Dual anode electrochemical reactor and method for in-situ generation of high valence iron for treatment of high salinity organic wastewater

Abstract

A double anode electrochemical reactor for in-situ generation of high-valence iron to treat high-salinity organic wastewater, comprising an electrochemical reactor shell and a first anode, a second anode and a stainless steel cathode located therein; the first anode is an iron electrode, which generates Fe(II) after electrolysis, and Fe(II) is oxidized to Fe(III) to form Fe(OH)3; the second anode is a titanium-based metal oxide coating electrode, which, after being electrified, converts Cl ‑ in high-salinity organic wastewater into HClO / ClO ‑ ; Fe(OH)3 and HClO / ClO ‑ interact to generate high-valence iron, based on HClO / ClO ‑ and high-valence iron, to simultaneously remove organic matter and ammonia nitrogen in high-salinity organic wastewater; wherein the high-valence iron includes Fe(IV), Fe(V) and Fe(VI), Fe(VI) is generated by the reaction of Fe(OH)3 and HClO / ClO ‑ , and Fe(IV) and Fe(V) are generated in the process of decomposition of Fe(VI).

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and relates to wastewater treatment technology, and in particular to a dual-anode electrochemical reactor and method for in-situ generation of high-valent iron to treat high-salt organic wastewater. Background Technology

[0002] High-salinity organic wastewater mainly originates from chemical, pharmaceutical, agrochemical, and coal chemical production processes, containing large amounts of organic matter, salts, ammonia nitrogen, heavy metals, petroleum hydrocarbons, and other pollutants. Its wide range of sources, complex composition, and high salinity make it challenging to treat. Advanced oxidation processes based on free radical generation are common industrial wastewater treatment technologies; however, high-salinity organic wastewater contains a large number of inorganic anions that quench free radicals, limiting the effectiveness of these processes. Ferric iron (Fe3+), as a non-free radical oxidant with strong oxidizing power, shows great promise for wastewater treatment; however, its instability poses challenges to its preparation, storage, and transportation, and its complex synthesis methods also limit its application in oxidation. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a dual-anode electrochemical reactor and method for in-situ generation of ferric iron to treat high-salt organic wastewater. The method generates ferric iron in-situ through a dual-anode electrochemical method to treat high-salt organic wastewater in-situ, and simultaneously and efficiently removes COD and ammonia nitrogen.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A dual-anode electrochemical reactor for in-situ generation of high-valent iron to treat high-salt organic wastewater includes an electrochemical reactor shell and a first anode, a second anode, and a stainless steel cathode located therein.

[0006] The first anode is an iron electrode. When electricity is applied, Fe(II) is electrolyzed and Fe(II) is oxidized to Fe(III) to form Fe(OH)3.

[0007] The second anode is a titanium-based metal oxide coated electrode, which, when energized, removes Cl- from the high-salt organic wastewater. - Converted to HClO / ClO - ;

[0008] The Fe(OH)3 and HClO / ClO - The interaction generates high-valence iron, based on the HClO / ClO -Simultaneously with the high-valent iron, organic matter and ammonia nitrogen are removed from the high-salt organic wastewater; wherein, the high-valent iron includes Fe(IV), Fe(V) and Fe(VI), and Fe(VI) is produced by Fe(OH)3 and HClO / ClO. - The reaction produces Fe(IV) and Fe(V) during the decomposition of Fe(VI).

[0009] In one embodiment, the first anode and the second anode are connected to the same constant current regulated power supply.

[0010] In one embodiment, the titanium-based metal oxide coated electrode has a titanium substrate and a ruthenium dioxide or iridium dioxide metal oxide coating. There are no requirements for the coating thickness, and commercially available titanium-based metal oxide coated electrodes are acceptable.

[0011] In one embodiment, the first anode and the second anode are symmetrically arranged on both sides of the stainless steel cathode. All three are plate-shaped electrodes of the same size, each with several holes. The electrode spacing is 55–75 mm, and the current density is 8–17 mA / cm². 2 .

[0012] This invention also provides a method for treating high-salt organic wastewater by in-situ generation of ferric iron, based on a dual-anode electrochemical reactor for treating high-salt organic wastewater by in-situ generation of ferric iron. The method involves: introducing the high-salt organic wastewater to be treated into the outer shell of the electrochemical reactor; adding 5–12.5 g / L sodium hydroxide (based on wastewater concentration); then energizing each electrode; and utilizing the generated HClO / ClO₂. - Along with high-valent iron, it simultaneously removes organic matter and ammonia nitrogen from the high-salt organic wastewater; wherein, the dual-anode electrochemical reactor operates in continuous flow mode with a hydraulic retention time of 60-70 min.

[0013] In one embodiment, the high-salt organic wastewater is mechanically stirred at 150–250 r / min during operation.

[0014] In one embodiment, the continuous flow mode allows the high-salt organic wastewater to enter from the lower part of the electrochemical reactor shell and exit from the upper part.

[0015] In one embodiment, the high-salt organic wastewater has a chloride ion concentration of 4000–6000 mg / L, an organic matter concentration of 50000–80000 mg / L (based on COD), and an electrical conductivity of 16–17 mS / cm.

[0016] In one embodiment, the dual-anode electrochemical reactor, under optimal operating conditions, simultaneously removes organic matter and ammonia nitrogen from high-salt organic wastewater, achieving an organic matter removal rate of 51% and an ammonia nitrogen removal rate of 38%; the optimal operating conditions are a current density of 12.5 mA / cm².2 The sodium hydroxide dosage is 10 g / L.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. Based on the dual-anodine reaction, Cl in high-salt organic wastewater is removed. - By making full use of the in-situ generated high-valence iron for the treatment of high-salt organic wastewater, the simultaneous and efficient removal of organic matter and ammonia nitrogen from high-salt organic wastewater is achieved.

[0019] 2. Besides the oxidation of high-valence iron, HClO / ClO - Oxidation can further enhance the treatment effect of high-salt organic wastewater.

[0020] 3. The process is simple, easy to operate, and occupies a small area. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention.

[0022] Figure 2 The removal rates of organic matter and ammonia nitrogen in this invention are... Detailed Implementation

[0023] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0024] The high-salt organic wastewater referred to in this invention generally refers to wastewater with a chloride ion concentration of 4000-6000 mg / L, an organic matter (COD) concentration of 50000-80000 mg / L, and a conductivity of 16-17 mS / cm.

[0025] Existing treatments for high-salinity organic wastewater often employ advanced oxidation technologies based on free radical oxidation. However, the quenching of anions inhibits free radical reactions, severely impacting the treatment efficiency of these technologies. Therefore, this invention utilizes a dual-anode electrochemical reactor to generate a non-free radical oxidant—ferric iron—in situ for the in-situ treatment of high-salinity organic wastewater. Furthermore, the in-situ generation of ferric iron also solves the problems associated with its preparation, storage, and transportation due to its instability.

[0026] like Figure 1 As shown, the present invention first provides a dual-anode electrochemical reactor for in-situ generation of ferric iron to treat high-salt organic wastewater, comprising an electrochemical reactor shell 1, and a first anode 3, a second anode 4, and a stainless steel cathode 5 disposed within the electrochemical reactor shell 1. The first anode 3 and the second anode 4 are both working anodes of the dual-anode electrochemical reactor, and the stainless steel cathode 5 is the working cathode of the dual-anode electrochemical reactor.

[0027] The first anode (3) is an iron electrode, which electrolyzes to produce Fe(II) after being energized. Fe(II) is then oxidized to Fe(III) to form Fe(OH)3. The second anode (4) is a titanium-based metal oxide coated electrode, which, after being energized, removes Cl- from the high-salt organic wastewater. - Converted to HClO / ClO - The high-valent iron of the present invention is composed of the aforementioned Fe(OH)3 and the aforementioned HClO / ClO - Generated through interactions, including Fe(IV), Fe(V), and Fe(VI), with Fe(VI) formed from Fe(OH)3 and HClO / ClO. - The reaction produces Fe(IV) and Fe(V), which are generated during the decomposition of Fe(VI). Fe(IV), Fe(V), and Fe(VI) can all oxidize and remove organic matter and ammonia nitrogen from high-salt organic wastewater. Fe(IV) and Fe(V) have stronger oxidizing power than Fe(VI) and are the main active substances for the removal of organic matter and ammonia nitrogen.

[0028] Based on the aforementioned HClO / ClO - Together with the aforementioned high-valence iron, organic matter and ammonia nitrogen can be removed simultaneously from high-salt organic wastewater.

[0029] In this embodiment of the invention, the first anode 3 and the second anode 4 are symmetrically arranged on both sides of the stainless steel cathode 5. All three are plate-shaped electrodes, each with several holes. The plate-shaped electrodes are of the same size, parallel to each other, with an electrode spacing of 55-75 mm and a current density of 8-17 mA / cm². 2 For example, the outer shell of the electrochemical reactor 1 is made of rectangular plexiglass, with dimensions of 100mm x 70mm x 105mm (length x width x height), and an effective reaction volume of 400cm³. 3 The effective area of ​​the plates is the same, which is 70mm×60mm×1mm (length×width×thickness). Each plate has 9 holes with a diameter of 9mm.

[0030] In this embodiment of the invention, a constant current regulated power supply 6 is used to supply power to the first anode 3 and the second anode 4. Specifically, the positive terminal of the constant current regulated power supply 6 is connected to the first anode 3 and the second anode 4, and the negative terminal is connected to the stainless steel cathode 5. The range of electrode current is determined based on the effective area of ​​the electrode and the current density. In practical applications, the current parameters can be determined based on the effective area of ​​existing electrode plates and the current density range provided by this invention.

[0031] In this embodiment of the invention, the substrate of the titanium-based metal oxide coated electrode is titanium, and the metal oxide coating is ruthenium dioxide or iridium dioxide, etc. There are no requirements for the coating thickness, and commercially available titanium-based metal oxide coated electrodes are acceptable.

[0032] To achieve continuous flow, in this embodiment of the invention, an inlet 7 is provided at the bottom of the side wall of the electrochemical reactor shell 1, and an outlet 8 is provided at the top of the side wall of the electrochemical reactor shell 1, so that the high-salt organic wastewater to be treated flows in from the inlet 7 and flows out from the outlet 8. Simultaneously, to improve the reaction effect, a mechanical stirrer 2 can also be provided inside the electrochemical reactor shell 1.

[0033] The method and principle of this invention for treating high-salt organic wastewater by in-situ generation of high-valent iron are as follows:

[0034] The high-salt organic wastewater to be treated is introduced into the outer shell 1 of the electrochemical reactor through inlet 7. Sodium hydroxide (5–12.5 g / L, based on wastewater volume) is added to introduce OH-. - Then, current is applied to each electrode, with the current density set to 8–17 mA / cm². 2 Utilizing the generated HClO / ClO - Along with high-valent iron, it simultaneously removes organic matter and ammonia nitrogen from high-salt organic wastewater; the dual-anode electrochemical reactor operates in continuous flow mode with a hydraulic retention time of 60–70 min. During the process, the high-salt organic wastewater is mechanically stirred at 150–250 r / min.

[0035] The first anode 3 electrolyzes to produce Fe(II), which is further oxidized to Fe(III) to form Fe(OH)3. The second anode 4 removes Cl from the high-salt organic wastewater. - Converted to HClO / ClO - Fe(OH)3 and HClO / ClO - A solid-liquid heterogeneous reaction occurs, generating high-valence iron including Fe(IV), Fe(V), and Fe(VI). During the treatment process, HClO / ClO... - It also participates in the oxidative removal of pollutants, including ferric iron and HClO / ClO. - The organic matter and ammonia nitrogen in the high-salt organic wastewater are removed simultaneously and efficiently. The treated wastewater flows out from the outlet 8 on the upper side wall of the electrochemical reactor 1.

[0036] A specific embodiment of using the above-mentioned reactor for the treatment of high-salt organic wastewater shows that the COD concentration in the wastewater is 66208.67±1666.48 mg / L and the ammonia nitrogen concentration is 471.65±52.81 mg / L. The treatment process is as follows:

[0037] 1. During normal treatment, high-salt organic wastewater enters the electrochemical reactor 1 through the inlet 7 at the bottom of the side wall. The pH is adjusted by adding sodium hydroxide at a rate of 10 g / L. A mechanical stirrer continuously stirs the water at a speed of 150–250 r / min. The positive terminal of the constant current and voltage regulator 6 is connected to the first anode 3 and the second anode 4, and the negative terminal is connected to the stainless steel cathode 5. The electrode spacing is set to 60 mm, and the current density is set to 12.5 mA / cm². 2 .

[0038] 2. During the treatment process, the iron electrode 3 electrolyzes to produce Fe(II), which is further oxidized to Fe(III) to form Fe(OH)3. The titanium-based metal oxide coated electrode 4 removes Cl from the high-salt organic wastewater. - Converted to HClO / ClO - Fe(OH)3 and HClO / ClO - A solid-liquid heterogeneous reaction occurs to generate high-valent iron, including Fe(IV), Fe(V), and Fe(VI), which is used to oxidize organic matter and ammonia nitrogen. Simultaneously, HClO / ClO... - It also participates in the oxidation and removal of pollutants.

[0039] 3. After a hydraulic retention time of 60 minutes, the treated wastewater flows out from outlet 8 on the upper side wall of electrochemical reactor 1. The test results are referenced below. Figure 2 In this embodiment, under optimal operating conditions, organic matter and ammonia nitrogen are removed simultaneously from high-salt organic wastewater, with an organic matter removal rate of 51% and an ammonia nitrogen removal rate of 38%.

[0040] In summary, this invention achieves simultaneous and efficient removal of organic matter and ammonia nitrogen from high-salt organic wastewater by generating high-valence iron in situ.

Claims

1. A method for treating high-salinity organic wastewater by in-situ generation of high-valence iron, which is realized by a dual-anode electrochemical reactor for treating high-salinity organic wastewater by in-situ generation of high-valence iron, the dual-anode electrochemical reactor comprising an electrochemical reactor shell (1) and a first anode (3), a second anode (4) and a stainless steel cathode (5) located therein; the first anode (3) is an iron electrode, which generates Fe(II) after electrolysis, and Fe(II) is oxidized to Fe(III) to form Fe(OH)3; the second anode (4) is a titanium-based metal oxide coating electrode, which converts Cl - in the high-salinity organic wastewater into HClO / ClO - after being electrified; the Fe(OH)3 and HClO / ClO - interact to generate high-valence iron, and based on the HClO / ClO - and the high-valence iron, organic matter and ammonia nitrogen in the high-salinity organic wastewater are simultaneously removed; wherein, The high valent iron includes Fe(IV), Fe(V) and Fe(VI), Fe(VI) is generated from Fe(OH)3 and HClO / ClO - Fe(IV) and Fe(V) are generated in the process of Fe(VI) decomposition; Its characterized in that, the high-salinity organic wastewater to be treated is introduced into the electrochemical reactor shell (1), 5-12.5 g / L of sodium hydroxide is added in terms of wastewater, and then power is supplied to each electrode, HClO / ClO - and high-valence iron are generated, and the organic matter and ammonia nitrogen in the high-salinity organic wastewater are synchronously removed; wherein the double-anode electrochemical reactor is operated in a continuous flow mode, and the hydraulic retention time is 60-70 min.

2. The method for treating high-salinity organic wastewater by in-situ generation of high-valent iron according to claim 1, characterized in that, During operation, the high-salt organic wastewater is subjected to mechanical stirring at 150-250 r / min.

3. The method for treating high-salinity organic wastewater by in-situ generation of high-valent iron according to claim 1, characterized in that, The continuous flow mode allows the high-salt organic wastewater to flow into the lower part of the electrochemical reactor shell (1) and flow out from the upper part.

4. The method for treating high-salinity organic wastewater by in-situ generation of high-valent iron according to claim 1, characterized in that, The high-salt organic wastewater has a chlorine ion concentration of 4000-6000 mg / L, an organic matter concentration of 50000-80000 mg / L in terms of COD, and a conductivity of 16-17 ms / cm.

5. The method for treating high-salinity organic wastewater by in-situ generation of high valence iron according to claim 1, characterized in that, The double anode electrochemical reactor synchronously removes organic matter and ammonia nitrogen in high-salt organic wastewater under optimal working conditions, the removal rate of organic matter is 51%, and the removal rate of ammonia nitrogen is 38%; the optimal working conditions are that the current density is 12.5 mA / cm 2 , and the sodium hydroxide dosage is 10 g / L.

6. The method for treating high-salinity organic wastewater by in-situ generation of high valence iron according to claim 1, characterized in that, The first anode (3) and the second anode (4) are connected to the same constant-current stabilized power supply (6).

7. The method for treating high-salinity organic wastewater by in-situ generation of high valence iron according to claim 1, characterized in that, The titanium-based metal oxide coating electrode has a titanium base and a metal oxide coating of ruthenium dioxide or iridium dioxide.

8. The method for treating high-salinity organic wastewater by in-situ generation of high valence iron according to claim 1, characterized in that, The first anode (3) and the second anode (4) are symmetrically arranged on two sides of the stainless steel cathode (5), and all of them are plate-shaped electrodes with the same size, each of which is punched with a plurality of holes, the electrode spacing is 55-75 mm, and the current density is 8-17 mA / cm 2 .

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