Preparation of liquid ferrous sulfide modified carbon quantum dots and application of liquid ferrous sulfide modified carbon quantum dots in soil improvement

Abstract

The invention discloses preparation of liquid ferrous sulfide modified carbon quantum dots and application of the liquid ferrous sulfide modified carbon quantum dots in soil improvement, a preparation method comprises the following steps: S1, dissolving urea and / or thiourea in water, adding a charcoal precursor, mixing and stirring, reacting for 4-12 hours at 120-180 DEG C, cooling, and recovering supernate to obtain liquid charcoal quantum dots; s2, adding sodium polyacrylate into water to obtain a solution A, adding the liquid biochar quantum dots into the solution A, and stirring under the protection of inert gas to obtain a solution B; s3, dissolving FeSO4. 7H2O in the degassed water to obtain a solution C, adding the solution C into the solution B under the protection of inert gas, and stirring to obtain a solution E; s4, dissolving Na2S in the degassed water to obtain a solution D, and dropwise adding the Na2S into the solution D under the protection of inert gas to obtain a black solution; s5, centrifuging the black solution to remove solid substances to obtain the liquid ferrous sulfide modified carbon quantum dots. The material disclosed by the invention is applied to the soil improvement and remediation process, and has important significance on improving the soil remediation efficiency and reducing the cost.

Description

Technical Field

[0001] The present invention relates to the field of environmental management, and in particular to the preparation of liquid ferrous sulfide modified carbon quantum dots and their application in soil improvement. Background Art

[0002] Industrial mining and agricultural activities result in the release of large quantities of toxic substances, such as inorganic arsenic, hexavalent chromium, and organic arsenic, into the aquatic and soil environments. Organic arsenic, upon oxidation in the environment, can release the more toxic arsenic (As(III)) and arsenic (As(V)). Furthermore, the extensive application of fertilizers and pesticides in agricultural soils results in large quantities of toxic substances, such as phosphorus and arsenic, being washed into the aquatic environment with rainwater, leading to agricultural non-point source pollution. Therefore, soil improvement and the prevention of the loss and transfer of toxic substances, such as heavy metals, are essential measures to ensure environmental safety. However, soil exists as a solid material, such as granular minerals, and contamination is inherent, cumulative, irreversible, and difficult to control. Remediation of soil solids presents challenges such as difficulty in stirring and uneven mixing, requiring significant human and material resources, and potentially creating blind spots in remediation. Currently, remediation of heavy metal-contaminated sites primarily involves off-site leaching or immobilization. These treatments alter the soil's original structure and physical and chemical properties, hindering its re-use. Summary of the invention

[0003] The main purpose of the present invention is to propose a preparation method of liquid ferrous sulfide modified carbon quantum dots and its application in soil improvement.

[0004] The technical solution of the present invention is as follows:

[0005] In a first aspect, a method for preparing liquid ferrous sulfide modified carbon quantum dots is provided, comprising the following steps:

[0006] S1. Dissolve urea and / or thiourea in water, add biochar precursor, mix and stir thoroughly to dissolve, react at 120-180°C for 4-12 hours, cool, and recover the supernatant to obtain liquid biochar quantum dots;

[0007] S2. Sodium polyacrylate is added to water to obtain solution A, the liquid biochar quantum dots are added to solution A, and the mixture is stirred under inert gas to obtain solution B;

[0008] S3. Dissolve FeSO4·7H2O in degassed water to obtain solution C. Under the protection of inert gas, add solution C dropwise to solution B and stir to obtain solution E.

[0009] S4. Dissolve Na2S in degassed water to obtain solution D. Under inert gas protection, add solution E dropwise to solution D to obtain a black solution;

[0010] S5. Centrifuge the black solution to remove solid substances, obtaining a solution of sodium polyacrylate-coupled biochar quantum dots dispersed with ferrous sulfide in solution state, which is the liquid ferrous sulfide-modified carbon quantum dots.

[0011] Preferably, in step S1, the mass ratio of "urea and / or thiourea" to the biochar precursor is 1:1 - 30.

[0012] Preferably, in step S1, the biochar precursor is prepared from solid waste of the gardening type. Preferably, the biochar precursor is prepared from Axonopus compressus. More preferably, the biochar precursor is obtained by washing the dark green Axonopus compressus, drying, pulverizing, and sieving through a 60-mesh sieve.

[0013] Preferably, in step S2, 0.03 g or 0.06 g of sodium polyacrylate is added to 240 mL of water to obtain solution A, and 2 mL of the liquid biochar quantum dots is added to solution A, and they are stirred and mixed under inert gas protection to obtain solution B.

[0014] Preferably, in step S3, 0.19 g of FeSO4·7H2O is dissolved in 40 mL of degassed water to obtain solution C.

[0015] Preferably, in step S4, 0.18 g of Na2S is dissolved in 20 mL of degassed water to obtain solution D.

[0016] Preferably, in step S5, the black solution is centrifuged at 10000 rpm to remove solid substances.

[0017] In a second aspect, there is provided a liquid ferrous sulfide-modified carbon quantum dot prepared by the preparation method described in the first aspect.

[0018] In a third aspect, there is provided an application of the liquid ferrous sulfide-modified carbon quantum dot described in the second aspect in soil improvement. The liquid ferrous sulfide-modified carbon quantum dot is added to the soil as a soil conditioner, and the liquid ferrous sulfide-modified carbon quantum dot adsorbs and fixes heavy metals and / or phosphorus in the soil.

[0019] Preferably, the heavy metal is at least one of cadmium, inorganic arsenic, organic arsenic, and chromium.

[0020] The beneficial effects of the present invention include: The present invention prepares liquid ferrous sulfide modified carbon quantum dots by coupling and dispersing ferrous sulfide with sodium polyacrylate and liquid biochar quantum dots, which improves the mass transfer efficiency of liquid ferrous sulfide modified carbon quantum dots in soil solid media, and hydrogen peroxide can be in-situ generated during the photoexcitation removal process. The liquid composite material prepared by the present invention has good effects on heavy metal fixation, phosphorus retention and soil electron transfer in soil. The liquid ferrous sulfide modified carbon quantum dots of the present invention are applied to the process of soil improvement and remediation, which is of great significance for improving soil remediation efficiency and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the organic arsenic removal diagram of the liquid ferrous sulfide modified carbon quantum dots prepared in Example 1 of the present invention.

[0022] Figure 2 It is the diagram of synchronous hydrogen peroxide production during the process of removing organic arsenic by the liquid ferrous sulfide modified carbon quantum dots prepared in Example 1 of the present invention.

[0023] Figure 3 It is the effect diagram of fixing arsenic in soil by the liquid ferrous sulfide modified carbon quantum dots prepared in Example 1 of the present invention.

[0024] Figure 4a and 4b They are respectively the TEM diagrams of the liquid ferrous sulfide modified carbon quantum dots prepared in Example 1 of the present invention at different magnifications. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0026] The embodiment of the present invention provides a preparation method of liquid ferrous sulfide modified carbon quantum dots, which includes the following steps:

[0027] S1. Dissolve urea and / or thiourea in water, add a biochar precursor, fully mix and stir to dissolve, react at 120 - 180 °C for 4 - 12 h, cool, and recover the supernatant to obtain liquid biochar quantum dots;

[0028] S2. Add sodium polyacrylate to water to obtain solution A, add the liquid biochar quantum dots to solution A, and stir and mix under inert gas protection to obtain solution B;

[0029] S3. Dissolve FeSO4·7H2O in degassed water to obtain solution C, and under inert gas protection, drop solution C into solution B and stir to obtain solution E;

[0030] S4. Dissolve Na2S in degassed water to obtain solution D. Under the protection of inert gas, drop solution E into solution D to obtain a black solution;

[0031] S5. Centrifuge the black solution to remove solid substances to obtain a solution of polyacrylate sodium-coupled biochar quantum dots dispersing ferrous sulfide in a solution state, which is the liquid ferrous sulfide-modified carbon quantum dots.

[0032] In soil improvement, solid materials are not easy to mix and there are blind spots. In the liquid ferrous sulfide-modified carbon quantum dots prepared by the present invention, polyacrylate sodium and liquid biochar quantum dots are coupled to disperse ferrous sulfide, avoiding the precipitation of ferrous sulfide into solids. During the treatment process, an electron shuttle can be provided in the soil to improve soil mass transfer, promote electron transfer, which is beneficial to activating soil stable minerals and promoting the iron cycle in the soil. As an unstable mineral, ferrous sulfide is more likely to release ferrous ions and sulfide ions. At the same time, the iron cycle activates free radicals. Therefore, the liquid ferrous sulfide-modified carbon quantum dots of the present invention can be added to the soil as a soil conditioner to adsorb and fix heavy metals and / or phosphorus in the soil.

[0033] In a preferred embodiment, in step S1, the mass ratio of "urea and / or thiourea" to the biochar precursor is 1:1 - 30.

[0034] In a preferred embodiment, in step S1, the biochar precursor is prepared from solid waste in the gardening industry. Preferably, the biochar precursor is prepared from Axonopus compressus. More preferably, the biochar precursor is obtained by washing the dark green Axonopus compressus, drying, pulverizing, and sieving through a 60-mesh sieve. The present invention realizes the resource utilization and harmless treatment of waste in the gardening industry, and at the same time meets the in-situ improvement of heavy metal-contaminated soil.

[0035] In a preferred embodiment, in step S2, add 0.03 g or 0.06 g of polyacrylate sodium to 240 mL of water to obtain solution A, add 2 mL of the liquid biochar quantum dots to solution A, and stir and mix under the protection of inert gas to obtain solution B.

[0036] In a preferred embodiment, in step S3, dissolve 0.19 g of FeSO4·7H2O in 40 mL of degassed water to obtain solution C.

[0037] In a preferred embodiment, in step S4, dissolve 0.18 g of Na2S in 20 mL of degassed water to obtain solution D.

[0038] In a preferred embodiment, in step S5, centrifuge the black solution at 10000 rpm to remove solid substances.

[0039] The embodiment of the present invention also provides a liquid ferrous sulfide-modified carbon quantum dot prepared by the above preparation method.

[0040] An embodiment of the present invention also provides an application of the liquid ferrous sulfide modified carbon quantum dots in soil improvement. The liquid ferrous sulfide modified carbon quantum dots are added to the soil as a soil conditioner, and the liquid ferrous sulfide modified carbon quantum dots adsorb and fix heavy metals and / or phosphorus in the soil.

[0041] In a preferred embodiment, the heavy metals are at least one of cadmium, inorganic arsenic, organic arsenic (such as roxarsone), and chromium.

[0042] The following further illustrates the present invention through specific examples.

[0043] Example 1

[0044] Collect the harvested broadleaf carpetgrass from the Tsinghua Park of Xili University Town in Shenzhen, Guangdong Province, and dry it naturally under sunlight (until the leaves of the broadleaf carpetgrass turn from green to dark green). Take 30 g of the dried broadleaf carpetgrass and place it in a 2 L beaker, wash it with deionized water accompanied by ultrasonic waves for 20 min, and repeat several times until the washing liquid is free of soil. Then put it in an oven and dry it at 60 °C for 24 h, crush it with a small crusher, pass it through a 60-mesh sieve, and finally store it in a drying oven.

[0045] Dissolve 1 g of urea in 100 mL of water, add 1 g of the above-prepared crushed broadleaf carpetgrass into the solution, and mix and stir well to dissolve. Put the above-treated mixture into a sealed reaction kettle and react in an oven at 180 °C for 5 h, cool it naturally, recover the supernatant, and obtain liquid biochar quantum dots (Carbon Quantum Dots, CQDs);

[0046] Add 0.03 g of sodium polyacrylate (PAA) to 240 mL of distilled water and stir well to obtain solution A; add 2 mL of CQDs to solution A, and stir and mix repeatedly under nitrogen protection for 60 min to obtain solution B; dissolve 0.19 g of FeSO4·7H2O in 40 mL of degassed water to obtain solution C; dissolve 0.18 g of Na2S in 20 mL of degassed water to obtain solution D; under nitrogen protection, drop solution C into solution B, stir magnetically for 1 h to obtain a light green mixed solution E; under nitrogen protection, drop solution D into solution E, finally generate a black solution, remove the solid matter by centrifugation at 10,000 rpm, and obtain polyacrylate-coupled biochar quantum dot-dispersed ferrous sulfide in solution state, that is, liquid ferrous sulfide modified carbon quantum dots (named: FeS / PAA-CQDs), and store them in the refrigerator.

[0047] Example 2

[0048] The difference from Example 1 is that 1 g of urea in Example 1 is replaced with 1 g of thiourea. Specifically:

[0049] Collect the harvested Axonopus compressus from the Tsinghua campus of Xili University Town in Shenzhen, Guangdong Province, and dry it naturally under sunlight (until the leaves of Axonopus compressus turn from bluish-green to dark green). Take 30 g of the dried Axonopus compressus and place it in a 2 L beaker. Wash it with deionized water accompanied by ultrasonic cleaning for 20 min, and repeat several times until the cleaning solution is free of mud. Then put it in an oven and dry it at 60 °C for 24 h. Crush it with a small crusher, pass through a 60-mesh sieve, and finally store it in a drying oven.

[0050] Dissolve 1 g of thiourea in 100 mL of water, add 1 g of the above-prepared crushed Axonopus compressus into the solution, and mix and stir thoroughly to dissolve. Load the above-treated mixture into a sealed reaction kettle and react in an oven at 180 °C for 5 h. Cool it naturally, recover the supernatant, and obtain liquid biochar quantum dots (CQDs);

[0051] Add 0.03 g of sodium polyacrylate (PAA) to 240 mL of distilled water and stir well to obtain solution A; add 2 mL of CQDs to solution A, and repeat stirring and mixing for 60 min under nitrogen protection to obtain solution B; dissolve 0.19 g of FeSO4·7H2O in 40 mL of degassed water to obtain solution C; dissolve 0.18 g of Na2S in 20 mL of degassed water to obtain solution D; under nitrogen protection, add solution C dropwise to solution B, stir magnetically for 1 h to obtain a light green mixed solution E; under nitrogen protection, add solution D dropwise to solution E, and finally form a black solution. Remove the solid matter by centrifugation at 10,000 rpm to obtain sodium polyacrylate-coupled biochar quantum dot-dispersed iron sulfide in solution state, namely liquid iron sulfide-modified carbon quantum dots (named: FeS / PAA-CQDs), and store it in the refrigerator.

[0052] Example 3

[0053] The difference from Example 1 is that 1 g of urea in Example 1 is replaced with 1 g of urea / thiourea (mass ratio 1:1). Specifically:

[0054] Collect the harvested Axonopus compressus from the Tsinghua campus of Xili University Town in Shenzhen, Guangdong Province, and dry it naturally under sunlight (until the leaves of Axonopus compressus turn from bluish-green to dark green). Take 30 g of the dried Axonopus compressus and place it in a 2 L beaker. Wash it with deionized water accompanied by ultrasonic cleaning for 20 min, and repeat several times until the cleaning solution is free of mud. Then put it in an oven and dry it at 60 °C for 24 h. Crush it with a small crusher, pass through a 60-mesh sieve, and finally store it in a drying oven.

[0055] 1 g of urea / thiourea (mass ratio 1:1) was dissolved in 100 mL of water, and 1 g of the pulverized Axonopus compressus prepared above was added into the solution, followed by thorough mixing and stirring for dissolution. The above-treated mixture was loaded into a sealed reaction kettle and reacted in an oven at 180 °C for 5 h, then naturally cooled, and the supernatant was recovered to obtain liquid biochar quantum dots (CQDs).

[0056] 0.03 g of sodium polyacrylate (PAA) was added to 240 mL of distilled water and stirred thoroughly to obtain solution A; 2 mL of CQDs was added to solution A, and the mixture was repeatedly stirred and mixed for 60 min under nitrogen protection to obtain solution B; 0.19 g of FeSO4·7H2O was dissolved in 40 mL of degassed water to obtain solution C; 0.18 g of Na2S was dissolved in 20 mL of degassed water to obtain solution D; under nitrogen protection, solution C was added dropwise to solution B, and magnetic stirring was carried out for 1 h to obtain a light green mixed solution E; under nitrogen protection, solution D was added dropwise to solution E, and finally a black solution was formed. The solid substances were removed by centrifugation at 10,000 rpm to obtain polyacrylate-coupled biochar quantum dot-dispersed iron sulfide in solution state, namely liquid iron sulfide-modified carbon quantum dots (named: FeS / PAA-CQDs), which were stored in the refrigerator.

[0057] The arsenic removal performance of the FeS / PAA-CQDs prepared in Example 1 was measured and compared for organoarsenic (roxarsone).

[0058] It can be Figure 1 found that compared with pure FeS, CQDs, PAA, and FeS-CQDs, the arsenic removal performance of FeS / PAA-CQDs was significantly increased, mainly because the liquid state significantly enhanced its contact and mass transfer effects. The arsenic removal efficiency of the FeS-CQDs composite material was lower than that of FeS / PAA-CQDs mainly because the dispersion of FeS was not obvious, the solution formed oxidation during the treatment process of the powdery material, and the electron transfer efficiency was significantly reduced.

[0059] It can be Figure 2 found from that during the removal process, it was found that the FeS / PAA-CQDs obtained after coupling modification produced the highest concentration of hydrogen peroxide, and the hydrogen peroxide decomposed rapidly until it stabilized. From this, it can be inferred that FeS / PAA-CQDs can effectively produce hydrogen peroxide during the oxidation process of organoarsenic to promote the oxidation decomposition and fixation of organic matter.

[0060] As Figure 3 shown, through different mass concentrations of FeS / PAA-CQDs ( Figure 3In [the text], CK represents the control group, that is, the soil without FeS / PAA-CQDs. It was found that when the addition ratio was 0.5 wt%, the concentration of available arsenic in the soil decreased significantly, further proving that liquid FeS / PAA-CQDs can achieve the fixation of available arsenic in the soil.

[0061] As Figure 4a and 4b shown, it can be found from the TEM image of the powdered liquid FeS / PAA-CQDs obtained by freeze-drying that FeS / PAA-CQDs are nano-thin flakes.

[0062] The present invention prepares a liquid FeS / PAA-CQDs material to solve the problems of mixed pollution of heavy metals and organic matters in soil, loss of soil phosphate fertilizer, and difficulty in mixing powder materials in soil, realizing the efficient fixation of heavy metals cadmium, inorganic arsenic, chromium, organic arsenic (such as roxarsone), and phosphorus, and in-situ generation of hydrogen peroxide during the photoexcitation removal process.

[0063] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those skilled in the technical field to which the present invention belongs, without departing from the concept of the present invention, several equivalent substitutions or obvious modifications can be made, and as long as the performance or use is the same, they should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A preparation method of liquid iron sulfide modified carbon quantum dots, characterized in that, It includes the following steps: S1. Dissolve urea and / or thiourea in water, add the biochar precursor, fully mix and stir to dissolve, then react at 120 - 180 °C for 4 - 12 h, cool, recover the supernatant to obtain liquid biochar quantum dots; S2. Add sodium polyacrylate to water to obtain solution A, add the liquid biochar quantum dots to solution A, and stir and mix under the protection of inert gas to obtain solution B; S3. Dissolve FeSO4·7H2O in degassed water to obtain solution C, under the protection of inert gas, dropwise add solution C to solution B, and stir to obtain solution E; S4. Dissolve Na2S in degassed water to obtain solution D, under the protection of inert gas, dropwise add solution E to solution D to obtain a black solution; S5. Centrifuge the black solution to remove solid substances to obtain a solution of sodium polyacrylate-coupled biochar quantum dots dispersed with iron sulfide in solution state, which is the liquid iron sulfide-modified carbon quantum dots.

2. The preparation method according to claim 1, characterized in that: In step S1, the mass ratio of "urea and / or thiourea" to the biochar precursor is 1:1 - 30.

3. The preparation method according to claim 1, characterized in that: In step S1, the biochar precursor is prepared from solid waste in the gardening category. Preferably, the biochar precursor is prepared from Axonopus compressus. More preferably, the biochar precursor is obtained by washing the dark green Axonopus compressus, drying, pulverizing, and passing through a 60-mesh sieve.

4. The preparation method according to claim 1, wherein: In step S2, add 0.03 g or 0.06 g of sodium polyacrylate to 240 mL of water to obtain solution A, add 2 mL of the liquid biochar quantum dots to solution A, and stir and mix under the protection of inert gas to obtain solution B.

5. The preparation method according to claim 1, wherein: In step S3, dissolve 0.19 g of FeSO4·7H2O in 40 mL of degassed water to obtain solution C.

6. The preparation method according to claim 1, wherein: In step S4, dissolve 0.18 g of Na2S in 20 mL of degassed water to obtain solution D.

7. The preparation method according to claim 1, wherein: In step S5, centrifuge the black solution at 10000 rpm to remove solid substances.

8. A liquid iron sulfide-modified carbon quantum dot prepared by the preparation method according to any one of claims 1 - 7.

9. Use of the liquid ferrous sulfide modified carbon quantum dots according to claim 8 in soil improvement, characterized in that, Add the liquid iron sulfide-modified carbon quantum dots as a soil conditioner to the soil, and the liquid iron sulfide-modified carbon quantum dots adsorb and fix heavy metals and / or phosphorus in the soil.

10. The application according to claim 7, wherein: The heavy metal is at least one of cadmium, inorganic arsenic, organic arsenic, and chromium.

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