ELECTRODIALYSIS DEVICE AND METHOD FOR SELECTIVE REMOVAL OF DRINKING WATER TARGET IONS

Abstract

An electrodialysis device and method for selective removal of drinking water target ions were provided. It belongs to the technical field of drinking water safety. A method of electrodialysis with slightly brackish water is proposed. By means of ion electromigration control, the resistance is converted from the single membrane resistance to the diffusion boundary layer resistance; and the diffusion boundary layer is fully compressed by controlling the electrodialysis membrane, the electrodialysis membrane stack, and the electrodialysis process parameters. So that the relative electromigration rate of the target ions is improved. According to the method, the initial concentration effect, the competition effect, the synergistic effect, the concentration diffusion, the differential pressure permeation, and other influences of electrodialysis are integrated for selectively removing the target ions. It significantly reduces the cost of water treatment and improves the long-term stability and operational applicability of the device.

Claims

1. An electrodialysis method for selective removal of drinking water target ions, comprising: treating raw slightly brackish water by using an electrodialysis desalination process to obtain desalted water; wherein in the electrodialysis desalination process, the raw slightly brackish water is processed by controlling an electrodialysis membrane, an electrodialysis membrane stack, and electrodialysis process parameters; wherein a calculation general formula of a selective separation coefficient is: $S_B^A=\frac{C_{A\left(t\right)}/C_{A\left(0\right)}-C_{B\left(t\right)}/C_{B\left(0\right)}}{\left(1-C_{A\left(t\right)}/C_{A\left(0\right)}\right)+\left(1-C_{B\left(t\right)}/C_{B\left(0\right)}\right)};$ wherein A representing a target ion, and B representing total dissolved solids in a selected standard ion or actual solution in actual use; wherein an aperture of the electrodialysis membrane is less than 1 micron; and the selective separation coefficient of the electrodialysis membrane is in a range from −1 to 1; wherein the electrodialysis membrane is selected from a group comprising a controllable channel membrane, a compression diffusion boundary layer membrane, and an ion exchange membrane; wherein electrodialysis membrane stack comprises: two segments, wherein the segment is number of repeated flows of the raw slightly brackish water in the electrodialysis membrane stack; two stages, wherein a value of the stage is number of electrode plates in the electrodialysis membrane stack reduced by 1; and two chambers, formed by separating the electrodialysis membrane; wherein a separation coefficient for selectively removing the target ions is obtained from a following formula:
K=[k.sub.liquid.Math.k.sub.field.Math.(k.sub.membrane+k.sub.segment+k.sub.stage)].sup.k.sup.chamber; k.sub.x represents the selective separation coefficient; x represents a liquid, a field, a membrane, a segment, a stage, or a chamber; the kx is obtained from a calculation general formula of the selective separation coefficient, k.sub.liquid represents a selective separation coefficient of a target solution; k.sub.field represents an electrodialysis process parameter multi-field control selective separation coefficient such as electrodialysis membrane stack voltage, electrodialysis membrane stack flow rate, concentration difference of a dense dilute chamber, and pressure difference of a dense dilute chamber; k.sub.membrane represents an electrodialysis membrane selective separation coefficient; k.sub.segment represents a membrane selective separation coefficient of electrodialysis membrane stack; k.sub.stage represents a stage selective separation coefficient of electrodialysis membrane stack; k.sub.chamber represents a chamber selective separation coefficient of electrodialysis membrane stack; a range of K is 0.3-0.9;

2. The electrodialysis method according to claim 1, wherein the controlling of the electrodialysis process parameters comprises controlling parameters of electrodialysis membrane stack voltage, electrodialysis membrane stack flow rate, concentration difference of a dense dilute chamber, and pressure difference of a dense dilute chamber.

3. The electrodialysis method according to claim 1, wherein raw water flow rate in each segment of the electrodialysis membrane stack is greater than 0.5 m/sec or less than 0.5 m/sec, and the voltage in each segment of the electrodialysis membrane stack is greater than 0.5 volts/pair or less than 0.5 volts/pair.

4. The electrodialysis method according to claim 1, wherein total dissolved solids in the raw slightly brackish water is 0.5-40000 ppm.

5. The electrodialysis method according to claim 4, wherein a stage voltage of a first segment of the electrodialysis membrane stack is 0.1-2.0 volts/pair, and voltage of a second segment of the electrodialysis membrane stack is 30-300% of the stage voltage of the first segment.

6. The electrodialysis method according to claim 1, wherein each same chamber of the electrodialysis membrane stack is circulated and refluxed, and a reflux ratio of each same chamber of the electrodialysis membrane stack is 1-4.

7. The electrodialysis method according to claim 1, wherein the chamber of the electrodialysis membrane stack is filled with ion resin, a filling rate is 5-80% by volume.

8. The electrodialysis method according to claim 1, wherein a bipolar membrane chamber is added in the chamber of electrodialysis membrane stack, and a proportion of the bipolar membrane chamber is 1-30% based on number of chambers.

Description

DESCRIPTION OF THE DRAWINGS

[0055] FIG. 1 is a diagram of the influence of an initial ion concentration on membrane resistance;

[0056] FIG. 2 is a diagram of the principle of electrodialysis.

[0057] FIG. 3 is a diagram of an assembly mode of stages and segments of an electrodialysis membrane stack;

[0058] FIG. 4 is a diagram of a membrane pair in an electrodialysis membrane stack;

[0059] FIG. 5 is a diagram of the circulation backflow of a chamber in an electrodialysis membrane stack;

[0060] FIG. 6 is a diagram of a two-stage two-segment two-chamber electrodialysis membrane stack;

[0061] FIG. 7 is a schematic diagram of a two-stage three-segment four-chamber electrodialysis membrane stack;

[0062] FIG. 8 is a schematic diagram of a three-stage five-segment four-chamber electrodialysis membrane stack.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0063] The technical solutions of the present disclosure are further described in detail below with reference to specific embodiments and drawings. It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the embodiments according to the disclosure. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0064] The principle of electrodialysis used in the method of the present disclosure is shown in FIG. 2, and a functioning relationship of a selective separation coefficient for selective removal of target ions by the method of the present disclosure, as shown below:

K=[k.sub.liquid.Math.k.sub.field.Math.(k.sub.membrane+k.sub.segment+k.sub.stage)].sup.k.sup.chamber.

[0065] In some embodiments, stages, and segments of the electrodialysis membrane stack assembly mode are shown in FIG. 3. FIG. 3 is merely used as a presentation to help understand and does not constitute a limitation on the present disclosure.

[0066] In some embodiments, the membrane pairs in the electrodialysis membrane stack are shown in FIG. 4. An electrodialysis membrane pair is formed by the electrodialysis membrane, and the circulation is repeated. FIG. 4 is merely a demonstration of membrane pairs, which helps to understand and does not constitute a limitation on the present disclosure.

[0067] In some embodiments, the circulation reflux of the chamber in the electrodialysis membrane stack is shown in FIG. 5. Each same chamber is circulated and refluxed, and the reflux ratio of each same chamber is 1-4. The same chamber means that the desalination chamber refluxes in the desalination chamber and the concentrated chamber refluxes in the concentrated chamber, and the desalination chamber does not reflux with the concentrated chamber. The diagram is a determined embodiment, which helps to understand and does not constitute a limitation on the present disclosure.

[0068] In some embodiments, the electrodialysis membrane stack with 2 stages, 2 segments, and 2 chambers is shown in FIG. 6. It is composed of 2 anodes and 1 cathode, and includes cation exchange membranes and anion exchange membranes. And a chamber separated by ion exchange membranes. The diagram is a determined embodiment, which helps to understand and does not constitute a limitation on the present disclosure.

[0069] In some embodiments, the electrodialysis membrane stack with 2 stages, 3 segments, and 4 chambers is shown in FIG. 7. It is composed of 2 anodes and 1 cathode, and includes cation exchange membranes, anion exchange membranes, and bipolar membranes. And a chamber separated by ion exchange membranes. The diagram is a determined embodiment, which helps to understand and does not constitute a limitation on the present disclosure.

[0070] In some embodiments, the electrodialysis membrane stack with 3 stages, 5 segments, and 4 chambers is shown in FIG. 8. It is composed of 2 anodes and 2 cathodes, and includes cation exchange membranes, anion exchange membranes, bipolar membranes, low permeability ion exchange membranes and reverse membranes. And a chamber separated by ion exchange membranes. The low permeability ion exchange membrane is a controllable channel membrane, and the reverse membrane is used as a separation membrane of a segment of the same stage. The diagram is a determined embodiment, which helps to understand and does not constitute a limitation on the present disclosure.

Embodiment 1

An Electrodialysis Method for Selectivity Removal of Hardness

[0071] The hardness of raw water was 600 ppm (in terms of calcium carbonate), and TDS can be 900 ppm. Electrodialysis membranes are used for electrodialysis, the selective separation coefficient of the electrodialysis membrane was 0.8. The stage of the electrodialysis membrane stack was 1 and the segment of the electrodialysis membrane stack was 1. The electrodialysis membrane pairs were 300 pairs, the flow was 6 m/s and the voltage was 45 volts. The electrodialysis membrane had a water yield of 90%, a dense dilute ratio of 1.0; K=[k.sub.liquid.Math.k.sub.field.Math.(k.sub.membrane+k.sub.segment+k.sub.stage)].sup.k.sup.chamber=0.9. The electrodialysis membrane also had an output water hardness of 300 mg/L and TDS 500 ppm. A direct operation cost was 0.05 yuan/ton or less and investment was 1.2 million/ton hours or less. The cleaning cycle of the membrane was half a year, and the membrane life was more than 8 years.

Embodiment 2

An Electrodialysis Method for Selective Defluorination

[0072] The fluoride concentrations of raw water can be 2.0 ppm, the hardness of raw water was 150 ppm (in terms of calcium carbonate), and TDS was 600 ppm. The electrodialysis membranes were used for electrodialysis, the selective separation coefficient of the electrodialysis membrane was 0.3. The stages of the electrodialysis membrane stack were 2 and the segments of the electrodialysis membrane stack were 2. The electrodialysis membrane pairs were 300 pairs. The electrodialysis membranes of segment 1 were compressed diffusion boundary layer membranes 180 pairs in total. The flow rate was 5 m/s and the voltage was 45 volts. The electrodialysis membranes of segment 2 were ion exchange membranes of 120 pairs in total. The flow rate was 7.5 m/s and the voltage was 75 volts. The electrodialysis membrane had a water yield of 97%, a dense dilute ratio of 1.0; K=[k.sub.liquid.Math.k.sub.field.Math.(k.sub.membrane+k.sub.segment+k.sub.stage)].sup.k.sup.chamber=0.5. The electrodialysis membrane also had an output water fluoride concentration of 0.8 ppm, TDS 350 ppm. A direct operation cost was 0.03 yuan/ton or less and investment was 1.2 million/ton hours or less. The cleaning cycle of the membrane was one year, and the membrane life was more than 8 years.

Embodiment 3

An Electrodialysis Method for Selective Decalcification and Defluorination

[0073] The fluoride concentrations of raw water can be 2.0 ppm, the hardness of raw water can be 600 ppm (in terms of calcium carbonate), and TDS can be 950 ppm. Electrodialysis membranes are used for electrodialysis, the selective separation coefficient of the electrodialysis membrane can be 0.3. The stage of the electrodialysis membrane stack should be 2 and the segment of the electrodialysis membrane stack should be 2. The electrodialysis membrane pairs can be 300 pairs. The electrodialysis membranes of segment 1 should be ion exchange membranes 150 pairs in total. The flow rate can be 5 m/s and the voltage can be 65 volts. The electrodialysis membranes of segment 2 should be ion exchange membranes 150 pairs in total. The flow rate can be 5 m/s and the voltage can be 75 volts. The electrodialysis membrane has a water yield of 93%, a dense dilute ratio of 1.0; K=[k.sub.liquid.Math.k.sub.field.Math.(k.sub.membrane+k.sub.segment+k.sub.stage)].sup.k.sup.chamber=0.5. The electrodialysis membrane also has an output water fluoride concentration of 0.8, hardness of 200 ppm (in terms of calcium carbonate), and TDS of 350 ppm. A direct operation cost could be 0.03 yuan/ton or less and investment could be 1.6 million/ton hours or less. A cleaning cycle of the membrane may be one year, and a membrane life may be more than 8 years.

Embodiment 4

An Electrodialysis Method for Selective Removal of Calcium, Fluorine, Sodium, Bicarbonate

[0074] The fluoride concentration of raw water was 2.0 ppm, the hardness of raw water was 600 ppm (in terms of calcium carbonate), and TDS was 1300 ppm. Electrodialysis membranes were used for electrodialysis, the selective separation coefficient of the electrodialysis membrane was 0.3. The stages of the electrodialysis membrane stack were 2 and the segments of the electrodialysis membrane stack were 2. The electrodialysis membrane pairs were 300 pairs. The electrodialysis membranes of segment 1 were ion exchange membranes with 150 pairs in total. The flow rate was 5 m/s and the voltage was 65 volts. The electrodialysis membranes of segment 2 were ion exchange membranes with 150 pairs in total. The flow rate was 5 m/s and the voltage was 75 volts. The electrodialysis membrane has a water yield of 93%, a dense dilute ratio of 1.0; K=[k.sub.liquid.Math.k.sub.field.Math.(k.sub.membrane+k.sub.segment+k.sub.stage)].sup.k.sup.chamber=0.5.

[0075] The electrodialysis membrane also had an output water fluoride concentration of 0.8 ppm, a hardness of 200 ppm (in terms of calcium carbonate), and TDS of 350 ppm. A direct operation cost was 0.03 yuan/ton or less and investment was 1.6 million/ton hours or less. The cleaning cycle of the membrane may be one year, and the membrane life may be more than 8 years.

Embodiment 5

An Electrodialysis Method for Selective Denitrification

[0076] The nitrate concentration of raw water was 400 ppm, and TDS was 950 ppm. The electrodialysis membranes were used for electrodialysis, the selective separation coefficient of the electrodialysis membrane was 0.3. The stage of the electrodialysis membrane stack was 1 and the segments of the electrodialysis membrane stack were 2. The electrodialysis membrane pairs were 300 pairs. The electrodialysis membranes of segment 1 were ion exchange membranes with 150 pairs in total. The flow rate was 5 m/s and the voltage was 55 volts. The electrodialysis membranes of segment 2 were ion exchange membranes with 150 pairs in total. The flow rate was 5 m/s and the voltage was 55 volts. The electrodialysis membrane had a water yield of 97%, a dense dilute ratio of 1.0; K=[k.sub.liquid.Math.k.sub.field.Math.(k.sub.membrane+k.sub.segment+k.sub.stage)].sup.k.sup.chamber=0.5. The electrodialysis membrane also had an output water nitrate concentration of 10 ppm or less. A direct operation cost was 0.03 yuan/ton or less and investment was 1.6 million/ton hours or less. The cleaning cycle of the membrane may be one year, and the membrane life was more than 8 years.

Embodiment 6

An Electrodialysis Method for Selective Arsenic Removal

[0077] The arsenic concentration of raw water was 50.0 ppb, and TDS was 950 ppm. The electrodialysis membranes were used for electrodialysis, the selective separation coefficient of the electrodialysis membrane was 0.3. The stages of the electrodialysis membrane stack were 2, the segments of the electrodialysis membrane stack were 3 and the chambers of the electrodialysis membrane stack were 4. The electrodialysis membrane pairs were 300 pairs. Stage 1 included 1 segment. The segment included 100 cyclic electrodialysis membrane pairs in total, and each cyclic electrodialysis membrane pair included 4 chambers. The chambers were separated by ion exchange membranes, the flow rate was 5 m/s and the voltage was 55 volts. Stage 2 included 2 segments. Segment 1 included 100 cyclic electrodialysis membrane pairs in total, and each cyclic electrodialysis membrane pair included 4 chambers. The chambers were separated by ion exchange membranes, the flow rate was 5 m/s and the voltage was 55 volts. Segment 2 included electrodialysis membrane pairs, and each cyclic electrodialysis membrane pair included 2 or 4 chambers. When the number of chambers was 2, the cyclic electrodialysis membrane pairs were common membrane pairs, the common membrane pairs were separated by the ion exchange membrane. When the number of chambers was 4, the cyclic electrodialysis membrane pairs were special membrane pairs. The special membrane pairs were divided into 2 chambers by the ion exchange membranes and then divided into 2 chambers by the bipolar membranes. The number of chambers divided by the bipolar membrane accounted for 10% of the total chamber number. The electrodialysis membrane had a water yield of 93%, a dense dilute ratio of 0.3-1.0; K=[k.sub.liquid.Math.k.sub.field.Math.(k.sub.membrane+k.sub.segment+k.sub.stage)].sup.k.sup.chamber=0.5. The electrodialysis membrane also had an output water fluoride concentration of 0.8 ppm, a hardness of 200 ppm (in terms of calcium carbonate), and a TDS of 350 ppm. A direct operation cost was 0.03 yuan/ton or less and investment was 1.6 million/ton hours or less. A cleaning cycle of the membrane was one year, and the membrane life was more than 8 years.

Embodiment 7

An Electrodialysis Method for Selective High Concentration Boron Removal

[0078] The arsenic concentration of raw water was 10.0 ppm, and TDS was 45000 ppm. Ion exchange membranes were used for the electrodialysis. The stages of the electrodialysis membrane stack were 3, the segments of the electrodialysis membrane stack were 5 and the chambers of the electrodialysis membrane stack were 4. The electrodialysis membrane pairs were 300 pairs and each segment included 60 pairs. Stage 1 included 2 segments. Each cyclic electrodialysis membrane pair included 2 chambers. The chambers were separated by controllable channel membranes, the flow rate was 0.5 m/s and the constant current was 2 A. Stage 2 included 2 segments. Each segment included cyclic electrodialysis membrane pair and each cyclic electrodialysis membrane pair included 4 chambers. The chambers were separated by controllable channel membranes, the flow rate was 0.5 m/s and the constant current was 1.3 A. Stage 3 includes 1 segment. The segment included electrodialysis membrane pairs, and each cyclic electrodialysis membrane pair included 2 or 4 chambers. When the number of chambers was 2, the cyclic electrodialysis membrane pairs were common membrane pairs, the common membrane pairs were separated by the ion exchange membrane. When the number of chambers is 4, the cyclic electrodialysis membrane pairs were special membrane pairs. The special membrane pairs were divided into 2 chambers by the ion exchange membrane and then divided into 2 chambers by the bipolar membrane. The number of chambers divided by the bipolar membrane accounted for 3-10% of the total chamber number. This stage had a constant pressure of 0.5 volts. This stage also had an output water boron concentration of 4.5 ppm or less, TDS 500 ppm or less. A direct operation cost could be 0.03 yuan/ton or less and investment was 1.6 million/ton hours or less. A cleaning cycle of the membrane was one year, and the membrane life was more than 8 years. The selective separation coefficient of the electrodialysis membrane was 0.9. A direct operation cost was 0.05 yuan/ton or less and investment was 1.2 million/ton hours or less. The cleaning cycle of the membrane was half a year, and the membrane life was more than 8 years.

Embodiment 8

An Electrodialysis Method for Selective Defluorination

[0079] Respectively added a respective corresponding solution into each water tank of the device. A sodium sulfate solution with a concentration of 2 L of 0.1 mol/L was added into the polar chamber water tank, and the concentration chamber water tank and the desalination chamber water tank were introduced into a simulated underground water solution 5L having the same concentration. Sodium chloride and sodium fluoride were used as research objects, the sodium chloride concentration was set to 500 ppm, and the sodium fluoride concentration was set to 2 ppm, respectively.

[0080] Then, the circulating pump corresponding to each water tank was turned on, that is, the circulation pumps provided on conduits connecting each tank to the corresponding compartments in the membrane stack were opened. The corresponding circulating flow rate was adjusted, and the flow rate of the solution in each water tank was controlled to be 6 L/h.

[0081] Then, a direct current power supply was turned on (the negative electrode of the power supply was connected to the cathode of the membrane stack, and the positive electrode of the power supply was connected to the anode of the membrane stack. FIG. 1). It was in a constant voltage state, the voltage was controlled to be 10 V.

[0082] The membrane stack used in this embodiment was composed of 3 groups of ion exchange membranes. Each group had 9 ion exchange membranes (electrode membranes, anion exchange membranes, and cation exchange membranes). The effective area of each membrane was 110 mm×270 mm=29700 mm.sup.2.

[0083] During operation, the conductivity analysis instrument was used to measure the conductivity in the concentration chamber water tank in real-time. When conductivity was observed to be stable, it is considered that the reaction was ended. Then processing was stopped, and the power supply was turned off.

Embodiment 9

An Electrodialysis Method for Selective Defluorination

[0084] Compared with embodiment 8, this embodiment differs only in that the concentration of sodium fluoride was set to 4 ppm, respectively.

Embodiment 10

An Electrodialysis Method for Selective Defluorination

[0085] Compared with embodiment 8, this embodiment differs only in that the concentration of sodium fluoride was set to 6 ppm, respectively.

Embodiment 11

An Electrodialysis Method for Selective Defluorination

[0086] Compared with embodiment 8, this embodiment differs only in that the concentration of sodium fluoride was set to 8 ppm, respectively.

Embodiment 12

[0087] An electrodialysis method for selective defluorination

[0088] Compared with embodiment 8, this embodiment differs only in that the concentration of sodium fluoride was set to 10 ppm, respectively.

Embodiment 13

An Electrodialysis Method for Selective Defluorination

[0089] This embodiment differs from Example 8 only in the following aspects:

[0090] The concentration of sodium fluoride was set to 3 ppm, respectively; the electric field intensity was 5V, and the water inlet flow rate was 12 L/h.

Embodiment 14

An Electrodialysis Method for Selective Defluorination

[0091] This embodiment differs from Example 8 only in the following aspects:

[0092] The concentration of sodium fluoride was set to 3 ppm, respectively; the electric field intensity was 10 V, and the water inlet flow rate was 12 L/h.

Embodiment 15

An Electrodialysis Method for Selective Defluorination

[0093] This embodiment differs from Example 8 only in the following aspects:

[0094] The concentration of sodium fluoride was set to 3 ppm, respectively; the electric field intensity was 15 V, and the water inlet flow rate was 12 L/h.

Embodiment 16

An Electrodialysis Method for Selective Defluorination

[0095] This embodiment differs from Example 8 only in the following aspects:

[0096] The concentration of sodium fluoride was set to 3 ppm, respectively; the electric field intensity was 20 V, and the water inlet flow rate was 12 L/h.

Embodiment 17

[0097] An electrodialysis method for selective defluorination

[0098] This embodiment differs from Example 8 only in the following aspects:

[0099] The concentration of sodium fluoride was set to 3 ppm, respectively; the electric field intensity was 25 V, and the water inlet flow rate was 12 L/h.

Embodiment 18

An Electrodialysis Method for Selective Defluorination

[0100] This embodiment differs from Example 8 only in the following aspects:

[0101] The concentration of sodium fluoride was set to 3 ppm, respectively; the electric field intensity was 30 V, and the water inlet flow rate was 12 L/h.

Embodiment 19

An Electrodialysis Method for Selective Defluorination

[0102] This embodiment differs from Example 8 only in the following aspects:

[0103] The concentration of sodium fluoride was set to 3 ppm, respectively; the electric field intensity was 15 V, and the water inlet flow rate was 6 L/h.

Embodiment 20

An Electrodialysis Method for Selective Defluorination

[0104] This embodiment differs from Example 8 only in the following aspects:

[0105] The concentration of sodium fluoride was set to 3 ppm, respectively; the electric field intensity was 15 V, and the water inlet flow rate was 12 L/h.

Embodiment 21

An Electrodialysis Method for Selective Defluorination

[0106] This embodiment differs from Example 8 only in the following aspects:

[0107] The concentration of sodium fluoride was set to 3 ppm, respectively; the electric field intensity was 15 V, and the water inlet flow rate was 18 L/h.

Embodiment 22

An Electrodialysis Method for Selective Defluorination

[0108] This embodiment differs from Example 8 only in the following aspects:

[0109] The concentration of sodium fluoride was set to 3 ppm, respectively; the electric field intensity was 15 V, and the water inlet flow rate was 24 L/h.

Embodiment 23

An Electrodialysis Method for Selective Defluorination

[0110] This embodiment differs from Example 8 only in the following aspects:

[0111] The concentration of sodium fluoride was set to 3 ppm, respectively; the electric field intensity was 15 V, and the water inlet flow rate was 30 L/h.

Test Example

1. Effect of Different Initial Fluorine Concentrations on Defluorination

[0112] The concentrations of sodium fluoride and sodium chloride in the desalination chamber water tank in Examples 8-12 were analyzed and determined respectively.

[0113] The fluorine ion selective separation efficiency in electrodialysis is calculated according to the following formula:

[00004]$S_B^A=\frac{C_{A\left(t\right)}/C_{A\left(0\right)}-C_{B\left(t\right)}/C_{B\left(0\right)}}{\left(1-C_{A\left(t\right)}/C_{A\left(0\right)}\right)+\left(1-C_{B\left(t\right)}/C_{B\left(0\right)}\right)};$

wherein, C.sub.A(t) is the ion concentration of A ion at time t; C.sub.A(0) is the initial ion concentration of A ion; C.sub.B(t) is the ion concentration of B ion at time t; C.sub.B(0) is the ion concentration of B ion. The S value range is −1 to 1 depending on the mass transfer rate of the fluoride and chloride ions. If the A ion mass transfer rate is higher than B ions, the S value is between −1 and 0; otherwise, the S value is between 0 and 1.

[0114] The concentration of sodium chloride and sodium fluoride in the desalination chamber water tank was analyzed by using an ion chromatograph, and the determination result is shown in Table 1.

TABLE-US-00001 TABLE 1 Ion Concentration of the Treated Water after Guided Electrodialysis Based on Different Initial Concentrations. Embodiment Embodiment Embodiment Embodiment Embodiment 8 9 10 11 12 After processing 28.1 21.5 21.8 22.8 30.6 C.sub.(NaCl)/ppm After processing 0.26 0.36 0.45 0.57 0.69 C.sub.(NaF)/ppm Selective separation 0.157 0.182 0.207 0.216 0.227 coefficient

[0115] The selective separation effect of fluorine ions in electrodialysis is shown in Table 2. The concentration of fluorine ions and chloride ions in each group of water samples can reach the standard of the drinking water specified by the World Health Organization (WHO). Improving the initial fluoride ion concentration can slightly improve the selectivity separation efficiency of the fluorine ions. After analyzing the resistance of the diffusion boundary layer on the surface of the ion exchange membrane, it is found that when the ion concentration is low, the diffusion boundary layer resistor RDBL is the main control factor of the film resistor. However, the influence of the concentration change of 2 -10 ppm on RDBL is relatively weak, so that the fluorine ion selective separation efficiency is not obvious with the concentration change.

2. Effect of Different Voltage on Defluorination

[0116] The results of the measurement in embodiment 13-18 are shown in Table 2.

TABLE-US-00002 TABLE 2 Ion Concentration of the Treated Water after Guided Electrodialysis Based on Different Electric Fields. Embodiment 13 Embodiment 14 Embodiment 15 Embodiment 16 Embodiment 17 Embodiment 18 After processing 56.5 20.6 25.5 7.44 5.36 5.07 C.sub.(NaCl)/ppm After processing 0.61 0.53 0.43 0.1 0.08 0.08 C.sub.(NaF)/ppm Selective 0.062 0.129 0.172 0.261 0.283 0.358 separation coefficient

[0117] The selective separation effect of fluorine ions in electrodialysis is shown in Table 2.The concentration of fluorine ions and chloride ions in each group of water samples can reach the standard of the drinking water specified by the World Health Organization (WHO). Improving the intensity of the external electric field can improve the selectivity separation efficiency of the fluorine ions. After analyzing the resistance of the diffusion boundary layer on the surface of the ion exchange membrane, it is found that increasing the electric field intensity can decrease the thickness of the DBL, and the RDBL is greatly reduced. So the fluorine ion selective separation efficiency is obviously improved.

3. Effect of Different Water Inlet Flow Rates on Defluorination

[0118] The results of the measurement in embodiment 19-23 are shown in Table 3.

TABLE-US-00003 TABLE 3 Ion Concentration of the Treated Water after Guided Electrodialysis Based on Different Electric fields. Embodiment Embodiment Embodiment Embodiment Embodiment 19 20 21 22 23 After processing 33.5 26.1 14.5 7.62 5.27 C.sub.(NaCl)/ppm After processing 0.44 0.23 0.14 0.09 0.06 C.sub.(NaF)/ppm Selective separation 0.106 0.172 0.208 0.282 0.379 coefficient

[0119] The selective separation effect of fluorine ions in electrodialysis is shown in Table 3. The concentration of fluorine ions and chloride ions in each group of water samples can reach the standard of the drinking water specified by the World Health Organization (WHO). Improving the water inlet flow rate can improve the selectivity separation efficiency of the fluorine ions. After analyzing the resistance of the diffusion boundary layer on the surface of the ion exchange membrane, it is found that increasing the water inlet flow rate can decrease the thickness of the DBL, and the RDBL is greatly reduced. So the fluorine ion selective separation efficiency is obviously improved.

[0120] The multi-parameter controlled guided defluorination electrodialysis of the present disclosure is applied to a drinking water treatment process, which not only can achieve the standard that the ion components in drinking water meet the specification of WHO, but also can realize competitive migration and separation of fluorine ions in an aqueous solution.

[0121] The above embodiments are merely intended to illustrate the present disclosure and are not intended to limit the present disclosure. Various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the present disclosure. Therefore, all equivalent technical solutions fall within the scope of the present invention.