Nanoparticle enhanced electrochemical water softening treatment method

Abstract

The invention relates to a nanoparticle enhanced electrochemical water softening treatment method. In the water softening treatment method provided by the invention, the nanoparticles move towards the cathode under the action of an electric field, and the water softening effect is enhanced through synergistic effects of providing nucleation sites and the like for CaCO3 and Mg (OH) 2 in a cathode region through an adsorption effect. After electrochemical treatment is carried out for 60 minutes in cooling water added with 100 mg / L of nano TiO2, the total hardness in simulated water is reduced to 139 mg CaCO3 / L from 375 mg CaCO3 / L, and the softening efficiency is 62.9%; and the electrochemical softening efficiency in simulated water without nano particles is 35.2%. And the softening efficiency is improved by 27.7% through combined treatment of nanoparticles and electrochemistry. Compared with the prior art, the method has the advantages that hardness ions in water are effectively removed, nano particles can become crystal nucleuses of scale forming substances, the scale forming process is promoted to be carried out in the solution, and therefore the scale forming substances are inhibited from being attached to the surface of the cathode, the electrolysis efficiency is effectively guaranteed, and no extra chemical agent needs to be added. The method is simple to operate, low in treatment cost and environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a nanoparticle-enhanced electrochemical water softening treatment method. Background Technology

[0002] Circulating cooling water is used in many industrial production processes, typically accounting for over 70% of industrial water consumption. To conserve water resources, freshwater cooling water needs to be recycled. Circulating cooling water systems present several problems during operation, such as excessively hard water leading to scaling on heated surfaces; high nutrient levels and suitable temperatures within the system causing microbial accumulation and corrosion of equipment; and increasing salt concentration due to the gradual concentration of circulating water, resulting in corrosion of cooling pipes. Scale buildup on the inner walls of heat exchange tubes can cause blockages, hindering the flow of circulating cooling water, increasing resistance, reducing system efficiency, and increasing heat transfer resistance on the heat exchanger tube walls, leading to increased energy consumption. Corrosion reduces equipment lifespan and affects safe operation. Furthermore, the growth of microorganisms in the circulating water system not only forms biological slime on the heat exchanger tube surface, affecting heat exchange performance, but also causes microbial corrosion of metals.

[0003] Currently, the common method for circulating water treatment is to add scale and corrosion inhibitors and bactericides. However, adding these agents can cause secondary pollution to the environment and has limited effect on increasing the concentration ratio, failing to meet the requirements for zero discharge. Electrochemical water softening technology is considered a promising green water treatment method due to its environmental friendliness, ease of operation, and ability to significantly improve the system concentration ratio. This technology mainly removes hardness ions through the electrolysis of water. At the cathode, a hydrogen evolution reaction occurs, producing a strongly alkaline water environment. At the anode, H₂O and Cl₂ are mainly produced. - The oxidation process produces strong oxidizing substances, which can effectively inhibit the reproduction of microorganisms in the water.

[0004] The main problems currently existing in the application of electrochemical water softening treatment are the low water softening efficiency of traditional electrolyzers and the high alkalinity environment in the cathode area, which promotes the deposition of more scale-forming substances on the cathode surface, leading to cathode deactivation and further reducing water softening efficiency. Therefore, improving electrolytic softening efficiency and inhibiting scale formation on the cathode surface are of great significance for the widespread application of electrochemical water softening treatment technology.

[0005] Patent publication number CN101423270A discloses a high-efficiency electrocatalytic advanced oxidation technology electrode material, including a nanofunctional anode material composed of composite nano-oxide particles and catalytic metal nanoparticles on a titanium substrate, and a nanofunctional cathode material using titanium or stainless steel as a substrate and introducing transition metal nanoparticles on its surface. However, it mainly increases the electrode specific surface area through surface nano-modification to generate more strong oxidizing substances to improve electrochemical sterilization and disinfection capabilities, without involving electrochemical water softening.

[0006] Patent publication number CN114105320A discloses a method for inhibiting scale formation on electrode surfaces by inducing liquid-phase nucleation of scale-forming substances using nano- and microbubbles. The nano-tipped porous electrode can generate a large number of nano- and microbubbles, which play a dual role: serving as both nucleation sites and transport carriers for scale. This method simultaneously softens water using electrochemical methods and inhibits scale formation on the electrode surface, thus ensuring the continuous progress of the electrochemical reaction. While this method has some effectiveness, its implementation depends on the preparation of special electrodes, resulting in a complex process and high cost. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art by providing a nanoparticle-enhanced electrochemical water softening treatment method, which can effectively improve the softening efficiency of electrochemical water softening treatment, and is low in cost and simple in process.

[0008] The objective of this invention can be achieved through the following technical solutions: A nanoparticle-enhanced electrochemical water softening treatment method involves adding nanoparticles to water to be treated and then performing electrochemical water softening treatment on the water containing the nanoparticles.

[0009] Furthermore, the nanoparticles are able to migrate toward the anode during the electrochemical water softening process.

[0010] Furthermore, the nanoparticles have a positively charged surface.

[0011] Furthermore, the nanoparticles are nano-metal oxides.

[0012] Furthermore, the nano-metal oxide is selected from at least one of nano-alumina, nano-silica, or nano-titanium dioxide, preferably nano-titanium dioxide.

[0013] Furthermore, the particle size of the nanoparticles is 10~80 nm. Furthermore, the concentration of the nanoparticles in the water to be treated is 5~200 mg / L.

[0014] Furthermore, the nanoparticles are dispersed in the water to be treated by ultrasonication.

[0015] Furthermore, the ultrasonic dispersion frequency is 40~50 kHz, and the duration is 40~50 min.

[0016] Furthermore, the current density of the electrochemical water softening treatment is 20~65 A / m. 2 .

[0017] Furthermore, the total hardness of the water to be treated is 10~600 mg CaCO3 / L, the alkalinity is 20~1000 mg CaCO3 / L, and the pH is 6.5~10.0.

[0018] Furthermore, the water to be treated contains cations and anions, the cations including calcium ions and magnesium ions, and the anions including sulfate ions, chloride ions, or bicarbonate ions or one or more.

[0019] Furthermore, the cation also includes sodium ions.

[0020] Furthermore, the water to be treated contains one or more of magnesium sulfate (MgSO4), sodium sulfate (Na2SO4), calcium chloride (CaCl2), sodium chloride (NaCl), or sodium bicarbonate (NaHCO3).

[0021] Furthermore, the electrochemical water softening process is carried out in an electrochemical device, which includes a cathode and an anode.

[0022] Furthermore, the cathode is a plate-shaped electrode, and the anode is a mesh-shaped electrode.

[0023] Furthermore, the plate-shaped electrode is made of stainless steel, and the mesh electrode is made of at least one of titanium, iridium, and ruthenium.

[0024] Furthermore, under laboratory conditions, the distance between the cathode and anode is 5–15 mm. In engineering applications, the distance can be increased to 20–200 mm depending on the electrode size.

[0025] Compared with the prior art, the present invention has the following advantages: (1) This invention significantly improves the hardness removal effect and maintains the stable operation of the treatment system by introducing nanoparticles into the water to be treated and combining them with electrochemical treatment. Its core mechanism is that under the action of an electric field, nanoparticles (especially positively charged nanoparticles) can migrate directionally towards the cathode, thereby greatly increasing the probability of contact and collision with scale-forming ions such as calcium and magnesium in the water. At the same time, the porous structure of the nanoparticles can adsorb these hardness ions and serve as preferential nucleation sites for crystals such as CaCO3 and Mg(OH)2, promoting the formation and enrichment of scale substances in the bulk solution rather than deposition on the cathode surface. This synergistic effect of "electromigration-adsorption-induced nucleation" is the key to improving the overall hardness removal efficiency.

[0026] (2) Because scaling on the cathode surface is effectively suppressed, electrode activity is maintained for a long time, resulting in stable current efficiency of the electrochemical process and continuous stable anode side reactions. This also promotes the formation of hypochlorite (ClO) ions. - The generation of active substances such as [unspecified substances] ensures that a good bactericidal and disinfecting effect is maintained simultaneously during the softening process.

[0027] (3) No chemical agents need to be added during the entire process of this method, which avoids the problem of secondary water pollution that may be caused by the introduction of external agents. It is environmentally friendly and suitable for various scenarios that require water softening treatment, such as industrial circulating cooling water and central air conditioning water.

[0028] (4) This invention does not require modification of existing electrochemical treatment device hardware. It directly adds nanoparticles to water to transfer scale deposits from the electrode surface to the aqueous solution, which has low implementation threshold and low modification cost. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the electrochemical water softening treatment device used in this invention; Figure 2 The graph shows the changes in total hardness (a) and calcium hardness (b) of the electrolysis, electrolysis + 100 mg / L nano Al2O3, electrolysis + 100 mg / L nano SiO2, electrolysis + 50 mg / L nano TiO2, and electrolysis + 100 mg / L nano TiO2 treatments for different times in this invention. Figure 3 The graph shows the changes in total hardness (a) and calcium hardness (b) at different times after electrolytic treatment with +0~100 mg / L nano Al2O3 in this invention; Figure 4 The graph shows the changes in total hardness (a) and calcium hardness (b) at different times after electrolytic treatment with 0~100 mg / L nano SiO2 in this invention. Figure 5The graph shows the changes in total hardness (a) and calcium hardness (b) at different times after electrolytic treatment with 0~100 mg / L nano TiO2 in this invention.

[0030] Explanation of markings in the diagram: 1-Cathode, 2-Anode, 3-Barrier mesh. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. All other embodiments obtained by those skilled in the art based on the given embodiments without creative effort are within the scope of protection of this application.

[0032] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. The sources and particle size parameters of the nano-alumina, nano-silica, or nano-titanium dioxide used in this invention are shown in Table 1.

[0033] Table 1. Sources and parameters of commercially available nano-alumina, nano-silica, or nano-titanium dioxide.

[0034] A nanoparticle-enhanced electrochemical water softening treatment method involves adding nanoparticles to water to be treated and then performing electrochemical water softening treatment on the water containing the nanoparticles.

[0035] In some specific embodiments, the nanoparticles are able to migrate toward the anode 2 during the electrochemical water softening process.

[0036] In some specific embodiments, the nanoparticles have a positively charged surface.

[0037] In some specific embodiments, the nanoparticles are nano-metal oxides.

[0038] In some specific embodiments, the nano-metal oxide is selected from at least one of nano-alumina, nano-silica, or nano-titanium dioxide, preferably nano-titanium dioxide.

[0039] In some specific embodiments, the nanoparticles have a particle size of 10~80 nm. In some specific embodiments, the concentration of the nanoparticles in the water to be treated is 5~200 mg / L.

[0040] In some specific embodiments, the nanoparticles are dispersed in the water to be treated by ultrasonication.

[0041] In some specific embodiments, the ultrasonic dispersion frequency is 40-50 kHz and the duration is 40-50 min.

[0042] In some specific embodiments, the current density of the electrochemical water softening treatment is 20~65 A / m. 2 .

[0043] In some specific embodiments, the water to be treated contains cations and anions, the cations including calcium ions and magnesium ions, and the anions including sulfate ions, chloride ions, or bicarbonate ions or one or more.

[0044] In some specific embodiments, the total hardness of the water to be treated is 10~600 mg CaCO3 / L, the alkalinity is 20~1000 mg CaCO3 / L, and the pH is 6.5~10.0.

[0045] In some specific embodiments, the cation also includes sodium ions.

[0046] In some specific embodiments, the water to be treated contains one or more of MgSO4, Na2SO4, CaCl2, NaCl, or NaHCO3.

[0047] In some specific embodiments, the electrochemical water softening process is carried out in an electrochemical device, which includes a cathode 1 and an anode 2.

[0048] In some specific embodiments, the cathode 1 is a plate electrode and the anode 2 is a mesh electrode.

[0049] In some specific embodiments, the plate electrode is made of stainless steel, and the mesh electrode is made of at least one of titanium, iridium, and ruthenium.

[0050] In some specific embodiments, under laboratory conditions, the distance between the cathode 1 and the anode 2 is 5-15 mm. In engineering applications, the distance can be increased to 20-200 mm depending on the size of the electrodes.

[0051] Each of the above embodiments can be implemented individually or in any combination of two or more.

[0052] The following description uses specific examples to illustrate the point.

[0053] Example 1 A nanoparticle-enhanced electrochemical water softening treatment method involves adding nano-alumina to simulated cooling water and ultrasonically dispersing it at 45 kHz for 45 min to ensure uniform dispersion. The concentration of nano-alumina is 100 mg / L. The simulated cooling water containing 100 mg / L nano-alumina is then subjected to electrochemical water softening treatment in an electrochemical device.

[0054] The electrochemical device includes a cathode 1, an anode 2, and a barrier layer 3. The cathode 1 is a stainless steel plate electrode, the anode 2 is a titanium-iridium-ruthenium mesh electrode, and the barrier layer 3 can be an activated carbon membrane. A detailed diagram of the electrochemical treatment device is shown below. Figure 1 As shown. The water to be treated used simulated cooling water, with hardness provided by MgSO4 and CaCl2, resulting in a total hardness of 375 mg CaCO3 / L, of which Mg hardness was 125 mg CaCO3 / L and Ca hardness was 250 mg CaCO3 / L; alkalinity was 1000 mg CaCO3 / L, provided by NaHCO3; the pH of the prepared simulated cooling water was 8.40. Figure 1 An electrochemical water softening experiment was conducted using the apparatus shown. The pressure was 60 A / cm². 2 The current density was used to perform constant current electrochemical treatment on the simulated cooling water, and the treatment time was controlled to be up to 60 minutes. The water volume in the electrochemical treatment device was 1L.

[0055] Example 2 It is largely the same as Example 1, except that nano-alumina is replaced with nano-silica.

[0056] Example 3 It is largely the same as Example 1, except that nano-alumina is replaced with nano-titanium dioxide.

[0057] Example 4 The majority of the components are the same as in Example 1, except that the 100 mg / L nano alumina is changed to 50 mg / L nano titanium dioxide.

[0058] Example 5 It is largely the same as Example 1, except that the concentration of nano-alumina was changed from 100 mg / L to 10 mg / L.

[0059] Example 6 The majority of the components are the same as in Example 1, except that the concentration of nano-alumina was changed from 100 mg / L to 30 mg / L.

[0060] Example 7 It is largely the same as Example 1, except that the concentration of nano-alumina was changed from 100 mg / L to 50 mg / L.

[0061] Example 8 It is largely the same as Example 1, except that the concentration of nano-alumina was changed from 100 mg / L to 75 mg / L.

[0062] Example 9 The majority of the components are the same as in Example 2, except that the concentration of nano-silica was changed from 100 mg / L to 10 mg / L.

[0063] Example 10 The majority of the components are the same as in Example 2, except that the concentration of nano-silica was changed from 100 mg / L to 30 mg / L.

[0064] Example 11 The majority of the components are the same as in Example 2, except that the concentration of nano-silica was changed from 100 mg / L to 50 mg / L.

[0065] Example 12 The majority of the components are the same as in Example 2, except that the concentration of nano-silica was changed from 100 mg / L to 75 mg / L.

[0066] Example 13 The majority of the components are the same as in Example 3, except that the concentration of nano titanium dioxide was changed from 100 mg / L to 10 mg / L.

[0067] Example 14 The majority of the components are the same as in Example 3, except that the concentration of nano titanium dioxide was changed from 100 mg / L to 30 mg / L.

[0068] Example 15 The majority of the components are the same as in Example 3, except that the concentration of nano titanium dioxide was changed from 100 mg / L to 50 mg / L.

[0069] Example 16 The majority of the components are the same as in Example 3, except that the concentration of nano titanium dioxide was changed from 100 mg / L to 75 mg / L.

[0070] Comparative Example 1 Compared to Example 1, everything else is the same except that nano-alumina is not added.

[0071] Performance testing: I. The Influence of Different Types of Nanoparticles The electrochemical treatment results after adding different types of nanoparticles (Examples 1-4, Comparative Example 1) to simulated cooling water are as follows: Figure 2 As shown, the total hardness of the nano-Al2O3 system decreased from 375 mg CaCO3 / L to 186 mg CaCO3 / L, the total hardness of the nano-SiO2 system decreased from 375 mg CaCO3 / L to 215 mg CaCO3 / L, and the total hardness of the nano-TiO2 system decreased from 375 mg CaCO3 / L to 139 mg CaCO3 / L. The electrochemical softening efficiencies of the three nanoparticles in the cooling water were 50.4%, 42.6%, and 62.9%, respectively, while the electrochemical softening efficiency of the cooling water without nanoparticles was 35.2%. The combined treatment of nano-Al2O3, nano-SiO2, nano-TiO2, and electrochemical treatment increased the softening efficiency by 15.2, 7.4, and 27.7 percentage points, respectively. Therefore, the combined treatment method of this invention effectively improves the hardness removal rate of simulated water. The different hardness removal properties of nanoparticles may be mainly related to their particle size and porosity; for example, the smaller the particle size, the better the hardness removal effect.

[0072] II. Effects of different concentrations of nano-Al2O3 The effects of adding different concentrations of nano-Al2O3 to simulated cooling water and combining it with electrochemical treatment on hardness removal were investigated, and the results are as follows: Figure 3 As shown. Nano-Al₂O₃ at concentrations of 0, 10, 30, 50, 75, and 100 mg / L (Examples 1, 5-12, and Comparative Example 1) was added to simulated water. The total hardness and calcium hardness content in the water were measured sequentially at 10, 30, 45, and 60 mins after the start of electrochemical treatment. The current density during the electrochemical treatment process was 60 A / m². 2 The average particle size of nano-Al2O3 is 25 nm.

[0073] Depend on Figure 3 It can be seen that when nano-Al2O3 is added to simulated water and combined with electrochemical treatment, the total hardness and calcium hardness in the simulated water gradually decrease with the increase of nano-Al2O3 concentration. After 60 minutes of treatment with simulated water containing 100 mg / L nano-Al2O3, the total hardness decreased from 375 mg CaCO3 / L to 186 mg CaCO3 / L, and the hardness removal rate was 50.40%.

[0074] III. Effects of Different Concentrations of Nano-SiO2 The effects of adding different concentrations of nano-SiO2 to simulated cooling water and combining it with electrochemical treatment on hardness removal were investigated, and the results are as follows: Figure 4 As shown. Nano-SiO2 was added to simulated water at concentrations of 0, 10, 30, 50, 75, and 100 mg / L (Examples 2, 9-8, and Comparative Example 1). The total hardness and calcium hardness content in the water were measured sequentially at 10, 30, 45, and 60 min after the start of electrochemical treatment. The current density during the electrochemical treatment process was 60 A / m.2 The average particle size of nano-SiO2 is 30 nm.

[0075] Depend on Figure 4 It can be seen that the total hardness and calcium hardness content in the simulated water gradually decreased with the increase of electrochemical treatment time. The water softening pattern with the increase of nano SiO2 concentration was basically consistent with that of nano Al2O3. Overall, the hardness removal effect of the simulated water with nano SiO2 after electrochemical treatment was slightly higher than that of the simulated water without nanoparticles. For cooling water with 100 mg / L nano SiO2 added, the total hardness decreased from 375 mg CaCO3 / L to 215 mg CaCO3 / L after 60 minutes of electrochemical treatment, and the hardness removal rate was 42.67%, which was lower than that of the electrochemical + nano Al2O3 system.

[0076] IV. Effects of Different Concentrations of Nano-TiO2 The effects of adding different concentrations of nano-TiO2 to simulated cooling water and combining it with electrochemical treatment on hardness removal were investigated, and the results are as follows: Figure 5 As shown, nano-TiO2 at concentrations of 0, 10, 30, 50, 75, and 100 mg / L (Examples 3, 13-16, and Comparative Example 1) was added to simulated water. The total hardness and calcium hardness content in the water were measured sequentially at 10, 30, 45, and 60 min after the start of electrochemical treatment. The current density during the electrochemical treatment process was 60 A / m. 2 The average particle size of nano-TiO2 is 20 nm.

[0077] The results are as follows Figure 5 As shown, the change in hardness content in simulated water with electrochemical treatment time follows the same pattern as the other two types of nanoparticles. A "threshold" effect appears at concentration. When simulated water with added nano-TiO2 concentrations of 10-50 mg / L is electrochemically treated for the same treatment time, the hardness decreases with increasing nano-TiO2 concentration. Further increasing the nano-TiO2 concentration, however, causes the hardness to increase. This indicates that adding an appropriate concentration of nano-TiO2 to simulated water can achieve a better synergistic softening effect with electrochemical treatment, while excessively high nano-TiO2 concentrations inhibit this synergistic softening effect. Electrochemical treatment with 50 mg / L nano-TiO2 for 60 minutes in simulated water achieves a hardness removal rate of 62.94%. Therefore, the combined effect of 50 mg / L nano-TiO2 and electrochemical treatment for softening simulated water is relatively strong.

[0078] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A nanoparticle-enhanced electrochemical water softening treatment method, characterized in that, Nanoparticles are added to the water to be treated, and the water containing the nanoparticles is subjected to electrochemical water softening treatment.

2. The nanoparticle-enhanced electrochemical water softening treatment method according to claim 1, characterized in that, The nanoparticles are able to migrate toward the anode during the electrochemical water softening process.

3. A nanoparticle-enhanced electrochemical water softening treatment method according to claim 1 or 2, characterized in that, The nanoparticles have a positive charge on their surface.

4. The nanoparticle-enhanced electrochemical water softening treatment method according to claim 1, characterized in that, The nanoparticles are nano-metal oxides.

5. The nanoparticle-enhanced electrochemical water softening treatment method according to claim 4, characterized in that, The nano-metal oxide is selected from at least one of nano-alumina, nano-silica, or nano-titanium dioxide.

6. The nanoparticle-enhanced electrochemical water softening treatment method according to claim 1, characterized in that, The nanoparticles have a particle size of 10~80 nm.

7. The nanoparticle-enhanced electrochemical water softening treatment method according to claim 1, characterized in that, The concentration of the nanoparticles in the water to be treated is 5~200 mg / L.

8. The nanoparticle-enhanced electrochemical water softening treatment method according to claim 1, characterized in that, The current density of the electrochemical water softening treatment is 20~65A / m. 2 .

9. The nanoparticle-enhanced electrochemical water softening treatment method according to claim 1, characterized in that, The water to be treated contains cations and anions. The cations include calcium ions and magnesium ions, and the anions include sulfate ions, chloride ions, or one or more bicarbonate ions.

10. The nanoparticle-enhanced electrochemical water softening treatment method according to claim 9, characterized in that, The total hardness of the water to be treated is 10~600 mg CaCO3 / L, the alkalinity is 20~1000 mg CaCO3 / L, and the pH is 6.5~10.0.

Images