Iron modified woody peat humus composition and application thereof in synchronous passivation of cadmium and arsenic in soil
By utilizing the porous structure of composite iron modifier and zeolite, as well as the action of microorganisms, in an acidic environment, the problem of easy precipitation of iron modifier in acidic environment was solved, and stable fixation and efficient passivation of cadmium and arsenic were achieved.
Patent Information
- Application Number
- CN202510966338.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-14
- Publication Date
- 2025-11-07
AI Technical Summary
In acidic environments, iron modifiers are prone to precipitate, reducing their complexation efficiency with humic acid and thus affecting the passivation effect on heavy metals such as cadmium and arsenic.
An iron-modified woody peat humus composition was used, including woody peat, a composite iron modifier, ammonium sulfate, potassium dihydrogen phosphate, and microbial fermentation broth. After the ferrous sulfate reacted with sodium dithionite, it was mixed with pretreated zeolite to form a stable organic-inorganic complex, which fixed Cd2+ and As(V). The passivation effect of cadmium and arsenic was enhanced by the porous structure of zeolite and the action of microorganisms.
In an acidic environment, it ensures the stable release and efficient utilization of iron ions, strongly fixes Cd2+, enhances the adsorption of As(V), achieves simultaneous and efficient passivation of cadmium and arsenic, and reduces the risk of heavy metal migration.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of woody peat humic substance composition, in particular to iron modified woody peat humic substance composition and its application in synchronous passivation of cadmium and arsenic in soil. BACKGROUND
[0002] Woody peat humic substance has a wide application prospect in the fields of environmental remediation (such as water purification and heavy metal removal), soil improvement, and agricultural application (such as water and fertilizer retention agent and plant growth regulator) due to its unique structural characteristics, such as rich aromatic ring, carboxyl, phenolic hydroxyl, carbonyl and other functional groups, which exhibit excellent adsorption performance, ion exchange capacity and cation exchange capacity (CEC); however, although natural woody peat contains a certain amount of iron, it usually exists in amorphous or structural combination state, with low content and uneven distribution, resulting in low redox potential and limited adsorption and reduction / oxidation capacity for some pollutants (such as Cd and As).
[0003] To overcome this limitation, researchers have tried to modify natural humic substance by physical or chemical methods; among them, iron modification is an effective means; iron ions can be complexed or physically adsorbed / inserted into the structure of humic substance, thereby improving its adsorption and passivation capacity for heavy metals; however, in acidic environment, iron modifier is prone to form precipitate, which reduces its complexing efficiency with humic acid, thereby affecting the passivation effect on heavy metals such as cadmium and arsenic; therefore, we propose iron modified woody peat humic substance composition and its application in synchronous passivation of cadmium and arsenic in soil. SUMMARY
[0004] The present application aims to provide iron modified woody peat humic substance composition and its application in synchronous passivation of cadmium and arsenic in soil, to solve the problem of easy precipitation of iron modifier in acidic environment, which reduces its complexing efficiency with humic acid, thereby affecting the passivation effect on heavy metals such as cadmium and arsenic.
[0005] In one aspect, the present application provides an iron modified woody peat humic substance composition, comprising the following raw materials: woody peat, composite iron modifier, ammonium sulfate, potassium dihydrogen phosphate, and microbial fermentation liquor. The composite iron modifier is prepared by reacting ferrous sulfate with sodium hydrosulfite, and then mixing with pretreated zeolite.
[0006] Preferably, the ratio of the raw materials is: woody peat 90-100 parts by weight, composite iron modifier 40-60 parts by weight, ammonium sulfate 5-10 parts by weight, potassium dihydrogen phosphate 2-5 parts by weight, and microbial fermentation liquor 8-15 parts by weight.
[0007] Ammonium sulfate serves as a nitrogen source, and the released NH4 + and Cd2+ Compete for adsorption sites, so need to control the dosage to avoid the adverse effects on the fixation of cadmium; while, although phosphate can promote the precipitation of Cd3(PO4)2, thereby fixing cadmium, but excessive will compete with arsenic for the adsorption sites on the iron oxide surface, affecting the fixation effect of arsenic.
[0008] As preferred, the microbial fermentation broth is a mixed liquid prepared by co-fermentation of Bacillus subtilis and Bacillus licheniformis; the mass ratio of Bacillus subtilis and Bacillus licheniformis is 2:1, and the total viable bacterial count is greater than 1.5×109 CFU / g. .
[0009] As preferred, the preparation steps of the composite iron modifier are as follows: ferrous sulfate with a concentration of 0.1 mol / L and sodium hydrosulfite with a concentration of 0.05 mol / L are stirred at a speed of 200-300 rpm under nitrogen protection for 1-2 h to obtain a reaction product; after the reaction is completed, the reaction product is mixed with pretreated zeolite under nitrogen protection, and ball milling is performed at a speed of 300-400 rpm for 1.5-2 h; after the ball milling is completed, the mixture is taken out, washed with deionized water for 2-3 times, and dried at 60-80°C under vacuum conditions for 4-6 h to obtain the composite iron modifier.
[0010] As preferred, the molar ratio of ferrous sulfate to sodium hydrosulfite is 1:1.
[0011] As preferred, the pretreated zeolite is obtained by soaking the zeolite in a sodium chloride solution with a concentration of 1 mol / L for 24 h, then washing with hydrochloric acid with a concentration of 0.1 mol / L until neutral, and drying at 105°C. The mass ratio of the reaction product to the pretreated zeolite is 1:0.5-0.8.
[0012] As preferred, the preparation method of the iron-modified woody peat humic substance composition is as follows: S1.1, respectively, take the following raw materials: woody peat 90-100 parts by weight, composite iron modifier 40-60 parts by weight, ammonium sulfate 5-10 parts by weight, potassium dihydrogen phosphate 2-5 parts by weight, microbial fermentation broth 8-15 parts by weight; S1.2, soak the woody peat in hydrochloric acid, stir at a speed of 100-200 rpm for 20-30 min; after acid washing, rinse with deionized water until neutral; Subsequently, the woody peat solid after acid washing and water washing to neutral is added into a sodium hydroxide solution at a solid-liquid ratio of 1:10, oscillated at a speed of 150-200 rpm at 50-60°C for 1-2 h, and filtered to obtain a humic acid crude extract; adjust the pH of the crude extract to 4.5-6.5 with a hydrochloric acid solution with a concentration of 0.5 mol / L, add cellulase, and enzymatically hydrolyze at 50-55°C for 1-2 h, and filter to obtain a humic acid concentrate; The main components of cellulase include endo-enzyme, exo-enzyme and beta-glucosidase.
[0013] S1.3, the humic acid concentrate, the composite iron modifier, ammonium sulfate and potassium dihydrogen phosphate are mixed, stirring at 200-300 rpm at 35-40 DEG C for 1-2h, the microbial fermentation liquor is added, and stirring at 200-300 rpm is continued for 20-30 min, and then low-temperature drying is carried out at 40-45 DEG C for 6-8h, to obtain the iron modified woody peat humic substance composition.
[0014] As preferred, in S1.2, the concentration of hydrochloric acid is 0.1-0.5 mol / L.
[0015] As preferred, in S1.2, the concentration of sodium hydroxide solution is 0.2-0.3 mol / L. The cellulase is added in an amount of 1-3% of the dry matter mass of the humic acid crude extract.
[0016] In another aspect, the application provides the application of the iron modified woody peat humic substance composition, and the following technical scheme is adopted: the application of the above-mentioned iron modified woody peat humic substance composition in the synchronous passivation of soil cadmium and arsenic.
[0017] Compared with the prior art, the application has the following beneficial effects: In the iron modified woody peat humic substance composition and its application in the synchronous passivation of soil cadmium and arsenic, the composite iron modifier overcomes the problem that free iron is easy to precipitate in acidic soil, ensuring the stable release and efficient utilization of iron ions; secondly, iron ions can undergo complexation reaction with functional groups such as carboxyl and phenolic hydroxyl in humic acid, forming stable organic-inorganic complexes, thereby strongly fixing Cd 2+ ; at the same time, As(V) is more easily adsorbed by iron oxides (because it is negatively charged), thereby fixing As(III); the addition of pretreated zeolite can significantly improve the cadmium adsorption capacity (ion exchange) and enhance the dispersibility of the active components of iron, achieving synchronous efficient passivation of cadmium and arsenic. DETAILED DESCRIPTION
[0018] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application.
[0019] The application provides an iron modified woody peat humic substance composition, which comprises the following raw materials: woody peat, composite iron modifier, ammonium sulfate, potassium dihydrogen phosphate and microbial fermentation liquor. The composite iron modifier is prepared by mixing the pretreated zeolite with the reaction product of ferrous sulfate and sodium hydrosulfite.
[0020] The pretreated zeolite is obtained by immersing the zeolite in a 1 mol / L sodium chloride solution for 24 h, washing with a 0.1 mol / L hydrochloric acid solution until neutral, and drying at 105°C.
[0021] The microbial fermentation liquid is a mixed liquid prepared by co-fermentation of Bacillus subtilis and Bacillus licheniformis, and the mass ratio of Bacillus subtilis to Bacillus licheniformis is 2:1, and the total viable bacterial count is greater than 1.0×109 CFU / mL. The fermentation process is carried out under sterile conditions.
[0022] Example 1: Preparation method of the iron-modified wood-based peat humic substance composition, comprising the following steps: S1.1, respectively, the following raw materials are weighed: wood-based peat 90 parts by weight, composite iron modifier 40 parts by weight, ammonium sulfate 5 parts by weight, potassium dihydrogen phosphate 2 parts by weight, microbial fermentation liquid 8 parts by weight; S1.2, the wood-based peat is immersed in a 0.5 mol / L hydrochloric acid solution, stirred at a speed of 200 rpm for 30 min; after acid washing, it is washed with deionized water until neutral; Then the wood-based peat solid after acid washing and water washing to neutral is added to a 0.2 mol / L sodium hydroxide solution at a solid-liquid ratio of 1:10, and oscillated at a speed of 200 rpm at 60°C for 2 h, and filtered to obtain a crude humic acid extract; the crude extract is adjusted to pH 6.0 with a 0.5 mol / L hydrochloric acid solution, and 2% of the dry matter mass of the humic acid crude extract is added. Cellulase, 50°C enzymolysis for 2h, filtration to obtain humic acid concentrate; S1.3, the humic acid concentrate, composite iron modifier, ammonium sulfate and potassium dihydrogen phosphate are mixed, stirred at a speed of 300 rpm at 40°C for 2 h, microbial fermentation liquid is added, and stirred at a speed of 300 rpm for 30 min, then dried at 40°C for 6 h to obtain the iron-modified wood-based peat humic substance composition.
[0023] The preparation steps of the composite iron modifier are as follows: 0.1 mol / L ferrous sulfate and 0.05 mol / L sodium hydrosulfite (molar ratio 1:1) are stirred at a speed of 300 rpm under nitrogen protection for 2 h to obtain a reaction product; after the reaction is completed, the reaction product is mixed with the pretreated zeolite (mass ratio 1:0.5) under nitrogen protection, and ball milled at a speed of 400 rpm for 2 h; after ball milling, the mixture is taken out, washed with deionized water for 3 times, and dried at 60°C under vacuum conditions for 6 h to obtain the composite iron modifier.
[0024] Example 2: Preparation method of iron-modified woody peat humic substance composition, comprising the following steps: S1.1, respectively, take the following raw materials: woody peat 100 parts by weight, composite iron modifier 60 parts by weight, ammonium sulfate 10 parts by weight, potassium dihydrogen phosphate 5 parts by weight, microbial fermentation broth 15 parts by weight; S1.2, the woody peat is immersed in 0.5 mol / L hydrochloric acid, and stirred at 200 rpm for 30 min; after acid washing, wash with deionized water until neutral; Then the woody peat solid which has been acid washed and purified and washed with water to neutral is added to 0.2 mol / L sodium hydroxide solution at a solid-liquid ratio of 1:10, and oscillated at 200 rpm at 60°C for 2h, and filtered to obtain a crude humic acid extract; adjust the pH of the crude extract to 6.0 with 0.5 mol / L hydrochloric acid, add 2% cellulase based on the dry matter mass of the humic acid crude extract, and enzymatically hydrolyze at 50°C for 2h, and filter to obtain a humic acid concentrate; S1.3, the humic acid concentrate, the composite iron modifier, ammonium sulfate and potassium dihydrogen phosphate are mixed, stirred at 300 rpm at 40°C for 2h, the microbial fermentation broth is added, and stirred at 300 rpm for 30 min, and then dried at 40°C for 6h to obtain the iron-modified woody peat humic substance composition.
[0025] The preparation steps of the composite iron modifier are as follows: 0.1 mol / L ferrous sulfate and 0.05 mol / L sodium hydrosulfite (molar ratio 1:1) are stirred at 300 rpm under nitrogen protection for 2h to obtain a reaction product; after the reaction is completed, the reaction product is mixed with pretreated zeolite (mass ratio 1:0.8) under nitrogen protection, and ball milled at 400 rpm for 2h; after ball milling, the mixture is taken out, washed with deionized water for 3 times, and dried at 60°C under vacuum conditions for 6h to obtain the composite iron modifier.
[0026] Example 3: Preparation method of iron-modified woody peat humic substance composition, comprising the following steps: S1.1, respectively, take the following raw materials: woody peat 100 parts by weight, composite iron modifier 60 parts by weight, ammonium sulfate 10 parts by weight, potassium dihydrogen phosphate 5 parts by weight, microbial fermentation broth 15 parts by weight; S1.2, the woody peat is immersed in 0.5 mol / L hydrochloric acid, and stirred at 200 rpm for 30 min; after acid washing, wash with deionized water until neutral; Subsequently, the wood peat solids purified by acid washing and washed to neutral were added into a 0.2 mol / L sodium hydroxide solution at a solid-liquid ratio of 1:10, oscillated at 200 rpm at 60°C for 2 h, and filtered to obtain a humic acid crude extract; the pH of the crude extract was adjusted to 6.0 with a 0.5 mol / L hydrochloric acid, 2% cellulase based on the dry matter mass of the humic acid crude extract was added, and enzymatic hydrolysis was performed at 50°C for 2 h, and filtered to obtain a humic acid concentrate; S1.3, the humic acid concentrate, the composite iron modifier, ammonium sulfate and potassium dihydrogen phosphate were mixed, stirred at 300 rpm at 40°C for 2 h, the microbial fermentation liquor was added, and stirring was continued at 300 rpm for 30 min, and then dried at 40°C for 6 h to obtain the iron-modified wood peat humus composition.
[0027] The preparation steps of the composite iron modifier are as follows: 0.1 mol / L ferrous sulfate and 0.05 mol / L sodium hyposulfite (molar ratio 1:1) were stirred at 300 rpm under nitrogen protection for 2 h to obtain a reaction product; after the reaction was completed, the reaction product and the pretreated zeolite (mass ratio 1:0.6) were mixed under nitrogen protection, and ball milling was performed at 400 rpm for 2 h; after the ball milling was completed, the mixture was taken out, washed with deionized water for 3 times, and dried at 60°C under vacuum conditions for 6 h to obtain the composite iron modifier.
[0028] Example 4: The preparation method of the iron-modified wood peat humus composition includes the following steps: S1.1, the following raw materials were weighed respectively: wood peat 95 parts by weight, composite iron modifier 30 parts by weight, ammonium sulfate 7 parts by weight, potassium dihydrogen phosphate 4 parts by weight, and microbial fermentation liquor 12 parts by weight; S1.2, the wood peat was immersed in a 0.5 mol / L hydrochloric acid, and stirred at 200 rpm for 30 min; after the acid washing, the wood peat was washed with deionized water until neutral; Subsequently, the wood peat solids purified by acid washing and washed to neutral were added into a 0.2 mol / L sodium hydroxide solution at a solid-liquid ratio of 1:10, oscillated at 200 rpm at 60°C for 2 h, and filtered to obtain a humic acid crude extract; the pH of the crude extract was adjusted to 6.0 with a 0.5 mol / L hydrochloric acid, 2% cellulase based on the dry matter mass of the humic acid crude extract was added, and enzymatic hydrolysis was performed at 50°C for 2 h, and filtered to obtain a humic acid concentrate; S1.3, the humic acid concentrate, the composite iron modifier, ammonium sulfate and potassium dihydrogen phosphate were mixed, stirred at 300 rpm at 40°C for 2 h, the microbial fermentation liquor was added, and stirring was continued at 300 rpm for 30 min, and then dried at 40°C for 6 h to obtain the iron-modified wood peat humus composition.
[0029] The preparation steps of the composite iron modifier are as follows: ferrous sulfate with a concentration of 0.1 mol / L and sodium hyposulfite with a concentration of 0.05 mol / L (molar ratio of 1:1) are stirred at a speed of 300 rpm under nitrogen protection for 2 h to obtain a reaction product; after the reaction is completed, the reaction product is mixed with pretreated zeolite (mass ratio of 1:0.6) under nitrogen protection, and ball milling is performed at a speed of 400 rpm for 2 h; after the ball milling is completed, the mixture is taken out, washed with deionized water for 3 times, and dried at 60°C under vacuum conditions for 6 h to obtain the composite iron modifier.
[0030] Example 5: The preparation method of the iron modified woody peat humus composition includes the following steps: S1.1, the following raw materials are weighed respectively: woody peat 95 parts by weight, composite iron modifier 50 parts by weight, ammonium sulfate 7 parts by weight, potassium dihydrogen phosphate 4 parts by weight, and microbial fermentation liquor 12 parts by weight; S1.2, the woody peat is immersed in hydrochloric acid with a concentration of 0.5 mol / L, and stirred at a speed of 200 rpm for 30 min; after acid washing, it is washed with deionized water until neutral; Then the woody peat solid after acid washing and water washing to neutral is added into sodium hydroxide solution with a concentration of 0.2 mol / L at a solid-liquid ratio of 1:10, oscillated at a speed of 200 rpm at 60°C for 2 h, and filtered to obtain a humic acid crude extract; the pH of the crude extract is adjusted to 6.0 with hydrochloric acid with a concentration of 0.5 mol / L, 2% of cellulase based on the dry matter mass of the humic acid crude extract is added, and enzyme hydrolysis is performed at 50°C for 2 h, and filtered to obtain a humic acid concentrate; S1.3, the humic acid concentrate, the composite iron modifier, ammonium sulfate and potassium dihydrogen phosphate are mixed, stirred at a speed of 300 rpm at 40°C for 2 h, the microbial fermentation liquor is added, and stirred at a speed of 300 rpm for 30 min, and then dried at a low temperature of 40°C for 6 h to obtain the iron modified woody peat humus composition.
[0031] The preparation steps of the composite iron modifier are as follows: ferrous sulfate with a concentration of 0.1 mol / L and sodium hyposulfite with a concentration of 0.05 mol / L (molar ratio of 1:1) are stirred at a speed of 300 rpm under nitrogen protection for 2 h to obtain a reaction product; after the reaction is completed, the reaction product is mixed with pretreated zeolite (mass ratio of 1:0.3) under nitrogen protection, and ball milling is performed at a speed of 400 rpm for 2 h; after the ball milling is completed, the mixture is taken out, washed with deionized water for 3 times, and dried at 60°C under vacuum conditions for 6 h to obtain the composite iron modifier.
[0032] Comparative Example 1: The method of Example 3 was used, and in the iron-modified woody peat humus composition and its application in the simultaneous passivation of soil cadmium and arsenic, the composite iron modifier was not used, and the iron modifier was directly used.
[0033] Comparative Example 2: The method of Example 3 was used, and in the preparation method of the composite iron modifier, the pretreated zeolite was not added.
[0034] Comparative Example 3: The method of Example 3 was used, and in the iron-modified woody peat humus composition and its application in the simultaneous passivation of soil cadmium and arsenic, the microbial fermentation broth was not added.
[0035] The application performance index test items and test standards of the iron-modified woody peat humus composition prepared by adding a composite iron modifier in the preparation method of the iron-modified woody peat humus composition in the soil cadmium and arsenic simultaneous passivation are as follows: The air-dried soil was sieved, 10.00 g ± 0.05 g was weighed and placed in a 50 mL centrifuge tube, 20 mL of DTPA-CaCl2-TEA extractant (0.005 mol / L DTPA + 0.01 mol / L CaCl2+ 0.005 mol / L TEA, pH = 7.3) was added, and it was shaken at 25℃±1℃ for 1 hour at a horizontal shaking speed of 180 rpm; centrifuged at 4000 rpm, and the supernatant was taken after 10 min, filtered through a 0.45 μm filter membrane, and the cadmium content was determined by atomic absorption spectrometry (AAS).
[0036] 1.00 g of air-dried soil sample was weighed and placed in a 50 mL centrifuge tube, 25 mL of 0.05 mol / L ammonium dihydrogen phosphate solution was added, and it was shaken at 25℃±1℃ for 16 hours (180 rpm), then centrifuged at 4500 rpm for 5 minutes, and the filtrate was taken after filtration, 1% thiourea + 10% HCl mixed solution was added for reduction for 10 minutes, and finally the content of available arsenic in the soil was determined by hydride generation-atomic fluorescence spectrometer.
[0037] The iron-modified woody peat humus composition was added to the contaminated soil, the field water holding capacity was maintained at 60-70%, and it was cultured in the dark at 25℃ for 180 days; the available heavy metals were extracted twice, the available cadmium / arsenic content of the soil after culture was determined, and the heavy metal reactivation rate was calculated.
[0038] The iron-modified woody peat humus compositions prepared in Examples 1-5 and Comparative Examples 1-3 were tested by the above standards, and the data obtained are shown in Table 1: Table 1 Performance data of iron-modified woody peat humus compositions of Examples 1-5 and Comparative Examples 1-3
[0039] It can be seen from Examples 1-3 and Example 4 that when the weight of the composite iron modifier increases in the iron-modified humus composition containing other components, the soil available cadmium content, the soil available arsenic content and the heavy metal reactivation rate first decrease and then increase; the sulfur group in the composite iron modifier fixes cadmium through a covalent complex mechanism to form a CdS precipitate that is difficult to dissolve; and arsenic is adsorbed by ligand exchange with iron oxide to form an Fe-AsO4 inner ring complex; in addition, the iron modifier is oxidized in the soil to generate more amorphous iron oxides (such as goethite and greigite), which further reduce the availability of heavy metals by wrapping heavy metal particles, blocking their contact with the soil solution, and forming Fe-O-Cd or Fe-AsO4 co-precipitates with Cd / As.
[0040] It can be seen from Examples 1-3 and Example 5 that when the mass ratio of the product to the pretreated zeolite increases in the iron-modified humus composition containing other components, the soil available cadmium content, the soil available arsenic content and the heavy metal reactivation rate first decrease and then increase; the zeolite has a high cation exchange capacity and locks soluble cadmium ions in the pores of the silica-alumina framework through a displacement reaction, thereby achieving fixation of cadmium; the zeolite adsorbs and fixes Cd 2+ on the surface and in the pores of the crystal framework, blocking the diffusion of cadmium.
[0041] According to the above test experiments, Example 3 is taken as the optimal example. It can be seen from the comparison between Example 3 and Comparative Example 1 that when the composite iron modifier is not used and the iron modifier is directly used, the soil available arsenic content and the heavy metal reactivation rate are significantly increased; arsenic mainly exists in the form of anions in the soil, and its adsorption and stabilization depend on the ligand exchange of iron oxides; however, the single iron modifier is prone to hydrolysis and precipitation in an acidic environment, which reduces the specific surface area of the iron oxide and thus reduces the adsorption sites for arsenic; in addition, phosphate in the soil competes for the adsorption sites with the iron oxide, further promoting the desorption and reactivation of arsenic and increasing its mobility; under acidic conditions, part of the arsenic is reduced to As(III) which is more toxic, further exacerbating the risk of migration.
[0042] It can be seen from the comparison between Example 3 and Comparative Example 2 that when the pretreated zeolite is not added in the preparation method of the composite iron modifier, the soil available cadmium content is significantly increased; the zeolite can lock Cd 2+ in the silica-alumina framework through an ion exchange reaction, thereby reducing its bioavailability; when the zeolite is not added, it is prone to agglomeration into micron-sized aggregates, which greatly reduces the specific surface area and the amount of available sulfur released, thereby affecting the completeness of the CdS precipitation reaction; in addition, the porous structure of the zeolite helps to continuously release OH - , buffer the soil acidity and prevent the dissolution of the CdS precipitate; without the zeolite, the soil H+ With the increase of concentration, the protonation can dissolve the CdS precipitate, and the acidic environment promotes the desorption of cadmium from the humic acid-iron complex, further increasing the bioavailability of cadmium.
[0043] As can be seen by comparing Example 3 with Comparative Example 3, in the iron-modified woody peat humus composition and its application in the simultaneous passivation of cadmium and arsenic in soil, the content of available arsenic in soil and the reactivation rate of heavy metals are significantly increased when no microbial fermentation liquid is added; the bioavailability of arsenic is closely related to its valence state, and microorganisms can oxidize As 3+ or reduce As 5+ to form iron arsenic precipitate (such as arsenic iron ore FeAsO4), which significantly reduces the bioavailability of dissolved arsenic; under the condition of dry-wet alternation in paddy field, the anoxic environment promotes the reduction of As 5+ to easily soluble As 3+ , and the lack of microorganisms leads to the lack of reoxidation ability, resulting in continuous release of arsenic.
[0044] The above shows and describes the basic principles, main features and advantages of the present application. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only preferred examples of the present application and are not intended to limit the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.
Claims
1. Iron modified woody peat humus composition, characterized in that, The raw materials include woody peat, composite iron modifier, ammonium sulfate, potassium dihydrogen phosphate, and microbial fermentation liquor. The composite iron modifier is prepared by mixing pretreated zeolite with the reaction product of ferrous sulfate and sodium hydrosulfite.
2. The iron-modified woody peat humic substance composition of claim 1, wherein, The ratio of the raw materials is: woody peat 90-100 parts by weight, composite iron modifier 40-60 parts by weight, ammonium sulfate 5-10 parts by weight, potassium dihydrogen phosphate 2-5 parts by weight, and microbial fermentation liquor 8-15 parts by weight.
3. The iron-modified woody peat humic substance composition according to claim 2, characterized in that, The microbial fermentation liquid is a mixed liquid prepared by co-fermentation of Bacillus subtilis and Bacillus licheniformis; the mass ratio of Bacillus subtilis and Bacillus licheniformis is 2:1, and the total viable bacterial count is greater than .
4. The iron-modified woody peat humic substance composition according to claim 3, characterized in that, The preparation steps of the composite iron modifier are: stirring the ferrous sulfate with a concentration of 0.1 mol / L and the sodium hydrosulfite with a concentration of 0.05 mol / L under nitrogen protection at a speed of 200-300 rpm for 1-2 h to obtain a reaction product; after the reaction is completed, mixing the reaction product with pretreated zeolite under nitrogen protection, and ball milling at a speed of 300-400 rpm for 1.5-2 h; after the ball milling is completed, taking out the mixture, washing it with deionized water for 2-3 times, and drying it at 60-80°C under vacuum conditions for 4-6 h to obtain the composite iron modifier.
5. The iron-modified woody peat humic substance composition according to claim 4, characterized in that, The molar ratio of the ferrous sulfate to the sodium hydrosulfite is 1:
1.
6. The iron-modified woody peat humic substance composition according to claim 5, characterized in that, The pretreated zeolite is obtained by soaking the zeolite in a sodium chloride solution with a concentration of 1 mol / L for 24 h, washing it with hydrochloric acid with a concentration of 0.1 mol / L until it is neutral, and drying it at 105°C. The mass ratio of the reaction product to the pretreated zeolite is 1:0.5-0.
8.
7. The iron-modified woody peat humic substance composition according to claim 6, characterized in that, The preparation method of the iron-modified woody peat humus composition is as follows: S1.1, respectively weighing the following raw materials: woody peat 90-100 parts by weight, composite iron modifier 40-60 parts by weight, ammonium sulfate 5-10 parts by weight, potassium dihydrogen phosphate 2-5 parts by weight, and microbial fermentation liquor 8-15 parts by weight; S1.2, immersing the woody peat in hydrochloric acid and stirring it at a speed of 100-200 rpm for 20-30 min; after the acid washing, washing it with deionized water until it is neutral; Then, adding the woody peat solid which has been acid washed and purified and washed with water until it is neutral into a sodium hydroxide solution at a solid-liquid ratio of 1:10, oscillating it at a speed of 150-200 rpm at 50-60°C for 1-2 h, and filtering to obtain a crude humic acid extract; adjusting the pH of the crude extract to 4.5-6.5 with hydrochloric acid with a concentration of 0.5 mol / L, adding cellulase, and enzymatically hydrolyzing it at 50-55°C for 1-2 h, and filtering to obtain a humic acid concentrate; S1.3, mixing the humic acid concentrate, composite iron modifier, ammonium sulfate, and potassium dihydrogen phosphate, stirring them at a speed of 200-300 rpm at 35-40°C for 1-2 h, adding microbial fermentation liquor, continuing to stir at a speed of 200-300 rpm for 20-30 min, and drying it at a low temperature of 40-45°C for 6-8 h to obtain the iron-modified woody peat humus composition.
8. The iron-modified woody peat humic substance composition according to claim 7, characterized in that, In S1.2, the concentration of the hydrochloric acid is 0.1-0.5 mol / L.
9. The iron-modified woody peat humic substance composition according to claim 8, characterized in that, In S1.2, the concentration of the sodium hydroxide solution is 0.2-0.3 mol / L. The amount of cellulase added is 1-3% of the dry matter mass of the crude humic acid extract.
10. Use of an iron-modified woody peat humic substance composition, characterized in that, Use of the iron-modified woody peat humic substance composition of claim 9 in the simultaneous passivation of cadmium and arsenic in soil.