Curing stabilizer for fluorine and heavy metals in ardealite and application of curing stabilizer

Abstract

The invention relates to the technical field of industrial solid waste recycling, in particular to a curing stabilizer for fluorine and heavy metal in ardealite and application of the curing stabilizer. The invention provides a curing stabilizer for fluorine and heavy metals in ardealite, the curing stabilizer comprises the following components: modified attapulgite, steel slag micropowder, charcoal, red mud, phosphorylated chitosan and a microbial agent, and the zeta potential of the modified attapulgite is 10-20 mV. According to the invention, the modified attapulgite, the steel slag micro powder, the charcoal, the red mud, the phosphorylated chitosan and the microbial agent are utilized for synergistic interaction to construct an inorganic-organic-microbial composite three-dimensional stabilized gelling framework, so that an efficient, stable and lasting curing effect is realized; particularly, heavy metals and fluorine elements in the ardealite can be effectively solidified and stabilized, and the compressive strength of the ardealite is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial solid waste resource utilization, and particularly relates to a stabilizer for fluorine and heavy metals in phosphogypsum and application thereof. BACKGROUND

[0002] Phosphogypsum is a by-product produced in the process of wet-process phosphoric acid production, and mainly contains dihydrate calcium sulfate (CaSO4·2H2O) and a small amount of impurities such as phosphorus, fluorine, heavy metals and organic matter. The acid leaching liquid of the phosphogypsum can pollute the surrounding water and soil.

[0003] At present, common treatment methods for the phosphogypsum include lime neutralization method, single clay mineral adsorption method and chemical reagent precipitation method, but these technologies still have the following limitations in practical application:

[0004] (1) It is difficult to balance the treatment efficiency and long-term stability: the lime neutralization method can quickly remove fluorides, but it can easily lead to a too high pH value, thereby causing the secondary dissolution or toxicity form conversion of some heavy metals, for example, As(III) can be oxidized to As(V) which is more toxic, and the single mineral adsorption material (such as zeolite and bentonite) has a limited inherent adsorption capacity, and the fixing efficiency of fluorides is usually low, and the modification treatment is needed to meet the actual demand.

[0005] (2) The synergistic removal effect of fluorine and heavy metals is poor: due to the difference in the form stability of different metal ions under different pH conditions, and the fluorine ions can form complexes or precipitates with metal ions, so it is difficult for a single treatment method to simultaneously and efficiently remove multiple pollutants, and the synergistic effect of multiple functional materials is needed to achieve the ideal removal effect and long-term stability.

[0006] (3) The application research of microbial technology is insufficient: in the field of industrial solid waste treatment, microorganisms have been applied to the biological conversion of heavy metals (such as the reduction of Cr(VI) to Cr(III) or as a coagulant), but the deep coupling mechanism of the microorganisms with inorganic materials and other industrial solid wastes still lacks systematic research, and the comprehensive performance in the synergistic treatment of multiple pollutants has not been fully utilized. SUMMARY

[0007] In order to solve the above problems, the present application provides a solidification stabilizer for fluorine and heavy metals in phosphogypsum and application thereof.

[0008] In a first aspect, the present application provides a solidification stabilizer for fluorine and heavy metals in phosphogypsum, which comprises the following components: modified attapulgite, steel slag powder, biochar, red mud, phosphatized chitosan and microbial inoculum, the zeta potential of the modified attapulgite is +10 to +20 mV, the specific surface area of the modified attapulgite is 150 to 180 m 2 / g.

[0009] In the present application, the zeta potential of the modified palygorskite is determined at 25 DEG C with 1 mmol / L KCl as the dispersion medium; and the specific surface area is determined by BET nitrogen adsorption method.

[0010] In some alternative embodiments, the content of the modified palygorskite is 30-35 wt%, the content of the steel slag micro-powder is 25-28 wt%, the content of the biochar is 5-10 wt%, the content of the red mud is 15-20 wt%, the content of the phosphorylated chitosan is 5-10 wt%, the added amount of the microbial agent in the solidification stabilizer is 3-8 wt%, and the effective viable bacterial count is ≥1x10 9 CFU / g;

[0011] The microbial agent comprises one or more than two combinations of Bacillus pasteurii, Bacillus licheniformis and Bacillus subtilis, the microbial agent culture temperature is 25 DEG C, the microbial agent can efficiently reduce Cr(VI) and produce a stable organic-inorganic hybrid structure, the reduction efficiency of Cr(VI) is ≥90%, and the microbial agent can metabolically produce beta-1, 3-glucan.

[0012] In some alternative embodiments, the content of calcium ferrite and calcium aluminosilicate in the steel slag micro-powder is 25-30 wt%, and the particle size of the steel slag micro-powder is 10-45 μm.

[0013] And / or, the specific surface area of the biochar is ≥300 m 2 / g, the pore volume is ≥0.25 cm 3 / g, and the surface carboxyl content is 0.8-1.2 mmol / g.

[0014] And / or, the content of sodium carbonate in the red mud is 1.2-2.5 wt%, the pH value is ≥10, and the particle size is ≤74 μm.

[0015] And / or, the pH value of the phosphorylated chitosan is 6.2-6.9.

[0016] It should be noted that the alkaline component of the red mud and the acidic group of the phosphorylated chitosan form a double pH buffer system, and the treatment environment pH is maintained at 7.2-7.8.

[0017] In some alternative embodiments, the preparation method of the modified palygorskite comprises the following steps:

[0018] S1, hydrolysis and activation of the amino silane coupling agent in an ethanol-water solution to obtain an amino silane coupling agent activation solution;

[0019] S2, adding attapulgite into the amino silane coupling agent activation solution obtained in S1, and performing coupling reaction under heating and stirring to obtain the modified attapulgite.

[0020] Optionally, in S1, the volume percentage of the amino silane coupling agent in the amino silane coupling agent activation solution is 1-5%;

[0021] Optionally, the pH value of the amino silane coupling agent activation solution is 4.0-5.0.

[0022] Optionally, the temperature of the hydrolysis activation is 25-30℃, and the time of the hydrolysis activation is 25-40 min.

[0023] Optionally, the amino silane coupling agent comprises one or more of 3-aminopropylmethyldiethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and aminopropyltriethoxysilane, preferably 3-aminopropylmethyldiethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0024] Optionally, the volume fraction of ethanol in the ethanol-water solution is 90-100%.

[0025] Optionally, in S2, the solid-liquid ratio of the attapulgite to the amino silane coupling agent activation solution is 1g:(5-20)mL.

[0026] Optionally, the stirring speed is 200-300 rpm.

[0027] Optionally, the temperature of the coupling reaction is 55-65℃, and the time of the coupling reaction is 1-3h.

[0028] It should be noted that S2 further comprises a step of pretreating the attapulgite, wherein the pretreatment comprises washing the attapulgite in deionized water for 3-5 times, drying at 80-105℃ until constant weight, and then grinding; the particle size of the pretreated attapulgite is 75-150μm.

[0029] In some optional embodiments, the method further comprises a step of post-treating the modified attapulgite, wherein the post-treatment comprises solid-liquid separation, washing, and vacuum drying at 65-85℃ for 24-48h.

[0030] In the second aspect, the application provides a method for stabilizing fluorine and heavy metals in phosphogypsum simultaneously by using the curing agent.

[0031] In some optional embodiments, the method comprises the following steps:

[0032] (1) mixing modified attapulgite, steel slag micro-powder, biochar, red mud, phosphatized chitosan and microbial inoculant to prepare a solidification stabilizer;

[0033] (2) mixing phosphogypsum with the solidification stabilizer;

[0034] (3) curing at normal temperature (20-35℃) for a curing period of ≥48h to realize the simultaneous solidification of heavy metals and fluorine in the phosphogypsum.

[0035] Optionally, the mass ratio of the phosphogypsum to the stabilizer is 100:(5-6);

[0036] Optionally, the pH of the slurry after mixing the solidification stabilizer with the phosphogypsum is 7.2-7.8;

[0037] Optionally, after removing the surface soluble impurities of the phosphogypsum by water washing, the phosphogypsum is dried at 60-80℃ until the water content is ≤5%, and then crushed to a particle size of ≤1mm to ensure full reaction with the solidification stabilizer and improve the solidification effect.

[0038] The technical scheme of the present application has the following advantages:

[0039] 1. The present application provides a solidification stabilizer for fluorine and heavy metals in phosphogypsum, which comprises the following components: modified attapulgite, steel slag micro-powder, biochar, red mud, phosphatized chitosan and microbial inoculant, wherein the zeta potential of the modified attapulgite is +10-+20mV, and the specific surface area of the modified attapulgite is 150-180m 2 / g. The present application uses modified attapulgite, steel slag micro-powder, biochar, red mud, phosphatized chitosan and microbial inoculant for synergistic effect, to construct an inorganic-organic-microbial composite three-dimensional stable gelation framework, to achieve high efficiency, stability and durability, especially to effectively stabilize the heavy metals and fluorine elements in the phosphogypsum. The stabilized phosphogypsum has good stability and high compressive strength. In the present application, the modified attapulgite with a zeta potential of 10-20mV can effectively adsorb fluorine, while avoiding space steric hindrance or non-specific adsorption caused by excessive charge, and taking into account the heavy metal adsorption effect. Meanwhile, the modified attapulgite with a zeta potential of 10-20mV can promote the firm adhesion of microorganisms and the formation of biofilm, avoid damage to microorganisms or inhibition of enzyme activity caused by excessive action, and improve the mineralization efficiency. Red mud and phosphatized chitosan can form a double pH buffer system, which can stabilize and maintain the pH in the system at 7.2-7.8, which is not only conducive to the precipitation of heavy metals in the phosphogypsum, but also provides growth conditions for the growth and metabolism of microbial inoculants and enzyme activity. The metabolic activity of microbial inoculants can induce the combination of calcium ions and carbonate ions in the environment to form calcium carbonate precipitate. This biological induced mineralization can precipitate heavy metal ions (such as Cd 2+) in the form of co-precipitation or coating in a stable mineral lattice, and can affect the occurrence of fluoride ions, and convert them into more difficultly soluble compounds. Compared with physical adsorption and chemical precipitation, the mineral phase formed by biomineralization has lower solubility and higher environmental stability, which is the fundamental guarantee for long-term stabilization of pollutants. At the same time, the microbial agent can further improve the stability of fluorine elements through co-precipitation or adsorption coating mechanism. In addition, the specific surface area of the modified attapulgite is greater than or equal to 150 m 2 / g, which is a necessary condition for efficient fluorine fixation and stabilization. If the specific surface area is insufficient, the number of effective adsorption sites is limited, making it difficult to construct a continuous porous framework with steel slag powder and biochar, resulting in a significant decrease in fluoride ion removal rate and heavy metal solidification rate. At the same time, a larger specific surface area provides more interfaces for microbial colonization and biomineralization, which helps to form a stable organic-inorganic hybrid layer. Therefore, this specific surface area is not arbitrarily selected, but is a key technical feature for achieving the synergistic solidification and long-term stabilization effect of the present application.

[0040] 2. The present application provides a kind of solidification stabilizer of fluorine and heavy metal in phosphogypsum, and the microbial agent includes at least one of Bacillus pasteurii, Bacillus licheniformis and Bacillus subtilis. The microbial agent of the present application can make full use of the function of biomineralization to realize the stability of fluorine and heavy metal in phosphogypsum.

[0041] 3. The present application provides a kind of solidification stabilizer of fluorine and heavy metal in phosphogypsum, and the modified attapulgite is obtained by modifying with amino silane coupling agent. The present application modifies the zeta potential of attapulgite from negative potential to positive potential by using amino silane coupling agent. By specific limitation of amino silane coupling agent, the adhesion performance of microorganism can also be improved, and the stability of fluorine and heavy metal in phosphogypsum is further improved. The present application aims to build a carrier interface that is extremely friendly to microbial agent, so as to maximize the synergistic stabilization effect of "inorganic-organic-microorganism". It is not only to change the surface potential of attapulgite from negative to positive, but also to actively build a microenvironment that is extremely friendly to microorganism. This optimized interface greatly promotes the colonization of subsequent microorganism, biofilm formation and efficient biomineralization, and is one of the key technical guarantees for realizing the "three-dimensional stabilization framework and microbial mineralization synergistic effect" of the present application.

[0042] 4.The present application provides a kind of fluorine and heavy metal solidification stabilizer in phosphogypsum, the preparation method of the modified palygorskite includes the following steps: S1, amino silane coupling agent is hydrolyzed and activated in ethanol solution, to obtain amino silane coupling agent activation solution;S2, palygorskite is added to the amino silane coupling agent activation solution obtained in S1, and coupling reaction is carried out under the condition of heating and stirring, to obtain the modified palygorskite.The present application utilizes amino silane coupling agent solution to modify palygorskite, and the zeta potential of the modified palygorskite is controlled at 10-20 mV, and the preparation method of the modified palygorskite provided by the present application can effectively retain the specific surface area of palygorskite, provide more active sites to adsorb pollutants, and provide sufficient adhesion space for microorganisms, ensuring the synergistic optimization of adsorption capacity and zeta potential control, thereby realizing the significant improvement of overall technical effect. DETAILED DESCRIPTION

[0043] The following examples are provided to better further understand the present application, and are not limited to the best mode, and do not limit 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 obtains any product same or similar to the present application, which belongs to the protection scope of the present application.

[0044] (1) The present application uses HJ299-2007 "Solid waste leaching toxicity leaching method-sulfuric acid and nitric acid method" to leach the stabilized samples obtained in the present application.

[0045] Among them, the concentration of F in the leaching solution is determined by HJ84-2016 "Determination of inorganic anions (F - , Cl - , NO2 - , Br - , NO3 - , PO4 3- , SO3 2- , SO4 2- ) ion chromatography method";

[0046] The concentration of Cd in the leaching solution is determined by HJ776-2015 "Determination of 32 elements in water by inductively coupled plasma atomic emission spectrometry".

[0047] (2) The calculation method of the stabilization rate (%):

[0048] Stabilization rate (%) = [1-(C leach ×L / S×D) / C total ]×100

[0049] Among them, C leach : the concentration of target substance in leaching solution (mg / L).

[0050] L / S: liquid to solid ratio after extraction (recommended 20L / kg according to standard);

[0051] D: dilution factor (1 if none);

[0052] C total : total sample measured value (mg·kg-1, the sample was digested and measured according to the microwave digestion method in HJ766-2015 "Determination of metal elements in solid waste by inductively coupled plasma mass spectrometry").

[0053] (3) 28d curing stable sample compressive strength MPa

[0054] Place the sample flat in the center of the pressure plate, the loading speed is preferably 2-6kN / s (4kN / s in this example), press until the test block is destroyed, and record the maximum breaking load P.

[0055] Compressive strength R P The calculation formula is as follows:

[0056]

[0057] Wherein, R P - compressive strength, MPa;

[0058] P - maximum breaking load, N;

[0059] L - length of the pressure surface, mm;

[0060] B - width of the pressure surface, mm.

[0061] (4) Microbial agent

[0062] The microbial agent used in this application is a composite microbial agent with Sporosarcina pasteurii (preserved number CGMCC 1.3687, China General Microbiological Culture Collection Center) as the dominant bacteria, prepared into a powder form by freeze-drying process, preferably with a spore rate of ≥80%, and the effective viable bacterial count is not less than 1×10 9 CFU / g (plate counting method: nutrient agar, 10 -5 -10 -7 Gradient dilution, 0.1mL / plate, 37℃, 24-48h counting). Under the preferred conditions, the spore rate of the microbial agent is ≥80%, to ensure its survival and mineralization in the stabilizer system.

[0063] The microbial agent can be obtained from the China General Microbiological Culture Collection Center, or the commercial freeze-dried powder of equivalent source; the incoming inspection conforms to the above technical indicators, which can be replaced, not limited to specific manufacturers / models.

[0064] Unless otherwise indicated, the experimental procedures or conditions in the examples were carried out according to conventional experimental procedures described in the literature. Unless otherwise indicated, the reagents or instruments used were conventional reagent products available on the market.

[0065] Preparation Example 1

[0066] The present preparation example provides a method for preparing modified attapulgite, and the specific steps are as follows:

[0067] (1) Pretreatment of attapulgite

[0068] Select 150 mesh natural attapulgite (specific surface area 135 m 2 / g) and wash it 4 times in deionized water to remove water-soluble impurities and trace mineral dust in the attapulgite. Dry the washed attapulgite in an oven at 105°C to a constant weight, and grind it to pass through a 150 mesh sieve to obtain pretreated attapulgite, which activates the surface hydroxyl groups of the attapulgite and increases the active sites for subsequent coupling reactions.

[0069] (2) Preparation of amino silane coupling agent solution

[0070] Mix ethanol and deionized water in a volume ratio of 9:1 to form a solvent, and mix 3-aminopropylmethyldiethoxysilane (APMDES) into the solvent in a final volume ratio of 2%, and hydrolyze and activate at 27°C for 30 min. Adjust the pH of the amino silane coupling agent solution to 5.0 using dilute acetic acid to form an amino silane coupling agent solution, which promotes the moderate hydrolysis of the silane coupling agent and forms active silanol.

[0071] (3) Surface coupling reaction

[0072] According to the (solid-liquid ratio of 1g:10mL) of pretreated attapulgite and amino silane coupling agent solution, add the pretreated attapulgite to the amino silane coupling agent solution, and stir at 200 rpm at 60°C for 2h to form modified attapulgite;

[0073] Centrifuge the modified attapulgite at 4000 rpm for 10 min. Wash the obtained solid product with deionized water 3 times and then with anhydrous ethanol 1 time to remove unreacted coupling agent and by-products. Dry the washed solid product in a vacuum oven at 80°C for 24h, grind it to pass through a 150 mesh sieve, and obtain amino-modified attapulgite.

[0074] The zeta potential of the amino-modified attapulgite prepared in the present preparation example was detected by a zeta potential analyzer to be 15.2 mV, and the specific surface area was 155 m 2 / g.

[0075] Preparation Example 2

[0076] The present preparation example provides a preparation method of modified attapulgite, and the specific steps are as follows:

[0077] (1) Pretreatment of attapulgite

[0078] Select 200 mesh natural attapulgite (specific surface area is 165 m 2 / g), wash 3 times in deionized water, and the selected steps are the same as those in Preparation Example 1.

[0079] (2) Preparation of amino silane coupling agent solution

[0080] According to the volume ratio of ethanol to deionized water of 9:1 to form the solvent, and according to the final volume ratio of 5%, APMDES is mixed into the solvent, and hydrolysis activation is carried out at 27°C for 30 min, and the pH value of the solution is adjusted to 4.5 using dilute acetic acid.

[0081] (3) Surface coupling reaction

[0082] According to (the solid-liquid ratio is 1 g:20 mL), the pretreated attapulgite is added into the coupling agent solution, and the reaction is carried out at 58°C with continuous stirring at a speed of 300 rpm for 1 h. The subsequent selected steps are the same as those in Preparation Example 1. The zeta potential of the amino-modified attapulgite prepared in the present preparation example is 20.0 mV, and the specific surface area is 178 m 2 / g.

[0083] Preparation Example 3

[0084] The present preparation example provides a preparation method of modified attapulgite, and the specific step parameters are the same as those in Preparation Example 1, except that an equal volume of N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane (DAMO) is used to replace APMDES in step (2).

[0085] The zeta potential of the amino-modified attapulgite prepared in the present preparation example is 14.5 mV, and the specific surface area is 152 m 2 / g.

[0086] Preparation Example 4

[0087] The present preparation example provides a preparation method of modified attapulgite, and the specific step parameters are the same as those in Preparation Example 1, except that an equal volume of γ-aminopropyl triethoxysilane (APTES) is used to replace APMDES in step (2).

[0088] The zeta potential of the amino-modified attapulgite prepared in the present preparation example is 9.2 mV, and the specific surface area is 142 m2 / g.

[0089] Example 1

[0090] The present example provides a stabilizer and its application, which are as follows:

[0091] (1) Raw material preparation and pretreatment

[0092] Modified palygorskite: The amino-modified palygorskite (zeta potential of 15.2 mV, specific surface area of 155 m 2 / g) prepared in Preparation Example 1 was used.

[0093] Other stabilizer components: Steel slag powder (particle size of 10-45 μm, CaFe2O4and Ca2Al2SiO7combined accounted for 30%), biochar (specific surface area of 300 m 2 / g, pore volume of 0.25 cm 3 / g, surface carboxyl content of 1.0 mmol / g), red mud (particle size < 74 μm, sodium carbonate content of 2.0 wt%, pH value of 10), phosphated chitosan (pH value of 6.2). Each of the above components was dried in an oven at 60°C for 4 h to constant weight before use.

[0094] Microbial agent: The microbial agent was a commercially available compound Bacillus pasteurii powder, with an effective viable bacterial count of not less than 1×10 9 CFU / g (plate counting method).

[0095] Material to be treated: Phosphogypsum from a phosphorus chemical enterprise, with heavy metal Cd content of 85 mg / kg and F content of 2.3 wt%.

[0096] (2) Stabilizer preparation and stabilized sample molding

[0097] 350 g of amino-modified palygorskite, 250 g of steel slag powder, 100 g of biochar, 150 g of red mud, and 100 g of phosphated chitosan were weighed by mass and placed in a blender for dry mixing at a speed of 300 rpm for 15 min to obtain a premix. Then, 50 g of microbial agent was added, and the stirring was continued at a speed of 200 rpm for 5 min to finally obtain a stabilizer for fluorine and heavy metals in phosphogypsum.

[0098] 1000 g of phosphogypsum was taken, and 60 g of the above stabilizer (stabilizer to phosphogypsum mass ratio of 100:6) was added and mechanically mixed uniformly. Deionized water was slowly added and continuously stirred to make the final moisture content of the mixture reach 20%. The uniformly mixed slurry was filled into a test mold and pressed to form a sample (80 mm×38 mm×18 mm) under a load of 30 KN. After demolding, the sample was placed in a standard curing box with a temperature of 25°C and a relative humidity of 95% for curing to the specified age.

[0099] (3) Performance test results

[0100] Compressive strength after 28 days of curing: 12.5 MPa;

[0101] Leaching toxicity after 28 days of curing: Cd leaching concentration is 0.08 mg / L; F leaching concentration is 4.2 mg / L; the stabilization rates are Cd 95%, F 98%, respectively.

[0102] Example 2

[0103] The present example provides a stabilizer and its application, which are as follows:

[0104] (1) Raw material preparation and pretreatment

[0105] Modified attapulgite: the amino-modified attapulgite prepared in Preparation Example 2, with the key parameters of zeta potential of 20 mV, specific surface area of 178 m2 / g. 2

[0106] Other stabilizer components and materials to be treated: all other raw materials, including steel slag powder, biochar, red mud, phosphatized chitosan, microbial inoculum, and phosphogypsum to be treated, are exactly the same as in Example 1 in terms of type, specification, and pretreatment method.

[0107] (2) Stabilizer preparation and stabilized sample molding

[0108] The same stabilizer formulation and preparation process as in Example 1 are used. 350 g of the amino-modified attapulgite of the present example, 250 g of steel slag powder, 100 g of biochar, 150 g of red mud, 100 g of phosphatized chitosan, and 50 g of microbial inoculum are weighed by mass, and the final stabilizer for fluorine and heavy metals in phosphogypsum is prepared according to the method described in Example 1.

[0109] The subsequent stabilized sample molding and curing process, including the ratio of phosphogypsum (100:6), water addition, compression molding, and standard curing, are exactly the same as the steps (2) of Example 1.

[0110] (3) Performance test results

[0111] The stabilized samples prepared in the present example are tested, and the results are as follows:

[0112] Compressive strength after 28 days of curing: 12.1 MPa;

[0113] Leaching toxicity after 28 days of curing: Cd leaching concentration is 0.09 mg / L; F leaching concentration is 4.4 mg / L; the stabilization rates are Cd 96%, F 99%, respectively.

[0114] ​Result analysis: the modified attapulgite in this example is prepared under the upper limit of process parameters (such as coupling agent concentration, solid-liquid ratio), and its zeta potential is at the upper limit of the range required by the application (+10~+20mV). The test results show that the final stable sample still performs excellently in mechanical properties and pollutant stabilization effect, fully proving that the process range claimed in the application is reasonable and effective.

[0115] Example 3

[0116] This example provides a stabilizer and its application, as follows:

[0117] (1) Raw material preparation and pretreatment

[0118] Except that the modified attapulgite is the sample prepared in Preparation Example 3 (zeta potential 14.5mV, specific surface area 152m 2 / g), the types, specifications and pretreatment methods of all other raw materials are exactly the same as in Example 1.

[0119] (2) Stabilizer preparation and stable sample molding

[0120] The proportions of all components, preparation process, sample molding and curing conditions are exactly the same as in Example 1.

[0121] (3) Performance test results

[0122] Compressive strength after 28 days of curing: 13.1MPa;

[0123] Leaching toxicity after 28 days of curing: Cd leaching concentration is 0.07mg / L; F leaching concentration is 3.9mg / L; the stabilization rates are Cd 97%, F 98% respectively.

[0124] Result analysis: the attapulgite modified by DAMO is more conducive to microbial colonization due to its moderate zeta potential, making the post-strength and pollutant stabilization effect of the stable body slightly better than in Example 1, proving that it is also a preferred technical solution of the application.

[0125] Comparative Example 1

[0126] This comparative example provides a stabilizer and its application, as follows:

[0127] (1) Raw material preparation and pretreatment

[0128] Modified attapulgite: APTES amino-modified attapulgite prepared in Preparation Example 4 (zeta potential 9.2mV, specific surface area 142m 2 / g).

[0129] Other stabilizer components and materials to be treated: All other raw materials, including steel slag micro-powder, biochar, red mud, phosphatized chitosan, microbial inoculants, and the phosphogypsum to be treated, are of the same types, specifications, and pretreatment methods as in Example 1.

[0130] (2) Stabilizer preparation and stabilized sample formation

[0131] The same stabilizer formulation, preparation process, sample formation, and curing conditions as in Example 1 were used.

[0132] (3) Performance test results

[0133] The stabilized sample prepared in this comparative example was tested, and the results are as follows:

[0134] Compressive strength after 28 days of curing: 9.2 MPa;

[0135] Leaching toxicity after 28 days of curing: Cd leaching concentration was 0.25 mg / L; F leaching concentration was 8.1 mg / L; the stabilization rates were Cd 72% and F 75%, respectively.

[0136] (4) Result analysis

[0137] Compared with Example 1 (compressive strength 12.5 MPa, Cd leaching 0.08 mg / L, F leaching 4.2 mg / L) and Example 2 (compressive strength 13.1 MPa, Cd leaching 0.07 mg / L, F leaching 3.9 mg / L), the results of this comparative example show that the compressive strength is reduced by about 26%, the Cd leaching concentration is about 2-3 times higher, and the F leaching concentration is nearly 1 time higher.

[0138] Comparative Example 2

[0139] This comparative example provides a stabilizer and its application, as follows:

[0140] (1) Raw material preparation and pretreatment

[0141] The only difference between this comparative example and Example 1 is that the natural attapulgite (zeta potential -10 mV) without any modification by amino silane coupling agent is used instead of the amino-modified attapulgite in Example 1. The types, specifications, and pretreatment methods of all other raw materials are the same as in Example 1.

[0142] (2) Stabilizer preparation and stabilized sample formation

[0143] The proportions of all components (including the amount of attapulgite still being 350 g), the preparation process, sample formation, and curing conditions are the same as in Example 1.

[0144] (3) Performance test results

[0145] Compressive strength after 28 days of curing: 7.5 MPa;

[0146] Leaching toxicity after 28 days of curing: Cd leaching concentration is 0.52 mg / L; F leaching concentration is 15.8 mg / L; the stability rates are Cd 65%, F 70%, respectively.

[0147] Result analysis: Since the unmodified attapulgite surface is negatively charged, it cannot effectively adsorb F through electrostatic attraction, and it is not conducive to the attachment of microorganisms with a negative surface, resulting in a significant weakening of biomineralization. Therefore, the mechanical strength and the stability effect on pollutants of the stabilizer are much worse than those of Example 1, which fully proves that the amino modification of attapulgite in the present application is one of the necessary technical steps to achieve the technical effects of the present application.

[0148] Comparative Example 3

[0149] This comparative example provides a preparation method of a stabilizer for fluorine and heavy metals in phosphogypsum, and the components and preparation steps thereof are completely the same as those of Example 1 except that red mud is not added. The specific ratio is: modified attapulgite 350 g, steel slag powder 250 g, biochar 100 g, phosphated chitosan 100 g, and microbial agent 50 g. The above components are first dry mixed, then water is added to a moisture content of 20%, and then wet mixing is uniformly carried out to form a molding, which is cured in a standard curing box with a temperature of 25°C and a relative humidity of 95% for 28 days.

[0150] Compressive strength after 28 days of curing: 9.8 MPa; Cd leaching concentration is 0.18 mg / L; F leaching concentration is 6.5 mg / L; the stability rates are Cd 79%, F 74%, respectively.

[0151] The results show that the absence of red mud will weaken the alkaline pH adjustment ability in the phosphogypsum system, destroy the "double pH buffer system" with phosphated chitosan, and lead to a decrease in microbial activity and a decrease in pollutant complex precipitation efficiency.

[0152] Comparative Example 4

[0153] This comparative example is the same as Example 1, but no phosphated chitosan is added. The specific ratio is: modified attapulgite 350 g, steel slag powder 250 g, biochar 100 g, red mud 150 g, and microbial agent 50 g. The remaining operation steps are consistent.

[0154] Compressive strength after 28 days of curing: 9.1 MPa; Cd leaching concentration is 0.20 mg / L; F leaching concentration is 7.2 mg / L; the stability rates are Cd 76%, F 69%, respectively.

[0155] The results show that the lack of phosphorylated chitosan can cause the imbalance of the "dual pH buffer system", poor pH stability of the treatment system, which affects the metal ion precipitation conditions and the optimal growth interval of microorganisms, resulting in the decline of the overall stability effect.

[0156] Comparative Example 5

[0157] The present comparative example is the same as Example 1, but no microbial inoculant is added. The component ratio is: modified attapulgite 350 g, steel slag micro-powder 250 g, biochar 100 g, red mud 150 g, and phosphorylated chitosan 100 g. The operation steps and curing conditions remain unchanged.

[0158] After 28 days of curing, the compressive strength is 10.0 MPa; the Cd leaching concentration is 0.23 mg / L; the F leaching concentration is 8.9 mg / L; and the stability rates are Cd 72% and F 61%, respectively.

[0159] It can be seen that, after the absence of microbial inoculant, although the initial physical adsorption and inorganic gelation still exist, the lack of the later biological induced mineralization process leads to a significant decline in long-term stability of pollutants.

[0160] Comparative Example 6

[0161] In order to further verify the necessity of the multi-component synergistic effect of the present application, only steel slag micro-powder is used as the stabilizer component in the present comparative example. 100 g of steel slag micro-powder is weighed by mass, mixed with 1000 g of phosphogypsum (mass ratio 100:10), water is added to a moisture content of 20%, and the pressing and curing conditions are consistent with Example 1.

[0162] After 28 days of curing, the compressive strength is 8.7 MPa; the Cd leaching concentration is 0.30 mg / L; the F leaching concentration is 9.5 mg / L; and the stability rates are Cd 65% and F 59%, respectively.

[0163] The results show that, in the absence of modified attapulgite, biochar, red mud, phosphorylated chitosan, and microbial inoculant, the use of steel slag alone is obviously insufficient in stability effect, and cannot meet the simultaneous stabilization demand of multiple pollutants in phosphogypsum.

[0164] Table 1 Determination of related properties in phosphogypsum after treatment

[0165]

[0166] The embodiment 1 of the present application shows excellent compressive strength and extremely low Cd and F leaching concentration, and the heavy metal and fluorine stability rates are more than 95% and more than 98% respectively, which fully verifies the synchronous, efficient and long-acting ability of the inorganic-organic-microorganism synergistic three-dimensional stabilization framework constructed by the present application to the pollutants in phosphogypsum, wherein the stability rate is a retention rate index based on the total amount, and is not a relative reduction rate of the control sample.

[0167] The comparative example 1 and the comparative example 2 respectively use the attapulgite with a zeta potential less than 10 mV and the unmodified attapulgite as a control, and the results show that the compressive strength is significantly decreased, the leaching concentration of Cd and F is increased, and the stability rate is decreased, which indicates that the adsorption capacity of anion F is seriously weakened and the attachment and mineralization process of microorganisms are affected when the potential range defined in the present application is not reached +10~+20 mV. Further, through the setting of the comparative examples 3~6, it is verified that each component plays an irreplaceable role in the synergistic system: the comparative example 3 lacks bauxite, which leads to lack of alkaline buffer in the system, affects the pH stability and microbial activity, and reduces the F stability rate; the comparative example 4 lacks phosphated chitosan, lacks double buffer regulation, the pH fluctuation is intensified, which leads to the decrease of Cd and F stability rate; the comparative example 5 lacks microbial inoculant, although the adsorption is effective in the early stage, but lacks the later biological mineralization, which reduces the Cd and F stability rate; the comparative example 6 only uses steel slag powder, lacks three-dimensional framework and mineralization regulation ability, and has the worst comprehensive performance, and the F stability rate is only 59%, which does not have industrial application feasibility.

[0168] In summary, the modified attapulgite with a zeta potential controlled in +10~+20 mV, steel slag powder, biochar, bauxite, phosphated chitosan and microbial inoculant are used in scientific proportion and synergistically to construct a stabilization system which integrates physical adsorption, chemical complexation, pH buffer and biological mineralization. The lack of any core component will destroy the stability of the system, which leads to a significant decrease in the stability rate, which fully proves that the present application has outstanding technical effects and creativity in material combination, parameter optimization and synergistic mechanism.

[0169] Obviously, the above embodiments are only examples for clearly illustrating, but not limiting the embodiments. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and cannot be listed. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A solidification stabilizer for fluorine and heavy metals in phosphogypsum, characterized by, The application relates to a composite material for soil improvement, which comprises the following components: modified palygorskite, steel slag micro-powder, biochar, red mud, phosphatized chitosan and microbial inoculum, wherein the zeta potential of the modified palygorskite is +10 to +20 mV; the specific surface area of the modified palygorskite is 150 to 180 m 2 / g.

2. The cure stabilizer according to claim 1, wherein The content of the modified palygorskite is 30-35wt%, the content of the steel slag powder is 25-28wt%, the content of the biochar is 5-10wt%, the content of the red mud is 15-20wt%, and the content of the phosphatized chitosan is 5-10wt%; The adding amount of the microbial agent in the solidification stabilizer is 3-8wt%, and the effective viable cell number in the microbial agent is ≥1×10 9 CFU / g; And / or, the microbial agent comprises one or more than two combinations of Bacillus pasteurii, Bacillus licheniformis and Bacillus subtilis.

3. The cure stabilizer according to claim 1, wherein The total content of calcium ferrite and calcium aluminum silicate in the steel slag powder is 25-30wt%, and the particle size of the steel slag powder is 10-45μm; and / or, the biochar has a specific surface area of > 300 m 2 / g, a pore volume of > 0.25 cm 3 / g, a surface carboxyl content of 0.8-1.2 mmol / g.

4. The cure stabilizer according to claim 1, wherein The content of sodium carbonate in the red mud is 1.2-2.5wt%, the pH value is ≥10, and the particle size is ≤74μm; And / or, the pH value of the phosphatized chitosan is 6.2-6.

9.

5. The solidification stabilizer of any one of claims 1-4, wherein, The preparation method of the modified palygorskite comprises the following steps: S1, hydrolysis and activation of amino silane coupling agent in ethanol-water solution to obtain amino silane coupling agent activation solution; S2, coupling reaction of palygorskite in the amino silane coupling agent activation solution obtained in S1 under heating and stirring to obtain the modified palygorskite.

6. The cure stabilizer according to claim 5, wherein In S1, the volume percentage of amino silane coupling agent in the amino silane coupling agent activation solution is 1-5%; And / or, the pH value of the amino silane coupling agent activation solution is 4.0-5.0; And / or, the temperature of hydrolysis and activation is 25-30℃, and the time of hydrolysis and activation is 25-40min; And / or, the amino silane coupling agent comprises at least one of 3-aminopropylmethyldiethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and aminopropyltriethoxysilane, preferably 3-aminopropylmethyldiethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane; And / or, the volume fraction of ethanol in the ethanol-water solution is 90-100%.

7. The cure stabilizer according to claim 5, wherein In S2, the solid-liquid ratio of palygorskite to amino silane coupling agent activation solution is 1g:(5-20)mL; And / or, the stirring speed is 200-300rpm; And / or, the temperature of the coupling reaction is 55-65℃, and the time of the coupling reaction is 1-3h.

8. The cure stabilizer according to claim 5, wherein In S2, the palygorskite further comprises a pretreatment step, which comprises washing 3-5 times in deionized water and drying to constant weight at 80-105℃ before grinding; the particle size of the pretreated palygorskite is 75-150μm; And / or, in S2, the modified palygorskite further comprises a post-treatment step, which comprises solid-liquid separation, washing, and vacuum drying at 65-85℃ for 24-48h.

9. A method for simultaneous stabilization of fluorine and heavy metals in phosphogypsum by the solidified stabilizer according to any one of claims 1 to 8, characterized in that, Comprise the following steps: First, mix the modified palygorskite, steel slag powder, biochar, red mud, phosphatized chitosan and microbial agent to prepare a solidification stabilizer; then mix the phosphogypsum with the prepared solidification stabilizer and cure.

10. The method of claim 9, wherein, The mass ratio of the phosphogypsum to the stabilizer is 100:(5-6); And / or, the pH value of the slurry after mixing the solidification stabilizer with the phosphogypsum is 7.2-7.8; And / or, the temperature of the curing is 20-35 DEG C, and the curing period is greater than or equal to 48 hours. And / or, the phosphogypsum is dried at 60-80 DEG C to a moisture content of less than or equal to 5% after water washing to remove surface soluble impurities, and then crushed to a particle size of less than or equal to 1 mm.

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