 and 73.02 percent. The performance of the electrode is obviously improved compared with the original PVDF carbon electrode in the embodiment 2. This indicates that negatively charged groups on the gel film accelerate Na in water + The adsorption of ions substantially improves the charge efficiency.
In a voltage interval of-0.8 to 0.8V and at a scanning speed of 0.005v/s, cyclic voltammetry was performed on the sample 2 by using an electrochemical workstation of the type CHI660E, as shown in FIG. 9. The test conditions were the same as in example 1. Wherein the working electrode was the electrode of example 2 (1X 1 cm) 2 ) The counter electrode is a platinum electrode (2X 2 cm) 2 ) And the auxiliary electrode is a saturated calomel electrode. The specific capacitances of the cyclic voltammetry tests of the PVA6-PSS5/10/15 electrodes in example 2 were calculated to be 93.13, 100.12 and 107.96F/g, respectively. The cyclic voltammetry test of the PVA6-PSS15 electrode after 50 cycles is shown in FIG. 10, and the calculation of the specific capacitance of 106.52F/g shows that only slight loss of the electrode capacitance occurs after 50 cycles, which indicates that the PVA6-PSS15 gel composite membrane electrode shows excellent long-term electrochemical performanceCycle stability and higher capacitance capacity.
The ion exchange capacity of example 2 was tested by acid-base titration as in example 1. The Ion Exchange Capacities (IEC) of the PVA6-PSS5/10/15 electrodes of example 2 were calculated to be 1.23, 1.28 and 1.43mmol/g, respectively. The ion exchange capacity of the ion exchange membrane is an important factor affecting the performance of MCDI devices. The ion exchange capacity is determined by the number of active sites or the number of functional groups having ion exchange capacity.
Example 3
Referring to example 1, except that: the initial concentration of polyvinyl alcohol was 7%.
Respectively weighing the required deionized water and polyvinyl alcohol, adding the deionized water and the polyvinyl alcohol into a 500 mL three-neck flask according to the sequence of water firstly and polymer secondly, mechanically stirring the mixture for 5 hours at the constant temperature of 90 ℃, and stopping stirring after the deionized water and the polyvinyl alcohol are completely dissolved. And standing at normal temperature, and cooling to room temperature to obtain 10% PVA aqueous solution for later use. Taking a certain amount of PVA aqueous solution, adding water to dilute the PVA aqueous solution to 7%, adding PSS with the mass fractions of 5%, 10% and 15% (relative to PVA), magnetically stirring for 30 min to prepare a precursor solution, adjusting the pH of the precursor solution to 2.50 +/-0.05 by using 1.0M hydrochloric acid, taking the precursor solution to stand at room temperature, taking 8mL of the precursor solution after defoaming, putting the precursor solution into a small beaker, respectively adding 800 mu L of glutaraldehyde for crosslinking, and ultrasonically oscillating for 1 min to prepare a gel film solution. And uniformly coating the film-forming solution on the surface of a PVDF carbon electrode by using an I-shaped scraper with the thickness of 750 mm, standing and crosslinking for 1h at room temperature to prepare a gel film composite electrode, namely a PVA7-PSS5/10/15 electrode.
The desalting performance test was mainly performed by the CDI module, as in example 1. The operation mode of a complete desalination-salt discharge cycle period of the CDI desalination test apparatus is the same as that of example 1, and the PVA7-PSS5/10/15 electrode is regenerated after such a complete charge-discharge process, so as to obtain real-time effluent concentration change and charge current change curves, as shown in fig. 11 and 12. The desalination amount of CDI gradually becomes stable after five cycles, and the final electrode desalination amount of the PVA7-PSS5/10/15 electrode is divided into 11.63, 12.83 and 15.30mg/g. The charge efficiency of the desalting test gradually becomes stable after five cycles, and the final electrode charge efficiency of the PVA7-PSS5/10/15 electrode is divided into 53.36, 56.61 and 64.60 percent. And the originalThe PVDF carbon electrode has significantly improved performance over comparative example 3. This indicates that negatively charged groups on the gel film accelerate Na in water + The adsorption of ions substantially improves the charge efficiency.
In a voltage interval of-0.8 to 0.8V and at a scanning speed of 0.005v/s, cyclic voltammetry was performed on the sample 3 by using an electrochemical workstation of the type CHI660E, as shown in FIG. 13. The test conditions were the same as in example 1. Wherein the working electrode was the electrode of example 7 (1X 1 cm) 2 ) The counter electrode is a platinum electrode (2X 2 cm) 2 ) And the auxiliary electrode is a saturated calomel electrode. The specific capacitances of the cyclic voltammetry tests of the PVA7-PSS5/10/15 electrodes of example 3 were calculated to be 101.34, 104.8 and 101.49F/g, respectively. The cyclic voltammetry test of the PVA7-PSS15 electrode after 50 cycles is shown in FIG. 14, and the specific capacitance is calculated to be 96.48F/g, so that the electrode capacitance is slightly lost after 50 cycles, and the PVA7-PSS15 gel composite membrane electrode shows excellent long-term cyclic stability and higher capacitance capacity in electrochemical performance.
The ion exchange capacity of example 3 was tested by acid-base titration as in example 1. The Ion Exchange Capacities (IEC) of the PVA7-PSS5/10/15 electrodes of example 3 were calculated to be 1.80, 1.96 and 1.97mmol/g, respectively. The ion exchange capacity of the ion exchange membrane is an important factor affecting the performance of MCDI devices. The ion exchange capacity is determined by the number of active sites or the number of functional groups having ion exchange capacity.
It should be understood by those skilled in the art that the foregoing is only illustrative of several embodiments of the invention, and not of all embodiments. It should be noted that many variations and modifications are possible to those skilled in the art, and all variations and modifications that do not depart from the gist of the invention are intended to be within the scope of the invention as defined in the appended claims.
Claims (5)
1. The gel composite membrane electrode based on polyvinyl alcohol is characterized by being of a multi-layer composite structure with a carbon electrode as an adsorption substrate layer and a composite gel layer as an ion exchange surface layer, wherein the composite gel layer takes polyvinyl alcohol as a matrix, sodium polystyrene sulfonate as an ion exchange reagent and glutaraldehyde as a cross-linking agent.
2. The preparation method of the polyvinyl alcohol-based gel composite membrane electrode according to claim 1, characterized in that the preparation steps are as follows:
(1) Dissolving polyvinyl alcohol in deionized water, stirring uniformly at 90 +/-2 ℃, and naturally cooling to room temperature to obtain 5-7% polyvinyl alcohol solution;
(2) Slowly adding sodium polystyrene sulfonate into a polyvinyl alcohol solution, wherein the concentration ratio of the sodium polystyrene sulfonate to the polyvinyl alcohol is 5-15;
(3) Adjusting the precursor solution to acidity, adding 10% glutaraldehyde for crosslinking to prepare gel surface solution;
(4) And uniformly coating the gel surface solution on the surface of the carbon electrode to form a composite gel layer, standing and crosslinking for 1h at room temperature to prepare the ion exchange gel membrane composite electrode.
3. The method for preparing the ion exchange gel membrane composite electrode for the capacitive deionization technology according to claim 2, wherein the carbon electrode is prepared by uniformly coating electrode slurry prepared from activated carbon, PVDF and conductive carbon black according to a mass ratio of 8.
4. The method for preparing the ion exchange gel membrane composite electrode for the capacitive deionization technology as claimed in claim 2, wherein the concentration ratio of sodium polystyrene sulfonate to polyvinyl alcohol in step (2) is 15.
5. The method for preparing the ion exchange gel membrane composite electrode for capacitive deionization technology as claimed in claim 2, wherein the pH of the precursor solution in step (3) is adjusted to 2.50 ± 0.05 using hydrochloric acid.
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Inventor after: Geng Long Inventor after: Guan Yinyan Inventor after: Zhang Shiyue Inventor after: Gao Weichun Inventor after: Tian Xueyong Inventor after: Liang Jiyan Inventor before: Geng Long Inventor before: Guan Yinyan Inventor before: Zhang Shiyue Inventor before: Gao Weichun Inventor before: Tian Xueyong Inventor before: Liang Jiyan |