An electro-Fenton-like organophosphoric acid wastewater and synchronous phosphorus recovery treatment system and method

Abstract

This invention provides a quasi-electro-Fenton treatment system for simultaneously removing and recovering phosphorus from organophosphoric acid wastewater, belonging to the field of water pollution control. It solves the problems of low efficiency and susceptibility to substrate Cl in traditional Fenton processes for degrading organophosphoric acid. ‑ The challenge of suppressing interference, Cl in the electro-Fenton process ‑ To the active species HClO and Fe IV O 2+ The conversion of substrate waste into organic phosphoric acid waste enables its beneficial utilization. The electro-Fenton-like treatment system comprises a pH adjustment zone and an electro-Fenton-like reaction zone. The pH adjustment zone includes a pH adjustment tank, an acid / alkali dosing tank, and a pH controller. The electro-Fenton-like reaction zone includes a Fenton reaction tank, an Fe source / sodium chloride dosing tank, electrode plates, a power supply, and a precipitation conduit. Using this electro-Fenton-like system to treat organic phosphoric acid wastewater allows for the efficient degradation of organically bound phosphorus into orthophosphate, while simultaneously recovering the eutrophic pollutant organic phosphoric acid in the form of iron phosphate. This electro-Fenton-like system provides a feasible solution for the treatment of organic phosphoric acid wastewater.

Description

Technical Field

[0001] This invention belongs to the field of water pollution control, and specifically refers to a Cl... - A water treatment system that uses induced electro-Fenton oxidation to remove organic phosphoric acid and simultaneously recover phosphorus. Background Technology

[0002] Organophosphoric acid is widely used as a stabilizer / scale inhibitor in industries such as papermaking, textiles, cleaning products, and cooling water circulation systems. Besides inorganic orthophosphates, organophosphoric acid is a significant form of phosphorus in industrial wastewater. Direct discharge without treatment can cause eutrophication pollution, but it is not the target of existing wastewater treatment processes. The presence of organophosphoric acid inhibits the final removal efficiency of total phosphorus in wastewater, making it difficult to meet surface water phosphorus discharge standards. Furthermore, phosphorus, an essential element for all life forms, is mined at a rate far exceeding natural geological replenishment, leading to phosphorus resource scarcity. Based on these issues, there is currently a significant lack of treatment technologies for the effective removal and simultaneous recovery of phosphorus from organophosphoric acid.

[0003] The most widely accepted phosphorus removal methods include biological treatment and chemical precipitation. Due to the presence of typical covalent CP bonds, organophosphoric acids exhibit high stability for biodegradation, while chemical precipitation only achieves the transfer of pollutants rather than their removal. Therefore, advanced oxidation processes (AOS) have been proposed and applied to the treatment of organophosphoric acid wastewater. The Fenton technique, commonly used in industry, has relatively low efficiency in degrading organophosphoric acids and is susceptible to substrate chlorides. - The inhibitory interference indicates that HO· and secondary active chlorine radicals contribute limitedly to the degradation of organophosphates in the traditional Fenton system. This inspires us to consider the potential of other bioactive species to degrade organophosphates.

[0004] Electro-Fenton oxidation can reduce Cl - It is anoly oxidized to HClO, and then reacts with Fe(II) to produce Fe. IV O 2+ Immediately, substrate waste Cl - It is transformed into a selective oxidant, which not only solves the problem of Cl... - Suppressing interference, and even enabling the use of Cl - This provides a feasible approach to improving the degradation efficiency of organophosphates. Summary of the Invention

[0005] To address the existing technical problems, the present invention aims to provide an electro-Fenton-like treatment system and method for the efficient degradation and simultaneous phosphorus recovery of organic phosphoric acid wastewater. This system treats saline organic phosphoric acid wastewater, achieving the recovery of HClO and Fe. IV O 2+ and 1The efficient generation and effective utilization of O2 significantly improves the conversion efficiency of organic phosphoric acid to orthophosphoric acid, and the generation of iron phosphate precipitate enables the eutrophic pollutant organic phosphoric acid to be recovered in the form of orthophosphoric acid.

[0006] To achieve the above objectives, the present invention provides an electro-Fenton-like system for treating organic phosphoric acid wastewater, comprising a pH adjustment zone and an electro-Fenton-like reaction zone.

[0007] The front end of the pH adjustment zone is connected to the organic phosphoric acid wastewater inlet. Acid / alkali is added through the dosing tank of the pH adjustment tank, and the pH of the wastewater is monitored by the pH controller to meet the initial pH requirements for the operation of the electro-Fenton reaction in the Fenton reaction tank. The baffle of the pH adjustment tank is set on the left side of the wastewater outlet of the pH adjustment tank to change the water flow direction and buffer the inlet water.

[0008] The electro-Fenton-like reaction zone has an inlet at its front end, connected to the pH adjustment zone, and an outlet and a sedimentation outlet at its rear end. The conical hopper design facilitates phosphorus precipitation and recovery. The electro-Fenton-like reaction zone is equipped with a separate ferrous / sodium chloride supply device, the supply rate of which is determined based on the organic phosphoric acid wastewater quality parameters, providing ferrous catalyst and sodium chloride for the Fe(II) / HClO electro-Fenton-like reaction. The positive and negative terminals of the power supply are connected to an anode plate coated with ruthenium-iridium oxide on a titanium substrate and a stainless steel cathode plate, respectively. The current intensity is adjusted to meet the operational requirements of the electro-Fenton-like reaction. A baffle plate for the Fenton reaction tank is located to the left of the outlet to facilitate the Fenton-like reaction and sedimentation.

[0009] Another aspect of the present invention is to provide an electro-Fenton-like method for treating organic phosphoric acid wastewater using the aforementioned electro-Fenton-like system, specifically comprising:

[0010] The salt content of the organophosphoric acid wastewater treated by the aforementioned electro-Fenton system is calculated as sodium chloride, with a preferred sodium chloride concentration range of 28.2-225.7 mM. Chloride ions are widely present in organophosphoric acid wastewater, such as organophosphoric acid production wastewater and textile dyeing wastewater. - If the content is sufficient to meet the requirements of an electro-Fenton reaction, then there is no need to add sodium chloride.

[0011] Before carrying out the electro-Fenton-like reaction, the initial pH of the organic phosphoric acid wastewater is preferably 3.5. Ferrous sulfate is added to the electro-Fenton-like reaction zone to catalyze the operation of the electro-Fenton-like reaction, and the Fe(II) / organic phosphoric acid molar ratio is preferably 18.2:1.

[0012] The preferred current density for the electro-Fenton system in treating organophosphate wastewater is 4.3-21.3 mA / cm². 2 The degradation equilibrium time of organophosphoric acid is effectively shortened with the increase of current density.

[0013] The principle of the electro-Fenton-like reaction in the organophosphate wastewater treatment system provided by this invention is as follows:

[0014] Wastewater matrix Cl - After anodic oxidation to Cl2, it dissolves in water to rapidly generate HClO (Equation 1-2). Under acidic conditions, it combines with Fe(II) in a Fenton-like reaction to generate Fe. IV O 2+ (Equation 3); not only derived from Fe(II), Fe IV O 2+ It can also be generated from Fe(III) active sites. The Fe(III)-derived pathway tends to produce [Fe] through the spontaneous interaction between Fe(III) and H2O2. III OOH] 2+ Homolytic cleavage of the OO bond in the complex to form Fe IV O 2+ (Equation 4-5); The H2O2 originates from the single-electron reduction of O2 on the cathode surface. ·- The disproportionation reaction of Fe(II) (Equation 6-7). Furthermore, O2 is produced by the reaction of Fe(II) with dissolved oxygen in water. ·- It can then be transformed into 1 O2 (Equation 8). In summary, HClO, Fe... IV O 2+ and 1 O2 is the main active species for the efficient degradation of organophosphates. The presence of alkali metal Fe provides active sites for the precipitation and recovery of orthophosphate.

[0015] 2Cl - → Cl2 + 2e - (1)

[0016] Cl2 + H2O → HClO + HCl (2)

[0017] Fe(II) + HClO → Fe IV O 2+ + HCl (3)

[0018]

[0019] [Fe III OOH] 2+ → Fe IV O 2+ + HO· (5)

[0020] O2 ·- + H + → HO2 · (6)

[0021] O2 ·-+ HO2 · + H2O → H2O2 + O2 + OH - (7)

[0022] Fe(II) + O2 → O2 ·- +Fe(III) (8)

[0023] The beneficial effects of this invention are as follows:

[0024] This invention proposes a one-step solution for the removal and phosphorus recovery of non-orthophosphates from organophosphate wastewater, overcoming the technical challenges of phosphorus recovery from non-orthophosphates. Compared to the traditional Fenton process, which has low efficiency in degrading organophosphates and is susceptible to substrate Cl, this solution offers a superior solution. - To address the challenge of suppressing interference, this invention proposes an electro-Fenton-like method that removes substrate waste Cl during operation. - It is converted into HClO and indirectly into Fe. IV O 2+ The oxidant turns waste into treasure, significantly increasing the conversion efficiency of organically bound phosphorus in organic phosphoric acid to orthophosphorus to nearly 90%.

[0025] Furthermore, the electro-Fenton-like treatment system for one-step removal and recovery of organic phosphoric acid proposed in this invention recovers organic phosphoric acid in the form of orthophosphorus in the precipitate, which can be reused as a raw material for the production of lithium iron phosphate batteries, phosphate fertilizers or phosphates. This reduces the solid waste treatment costs of water treatment companies and increases their profits, marking an important step towards a phosphorus circular economy.

[0026] Furthermore, the electro-Fenton-like treatment system for one-step removal and recovery of organic phosphoric acid proposed in this invention has a simple structure, is easy to operate, has low operating costs, and is suitable for engineering applications. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a quasi-electro-Fenton treatment system for the removal and simultaneous recovery of phosphorus from organic phosphoric acid wastewater, provided by the present invention.

[0028] in:

[0029] Ⅰ: pH adjustment zone, including: 1-0 pH adjustment tank, 1-1 pH adjustment tank inlet, 1-2 pH adjustment tank dosing tank, 1-3 pH controller, 1-4 pH adjustment tank baffle, 1-5 pH adjustment tank agitator;

[0030] II: Fenton reaction zone, including: 2-0 Fenton reaction tank, 2-1 Fenton reaction tank inlet, 2-2 power supply, 2-3 anode plate, 2-4 cathode plate, 2-5 Fenton reaction tank dosing tank, 2-6 Fenton reaction tank agitator, 2-7 sedimentation conduit, 2-8 sedimentation outlet, 2-9 Fenton reaction tank baffle, 2-10 drain outlet. Detailed Implementation

[0031] The present invention will be further illustrated below with specific embodiments, but these are not intended to limit the scope of protection of the present invention.

[0032] Example 1

[0033] like Figure 1 As shown, the present invention provides a Fenton-like electrochemical system for treating organophosphoric acid wastewater, mainly composed of a pH adjustment zone and an Fenton-like electrochemical reaction zone. The organophosphoric acid wastewater is first pumped into pH adjustment tank 1-0 through pH adjustment tank inlet 1-1. The influent is mixed using pH adjustment tank agitator 1-5 to stabilize the water quality. An appropriate amount of acid / alkali is supplied through pH adjustment tank dosing tank 1-2, and pH controller 1-3 monitors the wastewater pH change to meet the initial pH requirements of the Fenton-like electrochemical reaction. Next, the effluent from pH adjustment tank is pumped into Fenton reaction tank 2-0 through Fenton reaction tank inlet 2-1. Ferrous sulfate / sodium chloride is supplied through Fenton reaction tank dosing tank 2-5 and mixed evenly using Fenton reaction tank agitator 2-6. After adjusting to the required current intensity, DC power supply 2-2 is turned on. The organophosphoric acid wastewater to be treated is electrolyzed under the action of the titanium-ruthenium-iridium anode plate 2-3 and the stainless steel cathode plate 2-4. Specifically: Cl... - At point 2-3 on the anode plate, the anode loses electrons and is oxidized to Cl2 (Equation 1), which then dissolves in water to form HClO (Equation 2). HClO, as a substrate for a Fenton-like reaction, reacts with the catalyst Fe(II) to generate Fe. IV O 2+ (Equation 3) O2 is reduced by a single electron on the surface of the cathode plate 2-4. ·- The disproportionation reaction generates H2O2 (Equation 6-7), wherein the O2 ·- Derived from the redox reaction of Fe(II) with dissolved oxygen (Equation 8), H2O2 also acts as a substrate for a Fenton-like reaction, spontaneously interacting with Fe(III) to generate [Fe III OOH] 2+ Homolytic cleavage of the OO bond in the complex to form Fe IV O 2+ (Equation 4-5), HClO and Fe in an electro-Fenton-like reaction system IV O 2+ and from O2 ·- of 1 O2 synergistically and efficiently degrades organophosphoric acid into orthophosphoric acid, which then combines with Fe(III) to form ferric phosphate precipitate, which is then recovered. When the wastewater treated by the electro-Fenton-like system achieves efficient orthophosphoric acid conversion and the total phosphorus content meets my country's surface water phosphorus discharge standards, the power is turned off, and the qualified wastewater from the electro-Fenton-like reaction zone is discharged from the outlet 2-10, while the precipitate is discharged from the sedimentation conduit 2-7 and the sedimentation outlet 2-8.

[0034] Comparative Example 1

[0035] This invention utilizes an electro-Fenton-like device for treating organophosphoric acid wastewater to perform conventional Fenton methods. The organophosphoric acid wastewater is first pumped into pH adjustment tank 1-0 through inlet 1-1. Agitator 1-5 in the pH adjustment tank mixes the influent to stabilize the water quality. Appropriate amounts of acid / alkali are supplied through dosing tank 1-2 in the pH adjustment tank. pH controller 1-3 monitors the wastewater pH changes to meet the initial pH requirements of the conventional Fenton method. Next, the effluent from the pH adjustment tank is pumped into Fenton reaction tank 2-0 through inlet 2-1. Fe(II) and H2 are calculated based on water quality test results. O2 and sodium chloride are added and supplied by the dosing tank 2-5 of the Fenton reaction tank. The mixture is stirred evenly by the stirrer 2-6 of the Fenton reaction tank. Without powering on, a conventional Fenton reaction is initiated under acidic conditions of Fe(II) / H2O2. The conversion rate of orthophosphorus and the total phosphorus content in the wastewater are monitored. After the same amount of time as that for treating organic phosphoric acid wastewater by the electro-Fenton method, the wastewater in the electro-Fenton reaction zone is discharged from the outlet 2-10, and the precipitate is discharged from the precipitation conduit 2-7 and the precipitation outlet 2-8.

[0036] Application Example 1

[0037] The conventional Fenton method of Comparative Example 1 was applied to the treatment of organophosphoric acid wastewater. Hydroxyethylidene diphosphonic acid (HEDP), a model compound of organophosphoric acid, was used as the phosphorus source. The total phosphorus content of the water sample was 6 mg / L. The initial pH of the solution was controlled at 3, and the Fe(II) / H₂O₂ molar ratio was controlled at 0.01-5. The instantaneous mixing of the two induced the Fenton reaction. During operation, the pH of the solution was controlled to change within -5% from the initial pH. After 7 hours of treatment, the highest efficiency of organophosphoric acid to orthophosphoric acid was only 32.1%. Importantly, under the optimal Fe(II) / H₂O₂ molar ratio of 0.33, when the salinity (calculated as sodium chloride) of the water sample was maintained at 5.6, 28.2, 50.0, and 225.7 mM respectively, the orthophosphoric acid conversion rate gradually decreased to negligible levels, and the total phosphorus residue was much greater than 0.4 mg / L, failing to meet the Chinese surface water phosphorus discharge standard (GB 3838-2002). In other words, the conventional Fenton technology has low efficiency in degrading organophosphoric acid and is easily affected by the substrate Cl. - The suppression of interference cannot be considered a good method for treating organophosphate wastewater.

[0038] Application Example 2

[0039] The electro-Fenton-like system described in Example 1 was applied to the treatment of organophosphate wastewater. HEDP, a model organophosphate compound, was used as the phosphorus source. The total phosphorus content of the water sample was 6 mg / L. The initial pH of the solution was adjusted to 3.5, the Fe(II) / HEDP molar ratio was adjusted to 18.2:1, and the current density was adjusted to 4.3 mA / cm². 2 The salinity (calculated as sodium chloride) of the water samples was maintained at 5.6, 28.2, 50.0, and 225.7 mM, respectively. Electro-Fenton degradation was performed for 7 hours, and the results showed that Cl... - The presence of [a specific substance] significantly promotes the electro-Fenton-like oxidation of organophosphoric acid, significantly increasing the conversion efficiency of organophosphoric acid to orthophosphoric acid to nearly 90%. Only when the salt content is ≥28.2 mM can a conversion efficiency of over 83% of organophosphoric acid to orthophosphoric acid be achieved, and the total phosphorus content of the treated wastewater is <0.4 mg / L, meeting my country's surface water phosphorus discharge standards. The current density was increased to 21.3 mA / cm². 2 Electrolysis for 2 hours can achieve an efficiency of up to 86.4% in converting organic phosphoric acid to orthophosphoric acid. The precipitate collected after electro-Fenton oxidation was then dried and characterized by X-ray photoelectron spectroscopy (XPS). The full XPS spectrum showed elemental peaks corresponding to P 2p. A distinct characteristic peak of 133.3 eV, associated with +5 valence P, was observed in the high-resolution narrow spectrum of P 2p, indicating that orthophosphoric acid exists in its oxidized state on the collected solid. This conclusion is supported by Raman spectroscopy, where the Raman spectral activity of the collected precipitate is mainly due to the presence of phosphate groups (PO4). 3- The frequency shift and vibrational stretching modes revealed information about the internal phosphate groups. XPS and Raman analysis confirmed that the organophosphate in the wastewater was ultimately converted into orthophosphate in the precipitate and recovered. These results indicate that the electro-Fenton-like system of Example 1 is a good method for treating organophosphate wastewater.

[0040] Application Example 3

[0041] The electro-Fenton-like system described in Example 1 was applied to the treatment of organophosphate wastewater. HEDP, a model organophosphate compound, was used as the phosphorus source. The total phosphorus content of the water sample was 6 mg / L. The initial pH of the solution was adjusted to 3.5, the Fe(II) / HEDP molar ratio was adjusted to 18.2:1, and the current density was adjusted to 4.3 mA / cm². 2 The background matrix of the wastewater was determined using the effluent quality parameters from the aerobic biological treatment tank in the textile dyeing and printing wastewater treatment process, specifically: 2.0 mM K. + 168.7mM Na + 1.4mM Ca 2+ 0.5mM Mg 2+ 93.4mM Cl - 2.1mM NO3 - 32.1mM SO4 2-Because the matrix components contain Cl... - The concentration was sufficient to meet the requirements of the electro-Fenton-like reaction, therefore no additional NaCl was added. After 7 hours of electro-Fenton degradation, the orthophosphorus conversion rate was still as high as 88.7%, and the total phosphorus content was reduced to <0.4 mg / L, meeting my country's surface water phosphorus discharge standards. This indicates that the electro-Fenton-like system of Example 1 is still a good method for treating organophosphate wastewater even under complex background substrates.

[0042] In summary, Cl - The effects of traditional Fenton and electro-Fenton-like technologies on the oxidation efficiency of organophosphoric acid show opposite trends. Traditional Fenton technology has lower efficiency in degrading organophosphoric acid and is more susceptible to the influence of substrate Cl. - The invention proposes an electrical Fenton-like technique to suppress interference; this technique can reduce Cl - It is anoly oxidized to HClO, and then reacts with Fe(II) to produce Fe. IV O 2+ Immediately, substrate waste Cl - It is transformed into a selective oxidant, enabling efficient degradation of organophosphates even in complex background matrices. Therefore, the electro-Fenton-like system proposed in this invention, compared to traditional Fenton technology, not only solves the problem of Cl... - Suppressing interference, and even utilizing Cl - This significantly improves the degradation efficiency of organophosphoric acid. Furthermore, the electro-Fenton-like treatment device proposed in this invention has a simple structure, is easy to operate, and has low operating costs. In addition, the organophosphoric acid is ultimately recovered as orthophosphate in the precipitate, which can be used as a raw material for the production of lithium iron phosphate batteries, phosphate fertilizers, or phosphates for beneficial reuse, providing feasibility for the sustainable development of phosphorus resources.

[0043] The above description is merely an example of the embodiments of the present invention and is not intended to limit the scope of protection of the present invention. It should be noted that for those skilled in the art, any omissions, modifications, substitutions, variations, improvements, etc., made within the substantive scope of the present invention patent will be included within the scope of protection of the present invention patent.

Claims

1. A method for treating organophosphate wastewater using an electro-Fenton-like system, characterized in that, Specifically, it includes the following steps: (1) Organic phosphoric acid wastewater is pumped into pH adjustment tank through the inlet of pH adjustment tank. The pH of the solution is adjusted by adding acid / alkali through pH adjustment tank dosing tank and pH controller. The reagent is fully mixed with wastewater by stirring under pH adjustment tank agitator. (2) The organic phosphoric acid effluent in the pH adjustment tank is pumped into the Fenton reaction tank through the inlet of the Fenton reaction tank. Ferrous sulfate / sodium chloride is added through the dosing tank of the Fenton reaction tank. The power is turned on and the Fenton reaction tank agitator is stirred to start the electro-Fenton reaction. After the treatment meets the standard, the wastewater is discharged through the drain outlet and the precipitate is discharged from the precipitate outlet through the precipitation conduit. The electro-Fenton-like method is carried out using the following electro-Fenton-like treatment system, which includes a pH adjustment zone and an electro-Fenton-like reaction zone: The pH adjustment zone includes a pH adjustment tank, a pH adjustment tank inlet, a pH adjustment tank dosing tank, a pH controller, a pH adjustment tank partition, and a pH adjustment tank agitator; the pH adjustment tank inlet receives organic phosphoric acid wastewater via a pump; the pH adjustment tank dosing tank and the pH controller are both connected to the pH adjustment tank; the pH adjustment tank partition is located on the left side of the pH adjustment tank outlet. The electro-Fenton reaction zone includes a Fenton reaction tank, a Fenton reaction tank inlet, a power supply, an anode plate, a cathode plate, a Fenton reaction tank dosing tank, a Fenton reaction tank agitator, a sedimentation conduit, a sedimentation outlet, a Fenton reaction tank baffle, and a drain outlet. The bottom of the Fenton reaction tank is designed in a conical shape. The Fenton reaction tank inlet receives effluent from the pH adjustment tank via a pump. The anode plate and cathode plate are arranged parallel to each other perpendicular to the bottom of the reactor and are connected to the positive and negative terminals of the power supply via wires, respectively. The Fenton reaction tank dosing tank is connected to the Fenton reaction tank. The sedimentation conduit connects the sediment to the sedimentation outlet. The Fenton reaction tank baffle is located to the left of the drain outlet. The drain outlet allows the treated wastewater from the Fenton reaction tank to be discharged via a pump. The anode plate is a titanium substrate coated with a ruthenium-iridium oxide electrode, and the cathode plate is a stainless steel electrode.

2. The electric Fenton-like method according to claim 1, characterized in that: Before undergoing an electro-Fenton-like reaction, the pH value of the organic phosphoric acid wastewater should be 3.5, the salt content (based on NaCl) should be 28.2-225.7 mM, and the Fe(H) / organic phosphoric acid molar ratio should be 18.2:

1.

3. The electric Fenton-like method according to claim 1, characterized in that: The required current density for the electro-Fenton process in organic phosphoric acid wastewater is 4.3-21.3 mA / cm³. 2 .

4. The electric Fenton-like method according to claim 1, characterized in that: Phosphorus recovery involves converting organic phosphoric acid into commercially valuable orthophosphate in the precipitate and then recovering it.

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