A process for treating residual organic wastewater from magnesium-phosphate concentrate reverse flotation and subsequent desiliconization.

Abstract

This invention discloses a treatment process and system for residual organic wastewater from reverse flotation and subsequent desilication of demagnesium phosphate concentrate, belonging to the field of wastewater treatment technology. In the reverse flotation and subsequent desilication process of demagnesium phosphate concentrate, the filtrate from the desiliconized phosphate concentrate and tailings is collected and transported to a wastewater collection tank for mixing. An oxide mixture is added to the mixed wastewater and stirred until homogeneous. The mixture is then pumped sequentially into a two-stage series photo-ozone reactor to oxidize the organic matter in the wastewater. After the treated water sample meets the standards, it is returned to the phosphate rock flotation demagnesium removal process. The wastewater treatment system includes a wastewater collection tank, an oxide mixture addition tank, a mixing tank, a two-stage series photo-ozone reactor, and a qualified wastewater storage tower. This wastewater treatment process not only achieves efficient wastewater treatment without secondary pollution but also allows for reuse in the phosphate rock flotation demagnesium removal process, improving the practicality and stability of the wastewater treatment process and demonstrating promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a process and system for treating residual organic wastewater from magnesium phosphate concentrate reverse flotation and desiliconization. Background Technology

[0002] Demagnesium-phosphate concentrate is a non-metallic mineral product with P2O5 as its main component. When its grade reaches 28%, it can be used as an important raw material for the production of general phosphorus-related fertilizers and compound fertilizers, as well as wet-process phosphoric acid production. However, in order to broaden the types of phosphorus products and produce high-value calcium diphosphate products, it is often necessary to perform reverse flotation and desilication on the demagnesium-phosphate concentrate to increase the P2O5 grade to above 32%.

[0003] In related technologies, the main methods for desilication of magnesium-phosphate concentrate include direct flotation, reverse flotation, combined forward and reverse flotation, and direct-reverse flotation. Anionic or cationic organic reagents are generally used as collectors. After flotation, desilication concentrate and tailings are obtained. These are then filtered to produce filtrate containing residual desilication organic reagents. Because the magnesium-phosphate concentrate slurry contains 10-40% water, the water volume in the desilication system cannot maintain equilibrium, resulting in a surplus of water containing desilication reagents. This surplus water contains desilication reagents that can adversely affect upstream magnesium removal or the natural environment, becoming wastewater that must be treated before being returned to the magnesium removal process. Wastewater is often treated using natural degradation, biodegradation, evaporation, and calcination processes. However, these processes are either time-consuming, incompletely degrade the wastewater, have high treatment costs, or generate secondary pollution, indirectly increasing the production cost of desilication of magnesium-phosphate concentrate. Meanwhile, phosphate rock releases calcium and magnesium phosphate ions during flotation, which severely interferes with wastewater treatment. Therefore, there is an urgent need to research a low-cost, time-efficient, and environmentally friendly wastewater treatment process.

[0004] In the prior art, CN201510129375.2 describes a method for reducing the chemical oxygen demand (COD) of wastewater from zeolite molecular sieve production. The technical objective of this method is to degrade at least one of the following in the wastewater: quaternary ammonium salts (e.g., tetrapropylammonium bromide), quaternary ammonium bases (e.g., tetrapropylammonium hydroxide), and organic amines (e.g., ethylamine, diethylamine, n-butylamine). This effectively reduces the COD value of the wastewater. The technical solution involves adding hydrogen peroxide to the zeolite molecular sieve production wastewater. Under ultraviolet light irradiation, hydroxyl radicals with strong oxidizing power are generated, thereby oxidizing and degrading the organic nitrogen-containing compounds in the wastewater. These organic nitrogen-containing compounds are one or more of the quaternary ammonium salts, quaternary ammonium bases, and organic amines.

[0005] However, technical solutions similar to the above-mentioned solutions cannot solve the problem of the present invention. Due to the complex composition of residual organic wastewater from the demagnesium phosphate concentrate after desiliconization, ordinary treatment processes and technologies cannot meet the requirements. The treatment process and system of the present invention can treat residual organic wastewater from the demagnesium phosphate concentrate after desiliconization that cannot be treated by ordinary reagents and ordinary treatment processes.

[0006] Therefore, the proposed method utilizes clean, pollution-free ultraviolet light to catalyze the oxidation and degradation of wastewater by hydrogen peroxide and persulfate, and to excite ozone. The horizontal ultraviolet reactor can excite hydrogen peroxide and persulfate with ultraviolet light to rapidly release strong oxidizing free radicals and non-free radicals, thereby oxidizing organic matter. The horizontal ultraviolet-ozone reactor can excite the remaining hydrogen peroxide and persulfate with strong oxidizing free radicals and non-free radicals with high-energy deep ultraviolet light, while high-energy ultraviolet light excites oxygen in the water to release ozone. The synergistic effect of free radicals, non-free radicals, and ozone can further oxidize the residual reagents, making it environmentally friendly and highly efficient. This method solves the problem of inefficient treatment of residual organic wastewater from magnesium phosphate concentrate reverse flotation and desilication in existing technologies. Summary of the Invention

[0007] The purpose of this invention is to provide a process and system for treating residual organic wastewater from reverse flotation and desilication of magnesium-phosphate concentrate. This process not only achieves efficient wastewater treatment without secondary pollution, but also allows the wastewater to be reused in the magnesium removal process of phosphate rock flotation, thus improving the practicality and stability of the wastewater treatment process and showing good application prospects.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A process for treating residual organic wastewater from reverse flotation and subsequent desilication of magnesium-phosphate concentrate includes the following steps:

[0010] Step S1: Collect the filtrate from the desiliconized phosphate concentrate and desiliconized tailings after pressure filtration in the reverse flotation and desiliconization process of the demagnesium phosphate concentrate and transport it to the wastewater collection tank for mixing. Add the oxide mixture to the mixed wastewater and stir evenly.

[0011] Step S2: The mixed wastewater obtained in step S1 is pumped sequentially into the first-stage photocatalytic reactor and the second-stage ozone photocatalytic reactor to oxidize the organic matter in the wastewater. The wastewater is treated by repeating steps S1 and S2 n times. After the treated water sample passes the test, it is returned to the phosphate rock flotation demagnesification process for recycling.

[0012] In step S1, the oxide mixture is a mixture of hydrogen peroxide and persulfate.

[0013] Furthermore, the concentration of the oxide mixture is 1.2-20 L per ton of wastewater.

[0014] Furthermore, in step S2, the mixed wastewater is sequentially pumped into the first-stage photocatalytic reactor and the second-stage ozone photocatalytic reactor at a flow rate of 5-18 m³ / h. 3 / h; reaction treatment 0.1-10 h.

[0015] Furthermore, in step S2, n≥1.

[0016] Furthermore, in step S1, the residual organic reagent components in the filtrate after pressure filtration of the desilication phosphate concentrate and desilication tailings in the reverse flotation and desilication process of the demagnesium phosphate concentrate are one or more of the following: oleic acid, sodium oleate, dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, and dodecylamine; the filtrate also contains calcium ions, magnesium ions, phosphate ions, and carbonate ions dissolved during ore flotation.

[0017] Furthermore, in the hydrogen peroxide and persulfate mixture, the hydrogen peroxide content is 15%-40% by mass, the persulfate content is 10%-50% by mass, and the remainder is water. The persulfate is one or more of potassium persulfate, sodium persulfate, potassium persulfate, and sodium persulfate.

[0018] Furthermore, in step S2, the first-stage photocatalytic reactor and the second-stage ozone photocatalytic reactor are arranged in the following order: a horizontal ultraviolet light reactor with a wavelength of 254 nm is connected in series, followed by a horizontal ultraviolet-ozone reactor with a wavelength of 185 nm. The volume of each horizontal photoreactor is 1.0 m³. 3 .

[0019] Furthermore, in step S2, the horizontal ultraviolet light reactor with a light wavelength of 254 nm consists of 15 ultraviolet lamps, each 320W, with a wavelength of 254 nm; the horizontal ultraviolet light-ozone reactor with a light wavelength of 185 nm consists of 28 ultraviolet lamps, each 320W, with a wavelength of 185 nm.

[0020] Furthermore, the standard for qualified wastewater testing in step S2 is: the chemical oxygen demand (COD) of the residual reagent in the wastewater decreases to 150 mg / L or below, which is considered to meet the treatment requirements, and the treated wastewater can enter the reverse flotation magnesium removal process.

[0021] A system for treating residual organic wastewater from reverse flotation and desilication of magnesium phosphate concentrate includes: a wastewater collection tank, an oxide mixture addition tank, a mixing tank, a pumping device, a first-stage photocatalytic oxidation reactor, a second-stage ozone photocatalytic reactor, a qualified wastewater storage tower, a return water pump, and a drainage pump.

[0022] The wastewater collection tank is connected to the mixing tank via valves and a water pump. The oxide mixture addition tank and the mixing tank are connected via a connecting pipe and a feeding pump. The peroxide mixture is pumped into the mixing tank, and the oxide mixture and waste liquid are fully mixed in the mixing tank to obtain a mixture.

[0023] The mixing tank and the two-stage photocatalytic oxidation reactor are connected by a connecting pipe and a water pump. The mixed liquid is pumped into the first-stage photocatalytic oxidation reactor and the second-stage ozone photocatalytic reactor in sequence. The oxide mixture and wastewater react in the first-stage photocatalytic oxidation reactor and the second-stage ozone photocatalytic reactor to obtain treated wastewater.

[0024] The second-stage ozone photocatalytic reactor and the qualified wastewater storage tower are connected one by one through connecting pipes and valve controllers, and qualified wastewater is pumped into the qualified wastewater storage tower.

[0025] Each qualified wastewater storage tower is connected to a mixing tank via a connecting pipe and a return water pump. When the wastewater treatment is unqualified, it can be recycled through this loop for photocatalytic oxidation. The qualified wastewater storage towers are connected in series and parallel to maximize and flexibly accommodate the qualified wastewater or achieve the photocatalytic oxidation recycling capacity. Each qualified wastewater storage tower is connected to the phosphate rock reverse flotation demagnesification process via a connecting pipe and a drainage pump, and the qualified wastewater is pumped into the phosphate rock reverse flotation demagnesification process.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) The process for treating residual organic wastewater from demagnesium phosphate concentrate and desiliconization of the present invention utilizes clean ultraviolet light to catalyze the pollution-free hydrogen peroxide and persulfate and to activate ozone to oxidize and degrade the wastewater. The horizontal ultraviolet reactor can activate hydrogen peroxide and persulfate with ultraviolet light to quickly release strong oxidizing free radicals and non-free radicals to oxidize organic matter. The horizontal ultraviolet-ozone reactor can activate the remaining hydrogen peroxide and persulfate with strong oxidizing free radicals and non-free radicals with high-energy deep ultraviolet light. At the same time, high-energy ultraviolet light activates oxygen in the water to release ozone. Free radicals, non-free radicals and ozone work together to further oxidize the residual reagents. It has environmentally friendly and efficient applicability. Since the composition of residual organic wastewater from demagnesium phosphate concentrate and desiliconization of the present invention is complex, ordinary treatment processes and procedures cannot meet the requirements. The treatment process and system of the present invention can treat residual organic wastewater from demagnesium phosphate concentrate and desiliconization of the present invention that cannot be treated by ordinary reagents and ordinary treatment processes.

[0028] (2) The process for treating residual organic wastewater from desilication of magnesium phosphate concentrate and desiliconization of the present invention can not only treat desiliconized concentrate filter wastewater or desiliconized tailings filter wastewater separately, but also treat combined desiliconized concentrate and tailings filter wastewater, which has high practicality.

[0029] (3) The residual organic wastewater treatment system for demagnesium phosphate concentrate and desiliconization of the present invention is simple in equipment, easy to operate, and has good stability.

[0030] The main innovation of this invention lies in the use of a first-stage photocatalytic oxidation reactor and a second-stage ozone photocatalytic reactor connected in series. By using ultraviolet light to catalyze the generation of active groups from a mixture of hydrogen peroxide and persulfate, ultraviolet light to excite ozone, and ultraviolet light itself to oxidize and decompose residual organic reagents, this method not only reduces wastewater treatment time but is also environmentally friendly, produces no secondary pollution, and simplifies the wastewater treatment system. It effectively reduces the production cost of desilication of magnesium phosphate concentrate and solves the problem of residual organic wastewater from desilication of magnesium phosphate concentrate that cannot be treated by ordinary reagents and ordinary treatment processes in the existing technology. Attached Figure Description

[0031] Figure 1 This is a general flow chart of the wastewater treatment process in an embodiment of the present invention;

[0032] The components include: 1. Wastewater collection tank; 2. Control valve a; 3. Water pump; 4. Connecting pipe; 5. Oxide mixture addition tank; 6. Feed pump; 7. Mixing tank; 8. Water pump; 9. Control valve b; 10. First-stage photocatalytic reactor; 11. Second-stage ozone photocatalytic reactor; 12. Qualified wastewater storage tower a; 13. Control valve 3; 14. Control valve c; 15. Control valve d; 16. Qualified wastewater storage tower b; 17. Control valve e; 18. Control valve f; 19. Control valve h; 20. Qualified wastewater storage tower c; 21. Control valve i; 22. Control valve j; 23. Drain pump; 24. Drain pipe; 25. Control valve k; 26. Control valve m; 27. Control valve n; 28. Return water pipe; 29. ​​Return water pump. Detailed Implementation

[0033] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0034] Wastewater source in the example:

[0035] The demagnesia-phosphate concentrate is a product obtained by hydrocyclone classification, containing more than 70% +38 μm mesh. During flotation desilication, the pulp concentration is 20%-30%, the pH is 4-8, and the temperature is 20-35℃. The P2O5 content is 25-30%, and the mass fraction ratio (MER value) of sesquioxides [ω(Fe2O3)+ω(Al2O3)+ω(MgO)] / ω(P2O5) is ≥0.33. Reverse flotation of the demagnesia-phosphate concentrate is performed using a flotation reagent solution. The reverse flotation reagent solution raw materials include water and reagents, with water as the solvent and reagents as the solute. The flotation reagent solution contains 5-50% flotation reagents by mass concentration, and the reagent dosage is 500 g / t dry basis demagnesia-phosphate concentrate.

[0036] The desilication concentrate has a P2O5 grade of ≥32% and a MER value of ≤0.10.

[0037] The process involves reverse flotation desilication of magnesium-phosphate concentrate, pressure filtration dewatering of desilication concentrate, and pressure filtration dewatering of desilication tailings, wherein the desilication concentrate pressure filtration dewatering rate is ≥87%, and the desilication tailings pressure filtration dewatering rate is ≥80%. Wastewater includes desilication concentrate filtrate and desilication tailings filtrate.

[0038] The embodiments and comparative examples described in this invention all adopt... Figure 1 The wastewater treatment process shown in the figure is used for wastewater treatment.

[0039] Example 1:

[0040] The desilication wastewater collected at a flotation reagent dosage of 500 g / t was used as the treatment target, and the flow rate was controlled at 5 m³ / t. 3 The concentration of hydrogen peroxide and sodium persulfate mixture was 1.2 L / h (hydrogen peroxide mass content 15%, sodium persulfate mass 50%, the remainder being water). A first-stage horizontal photoreactor (15 UV lamps, 320W each, wavelength 254 nm) and a second-stage horizontal photo-ozone reactor (28 UV lamps, 320W each, wavelength 185 nm) were used in series for treatment. In one cycle, the first-stage horizontal photoreactor treated for 9.5 minutes, and the second-stage horizontal photo-ozone reactor treated for 14 minutes. Water samples were taken after each cycle to test the COD. The results showed that after the first treatment, the COD value decreased from 466 mg / L to 136 mg / L, with a COD removal rate of 70.8%. The effluent had no impact on the magnesium flotation index and met the national industrial wastewater discharge standard GB8978-1996, Class II standard (≤150 mg / L).

[0041] Example 2:

[0042] The desilication wastewater collected at a flotation reagent dosage of 500 g / t was used as the treatment target, and the flow rate was controlled at 18 m³ / t. 3The concentration of the hydrogen peroxide and sodium persulfate mixture was 6 L / h (hydrogen peroxide content 40%, sodium persulfate content 10%, the remainder being water). A first-stage horizontal photoreactor (15 UV lamps, 320W each, wavelength 254 nm) and a second-stage horizontal photo-ozone reactor (28 UV lamps, 320W each, wavelength 185 nm) were used in series for treatment. In one cycle, the first-stage photoreactor treated for 9.5 minutes, and the second-stage photo-ozone reactor treated for 14 minutes. Water samples were taken after each cycle to test the COD. The results showed that after the first treatment, the COD value decreased to 122 mg / L, the COD removal rate was 73.8%, the effluent had no impact on the magnesium flotation index, and met the national industrial wastewater discharge standard GB8978-1996 Class II standard (≤150 mg / L).

[0043] Example 3:

[0044] The desilication wastewater collected at a flotation reagent dosage of 500 g / t was used as the treatment target, and the flow rate was controlled at 10 m³ / t. 3 The concentration of hydrogen peroxide and sodium persulfate mixture was 20 L / h (hydrogen peroxide mass content 25%, sodium persulfate mass content 30%, the remainder being water). A first-stage horizontal photoreactor (15 UV lamps, 320W each, wavelength 254 nm) and a second-stage horizontal photo-ozone reactor (28 UV lamps, 320W each, wavelength 185 nm) were used in series for treatment. In one cycle, the first-stage horizontal photoreactor treated for 9.5 minutes, and the second-stage horizontal photo-ozone reactor treated for 14 minutes. Water samples were taken after each cycle to test the COD. The results showed that after the first treatment, the COD value decreased from 466 mg / L to 89 mg / L, with a COD removal rate of only 80.9%. The effluent had no impact on the magnesium flotation index and met the national industrial wastewater discharge standard GB8978-1996, Class II standard (≤150 mg / L).

[0045] Comparative Example 1:

[0046] The desilication wastewater collected at a flotation reagent dosage of 500 g / t was used as the treatment target, and the flow rate was controlled at 10 m³ / t. 3The hydrogen peroxide dosage was 20 L / h (55% hydrogen peroxide, the remainder water). A first-stage horizontal photoreactor (15 UV lamps, 320W each, 254 nm wavelength) and a second-stage horizontal photo-ozone reactor (28 UV lamps, 320W each, 185 nm wavelength) were used in series for treatment. In one cycle, the first-stage photoreactor treated for 9.5 minutes, and the second-stage photo-ozone reactor treated for 14 minutes. Water samples were taken after each cycle to test the COD. The results showed that after the first treatment, the COD value decreased from 466 mg / L to 322 mg / L, with a COD removal rate of only 30.9%; after the second cycle, the COD value decreased to 223 mg / L, with a COD removal rate of 52.1%; and after the third cycle, the COD value decreased to 164 mg / L, with a COD removal rate of 64.8%. The effect of single-stage hydrogen peroxide catalytic oxidation of desilication reagent wastewater was unsatisfactory.

[0047] Comparative Example 2:

[0048] The desilication wastewater collected at a flotation reagent dosage of 500 g / t was used as the treatment target, and the flow rate was controlled at 10 m³ / t. 3 The sodium persulfate concentration was 20 L / h (55% sodium persulfate, the remainder being water). A first-stage horizontal photoreactor (15 UV lamps, 320W each, wavelength 254 nm) and a second-stage horizontal photo-ozone reactor (28 UV lamps, 320W each, wavelength 185 nm) were connected in series for treatment. In one cycle, the first-stage horizontal photoreactor treated for 9.5 minutes, and the second-stage horizontal photo-ozone reactor treated for 14 minutes. Water samples were taken after each cycle to test the COD. The results showed that after the first treatment, the COD value decreased from 466 mg / L to 316 mg / L, with a COD removal rate of only 32.2%; after the second treatment, the COD value decreased to 212 mg / L, with a COD removal rate of 54.5%; after the third treatment, the COD value decreased to 148 mg / L, with a COD removal rate of 68.2%. The effluent had no impact on the magnesium flotation index and met the national industrial wastewater discharge standard GB8978-1996 Class II standard (≤150 mg / L).

[0049] Comparative Example 3:

[0050] The desilication wastewater collected at a flotation reagent dosage of 500 g / t was used as the treatment target, and the flow rate was controlled at 10 m³ / t. 3The concentration of hydrogen peroxide and sodium persulfate mixture was 20 L / h (hydrogen peroxide 25% by mass, sodium persulfate 30% by mass, the remainder being water). Treatment was carried out using a single-stage horizontal photocatalytic reactor (15 UV lamps, each 320W, wavelength 254 nm) for 23.5 minutes. Water samples were taken after each cycle to test COD. Results showed that after the first treatment, the COD value decreased from 466 mg / L to 327 mg / L, with a COD removal rate of only 29.8%; after the second cycle, the COD value decreased to 248 mg / L, with a COD removal rate of 46.8%; and after the third cycle, the COD value decreased to 182 mg / L, with a COD removal rate of 60.9%. The single-stage horizontal photocatalytic reaction was ineffective in treating wastewater from desilication reagent treatment.

[0051] Comparative Example 4:

[0052] The desilication wastewater collected at a flotation reagent dosage of 500 g / t was used as the treatment target, and the flow rate was controlled at 10 m³ / t. 3 The concentration of hydrogen peroxide and sodium persulfate mixture was 20 L / h (hydrogen peroxide 25% by mass, sodium persulfate 30% by mass, the remainder being water). Treatment was carried out using a second-stage horizontal photo-ozone reactor (28 UV lamps, each 320W, wavelength 185 nm) for 23.5 minutes. Water samples were taken after each cycle to test COD. Results showed that after the first treatment, the COD value decreased from 466 mg / L to 344 mg / L, with a COD removal rate of only 26.2%; after the second cycle, the COD value decreased to 257 mg / L, with a COD removal rate of 44.8%; and after the third cycle, the COD value decreased to 198 mg / L, with a COD removal rate of 57.5%. The single two-stage horizontal photo-ozone catalytic reaction was ineffective in treating wastewater from desilication reagent treatment.

[0053] Comparative Example 5:

[0054] The desilication wastewater collected at a flotation reagent dosage of 500 g / t was used as the treatment target, and the flow rate was controlled at 10 m³ / t. 3The treatment was conducted at a rate of 20 L / h (55% hydrogen peroxide, the remainder being water) using a first-stage horizontal photoreactor (15 UV lamps, each 320W, wavelength 254 nm) for 23.5 minutes. Water samples were taken after each cycle to test COD. Results showed that after the first treatment, the COD value decreased from 466 mg / L to 389 mg / L, with a COD removal rate of only 16.5%. After the second cycle, the COD value decreased to 337 mg / L, with a COD removal rate of 27.7%. After the third cycle, the COD value decreased to 302 mg / L, with a COD removal rate of 35.2%. After the seventh cycle, the COD value decreased to 211 mg / L, with a COD removal rate of 54.7%.

[0055] Comparative Example 6:

[0056] The desilication wastewater collected at a flotation reagent dosage of 500 g / t was used as the treatment target, and the flow rate was controlled at 10 m³ / t. 3 The treatment was carried out at a rate of 20 L / h (55% sodium persulfate, the remainder being water) using a second-stage horizontal photo-ozone reactor (28 UV lamps, each 320W, wavelength 185 nm), with a treatment time of 23.5 minutes. Water samples were taken after each cycle to test the COD. Results showed that after the first treatment, the COD value decreased from 466 mg / L to 367 mg / L, with a COD removal rate of only 21.2%; after the second cycle, the COD value decreased to 288 mg / L, with a COD removal rate of 38.2%; after the third cycle, the COD value decreased to 232 mg / L, with a COD removal rate of 50.2%; and after the seventh cycle, the COD value decreased to 155 mg / L, with a COD removal rate of 66.7%.

[0057] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A process for treating residual organic wastewater from reverse flotation and subsequent desilication of magnesium-phosphate concentrate, characterized in that: Includes the following steps: Step S1: Mix the wastewater from the desiliconized phosphate concentrate and the desiliconized tailings after pressure filtration in the reverse flotation and desiliconization process of the demagnesium phosphate concentrate, add the oxide mixture, and stir evenly; the oxide mixture is a mixed solution of hydrogen peroxide and persulfate. Step S2: Pump the material that was stirred evenly in step S1 into the first-stage photocatalytic reactor and the second-stage ozone photocatalytic reactor in sequence to oxidize the organic matter in the wastewater. Repeat steps S1 and S2 n times. Once the treated water sample passes the test, return it to the phosphate rock flotation demagnesification process. n is greater than or equal to 1; The first-stage photocatalytic reactor and the second-stage ozone photocatalytic reactor in step S2 are arranged in the following order: a horizontal ultraviolet light reactor with a wavelength of 254 nm is connected in series, followed by a horizontal ultraviolet light-ozone reactor with a wavelength of 185 nm. The standard for qualified water samples after treatment is that the chemical oxygen demand (COD) value decreases to 150 mg / L or below.

2. The wastewater treatment process according to claim 1, characterized in that: In step S1, the amount of oxide mixture added per ton of wastewater is 1.2-20 L.

3. The wastewater treatment process according to claim 1, characterized in that: In step S2, when the well-stirred material is pumped into the reactor, the flow rate is 5-18 m³ / h. 3 / h; reaction treatment 0.1-10 h.

4. The wastewater treatment process according to claim 1, characterized in that: In step S1, the residual organic matter in the wastewater is at least one of oleic acid, sodium oleate, dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, and dodecylamine.

5. The wastewater treatment process according to claim 1, characterized in that: In step S1, the mass percentage of hydrogen peroxide in the oxide mixture is 15%-40%, the mass percentage of persulfate is 10%-50%, and the remainder is water; the persulfate is at least one of potassium persulfate, sodium persulfate, potassium persulfate, and sodium persulfate.

6. The wastewater treatment process according to claim 1, characterized in that: The horizontal ultraviolet reactor and the horizontal ultraviolet-ozone reactor both have a volume of 1.0 m³. 3 .

7. The wastewater treatment process according to claim 1, characterized in that: The horizontal ultraviolet light reactor with a wavelength of 254 nm consists of 15 ultraviolet lamps, each 320W, with a wavelength of 254 nm; the horizontal ultraviolet light-ozone reactor with a wavelength of 185 nm consists of 28 ultraviolet lamps, each 320W, with a wavelength of 185 nm.

8. A system for treating residual organic wastewater from reverse flotation and subsequent desilication of magnesium-phosphate concentrate as described in claim 1, characterized in that: The residual organic wastewater treatment system includes: a wastewater collection tank, an oxide mixture addition tank, a mixing tank, a pumping device, a first-stage photocatalytic reactor, a second-stage ozone photocatalytic reactor, a qualified wastewater storage tower, a return water pump, and a drainage pump. The wastewater collection tank is connected to the mixing tank via valves and a water pump. The oxide mixture addition tank and the mixing tank are connected via a connecting pipe and a feeding pump. The oxide mixture and wastewater are thoroughly mixed in the mixing tank. The mixing tank and the two-stage reactor are connected by a connecting pipe and a water pump. The mixed oxide mixture and wastewater are pumped into the first-stage photocatalytic reactor and the second-stage ozone photocatalytic reactor in sequence to carry out the oxidation reaction. The second-stage ozone photocatalytic reactor and the qualified wastewater storage tower are connected by a connecting pipe and a control valve, and the treated wastewater is pumped into the qualified wastewater storage tower. Each qualified wastewater storage tower is connected to the mixing tank via a connecting pipe and a return water pump. When the wastewater treatment is unqualified, it is recycled through this loop for photocatalytic oxidation. Multiple qualified storage towers are connected in series and parallel to maximize and flexibly accommodate qualified wastewater or achieve photocatalytic oxidation recycling capacity. Each qualified wastewater storage tower is connected to the phosphate rock reverse flotation demagnesification process via a connecting pipe and a drainage pump, and qualified wastewater is pumped into the phosphate rock reverse flotation demagnesification process.

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