Catalytic valence change combined process for phosphogypsum stack leachate

Abstract

The present invention provides a catalytic valence change combination process for leachate from phosphogypsum stockpiles, which relates to the technical field of sewage treatment. The specific steps include: S1. Adding a phosphorus-fluorine precipitant to the leachate from the phosphogypsum stockpile, adjusting the pH to 7-8, adding a PAM flocculant, and filtering; S2. Passing the supernatant filtered in S1 into a photocatalytic reactor, adding a copper oxide / hydroxy iron oxide (CuO / FeOOH) composite material, adjusting the pH value to 2, and reacting at room temperature; S3. Centrifuging the suspension after the reaction in S2; S4. Adding an ammonia nitrogen remover to the supernatant after centrifugation in S3, adjusting the pH value to 7-8, and reacting at room temperature; S5. Adding a phosphorus-fluorine precipitant to the solution after oxidation in S4, adjusting the pH value to 11-12, adding a PAM flocculant, and filtering; S6. Discharging the water. After being treated by the treatment process of the present invention, the ammonia nitrogen content in the discharged water is less than 10 mg / L, the total nitrogen content is less than 15 mg / L, the total phosphorus content is less than 0.5 mg / L, the fluoride ion content is less than 15 mg / L, the SS content is less than 30 mg / L, and the COD content is less than 50 mg / L, meeting the effluent index of the Chaohu Lake Basin.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and specifically relates to a catalytic valence change combination process for leachate from phosphogypsum storage yards. Background Art

[0002] Phosphogypsum is a by-product of chemical industries such as phosphate fertilizer industry. Due to economic reasons and others, phosphogypsum is often piled up in large quantities. With the scouring of rainwater and other reasons, some of its chemical substances also seep in and flow into water sources such as surface water. This kind of leachate has the following characteristics: it has a relatively high acidity and contains harmful substances such as fluorides, medium and low concentrations of ammonia nitrogen, nitrate nitrogen, and high concentration of phosphorus. Therefore, phosphogypsum leachate will cause the deterioration of water quality of water sources, pollute crops, soil, etc., and even cause harm to organisms such as humans and livestock.

[0003] To solve the above problems, relevant practitioners have also proposed various solutions. CN110498537A discloses a process for efficiently removing ammonia nitrogen from phosphofluoric sewage containing ammonia nitrogen. This invention uses the addition of lime milk to adjust the pH of the sewage, and then uses the principle of struvite method to add magnesium oxide to precipitate ammonia nitrogen in the sewage, and finally realizes the removal of ammonia nitrogen in the sewage. However, removing ammonia nitrogen by chemical precipitation method leads to an increase in the amount of solid waste in the actual treatment process, increasing the treatment cost. In addition, the addition amount of magnesium oxide is very high, generally more than 3 times, otherwise the effluent index will not be reached, resulting in waste of reagents and increasing the cost pressure.

[0004] The prior art usually treats the harmful components in phosphogypsum leachate singly. After treatment, the phosphogypsum leachate still contains other harmful components. Even if a few studies remove multiple harmful components, the removal effect is not ideal enough, and the treatment method is cumbersome and the efficiency is low. Therefore, the present invention provides a catalytic valence change combination process for phosphogypsum storage yard leachate with low treatment cost, high efficiency, and excellent effect. Summary of the Invention

[0005] (1) Technical Problems to be Solved

[0006] In view of the deficiencies of the prior art, the present invention provides a catalytic valence change combination process for phosphogypsum storage yard leachate, which solves the problems of low treatment efficiency, high treatment cost, and poor treatment effect of existing phosphogypsum storage yard leachate.

[0007] (2) Technical Solutions

[0008] To achieve the above object, the present invention is realized through the following technical solutions:

[0009] The catalytic valence change combination process for phosphogypsum storage yard leachate specifically includes the following steps:

[0010] S1. Primary precipitation for phosphorus and fluorine removal: Add calcium hydroxide (Ca(OH)2), a phosphorus and fluorine precipitant, to the leachate of the phosphogypsum yard, adjust the pH to 7 - 8, mix evenly, add PAM flocculant, and then filter.

[0011] S2. Photocatalytic reduction for nitrate nitrogen removal: Pass the clarified liquid filtered in S1 into a photocatalytic reactor, and add copper oxide / hydroxy iron oxide (CuO / FeOOH). The morphology and crystal structure of copper oxide / hydroxy iron oxide (CuO / FeOOH) are as Figure 2 shown. CuO accounts for 1% - 20% of the total amount of CuO / FeOOH, and the mass concentration of copper oxide / hydroxy iron oxide is 20 - 50 mg / L. Add dilute sulfuric acid to adjust the pH value to 2, react at room temperature for 3 h, perform dark adsorption for 1 h, and carry out photocatalysis for 2 h.

[0012] S3. Centrifugation for catalyst removal: Centrifuge the turbid liquid after the reaction in S2 through a centrifuge device.

[0013] S4. Breakpoint chlorination for ammonia nitrogen removal: Add an ammonia nitrogen remover to the clarified liquid after centrifugation in S3. The ammonia nitrogen remover is any one of Cl2, NaClO, and HClO. Add calcium hydroxide solution to adjust the pH value to 7 - 8, and react at room temperature for 2 h.

[0014] S5. Secondary precipitation for phosphorus and fluorine removal: Add calcium hydroxide (Ca(OH)2), a phosphorus and fluorine precipitant, to the solution after oxidation in S4, adjust the pH value to 11 - 12, mix evenly, add PAM flocculant, and then filter.

[0015] S6. Effluent discharge.

[0016] Before treatment, the monthly water volume of the leachate from the phosphogypsum yard is about 6000 m 3 , with a total phosphorus concentration as high as 5400 mg / L, an ammonia nitrogen content of about 300 mg / L, a nitrate nitrogen content of about 60 mg / L, and a fluoride ion concentration of about 300 mg / L.

[0017] After the treatment of the leachate from the phosphogypsum yard, the ammonia nitrogen content in the effluent is less than 10 mg / L, the total nitrogen content is less than 15 mg / L, the total phosphorus content is less than 0.5 mg / L, the fluoride ion content is less than 15 mg / L, the SS content is less than 30 mg / L, and the COD content is less than 50 mg / L, meeting the effluent standards of the Chaohu Lake Basin.

[0018] The total phosphorus removal rate of this treatment process is 99.99%, and the fluoride removal rate is above 95%.

[0019] When treating the leachate from the phosphogypsum yard, in S1, adding Ca(OH)2 to adjust the pH of the leachate, the added Ca 2+ can also remove part of the total phosphorus at the same time, which can be represented by the following equation:

[0020] Ca2+ +PO4 3- →Ca3(PO4)2↓。

[0021] The S2 photocatalytic reaction is to oxidize and reduce the valence of pollutants with a photocatalyst under ultraviolet light irradiation, so as to decompose the pollutants into small molecule compounds without pollution. The photocatalytic reaction is usually based on the energy band theory of n-type semiconductors. There is a forbidden band composed of a high-energy valence band (without electrons) and a low-energy valence band (filled with electrons) inside, and this forbidden band is a discontinuous region; when the electrons on its full band are irradiated by light with an energy greater than the forbidden band width, they are excited and enter the conduction band. At the same time, holes (h + ) are generated on the full band. The excited electrons and holes combine to form hole / electron pairs, which are also called photo-generated carriers, and the photo-generated carriers have high activity and can be used to treat nitrate nitrogen by photocatalytic reduction and valence change.

[0022] After adding NaClO, S4 can gradually oxidize NH3 - H to chloramines (NH2Cl, NHCl2, NCl3), and finally oxidize NH3 - H to N2 to achieve the purpose of removing NH3 - H. The reaction principle is as follows:

[0023] NH3+HOCl→NH2Cl+H2O

[0024] NH2Cl+HOCl→NHCl2+H2O

[0025] NHCl2+HOCl→NCl3+H2O。

[0026] The above breakpoint chlorination method can effectively remove the color of water and reduce the COD content in wastewater.

[0027] S5 then adopts the chemical precipitation method to simultaneously precipitate the remaining total phosphorus and fluoride ions by adding Ca 2+ again, generating calcium phosphate and calcium fluoride precipitates.

[0028] (III) Beneficial effects

[0029] The present invention provides a catalytic valence change combination process for the leachate of a phosphogypsum yard. Compared with the prior art, it has the following beneficial effects:

[0030] 1. The present invention develops a short-process and highly efficient classification treatment catalytic valence change combination process for the leachate of a phosphogypsum yard, which can simply and quickly treat ammonia nitrogen, total nitrogen, total phosphorus and fluoride in the leachate of a phosphogypsum yard.

[0031] 2. The present invention is designed in an overall manner according to the characteristics of the leachate from phosphogypsum stockpiles. Combining the properties and types of pollutants, a catalytic valence change classification treatment combined process is adopted, saving a large amount of raw materials and effectively reducing the sludge volume and cost requirements.

[0032] 3. The chemical reagents and the like used in the present invention have low costs, few process flows, are simple and fast, and are inexpensive, and can be applied industrially.

[0033] 4. The sequence of the treatment process of the present invention cannot be adjusted. A method for treating the leachate from phosphogypsum stockpiles by using the breakpoint chlorination method and the chemical precipitation method in sequence and step by step is simple and feasible, can effectively reduce the sludge volume, save time, and at the same time can effectively reduce costs and protect the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0035] Figure 1 is the process flow diagram of the embodiment of the present invention;

[0036] Figure 2 is the SEM diagram of copper oxide / hydroxy iron oxide (CuO / FeOOH) in the embodiment of the present invention;

[0037] Figure 3 is the graph of the influence of the solution pH on the NH3 - H removal rate in S4 of the present invention;

[0038] Figure 4 is the graph of the influence of the dosage of NaClO on the NH3 - H removal rate in S4 of the present invention;

[0039] Figure 5 is the graph of the influence of the reaction time of NaClO on the NH3 - H removal rate in S4 of the present invention;

[0040] Figure 6(a) is the graph of the influence of the pH of the effluent solution on the total phosphorus content in S5 of the present invention;

[0041] Figure 6(b) is the graph of the influence of the pH of the effluent solution on the fluorine content in S5 of the present invention;

[0042] Figure 7 is the FTIR spectrogram of the catalysts used in Example 2, Example 4, Example 5, Comparative Example 1, and Comparative Example 2 of the present invention;

[0043] Among them, in Example 2, CuO accounts for 20% of the total amount of CuO / FeOOH, and is abbreviated as Cu / Fe-3 in Figure 7 ;

[0044] In Example 4, CuO accounts for 5% of the total amount of CuO / FeOOH, and is abbreviated as Cu / Fe-1 in Figure 7 ;

[0045] In Example 5, CuO accounts for 15% of the total amount of CuO / FeOOH, and is abbreviated as Cu / Fe-2 in Figure 7 ;

[0046] Figure 8 is the XRD pattern of the catalysts used in Example 2, Example 4, Example 5, Comparative Example 1, and Comparative Example 2 of the present invention;

[0047] Among them, in Example 2, CuO accounts for 20% of the total amount of CuO / FeOOH, and is abbreviated as Cu / Fe-3 in Figure 8 ;

[0048] In Example 4, CuO accounts for 5% of the total amount of CuO / FeOOH, and is abbreviated as Cu / Fe-1 in Figure 8 ;

[0049] In Example 5, CuO accounts for 15% of the total amount of CuO / FeOOH, and is abbreviated as Cu / Fe-2 in Figure 8 ;

[0050] Figure 9 is the graph showing the influence of the catalysts used in Example 2, Example 4, Example 5, Comparative Example 1, and Comparative Example 2 of the present invention on the TN removal rate;

[0051] Among them, in Example 2, CuO accounts for 20% of the total amount of CuO / FeOOH, and is abbreviated as Cu / Fe-3 in Figure 9 ;

[0052] In Example 4, CuO accounts for 5% of the total amount of CuO / FeOOH, and is abbreviated as Cu / Fe-1 in Figure 9 ;

[0053] In Example 5, CuO accounts for 15% of the total amount of CuO / FeOOH, and is abbreviated as Cu / Fe-2 in Figure 9 ;

[0054] Figure 10 is the graph showing the influence of the catalysts with different mass concentrations used in Example 2, Example 6, Example 7, and Example 8 of the present invention on the TN removal rate;

[0055] Figure 11It is the image diagram of the TN removal rate when the S2 solution is adjusted to different pH values in Embodiment 2, Embodiment 9, Embodiment 10, and Embodiment 11 of the present invention. Detailed implementation manners

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0057] By providing a catalytic valence change combination process for phosphogypsum stack leachate in the embodiments of this application, the problems of low treatment efficiency, high treatment cost, and poor treatment effect of the existing phosphogypsum stack leachate are solved, and the purpose of efficiently and low-cost treating the phosphogypsum stack leachate is achieved.

[0058] To better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with the specification drawings and specific implementation manners.

[0059] The catalytic valence change combination process for phosphogypsum stack leachate specifically includes the following steps:

[0060] S1. Primary precipitation for removing phosphorus and fluorine: Add the phosphorus and fluorine precipitant Ca(OH)2 to the phosphogypsum stack leachate, adjust the pH, mix evenly, add the PAM flocculant, and filter.

[0061] S2. Photocatalytic reduction for removing nitrate nitrogen: Pass the clear liquid filtered in S1 into the photocatalytic reaction tank, and add copper oxide / hydroxy iron oxide (CuO / FeOOH). The SEM diagram of this copper oxide / hydroxy iron oxide (CuO / FeOOH) is as Figure 2 shown. FeOOH presents a rod-like structure. With the addition of CuO, CuO / FeOOH also presents a rod-like structure, and it can effectively improve the photocatalytic effect of the copper oxide / hydroxy iron oxide composite material. Adjust the pH, react at room temperature, perform dark adsorption for 1 h, and perform photocatalysis for 2 h.

[0062] S3. Centrifugal separation to remove the catalyst: Centrifuge the turbid liquid after the reaction in S2 through a centrifuge device.

[0063] S4. Breakpoint chlorination for removing ammonia nitrogen: Add NaClO to the clear liquid after centrifugation in S3, adjust the pH value, and react at room temperature.

[0064] S5. Secondary precipitation for removing phosphorus and fluorine: Add Ca(OH)2 to the solution after oxidation in S4, adjust the pH value, mix evenly, add the PAM flocculant, and filter.

[0065] S6. Water discharge.

[0066] Adjustment experiments are carried out on the relevant parameters in the above process steps to determine the optimal parameters or the optimal parameter range values.

[0067] 1. Adjust the pH value in step S1, observe the influence of the solution pH value on the total phosphorus content and fluorine content in this step, and determine that the optimal pH range for removing total phosphorus and fluorine is 7 - 8. The specific situation is shown in Table 1 below.

[0068] Table 1 - Influence of the change of solution pH value in S1 on total phosphorus content and fluorine content

[0069]

[0070]

[0071] 2. Adjust the pH value of the solution in step S4, observe the influence of the solution pH value on the ammonia nitrogen content in this step, and determine that the optimal pH range for removing ammonia nitrogen is 7 - 8. The specific situation is shown in Figure 3 .

[0072] 3. Adjust the pH value of the solution in S4 to 7 - 8, adjust the dosage of NaClO in step S4, observe the influence of the NaClO dosage on the ammonia nitrogen content in this step, and determine that the optimal dosage value of NaClO is 1 mL (in the case where the leachate inflow is 100 mL). The specific situation is shown in Figure 4 .

[0073] 4. Adjust the pH value of the solution in S4 to 7 - 8, with the NaClO dosage value being 1 mL, adjust the reaction time of NaClO in step S4, observe the influence of the NaClO reaction time on the ammonia nitrogen content in this step, and determine that the optimal reaction time of NaClO is 120 min. The specific situation is shown in Figure 5 .

[0074] 5. Adjust the pH value of the solution in step S5, observe the influence of the solution pH value on the total phosphorus content and fluorine content in this step, and determine that the optimal pH range for removing total phosphorus and fluorine is 11 - 12. The specific situation is shown in Figure 6(a) and Figure 6(b).

[0075] Example 1:

[0076] The catalytic valence change combined process for the leachate of the phosphogypsum stack yard, as Figure 1 shown, specifically includes the following steps:

[0077] S1. Primary precipitation for removing phosphorus and fluorine: Take 100 mL of the leachate from the phosphogypsum stack yard, add the phosphorus and fluorine precipitant Ca(OH)2 to it, adjust the pH to 7, mix evenly, add the PAM flocculant, and filter;

[0078] S2. Photocatalytic reduction for nitrate nitrogen removal: The supernatant after filtration in S1 is introduced into a photocatalytic reaction chamber, and copper oxide / hydroxy iron oxide (CuO / FeOOH) is added, where CuO accounts for 20% of the total amount of CuO / FeOOH, and the mass concentration of copper oxide / hydroxy iron oxide is 40 mg / L. Adjust the pH value to 2 and react at room temperature for 3 h, with 1 h of dark adsorption and 2 h of photocatalysis;

[0079] S3. Centrifugation to remove catalyst: The turbid liquid after the reaction in S2 is centrifuged through a centrifugation device;

[0080] S4. Breakpoint chlorination for ammonia nitrogen removal: 1 mL of NaClO is added to the supernatant after centrifugation in S3, adjust the pH value to 7, and react at room temperature for 2 h;

[0081] S5. Secondary precipitation for phosphorus and fluoride removal: Calcium hydroxide (Ca(OH)2) as a phosphorus and fluoride precipitant is added to the solution after oxidation in S4, adjust the pH value to 11, mix evenly, add PAM flocculant, and then filter;

[0082] S6. Effluent discharge.

[0083] Example 2:

[0084] Catalytic valence change combined process for leachate from phosphogypsum stack yard, as Figure 1 shown, the specific steps include:

[0085] S1. Primary precipitation for phosphorus and fluoride removal: Take 100 mL of leachate from phosphogypsum stack yard, add calcium hydroxide (Ca(OH)2) as a phosphorus and fluoride precipitant, adjust the pH to 8, mix evenly, add PAM flocculant, and then filter;

[0086] S2. Photocatalytic reduction for nitrate nitrogen removal: The supernatant after filtration in S1 is introduced into a photocatalytic reaction chamber, and copper oxide / hydroxy iron oxide (CuO / FeOOH) is added, where CuO accounts for 20% of the total amount of CuO / FeOOH, and the mass concentration of copper oxide / hydroxy iron oxide is 40 mg / L. Adjust the pH value to 2 and react at room temperature for 3 h, with 1 h of dark adsorption and 2 h of photocatalysis;

[0087] S3. Centrifugation to remove catalyst: The turbid liquid after the reaction in S2 is centrifuged through a centrifugation device;

[0088] S4. Breakpoint chlorination for ammonia nitrogen removal: 1 mL of NaClO is added to the supernatant after centrifugation in S3, adjust the pH value to 8, and react at room temperature for 2 h;

[0089] S5. Secondary precipitation for phosphorus and fluoride removal: Calcium hydroxide (Ca(OH)2) as a phosphorus and fluoride precipitant is added to the solution after oxidation in S4, adjust the pH value to 12, mix evenly, add PAM flocculant, and then filter;

[0090] S6. Effluent discharge.

[0091] Example 3:

[0092] The catalytic valence change combination process for the leachate of the phosphogypsum yard is as Figure 1 shown, and the specific steps include:

[0093] S1. Primary precipitation for phosphorus and fluorine removal: Take 100 mL of the leachate from the phosphogypsum yard, add the phosphorus and fluorine precipitant Ca(OH)2 to it, adjust the pH to 8, mix evenly, add the PAM flocculant, and filter;

[0094] S2. Photocatalytic reduction for nitrate nitrogen removal: Pass the supernatant filtered in S1 into the photocatalytic reactor, and add copper oxide / hydroxy iron oxide (CuO / FeOOH), where CuO accounts for 20% of the total amount of CuO / FeOOH, and the mass concentration of copper oxide / hydroxy iron oxide is 40 mg / L. Adjust the pH value to 2, react at room temperature for 3 h, perform dark adsorption for 1 h, and perform photocatalysis for 2 h;

[0095] S3. Centrifugation for catalyst removal: Centrifuge the turbid liquid after the reaction in S2 through a centrifuge device;

[0096] S4. Breakpoint chlorination for ammonia nitrogen removal: Add 1 mL of NaClO to the supernatant after centrifugation in S3, adjust the pH value to 8, and react at room temperature for 2 h;

[0097] S5. Secondary precipitation for phosphorus and fluorine removal: Add the phosphorus and fluorine precipitant Ca(OH)2 to the solution after oxidation in S4, adjust the pH value to 11, mix evenly, add the PAM flocculant, and filter;

[0098] S6. Effluent discharge.

[0099] Example 4, the difference from Example 2 is that:

[0100] CuO in copper oxide / hydroxy iron oxide (CuO / FeOOH) accounts for 5% of the total amount of CuO / FeOOH.

[0101] Example 5, the difference from Example 2 is that:

[0102] CuO in copper oxide / hydroxy iron oxide (CuO / FeOOH) accounts for 15% of the total amount of CuO / FeOOH.

[0103] Example 6, the difference from Example 2 is that:

[0104] The mass concentration of copper oxide / hydroxy iron oxide is 20 mg / L.

[0105] Example 7, the difference from Example 2 is that:

[0106] The mass concentration of copper oxide / hydroxy iron oxide is 30 mg / L.

[0107] Example 8 is different from Example 2 in that:

[0108] The mass concentration of copper oxide / hydroxy iron oxide is 50 mg / L.

[0109] Example 9 is different from Example 2 in that:

[0110] In S2, the pH value is adjusted to 1.

[0111] Example 10 is different from Example 2 in that:

[0112] In S2, the pH value is adjusted to 3.

[0113] Example 11 is different from Example 2 in that:

[0114] In S2, the pH value is adjusted to 4.

[0115] Comparative Example 1 is different from Example 2 in that:

[0116] The catalyst for the photocatalytic reaction in S2 is CuO.

[0117] Comparative Example 2 is different from Example 2 in that:

[0118] The catalyst for the photocatalytic reaction in S2 is FeOOH.

[0119] Detection test

[0120] 1. The treated effluent is detected. The ammonia nitrogen content in the effluent is less than 10 mg / L, the total nitrogen content is less than 15 mg / L, the total phosphorus content is less than 0.5 mg / L, the fluoride ion content is less than 15 mg / L, the SS content is less than 30 mg / L, and the COD content is less than 50 mg / L, meeting the effluent standards of the Chaohu Lake Basin.

[0121] 2. Analyze the Cu / FeOOH with 20% CuO accounting for the total amount of Cu / FeOOH used in Example 2, the Cu / FeOOH with 5% CuO accounting for the total amount of Cu / FeOOH used in Example 4, the Cu / FeOOH with 15% CuO accounting for the total amount of Cu / FeOOH used in Example 5, the CuO used in Comparative Example 1, and the FeOOH used in Comparative Example 2, and obtain the Figure 7 FTIR spectrogram as shown and the Figure 8 XRD spectrogram as shown. It can be seen from Figure 7 , Figure 8 the structural differences of the above 5 catalysts.

[0122] 3. Detect the TN removal rates of Example 2, Example 4, Example 5, Comparative Example 1, and Comparative Example 2. The results are as Figure 9 shown. It can be seen from Figure 9 that the use of the copper oxide / hydroxy iron oxide (CuO / FeOOH) catalyst in Example 2 has the best TN removal effect.

[0123] 4. Detect the TN removal rates of Example 2, Example 6, Example 7, and Example 8. The results are as Figure 10 shown. It can be seen from Figure 10 that when the mass concentration of copper oxide / hydroxy iron oxide (CuO / FeOOH) in Example 2 is 40 mg / L, the TN removal effect is the best.

[0124] 5. Detect the TN removal rates of Example 2, Example 9, Example 10, and Example 11. The results are as Figure 11 shown. It can be seen from Figure 11 that when the pH of the S2 solution in Example 2 is 2, the TN removal effect is the best.

[0125] In summary, compared with the prior art, the following beneficial effects are achieved:

[0126] 1. The present invention has developed a short-process and highly efficient catalytic valence change combined process for classifying and treating the leachate of phosphogypsum stacks, which can simply and quickly treat ammonia nitrogen, total nitrogen, total phosphorus, and fluoride in the leachate of phosphogypsum stacks.

[0127] 2. The present invention is overall designed according to the characteristics of the leachate of phosphogypsum stacks. Combining the properties and types of pollutants, a catalytic valence change classification treatment combined process is adopted, saving a large amount of raw materials and effectively reducing the sludge volume and cost requirements.

[0128] 3. The chemical reagents and the like used in the present invention have low costs, few process flows, are simple and fast, and have low costs, and can be applied industrially.

[0129] 4. The order of the treatment process of the present invention cannot be adjusted. The method of treating the leachate of phosphogypsum stacks by breakpoint chlorination method and chemical precipitation method in sequence and step by step is simple and feasible, can effectively reduce the sludge volume, save time, and at the same time can effectively reduce costs and protect the environment.

[0130] 5. Figure 2 It shows in

[0131] that the hydroxy iron oxide presents a rod-like structure. After being modified with copper oxide, its original rod-like structure is not changed, and at the same time, it can effectively improve the photocatalytic effect of the copper oxide / hydroxy iron oxide composite material.

[0131] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

[0132] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A catalytic variable valence combination process for the leachate of phosphogypsum stack yard, characterized in that, The specific steps include: S1. Add a phosphorus-fluorine precipitant to the leachate of the phosphogypsum stack yard, adjust the pH to 7 - 8, mix evenly, add a PAM flocculant, and then filter. S2. Pass the clear liquid filtered in S1 into a photocatalytic reactor, add a copper oxide / hydroxy iron oxide (CuO / FeOOH) composite material, adjust the pH value to 2, react at room temperature, perform dark adsorption for 1 h, and photocatalyze for 2 h. S3. Centrifuge the suspension after the reaction in S2 through a centrifuge device. S4. Add an ammonia nitrogen remover to the clear liquid after centrifugation in S3, adjust the pH value to 7 - 8, and react at room temperature. S5. Add a phosphorus-fluorine precipitant to the solution after oxidation in S4, adjust the pH value to 11 - 12, mix evenly, add a PAM flocculant, and then filter. S6. Discharge the water.

2. The catalytic variable valence combination process for the leachate of phosphogypsum stack yard according to claim 1, characterized in that, The phosphorus-fluorine precipitants used in S1 and S5 are both Ca(OH)2.

3. The catalytic variable valence combination process for the leachate of phosphogypsum stack yard according to claim 1, characterized in that, In S2, CuO accounts for 1% - 20% of the total amount of the CuO / FeOOH composite material.

4. The catalytic variable valence combination process for the leachate of phosphogypsum stack yard according to claim 1, characterized in that, The mass concentration of copper oxide / hydroxy iron oxide in S2 is 20 - 50 mg / L.

5. The catalytic variable valence combination process for the leachate of phosphogypsum stack yard according to claim 1, characterized in that, The material used to adjust the pH in S2 is dilute sulfuric acid.

6. The catalytic variable valence combination process for the leachate of phosphogypsum stack yard according to claim 1, characterized in that, The ammonia nitrogen remover in S4 is any one of Cl2, NaClO, and HClO.

7. The catalytic variable valence combination process for the leachate of phosphogypsum stack yard according to claim 1, characterized in that, The material used to adjust the pH in S4 is calcium hydroxide solution.

8. The catalytic variable valence combination process for the leachate of phosphogypsum stack yard according to claim 1, characterized in that, The ammonia nitrogen content of the leachate of the phosphogypsum stack yard is 200 - 500 mg / L, the total phosphorus content is 1000 - 6000 mg / L, and the fluoride ion content is 500 - 2000 mg / L.

9. The catalytic variable valence combination process for the leachate of phosphogypsum stack yard according to claim 1, characterized in that, The ammonia nitrogen content in the water discharged after treatment in S6 is less than 10 mg / L, the total nitrogen content is less than 15 mg / L, the total phosphorus content is less than 0.5 mg / L, the fluoride ion content is less than 15 mg / L, the SS content is less than 30 mg / L, and the COD content is less than 50 mg / L, meeting the effluent standards of the Chaohu Lake Basin.

10. The catalytic variable valence combination process for the leachate of phosphogypsum stack yard according to claim 1, characterized in that, The total phosphorus removal rate of this process is 99.99%, and the fluoride removal rate is above 95%.

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