A flotation depressant for whitening and upgrading of phosphogypsum and a preparation method and application thereof

Abstract

The application discloses a flotation inhibitor for whitening and upgrading of phosphogypsum, and a preparation method and application thereof. First, a polysaccharide inhibitor and a high-molecular inhibitor are uniformly mixed with water, heated and dissolved, and then a mixture of inorganic inhibitors, organic small-molecule inhibitors and polyphenol inhibitors is added thereto, and stirring is conducted until all the inhibitors are dissolved to obtain a compounded flotation inhibitor. When the prepared flotation inhibitor is used for flotation of the phosphogypsum, the content of CaSO4.2H2O and the whiteness of the phosphogypsum can be significantly improved, the content of SiO2 is reduced to about 0.5%, the purity and the recovery rate of the phosphogypsum are significantly improved, the loss of phosphorus resources is reduced, the resource utilization of the phosphogypsum is promoted, and the stock pressure is reduced.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization technology of bulk solid waste phosphogypsum, specifically relating to a flotation inhibitor for whitening and upgrading phosphogypsum, its preparation method and application. Background Technology

[0002] Phosphogypsum is a solid waste produced in the wet-process phosphoric acid production process. It is a nearly unused byproduct of phosphate fertilizer production and is classified as a hazardous waste pollutant. Because phosphogypsum contains highly corrosive chemical elements such as phosphorus, fluorine, and free acids, its rough dumping methods have a negative impact on the environment. Specifically, it can cause pollution of groundwater, surface water, soil, and vegetation cover by substances seeping into protective barriers, and may also lead to dust storms and landslides. Currently, the requirement for bulk solid waste is a comprehensive utilization rate of 60% and an orderly reduction in stock. However, how to achieve comprehensive disposal and resource utilization of phosphogypsum has always been a global challenge. Currently, phosphogypsum is mainly used to produce high-value, high-whiteness, and ultra-high-strength high-grade gypsum new materials. However, the main difficulty in its production lies in the high impurity content and low whiteness of phosphogypsum. In particular, phosphogypsum produced by the wet-process phosphoric acid process contains organic matter, and the organic flotation reagents in the concentrate slurry carbonize during sulfuric acid extraction, causing the phosphogypsum to turn black, thus affecting the color of subsequent products. Furthermore, phosphogypsum also contains organic impurities and small amounts of silica and metal ions such as iron, magnesium, and aluminum, generally appearing light yellow, light gray, or grayish-black with low whiteness, greatly increasing the difficulty of safe resource utilization. Therefore, the main applications of phosphogypsum are still limited to cement retarders and paper-faced gypsum board. Nowadays, the advantages of high-quality, high-whiteness gypsum in building wall materials and functional fillers are becoming increasingly apparent. Therefore, research on impurity removal and whitening technology for phosphogypsum is of great value for broadening the application fields of phosphogypsum and realizing its high-value utilization.

[0003] Currently, there are many methods for removing impurities and whitening phosphogypsum both domestically and internationally, such as calcination, flotation, leaching, bleaching, and combined processes of the above methods. Among these, flotation is the most widely used method in the mineral processing industry. It can remove organic matter floating on the surface, achieving the purpose of purification and whitening. Therefore, it also has broad application prospects in the removal and whitening of phosphogypsum. At present, the flotation of phosphogypsum mainly focuses on reverse flotation, double reverse flotation, and simultaneous reverse flotation with mixed reagents. Most of the reagents studied are collectors, while research on phosphogypsum flotation modifiers is relatively limited. Chinese patent CN115400881A discloses a method for purifying and whitening phosphogypsum, which adds sulfuric acid as a modifier to the decolorized slurry. This not only adjusts the pH for flotation but also inhibits unreacted P2O5 and metal oxides in the phosphogypsum. Chinese patent CN115957888A discloses a phosphogypsum reverse flotation whitening and impurity removal agent and its preparation method and process, which uses tributyl phosphate, terpineol, and fatty alkyl (R) carbon chain lengths of C 12 -C 20 The carbon chain length of the aliphatic primary amine (R-NH2) and aliphatic alkyl (R) is C. 12 -C 20 A reagent prepared by compounding dimethyl tertiary amine (RN(CH3)2) can improve the selectivity for organic carbon and capture black organic carbon, iron impurities, and silica under acidic conditions. Meanwhile, the collectors used in various flotation processes for whitening and purifying phosphogypsum generally have the following shortcomings: Amine collectors mainly rely on physical adsorption, removing impurities or floating phosphogypsum through positive and negative charge adsorption, resulting in poor selectivity, high phosphogypsum loss in tailings, and incomplete removal of silica gangue. Fatty acid collectors have poor selectivity, are not resistant to hard water, and are sensitive to temperature, generally requiring mixing with other types of collectors or additives.

[0004] In conclusion, in order to improve the impurity removal and whitening effect of phosphogypsum in the flotation process, it is necessary to develop an additive to help improve the collector's ability, improve the quality of phosphogypsum, thereby increasing its comprehensive utilization rate and alleviating the stockpiling pressure of phosphogypsum. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a flotation inhibitor for whitening and improving phosphogypsum, its preparation method, and its application. A flotation inhibitor is obtained by compounding inorganic inhibitors, small organic molecule inhibitors, polysaccharide inhibitors, polyphenol inhibitors, and polymeric inhibitors. This inhibitor can enhance the separation and collection capabilities of amine collectors during the phosphogypsum flotation process, reduce the impurity content in phosphogypsum, and increase the purity and recovery rate of phosphogypsum.

[0006] To achieve the above objectives, the present invention provides a flotation inhibitor for whitening and improving phosphogypsum, comprising an inorganic inhibitor, an organic small molecule inhibitor, a polysaccharide inhibitor, a polyphenol inhibitor, and a polymer inhibitor in a mass ratio of (10-15):(22-30):(30-48):(12-22):(6-14).

[0007] Preferably, the inorganic inhibitor is any one of sodium fluorosilicate, fluorosilicic acid, water glass, and potassium dichromate.

[0008] Preferably, the organic small molecule inhibitor is any one of citric acid, mercaptoacetic acid, oxalic acid, maleic anhydride, and nonylphenyl tetraethylene glycol ether.

[0009] Preferably, the polysaccharide inhibitor is any one of aminoethyl starch, hydroxyethyl cellulose, carboxymethyl cellulose, and methyl carboxylate guar gum.

[0010] Preferably, the polyphenol inhibitor is any one of tannin, lignin, white privet bark sap, vitex bark sap, and calcium lignin sulfonate.

[0011] Preferably, the polymer inhibitor is any one of polyvinylpyrrolidone, lecithin, and alginate.

[0012] This invention also provides a method for preparing a flotation inhibitor for whitening and improving phosphogypsum, comprising the following steps:

[0013] (1) Mix polysaccharide inhibitor, polymer inhibitor and water in a certain proportion, stir and heat to 90°C to prepare solution 1;

[0014] (2) Weigh out the inorganic inhibitor, the organic small molecule inhibitor and the polyphenol inhibitor in proportion, mix and stir evenly to prepare a mixture;

[0015] (3) Add the mixture obtained in step (2) to the solution 1 obtained in step (1) and stir thoroughly until all solid substances are dissolved to prepare a flotation inhibitor.

[0016] Preferably, the mass ratio of the polysaccharide inhibitor, the polymer inhibitor and water in step (1) is 30-48:6-14:300-480.

[0017] This invention also provides the application of a flotation inhibitor for whitening and upgrading phosphogypsum in the flotation of phosphogypsum. The steps of phosphogypsum flotation are as follows:

[0018] (1) Prepare a slurry with a concentration of 25-40% by adding water to phosphogypsum, then add a pH adjuster to make the pH value of the slurry 2.0-2.3, and then add a decolorizing collector for reverse flotation to obtain a decolorized slurry;

[0019] (2) After adding flotation inhibitors and amine collectors to the decolorized slurry, positive flotation roughing is carried out to obtain roughing tailings and roughing concentrate;

[0020] (3) Add pH adjuster to adjust the pH value to 2.0-2.3 to the obtained rough concentrate, and then perform two-stage cleaning to obtain fine foam II and middlings I and middlings II;

[0021] (4) After merging middlings I and middlings II, add a pH adjuster to adjust the pH value to 2.0-2.3, and add flotation inhibitors and amine collectors for re-selection to obtain re-selected tailings and concentrate;

[0022] (5) Combine the selected foam II obtained in step (3) and the concentrate obtained in step (4), and prepare the whitened and upgraded phosphogypsum by concentration, filtration and drying.

[0023] (6) The rough tailings obtained in step (2) are scavenged to obtain middlings II and tailings;

[0024] (7) Combine the re-selected tailings obtained in step (4) and the roughing tailings obtained in step (6) and return them to step (2) for positive flotation roughing.

[0025] The pH adjuster is a 15% sulfuric acid solution.

[0026] The dosage of the decolorizing collector is 0.5-1 kg / t, the dosage of the amine collector is 0.05-0.15 kg / t, and the dosage of the flotation inhibitor is 0.05-0.2 kg / t.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. A flotation inhibitor was obtained by combining inorganic inhibitors, small organic molecule inhibitors, polysaccharide inhibitors, polyphenol inhibitors, and polymer inhibitors. This inhibitor can effectively suppress impurities such as silicon, dolomite, and unreacted phosphate rock in phosphogypsum, improve flotation efficiency, reduce the impurity content of the prepared phosphogypsum, and improve the purity of phosphogypsum.

[0029] 2. When compound flotation inhibitors are used in combination with amine collectors, they can help enhance the separation and collection capabilities of amine collectors in phosphogypsum flotation, significantly reduce the impurity content in the concentrate, and increase the purity and recovery rate of the concentrate phosphogypsum.

[0030] 3. The phosphogypsum decolorization flotation process, through a step-by-step decolorization and three-stage purification process, can effectively remove organic matter, carbon slag, and silica gangue mineral impurities from phosphogypsum, improving its whiteness and purity. The two scavenging processes reduce the losses during phosphogypsum flotation and minimize the pressure of tailings phosphogypsum stockpiling. The middlings merging and re-selection process is more efficient and direct, not only improving the phosphogypsum recovery rate and significantly reducing the impurity content of concentrate phosphogypsum, but also reducing the output of tailings phosphogypsum and alleviating the pressure of tailings phosphogypsum stockpiling.

[0031] 4. The combined use of flotation inhibitors and amine collectors, along with the decolorization flotation process, allows the prepared phosphogypsum to achieve a CaSO4·2H2O content of 97.3%, a whiteness of 66.7%, and a SiO2 impurity content of 0.36%. This significantly improves the quality of phosphogypsum, facilitates its deep resource utilization, and reduces the pressure of phosphogypsum stockpiling. Attached Figure Description

[0032] Figure 1 This is a flow chart of the phosphogypsum flotation process in Example 9. Detailed Implementation

[0033] The technical solution of the present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.

[0034] Flotation reagents:

[0035] Decolorizing collector: contains a foaming agent and a collector in a mass ratio of 2:3; the collector is a non-polar hydrocarbon oil, and is at least one of kerosene, coal tar, pine oil, fuel oil, shale tar and wood tar; the foaming agent is a neutral fatty alcohol foaming agent, and is at least one of terpineol, pentanol, octanol and benzyl alcohol.

[0036] Amine collectors: at least one of dodecylamine, tetradecylamine, and octadecylamine. Before use, they are mixed with hydrochloric acid at a mass ratio of 5:4 and dissolved in hot water to obtain hydrochloric acidified amine collectors.

[0037] Example 1

[0038] (1) Accurately weigh 39 parts of hydroxyethyl cellulose and 10 parts of polyvinylpyrrolidone, mix them with 390 parts of water, and slowly stir while heating to 90°C to prepare solution 1.

[0039] (2) Accurately weigh 12 parts of sodium fluorosilicate, 23 parts of maleic anhydride and 20 parts of white pea bark juice, mix and stir evenly to obtain a mixture;

[0040] (3) Add all the mixture obtained in step (2) to the solution 1 obtained in step (1) and stir thoroughly until all the substances are dissolved to obtain flotation inhibitor I.

[0041] Example 2

[0042] The method and steps are the same as in Example 1, except that the formulation of the flotation inhibitor is changed to a compound combination of fluorosilicic acid, maleic anhydride, hydroxyethyl cellulose, Vitex bark sap, and polyvinylpyrrolidone in a mass ratio of 15:28:35:20:12.

[0043] Example 3

[0044] The method and steps are the same as in Example 1, except that the formulation of the flotation inhibitor is changed to sodium fluorosilicate, nonylphenyl tetraethylene glycol ether, methyl carboxylate guar gum, white jasmine bark sap, and polyvinylpyrrolidone in a mass ratio of 15:30:32:17:8.

[0045] Example 4

[0046] The method and steps are the same as in Example 1, except that the formulation of the flotation inhibitor is changed to a compound of fluorosilicic acid, mercaptoacetic acid, aminoethyl starch, white pine bark juice, and alginic acid in a mass ratio of 10:24:34:18:9.

[0047] Example 5

[0048] The method and steps are the same as in Example 1, except that the formulation of the flotation inhibitor is changed to a combination of glass, nonylphenyl tetraethylene glycol ether, aminoethyl starch, Vitex bark juice, and polyvinylpyrrolidone in a mass ratio of 11:26:33:17:12.

[0049] Example 6

[0050] The method and steps are the same as in Example 1, except that the flotation inhibitor is formulated as a mixture of water glass, maleic anhydride, methyl carboxylate guar gum, lignin, and polyvinylpyrrolidone in a mass ratio of 13:28:36:19:13.

[0051] Example 7

[0052] The method and steps are the same as in Example 1, except that the flotation inhibitor is formulated as a compound of sodium fluorosilicate, oxalic acid, hydroxyethyl cellulose, calcium lignosulfonate, and lecithin in a mass ratio of 10:23:39:15:9.

[0053] Example 8

[0054] The method and steps are the same as in Example 1, except that the flotation inhibitor is formulated as a compound of sodium fluorosilicate, citric acid, hydroxyethyl cellulose, tannin, and alginic acid in a mass ratio of 15:26:45:21:14.

[0055] Example 9: Flotation of phosphogypsum

[0056] Flotation was performed on a Yunnan phosphogypsum sample with a CaSO4·2H2O content of 84.1%, a whiteness of 32.2%, and a SiO2 content of 11.2%. The flotation process flow is as follows: Figure 1 The study investigated the effect of flotation inhibitors on the whitening and quality improvement of phosphogypsum, specifically including the following steps:

[0057] (1) In a mixing tank, phosphogypsum is mixed with water to prepare a slurry with a mass concentration of 30%, sulfuric acid solution with a volume concentration of 15% is added to adjust the pH of the slurry to 2.0, and then 0.7 kg / t of TC decarbonization combined collector is added for reverse flotation decolorization to obtain the decolorized slurry.

[0058] (2) Add 0.15 kg / t of the flotation inhibitor prepared in Examples 1-8 to the dewatered slurry, and then add 0.1 kg / t of amine collector and perform positive flotation roughing to obtain roughing concentrate and roughing tailings respectively.

[0059] (3) Add a 15% sulfuric acid solution to the rough concentrate, adjust the pH to 2.1, and then perform two-stage cleaning to finally obtain cleaned foam II and middlings I and middlings II;

[0060] (4) After combining middlings I and middlings II, add 15% sulfuric acid solution to adjust the pH to 2.1. At the same time, add 0.06 kg / t of the flotation inhibitor prepared in Examples 1-8 and 0.05 kg / t of amine collector and then perform re-selection to obtain re-selected tailings and concentrate.

[0061] (5) Combine the selected foam II obtained in step (3) and the concentrate obtained in step (4), and prepare the whitened and upgraded phosphogypsum by concentration, filtration and drying at 45°C.

[0062] (6) The rough tailings obtained in step (2) are scavenged to obtain middlings II and tailings;

[0063] (7) Combine the re-selected tailings obtained in step (4) and the roughing tailings obtained in step (6) and return to step (2) for positive flotation roughing.

[0064] Comparative Example 1

[0065] The method and steps are the same as in Example 9, except that flotation inhibitors are not added in steps (2) and (4) to prepare phosphogypsum after whitening and quality improvement.

[0066] Comparative Example 2

[0067] The method and steps are the same as in Example 9, except that water-soluble starch is added as a flotation inhibitor in steps (2) and (4) to prepare phosphogypsum after whitening and quality improvement.

[0068] Comparative Example 3

[0069] The method and steps are the same as in Example 9, except that water glass is added as a flotation inhibitor in steps (2) and (4) to prepare phosphogypsum after whitening and quality improvement.

[0070] Comparative Example 4

[0071] The method and steps are the same as in Example 9, except that carboxymethyl cellulose is added as a flotation inhibitor in steps (2) and (4) to prepare phosphogypsum after whitening and quality improvement.

[0072] Comparative Example 5

[0073] The method and steps are the same as in Example 9, except that the flotation inhibitor added in steps (2) and (4) is replaced with a flotation inhibitor obtained by compounding fluorosilicic acid and maleic anhydride in a mass ratio of 10:22, and the whitened and improved phosphogypsum is prepared.

[0074] Comparative Example 6

[0075] The method and steps are the same as in Example 9, except that the flotation inhibitor added in steps (2) and (4) is replaced with a flotation inhibitor obtained by compounding water glass, hydroxyethyl cellulose and tannin in a mass ratio of 15:22:14, and the whitened and improved phosphogypsum is prepared.

[0076] Comparative Example 7

[0077] The method and steps are the same as in Example 9, except that the flotation inhibitor added in steps (2) and (4) is replaced with a flotation inhibitor obtained by compounding fluorosilicic acid, oxalic acid, lignin and alginic acid in a mass ratio of 15:30:22:14, and the whitened and improved phosphogypsum is prepared.

[0078] Results: The whitened and upgraded phosphogypsum prepared using the flotation inhibitors obtained in Examples 1-8 and the whitened and upgraded phosphogypsum prepared in Comparative Examples 1-4 were compared. The contents of CaSO4·2H2O and SiO2 were measured, and the whiteness was also measured. The results are shown in the table below:

[0079]

[0080]

[0081] The above data shows that when flotation inhibitors are obtained by combining inorganic inhibitors, small organic molecule inhibitors, polysaccharide inhibitors, polyphenol inhibitors, and polymeric inhibitors, and then used in the flotation of phosphogypsum, the quality of phosphogypsum can be significantly improved. Specifically, the content of CaSO4·2H2O can be increased to over 95.9%, an increase of over 11%; the content of SiO2 can be reduced from 11.2% to below 0.62%; and the whiteness can be increased from 32.2% to over 65.8%. This significantly improves the purity and whiteness of the prepared phosphogypsum and significantly reduces the impurity content. Compared with phosphogypsum without flotation, although the content of CaSO4·2H2O and whiteness of phosphogypsum can be increased to some extent when no flotation inhibitor is added during the flotation process (Comparative Example 1) or only one inhibitor is used (Comparative Examples 2-4), the SiO2 content of the prepared phosphogypsum is as high as 6%-9%, indicating a high impurity content, making subsequent resource utilization still difficult.

[0082] Flotation inhibitors prepared by combining two, three, or four of the following inhibitors—inorganic inhibitors, small organic molecule inhibitors, polysaccharide inhibitors, polyphenol inhibitors, and polymeric inhibitors—showed a certain degree of improvement in the CaSO4·2H2O content and whiteness of phosphogypsum when applied to its flotation compared to using only one of these inhibitors. However, this improvement was not significant. Furthermore, the flotation effect on phosphogypsum was enhanced with the increase in the number of inhibitors in the flotation inhibitor, but all results were significantly lower than those obtained by combining the five inhibitors. This indicates that the combination of these five inhibitor raw materials has a synergistic effect on the flotation of phosphogypsum.

[0083] In Comparative Example 3, when water glass (an inorganic depressant) was used as the flotation depressant, the content and whiteness of CaSO4·2H2O after phosphogypsum flotation were the lowest, indicating that the inorganic depressant had the weakest flotation effect on phosphogypsum. However, when the inorganic depressant was combined with other types of depressants such as small organic molecule depressants, the flotation effect on phosphogypsum was significantly improved, but there is still considerable room for improvement.

Claims

1. The application of a flotation inhibitor for whitening and upgrading phosphogypsum in the flotation of phosphogypsum, characterized in that: The flotation inhibitors include inorganic inhibitors, small organic molecule inhibitors, polysaccharide inhibitors, polyphenol inhibitors, and polymeric inhibitors in a mass ratio of (10-15):(22-30):(30-48):(12-22):(6-14); the small organic molecule inhibitors are any one of citric acid, mercaptoacetic acid, oxalic acid, maleic anhydride, and nonylphenyl tetraethylene glycol ether; the polysaccharide inhibitors are any one of aminoethyl starch, hydroxyethyl cellulose, carboxymethyl cellulose, and methyl carboxylate guar gum.

2. The application according to claim 1, characterized in that: The inorganic inhibitor is any one of sodium fluorosilicate, fluorosilicic acid, water glass, and potassium dichromate.

3. The application according to claim 1, characterized in that: The polyphenol inhibitor is any one of tannin, lignin, white privet bark sap, vitex bark sap, and calcium lignin sulfonate.

4. The application according to claim 1, characterized in that: The polymeric inhibitor is any one of polyvinylpyrrolidone, lecithin, and alginate.

5. The application according to claim 1, characterized in that: The amount of flotation inhibitor used in the application is 0.05-0.2 kg / t.

6. A method for preparing a flotation inhibitor for whitening and improving phosphogypsum as described in any one of claims 1-5, characterized in that: Includes the following steps: (1) Mix polysaccharide inhibitors, polymer inhibitors and water in a certain proportion, stir and heat to prepare solution 1; (2) Weigh out the inorganic inhibitor, the organic small molecule inhibitor and the polyphenol inhibitor in proportion, mix and stir evenly to prepare a mixture; (3) Add the mixture obtained in step (2) to the solution 1 obtained in step (1) and stir thoroughly until all solid substances are dissolved to obtain the flotation inhibitor.

7. The preparation method according to claim 6, characterized in that: The temperature after heating in step (1) is 90-95℃, and the mass ratio of polysaccharide inhibitor, polymer inhibitor and water is 30-48:6-14:300-480.

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