A method for purifying and whitening phosphogypsum

Abstract

The invention discloses a method for purifying and whitening phosphogypsum, which belongs to the technical field of comprehensive utilization of solid waste. The method for purifying and whitening phosphogypsum comprises the following steps: (1) adding water to phosphogypsum to prepare ore pulp, decolorizing the ore pulp to obtain decolorized ore pulp; (2) adding a collector to the decolorized ore pulp, adding a pH regulator, adjusting the pH to 2.0-2.5, performing a first positive flotation, and obtaining a first flotation liquid; (3) adding the pH regulator to the first flotation liquid, adjusting the pH to 2.0-2.5, performing a second positive flotation, and obtaining a second flotation liquid; (4) adding the pH regulator to the second flotation liquid, adjusting the pH to 2.0-2.5, performing a third positive flotation, concentrating, filtering, and drying to obtain refined phosphogypsum. The method can prepare phosphogypsum with high purity and high whiteness, effectively reduce the storage of phosphogypsum, and relieve environmental pressure.

Description

Technical Field

[0001] The invention relates to the technical field of comprehensive utilization of solid wastes, and in particular to a method for purifying and whitening phosphogypsum. Background Art

[0002] Phosphogypsum is an industrial solid waste in the phosphate fertilizer chemical industry. The stacking of phosphogypsum will bring many hidden dangers. Phosphogypsum is in powder form. It is easy to form dust under long-term sun exposure, affecting the atmospheric environment. If it is drenched by rain, it will cause harmful impurities such as various salts containing water-soluble P2O5 and F ions in the phosphogypsum to flow out easily. Phosphogypsum is a fluid plastic object. If it is not handled properly, acidic polluted water containing impurities will leak or overflow and enter surface water, groundwater or soil, which will cause irreversible water, soil and plant pollution. Phosphogypsum is also listed as a major hazard source by the national safety supervision department. Once the phosphogypsum reservoir collapses, it will cause huge losses to life and property downstream. The large-scale accumulation of phosphogypsum has caused serious social and environmental problems. Its comprehensive utilization and governance are urgent. Solving the comprehensive utilization of phosphogypsum is of great significance.

[0003] Processing phosphogypsum as a building material is an important means to reduce the stockpile of phosphogypsum. However, phosphogypsum cannot be used directly as a building material. It needs to be purified before use to improve its purity and whiteness so that it can be used in the construction field. Therefore, how to improve the whiteness and purity of phosphogypsum has become a technical problem that needs to be urgently solved by technicians in this field. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for purifying and whitening phosphogypsum, which can prepare high-purity and high-whiteness phosphogypsum, effectively reduce the storage of phosphogypsum, and alleviate environmental pressure.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for purifying and whitening phosphogypsum comprises the following steps:

[0007] (1) adding water to phosphogypsum to prepare a slurry, and decolorizing the slurry to obtain a decolorized slurry;

[0008] (2) adding a collector to the decolorized ore pulp, adding a pH adjuster, adjusting the pH to 2.0-2.5, performing a first positive flotation, and obtaining a first flotation liquid;

[0009] (3) adding the pH adjusting agent to the first flotation liquid to adjust the pH to 2.0-2.5, and performing a second positive flotation to obtain a second flotation liquid;

[0010] (4) adding the pH adjusting agent to the second flotation liquid to adjust the pH to 2.0-2.5, performing a third positive flotation, concentrating, filtering, and drying to obtain refined phosphogypsum.

[0011] The present invention can effectively remove impurities and decolorize the phosphogypsum by decolorizing the phosphogypsum (reverse flotation) and then performing three positive flotations, so that organic matter, carbon slag, silicon and other impurities in the phosphogypsum can be effectively removed, thereby preparing high-purity phosphogypsum with high whiteness and purity.

[0012] In the present invention, the unreacted phosphorus pentoxide and metal oxides in the phosphogypsum can be dissolved by adjusting the pH to 2.0-2.5 during the three positive flotations, thereby further improving the whiteness and purity of the phosphogypsum.

[0013] The inventors of the present invention have found through extensive research that in the process of positive flotation purification and whitening, the pH is a key parameter affecting purification and whitening. If the pH is too low or too high, it will lead to poor dissolution of phosphorus pentoxide and metal oxides, thereby reducing the whiteness and purity of phosphogypsum.

[0014] It should be noted that in the present invention, the forward flotation is carried out in an ordinary flotation cell. The forward flotation and reverse flotation described in the present invention are the forward flotation and reverse flotation commonly understood by those skilled in the art, that is, the forward flotation refers to: discharging useless mineral surfaces with the ore pulp as tailings; the reverse flotation refers to: leaving the required minerals in the flotation cell, and scraping out the unnecessary minerals with the foam.

[0015] As a preferred embodiment of the present invention, the CaSO4·2H2O content of the phosphogypsum is 70-92%, the whiteness is 20-40%, and the SiO2 content is 4-8%.

[0016] For the phosphogypsum with the above-mentioned specific whiteness and CaSO4·2H2O and SiO2 contents, the purification and whitening method of the present invention has good effect, and can effectively remove impurities and whiten the phosphogypsum at the same time.

[0017] As a preferred embodiment of the present invention, the mass fraction of the ore pulp is 20-40%, and the decolorization treatment comprises adding a decolorization collector and a frother into the ore pulp for reverse flotation.

[0018] As a preferred embodiment of the present invention, the decolorizing collector is a trihydroxy polyammonium collector, and its dosage is 0.48-1 kg / t. It should be noted that the dosage of the decolorizing collector kg / t refers to the dosage relative to phosphogypsum, that is, 0.48-1 kg of trihydroxy polyammonium collector is used for 1 t of phosphogypsum, the same below.

[0019] As a preferred embodiment of the present invention, the foaming agent is a carbonate foaming agent, and its dosage is 0.18-0.24 kg / t. The above-mentioned specific polyammonium type containing three hydroxyl groups is used as a collector, and carbonate is used as a foaming agent, and its dosage is controlled. Under their interaction and mutual influence, only one step of treatment is required to effectively remove organic matter, carbon slag, dolomite and other gangue minerals, thereby effectively improving the whiteness and purity of phosphogypsum.

[0020] As a preferred embodiment of the present invention, the trihydroxy polyammonium collector is at least one of 3-hydroxy ammonium hexanoate and 3-hydroxy ammonium dodecanoate.

[0021] As a preferred embodiment of the present invention, the foaming agent is at least one of sodium carbonate and calcium carbonate.

[0022] As a preferred embodiment of the present invention, the collector is at least one of sodium linear alkylbenzene sulfonate and sodium α-olefin sulfonate, and the amount thereof is 0.15 to 0.25 kg / t.

[0023] As a preferred embodiment of the present invention, the pH regulator is a sulfuric acid solution with a volume concentration of 20-40%. When the pH regulator is a sulfuric acid solution with a volume concentration of 20-40%, unreacted phosphorus pentoxide and metal oxides in phosphogypsum can be dissolved, while also avoiding corrosion to equipment.

[0024] As a preferred embodiment of the present invention, the pH adjuster is a sulfuric acid solution with a volume concentration of 30-40%.

[0025] As a preferred embodiment of the present invention, the drying temperature is 100-200° C. The inventors of the present invention have found in a large number of studies that the drying temperature can significantly affect the whiteness of phosphogypsum, and the whiteness of phosphogypsum can be significantly improved by controlling the drying temperature at 100-200° C.

[0026] As a preferred embodiment of the present invention, the drying temperature is 200°C.

[0027] The beneficial effects of the present invention are as follows: (1) the method for purifying and whitening phosphogypsum of the present invention can prepare phosphogypsum with high purity and high whiteness, effectively reduce the storage of phosphogypsum, alleviate environmental pressure, and has broad application prospects. The prepared refined phosphogypsum can replace desulfurized gypsum to prepare building gypsum powder; (2) the present invention decolorizes the phosphogypsum and then performs three positive flotations to effectively remove impurities and decolorize the phosphogypsum, so that organic matter, carbon slag, silicon and other impurities in the phosphogypsum are effectively removed, thereby preparing high-purity phosphogypsum with high whiteness and purity; (3) the present invention adopts a polyammonium type containing three hydroxyl groups as a collector and carbonate as a foaming agent, and controls their dosage. Under their interaction and mutual influence, only one step of treatment is required to effectively remove organic matter, carbon slag, dolomite and other gangue minerals, thereby effectively improving the whiteness and purity of the phosphogypsum. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the present invention, there is no particular limitation on the specific dispersion and stirring treatment methods.

[0030] Example 1

[0031] A method for purifying and whitening phosphogypsum comprises the following steps:

[0032] (1) In a mixing barrel, phosphogypsum (CaSO4·2H2O content of 91.89%, whiteness of 31.03%, SiO2 content of 5.87%) was added with water to prepare a slurry with a mass concentration of 35%, 1 kg / t of 3-hydroxy ammonium dodecanoate and 0.26 kg / t of calcium carbonate were added to the slurry, and reverse flotation was performed to obtain a decolorized slurry;

[0033] (2) adding the decolorized pulp to a roughing flotation tank, adding 0.2 kg / t of sodium dodecylbenzene sulfonate, and adding a sulfuric acid solution with a volume concentration of 35%, adjusting the pH to 2.4, and performing the first positive flotation to obtain a first flotation liquid;

[0034] (3) adding the first flotation liquid to a concentration flotation tank, adding a sulfuric acid solution with a volume concentration of 35%, adjusting the pH to 2.4, and performing a second positive flotation to obtain a second flotation liquid;

[0035] (4) The second flotation liquid is added to another fine flotation tank, and a sulfuric acid solution with a volume concentration of 35% is added to adjust the pH to 2.4, and a third positive flotation is performed, concentrated, filtered, and dried at 100° C. to obtain refined phosphogypsum.

[0036] The obtained refined phosphogypsum has a CaSO4·2H2O content of 96.17%, a yield of 79.99%, a whiteness of 67.12%, and a SiO2 content of 0.57%.

[0037] Example 2

[0038] The difference between Example 2 and Example 1 is that the drying temperature is different, and the other aspects are the same.

[0039] The drying temperature of Example 2 is 200°C, and the CaSO4·2H2O content of the obtained refined phosphogypsum is 96.17%, the yield is 79.99%, the whiteness is 73.71%, and the SiO2 content is 0.57%.

[0040] Example 3

[0041] A method for purifying and whitening phosphogypsum comprises the following steps:

[0042] (1) in a mixing barrel, phosphogypsum (CaSO4·2H2O content of 91.89%, whiteness of 31.03%, SiO2 content of 5.87%) was added with water to prepare a slurry with a mass concentration of 35%, 0.8 kg / t of ammonium 3-hydroxycaproate and 0.24 kg / t of calcium carbonate were added to the slurry, and reverse flotation was performed to obtain a decolorized slurry;

[0043] (2) adding the decolorized pulp to a roughing flotation tank, adding 0.15 kg / t of sodium α-olefin sulfonate, and adding a sulfuric acid solution with a volume concentration of 30%, adjusting the pH to 2.2, and performing the first positive flotation to obtain a first flotation liquid;

[0044] (3) adding the first flotation liquid to a concentration flotation tank, adding a sulfuric acid solution with a volume concentration of 30%, adjusting the pH to 2.2, and performing a second positive flotation to obtain a second flotation liquid;

[0045] (4) The second flotation liquid is added to another fine flotation tank, and a sulfuric acid solution with a volume concentration of 30% is added to adjust the pH to 2.2, and a third positive flotation is performed, concentrated, filtered, and dried at 100° C. to obtain refined phosphogypsum.

[0046] The obtained refined phosphogypsum has a CaSO4·2H2O content of 96.56%, a yield of 78.84%, a whiteness of 65.74%, and a SiO2 content of 0.77%.

[0047] Example 4

[0048] The difference between Example 4 and Example 3 is that the drying temperature is different, and the other aspects are the same.

[0049] The drying temperature of Example 4 is 200°C, and the CaSO4·2H2O content of the obtained refined phosphogypsum is 96.56%, the yield is 78.84%, the whiteness is 76.46%, and the SiO2 content is 0.77%.

[0050] Example 5

[0051] A method for purifying and whitening phosphogypsum comprises the following steps:

[0052] (1) In a mixing barrel, phosphogypsum (CaSO4·2H2O content of 91.89%, whiteness of 31.03%, SiO2 content of 5.87%) was added with water to prepare a slurry with a mass concentration of 35%, 0.6 kg / t of 3-hydroxy ammonium dodecanoate and 0.22 kg / t of sodium carbonate were added to the slurry, and reverse flotation was performed to obtain a decolorized slurry;

[0053] (2) adding the decolorized pulp to a roughing flotation tank, adding 0.1 kg / t of sodium dodecylbenzene sulfonate, and adding a sulfuric acid solution with a volume concentration of 40%, adjusting the pH to 2.5, and performing the first positive flotation to obtain a first flotation liquid;

[0054] (3) adding the first flotation liquid to a concentration flotation tank, adding a sulfuric acid solution with a volume concentration of 40%, adjusting the pH to 2.5, and performing a second positive flotation to obtain a second flotation liquid;

[0055] (4) The second flotation liquid is added to another fine flotation tank, and a sulfuric acid solution with a volume concentration of 40% is added to adjust the pH to 2.5, and a third positive flotation is performed, concentrated, filtered, and dried at 100° C. to obtain refined phosphogypsum.

[0056] The obtained refined phosphogypsum has a CaSO4·2H2O content of 97.71%, a yield of 79.40%, a whiteness of 65.50%, and a SiO2 content of 0.66%.

[0057] Example 6

[0058] The difference between Example 6 and Example 5 is that the drying temperature is different, and the other aspects are the same.

[0059] The drying temperature of Example 6 is 200°C, and the CaSO4·2H2O content of the obtained refined phosphogypsum is 97.71%, the yield is 79.40%, the whiteness is 73.46%, and the SiO2 content is 0.66%.

[0060] Example 7

[0061] A method for purifying and whitening phosphogypsum comprises the following steps:

[0062] (1) in a mixing barrel, phosphogypsum (CaSO4·2H2O content of 91.89%, whiteness of 31.03%, SiO2 content of 5.87%) was added with water to prepare a slurry with a mass concentration of 35%, 0.48 kg / t of 3-hydroxy ammonium dodecanoate and 0.2 kg / t of calcium carbonate were added to the slurry, and reverse flotation was performed to obtain a decolorized slurry;

[0063] (2) adding the decolorized pulp to a roughing flotation tank, adding 0.1 kg / t of sodium dodecylbenzene sulfonate, and adding a sulfuric acid solution with a volume concentration of 35%, adjusting the pH to 2.3, and performing the first positive flotation to obtain a first flotation liquid;

[0064] (3) adding the first flotation liquid to a concentration flotation tank, adding a sulfuric acid solution with a volume concentration of 35%, adjusting the pH to 2.3, and performing a second positive flotation to obtain a second flotation liquid;

[0065] (4) The second flotation liquid is added to another fine flotation tank, and a sulfuric acid solution with a volume concentration of 35% is added to adjust the pH to 2.3, and a third positive flotation is performed, concentrated, filtered, and dried at 100° C. to obtain refined phosphogypsum.

[0066] The obtained refined phosphogypsum has a CaSO4·2H2O content of 97.71%, a yield of 78.93%, a whiteness of 62.42%, and a SiO2 content of 0.82%.

[0067] Example 8

[0068] The difference between Example 8 and Example 7 is that the drying temperature is different, and the other aspects are the same.

[0069] The drying temperature of Example 8 is 200°C, and the CaSO4·2H2O content of the obtained refined phosphogypsum is 97.71%, the yield is 78.93%, the whiteness is 67.99%, and the SiO2 content is 0.82%.

[0070] Comparative Example 1

[0071] The difference between Comparative Example 1 and Example 7 is that Comparative Example 1 adopts one positive flotation, and the other aspects are the same.

[0072] A method for purifying and whitening phosphogypsum comprises the following steps:

[0073] (1) in a mixing barrel, phosphogypsum (CaSO4·2H2O content of 91.89%, whiteness of 31.03%, SiO2 content of 5.87%) was added with water to prepare a slurry with a mass concentration of 35%, 0.48 kg / t of 3-hydroxy ammonium dodecanoate and 0.2 kg / t of calcium carbonate were added to the slurry, and reverse flotation was performed to obtain a decolorized slurry;

[0074] (2) Add the decolorized pulp to a roughing flotation tank, add 0.1 kg / t of sodium dodecylbenzene sulfonate, and add a sulfuric acid solution with a volume concentration of 35%, adjust the pH to 2.3, perform the first positive flotation, concentrate, filter, and dry at 100° C. to obtain refined phosphogypsum.

[0075] The obtained refined phosphogypsum has a CaSO4·2H2O content of 93%, a yield of 83%, a whiteness of 42%, and a SiO2 content of 1.5%.

[0076] Comparative Example 2

[0077] The difference between Comparative Example 2 and Example 7 is that the pH adjusted during the positive flotation process in Comparative Example 2 is different, and the other aspects are the same.

[0078] A method for purifying and whitening phosphogypsum comprises the following steps:

[0079] (1) in a mixing barrel, phosphogypsum (CaSO4·2H2O content of 91.89%, whiteness of 31.03%, SiO2 content of 5.87%) was added with water to prepare a slurry with a mass concentration of 35%, 0.48 kg / t of 3-hydroxy ammonium dodecanoate and 0.2 kg / t of calcium carbonate were added to the slurry, and reverse flotation was performed to obtain a decolorized slurry;

[0080] (2) adding the decolorized pulp to a roughing flotation tank, adding 0.1 kg / t of sodium dodecylbenzene sulfonate, and adding a sulfuric acid solution with a volume concentration of 35%, adjusting the pH to 3.5, and performing the first positive flotation to obtain a first flotation liquid;

[0081] (3) adding the first flotation liquid to a concentration flotation tank, adding a sulfuric acid solution with a volume concentration of 35%, adjusting the pH to 3.5, and performing a second positive flotation to obtain a second flotation liquid;

[0082] (4) The second flotation liquid is added to another fine flotation tank, and a sulfuric acid solution with a volume concentration of 35% is added to adjust the pH to 3.5, and a third positive flotation is performed, concentrated, filtered, and dried at 100° C. to obtain refined phosphogypsum.

[0083] The obtained refined phosphogypsum has a CaSO4·2H2O content of 93%, a yield of 86%, a whiteness of 45%, and a SiO2 content of 3.5%.

[0084] Comparative Example 3

[0085] The difference between Comparative Example 3 and Example 7 is that the decolorizing collector and the foaming agent in Comparative Example 3 are different from those in Example 7, and the others are the same.

[0086] A method for purifying and whitening phosphogypsum comprises the following steps:

[0087] (1) In a stirring barrel, phosphogypsum (CaSO4·2H2O content of 91.89%, whiteness of 31.03%, SiO2 content of 5.87%) was added with water to prepare a slurry with a mass concentration of 35%, 0.48 kg / t of dodecyltrimethylammonium bromide and 0.2 kg / t of pine oil were added to the slurry, and reverse flotation was performed to obtain a decolorized slurry;

[0088] (2) adding the decolorized pulp to a roughing flotation tank, adding 0.1 kg / t of sodium dodecylbenzene sulfonate, and adding a sulfuric acid solution with a volume concentration of 35%, adjusting the pH to 2.3, and performing the first positive flotation to obtain a first flotation liquid;

[0089] (3) adding the first flotation liquid to a concentration flotation tank, adding a sulfuric acid solution with a volume concentration of 35%, adjusting the pH to 2.3, and performing a second positive flotation to obtain a second flotation liquid;

[0090] (4) The second flotation liquid is added to another fine flotation tank, and a sulfuric acid solution with a volume concentration of 35% is added to adjust the pH to 2.3, and a third positive flotation is performed, concentrated, filtered, and dried at 100° C. to obtain refined phosphogypsum.

[0091] The obtained refined phosphogypsum has a CaSO4·2H2O content of 92%, a yield of 88%, a whiteness of 34%, and a SiO2 content of 4.8%.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for purifying and whitening phosphogypsum, characterized in that: The following steps are involved: (1) adding water to phosphogypsum to prepare a slurry, and decolorizing the slurry to obtain a decolorized slurry; (2) adding a collector to the decolorized slurry, adding a pH adjuster, adjusting the pH to 2.4-2.5, performing a first positive flotation, and obtaining a first flotation liquid; (3) adding the pH adjusting agent to the first flotation liquid to adjust the pH to 2.4-2.5, and performing a second positive flotation to obtain a second flotation liquid; (4) adding the pH adjuster to the second flotation liquid to adjust the pH to 2.4-2.5, performing a third positive flotation, concentrating, filtering, and drying to obtain refined phosphogypsum; The decolorization treatment comprises adding a decolorization collector and a frother into the slurry for reverse flotation; the decolorization collector is a trihydroxy polyammonium type collector, and its dosage is 0.48-1 kg / t; the frother is a carbonate frother, and its dosage is 0.18-0.24 kg / t; The CaSO4·2H2O content of the phosphogypsum is 70-92%, the whiteness is 20-40%, and the SiO2 content is 4-8%; The drying temperature is 100-200°C; The trihydroxy polyammonium collector is at least one of 3-hydroxy ammonium hexanoate and 3-hydroxy ammonium dodecanoate.

2. The method for purifying and whitening phosphogypsum according to claim 1, characterized in that: The mass fraction of the slurry is 20-40%.

3. The method for purifying and whitening phosphogypsum according to claim 1, characterized in that: The foaming agent is at least one of sodium carbonate and calcium carbonate.

4. The method for purifying and whitening phosphogypsum according to claim 1, characterized in that: The collector is at least one of linear alkylbenzene sodium sulfonate and α-olefin sodium sulfonate, and the amount used is 0.15-0.25 kg / t.

5. The method for purifying and whitening phosphogypsum according to claim 1, characterized in that: The pH regulator is a sulfuric acid solution with a volume concentration of 20-40%.

6. The method for purifying and whitening phosphogypsum according to claim 1, characterized in that: The pH regulator is a sulfuric acid solution with a volume concentration of 30-40%.

7. The method for purifying and whitening phosphogypsum according to claim 1, characterized in that: The drying temperature is 200°C.