A method for integrated purification and cascade resource utilization of industrial waste salt

Abstract

The present invention discloses an integrated purification and cascade resource utilization method for industrial waste salt, and relates to the technical field of waste salt resource utilization. The specific preparation method comprises: first, preparing sodium sulfate waste salt into a saturated solution, and then performing low-temperature recrystallization separation to obtain sodium sulfate and mother liquor wastewater, and then adding an impregnating detergent to the sodium sulfate for washing and separation to obtain purified salt and washing wastewater; mixing the mother liquor wastewater and the washing wastewater, adding modified activated carbon for purification, and performing rotary evaporation to obtain waste salt, and the waste salt is mixed with a phosphorus source for reaction, and then subjected to quenching crystallization and crushing to obtain sodium hexametaphosphate. The method of the present invention can prepare purified salt and high-quality sodium hexametaphosphate, and the purified salt can be further used for dyeing and finishing auxiliaries or bipolar membrane electrolysis systems to produce acid and alkali, and then recycled for front-end production, and the sodium hexametaphosphate can be used as a washing auxiliaries, water softeners, detergents, etc. The high-value conversion of low-value waste salt is achieved, and there are good industrial application prospects, economic benefits and environmental benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of waste salt resource utilization, and in particular to a method for integrated purification and cascade resource utilization of industrial waste salt. Background Art

[0002] Industrial waste salt primarily comes from near-zero wastewater discharge terminals, primarily in agriculture, printing and dyeing, coal chemical industry, and fine chemical industries. Its primary components are sodium chloride and sodium sulfate, with annual production currently exceeding 20 million tons. Most waste salt contains persistent organic matter and has been listed on the National List of Hazardous Wastes since 2016. Furthermore, waste salt treatment is difficult and costly. Companies often resort to temporary storage or mixed recycling, which poses serious environmental risks and results in a waste of resources.

[0003] At present, the commonly used treatment methods for waste salt are salt washing, adsorption, oxidation, heat treatment, etc. The effective combination of waste salt treatment processes has not yet been fully reflected, and there are few cases of cascade resource utilization of waste salt. In particular, heat treatment can efficiently remove organic matter, but the reuse value of purified salt may be lower than the treatment cost. It is necessary to make full use of the scenario of heat treatment of waste salt, and by mixing it with certain substances, the waste salt can be removed from organic matter while being simultaneously converted into higher-value substances, so as to achieve the purpose of waste salt resource utilization and high-value conversion. Overall, it is necessary to develop an efficient integrated purification and cascade resource method to achieve the harmlessness of industrial waste salt, cascade resource utilization and high-value conversion of low-value waste salt. Summary of the Invention

[0004] The purpose of the present invention is to provide an integrated purification and cascade resource utilization method for industrial waste salt, so as to solve the problems of imperfect existing waste salt treatment processes and the lack of effective cascade resource utilization.

[0005] In order to solve the above technical problems, the present invention specifically provides the following technical solutions:

[0006] The present invention discloses a method for integrated purification and cascade resource utilization of industrial waste salt, comprising:

[0007] S1: First, sodium sulfate waste salt is added to water to form a saturated solution, and then low-temperature recrystallization is separated to obtain sodium sulfate and mother liquor wastewater. Then, a wetting detergent is added to the sodium sulfate for washing. After washing, purified salt and washing wastewater are separated;

[0008] S2: The mother liquor wastewater and washing waste liquid obtained in S1 are mixed to obtain a mixed liquid, modified activated carbon is added to the mixed liquid for purification, and waste salt is obtained by rotary evaporation. The waste salt is mixed with a phosphorus source for reaction, and then quenched, crystallized, and crushed to obtain sodium hexametaphosphate; the modified activated carbon is prepared from bamboo powder and a polymer, and the polymer is prepared from acrylamide, methacryloyloxyethyltrimethylammonium chloride, dimethylallylamine, and β-bromophenylethane. Purifying the mixed liquid with modified activated carbon can effectively remove organic pollutants and other toxic and harmful substances and impurities in the mixed liquid, thereby obtaining relatively pure waste salt, and further preparing sodium hexametaphosphate with low TOC content and high quality.

[0009] Preferably, the sodium sulfate waste salt in S1 is sodium sulfate waste salt produced by a printing and dyeing production process or a 1,4-butanediol production process.

[0010] Preferably, the low-temperature recrystallization in S1 includes direct low-temperature cooling crystallization and two-phase aqueous solvent crystallization, and the two-phase aqueous solvent is at least two of methanol, acetone, ethanol and saturated brine.

[0011] Preferably, the wetting detergent in S1 is at least one of water, saturated salt water, methanol, acetone and ethanol, and the mass ratio of the wetting detergent to the amount of sodium sulfate used is 1:0.375-1.

[0012] Preferably, the ratio of modified activated carbon to mixed liquid in S2 is 1 g: 50-250 ml.

[0013] Preferably, the phosphorus source in S2 is at least one of phosphoric acid and ammonium dihydrogen phosphate, and the mass ratio of the waste salt to the phosphorus source is 1:1.2-2.1.

[0014] Preferably, the temperature for preparing the saturated solution in S1 is 65-75°C, and the temperature for recrystallization and washing is 15-25°C.

[0015] Preferably, the reaction temperature of the mixed reaction of the waste salt and the phosphorus source in S2 is 500-650° C., and the reaction time is 0.8-2 h.

[0016] The invention also discloses use of the sodium hexametaphosphate prepared by the method in preparing a water treatment agent.

[0017] The present invention discloses a method for integrated purification and cascade resource utilization of industrial waste salt, comprising:

[0018] S1: First, sodium sulfate waste salt is added to water at 65-75°C to form a saturated solution, then the temperature is lowered to 15-25°C, recrystallized and separated to obtain sodium sulfate and mother liquor wastewater, then a wetting detergent is added to the sodium sulfate for washing, and after washing, purified salt and washing wastewater are separated;

[0019] S2: The mother liquor wastewater and washing waste liquid obtained in S1 are mixed to obtain a mixed liquid, modified activated carbon is added to the mixed liquid and shaken for 1.5-3 hours, and then the purified liquid is separated and subjected to rotary evaporation to obtain waste salt, the waste salt is mixed with a phosphorus source, reacted at 500-650°C for 0.8-2 hours, and then quenched, crystallized and crushed to obtain sodium hexametaphosphate.

[0020] Preferably, the sodium sulfate waste salt in S1 is sodium sulfate waste salt produced by a printing and dyeing production process or a 1,4-butanediol production process.

[0021] Preferably, the recrystallization in S1 includes direct low-temperature cooling crystallization and two-phase aqueous solvent crystallization, and the two-phase aqueous solvent is at least two of methanol, acetone, ethanol and saturated brine.

[0022] Preferably, the wetting detergent in S1 is at least one of water, saturated salt water, methanol, acetone and ethanol, and the mass ratio of the wetting detergent to the amount of sodium sulfate used is 1:0.375-1.

[0023] Preferably, the ratio of modified activated carbon to mixed liquid in S2 is 1 g: 50-250 ml.

[0024] Preferably, the phosphorus source in S2 is at least one of phosphoric acid and ammonium dihydrogen phosphate.

[0025] Preferably, the mass ratio of the waste salt to the phosphorus source in S2 is 1:1.2-2.1.

[0026] The present invention discloses a method for preparing a polymer, specifically comprising:

[0027] Dimethylallylamine and β-bromophenylethane are added to acetone and reacted at 55-70°C for 20-40 hours. After completion of the reaction, the intermediate is obtained by rotary evaporation, recrystallization, and drying. Acrylamide and methacryloyloxyethyltrimethylammonium chloride are added to water, and the pH is adjusted to 6.5-7.5. Then, the intermediate, azobisisobutylamidine hydrochloride, and ethylenediaminetetraacetic acid tetrasodium salt are added and reacted under nitrogen for 4-8 hours. After completion of the reaction, the polymer is washed and dried.

[0028] Preferably, the mass ratio of dimethylallylamine to β-bromophenylethane is 1:3-4.

[0029] Preferably, the usage ratio of dimethylallylamine to acetone is 1 g:12-22 ml.

[0030] Preferably, the solvent used for recrystallization is a mixed solvent consisting of acetone and diethyl ether, and the volume ratio of acetone to diethyl ether is 1:2.5-4.

[0031] Preferably, the mass ratio of methacryloyloxyethyltrimethylammonium chloride to acrylamide is 1:0.35-0.5.

[0032] Preferably, the mass ratio of acrylamide to water is 1 g:7.5-9 ml.

[0033] Preferably, the mass ratio of methacryloyloxyethyltrimethylammonium chloride to the intermediate is 1:0.003-0.005.

[0034] Preferably, the mass ratio of the intermediate to azobisisobutylamidine hydrochloride is 1:0.001-0.002.

[0035] Preferably, the mass ratio of the intermediate to the tetrasodium salt of ethylenediaminetetraacetic acid is 1:0.0001-0.0003.

[0036] The present invention discloses a method for preparing modified activated carbon, which is specifically:

[0037] A polymer solution is prepared by mixing the polymer with water, followed by adding bamboo powder and mixing thoroughly. The solution is then dried at 95-110°C to obtain an activated carbon precursor. The activated carbon precursor is pre-carbonized at 300-400°C for 1.5-2.5 hours to obtain a pre-carbonized material. Potassium hydroxide and water are added to the pre-carbonized material, mixed, and then dried at 95-110°C for 3-5 hours. The solution is then heated to 600-900°C under nitrogen at a heating rate of 4.5-6°C / min and activated for 1-3 hours to obtain a carbonized material. The carbonized material is then soaked in dilute hydrochloric acid for 8-15 hours, washed, and dried to obtain a modified activated carbon.

[0038] Preferably, the mass ratio of the polymer to water in the polymer solution is 1:3-5.5.

[0039] Preferably, the mass ratio of the polymer to the bamboo powder is 1:3-5.

[0040] Preferably, the mass ratio of potassium hydroxide to pre-carbonized material is 1:0.3-1.

[0041] Preferably, the mass ratio of the pre-carbonized material to the amount of water added to the pre-carbonized material is 1:0.2-1.

[0042] Preferably, the dilute hydrochloric acid consists of hydrochloric acid and water, and the usage ratio of hydrochloric acid to water is 1 mol: 1.5-2.5 L.

[0043] Preferably, the washing solvent is water.

[0044] More preferably, in the preparation of modified activated carbon, on the basis of using polymers, maleic anhydride-styrenesulfonic acid copolymers can also be used. Maleic anhydride-styrenesulfonic acid copolymers can be synergistically prepared with polymers to prepare modified activated carbon, thereby increasing the specific surface area and adsorption performance of the modified activated carbon, more effectively adsorbing pollutants, thereby improving the overall purification effect, obtaining purer waste salt, and preparing high-quality sodium hexametaphosphate with low TOC content and inactive phosphate content.

[0045] Preferably, the mass ratio of the polymer to the maleic anhydride-styrene sulfonic acid copolymer is 1:0.1-1.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The present invention proposes a method for integrated purification and cascade resource utilization of industrial waste salt. First, sodium sulfate waste salt is made into a saturated solution, and then low-temperature recrystallization is performed to separate sodium sulfate and mother liquor wastewater. Then, a wetting detergent is added to the sodium sulfate for washing. After washing, purified salt and washing wastewater are separated; the mother liquor wastewater and washing wastewater are mixed to obtain a mixed solution, modified activated carbon is added to the mixed solution for purification, and rotary evaporation is performed to obtain waste salt. The waste salt is mixed with a phosphorus source for reaction, and then sodium hexametaphosphate is obtained through quenching, crystallization, and crushing. The method of the present invention can prepare purified salt and high-quality sodium hexametaphosphate. The purified salt can be further used for dyeing and finishing auxiliaries or bipolar membrane electrolysis systems to produce acid and alkali, and can be reused in the front-end production section. The sodium hexametaphosphate can be used as a washing auxiliaries, water softeners, detergents, etc. The method of the present invention realizes the high-value conversion of low-value waste salt, has good industrial application prospects, and has good economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other implementation drawings based on the provided drawings without inventive effort.

[0049] Figure 1 This is a flow chart of the integrated purification and cascade resource utilization method for industrial waste salt in Example 1;

[0050] Figure 2 This is a flow chart of the integrated purification and cascade resource utilization method for industrial waste salt in Example 2. DETAILED DESCRIPTION

[0051] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only 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 making creative efforts are within the scope of protection of the present invention.

[0052] The following first describes the concepts involved in this application with reference to the accompanying drawings. It should be noted that the following description of each concept is intended only to make the content of this application easier to understand and does not limit the scope of protection of this application. At the same time, the embodiments and features in the embodiments of this application can be combined with each other unless there is a conflict. The following detailed description of this application will be made with reference to the accompanying drawings and in conjunction with the embodiments.

[0053] Example 1:

[0054] Integrated purification and cascade resource utilization method for industrial waste salt:

[0055] S1: Sodium sulfate waste salt is added to water at 70°C to form a saturated solution. The temperature is then lowered to 20°C for crystallization separation. The crystallization is repeated twice to separate sodium sulfate and mother liquor wastewater. Water is then added to the sodium sulfate for washing for 0.25 hours, and the washing is repeated twice to separate purified salt and washing wastewater. The sodium sulfate waste salt is generated from the dyeing and finishing process of the printing and dyeing industry. It is produced after near-zero emission treatment. The mass ratio of water used for washing to sodium sulfate is 1:1.

[0056] S2: The mother liquor wastewater and washing wastewater in S1 are mixed to obtain a mixed solution, and the mixed solution is evaporated to obtain waste salt. Then, the waste salt is mixed with ammonium dihydrogen phosphate and reacted at 600℃ for 1 hour. After the reaction is completed, it is placed in cooling water for rapid cooling and crystallization, and then crushed to obtain sodium hexametaphosphate. The mass ratio of the waste salt to ammonium dihydrogen phosphate is 1:1.6. The process is as follows Figure 1 shown.

[0057] Example 2:

[0058] S1: Sodium sulfate waste salt is added to water at 70°C to form a saturated solution. The temperature is then lowered to 20°C for crystallization separation. The crystallization is repeated twice to separate sodium sulfate and mother liquor wastewater. Water is then added to the sodium sulfate for washing for 0.25 hours. The washing is repeated twice to separate purified salt and washing wastewater. The sodium sulfate waste salt is generated in the 1,4-butanediol production process of a fine chemical company. The mass ratio of water used for washing to sodium sulfate is 1:1.

[0059] S2: The mother liquor wastewater and washing wastewater in S1 are mixed to obtain a mixed solution, and the mixed solution is evaporated to obtain waste salt. Then, the waste salt is mixed with ammonium dihydrogen phosphate and reacted at 550℃ for 1 hour. After the reaction, it is placed in cooling water for rapid cooling and crystallization, and then crushed to obtain sodium hexametaphosphate. The mass ratio of the waste salt to ammonium dihydrogen phosphate is 1:1.55. The process is as follows Figure 2 shown.

[0060] Example 3:

[0061] Preparation of the polymer: Dimethylallylamine and β-bromophenylethane were added to acetone and reacted at 60°C for 30 hours. After the reaction, the mixture was first rotary evaporated, then recrystallized three times by adding a mixed solvent, and the solid was isolated and dried to obtain the intermediate. Acrylamide and methacryloyloxyethyltrimethylammonium chloride were added to water, and the pH was adjusted to 7. Then, the intermediate, azobisisobutylamidine hydrochloride, and ethylenediaminetetraacetic acid tetrasodium salt were added. The reaction was carried out under nitrogen for 6 hours. After the reaction, the polymer was washed with ethanol and dried. The mass ratio of dimethylallylamine and β-bromophenylethane is 1:3.2, the mass ratio of dimethylallylamine to acetone is 1 g:17 ml, the mixed solvent consists of acetone and ether, the volume ratio of acetone and ether is 1:3, the mass ratio of methacryloyloxyethyltrimethylammonium chloride to acrylamide is 1:0.425, the mass ratio of acrylamide to water is 1 g:8.33 ml, the mass ratio of methacryloyloxyethyltrimethylammonium chloride to the intermediate is 1:0.004, the mass ratio of the intermediate to azobisisobutylamidine hydrochloride is 1:0.0015, and the mass ratio of the intermediate to tetrasodium ethylenediaminetetraacetic acid is 1:0.00015.

[0062] Preparation of modified activated carbon: A polymer solution was prepared by mixing a polymer with water. The polymer solution was then mixed with bamboo powder and dried at 105°C to obtain an activated carbon precursor. The activated carbon precursor was pre-carbonized at 350°C for 2 hours to obtain a pre-carbonized material. Potassium hydroxide and water were added to the pre-carbonized material, and the mixture was dried at 105°C for 3.5 hours. The mixture was then heated to 800°C under nitrogen at a heating rate of 5°C / min for activation for 1.5 hours to obtain a carbonized material. The carbonized material was soaked in dilute hydrochloric acid for 10 hours, washed with water until neutral, and dried to obtain the modified activated carbon. The mass ratio of polymer to water in the polymer solution was 1:4, the mass ratio of polymer to bamboo powder was 1:4, the mass ratio of potassium hydroxide to pre-carbonized material was 1:0.5, and the mass ratio of pre-carbonized material to water added to the pre-carbonized material was 1:0.4. The dilute hydrochloric acid consisted of hydrochloric acid and water, with a hydrochloric acid to water ratio of 1 mol:2 L.

[0063] Integrated purification and cascade resource utilization method for industrial waste salt:

[0064] S1: Sodium sulfate waste salt is added to water at 70°C to form a saturated solution. The temperature is then lowered to 20°C for crystallization separation. The crystallization is repeated twice to separate sodium sulfate and mother liquor wastewater. Water is then added to the sodium sulfate for washing for 0.25 hours, and the washing is repeated twice to separate purified salt and washing wastewater. The sodium sulfate waste salt is generated from the dyeing and finishing process of the printing and dyeing industry. It is produced after near-zero emission treatment. The mass ratio of water used for washing to sodium sulfate is 1:1.

[0065] S2: The mother liquor and washing wastewater in S1 are mixed to obtain a mixed solution. Modified activated carbon is then added to the mixed solution and shaken for 2 hours. The purified solution is filtered and subjected to rotary evaporation to obtain waste salt. The waste salt is mixed with ammonium dihydrogen phosphate and reacted at 600°C for 1 hour. After the reaction, the mixture is quenched in cooling water for crystallization and crushed to obtain sodium hexametaphosphate. The ratio of modified activated carbon to mixed solution is 1g:100ml, and the mass ratio of waste salt to ammonium dihydrogen phosphate is 1:1.6.

[0066] Example 4:

[0067] The preparation of the polymer is the same as in Example 3.

[0068] The preparation of modified activated carbon is the same as in Example 3.

[0069] Integrated purification and cascade resource utilization method for industrial waste salt: The integrated purification and cascade resource utilization method for industrial waste salt in this embodiment is compared with Example 3, except that the usage ratio of modified activated carbon to mixed liquid is 1g:65ml, and other conditions and parameters are the same as Example 3.

[0070] Example 5:

[0071] The preparation of the polymer is the same as in Example 3.

[0072] The preparation of modified activated carbon is the same as in Example 3.

[0073] Integrated purification and cascade resource utilization method for industrial waste salt: The integrated purification and cascade resource utilization method for industrial waste salt in this embodiment is compared with Example 3, except that the usage ratio of modified activated carbon to mixed liquid is 1g:200ml, and other conditions and parameters are the same as Example 3.

[0074] Example 6:

[0075] The preparation of the polymer is the same as in Example 3.

[0076] Preparation of modified activated carbon: A polymer, maleic anhydride-styrene sulfonic acid copolymer, and water are mixed to obtain a polymer solution. The polymer solution is then mixed evenly with bamboo powder and dried at 105°C to obtain an activated carbon precursor. The activated carbon precursor is pre-carbonized at 350°C for 2 hours to obtain a pre-carbonized material. Potassium hydroxide and water are added to the pre-carbonized material, mixed, and then dried at 105°C for 3.5 hours. The mixture is then heated to 800°C under nitrogen at a heating rate of 5°C / min and activated for 1.5 hours to obtain a carbonized material. The carbonized material is soaked in dilute hydrochloric acid for 10 hours, washed with water until neutral, and dried to obtain the modified activated carbon. The mass ratio of the polymer to water in the polymer solution is 1:4, the mass ratio of the polymer to maleic anhydride-styrenesulfonic acid copolymer is 1:0.4, the mass ratio of the polymer to bamboo powder is 1:4, the mass ratio of potassium hydroxide to pre-carbonized material is 1:0.5, the mass ratio of the pre-carbonized material to the amount of water added to the pre-carbonized material is 1:0.4, and the dilute hydrochloric acid consists of hydrochloric acid and water, and the ratio of hydrochloric acid to water is 1 mol:2L.

[0077] Integrated purification and cascade resource utilization method for industrial waste salt: The integrated purification and cascade resource utilization method for industrial waste salt in this embodiment is compared with Example 3, except that the modified activated carbon is the activated carbon prepared in this embodiment, and other conditions and parameters are the same as Example 3.

[0078] Example 7:

[0079] The preparation of the polymer is the same as in Example 3.

[0080] Preparation of modified activated carbon: The preparation of modified activated carbon in this example is compared with that in Example 6, except that the mass ratio of the polymer to the maleic anhydride-styrene sulfonic acid copolymer is 1:0.75, and the other conditions and parameters are the same as in Example 6.

[0081] Integrated purification and cascade resource utilization method for industrial waste salt: The integrated purification and cascade resource utilization method for industrial waste salt in this embodiment is compared with that in Example 6, except that the modified activated carbon is the activated carbon prepared in this embodiment, and other conditions and parameters are the same as in Example 6.

[0082] Example 8:

[0083] The preparation of the polymer is the same as in Example 3.

[0084] Preparation of modified activated carbon: The preparation of modified activated carbon in this example is compared with that in Example 6, except that the mass ratio of the polymer to the maleic anhydride-styrene sulfonic acid copolymer is 1:0.15, and the other conditions and parameters are the same as in Example 6.

[0085] Integrated purification and cascade resource utilization method for industrial waste salt: The integrated purification and cascade resource utilization method for industrial waste salt in this embodiment is compared with that in Example 6, except that the modified activated carbon is the activated carbon prepared in this embodiment, and other conditions and parameters are the same as in Example 6.

[0086] Comparative Example 1:

[0087] The preparation of the polymer is the same as in Example 3.

[0088] The preparation of modified activated carbon is the same as in Example 3.

[0089] Integrated purification and cascade resource utilization method for industrial waste salt: The integrated purification and cascade resource utilization method for industrial waste salt in this embodiment is compared with Example 3, except that the usage ratio of modified activated carbon to mixed liquid is 1g:400ml, and other conditions and parameters are the same as Example 3.

[0090] Comparative Example 2:

[0091] Preparation of modified activated carbon: The preparation of modified activated carbon in this example is different from that in Example 6, except that no polymer is used. Other conditions and parameters are the same as in Example 6.

[0092] Integrated purification and cascade resource utilization method for industrial waste salt: The integrated purification and cascade resource utilization method for industrial waste salt in this embodiment is compared with that in Example 6, except that the modified activated carbon is the activated carbon prepared in this embodiment, and other conditions and parameters are the same as in Example 6.

[0093] Experimental Example 1:

[0094] The total organic carbon (TOC) of the purified salt was determined by direct determination. The TOC of the initial sodium sulfate waste salt, the purified salt prepared in Examples 1-8 and Comparative Examples 1-2 was determined. The salt was first pre-acidified, then aerated with nitrogen to remove CO2 generated by the decomposition of various carbonates, and then injected into the instrument for determination.

[0095] The results showed that the TOC content of the initial sodium sulfate waste salt used in Example 1 was 1200 mg / kg, and the TOC content of the purified salt prepared after recrystallization and washing was reduced to 40.23 mg / kg; the TOC content of the initial sodium sulfate waste salt used in Example 2 was 1800 mg / kg, and the TOC content of the purified salt prepared after recrystallization and washing was reduced to 38.27 mg / kg; the TOC content of the purified salts prepared in Examples 3-8 and Comparative Examples 1-2 was basically the same as that in Example 1.

[0096] Experimental Example 2:

[0097] The total organic carbon (TOC) of sodium hexametaphosphate was determined by direct determination. The TOC of the sodium hexametaphosphate prepared in Examples 1-8 and Comparative Examples 1-2 was determined by pre-acidification, nitrogen aeration was then introduced to remove CO2 generated by the decomposition of various carbonates, and then the TOC was injected into the instrument for determination.

[0098] Table 1 Determination results of total organic carbon (TOC) of sodium hexametaphosphate

[0099]

[0100] The results are shown in Table 1. Compared with Example 3, Example 1 shows that the TOC content of sodium hexametaphosphate prepared in Example 3 is lower than that in Example 1, indicating that the use of modified activated carbon can effectively reduce the TOC content of the prepared sodium hexametaphosphate; compared with Example 4, Example 3 shows that the increase in the amount of modified activated carbon used within a certain range can further reduce the TOC content of the prepared sodium hexametaphosphate; compared with Example 5, Example 3 shows that the reduction in the amount of modified activated carbon used within a certain range can inhibit the reduction in the TOC content of the prepared sodium hexametaphosphate; compared with Example 6, Example 3 shows that on the basis of using a polymer, maleic anhydride-styrene sulfonic acid copolymer is used to further prepare modified activated carbon, and this modified activated carbon purifies the mixed solution and prepares sodium hexametaphosphate, which can reduce the TOC content of sodium hexametaphosphate; compared with Example 7, Example 6 shows that maleic anhydride-styrene sulfonic acid copolymer can reduce the TOC content of sodium hexametaphosphate. Increasing the usage of the olefin sulfonic acid copolymer within a certain range can improve the effect of the prepared modified activated carbon, thereby further reducing the TOC content of the prepared sodium hexametaphosphate; Example 6, compared with Example 8, shows that when the usage of the maleic anhydride-styrene sulfonic acid copolymer is reduced within a certain range, the effect of the prepared modified activated carbon is weakened, thereby resulting in an increase in the TOC content of the prepared sodium hexametaphosphate; Example 3, compared with Comparative Example 1, shows that the usage of the modified activated carbon needs to be within an appropriate range, and too low an amount has no obvious effect on reducing the TOC content of the prepared sodium hexametaphosphate; Example 6, compared with Comparative Example 2, shows that the polymer and the maleic anhydride-styrene sulfonic acid copolymer need to be used together to prepare the modified activated carbon, and the modified activated carbon prepared using the maleic anhydride-styrene sulfonic acid copolymer alone has no obvious effect on reducing the TOC content of the subsequently prepared sodium hexametaphosphate.

[0101] Experimental Example 3:

[0102] The inactive phosphate content of sodium hexametaphosphate was determined according to the sodium hexametaphosphate industry standard HG / T 2519-2017, and the inactive phosphate content of the sodium hexametaphosphate prepared in Examples 1-8 and Comparative Examples 1-2 was determined.

[0103] Table 2 Determination results of inactive phosphate content of sodium hexametaphosphate

[0104]

[0105] The results are shown in Table 2. Compared with Example 1, Example 3 shows that the inactive phosphate content of the sodium hexametaphosphate prepared in Example 3 is lower than that in Example 1, indicating that the use of modified activated carbon can effectively improve the quality of the prepared sodium hexametaphosphate; Compared with Example 4, Example 3 shows that the increase in the amount of modified activated carbon used within a certain range can further reduce the inactive phosphate content, that is, improve the quality; Compared with Example 5, Example 3 shows that the reduction in the amount of modified activated carbon used within a certain range increases the inactive phosphate content of the prepared sodium hexametaphosphate and reduces the quality; Compared with Example 6, Example 3 shows that on the basis of using a polymer, maleic anhydride-styrene sulfonic acid copolymer is used to further prepare modified activated carbon, the modified activated carbon purifies the mixed solution, and prepares sodium hexametaphosphate, the inactive phosphate content of the prepared sodium hexametaphosphate is reduced, and the quality is improved; Compared with Example 7, Example 6 shows that maleic anhydride-styrene sulfonic acid copolymer is used to further prepare modified activated carbon, the modified activated carbon purifies the mixed solution, and prepares sodium hexametaphosphate, the inactive phosphate content of the prepared sodium hexametaphosphate is reduced, and the quality is improved. Increasing the usage of styrenesulfonic acid copolymer within a certain range can improve the effect of the modified activated carbon prepared, thereby further reducing the inactive phosphate content of the prepared sodium hexametaphosphate and improving the quality; Example 6, compared with Example 8, shows that when the usage of maleic anhydride-styrenesulfonic acid copolymer is reduced within a certain range, the effect of the modified activated carbon prepared is weakened, thereby increasing the inactive phosphate content of the prepared sodium hexametaphosphate and reducing the quality; Example 3, compared with Comparative Example 1, shows that the usage of modified activated carbon needs to be within an appropriate range, and too low an amount has no obvious effect on improving the quality of the prepared sodium hexametaphosphate; Example 6, compared with Comparative Example 2, shows that the polymer and maleic anhydride-styrenesulfonic acid copolymer need to be used together to prepare modified activated carbon, and the modified activated carbon prepared using maleic anhydride-styrenesulfonic acid copolymer alone has no obvious effect on improving the quality of the subsequently prepared sodium hexametaphosphate.

[0106] The embodiments and / or implementation methods described above are only used to illustrate the preferred embodiments and / or implementation methods for realizing the technology of the present invention, and do not impose any form of limitation on the implementation methods of the technology of the present invention. Any person skilled in the art may make slight changes or modifications to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but they should still be regarded as technologies or embodiments that are essentially the same as the present invention.

[0107] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. The above is only the preferred implementation method of this application. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of this application, they can also make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the scope of protection of this application.

Claims

1. A method for integrated purification and cascade resource utilization of industrial waste salt, comprising: S1: First, sodium sulfate waste salt is added to water to form a saturated solution, and then low-temperature recrystallization is separated to obtain sodium sulfate and mother liquor wastewater. Then, a wetting detergent is added to the sodium sulfate for washing. After washing, purified salt and washing wastewater are separated; S2: The mother liquor wastewater and washing waste liquid obtained in S1 are mixed to obtain a mixed solution, modified activated carbon is added to the mixed solution for purification, and waste salt is obtained by rotary evaporation, the waste salt is mixed with a phosphorus source for reaction, and then sodium hexametaphosphate is obtained by quenching, crystallizing and crushing. The modified activated carbon is prepared from bamboo powder and a polymer, and the polymer is prepared from acrylamide, methacryloyloxyethyltrimethylammonium chloride, dimethylallylamine and β-bromophenylethane; In the preparation of the polymer, dimethylallylamine and β-bromophenylethane are added to acetone and reacted at 55-70°C for 20-40 hours. After the reaction, the intermediate is obtained by rotary evaporation, recrystallization, and drying. Acrylamide and methacryloyloxyethyltrimethylammonium chloride are added to water, the pH is adjusted to 6.5-7.5, and then the intermediate, azobisisobutylamidine hydrochloride, and ethylenediaminetetraacetic acid tetrasodium salt are added. The reaction is carried out under nitrogen for 4-8 hours. After the reaction, the polymer is washed and dried. The mass ratio of the polymer to the bamboo powder is 1:3-5; the mass ratio of the modified activated carbon to the mixed liquid in S2 is 1g:50-250ml.

2. The method for integrated purification and cascade resource utilization of industrial waste salt according to claim 1, characterized in that: The sodium sulfate waste salt in S1 includes sodium sulfate waste salt produced by the printing and dyeing production process and the 1,4-butanediol production process.

3. The method for integrated purification and cascade resource utilization of industrial waste salt according to claim 1, characterized in that: The low-temperature recrystallization in S1 includes direct low-temperature cooling crystallization and two-phase aqueous solvent crystallization, and the two-phase aqueous solvent is at least two of methanol, acetone, ethanol and saturated brine.

4. The method for integrated purification and cascade resource utilization of industrial waste salt according to claim 1, characterized in that: The infiltration detergent in S1 is at least one of water, saturated salt water, methanol, acetone and ethanol, and the mass ratio of the infiltration detergent to the sodium sulfate is 1:0.375-1.

5. The method for integrated purification and cascade resource utilization of industrial waste salt according to claim 1, characterized in that: The phosphorus source in S2 is at least one of phosphoric acid and ammonium dihydrogen phosphate, and the mass ratio of the waste salt to the phosphorus source is 1:1.2-2.

1.

6. The method for integrated purification and cascade resource utilization of industrial waste salt according to claim 1, characterized in that: The temperature for preparing the saturated solution in S1 is 65-75°C, and the temperature for recrystallization and washing is 15-25°C.

7. The method for integrated purification and cascade resource utilization of industrial waste salt according to claim 1, characterized in that: The reaction temperature of the mixed reaction of the waste salt in S2 and the phosphorus source is 500-650° C., and the reaction time is 0.8-2 h.

Images