A method for removing heavy metal-organophosphorus complexes in water by enhanced Fenton oxidation and complex breaking

Abstract

The present invention discloses a method for strengthening Fenton oxidation to remove nickel-organophosphorus complexes in water, and is specifically related to the technical field of wastewater treatment. The treatment method provided by the present invention comprises: 1. Mixing wastewater containing nickel-organophosphorus complexes with Fenton co-catalysts, divalent iron ions, and hydrogen peroxide, adjusting the pH and stirring, destroying metal-coordination bonds and organic ligand structures in an acidic environment, and obtaining wastewater containing free nickel ions. 2. Then continue to adjust the pH of the system to alkaline, remove free nickel ions in the wastewater by precipitation, and the mineralization product of the organophosphorus ligand and the Fenton co-catalyst will also participate in the formation of precipitation, so the organic ligands and co-catalysts in the wastewater can also be removed by co-precipitation. The present invention adds a small amount of Fenton co-catalyst to significantly improve the selective removal ability of the organophosphorus complex nickel in the Fenton oxidation process, the heavy metal nickel removal efficiency is as high as more than 95%, the organic ligand mineralization rate can reach more than 70%, and the environmental protection benefit is obvious.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment, and in particular relates to a method for removing heavy metal-organic phosphorus complexes in water by strengthening Fenton oxidation and complex breaking. Background Art

[0002] Nickel (Ni) is widely used in various industries due to its excellent corrosion resistance, including use as catalysts, metal alloys, ceramic capacitors and metal surface electroplating. With the rapid development of the electroplating industry, a large amount of heavy metal wastewater has been generated. In addition to heavy metals, various organic chelating agents are used as stabilizers, detergents and brighteners in industrial activities. Most chelating agents, such as citrate and ethylenediaminetetraacetic acid (EDTA), are organic acids with carboxyl groups. The carboxyl group provides electrons to metal atoms to form coordination bonds, making the complexed heavy metals highly water-soluble and highly stable. Organophosphorus mainly includes organophosphoric acids containing CP bonds, organophosphate esters containing COP bonds, and other organophosphorus polymers. Organophosphoric acids are an important component of organophosphorus. They contain one or more phosphate groups [-C-PO(OH) 2 ], the CP bonds contained in them are very stable and can form strong chelation with metal ions, and have been widely used in many industries and fields. For example, in the papermaking and textile printing and dyeing industries, organophosphate chelating agents are often used to chelate metal ions to prevent natural textile fibers from being contaminated by deposited iron oxide and iron hydroxide. In circulating cooling water systems and membrane industries, organophosphate chelating agents are generally used as scale inhibitors to prevent scaling or membrane clogging; in detergents, PCs are often added as chelating agents, scale inhibitors and bleaching stabilizers; in the electroplating industry, organophosphates are also often used as ligands to easily combine with various heavy metals. This heavy metal-organophosphorus complex composite pollution greatly increases the difficulty of wastewater treatment, making it difficult for conventional chemical precipitants to compete with chelating agents, and thus unable to remove dissolved heavy metals. For example, China, the world's largest chemical nickel plating market, set the discharge standard for nickel in electroplating wastewater at 1.0 mg / L in 1996, and further reduced the standard for new factories to 0.5 mg / L in 2008, and the standard for environmentally sensitive areas to 0.1 mg / L. With the increasing requirements for heavy metal pollution control in industrial wastewater, the deep removal of heavy metals has become a problem that must be faced in industrial wastewater treatment.

[0003] Advanced oxidation-physicochemical treatment combined process has been widely used to treat heavy metal complexes. The overall treatment idea is to use advanced oxidation processes (AOPs) to break the heavy metal complexes in the water body. The heavy metals will be released from it in the form of free ions and finally removed by traditional physicochemical treatment processes. 2 O 2Decomposition produces HO·, which in turn degrades organic matter. Cationic surfactants are a class of organic compounds with hydrophilic and hydrophobic groups. When ionized in aqueous solution, the generated surfactant ions are positively charged. It can neutralize the negatively charged pollutants in water and act as an adsorbent bridge, thereby destabilizing and flocculating the pollutant system and facilitating sedimentation and filtration dehydration. In general, heavy metal-organic complexes formed by heavy metals and commonly used complexing agents (such as citric acid, tartaric acid, EDTA, HEDP, etc.) have high-density negative charge characteristics. For example, at pH = 11, Cr(III)-citrate mainly exists in a high-charge form, that is, [(Cr-citrate-OH) 2 (OH) 3 ] 5- , cannot be precipitated under alkaline conditions alone.

[0004] In summary, the existing treatment methods for nickel-organophosphorus wastewater have high energy consumption and low treatment efficiency, and it is difficult to efficiently remove nickel-organophosphorus through simple methods. Seeking complex heavy metal deep treatment technology with simple process, low cost and stable effect is a hot and difficult issue in the current research field of pollution control. Summary of the invention

[0005] In order to solve the problem that the existing technology is difficult to effectively remove complexed nickel-organophosphorus in wastewater, the present invention provides a method for removing heavy metal-organophosphorus complexes in water by enhanced Fenton oxidation decomposition. The method particularly focuses on the removal of heavy metals in wastewater. The method can achieve relatively economical and effective treatment of simulated wastewater and actual wastewater containing nickel-organophosphorus complexes under the competition of multiple organic acids and ions.

[0006] In order to achieve the above object, the technical solution provided by the present invention is:

[0007] A method for removing heavy metal-organophosphorus complexes in water by enhanced Fenton oxidation and complex breaking, comprising the following steps:

[0008] 1) mixing wastewater containing heavy metal-organophosphorus complex with Fenton co-catalyst, divalent iron ions and hydrogen peroxide, adjusting the pH of the wastewater to be acidic, and fully reacting in an acidic environment to break the complex bond of heavy metal-organophosphorus acid and oxidize it, thereby obtaining wastewater containing free heavy metal ions and organophosphorus mineralization products; wherein the Fenton co-catalyst is a cationic surfactant having a hydrophobic carbon chain longer than 10 carbon atoms;

[0009] 2) Add alkali to the wastewater to adjust the pH to neutral or alkaline, fully react with precipitation, remove free heavy metal ions in the wastewater by precipitation, separate the solid and liquid to obtain wastewater that meets the heavy metal discharge standards, and the mineralization products of the organophosphorus ligands and Fenton co-catalysts also participate in the formation of precipitation and are then removed by co-precipitation.

[0010] Furthermore, the heavy metals include nickel, and the concentration of heavy metals in the wastewater is 0.1-2 mmol / L; the organic phosphorus is one or more of aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, hydroxyethylenediphosphonic acid, and diethylenetriaminepenta(methylenephosphonic acid).

[0011] In the process of step 1) of the present invention, the nickel-organophosphorus complex with high density negative charge is enriched on the surface of the positively charged Fenton co-catalyst micelle through electrostatic attraction, so that the pollutants originally in the homogeneous system are gathered together to form a local reactor. The pollutants in the aggregated state are more conducive to being broken and oxidized, thereby greatly promoting the oxidation efficiency of active species such as hydroxyl radicals on target pollutants, and avoiding the active species being consumed by a large amount of coexisting substrates.

[0012] After the pH of the solution system after the Fenton reaction is adjusted to alkaline conditions in step 2), the free nickel ions present in the solution generate nickel hydroxide precipitates under alkaline conditions, and the mineralization products of the organophosphorus ligands and the Fenton co-catalyst also participate in the formation of the co-precipitation, ultimately achieving the purpose of removing heavy metal nickel and organophosphorus together.

[0013] In step 1), the role of the Fenton co-catalyst is to strengthen the Fenton oxidation. The HO· generated by the sufficient reaction of the divalent iron ions and the hydrogen peroxide breaks the complex bond of the nickel-organophosphoric acid and oxidizes it, thereby obtaining an organophosphorus mineralization product containing free nickel ions.

[0014] The purpose of step 2) is to remove the free nickel ion organophosphorus mineralization products in the wastewater by adsorption coprecipitation. Specifically, sodium hydroxide is added to the wastewater containing free nickel ions, organophosphorus mineralization products, and Fenton cocatalysts to adjust the pH to 7-14, so that the free nickel ions form hydroxide precipitation. It is worth noting that the organophosphorus ligand mineralization products and Fenton cocatalysts involved in the precipitation will also be removed by coprecipitation.

[0015] Furthermore, the Fenton co-catalyst is one or more of dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyldimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, tributylhexadecylphosphonium bromide, hexadecylpyridinium bromide, ethylhexadecyldimethylammonium bromide, sodium hexadecyl sulfonate, sodium hexadecyl sulfate, polyethylene glycol hexadecyl ether, and hexadecyldimethyl tertiary amine.

[0016] Furthermore, the Fenton co-catalyst is a cationic surfactant having a hydrophobic carbon chain of 16 or more carbon atoms. For example, the Fenton co-catalyst may be further preferably hexadecyltrimethylammonium bromide, hexadecyldimethylethylammonium bromide, tributylhexadecylphosphonium bromide, hexadecylpyridinium bromide, hexadecyltrimethylammonium chloride or octadecyltrimethylammonium bromide.

[0017] Furthermore, the molar ratio of Fenton co-catalyst to heavy metals in wastewater is 1 to 8:1. Since the treatment efficiency of hexadecyltrimethylammonium bromide is highest when it is close to the critical micelle concentration, the molar ratio of Fenton co-catalyst to heavy metals in wastewater is preferably 4 to 6:1.

[0018] Furthermore, the divalent iron ions in step 1) are provided by one or more of ammonium ferrous sulfate, ferrous carbonate, ferrous chloride, ferrous nitrate, and ferrous acetate, and the molar ratio of divalent iron ions to heavy metals in the wastewater is 1 to 20:1. Since less divalent iron and excess divalent iron cannot improve the efficiency of the Fenton reaction, and if the amount is excessive, more by-products are likely to be produced, thereby causing secondary pollution, the molar ratio of divalent iron ions to heavy metals in the wastewater is preferably 8 to 10:1.

[0019] Furthermore, in step 1), the molar ratio of hydrogen peroxide to heavy metals in wastewater is 10 to 300:1, because less hydrogen peroxide and excess hydrogen peroxide cannot improve the efficiency of Fenton reaction, and excess hydrogen peroxide easily produces more by-products and causes secondary pollution. The molar ratio of hydrogen peroxide to heavy metals in wastewater is preferably 80 to 100:1.

[0020] Preferably, the reaction temperature in step 1) is 20-30°C.

[0021] Preferably, the reaction time in step 1) is 10 to 120 minutes.

[0022] Since in step 1) when the reaction time is greater than or equal to 60 minutes, the reaction tends to be stable, the residual nickel concentration value changes very little, and further increasing the reaction time does not significantly improve the removal effect. More preferably, the reaction time in step 1) is 30 to 60 minutes.

[0023] Furthermore, the concentration of coexisting organic acids in the wastewater of step 1) is not greater than 10.0 mM, the organic acids include one or more of formic acid, acetic acid, malonic acid, and lactic acid, and the concentration of coexisting chloride ions, sulfate ions, nitrate ions, and carbonate ions is not greater than 100 mM.

[0024] Furthermore, in step 1), the pH of the wastewater is adjusted to 3-5, and hydrogen peroxide and divalent iron ions are used to carry out the Fenton reaction and the pH is adjusted to 3-5, because hydrogen peroxide and divalent iron ions are the basis of the Fenton reaction, and the efficiency is highest under acidic conditions of pH 3-5.

[0025] Furthermore, the pH is adjusted to 7-14 in step 2) because free nickel ions can form hydroxide precipitation under neutral to alkaline conditions, and under alkaline conditions, the organic phosphorus ligand mineralization products and Fenton co-catalysts involved in the precipitation can be entrained and removed by co-precipitation. The precipitation reaction time of step 2) is 30-90 minutes.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. Using the Fenton method in the advanced oxidation process, Fe(II) is used to catalyze H 2 O 2 The nickel-organophosphorus complex in the wastewater is decomposed to produce HO·, so that the nickel-organophosphorus complex bond is broken and oxidized, and wastewater containing free nickel ion and organophosphorus mineralization products is obtained. The electrostatic attraction and hydrophobic interaction depth of the Fenton co-catalyst are used to remove the free nickel ions, Fenton co-catalyst and organophosphorus mineralization products in the water body.

[0028] 2. While reducing the harm of nickel-organophosphorus complexes, it can adsorb organic matter in wastewater to a certain extent, compete with common organic acids in water bodies, and has the advantage of strong anti-interference.

[0029] 3. The present invention significantly improves the selective removal ability of organic phosphorus complex nickel in the Fenton oxidation process by adding a small amount of Fenton co-catalyst, and the heavy metal nickel removal efficiency is as high as more than 95%, and the organic ligand mineralization rate can reach more than 70%. Compared with the prior art, the present invention has the characteristics of significant economy, universality, high efficiency, and simple operation. While achieving a high removal rate, it also greatly saves the input amount of many complex-breaking oxidants, saves costs, and shortens the processing time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a comparative line graph of the final residual phosphorus concentration after treatment by the present invention in Example 1;

[0031] Figure 2 is a comparative line graph of the final residual nickel concentration before and after the addition of the Fenton promoter in the present invention in Example 1-2;

[0032] Figure 3 is a comparative bar graph of the final residual nickel concentrations after treatment by the present invention under competition of four different organic acids in Examples 3-6;

[0033] Figure 4 is a comparative bar chart of the final residual nickel concentrations in Examples 7-10 after being treated by the present invention under common ion competition;

[0034] Figure 5It is a comparative bar chart of the final residual nickel concentrations after the conventional process in Examples 11-14 and after the treatment in Example 1 of the present invention.

[0035] Figure 6 It is a comparative bar chart of the final residual nickel concentrations of five cationic surfactants with the same carbon chain length but different configurations in Examples 15-18 and Example 1 after being treated by the present invention.

[0036] Figure 7 It is a comparative bar chart of the final residual nickel concentrations of six surfactants with the same carbon chain length but different charged head groups in Examples 19-22 and Example 1 and Example 15 after being treated by the present invention.

[0037] Figure 8 It is a comparative bar chart of the final residual nickel concentrations of six cationic surfactants with different carbon chain lengths in Examples 23-27 and Example 1 after being treated by the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0039] Example 1

[0040] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation and complex breaking, specifically comprising the following steps:

[0041] S1. Prepare nickel-organophosphorus complex simulated wastewater, add nickel chloride and hydroxyethylidene diphosphonic acid into water at a molar ratio of 1:1, and stir thoroughly to allow hydroxyethylidene diphosphonic acid to chelate nickel salt to form a complex Ni 2+ -HEDP, the final concentration of Ni added to the wastewater is 0.1mmol / L, and simulated wastewater containing nickel-organophosphorus complex is obtained.

[0042] Adding cetyltrimethylammonium bromide (CTAB), ammonium ferrous sulfate and hydrogen peroxide to the simulated wastewater prepared above, the molar ratios of CTAB, divalent iron ions and hydrogen peroxide to Ni in the wastewater are 4:1, 8:1 and 100:1, respectively, and adjusting the pH of the wastewater to 3, allowing the nickel-organophosphate complex bond to be broken and oxidized to obtain wastewater containing free nickel ion organophosphate mineralization products, the reaction time is 60 minutes, and the reaction temperature is room temperature;

[0043] S2. Continue to adjust the pH of the wastewater containing free nickel ions obtained in step S1 to 9, fully precipitate and react for 60 minutes, and then separate the solid and liquid to obtain wastewater that meets the heavy metal discharge standards.

[0044] Example 2

[0045] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that cetyltrimethylammonium bromide (CTAB) is not added in step S1.

[0046] Example 3

[0047] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that formic acid is added in step S1 at a molar ratio of 10:1 to nickel in the wastewater.

[0048] Example 4

[0049] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that acetic acid is added in step S1 at a molar ratio of 10:1 to nickel in the wastewater.

[0050] Example 5

[0051] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that malonic acid is added in step S1 at a molar ratio of 10:1 to nickel in the wastewater.

[0052] Example 6

[0053] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that lactic acid is added in step S1 at a molar ratio of 10:1 to nickel in the wastewater.

[0054] Example 7

[0055] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that sodium chloride is added in a molar ratio of 100:1 to nickel in the wastewater in step S1.

[0056] Example 8

[0057] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that sodium nitrate is added in step S1 at a molar ratio of 100:1 to nickel in the wastewater.

[0058] Example 9

[0059] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that sodium sulfate is added in step S1 at a molar ratio of 100:1 to nickel in the wastewater.

[0060] Example 10

[0061] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that sodium carbonate is added in step S1 at a molar ratio of 100:1 to nickel in the wastewater.

[0062] Embodiment 11

[0063] A method for removing nickel-organophosphorus complexes from water by enhanced Fenton oxidation decomposition, which is different from Example 1 in that: no hexadecyltrimethylammonium bromide (CTAB), divalent iron compounds, or hydrogen peroxide are added to the wastewater containing the nickel-organophosphorus complex in step S1, and only an alkaline precipitation process is used to adjust the pH of the mixed solution to 10.

[0064] Example 12

[0065] A method for removing nickel-organophosphorus complexes from water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that: in step S1, the wastewater containing nickel-organophosphorus complexes does not contain cetyltrimethylammonium bromide (CTAB), divalent iron compounds, or hydrogen peroxide, but only aluminum sulfate with a final concentration of 160 mg / L is added, and the pH of the mixed solution is adjusted to 10.

[0066] Embodiment 13

[0067] A method for removing nickel-organophosphorus complexes from water by enhanced Fenton oxidation decomposition, which is different from Example 1 in that: no cetyltrimethylammonium bromide (CTAB), divalent iron compounds, or hydrogen peroxide are added to the wastewater containing the nickel-organophosphorus complex in step S1, and only ferrous sulfate with a final concentration of 50 mg / L is added, and the pH of the mixed solution is adjusted to 7.2.

[0068] Embodiment 14

[0069] A method for removing nickel-organophosphorus complexes from water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that: in step S1, the wastewater containing nickel-organophosphorus complexes does not contain cetyltrimethylammonium bromide (CTAB), divalent iron compounds, or hydrogen peroxide, but only polyaluminium chloride with a final concentration of 60 mg / L is added, and the pH of the mixed solution is adjusted to 7.2.

[0070] Embodiment 15

[0071] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that the hexadecyltrimethylammonium bromide (CTAB) in step S1 is replaced by an equal molar amount of hexadecyltrimethylammonium chloride (CTAC).

[0072] Example 16

[0073] A method for removing nickel-organophosphorus complexes from water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that the hexadecyltrimethylammonium bromide (CTAB) in step S1 is replaced by an equal molar amount of hexadecyldimethylethylammonium bromide (EHDAB).

[0074] Embodiment 17

[0075] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that the hexadecyltrimethylammonium bromide (CTAB) in step S1 is replaced by an equal molar amount of tributylhexadecylphosphonium bromide (THPB).

[0076] Embodiment 18

[0077] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that the cetyltrimethylammonium bromide (CTAB) in step S1 is replaced by an equal molar amount of cetylpyridinium bromide (CPB).

[0078] Embodiment 19

[0079] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that the hexadecyltrimethylammonium bromide (CTAB) in step S1 is replaced by an equal molar amount of polyethylene glycol hexadecyl ether (PHE).

[0080] Embodiment 20

[0081] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that the hexadecyltrimethylammonium bromide (CTAB) in step S1 is replaced by an equal molar amount of hexadecyldimethyltertiary amine (HDTA).

[0082] Embodiment 21

[0083] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that the hexadecyltrimethylammonium bromide (CTAB) in step S1 is replaced by an equal molar amount of sodium hexadecyl sulfonate (SDS).

[0084] Embodiment 22

[0085] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that the hexadecyltrimethylammonium bromide (CTAB) in step S1 is replaced by an equal molar amount of hexadecyl sodium sulfate (SHS).

[0086] Embodiment 23

[0087] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that the hexadecyltrimethylammonium bromide (CTAB) in step S1 is replaced by an equal molar amount of octadecyltrimethylammonium bromide.

[0088] Embodiment 24

[0089] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that the hexadecyltrimethylammonium bromide (CTAB) in step S1 is replaced by an equal molar amount of decanyltrimethylammonium bromide.

[0090] Embodiment 25

[0091] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that the hexadecyltrimethylammonium bromide (CTAB) in step S1 is replaced by an equal molar amount of dodecyltrimethylammonium bromide.

[0092] Embodiment 26

[0093] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that the hexadecyltrimethylammonium bromide (CTAB) in step S1 is replaced by an equal molar amount of tetradecyltrimethylammonium bromide.

[0094] Embodiment 27

[0095] A method for removing nickel-organophosphorus complexes in water by enhanced Fenton oxidation decomposition, wherein the difference from Example 1 is that the hexadecyltrimethylammonium bromide (CTAB) in step S1 is replaced by an equal molar amount of octadecyltrimethylammonium bromide.

[0096] The wastewater from the experiments of Examples 1-27 was tested for performance:

[0097] The test of the residual amount of complexed nickel in wastewater is carried out by flame atomic absorption spectrometer (AA). The operation steps are as follows: the total content of nickel ions in the wastewater solution before and after treatment is determined, including complexed and free nickel.

[0098] The phosphorus concentration in wastewater is tested using an ultraviolet spectrophotometer. The operating steps are: determine the total phosphorus and inorganic phosphorus contents respectively, and calculate the organic phosphorus content.

[0099] Figure 1 is a comparative line chart of the final residual phosphorus concentration after treatment by the method of the present invention in Example 1. Figure 1It can be seen that the total phosphorus content does not change with the reaction, the concentration of organic phosphorus ligands gradually decreases with the increase of reaction time and then tends to be stable, and the concentration of inorganic phosphorus gradually increases with the increase of reaction time and then tends to be stable. This shows that after the treatment of the present invention, the organic phosphorus in the pollutants is gradually mineralized into inorganic phosphorus as the reaction proceeds, and the mineralization rate can reach 78%. The mineralized inorganic phosphorus in the wastewater is easier to remove than the organic phosphorus.

[0100] Figure 2 It is a comparative line graph of the final residual nickel concentration before and after the addition of the Fenton promoter in Example 1-2. It has been determined that in the experiment without adding the Fenton promoter, after the pure Fenton reaction treatment, the final residual nickel concentration in the wastewater is about 4.97 mg / L, and the removal rate is about 15.42%; while in the experiment with the addition of the Fenton promoter, after the reaction, the final residual nickel concentration in the wastewater is about 0.05 mg / L, and the removal rate is about 99.15%. The final residual nickel concentration can meet China's "Copper, Nickel, Cobalt Industrial Pollutant Emission Standard" (GB25467-2010) (0.5 mg / L). It shows that the present invention significantly improves the selective removal ability of the Fenton oxidation process for organic phosphorus complex nickel by adding the Fenton promoter. In the wastewater treatment method of the present invention, pollutants in the initial wastewater system are in a dispersed state and are not easily broken and oxidized by hydroxyl radicals. By adding a Fenton co-catalyst, a nickel-organophosphorus complex with a high density of negative charge is enriched on the surface of the positively charged Fenton co-catalyst micelles through electrostatic attraction, and pollutants in an aggregated state are more conducive to being broken and oxidized.

[0101] Figure 3 It is a comparative bar graph of the final residual nickel concentration after treatment by the present invention under the competition of four different organic acids in Examples 3-6. It has been determined that for the competition of formic acid, the residual nickel concentration in the water body treated by the present invention is about 0.10 mg / L, and the removal rate is about 98.3%; for the competition of acetic acid, the residual nickel concentration in the water body treated by the present invention is about 0.11 mg / L, and the removal rate is about 98.13%; for the competition of malonic acid, the residual nickel concentration in the water body treated by the present invention is about 0.28 mg / L, and the removal rate is about 95.23%; for the competition of lactic acid, the residual nickel concentration in the water body treated by the present invention is about 0.06 mg / L, and the removal rate is about 97.96%. It shows that the present invention has good anti-interference against the competition of common organic acids, and the final residual nickel concentration can meet China's "Copper, Nickel, Cobalt Industrial Pollutant Emission Standard" (GB25467-2010) (0.5 mg / L).

[0102] Figure 4It is a comparative bar chart of the final residual nickel concentration after treatment by the present invention under common ion competition in Examples 7-10. It has been determined that for the competition of chloride ions, the residual nickel concentration in the water body treated by the present invention is about 0.11 mg / L, and the removal rate is about 98.13%; for the competition of nitrate ions, the residual nickel concentration in the water body treated by the present invention is about 0.19 mg / L, and the removal rate is about 96.66%; for the competition of sulfate ions, the residual nickel concentration in the water body treated by the present invention is about 0.16 mg / L, and the removal rate is about 97.22%; for the competition of carbonate ions, the residual nickel concentration in the water body treated by the present invention is about 0.33 mg / L, and the removal rate is about 94.36%. It shows that the present invention has good anti-interference against the competition of common ions, and the final residual nickel concentration can meet China's "Copper, Nickel, Cobalt Industrial Pollutant Emission Standard" (GB25467-2010) (0.5 mg / L).

[0103] Figure 5 It is a comparative bar chart of the final residual nickel concentration after the conventional process in Examples 11-14 and after the treatment of Example 1 of the present invention. It has been determined that the residual nickel concentration in the water body after the alkaline precipitation process is about 5.81 mg / L, and the removal rate is about 1.02%; the residual nickel concentration in the water body after the addition of aluminum sulfate is about 5.79 mg / L, and the removal rate is about 1.36%; the residual nickel concentration in the water body after the addition of ferrous sulfate is about 5.75 mg / L, and the removal rate is about 2.04%; the residual nickel concentration in the water body after the addition of polyaluminum chloride is about 5.68 mg / L, and the removal rate is about 3.24%. It shows that some common processes cannot remove nickel-organic phosphorus complexes in water, and the final residual nickel concentration cannot meet China's "Copper, Nickel, Cobalt Industrial Pollutant Emission Standard" (GB25467-2010) (0.5 mg / L).

[0104] Figure 6It is a comparative bar graph of the final residual nickel concentration of five cationic surfactants with the same carbon chain length and different configurations in Examples 15-18 and Example 1 after being treated by the present invention. It has been determined that when the carbon chain length of the surfactant is 16 and the head groups are all positively charged, hexadecyl trimethyl ammonium chloride (CTAC), hexadecyl dimethyl ethyl ammonium bromide (EHDAB), tributyl hexadecyl phosphine bromide (THPB), and hexadecyl pyridine bromide (CPB) are used as Fenton cocatalysts, and the residual nickel concentrations in the water body after the experimental treatment are 0.08 mg / L, 0.13 mg / L, 0.12 mg / L, and 0.11 mg / L, respectively, and the final residual nickel concentration can meet China's "Copper, Nickel, Cobalt Industrial Pollutant Emission Standards" (GB25467-2010) (0.5 mg / L). It shows that the use of cationic surfactants with a carbon chain length of 16 and positive charge can significantly improve the selective removal ability of the Fenton oxidation process for organic phosphorus complex nickel.

[0105] Figure 7 It is a comparative bar graph of the final residual nickel concentration of six surfactants with the same carbon chain length and different charged head groups in Examples 19-22 and Example 1 and Example 15 after being treated by the present invention. It has been determined that when the carbon chain length of the surfactant is 16, different charged head groups of surfactants are selected, polyethylene glycol hexadecyl ether (PHE), hexadecyl dimethyl tertiary amine (HDTA), sodium hexadecyl sulfonate (SDS), sodium hexadecyl sulfate (SHS) are used as Fenton cocatalysts, and the residual nickel concentrations in the water body after experimental treatment are 4.13 mg / L, 3.95 mg / L, 3.72 mg / L, and 3.16 mg / L, respectively. Using nonionic and anionic surfactants as Fenton cocatalysts, the final residual nickel concentration cannot meet China's "Copper, Nickel, Cobalt Industrial Pollutant Emission Standard" (GB25467-2010) (0.5 mg / L).

[0106] Figure 8It is a comparative bar graph of the final residual nickel concentration of six cationic surfactants with different carbon chain lengths in Examples 23-27 and Example 1 after being treated by the method of the present invention. After measurement, cationic surfactants with different carbon chain lengths were selected for comparative experiments, and octadecyl trimethyl ammonium bromide, decanyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium bromide, and octadecyl trimethyl ammonium bromide were used as Fenton cocatalysts, and the residual nickel concentrations in the water body after the experimental treatment were 4.17 mg / L, 3.87 mg / L, 3.64 mg / L, 3.37 mg / L, and 0.22 mg / L, respectively. With the increase of the carbon chain length of the cationic surfactant, the final residual nickel concentration presents a trend of gradually decreasing. When the carbon chain length is greater than or equal to 16, the final residual nickel concentration after being treated by the present invention can meet China's "Copper, Nickel, Cobalt Industrial Pollutant Emission Standard" (GB25467-2010) (0.5 mg / L).

[0107] In summary, the existing common coagulation process has a poor effect on the treatment of wastewater containing nickel-organophosphorus complexes. The present invention is used to treat wastewater containing nickel-organophosphorus complexes, and has good resistance to the competitive interference of related organic acids and ions. The removal efficiency of heavy metal nickel is as high as more than 95%, and the mineralization rate of organic ligands can reach more than 70%. Compared with the prior art, the present invention has the characteristics of significant economy, universality, high efficiency, and simple operation. While achieving a high removal rate, it also greatly saves the input of many complex-breaking oxidants, saves costs, and shortens the treatment time.

[0108] The contents described in this specification are merely an enumeration of implementation forms of the inventive concept, and the protection scope of the present invention should not be regarded as being limited to the specific forms described in the embodiments.

Claims

1. A method for removing heavy metal-organophosphorus complexes in water by enhanced Fenton oxidation and complex breaking, characterized in that: The following steps are involved: 1) Mix the wastewater containing heavy metal-organophosphorus complex with Fenton catalyst, divalent iron ions and hydrogen peroxide, adjust the pH of the wastewater to acidic, and fully react in an acidic environment to break the complex bond of heavy metal-organophosphorus acid and oxidize it, so as to obtain wastewater containing free heavy metal ions and organophosphorus mineralization products; Wherein, the Fenton co-catalyst is hexadecyltrimethylammonium bromide, hexadecyldimethylethylammonium bromide, tributylhexadecylphosphonium bromide, hexadecylpyridinium bromide, hexadecyltrimethylammonium chloride or octadecyltrimethylammonium bromide; 2) Add alkali to the wastewater to adjust the pH to neutral or alkaline, fully precipitate the reaction, remove the free heavy metal ions in the wastewater by precipitation, separate the solid and liquid to obtain the wastewater that meets the heavy metal discharge standards, and the mineralization products of the organophosphorus ligands and the Fenton co-catalyst also participate in the formation of precipitation and are then removed by co-precipitation; Step 1) the molar ratio of Fenton catalyst to heavy metals in wastewater is 4 to 6:1, the molar ratio of divalent iron ions to heavy metals in wastewater is 8 to 10:1, and the molar ratio of hydrogen peroxide to heavy metals in wastewater is 80 to 100:1; In step 1), the pH of the wastewater is adjusted to 3 to 5, and the reaction time is 30 to 60 minutes; In step 2), the pH is adjusted to 7-14 and the precipitation reaction time is 30-90 minutes.

2. The method for removing heavy metal-organophosphorus complexes in water by enhanced Fenton oxidation and complex breaking as claimed in claim 1, characterized in that: The heavy metals include nickel, and the concentration of heavy metals in the wastewater is 0.1 to 2 mmol / L; the organic phosphorus is one or more of aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, hydroxyethylenediphosphonic acid, and diethylenetriaminepenta(methylenephosphonic acid).

3. The method for removing heavy metal-organophosphorus complexes in water by enhanced Fenton oxidation and complex breaking as claimed in claim 1, characterized in that: The divalent iron ions in step 1) are provided by one or more of ammonium ferrous sulfate, ferrous carbonate, ferrous chloride, ferrous nitrate, and ferrous acetate.

4. The method for removing heavy metal-organophosphorus complexes in water by enhanced Fenton oxidation and complex breaking as claimed in claim 1, characterized in that: Step 1) The concentration of coexisting organic acids in the wastewater is not greater than 10.0 mM, the organic acids include one or more of formic acid, acetic acid, malonic acid, and lactic acid, and the concentration of coexisting chloride ions, sulfate ions, nitrate ions, and carbonate ions is not greater than 100 mM.

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