CN114890513A - Multi-channel capacitive desalting device constructed by copper ion redox electrolyte and desalting method - Google Patents
Multi-channel capacitive desalting device constructed by copper ion redox electrolyte and desalting method Download PDFInfo
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- 238000011033 desalting Methods 0.000 title claims abstract description 65
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- 238000000034 method Methods 0.000 title claims abstract description 32
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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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
Abstract
The invention discloses a multi-channel capacitive desalting device constructed by copper ion redox electrolyte, wherein the anode of the desalting device is a functional activated carbon anode, the functional activated carbon anode comprises an activated carbon electrode, an anion exchange membrane and sodium chloride and copper chloride active electrolyte solution which are added into a first channel formed between the activated carbon electrode and the anion exchange membrane, a desalting channel is formed between the anion exchange membrane and a cathode, and NaCl solution to be treated is desalted through the desalting channel. The invention provides Cu by using a copper chloride solution 2+ /Cu + The electricity pair utilizes the change of the ionic valence state caused by oxidation and reduction reactions in the charge and discharge processes of the positive electrode and the negative electrode to achieve the effect of additional adsorption and desorption of the positive ions and the negative ions on two sides of the electrodes, the ion adsorption capacity of the device is improved, the adsorption energy consumption is reduced, the cycle stability is improved, and the multi-channel capacitance deionization technology constructed by the copper ion redox electrolyte has better economic, environmental and social benefits in the aspects of energy conservation, environmental protection and sustainable development.
Description
Technical Field
The invention relates to the technical field of capacitive deionization desalination, wastewater treatment and resource recovery, in particular to a multi-channel capacitive desalination device constructed by copper ion redox electrolyte and a desalination method.
Background
Fresh water resources are an important guarantee for socio-economic development, and with the increase of the population in the world and the ubiquitous water environment pollution, more than 25 hundred million people experience serious water shortage for at least one month every year, and sustainable supply of fresh water resources will be one of the most important problems related to human development. 95% of water resources on earth belong to seawater resources, and desalination of seawater is a feasible method for producing fresh water. The basic principle of Capacitive deionization (Capacitive deionization) is that ions in water are subjected to directional migration for balancing potential difference of two electrodes and are adsorbed on the surfaces of electrodes to form an electric double layer capacitor, and charged particles in water are removed in the processes of ion transmission in a solution and charge transfer between the electrodes, so that the aim of desalination or purification is fulfilled. In recent 50 years, with the innovation and development of materials and structures of a capacitive deionization technology, the operability of the technology for desalting high-concentration seawater is greatly improved. The porous carbon electrode material has large specific surface area, high conductivity and good charge and discharge stability, and is widely used in electric double-layer capacitance deionization. The adsorption capacity of the currently reported graphene, carbide derivative carbon and various carbon-based composite electrode materials is improved compared with that of an activated carbon electrode, but the manufacturing process is complex. Thus, activated carbon still has a competitive advantage in current large-scale applications that is readily available. However, the activated carbon electrode in the traditional CDI process has the defects of low adsorption specific capacity, low charge efficiency, low suitable desalination concentration, improved cycling stability and the like.
Membrane Capacitive Deionization (MCDI) has improved in all of the above aspects, and shows the characteristics of stable water quality, small fluctuation of pH and high cyclicity, but the adsorption capacity is still low. The Faraday battery material and pseudo-capacitor material used in lithium ion and sodium ion batteries are applied to the great improvement of the desalting capacity in the mixed capacitance deionization (HCDI), but the energy storage principle of the materials is mainly ion storage and interlayer ion intercalation accompanied by oxidation-reduction reaction generated in and on the surfaces of electrodes. Therefore, the main problems of low water yield caused by the limitation of reaction kinetics and cycle performance attenuation caused by the volume shrinkage of the material structure are shown in the ion intercalation kinetics and the charge transfer rate which are poorer than those of the traditional carbon material.
With the rising reports of improving the energy density of the ion battery by coupling the electrode interface redox reaction with the double electric layer capacitance to improve the electrochemical charge storage mechanism, the research of improving the capacitive deionization (RCDI) by oxidation-reduction electrolyte based on the MCDI and HCDI processes is continuously reported. According to the characteristics of the electrical property of the used couple and the standard oxidation-reduction potential, the designed structure of the desalting device is usually a three-channel type, namely a positive electrode, a negative electrode and a middle desalting channel which are respectively formed by adopting an anion exchange membrane and a cation exchange membrane. The oxidation-reduction reaction is expanded from the electrode to the electrolyte, because the oxidation-reduction reaction of electrolyte ions is simple, and the kinetic standard rate constant k 0 Larger, faster kinetics of the reaction process relative to that occurring within or at the interface of the cell-type electrode material, which allows the redox reaction to take precedence over the oxidation and reduction reactions of the carbon electrode itself, slowing the oxidation of the carbon electrode and making the electrode more stable. Furthermore, the capacity contribution of the redox capacitor is higher than that of the electric double layer capacitor, the redox desalting capacity is 2.39 times of that of the electric double layer capacitor, reversible electrolyte reaction is more important for desalting the system, and therefore, continuous and stable desalting effect is shown, and 120 cycles are circulatedOr more than 80% for a longer period. Currently reported redox electrolytes include sodium iodide, sodium ferricyanide, sodium ferrocyanide, vanadium chloride, and the like. Wherein sodium iodide, sodium ferricyanide and sodium ferrocyanide are used as cathode electrolyte, and 3I is adopted in the charge-discharge process - /I 3 - ，Fe(CN) 6 3- /Fe(CN) 6 4- The change of ion valence state occurs to promote the cation Na + Adsorption and release. If the shuttling of electrolyte ions occurs during long-term cycling, it can cause contamination of the water to be treated. Vanadium chloride is used as an anolyte and passes through a pair of electrodes V 3+ /V 2+ The conversion promotes the adsorption of the anion Cl < - >, but the price is higher and is not dominant in large-scale application.
Disclosure of Invention
The present invention is to solve the above-mentioned technical disadvantages, and an object of the present invention is to provide a multi-channel capacitive desalination apparatus and a desalination method constructed by copper ion redox electrolyte, which are compatible with Cu by the separation and ion sieving effects of an ion exchange membrane 2+ /Cu + The oxidation-reduction potential of the electric pair is used for realizing the promotion of the specific capacity of ion adsorption, and the aim of promoting the desalting performance and the desalting stability is fulfilled.
The invention provides a multi-channel capacitive desalting device constructed by copper ion redox electrolyte, which is provided with a cathode and an anode, wherein the anode is a functional activated carbon anode, the functional activated carbon anode comprises an activated carbon electrode, an anion exchange membrane and sodium chloride and copper chloride active electrolyte solution which are added into a first channel formed between the activated carbon electrode and the anion exchange membrane, a desalting channel is formed between the anion exchange membrane and the cathode, and the NaCl solution to be treated is desalted through the desalting channel.
Preferably, the cathode is an activated carbon electrode.
Preferably, the cathode is a functional activated carbon cathode, the functional activated carbon cathode comprises an activated carbon electrode, an anion exchange membrane and sodium chloride and copper chloride active electrolyte solution which are added into a second channel formed between the activated carbon electrode and the anion exchange membrane, a desalting channel is formed between the functional activated carbon anode and the anion exchange membrane of the functional activated carbon cathode, and a cation exchange membrane is arranged in the desalting channel to divide the desalting channel into a desalting chamber and a concentrated water chamber.
Preferably, the first channel and the second channel are connected through a pipeline to form a circulation loop, and a circulation pump is arranged on the circulation loop.
Preferably, the cathode is a low-potential redox electrode, and the low-potential redox electrode is made of a redox reaction electrode material, including but not limited to NaTi 2 (PO) 3 。
Preferably, the low potential redox electrode further comprises a cation exchange membrane, and Cr (EDTA) which is added in a third channel formed between the low potential redox electrode and the cation exchange membrane and comprises but not limited to EDTA (ethylene diamine tetraacetic acid) for complexing Cr ions - /Cr(edta) 2- An electrolyte solution.
Preferably, the first channel is connected with an external first redox electrolyte pool through a pipeline to form a circulation loop, and a circulation pump is arranged on the circulation loop.
Preferably, the third channel is connected with an external second redox electrolyte pool through a pipeline to form a circulation loop, and a circulation pump is arranged on the circulation loop.
Preferably, the activated carbon electrode is one of a fixed electrode or a flow electrode.
A multi-channel capacitance desalting method for constructing copper ion redox electrolyte includes such steps as desalting the NaCl solution to be treated by any desalting unit, applying opposite polarities of power supply to cathode and anode to generate electric field between them, on-line recording the electric conductivity and pH variation of NaCl solution to be treated by water quality multi-parameter analyzer, and controlling the voltage and current charge-discharge program by electrochemical workstation. When constant voltage charging and discharging is adopted, the working voltage is 0.8-1.2V; when constant current charge and discharge is adopted, the step current is different according to the concentration of the anolyte solution, when the concentration ratio of the sodium chloride to the copper chloride solution is 20:2-20:3, the step current is 2.8mA/-2.8mA/-4.2mA/2.8mA or 4.2mA/-4.2mA/-12.6mA/4.2mA, and when the concentration ratio of the sodium chloride to the copper chloride solution is 20:3-20:7, the step current is 4.9mA/-4.9mA/-25.2mA/4.9 mA. The concentration of the NaCl solution to be treated is 5 mM-100 mM.
The invention provides a multi-channel capacitive desalting device constructed by copper ion redox electrolyte and a preparation method thereof, and the device has the following beneficial effects:
(1) the invention provides Cu by using the copper chloride solution with higher economic benefit 2+ /Cu + The electric pair realizes the adsorption and separation of anions and cations on two sides of the electrode by using the change of ion valence state caused by oxidation and reduction reactions generated in the charge and discharge processes of the anode and the cathode. The invention reasonably matches the electrolyte, the electrolytic material and the structure from the electrolyte construction functional electrode, improves the ion adsorption capacity of the device, reduces the adsorption energy consumption and improves the cycle stability, thereby realizing the aim of improving the desalting performance of the system and reducing the production cost. The invention can utilize the double carbon electrode, can also utilize the cation reaction material to prepare the electrode, and simultaneously Cu 2+ /Cu + The electrolyte has better reversible cycle, and Cu is used 2+ /Cu + Can not permeate anion exchange membrane, can not cause the pollution of treated water, and is environment-friendly and pollution-free.
(2) The invention can adopt different copper ion redox electrolyte desalination systems selected according to the concentration of desalted water and the set desalination target, and has obvious flexibility advantage in different scale applications. Not only Activated carbon/Activated carbon (Activated carbon) symmetrical electrodes can be used, but also Activated carbon/NaTi can be used for cation adsorption 2 (PO) 3 The mixed electrode (cation adsorption redox reaction capacitor material including but not limited to sodium titanium phosphate) and the electrolyte solution matched with the anode and the cathode to circulate are used for further improving the ion adsorption capacity.
(3) The invention can control the using amount of the ion exchange membranes according to the cost requirement of a user, and selects different copper ion redox electrolyte desalination systems and implementation modes. Specifically, when the structure of the device is selected, a two-channel system, a three-channel system and a four-channel system can be selected to realize the increase of the adsorption capacity of the anions and cations.
(4) The multi-channel capacitance deionization technology constructed by the copper ion redox electrolyte has better economic, environmental and social benefits in the aspects of energy conservation, environmental protection and sustainable development, and has very strong applicability.
Drawings
FIG. 1 shows two-pass AC// AC CuCl as shown in example 1 2 (Cu 2+ /Cu + ) A schematic diagram of a redox electrolyte desalination unit;
FIG. 2 shows the example 2AC// AC four-channel CuCl 2 (Cu 2+ /Cu + ) A schematic diagram of a redox electrolyte desalination unit;
FIG. 3 shows AC// NaTi of example 3 2 (PO) 3 A schematic structural diagram of a two-channel redox electrolyte mixed capacitance deionization desalination device;
FIG. 4 shows AC// NaTi of example 4 2 (PO) 3 A schematic structural diagram of a three-channel redox electrolyte mixed capacitance deionization desalination device;
FIG. 5 is a diagram showing the analysis of the desalted system in example 1, wherein (a) the change in voltage and current and the conductivity of treated water and (b) Cu 2+ /Cu + Before and after the electrolyte is added, the desalting performance of the sequential batch type constant voltage and continuous flow constant current under 2 charge-discharge operation modes is compared, and (c) Cu with different concentrations is added 2+ /Cu + Analysis of electrolyte desalting Performance SAC, SAR, charge efficiency, E m 。；
FIG. 6 is a diagram showing the performance analysis of the desalination system in example 2, (a) an activated carbon electrode under a three-electrode condition, 100mM NaCl +10mM Cu 2+ /Cu + Cyclic voltammetry test curve in electrolyte, (b) constant current charge-discharge test curve, (c) concentration change curve of desalted water and concentrated water under 1.2V working voltage, (d) desalination performance analysis SAC, SAR, charge efficiency, E under different working voltages m 。；
FIG. 7 shows a low potential redox electrode NaTi used in example 3 2 (PO) 3 A performance test chart; (a) NaTi in three-electrode system 2 (PO) 3 Cyclic voltammetry test curves in 1M NaCl solution, (b) AC// NaTi 2 (PO) 3 A mixed capacitor cyclic voltammetry test curve;
FIG. 8 is a diagram of the desalination system performance analysis of example 3; (a) CuCl 2 (Cu 2+ /Cu + ) The voltage, current and treated water concentration change curve of the redox electrolyte desalination system test, (b) the voltage, current and treated water concentration change curve under the condition of no redox electrolyte, (c) the cycle performance test of the redox electrolyte desalination system;
FIG. 9 is a diagram of the desalination system performance analysis of example 4; (a) EDTA complexing Cr ion Cr (EDTA) added to cathode - /Cr(edta) 2- Voltage, current and desalted water concentration change curve after electricity is paired, (b) EDTA complex Cr ion Cr (EDTA) is added to the cathode - /Cr(edta) 2- Desalting cyclicity test chart after electric pairing.
The labels in the figure are: 1. the device comprises an anode, 11 active carbon electrodes, 12 anion exchange membranes, 13 first channels, 2 cathodes, 21 second channels, 22 third channels, 3 desalting channels, 31 cation exchange membranes, 32 desalting chambers, 33 concentrated water chambers, 4 first redox electrolyte tanks, 5 circulating pumps and 6 second redox electrolyte tanks.
Detailed Description
The invention is further described below in conjunction with the drawings and the specific embodiments to assist in understanding the contents of the invention. The method used in the invention is a conventional method if no special provisions are made; the raw materials and the apparatus used are, unless otherwise specified, conventional commercially available products.
Example 1
Shown in FIG. 1(a) as AC// AC two-channel CuCl 2 (Cu 2+ /Cu + ) Redox electrolyte desalination system (DC-RCDI). This example uses Cu 2+ /Cu + The copper ion pair is used as an anolyte to construct a functional activated carbon anode, and is matched with an activated carbon electrode 11 (cathode 2) for desalination. The functional activated carbon anode comprises an activated carbon electrode 11, an anion exchange membrane 12 and sodium chloride and copper chloride active electrolyte solution which are added into a first channel 13 formed between the activated carbon electrode and the anion exchange membrane, a desalting channel 3 is formed between the anion exchange membrane 12 and a cathode 2, the first channel 13 is connected with an external first oxidation reduction electrolyte pool 4 through a pipeline to form a circulation loop, a circulation pump 5 is arranged on the circulation loop, and NaCl solution to be treated is desalted through the desalting channel 3. The activated carbon electrodes 11 of the present embodiment are allA fixed electrode is used.
Fig. 1(b) shows an ion adsorption and desorption process corresponding to the charge and discharge process. (1) In the charging stage, ion and electricity pairs in the anode circulating electrolyte are oxidized, and Cu + Oxidation to higher valence Cu 2+ . Under the action of voltage, the anions in the NaCl solution to be treated permeate the anion exchange membrane 12 to reach the anode 1, and meanwhile, in order to balance Cu 2+ Will cause more anions to be adsorbed through the anion exchange membrane 12; at this time, the cations are adsorbed by the activated carbon electrode 11, and the desalting effect is achieved. (2) During the discharge stage, negative positive charges are accumulated due to reverse discharge, and high valence state Cu is generated 2+ Reduction to Cu + . The anions adsorbed by the charging stage pass through the anion exchange membrane 12 due to electrostatic repulsion and are returned to the treated water again. The positive ions of the negative electrode are released under the action of the same charges, and the regeneration and concentration effects of the electrode are realized.
The specific operation is as follows:
firstly, installing a capacitance deionization device, sequentially assembling a prepared anode electrode plate (activated carbon electrode 11), an anion exchange membrane 12 and a cathode electrode plate (activated carbon electrode 11), wherein a fluid channel is realized by a silica gel gasket and reserved holes, the widths of a first channel 13 and a desalination channel 3 are both 3mm, and the first channel and the desalination channel are encapsulated by an outer polyethylene shell. The mass ratio of the positive electrode to the negative electrode (positive electrode: negative electrode) is 1: 3.
And II, copper ion redox electrolyte solution, which consists of 100mM sodium chloride solution and 10mM copper chloride solution. The comparison scheme of the copper chloride solutions with different concentrations is 100mM NaCl +15, 25, 35mM CuCl 2 And (3) an electrolyte. In the experimental process, after the copper ion redox electrolyte is deoxidized, a circulating pump 5 is adopted to perform the deoxidation at the flow rate of 2.1mLmin -1 Continuously circulating on the positive electrode side.
Thirdly, the middle desalting channel 3 is 20mM NaCl solution to be treated, and the treatment is carried out by adopting 2 modes of single continuous flow and circulation sequencing batch, and is carried out by a circulating pump 5 at 2.1mLmin -1 The flow rate is passed through the desalting channel 3 (same as the flow rate of the circulating copper ion redox electrolyte).
And fourthly, connecting the anode and the cathode of the device with the anode and the cathode of a power supply respectively, and controlling a process operation voltage and current program through an electrochemical workstation. In this embodiment, the charging and discharging procedures are constant current charging and discharging and constant voltage charging and discharging. Wherein the constant voltage sequencing batch experiment procedure comprises 1.2V charging and-1.2V discharging for 30min respectively. The charging and discharging process and the corresponding ion adsorption and desorption process adopted by the constant current and continuous flow experiment are specifically described as follows: the step current is 2.8mA/-2.8mA/-4.2mA/2.8mA, and the corresponding voltage interval is 0V-1.2V-0V. As shown in fig. 5(a), the whole charging and discharging process is divided into four stages I, II, III and IV.
And fifthly, recording the conductivity change of the NaCl solution to be treated on line by adopting a water quality multi-parameter analyzer. The section I is charged corresponding to constant current, the conductivity is reduced to a constant value, the section II adopts the current same as that of the section I to be charged to discharge to 0V, and the desorption can be fully realized, so that the balance of absorption and desorption is achieved. III stage discharge to-1.2V to achieve Cu 2+ /Cu + Is reduced at the positive electrode to ensure the cycle reversibility, so that the concentration of the treated water in the stage III rapidly rises. And in the stage IV, after the reverse discharge is finished, the voltage is restored to 0V, the charge-discharge process of a single period is realized, and in the stage, the conductivity falls back to the initial value along with the flow of the water flow.
And sixthly, analyzing by combining a desalting conductivity change curve and an electrochemical workstation current-voltage change curve. The water production rate WR in this example test was determined as the ratio of the duration of the charging phase to the duration of the entire cycle, with a water production rate WR > 50%, and we used a larger discharge current, e.g., -11.2mA, to bring the WR close to 60% during the reverse discharge phase. The pH of the circulating electrolyte on the circulating side in the charging and discharging process is below 5.1, which is favorable for Cu 2+ /Cu + The electric pair exists in an ionic form. The pH change of the treated water is relatively flat, and the delta pH is less than 0.5. The conductivity curve shows that the conductivity of the effluent in the I section and the IV section is rapidly reduced to the adsorption stage. II, IV discharge is the concentration stage. And I, III, two stages of completing charging and reverse charging by deviating the potentials of the two electrodes from an open circuit potential, namely a balance potential in a non-powered state. In the stage II and the stage IV, the potential difference between the two electrodes is gradually reduced and returns to the balance potential, namely the stage of outputting electric charge, energy recovery can be carried out, and 47.99% of the total electric quantity can be recovered in the experiment. In addition, FIG. 5(b) shows the copper ion electrolyteThe desalination system compares the desalination performance under 2 charge-discharge operation modes of sequencing Batch constant voltage (Batch, CV) and Continuous current (Continuous, CC), and fig. 5(c) shows that the specific capacity, adsorption rate, charge efficiency and specific energy consumption data analysis under two operation modes increase Cu 2+ /Cu + The adsorption specific capacity effect of the material after electric pairing is more prominent. SAC can reach 34.46mg g in CV mode -1 2.04 times of that of a pure sodium chloride solution, and therefore, Cu was tested 2+ The capacity contribution value after the active electrolyte is 1.04 times that of the active carbon in a 100mM NaCl electrolyte. SAC with specific adsorption capacity of 23.91mg g under CC mode -1 2.63 times of pure sodium chloride solution.
Furthermore, the specific capacity for desalting depends on Cu in the electrolyte 2+ /Cu + The concentration is increased, and the electric pair concentration is 15mM Cu under the condition of 4.2mA/-12.6mA current 2+ /Cu + Is 10mM Cu 2+ /Cu + The specific capacity of the adsorption is 1.23 times of that of the adsorption, the specific capacity is increased to 25mM, and the specific capacity is obviously increased to 1.58 times of that of 10mM by adopting 4.9mA/-25.2mA current charge and discharge. Specific energy consumption E m Also continuously decreases and is maintained at 210KJ mol -1 。
Example 2
FIG. 2(a) shows AC// AC four-channel CuCl 2 (Cu 2+ /Cu + ) Redox electrolyte desalination system (FC-RCDI). The difference between this embodiment and embodiment 1 is that the cathode 2 is a functional activated carbon cathode, the functional activated carbon cathode includes an activated carbon electrode 11, an anion exchange membrane 12, and sodium chloride and copper chloride active electrolyte solution added in the second channel 21 formed therebetween, a desalination channel 3 is formed between the functional activated carbon anode and the anion exchange membrane 12 of the functional activated carbon cathode, and a cation exchange membrane 31 is arranged in the desalination channel 3 to divide the desalination channel 3 into a desalination chamber 32 and a concentrated water chamber 33. The circulation loop of the present embodiment is formed by connecting the first channel 13 and the second channel 21 through a pipeline, and the circulation loop is also provided with the circulation pump 5. The activated carbon electrodes 11 of the present embodiment also employ fixed electrodes.
The embodiment shown in FIG. 2(b) employs the first passage 13, the second passage 21, the desalination chamber 32 and the concentrated waterChamber 33 four-channel desalination, Cu 2+ /Cu + The copper ion electrolyte flows through the first passage 13 and the second passage 21 in turn by the circulation pump 5. Cu in the first channel 13 + Is oxidized into Cu 2+ In the second channel 21Cu 2+ Is reduced to Cu + In the circulation process, the potential difference of the two sides of the electrode is utilized to complete continuous Cu 2+ /Cu + The oxidation reduction valence state changes, and the double electric layers of the coupled activated carbon electrodes are desalted. The embodiment avoids the process of energy consumption caused by anode reverse discharge, can realize continuous and uninterrupted desalination under the continuous flow condition, and saves energy and reduces emission.
The specific operation is as follows:
the method comprises the steps of installing a capacitance deionization device, sequentially assembling prepared anode electrode plates (activated carbon electrodes 11), anion exchange membranes 12, cation exchange membranes 31, anion exchange membranes 12 and cathode electrode plates (activated carbon electrodes 11), enabling a fluid channel to be achieved through silica gel gaskets and reserved holes, enabling the width of the channel to be 3mm, and packaging the channel by an outer polyethylene shell. The mass ratio of the positive electrode to the negative electrode (positive electrode: negative electrode) was 1: 1.
Secondly, oxidizing and reducing the electrolyte solution by copper ions. In the positive electrode and the negative electrode, the copper ion redox electrolyte solution adopted in the channel formed by the electrode plate and the anion exchange membrane 12 is 100mM NaCl solution added with 10mM CuCl 2 The active electrolyte. Deoxidizing the copper ion redox electrolyte, and then using a circulating pump to perform 2.1mLmin at a certain flow rate -1 Continuously circulate between the anode and the cathode to generate Cu 2+ /Cu + The valence state of the redox couple is changed.
And thirdly, the middle desalting channel 3 is 20mM NaCl solution to be treated. The desalting chamber 32 and the concentrated water chamber 33 are respectively circulated in respective channels continuously in a circulation sequencing batch mode by adopting 17mL of 20mM NaCl, and the control flow rate of the circulating pump is 2.1mLmin -1 。
And fourthly, connecting the anode and the cathode of the device with the anode and the cathode of a power supply respectively, and controlling a process operation voltage and current program through an electrochemical workstation. The experiment adopts a constant voltage charging and discharging procedure. Wherein the constant voltage sequencing batch experimental procedure is 1.2V charging and0V discharge for 30min each. Wherein, in order to test the optimal working voltage of the system, three values of 0.8V, 1.0V and 1.2V are adopted for testing, and the testing is mainly carried out according to Cu 2+ /Cu + The redox potential difference of the redox couple was determined for the test in 100mM NaCl solution.
And fifthly, recording the change of the conductivity meter of the water to be treated on line by adopting a water quality multi-parameter analyzer. The test conductivity of the desalting chamber 30min before charging is reduced, and the test conductivity of the concentrated water chamber is increased. And in the discharging stage, 0V is adopted for discharging for 30min, and the conductivity value falls back to the initial value.
And sixthly, analyzing by combining a desalting conductivity change curve and an electrochemical workstation current-voltage change curve. The desalting experiment was first conducted by testing the activated carbon electrode at 100mM NaCl +10mM Cu in a three-electrode condition 2+ /Cu + The cyclic voltammetry and constant current charge-discharge curve in the redox electrolyte solution is further determined to obtain Cu 2+ /Cu + And (3) carrying out experimental working voltage and operation mode analysis on the energy storage and desalination mechanism of the electric pair by combining the oxidation-reduction potential of the electric pair. The cyclic voltammogram test of FIG. 6(a) shows that there are two oxidation peaks at 0.15V and 0.43V, respectively, and a reduction peak at-0.4V. Referring also to FIG. 6(b), the potential value of redox generation of the GCD test further determines Cu 2+ /Cu + The energy storage and desalination mechanism of the electric pair is ion excess adsorption brought by charge storage accompanied by oxidation reduction and charge neutrality of a rear electrode of the membrane. FIG. 6(c) desalination experiment using 1.2V common working voltage, testing 30min desalination and concentration characteristics, the conductivity of the NaCl solution to be treated in the desalination chamber 32 decreased rapidly, accompanied by a rapid increase in the conductivity of the concentrate chamber. As can be seen in the figure, the concentration decrease and increase values of the solutions on both sides are substantially the same. And 0V discharge is adopted, energy recovery is not considered, the test concentrations of the solutions at two sides are recovered to the initial state, and the voltage value shows that the reversible oxidation reduction of the copper ion couple in the electrode channels at two sides can be realized, and the reversible cyclicity is good. FIG. 6(d) is a diagram showing the SAC, adsorption rate SAR, charge efficiency and specific energy E for testing desalination specific capacity under the conditions of three working voltage values of 0.8V, 1.0V and 1.2V m . Along with the increase of the voltage, the desalting specific capacity SAC is gradually increased and is 34.668mg g -1 ，51.06mg g -1 ，59.14mg g -1 . The desalting rate SAR is also increased in turn, and can reach 0.986mg g at 1.2V -1 min -1 . The charge efficiency is above 86%, wherein the maximum of 1.0V is 90.78%. In addition, the specific energy consumption E for desalination of the system m Lower, 1.0V at 106KJ mol -1 At 0.8V, only 88.39KJ mol -1 1.2V has larger working current due to working voltage, and the maximum calculated specific energy consumption is 132.78KJ mol -1 The specific energy consumption values are smaller than those of the embodiment 1, and are basically below the desalination energy consumption level of the fixed electrode reported at present. Therefore, the experiment confirms that 1.0V is the optimal working voltage condition, so that Cu can be ensured 2+ /Cu + Reversible oxidation and reduction are continuously generated on the electrodes at the two sides, so that the cyclic stability of electrode desalination is ensured.
Example 3
FIG. 3 shows an AC// low potential redox electrode material (including but not limited to NaTi) 2 (PO) 3 ) The present example differs from example 1 in that the cathode 2 does not use the activated carbon electrode 11 but uses a redox reaction electrode material (NaTi) in the two-channel mixed capacitance deionization system 2 (PO) 3 ) As the cathode 2.
Cu 2+ /Cu + The copper ion electrolyte is continuously circulated in the first passage 13 by the circulation pump 5. During charging, Cu in the first channel 13 + Is oxidized into Cu 2+ Because the electrolyte solution after the membrane keeps neutral, additional anion adsorption is realized; the cathode 2 uses NaTi 2 (PO) 3 Middle Ti 4+ Ion reduction to produce Ti 4+ To Ti 3+ The valence state of the ion is changed, cation adsorption is realized along with the embedding of Na < + >, and the opposite is realized during discharging.
The specific operation is as follows:
firstly, installing a capacitive deionization device, and preparing an anode electrode plate (an activated carbon electrode 11), an anion exchange membrane 12 and a cathode electrode plate (NaTi) 2 (PO) 3 NTP), the fluid channel is realized through a silica gel gasket and a reserved hole, the width of the channel is 3mm, and the channel is packaged by an outer polyethylene shell. Positive and negative electrodeThe active material mass ratio (positive electrode: negative electrode) of (1: 1).
Secondly, oxidizing and reducing the electrolyte solution by copper ions. Consists of 100mM sodium chloride and 10mM copper chloride. Deoxidizing the copper ion redox electrolyte, and then adopting a circulating pump 5 to perform 2.1mLmin at a certain flow rate -1 Continuously circulating on the positive electrode side.
And thirdly, the middle desalting channel is 20mM NaCl solution to be treated. In a single continuous flow mode, with a circulation pump at 2.1mLmin -1 The flow rate flows through the desalination channel 3.
And fourthly, connecting the anode and the cathode of the device with the anode and the cathode of a power supply respectively, and controlling a process operation voltage and current program through an electrochemical workstation. Constant current charging and discharging is adopted in the experiment, the step current is 2.8mA/-2.8mA, the corresponding cut-off charging and discharging working voltages are 1.6V and 0V respectively, and the reversible circulation of the electricity pair can be realized by adopting 0V discharging. When the desalting performance was tested under the condition without a redox electrolyte, the charge cut-off voltage was 1.4V.
And fifthly, recording the change of the conductivity meter of the water to be treated on line by adopting a water quality multi-parameter analyzer. The conductivity of the desalting channel corresponding to the charging stage is reduced in a test, and the conductivity value falls back to the initial value in the discharging stage.
And sixthly, analyzing by combining a desalting conductivity change curve and an electrochemical workstation current-voltage change curve. FIG. 7(a) shows NaTi in a three-electrode system 2 (PO) 3 Cyclic voltammetry test curves in 1M NaCl solution, FIG. 7(b) AC// NaTi 2 (PO) 3 Mixed capacitor cyclic voltammetry test curves. As can be seen from the cyclic voltammogram test of FIG. 7(a), NaTi 2 (PO) 3 The oxidation-reduction peak of (NTP) appears at a potential value lower than that of Cu 2+ /Cu + The redox peaks of the couple (FIG. 6(a)) are more negative, ranging from-0.6V to 1.0V, respectively. While the window of stable potential in 1M NaCl solution is more negative than active carbon. Thus, the experiment tested AC// NaTi 2 (PO) 3 The cyclic voltammogram of the hybrid capacitor determines the optimum operating voltage of the device, and the effect of the voltage on the capacity. As can be seen from fig. 7(b), as the voltage of the device increases, the area enclosed by the CV increases, and the energy density of the capacitor gradually increases. The curve from 0 to 1.6V can be seenTo a pair of redox peaks, in particular Ti 4+ /Ti 3+ Reaction of the ions.
The invention combines the test results of the above experiments to respectively test whether the anode is added with Cu or not 2+ /Cu + Desalting performance in both cases of redox electrolyte. Specifically, in FIG. 8(a), the anode was cycled with 100mM sodium chloride and 10mM copper chloride electrolyte solution and in FIG. 8(b), the anode was cycled with only 100mM sodium chloride solution. Due to the addition of Cu 2+ /Cu + The redox electrolyte can increase the capacitance value of the anode of the activated carbon, and the increase of the capacitance increases the stored electricity quantity required for increasing a certain potential value, so that under the condition of the same charging current of the anode and the cathode, the potential value of the anode changes more slowly, the potential of the cathode continuously approaches to the negative side, and the working voltage of the device is higher. Therefore, under the condition of the same current density, no Cu exists 2+ /Cu + Under redox electrolyte conditions, the charging voltage of the device can only reach 1.4V. The change curve of the concentration of the desalted water and the charge-discharge curve are calculated, and the desalting specific capacity is 13.31mg g after the redox electrolyte is added -1 Increased to 31.37mg g -1 The adsorption rate also increased to 1.71mg g -1 min -1 The charge efficiency is 89.54 percent, and the energy consumption is 136KJ mol -1 . FIG. 8(c) shows the stability of the desalination cycle under 100mM NaCl and 10mM cupric chloride, and the results show that the system has better stability, and the capacity is maintained above 60% after 80 cycles of the cycle.
Example 4
As shown in fig. 4, the circulating electrolyte is added to the cathode 2 to form a three-channel redox electrolyte desalination system. This embodiment is an improvement on the basis of embodiment 3, and the difference between this embodiment and embodiment 3 is that the low potential redox electrode further includes a cation exchange membrane 31, and Cr (EDTA) formed by adding EDTA complexed with Cr ions in the third channel 22 between the low potential redox electrode and the cation exchange membrane 31 - /Cr(edta) 2- An electrolyte solution; the third channel 22 is connected with an external second redox electrolyte pool 6 through a pipeline to form a circulation loop, and the circulation loop is also provided with a circulation pump 5. Anode 1 active carbon electrode and cathode phosphorusSodium titanium acid NaTi 2 (PO) 3 The electrodes are all fixed electrodes.
In the embodiment, the cathode 2 adopts EDTA with negative standard redox potential to complex Cr ions (EDTA) - /Cr(edta) 2- The cathode 2 is constructed by coupling the electrode pair as cathode electrolyte with redox reaction electrode material. Cu generation in positive electrolyte solution during charging + To Cu 2+ The anode electrode material NaTi 2 (PO) 3 Generation of Ti with electrolyte solution 4+ To Ti 3+ And Cr (edta) - To Cr (edta) 2- Reduction of (2). Because positive charges of the positive electrode are increased along with oxidation and reduction, negative charges of the negative electrode are increased, and adsorption of anions and cations is further realized respectively. And the discharging process is reversed. NaTi because the cathode material and redox electrolyte have a low standard electrode redox potential 2 (PO) 3 And Cr (edta) - /Cr(edta) 2- Can be connected with anode 1Cu 2+ /Cu + Functional active carbon anode constructed by copper ion electrolyte very Cr (edta) - /Cr(edta) 2- Good potential matching and open circuit voltage at Cu 2+ /Cu + The charge and discharge process can be carried out by charging to a cut-off voltage of 1.2V and discharging to 0V below the reduction potential of copper ions. The desalting and concentration during charging and discharging were the same as in example 1, but the effect was better in terms of energy consumption and desalting performance.
The specific operation is as follows:
firstly, installing a capacitive deionization device, and preparing an anode electrode plate (an activated carbon electrode 11), an anion exchange membrane 12, a cation exchange membrane 31 and a cathode electrode plate (NaTi) 2 (PO) 3 NTP), the fluid channel is realized through a silica gel gasket and a reserved hole, the width of the channel is 3mm, and the channel is packaged by an outer polyethylene shell. The mass ratio of the active material of the positive electrode to the negative electrode (positive electrode: negative electrode) was 1: 1.
Secondly, copper ion redox electrolyte solution and EDTA complex Cr ion redox electrolyte solution. The copper ion redox electrolyte solution consists of 100mM sodium chloride and 10mM copper chloride active electrolyte, and EDTA complexes Cr ionsThe electrolyte solution was prepared from 100mM NaCl solution and 10mM Cr (edta) - /Cr(edta) 2- The active electrolyte composition. After deoxygenation, a circulating pump 5 is adopted to perform deoxygenation at a certain flow rate of 2.1mLmin -1 Continuously circulating on the positive electrode side and the negative electrode side respectively.
And thirdly, the middle desalting channel 3 is 20mM NaCl solution to be treated. In a single continuous flow mode, 2.1mLmin by a peristaltic pump -1 The flow rate flows through the desalination channel 3.
And fourthly, connecting the anode and the cathode of the device with the anode and the cathode of a power supply respectively, and controlling a process operation voltage and current program through an electrochemical workstation. Constant current charging and discharging are adopted in the experiment, the step current is 2.8mA/-2.8mA, and the corresponding cut-off charging and discharging working voltages are 1.6V and 0V respectively.
And fifthly, recording the change of the conductivity meter of the water to be treated on line by adopting a water quality multi-parameter analyzer. The conductivity of the desalting channel corresponding to the charging stage is reduced in a test, and the conductivity value falls back to the initial value in the discharging stage.
And sixthly, analyzing by combining a desalting conductivity change curve and an electrochemical workstation current-voltage change curve. FIG. 9(a) is a desalting performance test curve. Because the oxidation-reduction electrolyte is added to the positive electrode and the negative electrode, a charging platform appears at 1.4V to 1.6V in the charging stage, the concentration of the sodium chloride solution to be treated is quickly reduced in the initial stage, the reduction value is large, and the lowest point concentration reduction value is close to 120mgL -1 Calculated specific desalting capacity was 52.97mg g -1 (including the masses of the positive and negative electrodes), the adsorption rate increased to 3.50mg g -1 min -1 The charge efficiency is 98 percent, and the energy consumption is only 74.54KJ mol -1 Compared with the embodiment 3, the method has obvious improvement. FIG. 9(b) is a desalination cycle stability test, and the results show that the system has a significant improvement in cyclic desalination stability compared with example 3, and the capacity of the system is maintained above 90% after 80 cycles of circulation. The reason for the capacity retention in the test is mainly the negative Cr (edta) - /Cr(edta) 2- The oxidation pre-reduction of (A) counteracts the NaTi 2 (PO) 3 Na in the circulation + The structural change caused by intercalation and deintercalation contributes more to the capacity, while NaTi 2 (PO) 3 Voltage stabilization of electrode pair deviceThe contribution of the window is large. The present invention thus teaches that the redox reactive materials and redox counter ions used in the negative electrode include, but are not limited to, the sodium titanium phosphate (NTP) materials and EDTA-complexed Cr ions described above.
The invention aims at a redox active electrolyte desalination system to further promote anion adsorption, and provides an anolyte solution copper chloride which can be used for a positive electrode, and the copper chloride is obtained by CuCl 2 Cu in electrolyte solution 2+ /Cu + The redox reaction of the active couple achieves the purpose of improving the anion adsorption capacity. And, since Cu 2+ /Cu + The anion membrane can not permeate, the pollution of treated water can not be caused, the environment is protected, the pollution is not caused, the price is low, the method has more advantages in large-scale application, and the method can be widely applied to the technical fields of capacitive deionization desalination, water treatment and resource recovery.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (10)
1. The multi-channel capacitive desalting device constructed by copper ion redox electrolyte is provided with a cathode and an anode, and is characterized in that the anode is a functional activated carbon anode, the functional activated carbon anode comprises an activated carbon electrode, an anion exchange membrane and sodium chloride and copper chloride active electrolyte solution which are added into a first channel formed between the activated carbon electrode and the anion exchange membrane, a desalting channel is formed between the anion exchange membrane and the cathode, and NaCl solution to be treated is subjected to desalting treatment through the desalting channel.
2. The multi-channel capacitive desalination apparatus constructed by copper ion redox electrolyte as claimed in claim 1, wherein the cathode is activated carbon electrode.
3. The multi-channel capacitive desalination device constructed by copper ion redox electrolyte according to claim 2, wherein the cathode is a functional activated carbon cathode, the functional activated carbon cathode comprises an activated carbon electrode, an anion exchange membrane and sodium chloride and copper chloride active electrolyte solution which are added into a second channel formed between the activated carbon electrode and the anion exchange membrane, the desalination channel is formed between the functional activated carbon anode and the anion exchange membrane of the functional activated carbon cathode, and a cation exchange membrane is arranged in the desalination channel to divide the desalination channel into a desalination chamber and a concentrated water chamber.
4. The multi-channel capacitive desalination device constructed by copper ion redox electrolyte according to claim 3, wherein the first channel and the second channel are connected by a pipeline to form a circulation loop, and a circulation pump is arranged on the circulation loop.
5. The multi-channel capacitive desalination apparatus constructed by copper ion redox electrolyte as claimed in claim 1, wherein the cathode is a low potential redox electrode, and the low potential redox electrode is made of redox reaction electrode material including but not limited to NaTi 2 (PO) 3 。
6. The multi-channel capacitive desalination device constructed by copper ion redox electrolyte as claimed in claim 5, wherein the low potential redox electrode further comprises a cation exchange membrane, and Cr (EDTA) added in a third channel formed by EDTA complexing Cr ions and formed by the EDTA is formed between the low potential redox electrode and the cation exchange membrane - /Cr(edta) 2- An electrolyte solution.
7. The multi-channel capacitive desalination device constructed by copper ion redox electrolyte according to claim 2, 5 or 6, wherein the first channel is connected with an external first redox electrolyte pool through a pipeline to form a circulation loop, and a circulation pump is arranged on the circulation loop.
8. The multi-channel capacitive desalination device constructed by copper ion redox electrolyte according to claim 6, wherein the third channel is connected with an external second redox electrolyte tank through a pipeline to form a circulation loop, and a circulation pump is arranged on the circulation loop.
9. The multi-channel capacitive desalination apparatus constructed by copper ion redox electrolyte as claimed in claim 1, wherein the activated carbon electrode is one of a fixed electrode or a flowing electrode.
10. A multi-channel capacitance desalination method constructed by copper ion oxidation reduction electrolyte is characterized in that a NaCl solution to be processed is desalted through any desalination device of claims 1 to 9, opposite power supply polarities are applied to the cathode and the anode in the desalination process to generate an electric field between the cathode and the anode, a water quality multi-parameter analyzer is used for recording the change of the conductivity and the pH of the NaCl solution to be processed on line, an electrochemical workstation is used for controlling voltage and current charging and discharging programs, when constant voltage charging and discharging are adopted, the working voltage is 0.8-1.2V, when constant current charging and discharging are adopted, the step current is different according to the difference of the concentration of the anode electrolyte solution, when the concentration ratio of sodium chloride and the copper chloride solution is 20:2-20:3, the step current is 2.8mA/-2.8 mA-4.2 mA/2.8 mA/4.2 mA/-12.6mA/4.2, when the concentration ratio of sodium chloride to copper chloride solution used was 20:3 to 20:7, the step current used was 4.9mA/-4.9mA/-25.2mA/4.9 mA.
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| CN115522071B (en) * | 2022-10-13 | 2023-09-26 | 华东理工大学 | Apparatus and method for activating electrodes |
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