Method for removing organic matters in potassium sulfate waste salt

Abstract

The invention relates to a method for removing organic matters in potassium sulfate waste salt, which comprises the following steps: S1, mixing potassium sulfate waste salt with a potassium persulfate solution to obtain oxidized potassium sulfate waste salt; s2, mixing the oxidized potassium sulfate waste salt with a potassium sulfate saturated solution, stirring and washing; and S3, drying the wet salt obtained after stirring and washing to constant weight to obtain a potassium sulfate product. Compared with the prior art, the method has the advantages that the potassium sulfate in the waste salt can be efficiently recycled, and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of potassium-containing waste salt treatment, and particularly to a method for removing organic matter from potassium sulfate waste salt. Background Art

[0002] In recent years, the sources of potassium-containing waste salt in China are extensive and the total amount is increasing continuously. The "National List of Hazardous Wastes" has listed the waste salt generated in industries such as pesticides and biopharmaceuticals as hazardous wastes. If not properly treated, it will directly cause pollution to natural environments such as surface water, groundwater, and soil. At present, waste salt is mainly treated by methods such as building storage facilities for centralized temporary storage, incineration, and rigid landfill, facing high storage and treatment costs that are difficult for enterprises to bear. At the same time, China has a problem of lack of potassium resources. Therefore, potassium-containing industrial waste salt can be used as an important resource raw material. Recycling potassium-containing waste salt can not only eliminate its environmental pollution but also make full use of salt resources to achieve the resource utilization and circular utilization of salt.

[0003] At present, the main methods for harmless removal of organic matter from waste salt are pyrolysis carbonization method, high-temperature melting method, and oxidation method.

[0004] The pyrolysis carbonization method utilizes the thermal instability of organic matter to decompose and carbonize the organic matter in waste salt under anaerobic or anoxic conditions, decomposing it into volatile gases and carbon slag, so as to achieve the purpose of removing organic impurities in waste salt. Patent CN109882854A discloses a method for high-temperature pyrolysis and harmless treatment of industrial waste salt using suspension incineration technology, which uses a suspension incinerator to replace the commonly used heat pipe pyrolysis furnace for industrial waste salt treatment. This method has the advantages of less flue gas pollution and recyclable carbon. However, due to the need to control the pyrolysis method under anaerobic or anoxic conditions and the operating temperature needs to be lower than the melting point of waste miscellaneous salt, the application range of this method is limited.

[0005] The high-temperature melting treatment method removes the organic matter in industrial waste salt in a molten state at a high temperature of 800 - 1200 °C, and the removal effect of organic matter is better. The high-temperature melting method treats waste salt at a higher reaction temperature than the pyrolysis carbonization method, effectively avoiding the disadvantage of the pyrolysis carbonization method being prone to bonding with refractory materials and improving the purity of waste salt. Patent CN112591767A discloses a method for high-temperature melting and oxidation treatment of chemical industrial waste salt, including melting and enhanced oxidation of molten salt. By means of enhanced mass transfer, the contact between organic matter and oxidizing substances is enhanced, and the chemical industrial waste salt is converted into raw materials used by chlor-alkali enterprises to achieve closed-loop recycling. However, due to the high energy consumption of the high-temperature melting method, it usually requires waste heat recovery and utilization of high-temperature flue gas, increasing equipment investment costs. At the same time, the particles entrained in the flue gas will significantly reduce the waste salt resource utilization rate.

[0006] The oxidation method refers to the use of oxidants to oxidize the hardly degradable organic matter in waste salts, which can quickly remove toxic and harmful organic matter, has good effects on the degradation of most organic pollutants, and has the advantages of rapid reaction and no secondary pollution. However, the application of this method is also subject to certain limitations, and has disadvantages such as high cost and small treatment scale.

[0007] At present, there is no method for removing organic matter from potassium sulfate waste salts with low equipment investment, strong operability and wide application range. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for removing organic matter from potassium sulfate waste salts to achieve the harmless treatment and resource utilization of potassium sulfate waste salts.

[0009] The purpose of the present invention can be achieved through the following technical solutions: A method for removing organic matter from potassium sulfate waste salts, comprising the following steps:

[0010] S1: Mix potassium sulfate waste salts with a potassium persulfate solution to obtain oxidized potassium sulfate waste salts;

[0011] S2: Mix the oxidized potassium sulfate waste salts with a saturated potassium sulfate solution and stir and wash;

[0012] S3: Dry the wet salts obtained after stirring and washing to a constant weight to obtain potassium sulfate products.

[0013] Preferably, the potassium persulfate solution in step S1 is an aqueous potassium persulfate solution, and the concentration of the potassium persulfate solution is 50wt%-90wt%.

[0014] Preferably, the addition amount of the potassium persulfate solution in step S1 is 0.5wt%-5wt% of the treatment amount of potassium sulfate waste salts.

[0015] Preferably, the mixing time of the potassium sulfate waste salts and the potassium persulfate solution in step S1 is 0.3-1h.

[0016] Preferably, the mixing temperature of the potassium sulfate waste salts and the potassium persulfate solution in step S1 is normal temperature.

[0017] Preferably, in step S2, the mixture obtained by mixing the potassium sulfate waste salts and the potassium persulfate solution in step S1 is mixed with a saturated potassium sulfate solution for stirring and washing.

[0018] Preferably, the temperature of the saturated potassium sulfate solution in step S2 is 5-40°C.

[0019] Preferably, the mixing temperature in step S2 is 5-40°C.

[0020] Preferably, the stirring and washing time in step S2 is 0.5h-5h.

[0021] Preferably, the pH value of the potassium sulfate saturated solution in step S2 is 1-6, and the pH value of the solution is adjusted by sulfuric acid and / or potassium hydroxide.

[0022] Preferably, the potassium sulfate saturated solution in step S2 is an aqueous solution of potassium sulfate saturated.

[0023] Preferably, the drying temperature of the wet salt in step S3 is 80°C - 150°C.

[0024] Preferably, after stirring and washing in step S2, the wet salt and the washing mother liquor are obtained by centrifugal separation. The wet salt is repeatedly washed with the potassium sulfate saturated solution several times to obtain the wet salt described in step S3.

[0025] More preferably, the rotation speed of the centrifugal separation is 3000 r / min - 8000 r / min, and the separation time is 5 min - 10 min.

[0026] More preferably, a part of the washing mother liquor is recycled as the potassium sulfate saturated solution, and the remaining part is evaporated and concentrated, cooled and crystallized, and the solid phase produced by centrifugal separation is re-entered as the potassium sulfate waste salt into step S1.

[0027] Preferably, the potassium sulfate waste salt contains organic impurities such as acetonitrile, acetic acid, dichloroethane, ethylene glycol, and isopropanol.

[0028] Since dichloroethane is insoluble in water, if the ordinary cold washing process is directly adopted, the impurities of the waste salt cannot be effectively removed. The present invention proposes to add the oxidant potassium persulfate during the cold washing process, so that dichloroethane is oxidized into water-soluble organic matters such as carboxylic acids and can be removed by cold washing.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention provides a method for treating potassium sulfate waste salt, which can efficiently remove harmful organic matters in the potassium sulfate waste salt by the low-temperature oxidation washing method, realizing the harmless treatment and resource utilization of the waste salt;

[0031] 2. The present invention provides a method for the harmless treatment and resource utilization of potassium sulfate waste salt. The potassium sulfate product treated by this method has a wide application prospect;

[0032] 3. The present invention is carried out under low-temperature conditions, far lower than the melting point of the waste salt, and no melting and caking phenomenon will occur, and the obtained potassium sulfate product has good quality;

[0033] 4. The present invention can efficiently recover potassium sulfate in the waste salt, and the addition of potassium persulfate during the treatment process can also increase the content of potassium sulfate, realizing the resource utilization of the product, which meets the national environmental protection requirements;

[0034] 5. The process of the present invention is simple and effective, does not involve high-temperature and high-pressure equipment, does not generate acidic harmful gases, and can achieve clean discharge of the three wastes;

[0035] 6. The present invention adopts the technology of oxidation first and then cold washing, which solves the problem that the cold washing process alone cannot remove the water-insoluble organic matter;

[0036] 7. Since the present invention adopts the method of low-temperature oxidation plus cold washing, the energy consumption and equipment requirements are low. It not only saves the equipment investment cost, but also has strong operability and high safety, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a process flow diagram for removing organic matter from potassium sulfate waste salt of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0039] A method for removing organic matter from potassium sulfate waste salt, as Figure 1 shown, includes the following steps:

[0040] S1: At a certain temperature, according to the solubility of potassium sulfate at the corresponding temperature, prepare a saturated potassium sulfate solution;

[0041] S2: Adjust the pH value of the solution with sulfuric acid and potassium hydroxide, and make a waste salt washing solution after mixing evenly;

[0042] S3: At room temperature, add a certain amount of potassium persulfate solution to the potassium sulfate waste salt to oxidize the dichloroethane in the waste salt;

[0043] S4: At a certain temperature, mix the oxidized potassium sulfate waste salt with the washing solution prepared in S2 and stir for washing;

[0044] S5: After stirring and washing, centrifuge to separate the washed wet salt and the washing mother liquor. The washed wet salt is repeatedly washed with the washing solution prepared in S2 several times and enters S6; the washing mother liquor enters S7;

[0045] S6: The wet salt after washing in S5 is dried to constant weight at a certain temperature to obtain potassium sulfate product;

[0046] S7: A part of the washing mother liquor enters S2 and is used as the washing solution for recycling, and the remaining part enters S8;

[0047] S8: The remaining washing mother liquor is evaporated and concentrated, cooled and crystallized, and the solid phase generated by centrifugal separation re-enters S3, and the liquid generated is discharged after treatment.

[0048] As a preferred technical solution, the temperature in step S1 is 5°C - 40°C.

[0049] As a preferred technical solution, the pH value of the washing liquid in step S2 is 1 - 6.

[0050] As a preferred technical solution, the addition amount of the potassium persulfate solution in step S3 is 0.5% - 5% of the potassium sulfate waste salt treatment amount, and the concentration of the potassium persulfate solution is 50% - 90%.

[0051] As a preferred technical solution, the time of the oxidation reaction in step S3 is 0.3 - 1 h.

[0052] As a preferred technical solution, in step S4, the stirring and washing time of the oxidized potassium sulfate waste salt and the washing liquid prepared in S2 is 0.5 h - 5 h.

[0053] As a preferred technical solution, the temperature of the stirring and washing in step S4 is 5°C - 40°C.

[0054] As a preferred technical solution, the centrifugal separation speed in step S5 is 3000 r / min - 8000 r / min, and the separation time is 5 min - 10 min.

[0055] As a preferred technical solution, the repeated washing times of the potassium sulfate waste salt in step S5 is 0 - 2 times.

[0056] As a preferred technical solution, the drying temperature of the wet salt in step S6 is 80°C - 150°C.

[0057] The following is a detailed description in conjunction with specific embodiments.

[0058] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0059] The potassium sulfate waste salt used in the following examples is generated during the production of pesticide intermediates, and the waste salt mainly contains five organic matter impurities: acetonitrile, acetic acid, dichloroethane, ethylene glycol and isopropanol.

[0060] Example 1

[0061] S1: At 5°C, according to the solubility of potassium sulfate, prepare a saturated potassium sulfate solution;

[0062] S2: Use sulfuric acid and potassium hydroxide to adjust the pH value of the solution prepared in S1 to 1 to make a waste salt washing liquid;

[0063] S3: At room temperature, add a 0.5% potassium persulfate solution with a concentration of 90% to the potassium sulfate waste salt, and the oxidation time is 0.3 h;

[0064] S4: At 5 °C, mix the potassium sulfate waste salt oxidized in S3 with the washing solution prepared in S2, stir and wash for 0.5 h;

[0065] S5: After stirring and washing, perform centrifugal separation at a rotational speed of 3000 r / min for 5 min to separate the washed waste salt and the washing mother liquor. The washed waste salt enters S6, and the washing mother liquor enters S7;

[0066] S6: Dry the waste salt washed in S5 at 80 °C to obtain potassium sulfate products;

[0067] S7: Part of the washing mother liquor enters S2 and is recycled as the washing solution, and the remaining part enters S8;

[0068] S8: The solid phase generated from the remaining washing mother liquor through evaporation concentration, cooling crystallization, and centrifugal separation re-enters S3, and the generated liquid is discharged after treatment.

[0069] Example 2

[0070] S1: At 20 °C, prepare a saturated potassium sulfate solution according to the solubility of potassium sulfate;

[0071] S2: Adjust the pH value of the solution prepared in S1 to 2.5 with sulfuric acid and potassium hydroxide to prepare a waste salt washing solution;

[0072] S3: At room temperature, add a 0.5% potassium persulfate solution with a concentration of 75% to the potassium sulfate waste salt, and the oxidation time is 0.7 h;

[0073] S4: At 20 °C, mix the oxidized potassium sulfate waste salt with the washing solution prepared in S2, stir and wash for 1 h;

[0074] S5: After stirring and washing, perform centrifugal separation at a rotational speed of 5000 r / min for 7.5 min to separate the washed waste salt and the washing mother liquor. The washed waste salt is washed again and then enters S6, and the washing mother liquor enters S7;

[0075] S6: Dry the waste salt washed in S5 at 105 °C to obtain potassium sulfate products;

[0076] S7: Part of the washing mother liquor enters S8 and is recycled as the washing solution, and the remaining part enters S7;

[0077] S8: The solid phase generated from the remaining washing mother liquor through evaporation concentration, cooling crystallization, and centrifugal separation re-enters S3, and the generated liquid is discharged after treatment.

[0078] Example 3

[0079] S1: At 40 °C, prepare a saturated potassium sulfate solution according to the solubility of potassium sulfate;

[0080] S2: Adjust the pH value of the solution prepared in S1 to 6 with sulfuric acid and potassium hydroxide to make a waste salt washing solution;

[0081] S3: At room temperature, add a 0.5% potassium persulfate solution to the potassium sulfate waste salt. The concentration of the potassium persulfate solution is 50%, and the oxidation time is 1 h;

[0082] S4: At 40 °C, mix the potassium sulfate waste salt with the washing solution prepared in S2, stir and wash for 5 h;

[0083] S5: After stirring and washing, perform centrifugal separation at a rotational speed of 8000 r / min for 10 min to separate the washed waste salt and the washing mother liquor. The washed waste salt is washed twice and then enters S6, and the washing mother liquor enters S7;

[0084] S6: Dry the waste salt washed in S5 at 150 °C to obtain a potassium sulfate product;

[0085] S7: Part of the washing mother liquor enters S2 and is recycled as the washing solution, and the remaining part enters S8;

[0086] S8: The solid phase generated from the evaporation, concentration, cooling crystallization, and centrifugal separation of the remaining washing mother liquor re-enters S3, and the generated liquid is discharged after treatment.

[0087] Example 4

[0088] S1: At 5 °C, prepare a saturated potassium sulfate solution according to the solubility of potassium sulfate;

[0089] S2: Adjust the pH value of the solution prepared in S1 to 1 with sulfuric acid and potassium hydroxide to make a waste salt washing solution;

[0090] S3: At room temperature, add a 1% potassium persulfate solution to the potassium sulfate waste salt. The concentration of the potassium persulfate solution is 90%, and the oxidation time is 0.3 h;

[0091] S4: At 5 °C, mix the potassium sulfate waste salt after oxidation in S3 with the washing solution prepared in S2, stir and wash for 0.5 h;

[0092] S5: After stirring and washing, perform centrifugal separation at a rotational speed of 3000 r / min for 5 min to separate the washed waste salt and the washing mother liquor. The washed waste salt enters S6, and the washing mother liquor enters S7;

[0093] S6: Dry the waste salt washed in S5 at 80 °C to obtain a potassium sulfate product;

[0094] S7: A part of the washing mother liquor enters S2 and is recycled as the washing liquid, and the remaining part enters S8;

[0095] S8: The solid phase generated from the remaining washing mother liquor through evaporation concentration, cooling crystallization, and centrifugal separation re-enters S3, and the generated liquid is discharged after treatment.

[0096] Example 5

[0097] S1: At 20 °C, according to the solubility of potassium sulfate, prepare a saturated potassium sulfate solution;

[0098] S2: Adjust the pH value of the solution prepared in S1 to 2.5 with sulfuric acid and potassium hydroxide to make a waste salt washing liquid;

[0099] S3: At room temperature, add a 1% potassium persulfate solution to the potassium sulfate waste salt, the concentration of the potassium persulfate solution is 75%, and the oxidation time is 0.7 h;

[0100] S4: At 20 °C, mix the oxidized potassium sulfate waste salt with the washing liquid prepared in S2, stir and wash for 1 h;

[0101] S5: After stirring and washing, perform centrifugal separation at a rotational speed of 5000 r / min and a centrifugation time of 7.5 min to separate the washed waste salt and the washing mother liquor. The washed waste salt is washed again and enters S6, and the washing mother liquor enters S7;

[0102] S6: The waste salt after washing in S5 is dried at 105 °C to obtain potassium sulfate products;

[0103] S7: A part of the washing mother liquor enters S2 and is recycled as the washing liquid, and the remaining part enters S8;

[0104] S8: The solid phase generated from the remaining washing mother liquor through evaporation concentration, cooling crystallization, and centrifugal separation re-enters S3, and the generated liquid is discharged after treatment.

[0105] Example 6

[0106] S1: At 40 °C, according to the solubility of potassium sulfate, prepare a saturated potassium sulfate solution;

[0107] S2: Adjust the pH value of the solution prepared in S1 to 6 with sulfuric acid and potassium hydroxide to make a waste salt washing liquid;

[0108] S3: At room temperature, add a 1% potassium persulfate solution to the potassium sulfate waste salt, the concentration of the potassium persulfate solution is 50%, and the oxidation time is 1 h;

[0109] S4: At 40 °C, mix the potassium sulfate waste salt with the washing liquid prepared in S2, stir and wash for 5 h;

[0110] S5: After stirring and washing, perform centrifugal separation at a rotational speed of 8000 r / min for 10 min to separate the washed waste salt and the washing mother liquor. The washed waste salt is repeatedly washed twice and enters S6, while the washing mother liquor enters S7;

[0111] S6: The waste salt after washing in S5 is dried at 150 °C to obtain potassium sulfate product;

[0112] S7: A part of the washing mother liquor enters S2 and is recycled as the washing liquid, and the remaining part enters S8;

[0113] S8: The solid phase generated from the remaining washing mother liquor through evaporation concentration, cooling crystallization, and centrifugal separation re-enters S3, and the generated liquid is discharged after treatment.

[0114] Example 7

[0115] S1: At 5 °C, prepare a saturated potassium sulfate solution according to the solubility of potassium sulfate;

[0116] S2: Adjust the pH value of the solution prepared in S1 to 1 with sulfuric acid and potassium hydroxide to make a waste salt washing liquid;

[0117] S3: At room temperature, add a 3% potassium persulfate solution with a concentration of 90% to the potassium sulfate waste salt, and the oxidation time is 0.3 h;

[0118] S4: At 5 °C, mix the potassium sulfate waste salt after oxidation in S3 with the washing liquid prepared in S2, and stir and wash for 0.5 h;

[0119] S5: After stirring and washing, perform centrifugal separation at a rotational speed of 3000 r / min for 5 min to separate the washed waste salt and the washing mother liquor. The washed waste salt enters S6, and the washing mother liquor enters S7;

[0120] S6: The waste salt after washing in S5 is dried at 80 °C to obtain potassium sulfate product;

[0121] S7: A part of the washing mother liquor enters S2 and is recycled as the washing liquid, and the remaining part enters S8;

[0122] S8: The solid phase generated from the remaining washing mother liquor through evaporation concentration, cooling crystallization, and centrifugal separation re-enters S3, and the generated liquid is discharged after treatment.

[0123] Example 8

[0124] S1: At 20 °C, prepare a saturated potassium sulfate solution according to the solubility of potassium sulfate;

[0125] S2: Adjust the pH value of the solution prepared in S1 to 2.5 with sulfuric acid and potassium hydroxide to make a waste salt washing liquid;

[0126] S3: At room temperature, add a 3% potassium persulfate solution to the potassium sulfate waste salt. The concentration of the potassium persulfate solution is 75%, and the oxidation time is 0.7 h.

[0127] S4: At 20 °C, mix the oxidized potassium sulfate waste salt with the washing liquid prepared in S2, stir and wash for 1 h.

[0128] S5: After stirring and washing, perform centrifugal separation at a rotational speed of 5000 r / min for 7.5 min to separate the washed waste salt and the washing mother liquor. The washed waste salt is washed once again and enters S6, while the washing mother liquor enters S7.

[0129] S6: Dry the waste salt washed in S5 at 105 °C to obtain potassium sulfate products.

[0130] S7: Part of the washing mother liquor enters S2 and is recycled as the washing liquid, while the remaining part enters S8.

[0131] S8: The solid phase generated from the evaporation concentration, cooling crystallization, and centrifugal separation of the remaining washing mother liquor re-enters S3, and the generated liquid is discharged after treatment.

[0132] Example 9

[0133] S1: At 40 °C, prepare a saturated potassium sulfate solution according to the solubility of potassium sulfate.

[0134] S2: Adjust the pH value of the solution prepared in S1 to 6 with sulfuric acid and potassium hydroxide to prepare a waste salt washing liquid.

[0135] S3: At room temperature, add a 3% potassium persulfate solution to the potassium sulfate waste salt. The concentration of the potassium persulfate solution is 50%, and the oxidation time is 1 h.

[0136] S4: At 40 °C, mix the potassium sulfate waste salt with the washing liquid prepared in S2, stir and wash for 5 h.

[0137] S5: After stirring and washing, perform centrifugal separation at a rotational speed of 8000 r / min for 10 min to separate the washed waste salt and the washing mother liquor. The washed waste salt is washed twice and enters S6, while the washing mother liquor enters S7.

[0138] S6: Dry the waste salt washed in S5 at 150 °C to obtain potassium sulfate products.

[0139] S7: Part of the washing mother liquor enters S2 and is recycled as the washing liquid, while the remaining part enters S8.

[0140] S8: The solid phase generated from the evaporation concentration, cooling crystallization, and centrifugal separation of the remaining washing mother liquor re-enters S3, and the generated liquid is discharged after treatment.

[0141] Example 10

[0142] S1: At 5°C, prepare a saturated potassium sulfate solution according to the solubility of potassium sulfate;

[0143] S2: Adjust the pH value of the solution prepared in S1 to 1 with sulfuric acid and potassium hydroxide to make a waste salt washing solution;

[0144] S3: At room temperature, add a 5% potassium persulfate solution to the potassium sulfate waste salt. The concentration of the potassium persulfate solution is 90%, and the oxidation time is 0.3 h;

[0145] S4: At 5°C, mix the potassium sulfate waste salt after oxidation in S3 with the washing solution prepared in S2, stir and wash for 0.5 h;

[0146] S5: After stirring and washing, perform centrifugal separation at a rotational speed of 3000 r / min for 5 min to separate the washed waste salt and the washing mother liquor. The washed waste salt enters S6, and the washing mother liquor enters S7;

[0147] S6: Dry the waste salt washed in S5 at 80°C to obtain a potassium sulfate product;

[0148] S7: Part of the washing mother liquor enters S2 and is recycled as the washing solution, and the remaining part enters S8;

[0149] S8: The remaining washing mother liquor is evaporated and concentrated, cooled and crystallized, and the solid phase produced by centrifugal separation re-enters S3, and the liquid produced is discharged after treatment.

[0150] Example 11

[0151] S1: At 20°C, prepare a saturated potassium sulfate solution according to the solubility of potassium sulfate;

[0152] S2: Adjust the pH value of the solution prepared in S1 to 2.5 with sulfuric acid and potassium hydroxide to make a waste salt washing solution;

[0153] S3: At room temperature, add a 5% potassium persulfate solution to the potassium sulfate waste salt. The concentration of the potassium persulfate solution is 75%, and the oxidation time is 0.7 h;

[0154] S4: At 20°C, mix the oxidized potassium sulfate waste salt with the washing solution prepared in S2, stir and wash for 1 h;

[0155] S5: After stirring and washing, perform centrifugal separation at a rotational speed of 5000 r / min for 7.5 min to separate the washed waste salt and the washing mother liquor. The washed waste salt is washed once again and then enters S6, and the washing mother liquor enters S7;

[0156] S6: Dry the waste salt washed in S5 at 105°C to obtain a potassium sulfate product;

[0157] S7: Part of the washing mother liquor enters S2 and is recycled as the washing liquid, and the remaining part enters S8;

[0158] S8: The solid phase generated from the remaining washing mother liquor through evaporation concentration, cooling crystallization, and centrifugal separation re-enters S3, and the generated liquid is discharged after treatment.

[0159] Example 12

[0160] S1: At 40 °C, according to the solubility of potassium sulfate, prepare a saturated potassium sulfate solution;

[0161] S2: Adjust the pH value of the solution prepared in S1 to 6 with sulfuric acid and potassium hydroxide to make a waste salt washing liquid;

[0162] S3: At room temperature, add a 5% potassium persulfate solution to the potassium sulfate waste salt. The concentration of the potassium persulfate solution is 50%, and the oxidation time is 1 h;

[0163] S4: At 40 °C, mix the potassium sulfate waste salt with the washing liquid prepared in S2, stir and wash for 5 h;

[0164] S5: After stirring and washing, perform centrifugal separation at a rotation speed of 8000 r / min for 10 min to separate the washed waste salt and the washing mother liquor. The washed waste salt is repeatedly washed twice and enters S6, and the washing mother liquor enters S7;

[0165] S6: The waste salt after washing in S5 is dried at 150 °C to obtain potassium sulfate products;

[0166] S7: Part of the washing mother liquor enters S2 and is recycled as the washing liquid, and the remaining part enters S8;

[0167] S8: The solid phase generated from the remaining washing mother liquor through evaporation concentration, cooling crystallization, and centrifugal separation re-enters S3, and the generated liquid is discharged after treatment.

[0168] Application Example

[0169] Compare the potassium sulfate content and the residual amount of organic matter in the potassium sulfate products after treatment in Comparative Example 1, Example 4, Example 7, Example 10, and Example 13. The specific results are shown in the following table.

[0170] Table 1: Potassium Sulfate and Organic Matter Contents in Potassium Sulfate Waste Salt after Treatment in Different Examples

[0171]

[0172] Note: The detection limits of acetic acid, acetonitrile, isopropanol, dichloroethane, and ethylene glycol in the potassium sulfate waste salt are all less than 10 ppb.

[0173] Comparative Example 1

[0174] In Comparative Example 1, the difference from Example 1 is as follows:

[0175] Potassium persulfate was not added in step S3.

[0176] For the potassium sulfate content and the residual amount of organic matter in the potassium sulfate product after the treatment of Comparative Example 1, the specific results are shown in the following table.

[0177] Table 2: Potassium sulfate and organic matter contents in the potassium sulfate waste salt after the treatment of Comparative Example 1

[0178]

[0179] It can be seen that dichloroethane in the potassium sulfate waste salt cannot be effectively removed in Comparative Example 1, and the potassium sulfate content decreases.

[0180] Comparative Example 2

[0181] In Comparative Example 2, the difference from Example 1 is as follows:

[0182] Potassium dichromate was added in step S3.

[0183] For the potassium sulfate content and the residual amount of organic matter in the potassium sulfate product after the treatment of Comparative Example 2, the specific results are shown in the following table.

[0184] Table 3: Potassium sulfate and organic matter contents in the potassium sulfate waste salt after the treatment of Comparative Example 2

[0185]

[0186] It can be seen that a new impurity, potassium dichromate, is introduced in Comparative Example 2.

[0187] Comparative Example 3

[0188] In Comparative Example 3, the difference from Example 1 is as follows:

[0189] 0.1% potassium persulfate was added in step S3 (i.e., a 0.1% potassium persulfate solution was added to the potassium sulfate waste salt).

[0190] For the potassium sulfate content and the residual amount of organic matter in the potassium sulfate product after the treatment of Comparative Example 3, the specific results are shown in the following table.

[0191] Table 4: Potassium sulfate and organic matter contents in the potassium sulfate waste salt after the treatment of Comparative Example 3

[0192]

[0193]

[0194] It can be seen that dichloroethane in the potassium sulfate waste salt cannot be completely and effectively removed in Comparative Example 3.

[0195] Comparative Example 4

[0196] In this Comparative Example 4, the difference from Example 1 is that:

[0197] In step S3, 10% potassium persulfate is added (that is, 10% potassium persulfate solution is added to the potassium sulfate waste salt).

[0198] For the potassium sulfate content and the residual amount of organic substances in the potassium sulfate product after the treatment of Comparative Example 4, the specific results are shown in the following table.

[0199] Table 4: Potassium sulfate and organic matter contents in the potassium sulfate waste salt after the treatment of Comparative Example 4

[0200]

[0201] It can be seen that a small amount of potassium persulfate impurities are introduced in Comparative Example 4.

[0202] The present invention discloses a method for treating potassium sulfate waste salt by low-temperature oxidation and cold washing, which removes organic substances in the potassium sulfate waste salt. The treated potassium sulfate can be used and sold as a product, realizing the reduction, harmlessness and resource utilization of the waste salt.

[0203] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A method for removing organic matter from potassium sulfate waste salt, characterized in that: The following steps are involved: S1: mixing potassium sulfate waste salt with potassium persulfate solution to obtain oxidized potassium sulfate waste salt; S2: mixing the oxidized potassium sulfate waste salt with a saturated potassium sulfate solution, stirring and washing; S3: Dry the wet salt obtained after stirring and washing to a constant weight to obtain a potassium sulfate product.

2. The method for removing organic matter from potassium sulfate waste salt according to claim 1, characterized in that: The potassium persulfate solution in step S1 is a potassium persulfate aqueous solution, and the concentration of the potassium persulfate solution is 50wt%-90wt%.

3. The method for removing organic matter from potassium sulfate waste salt according to claim 1, characterized in that: The amount of potassium persulfate solution added in step S1 is 0.5wt%-5wt% of the amount of potassium sulfate waste salt treated.

4. The method for removing organic matter from potassium sulfate waste salt according to claim 1, characterized in that: In step S1, the mixing time of the potassium sulfate waste salt and the potassium persulfate solution is 0.3-1h, and the mixing temperature is room temperature.

5. The method for removing organic matter from potassium sulfate waste salt according to claim 1, characterized in that: The temperature of the saturated potassium sulfate solution in step S2 is 5-40°C, and the mixing temperature in step S2 is 5-40°C.

6. The method for removing organic matter from potassium sulfate waste salt according to claim 1, characterized in that: The pH value of the saturated potassium sulfate solution in step S2 is 1-6, and the pH value of the solution is adjusted by sulfuric acid and / or potassium hydroxide.

7. The method for removing organic matter from potassium sulfate waste salt according to claim 1, characterized in that: The wet salt drying temperature in step S3 is 80°C-150°C.

8. The method for removing organic matter from potassium sulfate waste salt according to claim 1, characterized in that: After stirring and washing in step S2, the wet salt and the washing mother liquor are obtained by centrifugation, and the wet salt is repeatedly washed several times with a saturated potassium sulfate solution to obtain the wet salt described in step S3.

9. The method for removing organic matter from potassium sulfate waste salt according to claim 8, characterized in that: A part of the washing mother liquor is recycled as a saturated potassium sulfate solution, and the remaining part is evaporated, concentrated, cooled, crystallized, and centrifuged to produce a solid phase that enters step S1 as potassium sulfate waste salt.

10. The method for removing organic matter from potassium sulfate waste salt according to claim 1, characterized in that: The potassium sulfate waste salt contains acetonitrile, acetic acid, ethylene dichloride, ethylene glycol, and isopropanol organic impurities.

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