Integrated purification and gradient recycling method for industrial waste salt

Abstract

The invention discloses an industrial waste salt integrated purification and gradient recycling method, and relates to the technical field of waste salt resource utilization. The specific preparation method comprises the following steps: firstly preparing sodium sulfate waste salt into a saturated solution, then performing low-temperature recrystallization separation to obtain sodium sulfate and mother liquor wastewater, and then adding an infiltration detergent into the sodium sulfate for washing and separation to obtain purified salt and washing waste liquid; the method comprises the following steps: mixing mother liquor wastewater and washing waste liquid, adding modified activated carbon for purification, performing rotary evaporation to obtain waste salt, mixing the waste salt with a phosphorus source for reaction, and performing shock cooling crystallization and crushing to obtain sodium hexametaphosphate. According to the method, purified salt and high-quality sodium hexametaphosphate can be prepared, the purified salt can be continuously used for dyeing and finishing auxiliaries or a bipolar membrane electrolysis system to produce acid and alkali and can be reused for front-end production, and sodium hexametaphosphate can be used as a washing auxiliary, a water softener, a cleaning agent and the like. The method realizes high-value conversion of low-value waste salt, and has good industrial application prospects, economic benefits and environmental benefits.

Description

Technical Field

[0001] The 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 mainly comes from the end of near-zero discharge of industrial wastewater, mainly concentrated in agriculture, printing and dyeing, coal chemical industry, fine chemical industry and other industries. The main components are sodium chloride and sodium sulfate, and the current annual output exceeds 20 million tons. Most waste salt contains difficult-to-degrade organic matter and has been included in the "National List of Hazardous Wastes" since 2016. At the same time, waste salt treatment is difficult and the treatment cost is high. Enterprises adopt the method of temporary storage or mixed utilization, which poses serious environmental risks and causes 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 been fully reflected, and there are few cases of cascade resource utilization of waste salt. In particular, thermal 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 thermal treatment of waste salt, and by mixing with certain substances, the waste salt can be removed from organic matter and 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 that the existing waste salt treatment process is imperfect and has not been effectively cascaded resource utilization.

[0005] In order to solve the above technical problems, the present invention specifically provides the following technical solutions: The present invention discloses a method for integrated purification and cascade resource utilization of industrial waste salt, comprising: S1: First, sodium sulfate waste salt is added into water to prepare a saturated solution, and then low-temperature recrystallization is performed to separate sodium sulfate and mother liquor wastewater, and then a wetting detergent is added to the sodium sulfate for washing, and after washing, purified salt and washing wastewater are separated; S2: Mix the mother liquor wastewater and washing waste liquid obtained in S1 to obtain a mixed solution, add modified activated carbon to the mixed solution for purification, perform rotary evaporation to obtain waste salt, mix the waste salt with a phosphorus source for reaction, and then obtain sodium hexametaphosphate through quenching, crystallization 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-bromobenzene ethane. Using modified activated carbon to purify the mixed solution can effectively remove organic pollutants and other toxic and harmful substances and impurities in the mixed solution, thereby obtaining relatively pure waste salt, and then preparing sodium hexametaphosphate with low TOC content and high quality.

[0006] 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.

[0007] 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.

[0008] 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 sodium sulfate is 1:0.375-1.

[0009] Preferably, the dosage ratio of modified activated carbon to mixed liquid in S2 is 1g:50-250ml.

[0010] Preferably, the phosphorus source in S2 is at least one of phosphoric acid and diammonium phosphate, and the mass ratio of the waste salt to the phosphorus source is 1:1.2-2.1.

[0011] 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.

[0012] 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.

[0013] The invention also discloses use of the sodium hexametaphosphate prepared by the method in preparing a water treatment agent.

[0014] The present invention discloses a method for integrated purification and cascade resource utilization of industrial waste salt, comprising: S1: First, sodium sulfate waste salt is added into water at 65-75°C to prepare a saturated solution, then the temperature is lowered to 15-25°C, and sodium sulfate and mother liquor wastewater are separated by recrystallization, and then a wetting detergent is added into the sodium sulfate for washing, and purified salt and washing wastewater are separated after washing is completed; S2: The mother liquor wastewater obtained in S1 and the washing waste liquid are mixed to obtain a mixed liquid, modified activated carbon is added to the mixed liquid and oscillated for 1.5-3 hours, and then the purified liquid is separated and rotary evaporated 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.

[0015] 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.

[0016] 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.

[0017] 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 sodium sulfate is 1:0.375-1.

[0018] Preferably, the dosage ratio of modified activated carbon to mixed liquid in S2 is 1g:50-250ml.

[0019] Preferably, the phosphorus source in S2 is at least one of phosphoric acid and diammonium phosphate.

[0020] Preferably, the mass ratio of the waste salt to the phosphorus source used in S2 is 1:1.2-2.1.

[0021] The present invention discloses a method for preparing a polymer, which specifically comprises: Add dimethylallylamine and β-bromobenzene ethane to acetone, react at 55-70°C for 20-40 hours, and obtain the intermediate by rotary evaporation, recrystallization and drying after the reaction. Add acrylamide and methacryloyloxyethyl trimethylammonium chloride to water, adjust the pH to 6.5-7.5, then add the intermediate, azobisisobutylamidine hydrochloride and ethylenediaminetetraacetic acid tetrasodium salt, react under nitrogen for 4-8 hours, wash and dry after the reaction to obtain the polymer.

[0022] Preferably, the mass ratio of dimethylallylamine to β-bromophenylethane is 1:3-4.

[0023] Preferably, the usage ratio of dimethylallylamine to acetone is 1 g: 12-22 ml.

[0024] Preferably, the solvent used for recrystallization is a mixed solvent, the mixed solvent consists of acetone and diethyl ether, and the volume ratio of acetone to diethyl ether is 1:2.5-4.

[0025] Preferably, the mass ratio of methacryloyloxyethyltrimethylammonium chloride to acrylamide is 1:0.35-0.5.

[0026] Preferably, the mass ratio of acrylamide to water is 1 g:7.5-9 ml.

[0027] Preferably, the mass ratio of methacryloyloxyethyltrimethylammonium chloride to the intermediate is 1:0.003-0.005.

[0028] Preferably, the mass ratio of the intermediate to azobisisobutylamidine hydrochloride is 1:0.001-0.002.

[0029] Preferably, the mass ratio of the intermediate to the tetrasodium salt of ethylenediaminetetraacetic acid is 1:0.0001-0.0003.

[0030] The present invention discloses a method for preparing modified activated carbon, which is specifically: The polymer is mixed with water to obtain a polymer solution, and then bamboo powder is added and mixed evenly, and then dried at 95-110°C to obtain an activated carbon precursor. The activated carbon precursor is pre-carbonized at 300-400°C for 1.5-2.5h to obtain a pre-carbonized material. Potassium hydroxide and water are added to the pre-carbonized material and mixed, and then dried at 95-110°C for 3-5h, and then heated to 600-900°C at a heating rate of 4.5-6°C / min under nitrogen conditions for activation for 1-3h to obtain a carbonized material, and the carbonized material is soaked in dilute hydrochloric acid for 8-15h, and then washed and dried to obtain modified activated carbon.

[0031] Preferably, the mass ratio of the polymer to water in the polymer solution is 1:3-5.5.

[0032] Preferably, the mass ratio of the polymer to the bamboo powder is 1:3-5.

[0033] Preferably, the mass ratio of potassium hydroxide to pre-carbonized material is 1:0.3-1.

[0034] 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.

[0035] Preferably, the dilute hydrochloric acid consists of hydrochloric acid and water, and the usage ratio of hydrochloric acid to water is 1 mol: 1.5-2.5L.

[0036] Preferably, the washing solvent is water.

[0037] More preferably, in the preparation of modified activated carbon, maleic anhydride-styrene sulfonic acid copolymer can be used in addition to the polymer. The maleic anhydride-styrene sulfonic acid copolymer can be synergistically prepared with the polymer to improve the specific surface area and adsorption performance of the modified activated carbon, and more effectively adsorb 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.

[0038] Preferably, the mass ratio of the polymer to the maleic anhydride-styrene sulfonic acid copolymer is 1:0.1-1.

[0039] Compared with the prior art, the present invention has the following beneficial effects: The present invention proposes an integrated purification and cascade resource utilization method for 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 the washing wastewater 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 sodium hexametaphosphate is obtained by quenching, crystallizing and crushing. The method of the present invention can prepare purified salt and high-quality sodium hexametaphosphate. The purified salt can continue to be 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. 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

[0040] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0041] Figure 1 This is a flow chart of the integrated purification and cascade resource utilization method of industrial waste salt in Example 1; 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

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0043] The following first describes the concepts involved in the present application in conjunction with the accompanying drawings. It should be noted that the following description of each concept is only to make the content of the present application easier to understand, and does not limit the scope of protection of the present application; at the same time, the embodiments and features in the embodiments of the present application can be combined with each other in the absence of conflict. The present application will be described in detail with reference to the accompanying drawings and in conjunction with the embodiments.

[0044] Embodiment 1: Integrated purification and cascade resource utilization method for industrial waste salt: S1: At 70°C, sodium sulfate waste salt is added to water to make a saturated solution, and then the temperature is lowered to 20°C for crystallization separation. The crystallization is repeated twice to separate sodium sulfate and mother liquor wastewater. Then water is added to the sodium sulfate for washing for 0.25h, and the washing is repeated twice to separate purified salt and washing wastewater. The sodium sulfate waste salt is the wastewater generated in the dyeing and finishing process of the printing and dyeing industry. The sodium sulfate waste salt generated after near-zero emission treatment has a mass ratio of 1:1 for the amount of water used for washing and the amount of sodium sulfate used.

[0045] S2: Mix the mother liquor wastewater and washing wastewater in S1 to obtain a mixed solution, evaporate the mixed solution to obtain waste salt, then mix the waste salt with diammonium phosphate, react at 600℃ for 1h, place in cooling water for rapid cooling and crystallization after the reaction, and obtain sodium hexametaphosphate after crushing. The mass ratio of waste salt to diammonium phosphate is 1:1.6. The process is as follows Figure 1 shown.

[0046] Embodiment 2: S1: At 70°C, sodium sulfate waste salt is added to water to prepare a saturated solution, and then the temperature is lowered to 20°C for crystallization separation. The crystallization is repeated twice to separate sodium sulfate and mother liquor wastewater. Then water is added to the sodium sulfate for washing for 0.25h, and the washing is repeated twice to separate purified salt and washing wastewater. The sodium sulfate waste salt is the sodium sulfate waste salt produced in the production process of 1,4-butanediol of a fine chemical enterprise, and the mass ratio of the amount of water used for washing to the amount of sodium sulfate used is 1:1.

[0047] S2: Mix the mother liquor wastewater and washing wastewater in S1 to obtain a mixed solution, evaporate the mixed solution to obtain waste salt, then mix the waste salt with diammonium phosphate, react at 550℃ for 1h, place in cooling water for rapid cooling and crystallization after the reaction, and crush to obtain sodium hexametaphosphate. The mass ratio of waste salt to diammonium phosphate is 1:1.55. The process is as follows Figure 2 shown.

[0048] Embodiment 3: Preparation of polymer: Add dimethylallylamine and β-bromophenylethane to acetone, react at 60°C for 30 hours, and then add a mixed solvent for recrystallization three times to separate the solid, and finally dry to obtain the intermediate. Add acrylamide and methacryloyloxyethyl trimethylammonium chloride to water, adjust the pH to 7, then add the intermediate, azobisisobutylamidine hydrochloride and ethylenediaminetetraacetic acid tetrasodium salt, react under nitrogen for 6 hours, and wash with ethanol after the reaction to obtain the polymer. The mass ratio of dimethylallylamine and β-bromophenylethane is 1:3.2, the mass ratio of dimethylallylamine to acetone is 1g:17ml, 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 1g:8.33ml, 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.

[0049] Preparation of modified activated carbon: The polymer is mixed with water to obtain a polymer solution, and then the polymer solution is evenly mixed 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 2h to obtain a pre-carbonized material. Potassium hydroxide and water are added to the pre-carbonized material and mixed, and then dried at 105°C for 3.5h, and then heated to 800°C at a heating rate of 5°C / min under nitrogen conditions for activation for 1.5h to obtain a carbonized material. The carbonized material is soaked in dilute hydrochloric acid for 10h, then washed with water to neutrality, and then dried to obtain 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 bamboo powder is 1:4, the mass ratio of potassium hydroxide to the 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, the dilute hydrochloric acid is composed of hydrochloric acid and water, and the amount ratio of hydrochloric acid to water is 1mol:2L.

[0050] Integrated purification and cascade resource utilization method for industrial waste salt: S1: At 70°C, sodium sulfate waste salt is added to water to make a saturated solution, and then the temperature is lowered to 20°C for crystallization separation. The crystallization is repeated twice to separate sodium sulfate and mother liquor wastewater. Then water is added to the sodium sulfate for washing for 0.25h, and the washing is repeated twice to separate purified salt and washing wastewater. The sodium sulfate waste salt is the wastewater generated in the dyeing and finishing process of the printing and dyeing industry. The sodium sulfate waste salt generated after near-zero emission treatment has a mass ratio of 1:1 for the amount of water used for washing and the amount of sodium sulfate used.

[0051] S2: Mix the mother liquor wastewater and washing wastewater in S1 to obtain a mixed solution, then add modified activated carbon to the mixed solution and shake for 2 hours, filter out the purified solution, and obtain waste salt by rotary evaporation. Mix the waste salt with diammonium phosphate, react at 600℃ for 1 hour, and place it in cooling water for quenching and crystallization after the reaction, and obtain sodium hexametaphosphate after crushing. The usage ratio of modified activated carbon to mixed solution is 1g:100ml, and the mass ratio of waste salt to diammonium phosphate is 1:1.6.

[0052] Embodiment 4: The preparation of the polymer is the same as in Example 3.

[0053] The preparation of modified activated carbon is the same as in Example 3.

[0054] 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.

[0055] Embodiment 5: The preparation of the polymer is the same as in Example 3.

[0056] The preparation of modified activated carbon is the same as in Example 3.

[0057] 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.

[0058] Embodiment 6: The preparation of the polymer is the same as in Example 3.

[0059] Preparation of modified activated carbon: A polymer, maleic anhydride-styrene sulfonic acid copolymer and water are mixed to obtain a polymer solution, and then the polymer solution is evenly mixed 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 and mixed, and then dried at 105°C for 3.5 hours, and then heated to 800°C at a heating rate of 5°C / min under nitrogen conditions for 1.5 hours to obtain a carbonized material. The carbonized material is soaked in dilute hydrochloric acid for 10 hours, then washed with water until neutral, and then dried to obtain 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-styrene sulfonic 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 water added to the pre-carbonized material is 1:0.4, and the dilute hydrochloric acid consists of hydrochloric acid and water, and the usage ratio of hydrochloric acid to water is 1 mol:2L.

[0060] 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 3, 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 3.

[0061] Embodiment 7: The preparation of the polymer is the same as in Example 3.

[0062] Preparation of modified activated carbon: The preparation of modified activated carbon in this embodiment is compared with that in Example 6, except that the mass ratio of the polymer to the maleic anhydride-styrene sulfonic acid copolymer used is 1:0.75, and the other conditions and parameters are the same as in Example 6.

[0063] 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.

[0064] Embodiment 8: The preparation of the polymer is the same as in Example 3.

[0065] Preparation of modified activated carbon: The preparation of modified activated carbon in this embodiment is compared with that in Example 6, except that the mass ratio of the polymer to the maleic anhydride-styrene sulfonic acid copolymer used is 1:0.15, and the other conditions and parameters are the same as in Example 6.

[0066] 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.

[0067] Comparative Example 1: 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:400ml, and other conditions and parameters are the same as Example 3.

[0070] Comparative Example 2: Preparation of modified activated carbon: The preparation of modified activated carbon in this example is compared with that in Example 6, except that no polymer is used, and other conditions and parameters are the same as in Example 6.

[0071] 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.

[0072] Experimental Example 1: The total organic carbon (TOC) of the purified salt was determined by direct determination method. The TOC of the initial sodium sulfate waste salt, the purified salt 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 injected into the instrument for determination.

[0073] 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. Experimental Example 2: The total organic carbon (TOC) of sodium hexametaphosphate was determined by direct determination method. The TOC of 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 injected into the instrument for determination.

[0074] Table 1 Determination results of total organic carbon (TOC) of sodium hexametaphosphate

[0075] 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 use of modified activated carbon 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 use of modified activated carbon within a certain range will inhibit the reduction of 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 the 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 a suitable 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.

[0076] Experimental Example 3: 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.

[0077] Table 2 Determination results of inactive phosphate content of sodium hexametaphosphate

[0078] The results are shown in Table 2. Compared with Example 1 and Example 3, the inactive phosphate 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 improve the quality of the prepared sodium hexametaphosphate; compared with Example 4, Example 3 shows that the increase in the use of modified activated carbon 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 use of modified activated carbon 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 prepared modified activated carbon, 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 prepared modified activated carbon 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.

[0079] 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 are not intended to limit the implementation methods of the technology of the present invention in any form. Any technical personnel in this field 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.

[0080] 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 its 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 and the objective existence of infinite specific structures, ordinary technicians in this technical field can make several improvements, modifications or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the concept and technical solution of the invention 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 into water to prepare a saturated solution, and then low-temperature recrystallization is performed to separate sodium sulfate and mother liquor wastewater, and then a wetting detergent is added to the sodium sulfate for washing, and after washing, purified salt and washing wastewater are separated; S2: the mother liquor wastewater obtained in S1 and the washing waste liquid 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 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, methacryloyloxyethyl trimethylammonium chloride, dimethylallylamine and beta-bromophenylethane.

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 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 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 dosage ratio of the modified activated carbon to the mixed liquid in S2 is 1g:50-250ml.

6. 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 diammonium phosphate, and the mass ratio of the waste salt to the phosphorus source is 1:1.2-2.

1.

7. 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.

8. 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.

9. Use of the sodium hexametaphosphate prepared by any method of claims 1 to 8 in the preparation of a water treatment agent.

Images