Method and application for simultaneously oxidizing and flocculating to remove low-valent phosphorus in wastewater by using an aluminum-based composite agent

Abstract

The present invention provides a method for simultaneously oxidizing and flocculating low-valent phosphorus in wastewater by using an aluminum-based composite agent. Aluminum powder and ferric salts are subjected to ball milling treatment under an inert atmosphere. In the ball-milled material, the surface oxide layer of zero-valent aluminum is destroyed and ferrous salts are generated simultaneously. Zero-valent aluminum and ferric salts couple to activate molecular oxygen and generate strongly oxidizing free radicals and ferric ions. The strongly oxidizing free radicals oxidize hypophosphite ions in the wastewater to phosphite ions, and the ferric ions synergistically oxidize the phosphite ions to orthophosphate ions. In acidic wastewater, aluminum rapidly dissolves and together with ferric salts generates flocs to remove orthophosphate ions through flocculation precipitation, achieving efficient simultaneous oxidation and flocculation removal of low-valent phosphorus in nickel-plating wastewater. The present invention also provides the application of the above method in treating low-valent phosphorus-containing wastewater such as nickel-plating wastewater. The materials of the present invention are widely sourced and low in cost, and the material preparation method is simple, greatly simplifying the treatment process flow and being easy to apply in engineering.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial wastewater treatment, and particularly relates to a method for synchronously oxidizing and flocculating low-valent phosphorus in wastewater by using an aluminum-based composite agent, and also relates to the application of the above method in treating low-valent phosphorus-containing wastewater generated in chemical production fields such as nickel plating. Background Art

[0002] Sodium hypophosphite is widely used in chemical production fields such as flame retardant production, electroless nickel plating, and electroless copper plating. During the production process, strongly acidic wastewater containing low-valent phosphorus such as hypophosphite (+1 valence) and phosphite (+3 valence) will be generated.

[0003] Different from orthophosphate (+5 valence), low-valent phosphate minerals have higher solubility than orthophosphate minerals, resulting in difficulty in directly removing low-valent phosphorus by chemical precipitation method. In addition, microorganisms have poor metabolic ability for low-valent phosphorus, and low-valent phosphorus in industrial wastewater usually coexists with heavy metal ions such as nickel, copper, and tin, and the biochemical treatment effect is not ideal. Therefore, the conventional treatment method for low-valent phosphorus in wastewater is to add strong oxidants (H2O2, O3) to oxidize it into orthophosphate, and then add alkaline substances (NaOH, CaO) to adjust the pH of the wastewater to weakly alkaline, and then add a flocculant to flocculate and precipitate orthophosphate. However, it is relatively easy to oxidize hypophosphite to phosphite, but it is difficult to oxidize phosphite to orthophosphate by conventional oxidants.

[0004] Advanced oxidation methods generate strongly oxidizing species (·OH or 1 O2) that can complete the transformation of low-valent phosphorus to pentavalent phosphorus, but still need two-step treatment of advanced oxidation combined with chemical precipitation to obtain an ideal effect, and there are problems such as high reagent cost, cumbersome operation, and harsh implementation conditions. In electrochemical treatment, anodic oxidation generates strongly oxidizing species combined with iron salt flocculation and precipitation methods, which have problems such as high energy consumption cost, complex preparation of electrode materials, and service life, and it is also difficult to achieve large-scale application.

[0005] Therefore, developing a new technology to achieve efficient removal of low-valent phosphorus, simplify the low-valent phosphorus treatment method, and reduce the disposal cost has great social benefits and application value. Summary of the Invention

[0006] One of the purposes of the present invention is to provide a method for synchronously oxidizing and flocculating low-valent phosphorus in wastewater by using an aluminum-based composite agent.

[0007] Another purpose of the present invention is to provide the application of a method for synchronously oxidizing and flocculating low-valent phosphorus in wastewater by using an aluminum-based composite agent in treating low-valent phosphorus-containing wastewater generated in chemical production fields such as nickel plating.

[0008] One of the technical solutions adopted by the present invention to achieve its purpose is to provide a method for synchronously oxidizing and flocculating to remove low-valent phosphorus in wastewater with an aluminum-based composite agent, comprising the following steps:

[0009] Place aluminum powder and ferric salt under an inert atmosphere for ball milling treatment to obtain an aluminum-based composite agent;

[0010] Add the aluminum-based composite agent to the wastewater containing low-valent phosphorus and react for a certain time under aerobic conditions; in this reaction, hypophosphite and / or phosphite are oxidized to orthophosphate and removed in the form of flocculation precipitation.

[0011] The general idea of a method for synchronously oxidizing and flocculating to remove low-valent phosphorus in wastewater with an aluminum-based composite agent provided by the present invention is as follows:

[0012] The present invention uses aluminum powder and ferric salt as raw materials to prepare an aluminum-based composite agent by means of ball milling treatment under an inert atmosphere. During the high-energy mechanical collision process of aluminum powder, iron salt, and ball milling beads, the surface of zero-valent aluminum metal will be severely abraded, destroying the dense oxide layer on the surface of zero-valent aluminum and prompting zero-valent aluminum to expose a fresh surface.

[0013] As shown in Formula 1, during the ball milling process, after partial ferric salt comes into full contact with the fresh surface of zero-valent aluminum exposed, a chemical reaction occurs to form divalent iron. Ferric iron and divalent iron will adhere to the surface of zero-valent aluminum. On the one hand, it can effectively prevent zero-valent aluminum from undergoing cold welding effect to form a flaky structure. On the other hand, it can also hinder the direct contact between zero-valent aluminum and oxygen and prevent the formation of a continuous and dense oxide layer on the surface of zero-valent aluminum.

[0014] When the aluminum-based composite agent containing zero-valent aluminum enters the wastewater containing low-valent phosphorus, under aerobic conditions, zero-valent aluminum activates molecular oxygen and rapidly generates strong oxidizing species such as ·OH and ·O2 - etc. On the one hand, it can quickly oxidize hypophosphite in the wastewater to phosphite. On the other hand, the strong oxidizing species will oxidize ferric iron to high-valent iron (Ⅳ, Ⅴ, Ⅵ), and the high-valent iron will be beneficial to the process of selectively oxidizing phosphite to orthophosphate. At the same time, the ionization equilibrium between the dissolved aluminum and its hydrolysis products will cause the pH of the wastewater to gradually rise, and the flocs such as dissolved aluminum salts and iron salts will flocculate and precipitate phosphates, achieving the effect of removing low-valent phosphorus in the wastewater in the form of flocculation. The method provided by the present invention not only realizes the one-step oxidation-flocculation high-efficiency treatment of low-valent phosphorus but also can adjust the pH of strongly acidic wastewater, which is beneficial to the subsequent treatment of the wastewater.

[0015] Specifically, when the aluminum-iron salt composite material enters strongly acidic wastewater to oxidize and flocculate low-valent phosphates, it mainly undergoes the reaction process of the following three stages:

[0016] (1) As shown in Formula 2-4, zero-valent aluminum after ball milling activates oxygen to produce hydrogen peroxide. Zero-valent aluminum and divalent iron salts produce strongly oxidizing species under acidic conditions, oxidizing hypophosphite (+1) to phosphite (+3), and oxidizing species such as ·OH will further oxidize trivalent iron to high-valent iron;

[0017] (2) As shown in Formula 5-9, high-valent iron and oxidizing species further oxidize phosphite (+3) to orthophosphate (+5), and as the reaction proceeds, aluminum gradually dissolves, and aluminum and its various hydrolysis products can gradually adjust the solution pH;

[0018] (3) As shown in Formula 9-11, aluminum salt and iron salt flocs flocculate and precipitate orthophosphate. Through the above process, the aluminum-iron salt composite material realizes the efficient removal of low-valent phosphate by oxidation and flocculation, and adjusts the pH of the wastewater to weakly alkaline.

[0019] Al + 3Fe 3+ =Al 3+ + 3Fe 2+ (Formula 1)

[0020] 2Al + 3O2 + 6H + =2Al 3+ + 3H2O2 (Formula 2)

[0021] Al + H2O2 = Al 3+ + 3·OH + 3OH - (Formula 3)

[0022] Fe 2+ + H2O2 = Fe 3+ + ·OH + OH - (Formula 4)

[0023] H2PO2 - + 2·OH = HPO3 2- + H2O + H + (Formula 5)

[0024] HPO3 2- + 2·OH = PO4 3- + H2O + H + (Formula 6)

[0025] HPO3 2- + 2Fe(Ⅳ) + H2O = PO4 3- + 2Fe 3+ + 3H + (Formula 7)

[0026] HPO3 2- + Fe(Ⅴ) + H2O = PO4 3-+Fe 3+ +3H + (Formula 8)

[0027] 3HPO3 2- +2Fe(Ⅵ)+3H2O = 3PO4 3- +2Fe 3+ +9H + (Formula 9)

[0028] nAl 3+ +PO4 3- +(3n - 3)OH - =Al n PO4(OH) 3n-3 (s) (Formula 10)

[0029] nFe 3+ +PO4 3- +(3n - 3)OH - =Fe n PO4(OH) 3n-3 (s) (Formula 11)

[0030] In the present invention, the preparation of the aluminum-based composite agent using ferric salts and aluminum powder has the following advantages: on the one hand, some ferric salts as raw materials will generate ferrous salts during the ball milling process, and ferrous salts play a key role in generating strongly oxidizing species such as ·OH; on the other hand, ferric salts dissolve in the solution, playing a key role in the formation of higher-valent iron in the later stage, and can improve the reaction rate of higher-valent iron.

[0031] Preferably, the ferric salts include ferric sulfate and / or ferric chloride.

[0032] Furthermore, in the aluminum-based composite agent, the dosage of ferric iron will affect the ball milling effect and the removal effect of low-valent phosphate. When the content of iron salt is too low, it will lead to insufficient ball milling and limited reaction activity of zero-valent aluminum; while when the content of iron salt is too high, the active metal component is insufficient and there are fewer electrons available to supply activated molecular oxygen. Preferably, the mass ratio of aluminum powder to ferric iron in the ferric salt is (5 - 20):1. More preferably, the mass ratio of aluminum powder to ferric iron in the ferric salt is (10 - 20):1.

[0033] Furthermore, the purity of the aluminum powder is 95% - 99%, and the particle size is 50 - 1000 mesh.

[0034] Furthermore, considering the high-speed ball milling stage of aluminum powder and ferric salts, the collision between the two is extremely intense, the abrasion of the aluminum powder surface is extremely obvious, the particle size of the aluminum powder drops rapidly. If the continuous high-speed ball milling releases heat severely and the material reactivity is extremely strong, it is easy to catch fire spontaneously when opening the lid. Therefore, adopting an intermittent ball milling method can play a role in cooling and preventing spontaneous combustion, ensuring the safe and stable progress of the preparation process.

[0035] In the present invention, the ball milling treatment is carried out in an intermittent manner, and the time interval between two adjacent ball milling treatments is 20 - 40 min. Preferably, the ball milling treatment adopts an intermittent cyclic ball milling method of "starting for half an hour - stopping for half an hour", and is carried out for 1 to 8 cycles.

[0036] Furthermore, the particle size of the ball milling beads for the ball milling treatment is 6 - 20 mm; the feeding mass ratio of the ball milling beads to the material is (20 - 50):1. Preferably, the particle sizes of the ball milling beads include 6 mm, 10 mm, and 15 mm, and the feeding number ratio of the three is 15:5:1.

[0037] Furthermore, the addition amount of the aluminum-based composite agent in the wastewater is 0.1 - 5 g / L. Specifically, it can be adjusted according to the concentration of low-valent phosphorus (hypophosphite + phosphite) in the wastewater, the required controlled reaction time, and the reaction rate.

[0038] Furthermore, the pH of the wastewater is 2 - 6, and the acidic condition is beneficial to the generation of strongly oxidizing substances ·OH and the continuous dissolution of aluminum.

[0039] Furthermore, the reaction under aerobic conditions includes: in an open container, using air as the oxygen source, and promoting the replacement of oxygen in the air and the solution through oscillation or stirring. This method directly uses the oxygen in the air, and by means of oscillation or stirring, etc., promotes the continuous entry of oxygen into the wastewater to participate in the reaction. The oxygen source is extensive, cheap and easy to obtain. Using air as the oxygen source in the present invention has great advantages in terms of usage cost and safety compared with oxidants such as hydrogen peroxide, persulfate, and ozone.

[0040] Furthermore, for the treatment of a large amount of wastewater containing low-valent phosphorus generated in chemical engineering, the reaction under aerobic conditions can also be carried out by continuously injecting an oxygen-containing gas (air or oxygen) into the wastewater using equipment such as a pump.

[0041] The technical solution adopted by the present invention to achieve the second object is: to provide an application of the method according to the first object of the present invention in treating wastewater containing low-valent phosphorus generated in the production process of nickel plating, copper plating, or flame retardants. The low-valent phosphorus in the wastewater exists in the forms of hypophosphite (+1 valence) and phosphite (+3 valence).

[0042] Compared with the prior art, the beneficial effects of the present invention are:

[0043] (1) The method for simultaneously oxidizing and flocculating low-valent phosphorus in wastewater using the aluminum-based composite agent provided by the present invention uses aluminum powder and ferric salts as industrial-grade raw materials. These materials are inexpensive and easily available, can be used on a large scale, effectively control the cost of treating wastewater, and cause no secondary pollution. The ball-milling preparation method of the aluminum-based composite agent is carried out under normal temperature and pressure. The synthesis process is simple and the reaction conditions are mild, which is suitable for industrial production. The source of oxygen is extensive, inexpensive and easily available. In the present invention, air is used as the oxygen source, which has great advantages over oxidants such as hydrogen peroxide, persulfate and ozone in terms of use cost and safety.

[0044] (2) The aluminum-based composite agent prepared by the present invention has strong reaction activity. Under aerobic conditions, it can rapidly oxidize low-valent phosphate, and utilize the oxidation selectivity of high-valent iron to accelerate the oxidation of trivalent phosphorus to pentavalent phosphorus. At the same time, the pH of the wastewater can be adjusted by aluminum dissolution to generate flocs to remove orthophosphate. Compared with the conventional method that requires two steps of "oxidation + flocculation" to remove low-valent phosphorus, the method provided by the present invention greatly simplifies and optimizes the process steps, has a high removal effect, avoids repeated dosing of agents, and reduces the treatment cost.

[0045] (3) The aluminum-based composite agent provided by the present invention can still maintain good metal activity and pollutant removal ability in the actual complex wastewater system. This method is applicable to the treatment of low-valent phosphorus and some organic matters in strongly acidic wastewater generated during the production of nickel plating, copper plating or flame retardants, and has broad prospects for popularization and application. Description of the Drawings

[0046] Figure 1 It is the effect diagram of the composite material for removing hypophosphite in Application Example 1 of the present invention;

[0047] Figure 2 It is the effect diagram of the composite material for treating hypophosphite in Application Example 3 of the present invention; among them, (a) the removal rates of hypophosphite under aerobic, anaerobic and quenching conditions; (b) is the removal of hypophosphite and the change of ABTS ·+ concentration during the aerobic reaction. Detailed Embodiments

[0048] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0049] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0050] The present invention will be further described below in conjunction with specific embodiments, but it is not intended to limit the present invention.

[0051] The raw materials and main parameters involved in the embodiments and comparative examples of the present invention are shown in Table 1 below.

[0052] Table 1

[0053]

[0054] Among the raw materials in the above table, the particle size of aluminum powder is 80 - 150 μm, and the purity is 99%; the purity of other iron salts exceeds 99%.

[0055] Example 1

[0056] Add a total of 70 g of ball milling beads with diameters of 15, 10, and 6 mm to four 100 mL stainless steel ball milling jars in a number ratio of 1:5:15; weigh 2 g of aluminum powder and 0.290 g of anhydrous ferric chloride into the ball milling jars respectively, that is, the mass ratio between aluminum and ferric iron element is 1:0.05, and the mass ratio of ball milling beads to the added materials is 31:1. After sealing the ball milling jars and evacuating, introduce argon as the protective gas, put the ball milling jars into a planetary ball mill, set the rotation speed to 400 rpm, and take running for half an hour and stopping for half an hour as a cycle, and cycle ball mill 3 times. After ball milling, take out the obtained aluminum-iron salt composite material and place it under nitrogen protection.

[0057] Example 2

[0058] Prepare the aluminum-iron salt composite material according to the raw material composition, ratio, ball milling parameters, etc. shown in Table 1, and the other steps are the same as those in Example 1, and the product is placed under nitrogen protection.

[0059] Example 3

[0060] Prepare the aluminum-iron salt composite material according to the raw material composition, ratio, ball milling parameters, etc. shown in Table 1, and the other steps are the same as those in Example 1, and the product is placed under nitrogen protection.

[0061] Example 4

[0062] Add a total of 70 g of ball milling beads with diameters of 15, 10, and 6 mm to four 100 mL stainless steel ball milling jars in a number ratio of 1:5:15; weigh 1.5 g of aluminum powder and 0.268 g of hydrated Fe2(SO4)3 into the ball milling jars respectively, that is, the mass ratio between aluminum and ferric iron element is 1:0.05, and the mass ratio of ball milling beads to the added materials is 40:1. After sealing the ball milling jars and evacuating, introduce argon as the protective gas, put the ball milling jars into a planetary ball mill, set the rotation speed to 300 rpm, and take running for half an hour and stopping for half an hour as a cycle, and cycle ball mill 4 times. After ball milling, take out the obtained aluminum-iron salt composite material and place it under nitrogen protection.

[0063] Example 5

[0064] The aluminum-iron salt composite material was prepared according to the raw material composition, ratio, ball milling parameters, etc. shown in Table 1. The other steps were the same as those in Example 4, and the product was placed under nitrogen protection.

[0065] Example 6

[0066] The aluminum-iron salt composite material was prepared according to the raw material composition, ratio, ball milling parameters, etc. shown in Table 1. The other steps were the same as those in Example 4, and the product was placed under nitrogen protection.

[0067] Comparative Example 1

[0068] The difference between this comparative example and Example 1 is that 0.290 g of anhydrous ferric chloride in Example 1 is replaced by 0.355 g of FeCl2 tetrahydrate, and the other conditions remain unchanged to prepare an aluminum-iron salt composite material, and the product is placed under nitrogen protection.

[0069] Comparative Example 2

[0070] The difference between this comparative example and Example 4 is that 0.268 g of hydrated ferric sulfate in Example 4 is replaced by 0.496 g of FeSO4 heptahydrate, and the other conditions remain unchanged to prepare an aluminum-iron salt composite material, and the product is placed under nitrogen protection.

[0071] Application Example 1

[0072] Pre-aerate the pure water for 30 minutes in advance, and use the pure water to prepare multiple 100mL portions of 1mM H2PO2 - Simulate wastewater and adjust the initial pH of the solution to 3.5 (consistent with the actual nickel plating wastewater). The aluminum-iron salt composite material prepared in Examples 1 and 4, Comparative Examples 1 and 2, and the aluminum powder and iron salt mixture according to the aluminum and iron salt ratios of Examples 1 and 4 (not ball milled, recorded as Al+FeCl3 and Al+Fe2(SO4)3, respectively) are all added into an open conical flask at a dosage of 1g / L. The conical flask is placed in a constant temperature oscillator, the temperature is set to 25°C, the speed is set to 200rpm, and the reaction time is 6h. Take 1mL of samples regularly and filter with a 0.22 micron polyethersulfone filter head, detect the concentrations of hypophosphite and phosphite by ion chromatography, and detect the concentration of orthophosphate by molybdate spectrophotometry.

[0073] Table 2

[0074]

[0075] As shown in Table 2 and Figure 1As shown, the removal rates of hypophosphite radicals in the samples prepared in Comparative Examples 1 and 2 were both lower than 35%, and the removal rates of the mixed addition of Al+FeCl3 and Al+Fe2(SO4)3 were both lower than 15%. However, the removal rates of hypophosphite radicals in the samples such as Al-FeCl3 and Al-Fe2(SO4)3 prepared in Example 1 and Example 4 exceeded 85%. At the same time, the production amounts of +3P and +5P after the reaction were small, indicating that hypophosphite radicals were efficiently oxidized to orthophosphate radicals and then removed by flocculation precipitation.

[0076] Application Example 2

[0077] Pre-aerate pure water for 30 min in advance, and use this pure water to prepare multiple portions of 100 mL of H2PO2 with a concentration of 1 mM - Simulated wastewater (30 - 31 mg P / L), and adjust the initial pH of the solution to 3.5 (consistent with actual nickel plating wastewater). Put the aluminum-iron salt composite materials prepared in Example 2, 3, 5, and 6 into an open conical flask at a dosage of 1 g / L. Place the conical flask in a constant temperature oscillator, set the temperature to 25 °C, the rotation speed to 200 rpm, and the reaction time to 6 h. Take 1 mL of sample at regular intervals and filter it with a 0.22-micron polyethersulfone filter head, and detect the concentrations of hypophosphite radicals and phosphite radicals by ion chromatography, and detect the concentration of orthophosphate radicals by molybdate spectrophotometry.

[0078] Table 3

[0079]

[0080] As shown in Table 3, the removal rates of hypophosphite radicals in the samples prepared in Example 2, 3, 5, and 6 were all higher than 72%, and the production amounts of +3P and +5P after the reaction were small, indicating that hypophosphite radicals were efficiently oxidized to orthophosphate radicals and then removed by flocculation precipitation. In addition, according to the comparison of the test results of Examples 1 - 3 and Examples 4 - 6, as the dosage of ferric salt increased, the removal effect of hypophosphite decreased. In addition, the effect of Al-Fe2(SO4)3 was slightly better than that of Al-FeCl3.

[0081] Application Example 3

[0082] Prepare multiple portions of 100 mL of H2PO2 with a concentration of 1 mM respectively -Simulate the wastewater and adjust the initial pH of the solution to 3.5 (consistent with the actual nickel plating wastewater). It is divided into three groups: anaerobic closed (the water used for solution preparation is treated by deoxygenation and aeration), aerobic open, and aerobic open with methanol added. Add the aluminum-iron salt composite material prepared in Example 4 into the Erlenmeyer flask at a dosage of 1.5 g / L respectively, and the methanol dosage is 0.5 M. Place the Erlenmeyer flask in a constant temperature oscillator, set the temperature at 25 °C, the rotation speed at 200 rpm, and the reaction time at 6 h. Sample 1 mL at regular intervals and filter it with a 0.22-micron polyethersulfone filter head. Detect the concentrations of hypophosphite and phosphite by ion chromatography, detect the concentration of orthophosphate by molybdate spectrophotometry, and detect the concentration of Fe(Ⅵ) by ABTS quenching method.

[0083] As Figure 2 (a) shows that under anaerobic closed conditions, the removal rate of hypophosphite is only 5.9%. In addition, methanol can quench a variety of free radicals. Even under aerobic conditions, the removal rate of hypophosphite is only 4.3%. The above results indicate that the aluminum-iron salt composite material can effectively remove hypophosphite by activating molecular oxygen to generate strong free radicals.

[0084] Figure 2 (b) shows the removal of hypophosphite and the change in ABTS ·+ concentration during the aerobic reaction. As Figure 2 (b) shows, as a probe-type detection substance for Fe(Ⅵ), the yield of ABTS ·+ does not increase significantly in the early stage of the reaction. However, when hypophosphite is almost completely removed, the concentration of ABTS ·+ rises rapidly, indicating that high-valent iron is generated during the reaction and plays a key role in the reaction process of hypophosphite-phosphite-orthophosphate.

[0085] Application Example 4

[0086] Take multiple portions of 100 mL of actual nickel plating wastewater, which contains 1.1 mM H2PO2 - and 0.2 mM HPO3 2- , and the initial pH of the wastewater is 3.5. Add the aluminum-iron salt composite material prepared in Example 4 into the Erlenmeyer flask at dosages of 0.5 g / L, 1 g / L, 1.5 g / L, and 2 g / L respectively. Place the Erlenmeyer flask in a constant temperature oscillator, set the temperature at 25 °C, the rotation speed at 200 rpm, and the reaction time at 6 h. Sample 1 mL at regular intervals and filter it with a 0.22-micron polyethersulfone filter head. Detect the concentrations of hypophosphite and phosphite by ion chromatography, and detect the concentration of orthophosphate by molybdate spectrophotometry.

[0087] Table 4

[0088]

[0089] As shown in Table 4, when the dosage of the Al-Fe2(SO4)3 composite material ranges from 0.5 g / L to 2 g / L, the removal rate of hypophosphite ions can exceed 80%, and with the increase of the dosage, the removal effect of hypophosphite ions gradually increases. When the dosage is 0.5 g / L, the concentration of +5P reaches 1.6 mg P / L. This is because the dosage is relatively small and the solution pH is only 5.9, resulting in a decrease in the flocculation effect. When the dosage is 2 g / L, the removal rate of hypophosphite ions reaches 100%, and the concentrations of phosphite ions and orthophosphate ions in the solution are both lower than 0.1 mg / L.

[0090] The above are only the preferred embodiments of the present invention, and thus do not limit the implementation manners and protection scope of the present invention. For those skilled in the art, it should be realized that all the equivalent replacements and obvious changes made by using the content of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for synchronously oxidizing and flocculating to remove low-valent phosphorus in wastewater with an aluminum-based composite agent, characterized in that, It includes the following steps: Put aluminum powder and ferric salt in an inert atmosphere for ball milling treatment to obtain an aluminum-based composite agent; Add the aluminum-based composite agent to the wastewater containing low-valent phosphorus and react for a certain time under aerobic conditions; in this reaction, hypophosphite ions and / or phosphite ions are oxidized to orthophosphate ions and removed in the form of flocculation precipitation.

2. The method according to claim 1, wherein The ferric salt includes ferric sulfate and / or ferric chloride.

3. The method according to claim 1, characterized in that, The mass ratio of the aluminum powder to the ferric element in the ferric salt is (5-20):

1.

4. The method according to claim 1, wherein The rotation speed of the ball milling treatment is 300-500 rpm, and the time is 2-8 h.

5. The method according to claim 1, characterized in that, The ball milling treatment is carried out in an intermittent manner, and the time interval between adjacent two ball milling treatments is 20-40 min.

6. The method according to claim 1, characterized in that The purity of the aluminum powder is 95%-99%, and the particle size is 50-1000 mesh.

7. The method according to claim 1, wherein The addition amount of the aluminum-based composite agent in the wastewater is 0.1-5 g / L.

8. The method according to claim 1, wherein The pH of the wastewater is 2-6.

9. The method according to claim 1, characterized in that, The reaction under aerobic conditions includes: in an open container, using air as the oxygen source, and promoting the replacement of oxygen in the air with the solution by oscillation or stirring.

10. Application of the method according to any one of claims 1-9 in treating wastewater containing low-valent phosphorus generated in the production process of nickel plating, copper plating or flame retardant.

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