A method for deep treatment of high-salinity industrial wastewater

Abstract

This invention relates to the field of industrial wastewater treatment technology, and particularly to a method for the deep treatment of high-salinity industrial wastewater, comprising the following steps: designing a single electrolytic cell, using a DSA electrode as the anode and a Cu / Fe electrode as the cathode, and placing an ultraviolet lamp; turning on the power supply to the single electrolytic cell, and controlling the current density in the anode and cathode cells to be 5-35 mA / cm². 2 The reaction proceeds for 1-2 hours; then the UV lamp is turned on to continue the degradation reaction without changing the current density of the original electrode, and the reaction continues for 3 hours until the recalcitrant organic matter can no longer be degraded; the UV lamp is then turned off, and the reaction continues until nitrate nitrogen is completely removed, at which point TN is also efficiently removed. This invention achieves the electrochemical reaction through a Cu / Fe electrode design. After the nitrate has completely reacted, the UV lamp is turned on to enhance the generation of ClO free radicals, completely mineralizing the recalcitrant organic matter and converting organic nitrogen into inorganic nitrogen. The UV lamp is then turned off, and the reaction continues until TN is reduced to a minimum, ultimately achieving synergistic removal of TOC and TN.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, and in particular to a method for deep treatment of high-salinity industrial wastewater. Background Technology

[0002] Industrial wastewater production processes generate large quantities of toxic and recalcitrant organic wastewater, and biological treatment aims to remove total organic carbon (TOC) and total nitrogen (TN). However, even after conventional secondary biological treatment, the effluent still contains a large amount of toxic, harmful, and recalcitrant organic pollutants, with high levels of suspended solids, color, and salinity. TOC and TN remain prevalent in the biologically treated effluent of industrial wastewater, causing the treated wastewater to fail to meet industrial wastewater discharge standards and thus posing a serious threat to the environment. Data from multiple industrial wastewater plants show that the biologically treated effluent exhibits similar three-dimensional fluorescence (EEM) spectral characteristics, with characteristic peaks related to humic acid and fulvic acid compounds, while TN is mainly represented by NO3. - It exists in the form of -N. In recent years, water purification processes based on electrocatalytic oxidation technology have attracted worldwide attention due to their strong oxidation capacity, simple operation, and lack of secondary pollution. However, some drawbacks of traditional electrochemical processes, such as low current efficiency, mass transfer limitations, and high cost, restrict their practical application. Humic acid is also a typical free radical quencher, which reduces reaction efficiency and results in high energy consumption. Summary of the Invention

[0003] In order to solve the problems of low current efficiency, mass transfer limitation and high cost of traditional electrochemical processes, this invention provides a method for deep treatment of high-salinity industrial wastewater.

[0004] This invention is achieved through the following technical solution: a method for deep treatment of high-salinity industrial wastewater, comprising the following steps:

[0005] 1) Design a single electrolytic cell with a DSA electrode as the anode and a Cu / Fe electrode as the cathode, and place an ultraviolet lamp there;

[0006] 2) Turn on the power to the single electrolytic cell and control the current density in the anode and cathode cells to 5-35 mA / cm². 2 The reaction takes 1-2 hours.

[0007] 3) Turn on the UV lamp and continue the degradation reaction without changing the current density of the original electrode for 3 hours;

[0008] 4) Turn off the UV lamp and continue the reaction until nitrate nitrogen is completely removed. At this point, TN is also efficiently removed.

[0009] As a further improvement to the technical solution of the present invention, the preparation method of the Cu / Fe electrode is as follows: using copper foam as the cathode and graphite of the same size as the anode, electrodeposition is performed at a constant voltage of 5.0 V for 30 min, wherein the electrolyte of the electrodeposition solution is FeSO4·7H2O, Na2SO4 and hexadecyltrimethylammonium bromide; after electrodeposition, the prepared Cu / Fe electrode is rinsed with anhydrous ethanol, then rinsed with deionized water, and finally vacuum dried for later use.

[0010] As a further improvement to the technical solution of the present invention, the concentration of FeSO4·7H2O in the electrodeposition solution is 10 mmol / L, the concentration of Na2SO4 is 15.0 mmol / L, and the concentration of hexadecyltrimethylammonium bromide is 1.0 mmol / L.

[0011] As a further improvement to the technical solution of the present invention, the foamed copper needs to be pretreated in advance. The pretreatment method is as follows: the foamed copper electrode is immersed in H2SO4 solution to remove the natural oxides on the surface; then it is immersed in ethanol under ultrasonic waves for degreasing treatment, and then cleaned with ultrapure water under ultrasonic conditions.

[0012] As a further improvement to the technical solution of the present invention, NO3 is provided on the single electrolytic cell. - -N online detector and colorimeter.

[0013] The present invention provides a method for deep treatment of high-salinity industrial wastewater, which has the following advantages compared with the prior art:

[0014] Ultraviolet electrocatalysis for high-salinity wastewater has several drawbacks, including high color intensity, limited UV penetration, and high energy consumption. Furthermore, the wastewater contains recalcitrant organic matter such as nitrogen-containing heterocyclic compounds and reducing substances like nitrate nitrogen, which are poorly removed by ultraviolet electrocatalysis. This invention addresses the problem of high TOC and TN content in the effluent from industrial wastewater biological treatment ponds by providing an electrochemically coupled ultraviolet treatment method for simultaneous denitrification, carbon removal, and detoxification. The method utilizes a Cu / Fe electrode to achieve the electrochemical reaction. After the nitrate has completely reacted, the ultraviolet lamp is activated to enhance the generation of ClO free radicals, completely mineralizing the recalcitrant organic matter and converting organic nitrogen into inorganic nitrogen. The ultraviolet lamp is then turned off, and the reaction continues until TN is reduced to a minimum, ultimately achieving synergistic removal of TOC and TN. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the specific process of the advanced treatment method for high-salinity industrial wastewater according to the present invention.

[0018] Figure 2 The images show the XRD patterns of the copper foam and Cu / Fe electrodes before and after the reaction.

[0019] Figure 3 The images show the XPS spectra before and after the Cu / Fe electrode reaction.

[0020] Figure 4 The LSV, CV, and EIS curves are shown for copper foam and Cu / Fe electrodes.

[0021] Figure 5 This is a graph showing the changes in C and N removal in actual wastewater.

[0022] Figure 6 This is a diagram showing the changes in three-dimensional fluorescence spectra of actual wastewater at different time periods. Detailed Implementation

[0023] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0024] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0025] The specific embodiments of the present invention will be described in detail below. Example 1

[0026] 1. Preparation of Cu / Fe Electrode: A Cu / Fe foam electrode was prepared using a modified cathodic electrodeposition method. Before use, the copper foam electrode (3.0 cm × 4.0 cm × 0.1 cm) underwent pretreatment. First, it was immersed in H₂SO₄ solution (1 mol / L) for 10 minutes to remove surface natural oxides. Then, it was immersed in ethanol for 15 minutes under ultrasonic conditions for degreasing. Finally, it was rinsed with ultrapure water under ultrasonic conditions for 15 minutes.

[0027] The electrodeposition electrolyte consisted of 10 mmol / L FeSO4·7H2O, 15.0 mmol / L Na2SO4, and 1.0 mmol / L hexadecyltrimethylammonium bromide (CTAB). Pretreated copper foam was used as the cathode, and graphite of the same size as the anode. Electrodeposition was performed at a constant voltage of 5.0 V for 30 min. After electrodeposition, the prepared Cu / Fe electrode was rinsed with anhydrous ethanol, then washed with deionized water, and finally vacuum-dried at 60 °C for 24 hours for later use.

[0028] 2. X-ray powder diffraction (XRD) of Cu / Fe electrodes Figure 2 The results show three diffraction peaks at 43.32, 50.45, and 74.12, corresponding to the (111), (200), and (222) planes of the Cu (JCPDS 99-0034) alloy crystal structure, respectively. The peak values ​​shifted compared to those of copper foam after Fe electrodeposition, indicating successful preparation of the Cu / Fe electrode. The XRD peak values ​​of the composite electrode material after the reaction showed no significant change, indirectly reflecting the material's good stability.

[0029] 3. The elemental valence states of Cu and Fe before (ac) and after (df) the Cu / Fe electrode reaction were analyzed using X-ray photoelectron spectroscopy (XPS). Figure 3 (b) and (c) show the Cu2p spectra of the Cu / Fe composite cathode before and after the reaction, respectively, with a total of 6 characteristic peaks. Among them, 931.21 eV and 952.35 eV correspond to Cu2p peaks and Cu2p peaks, respectively. 0 2p1 / 2 and Cu 0 The electron binding energies of 2p³ / ², 934.51 eV and 954.80 eV, correspond to Cu, respectively. 2+ 2p3 / 2 and Cu 2+ The electron binding energies of 2p¹ / ², 943.18 eV and 963.59 eV, correspond to Cu, respectively. 2+ 2p3 / 2 and Cu 2+ The electron binding energy of 2p¹ / ² indicates the presence of CuO. The electron binding energy of Cu remains essentially unchanged before and after the reaction. 710.8 eV and 724.5 eV correspond to the electron binding energies of Fe²p³ / ² and Fe²p¹ / ², respectively. The characteristic peak at 710.8 eV indicates the presence of iron oxide in the material, possibly due to the oxidation of a small portion of the surface of the deposited iron particles exposed to air. The decrease in the peak at 710.8 eV after the reaction indicates partial oxidation of Fe(II). The characteristic peaks of the Fe(III) 2p spectrum at 719.0 eV and 731.2 eV also show a partial decrease after the reaction. The comparison of the material before and after the reaction shows that Cu and Fe are predominantly in the metallic state in the bimetallic catalyst, further demonstrating the successful preparation and reusability of the material.

[0030] 4. Electrochemical Testing

[0031] A series of LSV, CV, and EIS tests were performed on the copper foam and the Cu / Fe electrode. The results are shown in [Figure number missing]. Figure 4 . Figure 4 -a shows a comparison of the LSV (Laser Current Variation) of the copper foam electrode and the Cu / Fe electrode. It can be seen that the Cu / Fe electrode has a significantly higher peak current compared to the copper foam electrode, indicating that the introduction of Fe promotes the adsorption and degradation of nitrates. This suggests that the increased active surface area of ​​the Cu / Fe electrode further enhances the electroreduction activity of the material. At the same potential, the current density of the Cu / Fe electrode is higher than that of the copper foam electrode, indicating that the Cu / Fe electrode degrades NO3 in the solution more effectively than the copper foam electrode. - -N has strong capabilities. Figure 4 -b illustrates the redox process of electrocatalytic denitrification using copper foam and Cu / Fe electrodes. Compared to copper foam, the Cu / Fe electrode exhibits distinct redox peaks. An oxidation peak appears in the range of -1.0 V to -0.3 V, which corresponds to atomic hydrogen desorption. A dense reduction peak appears in the range of -0.4 V to -1.1 V, due to nitrate reduction. The rapid decline after -1.3 V is a result of hydrogen production. Figure 4 -c shows a comparison of EIS images for copper foam and Cu / Fe electrodes. The arc radius of the copper foam electrode is larger than that of the bimetallic material, indicating that the addition of Fe reduces interfacial impedance and enhances electron transfer. From the perspective of binding energy, Fe has good adsorption energy for nitrogen oxides. The results show that the addition of iron is beneficial for NO3- adsorption. - Reduced to NH4 + . Example 2

[0032] A method for deep treatment of high-salinity industrial wastewater includes the following steps:

[0033] 1) Design a single electrolytic cell, using a DSA electrode as the anode and the Cu / Fe electrode prepared in Example 1 as the cathode, and place an ultraviolet lamp there. Simultaneously, NO3 is placed on the single electrolytic cell. - -N online detector, colorimeter;

[0034] 2) Turn on the power to the single electrolytic cell and control the current density in the anode and cathode cells to 30 mA / cm². 2 The reaction lasted for 2 hours; the nitrate removal rate was close to 100%, or it was converted into NH4. + -N, or converted to N2, where NH4 + -N is converted into N2 through a chloramine reaction using HClO generated at the anode, thus achieving effective removal of TN;

[0035] 3) Turn on the ultraviolet lamp and continue the degradation reaction without changing the current density of the original electrodes. The reaction lasts for 3 hours. Under the action of ClO free radicals, the recalcitrant organic matter is completely mineralized, and some nitrogen-containing heterocyclic compounds are converted into inorganic nitrogen.

[0036] 4) Turn off the UV lamp and continue the reaction for 1 hour until nitrate nitrogen is completely removed. At this time, TN is also efficiently removed.

[0037] This embodiment describes the treatment of effluent from a biological treatment pond for industrial wastewater. The initial pH was approximately 7, and the NO3 content was low. - The -N concentration was 50 mg / L, the initial TOC concentration was 80 mg / L, and the TN concentration was 230 mg / L. The reaction time was 6 h (EO2h + UV - EO3h + EO1h), the electrode spacing was 3.5 cm, and the current density was 30 mA / cm². 2 The changes in C and N during the reaction process are as follows: Figure 5 As shown in the figure, the TOC concentration after the reaction was 13.2 mg / L, with a removal rate of 83.5%, and the TN concentration was 230 mg / L, with a removal rate of 91.7%.

[0038] Three-dimensional fluorescence spectrum analysis was performed on the above water quality data, and three-dimensional fluorescence spectra at different time points (0, 2, 3, and 5 hours) were obtained, such as... Figure 6 As shown in the figure, it can be seen that in the first stage, when only electrocatalysis is used for organic matter removal, the fluorescence area decreases, but the organic matter is not completely removed. The larger fluorescence intensity is located at λ. Ex / λ Em = (260~280nm) / (300~325nm), another fluorescent region is located at λ Ex / λ Em = (270~290nm) / (340~360nm). These two main fluorescence regions represent humic acid-like substances. After UV synergistic treatment, the overall intensity of the fluorescence peak in the effluent was further reduced, and the fluorescence peak intensity could be completely removed in just 1 hour of reaction. The UV process can generate active chlorine free radicals, which promotes and enhances the removal of organic matter in the reaction.

[0039] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. A method for deep treatment of high-salinity industrial wastewater, characterized in that, The steps include: 1) Design a single electrolytic cell with a DSA electrode as the anode and a Cu / Fe electrode as the cathode, and place an ultraviolet lamp there; 2) Turn on the power to the single electrolytic cell and control the current density in the anode and cathode cells to 5-35 mA / cm². 2 The reaction takes 1-2 hours. 3) Turn on the UV lamp and continue the degradation reaction without changing the current density of the original electrode for 3 hours; 4) Turn off the UV lamp and continue the reaction until nitrate nitrogen is completely removed. At this point, TN is also efficiently removed.

2. The method for deep treatment of high-salinity industrial wastewater according to claim 1, characterized in that, The Cu / Fe electrode is prepared as follows: using copper foam as the cathode and graphite of the same size as the anode, electrodeposition is performed at a constant voltage of 5.0 V for 30 min. The electrolyte in the electrodeposition solution is FeSO4·7H2O, Na2SO4 and hexadecyltrimethylammonium bromide. After electrodeposition, the prepared Cu / Fe electrode is rinsed with anhydrous ethanol, then rinsed with deionized water, and finally vacuum dried for later use.

3. The method for deep treatment of high-salinity industrial wastewater according to claim 2, characterized in that, The electrodeposition solution contained 10 mmol / L FeSO4·7H2O, 15.0 mmol / L Na2SO4, and 1.0 mmol / L hexadecyltrimethylammonium bromide.

4. The method for deep treatment of high-salinity industrial wastewater according to claim 2, characterized in that, The copper foam needs to be pretreated in advance. The pretreatment method is as follows: soak the copper foam electrode in H2SO4 solution to remove the natural oxides on the surface; then soak it in ethanol under ultrasonication for degreasing treatment, and then clean it with ultrapure water under ultrasonic conditions.

5. The method for deep treatment of high-salinity industrial wastewater according to claim 1, characterized in that, The single electrolytic cell is equipped with NO3. - -N online detector and colorimeter.

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