Innocuous solid waste and method for preparing the same

Abstract

The present application relates to the technical field of environmental protection, and particularly relates to a harmless solid waste and a preparation method thereof. The preparation method of the harmless solid waste comprises: performing acid soaking treatment on phosphogypsum, performing solid-liquid separation to obtain filtrate one and residue one, performing alkali soaking treatment on the residue one, adding persulfate for oxidation treatment, performing solid-liquid separation to obtain filtrate two and the harmless solid waste, mixing the filtrate one and the filtrate two to obtain mixed filtrate, and finally using an adsorbent to adsorb and recover phosphorus in the mixed filtrate. The present application can not only effectively remove inorganic phosphorus and organic phosphorus in the phosphogypsum, but also remove fluorine ions, heavy metal ions and organic pollutants in the phosphogypsum, so that the harmless treatment of the phosphogypsum is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental protection, in particular to a harmless solid waste and a preparation method thereof. BACKGROUND

[0002] Phosphogypsum is a large amount of industrial waste produced in the process of wet-process phosphoric acid production, and 4.5-5 tons of phosphogypsum will be produced for every ton of phosphoric acid. At present, phosphogypsum is mainly landfilled, that is, a phosphogypsum slag field is built by using the principle of engineering. However, land storage of phosphogypsum not only occupies a large amount of land, but also brings great threat to the environment. For example, phosphogypsum will form strong acid wastewater mainly containing phosphoric acid in the process of long-term open-air storage under the action of sunlight, rain, weathering and decomposition, and carry other dissociated harmful components to penetrate into the ground, eventually leading to leaching pollution of soil, surface water and shallow groundwater, so it is necessary to seek a reasonable harmless treatment approach for phosphogypsum to realize the sustainable development of phosphate fertilizer industry and the high utilization of phosphogypsum.

[0003] Phosphogypsum contains pollutants such as phosphorus, fluorine, heavy metals and organic pollutants, among which phosphorus is the main pollutant. The phosphorus in phosphogypsum can be divided into inorganic phosphorus and organic phosphorus, and the inorganic phosphorus can be divided into easily soluble phosphorus, AL-P (aluminum phosphate salt), Fe-P (iron phosphate salt), Ca-P (calcium phosphate salt) and O-P (occluded phosphorus). The various forms of phosphorus lead to the continuous transformation of phosphorus in phosphogypsum. The existing water washing, lime neutralization, organic flotation and high-temperature calcination can only remove part of the phosphorus in phosphogypsum, which limits the resource utilization of phosphogypsum. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the defect that the prior art can only remove part of the phosphorus in phosphogypsum, so as to provide a harmless solid waste and a preparation method thereof which solve the above problems.

[0005] To achieve the above purpose, the present application provides the following technical scheme:

[0006] A preparation method of a harmless solid waste, comprising: subjecting phosphogypsum to acid soaking treatment, solid-liquid separation to obtain filtrate one and residue one, then subjecting the residue one to alkali soaking treatment and adding persulfate for oxidation treatment, solid-liquid separation to obtain filtrate two and the harmless solid waste, mixing the filtrate one and the filtrate two to obtain mixed filtrate, and finally using an adsorbent to adsorb and recover phosphorus in the mixed filtrate.

[0007] Preferably, the acid is an organic acid; the organic acid is oxalic acid or / and citric acid; the concentration of the acid is 0.01-0.05 mol / L;

[0008] And / or, the base is sodium hydroxide or / and potassium hydroxide; the concentration of the base is 0.01-0.05 mol / L;

[0009] And / or, the persulfate is sodium persulfate or / and potassium persulfate.

[0010] Preferably, the temperature of the acid soaking treatment is 30-40℃, and the duration is 10-30 min;

[0011] And / or, the temperature of the alkali soaking treatment is 40-60℃; the duration is 10-30 min.

[0012] Preferably, the mass ratio of the phosphogypsum to the persulfate is (20-100):1.

[0013] Preferably, the pH of the mixed filtrate is 6-10;

[0014] And / or, the mass ratio of the adsorbent to the mixed filtrate is 1:100.

[0015] Preferably, the adsorbent is La / Al / CS hydrogel beads;

[0016] The preparation process of the La / Al / CS hydrogel beads comprises: dissolving a lanthanum salt and an aluminum salt in a solvent to prepare a mixed solution, then adding a precipitant to perform a hydrothermal reaction to obtain a La / Al composite material, and finally performing embedding treatment with an embedding agent.

[0017] Preferably, in the mixed solution, the concentration of the lanthanum salt is 50-100 g / L; the concentration of the aluminum salt is 50-100 g / L;

[0018] And / or, the lanthanum salt is lanthanum nitrate;

[0019] And / or, the aluminum salt is aluminum chloride;

[0020] And / or, the solvent is water;

[0021] And / or, the precipitant is a base; the concentration of the base is 0.5 mol / L; the base is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate;

[0022] And / or, the volume ratio of the precipitant to the mixed solution is 1:1;

[0023] And / or, the embedding agent is a natural polymer material; the natural polymer material is at least one of peanut shell, coconut shell, sawdust and straw; the natural polymer material is a pretreated natural cellulose; the pretreatment is that the natural polymer material is crushed, sieved, and then soaked in alkali; the alkali is at least one of sodium hydroxide and potassium hydroxide; the concentration of the alkali is 20-50 g / L; the soaking time of the alkali is greater than or equal to 90 min; and the soaking in alkali is followed by filtration, water washing and drying.

[0024] Preferably, the embedding process is that the pretreated natural polymer material is dissolved in an ionic liquid to obtain a natural polymer material solution, then glutaraldehyde and La / Al composite material are added, and then a hydrogel solution is prepared by water bath stirring, finally the hydrogel solution is added dropwise into water by using a peristaltic pump, and the La / Al / CS hydrogel beads are obtained by sequentially performing standing, filtering, washing and freeze-drying at room temperature.

[0025] The concentration of the natural polymer material solution is 0.1 g / mL.

[0026] The mass ratio of the natural polymer material to glutaraldehyde and La / Al composite material is 1:0.1:1.

[0027] The temperature of the water bath is 100 DEG C, and the time length is 2 h.

[0028] The ionic liquid is 1-allyl-3-methylimidazolium chloride or 1-butyl-3-methylimidazolium chloride.

[0029] Preferably, the temperature of the hydrothermal reaction is 80 DEG C, and the time length is 12 h.

[0030] Preferably, the La / Al / CS hydrogel beads are eluted by using an eluent after adsorbing phosphorus.

[0031] The eluent is sodium hydroxide or / and potassium hydroxide.

[0032] The concentration of the eluent is 1-2 mol / L.

[0033] The mass ratio of the La / Al / CS hydrogel beads to the eluent is 1:10.

[0034] The time length of the elution is 1 h.

[0035] The elution is followed by washing with water.

[0036] The application also provides a harmless solid waste prepared by the above-mentioned method for preparing a harmless solid waste.

[0037] The technical scheme of the application has the following advantages:

[0038] 1. A preparation method of a solid waste harmless material, comprising: performing acid soaking treatment on phosphogypsum, and performing solid-liquid separation to obtain filtrate one and residue one; performing alkali soaking treatment on the residue one, adding persulfate for oxidation treatment, and performing solid-liquid separation to obtain filtrate two and the solid waste harmless material; mixing the filtrate one and the filtrate two to obtain mixed filtrate; and using an adsorbent to adsorb and recover phosphorus in the mixed filtrate. In the present application, the acid soaking treatment can effectively destroy the crystal structure in the phosphogypsum, thereby releasing the eutectic phosphorus and effectively removing the easily soluble phosphorus and Ca-P (calcium phosphate salt) phosphorus; the alkali soaking treatment can release the phosphorus in AL-P (aluminum phosphate salt) and Fe-P (iron phosphate salt); the alkali soaking treatment is performed while adding the persulfate, which can oxidize the organic phosphorus in the phosphogypsum into inorganic phosphorus and release O-P (occluded phosphorus) to be removed with the alkali liquor; through the present application, the inorganic phosphorus and the organic phosphorus in the phosphogypsum can be effectively removed, and the fluorine ions, heavy metal ions and organic pollutants in the phosphogypsum can also be removed, thereby realizing the harmless treatment of the phosphogypsum; the mixing of the filtrate one and the filtrate two can not only neutralize the acid and alkali properties of the filtrate, but also need not use neutralizing acid / alkali for treatment, and is beneficial to the selective adsorption of the adsorbent to the phosphate in the filtrate.

[0039] 2. The La / Al / CS hydrogel beads used in the present application have high selective adsorption to phosphate, are less affected by other competitive anions, and have high regeneration performance, and the adsorption capacity of the La / Al / CS hydrogel beads to phosphate can still reach 74.3% of the initial adsorption capacity after 5 times of adsorption and desorption. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the specific embodiments or the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0041] Figure 1 is a process flow chart for preparing the solid waste harmless material in the present application;

[0042] Figure 2 is an effect diagram of the oscillation time on the La / Al / CS hydrogel beads prepared in the present application for adsorbing phosphorus;

[0043] Figure 3 is an effect diagram of pH on the La / Al / CS hydrogel beads prepared in the present application for adsorbing phosphorus;

[0044] Figure 4is a coexisting ion pair effect diagram of the La / Al / CS hydrogel beads prepared in Example 1 of the present application on adsorption of phosphorus;

[0045] Figure 5 is a regeneration performance test diagram of the La / Al / CS hydrogel beads prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0046] The following examples are provided to better further understand the present application, and are not limited to the best mode, and do not constitute limitations on the content and protection scope of the present application, and any person under the inspiration of the present application or the combination of the present application with other prior art features, any product same or similar to the present application, falls within the protection scope of the present application.

[0047] The specific experimental steps or conditions not mentioned in the examples can be carried out according to the operation or conditions of the conventional experimental steps described in the literature in the art. The reagents or instruments not mentioned by the manufacturer are conventional reagent products that can be obtained by market purchase.

[0048] Example 1

[0049] The present embodiment provides a preparation method of harmless solid waste, and the process flow is as shown in Figure 1 The present embodiment provides a preparation method of harmless solid waste, and the process flow is as shown in

[0050] 1) 10g of lanthanum nitrate and 10g of aluminum chloride were weighed and dissolved in 100mL of deionized water to prepare a mixed solution, then stirred under a 40℃ water bath and slowly added with 100mL of 0.5mol / L sodium hydroxide solution, after the precipitation was completed, the temperature was raised to 80℃ and aged for 12h, centrifugal filtration was carried out, washed with deionized water, dried at 50℃, crushed and sieved through a 200 mesh sieve, to obtain La / Al composite material;

[0051] 2) The peanut shell was crushed and sieved through a 100 mesh sieve, then added to 100mL of 40g / L NaOH solution and stirred for 90min, then filtered and washed with water until neutral, dried in a 40℃ oven for 12h to obtain pretreated peanut shell, 10g of pretreated peanut shell was dissolved in 100mL of 1-allyl-3-methylimidazole chloride, then 1g of glutaraldehyde and 10g of La / Al material were added, stirred in a 100℃ water bath for 2h to prepare La / Al / CS hydrogel solution, finally the La / Al / CS hydrogel solution was added dropwise into water using a peristaltic pump, and placed at room temperature for 12h, then filtered, washed and freeze-dried to obtain La / Al / CS hydrogel beads;

[0052] 3) 100g of phosphogypsum was immersed in 500mL of oxalic acid with a concentration of 0.01mol / L, then stirred and mixed at 30℃ for 10min, and filtered to obtain filtrate one and residue one;

[0053] 4) The filter residue of step 3) is immersed in 500 mL of 0.01 mol / L NaOH solution, 5g of sodium persulfate is added, and then the mixture is stirred at 40°C for 10 min, filtered to obtain filter solution two and harmless solid waste;

[0054] 5) The filter solution one of step 3) is mixed with the filter solution two of step 4) to obtain a mixed filter solution with a pH of 6, 1wt% of La / Al / CS hydrogel beads of the mass of the mixed filter solution is added, and the mixture is stirred for 30 min, filtered to obtain La / Al / CS hydrogel beads adsorbed with phosphate;

[0055] 6) The La / Al / CS hydrogel beads adsorbed with phosphate are mixed with 1 mol / L sodium hydroxide solution, the mass ratio of the La / Al / CS hydrogel beads adsorbed with phosphate to the sodium hydroxide solution is 1:10, oscillation for 1 h, filtration, washing with deionized water, and the obtained La / Al / CS hydrogel beads are reused.

[0056] Example 2

[0057] The present embodiment provides a preparation method of harmless solid waste, and the process flow is as shown in Figure 1 The method comprises the following steps:

[0058] 1) 7.5g of lanthanum nitrate and 7.5g of aluminum chloride are weighed and dissolved in 100mL of deionized water to prepare a mixed solution, then stirred in a 40°C water bath and slowly added with 100mL of 0.5mol / L potassium hydroxide solution, after the precipitation is completed, the temperature is raised to 80°C for aging for 12h, centrifugal filtration is performed, washed with deionized water, dried at 50°C, crushed and sieved through a 200 mesh sieve to obtain La / Al composite material;

[0059] 2) The coconut shell is crushed and sieved through a 100 mesh sieve, then added to 100mL of 20g / L KOH solution and stirred for 90min, then filtered and washed with water until neutral, dried in a 40°C oven for 12h to obtain pretreated peanut shell, 10g of the pretreated peanut shell is dissolved in 100mL of 1-butyl-3-methylimidazolium chloride, then 1g of glutaraldehyde and 10g of La / Al material are added, and the mixture is stirred in a 100°C water bath for 2h to prepare a La / Al / CS hydrogel solution, finally the La / Al / CS hydrogel solution is added dropwise into water using a peristaltic pump, and the mixture is left to stand at room temperature for 12h, then filtered, washed, and freeze-dried to obtain La / Al / CS hydrogel beads;

[0060] 3) 100g of phosphogypsum is immersed in 500mL of 0.03mol / L citric acid, then stirred at 35°C for 20min, and filtered to obtain filter solution one and filter residue one;

[0061] 4) The filter residue of step 3) is immersed in 500 mL of 0.03 mol / L NaOH solution, 2 g of sodium persulfate is added, and then the mixture is stirred at 50°C for 20 min, filtered to obtain filter solution two and harmless solid waste;

[0062] 5) The filter solution one of step 3) is mixed with the filter solution two of step 4) to obtain a mixed filter solution with a pH of 8, 1 wt% of La / Al / CS hydrogel beads based on the mass of the mixed filter solution is added, and the mixture is stirred for 30 min, filtered to obtain La / Al / CS hydrogel beads adsorbed with phosphate;

[0063] 6) The La / Al / CS hydrogel beads adsorbed with phosphate are mixed with a 2 mol / L potassium hydroxide solution, the mass ratio of the La / Al / CS hydrogel beads adsorbed with phosphate to the sodium hydroxide solution is 1:10, oscillation is performed for 1 h, filtration is performed, and washing is performed with deionized water to obtain La / Al / CS hydrogel beads for repeated use.

[0064] Example 3

[0065] The present embodiment provides a preparation method of harmless solid waste, and the process flow is as shown in Figure 1 , which comprises the following steps:

[0066] 1) 5 g of lanthanum nitrate and 5 g of aluminum chloride are weighed and dissolved in 100 mL of deionized water to prepare a mixed solution, then the mixed solution is stirred in a 40°C water bath and 100 mL of 0.5 mol / L sodium carbonate solution is slowly added dropwise, after the precipitation is completed, the temperature is increased to 80°C and aged for 12 h, centrifugal filtration is performed, washing is performed with deionized water, drying is performed at 50°C, crushing is performed and sieving is performed through a 200 mesh sieve to obtain La / Al composite material;

[0067] 2) The sawdust is crushed and sieved through a 100 mesh sieve, then added to 100 mL of 50 g / L NaOH solution, stirred and reacted for 120 min, then filtered and washed with water until neutral, dried in a 40°C oven for 12 h to obtain pretreated peanut shell, 10 g of the pretreated peanut shell is dissolved in 100 mL of 1-allyl-3-methylimidazolium chloride, then 1 g of glutaraldehyde and 10 g of La / Al material are added, stirred in a 100°C water bath for 2 h to prepare La / Al / CS hydrogel solution, finally the La / Al / CS hydrogel solution is added dropwise to water using a peristaltic pump, placed at room temperature for 12 h, filtered, washed, and freeze-dried to obtain La / Al / CS hydrogel beads;

[0068] 3) 100 g of phosphogypsum is immersed in 500 mL of 0.05 mol / L oxalic acid, then the mixture is stirred at 40°C for 30 min, filtered to obtain filter solution one and filter residue one;

[0069] 4) The residue of step 3) was immersed in 500 mL of 0.05 mol / L KOH solution, 1 g of sodium persulfate was added, and then the mixture was stirred at 60°C for 30 min, filtered to obtain filtrate two and harmless solid waste;

[0070] 5) The filtrate one of step 3) was mixed with the filtrate two of step 4) to obtain a mixed filtrate with a pH of 10, 1 wt% of La / Al / CS hydrogel beads based on the mass of the mixed filtrate was added, and the mixture was stirred for 30 min, and then filtered to obtain La / Al / CS hydrogel beads adsorbed with phosphate;

[0071] 6) The La / Al / CS hydrogel beads adsorbed with phosphate were mixed with a 1 mol / L sodium hydroxide solution, the mass ratio of the La / Al / CS hydrogel beads adsorbed with phosphate to the sodium hydroxide solution was 1:10, and the mixture was oscillated for 1 h, filtered, and washed with deionized water to obtain La / Al / CS hydrogel beads for repeated use.

[0072] Comparative Example 1

[0073] The difference between this comparative example and Example 1 is that no alkali soaking treatment is performed, and other conditions are the same as those in Example 1.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 1 is that no acid soaking treatment is performed, and other conditions are the same as those in Example 1.

[0076] Comparative Example 3

[0077] The difference between this comparative example and Example 1 is that no persulfate salt is added, and other conditions are the same as those in Example 1.

[0078] Comparative Example 4

[0079] The difference between this comparative example and Example 1 is that the alkali soaking treatment and the oxidation treatment are performed separately, i.e., the oxidation treatment is not performed in the alkali solution, and other conditions are the same as those in Example 1.

[0080] Comparative Example 5

[0081] The difference between this comparative example and Example 1 is that the alkali soaking treatment and the oxidation treatment are performed separately, i.e., the oxidation treatment is not performed in the alkali solution, and other conditions are the same as those in Example 1.

[0082] Test Example 1

[0083] The detection method of total phosphorus in phosphogypsum adopts the potassium persulfate digestion method; the detection of soluble fluorine adopts the ion selective electrode method;

[0084] Table 1 Content of impurities in phosphogypsum

[0085] Total phosphorus (mg / L) Soluble fluorine (mg / L) Phosphogypsum 213.51 94.62 Example 1 0.45 0.94 Example 2 0.23 0.54 Example 3 0.02 0.16 Comparative Example 1 22.52 5.63 Comparative Example 2 33.61 6.32 Comparative Example 3 15.67 3.94 Comparative Example 4 22.73 7.94 Comparative Example 5 13.24 3.57

[0086] According to Table 1, the total phosphorus in the harmless solid waste prepared by the application is less than 0.5 mg / L, and the soluble fluorine is less than 10 mg / L, which meets the standard of the Standard for Pollution Control on Storage and Landfill of General Industrial Solid Waste (GB 18599-2020).

[0087] Test Example 2

[0088] A phosphate solution (200 mg / L) was prepared using KH2PO4 and deionized water, and the pH value was adjusted using sodium hydroxide and hydrochloric acid. 25 mL of the solution and 0.05 g of La / Al / CS adsorbent were added to a 50 mL centrifuge tube, and the oscillation time, pH, and the effect of other competitive anions on the adsorption of phosphate by the La / Al / CS hydrogel beads were measured at room temperature, respectively. The test results are shown in Tables 1-4. Figure 2 、 3 、4. The regeneration performance of the La / Al / CS adsorbent was measured using 1M sodium hydroxide as an eluent, and the test results are shown in Table 5. Figure 5 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 According to Tables 1-5, the phosphorus adsorption capacity of the La / Al / CS hydrogel beads prepared in Example 1 is close to the maximum phosphorus adsorption capacity when the oscillation time is 1 h, and the phosphorus adsorption capacity of the La / Al / CS hydrogel beads has a maximum value and stable effect in the pH range of 6-10, has high selective adsorption for phosphate, is less affected by other competitive anions, and has high regeneration performance. After 5 adsorption and desorption cycles, the adsorption capacity for phosphate can still reach 74.3% of the initial adsorption capacity.

[0089] Obviously, the above examples are only examples for clarity, and are not limitations on the embodiments. For ordinary skilled persons in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for preparing a solid waste which is innocuous, characterized by, The application relates to a harmless solid waste preparation method. The organic acid is oxalic acid or / and citric acid; 2. The production method according to claim 1, characterized by, The alkali is sodium hydroxide or / and potassium hydroxide; the concentration of the alkali is 0.01-0.05 mol / L; The persulfate is sodium persulfate or / and potassium persulfate. The temperature of the acid soaking treatment is 30-40 DEG C, and the time length is 10-30 min; 3. The production method according to claim 1 or 2, characterized by, The temperature of the alkali soaking treatment is 40-60 DEG C; and the time length is 10-30 min. The mass ratio of the phosphogypsum to the persulfate is (20-100):

1.

4. The production method according to any one of claims 1 to 3, characterized by, The pH of the mixed filtrate is 6-10; 5. The method of any one of claims 1-4, wherein, The mass ratio of the adsorbent to the mixed filtrate is 1:

100. The preparation process of the La / Al / CS hydrogel beads comprises the following steps: dissolving a lanthanum salt and an aluminum salt in a solvent to prepare a mixed solution, adding a precipitant to perform hydrothermal reaction to prepare a La / Al composite material, and finally performing embedding treatment by using an embedding agent.

6. The method of any one of claims 1-5, wherein, In the mixed solution, the concentration of the lanthanum salt is 50-100 g / L; and the concentration of the aluminum salt is 50-100 g / L; 7. The preparation method according to claim 6, characterized in that, The lanthanum salt is lanthanum nitrate; The aluminum salt is aluminum chloride; The solvent is water; The precipitant is an alkali; the concentration of the alkali is 0.5 mol / L; the alkali is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate; The volume ratio of the precipitant to the mixed solution is 1:1; The embedding agent is a natural high molecular material; the natural high molecular material is at least one of peanut shells, coconut shells, wood chips and straw; the natural high molecular material is pretreated natural cellulose; the pretreatment comprises the following steps: crushing and sieving the natural high molecular material, and then performing alkali soaking treatment; the alkali is at least one of sodium hydroxide and potassium hydroxide; the concentration of the alkali is 20-50 g / L; the alkali soaking time is greater than or equal to 90 min; and after the alkali soaking treatment, the natural high molecular material is further subjected to filtering, water washing and drying treatments. The temperature of the hydrothermal reaction is 80 DEG C, and the time length is 12 h.

8. The production method according to claim 6 or 7, characterized by, The La / Al / CS hydrogel beads are subjected to elution treatment by using an eluent after adsorbing phosphorus; 9. The method of any one of claims 6-8, wherein, The eluent is sodium hydroxide or / and potassium hydroxide; The concentration of the eluent is 1-2 mol / L; The mass ratio of the La / Al / CS hydrogel beads to the eluent is 1:10; The time length of the elution treatment is 1 h; After the elution treatment, the La / Al / CS hydrogel beads are further washed by using water. The harmless solid waste is prepared by using the harmless solid waste preparation method in any one of claims 1-9.

10. A solid waste material rendered innocuous, characterized in that, ​

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