Method for whitening and removing impurities from solid waste phosphogypsum

Abstract

The invention relates to a whitening and impurity removing method for solid waste phosphogypsum, and belongs to the technical field of solid waste recovery treatment. The method comprises the following steps: adding water into ardealite raw ore powder for size mixing until the ore pulp concentration is 25-50wt%, carrying out ultrasonic washing and impurity removal to obtain washed ardealite ore powder, adding water for size mixing until the ore pulp concentration is 20-40wt%, adding a reverse flotation reagent, uniformly mixing, and carrying out reverse flotation for 3-10 minutes to obtain reverse flotation ardealite concentrate; the reverse flotation reagent comprises a collecting agent, a foaming agent and a pH regulator; and drying the reverse flotation phosphogypsum concentrate, grinding, and calcining at a high temperature of 400-600 DEG C to obtain phosphogypsum concentrate powder. According to the method, an impurity layer adsorbed on the surface of the ardealite mineral is damaged by bubbles generated by ultrasound and stable cavitation, so that the ardealite mineral falls off and is subjected to impurity removal; a specific reverse flotation collecting agent is adopted, NH2 < + > groups dissociated by the specific reverse flotation collecting agent under the acidic condition are differentially adsorbed on the surfaces of minerals such as gypsum and silicon dioxide, and the hydrophobicity of the surfaces of the minerals is changed so as to remove impurity minerals such as silicon dioxide; and after grinding, carrying out high-temperature calcination to remove residual organic matters.

Description

Technical Field

[0001] The invention relates to a method for whitening and removing impurities from solid waste phosphogypsum, belonging to the technical field of solid waste recycling and treatment. Background Art

[0002] Methods for improving the whiteness of phosphogypsum ore and the grade of concentrate include flotation and heat treatment. At present, the heat treatment method can be treated by high-temperature calcination or microwave sintering. Both methods can effectively remove phosphorus, fluorine and organic impurities in phosphogypsum. The heat treatment method for treating phosphogypsum has the characteristics of high heat and raw material utilization, but the treatment of by-products (gaseous sulfides, carbon dioxide, sulfur dioxide, etc.) is still a serious problem, and it cannot effectively treat solid impurity minerals. This process is suitable for phosphogypsum with high organic impurity content, and the basic investment and process energy consumption are high. The flotation method changes the hydrophobicity of the mineral surface by utilizing the differential adsorption of flotation agents on the mineral surface under different working environments; and then uses the surface tension effect of the fluid to adsorb the hydrophobic particles onto tiny bubbles and take them out. In the phosphogypsum system, the flotation collectors mainly include sodium oleate, kerosene, dodecylamine and dodecyltrimethylammonium chloride, but for traditional desiliconization collectors, such as dodecylamine and sodium oleate, their water solubility and selectivity are poor. The use of traditional desiliconization collectors to improve the whiteness of phosphogypsum ore and the grade of concentrate often requires a combination of reverse and forward flotation processes to perform closed-circuit flotation; this process requires multiple flotations, consumes a lot of water, and the wastewater produced poses a risk of secondary pollution to the environment and needs to be treated again before it can be discharged. Summary of the invention

[0003] In view of the problems that the flotation method for improving the whiteness of phosphogypsum ore and the grade of concentrate has the problems of poor water solubility and selectivity of the collector, the present invention proposes a method for whitening and removing impurities from solid waste phosphogypsum, that is, using bubbles and stable cavitation generated by ultrasound to destroy the impurity layer adsorbed on the surface of the phosphogypsum mineral, so that it falls off and impurities are removed; using a specific reverse flotation collector to utilize the NH2 dissociated under acidic conditions + The groups are differentially adsorbed on the surface of minerals such as gypsum and silica, changing the hydrophobicity of the mineral surface to remove impurity minerals such as silica; after grinding, high-temperature calcination is performed to remove residual organic matter. The whiteness of the phosphogypsum concentrate powder of the present invention can reach 80.1-83.2%, and the grade can reach 96.9-99.2%.

[0004] A method for whitening and removing impurities from solid waste phosphogypsum, the specific steps are as follows:

[0005] (1) drying the solid waste phosphogypsum ore and crushing it to a particle size of no more than 100 mesh to obtain phosphogypsum ore powder;

[0006] (2) adding water to the raw phosphogypsum ore powder to adjust the slurry concentration to 25-50 wt %, and ultrasonically washing to remove impurities to obtain washed phosphogypsum ore powder;

[0007] (3) washing the phosphogypsum powder with water and slurrying to a slurry concentration of 20-40 wt%, adding a reverse flotation agent and mixing evenly, and performing reverse flotation for 3-10 minutes to obtain a reverse flotation phosphogypsum concentrate; the reverse flotation agent includes a collector, a frother and a pH adjuster;

[0008] (4) Reverse flotation: The phosphogypsum concentrate is dried and ground, and then calcined at a temperature of 400-600°C to obtain phosphogypsum concentrate powder.

[0009] The whiteness of the solid waste phosphogypsum ore in step (1) is 29.5-32.4%, and the grade is 88.5-90.2%.

[0010] Preferably, the ultrasonic power in step (2) is 80 to 100 W, and the ultrasonic water washing and impurity removal time is 20 to 80 minutes.

[0011] Preferably, based on the washed phosphogypsum powder, the amount of collector added in the reverse flotation reagent in step (3) is 50-300 g / t, the amount of frother added is 50-300 g / t, and the pH value of the reverse flotation pulp is 1-2.

[0012] Preferably, the preparation method of the collector in step (3) comprises the following specific steps:

[0013] 1) Heat dodecylamine until it melts, add methyl acrylate dropwise under stirring, raise the temperature to 60-70° C. and react at a constant temperature for 1.5-3.5 hours to obtain a collector intermediate;

[0014] 2) The collector intermediate is heated to 90-95° C., and a sodium hydroxide solution is added dropwise under stirring and reacted at a constant temperature for 0.6-1.5 hours to obtain a collector.

[0015] More preferably, in step 1), the molar ratio of dodecylamine to methyl acrylate is 1:1.5-2.4.

[0016] More preferably, the concentration of the sodium hydroxide solution in step 2) is 5.5-6 mol / L, and the molar ratio of dodecylamine to sodium hydroxide in step 1) is 1:0.8-1:1.

[0017] Preferably, the foaming agent in step (3) is methyl isobutyl carbinol and the pH adjuster is sulfuric acid.

[0018] The whiteness of the phosphogypsum concentrate powder in step (4) is 80.1-83.2%, and the grade is 96.9-99.2%.

[0019] The present invention utilizes ultrasonic enhanced water washing of solid waste phosphogypsum ore to separate the sludge attached to the surface of the ore and separate it from the phosphogypsum ore to remove most of the sludge impurities in the phosphogypsum. In the reverse flotation process, a specific collector is used to utilize the NH2 + The groups are differentially adsorbed on the surfaces of minerals such as gypsum and silica, changing the hydrophobicity of the mineral surfaces. The surface tension effect of the fluid is then used to separate impurity minerals such as silica. Some of the coloring impurities and organic impurities on the surface of the phosphogypsum are then removed by calcination, greatly improving the whiteness of the phosphogypsum and the grade of the concentrate.

[0020] The beneficial effects of the present invention are:

[0021] (1) The present invention significantly improves the whiteness and grade of phosphogypsum concentrate through ultrasonic water washing-reverse flotation-calcination process;

[0022] (2) In the water washing process of the present invention, bubbles and stable cavitation generated by ultrasound are used to destroy the impurity layer adsorbed on the surface of the phosphogypsum mineral, causing it to fall off and remove impurities;

[0023] (3) The reverse flotation process of the present invention uses a specific collector, which has NH2 + 、-COO - Functional groups can change the hydrophobicity of the mineral surface and improve flotation efficiency;

[0024] (4) The entire process of the present invention is simple, the amount of additives used is small, and the calcination temperature and time are greatly reduced through water washing and flotation processes, thereby reducing energy consumption. The purified phosphogypsum concentrate has a higher whiteness and concentrate grade, meeting the conditions for high-value utilization of phosphogypsum. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 These are SEM images of solid waste phosphogypsum ore and phosphogypsum concentrate powder in Example 1, (a) and (b) are solid waste phosphogypsum ore, (c) and (d) are phosphogypsum concentrate powder;

[0026] Figure 2 This is the EDS spectrum analysis of the solid waste phosphogypsum ore in Example 1;

[0027] Figure 3 This is the EDS spectrum analysis of the phosphogypsum concentrate powder in Example 1;

[0028] Figure 4 The metallographic micrographs of the solid waste phosphogypsum ore in Example 1 are shown in Figures a to d at 50 times, 100 times, 200 times, and 500 times, respectively;

[0029] Figure 5 The metallographic micrographs of the phosphogypsum concentrate powder of Example 1, a to d are 50 times, 100 times, 200 times, and 500 times respectively;

[0030] Figure 6 is the infrared spectrum of the collector of Example 1;

[0031] Figure 7 This is the XRD spectrum of the phosphogypsum concentrate powder of Examples 1-4. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited to the described contents.

[0033] Embodiment 1: The preparation method of the collector of this embodiment comprises the following specific steps:

[0034] 1) Heat dodecylamine until it melts, add methyl acrylate dropwise under stirring, raise the temperature to 70°C and react at a constant temperature for 1.5 hours to obtain a collector intermediate; the molar ratio of dodecylamine to methyl acrylate is 1:1.8; the reaction formula is:

[0035]

[0036] 2) The collector intermediate is heated to 90° C., and a sodium hydroxide solution is added dropwise under stirring and reacted at a constant temperature for 1.5 hours to obtain a collector; the concentration of the sodium hydroxide solution is 6 mol / L, and the molar ratio of dodecylamine to sodium hydroxide in step 1) is 1:0.8; the reaction formula is:

[0037]

[0038] The infrared spectrum of the collector of this embodiment is shown in Figure 6 ,from Figure 6 It can be seen that at 3357cm -1 The strong absorption peak near 2852cm is due to the stretching vibration of the -OH group. -1 With 2923cm -1 The peaks at 1638cm are the absorption peaks produced by the stretching vibration of -CH3 and -CH2 groups. -1 The absorption peak at 1560cm is due to the stretching vibration of -COO-. -1 The absorption peak at 1403cm is due to the bending vibration of the NH bond. -1 The peak at 1110 cm -1 The absorption peak at is the bending vibration of -CH2; therefore, the synthesized collector product has amino and carboxyl functional groups in its structure;

[0039] A method for whitening and removing impurities from solid waste phosphogypsum, the specific steps are as follows:

[0040] (1) After the solid waste phosphogypsum ore is dried, it is crushed to a particle size of -100 mesh to obtain phosphogypsum ore powder; the content of each phase in the solid waste phosphogypsum ore of this embodiment is shown in Table 1;

[0041] Table 1 Content of each phase in solid waste phosphogypsum ore

[0042] phase of matter <![CDATA[CaSO4·2H2O]]> <![CDATA[CaPO3(OH)·2H2O]]> <![CDATA[SiO2]]> content(%) 90.25 2.16 3.56 phase of matter <![CDATA[CaF2]]> other — content(%) 2.03 2.00 —

[0043] (2) adding water to the raw phosphogypsum ore powder to prepare a slurry concentration of 25 wt %, and washing and removing impurities by ultrasonic (power of 80 W) for 80 min to obtain washed phosphogypsum ore powder;

[0044] (3) adding water to the washed phosphogypsum powder to adjust the pulp to a pulp concentration of 20wt%, adding reverse flotation reagents (collector, frother and pH adjuster) and mixing evenly, and performing reverse flotation for 3min to obtain reverse flotation phosphogypsum concentrate; the frother is methyl isobutyl carbinol, and the pH adjuster is sulfuric acid; based on the washed phosphogypsum powder, the amount of collector added in the reverse flotation reagent is 300g / t, the amount of frother (methyl isobutyl carbinol) added is 300g / t, and the pH value of the reverse flotation pulp is 2;

[0045] (4) The reverse flotation phosphogypsum concentrate is dried and ground, and then calcined at 600° C. for 60 min to obtain phosphogypsum concentrate powder;

[0046] The SEM images of the solid waste phosphogypsum ore and phosphogypsum concentrate powder in this example are shown in Figure 1 After the whitening process, the mineral impurities in the phosphogypsum concentrate powder and the sludge impurities attached to the surface are greatly reduced;

[0047] The EDS spectrum analysis of the solid waste phosphogypsum ore and phosphogypsum concentrate powder in this example is shown in Figure 2 and 3 Compared with the original ore, impurity elements such as Si, F, P, and Fe in the concentrate were not detected in the selected sample surface, and their content in the concentrate was greatly reduced;

[0048] In this embodiment, the phosphogypsum ore and the calcined concentrate treated by the whitening process were observed under a metallographic microscope. Specifically, the same position of the ore and the calcined concentrate was observed under a metallographic microscope at different magnifications for the distribution of impurities. The obtained metallographic micrographs are as follows: Figure 4 and 5 As shown, the impurities in the phosphogypsum after the whitening process are greatly reduced, indicating that the whitening process has a significant effect on the whitening and purification of phosphogypsum;

[0049] Phosphogypsum whiteness test method: Dry the phosphogypsum ore and the concentrate sample after whitening process and grind them into uniform powder. Use SBDY-1 whiteness meter to test the whiteness of the sample. Take the average value after three consecutive tests.

[0050] The whiteness of the phosphogypsum ore in this embodiment is 30.9%, and the grade is 90.2%; the whiteness of the phosphogypsum concentrate powder is 83.2%, and the grade is 99.2%, and the yield is 49.16%.

[0051] Embodiment 2: The preparation method of the collector of this embodiment comprises the following specific steps:

[0052] 1) Heat dodecylamine until it melts, add methyl acrylate dropwise under stirring, raise the temperature to 60°C and react at a constant temperature for 3.5 hours to obtain a collector intermediate; the molar ratio of dodecylamine to methyl acrylate is 1:1.5; the reaction formula is:

[0053]

[0054] 2) heating the collector intermediate to 95° C., dripping a sodium hydroxide solution dropwise under stirring and reacting at a constant temperature for 1.0 h to obtain a collector; the concentration of the sodium hydroxide solution is 5.5 mol / L, and the molar ratio of dodecylamine to sodium hydroxide in step 1) is 1:1;

[0055]

[0056] A method for whitening and removing impurities from solid waste phosphogypsum, the specific steps are as follows:

[0057] (1) After drying the solid waste phosphogypsum ore, the ore was crushed to a particle size of -100 mesh to obtain phosphogypsum ore powder; the content of each phase in the solid waste phosphogypsum ore of this embodiment is the same as that in Example 1;

[0058] (2) adding water to the raw phosphogypsum ore powder to prepare a slurry concentration of 50 wt %, and washing and removing impurities by ultrasonic (power of 100 W) for 20 min to obtain washed phosphogypsum ore powder;

[0059] (3) adding water to the washed phosphogypsum powder to adjust the slurry to a slurry concentration of 30 wt%, adding reverse flotation reagents (collector, frother and pH adjuster) and mixing evenly, and performing reverse flotation for 5 minutes to obtain reverse flotation phosphogypsum concentrate; the frother is methyl isobutyl carbinol, and the pH adjuster is sulfuric acid; based on the washed phosphogypsum powder, the amount of collector added in the reverse flotation reagent is 100 g / t, the amount of frother (methyl isobutyl carbinol) added is 100 g / t, and the pH value of the reverse flotation slurry is 1.2;

[0060] (4) The reverse flotation phosphogypsum concentrate is dried and ground, and then calcined at 500° C. for 80 min to obtain phosphogypsum concentrate powder;

[0061] The whiteness of the phosphogypsum ore in this embodiment is 30.9%, and the grade is 90.2%; the whiteness of the phosphogypsum concentrate powder is 80.7%, and the grade is 98.7%, and the yield is 57.26%.

[0062] Embodiment 3: The preparation method of the collector of this embodiment comprises the following specific steps:

[0063] 1) Heat dodecylamine until it melts, add methyl acrylate dropwise under stirring, raise the temperature to 65°C and react at a constant temperature for 2.5 hours to obtain a collector intermediate; the molar ratio of dodecylamine to methyl acrylate is 1:2.4; the reaction formula is:

[0064]

[0065] 2) heating the collector intermediate to 95° C., dripping a sodium hydroxide solution dropwise under stirring and reacting at a constant temperature for 0.6 h to obtain a collector; the concentration of the sodium hydroxide solution is 5.5 mol / L, and the molar ratio of dodecylamine to sodium hydroxide in step 1) is 1:1;

[0066]

[0067] A method for whitening and removing impurities from solid waste phosphogypsum, the specific steps are as follows:

[0068] (1) After drying the solid waste phosphogypsum ore, the ore was crushed to a particle size of -100 mesh to obtain phosphogypsum ore powder; the content of each phase in the solid waste phosphogypsum ore of this embodiment is the same as that in Example 1;

[0069] (2) adding water to the raw phosphogypsum ore powder to prepare the slurry to a slurry concentration of 37.5 wt %, and washing and removing impurities by ultrasonic (power of 90 W) for 40 min to obtain washed phosphogypsum ore powder;

[0070] (3) adding water to the washed phosphogypsum powder to adjust the pulp to a pulp concentration of 40wt%, adding reverse flotation reagents (collector, frother and pH adjuster) and mixing evenly, and performing reverse flotation for 5 minutes to obtain reverse flotation phosphogypsum concentrate; the frother is methyl isobutyl carbinol, and the pH adjuster is sulfuric acid; based on the washed phosphogypsum powder, the amount of collector added in the reverse flotation reagent is 50g / t, the amount of frother (methyl isobutyl carbinol) added is 50g / t, and the pH value of the reverse flotation pulp is 1.1;

[0071] (4) The reverse flotation phosphogypsum concentrate is dried and ground, and then calcined at 500° C. for 90 min to obtain phosphogypsum concentrate powder;

[0072] The whiteness of the phosphogypsum ore in this embodiment is 30.9%, and the grade is 90.2%; the whiteness of the phosphogypsum concentrate powder is 80.1%, and the grade is 96.9%, and the yield is 57.49%.

[0073] Embodiment 4: The preparation method of the collector of this embodiment comprises the following specific steps:

[0074] 1) Heat dodecylamine until it melts, add methyl acrylate dropwise under stirring, raise the temperature to 65°C and react at a constant temperature for 2 hours to obtain a collector intermediate; the molar ratio of dodecylamine to methyl acrylate is 1:1.8; the reaction formula is:

[0075]

[0076] 2) heating the collector intermediate to 90° C., adding a sodium hydroxide solution dropwise under stirring and reacting at a constant temperature for 1.2 h to obtain a collector; the concentration of the sodium hydroxide solution is 5.8 mol / L, and the molar ratio of dodecylamine to sodium hydroxide in step 1) is 1:1;

[0077]

[0078] A method for whitening and removing impurities from solid waste phosphogypsum, the specific steps are as follows:

[0079] (1) After drying the solid waste phosphogypsum ore, the ore was crushed to a particle size of -100 mesh to obtain phosphogypsum ore powder; the content of each phase in the solid waste phosphogypsum ore of this embodiment is the same as that in Example 1;

[0080] (2) adding water to the raw phosphogypsum ore powder to adjust the slurry concentration to 37.5 wt %, and washing and removing impurities by ultrasonic (power of 100 W) for 40 min to obtain washed phosphogypsum ore powder;

[0081] (3) adding water to the washed phosphogypsum powder to adjust the pulp to a pulp concentration of 20wt%, adding reverse flotation reagents (collector, frother and pH adjuster) and mixing evenly, and performing reverse flotation for 5 minutes to obtain reverse flotation phosphogypsum concentrate; the frother is methyl isobutyl carbinol, and the pH adjuster is sulfuric acid; based on the washed phosphogypsum powder, the amount of collector added in the reverse flotation reagent is 300g / t, the amount of frother (methyl isobutyl carbinol) added is 300g / t, and the pH value of the reverse flotation pulp is 1.5;

[0082] (4) The reverse flotation phosphogypsum concentrate is dried and ground, and then calcined at 400° C. for 100 min to obtain phosphogypsum concentrate powder;

[0083] The XRD spectra of phosphogypsum concentrate powder of Example 1-4 are shown in Figure 7 ,from Figure 7It can be seen that the main phase components of the phosphogypsum concentrate powder of Example 1-4 are calcium sulfate and silicon dioxide; compared with the phosphogypsum ore, the characteristic peaks of calcium phosphate (CaPO3(OH)·2H2O) and calcium fluoride (CaF2) in the concentrate basically disappear, indicating that mineral impurities such as calcium phosphate in the phosphogypsum have been basically removed. Then, using Jade9 software, the XRD pattern of the phosphogypsum concentrate powder was quantitatively analyzed. The results showed that the concentrate grade of calcium sulfate in the phosphogypsum concentrate powder reached 96.9% to 99.2%;

[0084] Under the condition that the particle size of phosphogypsum raw ore powder is -100 mesh, in the whitening process, the whiteness, grade and yield of phosphogypsum concentrate powder under different process conditions are shown in Table 2;

[0085] Table 2 Whiteness, grade and yield of phosphogypsum concentrate powder under different process conditions

[0086]

[0087] The whiteness of the phosphogypsum ore in this embodiment is 30.9%, and the grade is 90.2%; the whiteness of the phosphogypsum concentrate powder is 81.3%, and the grade is 97.7%, and the yield is 55.62%.

[0088] The specific implementation modes of the present invention are described in detail above, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for whitening and removing impurities from solid waste phosphogypsum, characterized in that: The specific steps are as follows: (1) drying the solid waste phosphogypsum ore and crushing it to a particle size of no more than 100 mesh to obtain phosphogypsum ore powder; (2) adding water to the raw phosphogypsum ore powder to adjust the slurry concentration to 25-50 wt %, and ultrasonically washing to remove impurities to obtain washed phosphogypsum ore powder; (3) washing the phosphogypsum powder with water and slurrying to a slurry concentration of 20-40 wt%, adding a reverse flotation agent and mixing evenly, and performing reverse flotation for 3-10 minutes to obtain a reverse flotation phosphogypsum concentrate; the reverse flotation agent includes a collector, a frother and a pH adjuster; (4) Reverse flotation: The phosphogypsum concentrate is dried and ground, and then calcined at a temperature of 400-600°C to obtain phosphogypsum concentrate powder.

2. The method for whitening and removing impurities from solid waste phosphogypsum according to claim 1, characterized in that: The whiteness of the solid waste phosphogypsum ore in step (1) is 29.5-32.4%, and the grade is 88.5-90.2%.

3. The method for whitening and removing impurities from solid waste phosphogypsum according to claim 1, characterized in that: The ultrasonic power of step (2) is 80-100W, and the ultrasonic washing and impurity removal time is 20-80min.

4. The method for whitening and removing impurities from solid waste phosphogypsum according to claim 1, characterized in that: Based on the washed phosphogypsum powder, the amount of collector added to the reverse flotation reagent in step (3) is 50-300 g / t, the amount of frother added is 50-300 g / t, and the pH value of the reverse flotation pulp is 1-2.

5. The method for whitening and removing impurities from solid waste phosphogypsum according to claim 1, characterized in that: The preparation method of the collector in step (3) comprises the following specific steps: 1) Heat dodecylamine until it melts, add methyl acrylate dropwise under stirring, raise the temperature to 60-70° C. and react at a constant temperature for 1.5-3.5 hours to obtain a collector intermediate; 2) The collector intermediate is heated to 90-95° C., and a sodium hydroxide solution is added dropwise under stirring and reacted at a constant temperature for 0.6-1.5 hours to obtain a collector.

6. The method for whitening and removing impurities from solid waste phosphogypsum according to claim 5, characterized in that: In the step 1), the molar ratio of dodecylamine to methyl acrylate is 1:1.5-2.

4.

7. The method for whitening and removing impurities from solid waste phosphogypsum according to claim 5, characterized in that: The concentration of the sodium hydroxide solution in step 2) is 5.5-6 mol / L, and the molar ratio of dodecylamine to sodium hydroxide in step 1) is 1:0.8-1:

1.

8. The method for whitening and removing impurities from solid waste phosphogypsum according to claim 1, characterized in that: In step (3), the foaming agent is methyl isobutyl carbinol, and the pH adjusting agent is sulfuric acid.

9. The method for whitening and removing impurities from solid waste phosphogypsum according to claim 1, characterized in that: The whiteness of the phosphogypsum concentrate powder in step (4) is 80.1-83.2%, and the grade is 96.9-99.2%.

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