Method for treating soil heavy metal pollution by using composite biochar material

Abstract

The application discloses a method for treating heavy metal pollution in soil by using composite biochar materials and belongs to the technical field of soil treatment. The method for treating heavy metal pollution in soil by using composite biochar materials comprises the following steps: step (1), mixing the prepared composite biochar materials with the soil polluted by heavy metals, and standing for treatment to obtain pretreated soil; step (2), adding composite chitosan to the pretreated soil and mixing uniformly to obtain treated soil; and step (3), planting Pteridium aquilinum on the surface of the treated soil, removing the Pteridium aquilinum after 60-90 days of planting, and determining the concentration of heavy metals in the soil. The method can effectively remove the content of heavy metals in the soil and achieve the purpose of remediation and treatment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of heavy metal contaminated soil remediation, and particularly relates to a method for remediation of heavy metal contaminated soil by using composite biochar materials. BACKGROUND

[0002] With the acceleration of industrialization and the continuous development of urbanization, soil heavy metal pollution problems have gradually emerged, becoming an important hidden danger affecting environmental quality and human health. Traditional soil heavy metal pollution remediation methods, such as physical remediation and chemical remediation, can reduce the content of heavy metals in soil to some extent, but often have problems such as high cost, long cycle, and easy secondary pollution. In addition, these methods are often only targeted at specific heavy metal elements, and have limited remediation effect on complex and variable soil heavy metal pollution conditions.

[0003] Composite biochar materials, as an environmentally friendly material, have shown great potential in the field of soil heavy metal pollution remediation in recent years. Biochar itself has good adsorption performance and large specific surface area, which can effectively adsorb heavy metal ions in soil. Composite biochar materials further improve their adsorption capacity and selectivity for heavy metal ions by introducing different functional substances. Moreover, composite biochar materials have the advantages of low preparation cost, wide raw material sources, and environmental friendliness, making them have broad application prospects in the field of soil heavy metal pollution remediation.

[0004] Patent CN 105127187 B discloses a method for synergistically remediating petroleum-heavy metal contaminated soil by animals and plants-biochar. The method involves applying biochar-based fertilizer to the petroleum-heavy metal contaminated soil, mixing evenly, and aging. After aging, earthworm breeding is carried out, and then castor is planted. After the harvest of castor fruits, the castor is removed as a whole. Then, biochar-based fertilizer is applied to the petroleum-heavy metal contaminated soil again, mixed evenly, and aged. After aging, earthworm breeding is carried out, and then willow is planted. The above steps are repeated until the content of heavy metals in the soil reaches the safety standard. The invention has good remediation effect and does not cause secondary pollution to the soil. However, the method has a long remediation period, and the removal effect of heavy metals in the soil still needs to be improved. SUMMARY

[0005] The present application aims to provide a method for remediation of heavy metal contaminated soil by using composite biochar materials, to solve the technical problems of long remediation time and poor removal effect of heavy metals in the prior art.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] The application provides a method for treating heavy metal pollution in soil by using a composite biochar material, comprising the following steps:

[0008] Step (1): mixing the prepared composite biochar material with the soil polluted by heavy metals, and standing for treatment to obtain pretreated soil;

[0009] Step (2): adding the composite chitosan to the pretreated soil and uniformly mixing to obtain treated soil;

[0010] Step (3): planting Pteris spp. on the surface of the treated soil, removing the Pteris spp. after 60-90 days of planting, and determining the heavy metal concentration in the soil.

[0011] As preferred, the preparation method of the composite biochar material comprises the following steps:

[0012] Q1: drying the collected corn stalks, then cutting them into segments, soaking them in anhydrous ethanol, taking them out, drying them, then placing them in a container containing a mixed solution of concentrated sulfuric acid and distilled water, heating, cooling, washing, and drying to obtain pretreated corn stalks, then placing them in an argon environment, mixing them with potassium hydroxide, and then heating to obtain corn stalk biochar;

[0013] Q2: placing the sieved sepiolite ore in a container containing distilled water, soaking, then adding sodium pyrophosphate, stirring, suction filtering, washing, placing the filter cake in an oven for drying, and grinding to obtain sepiolite powder, then mixing the sepiolite powder with a sulfuric acid solution, oscillating to react, suction filtering, washing, drying, and grinding to obtain acidified sepiolite;

[0014] Q3: uniformly dispersing the corn stalk biochar in distilled water, ultrasonically dispersing to obtain a solution containing corn stalk biochar, adding the acidified sepiolite to the solution containing corn stalk biochar, stirring vigorously, then placing in an autoclave for heating, cooling, washing, and drying to obtain the composite biochar material.

[0015] In the above process, the corn stalks are heated and heat-treated to obtain corn stalk biochar, then the sepiolite is mixed with a sulfuric acid solution for acidification treatment to obtain acidified sepiolite, and the corn stalk biochar is mixed with the acidified sepiolite to obtain the composite biochar material.

[0016] As preferred, in the Q1, the soaking time with anhydrous ethanol is 5-8d, the ratio of the use amount of corn stalk, concentrated sulfuric acid and distilled water is (50-70)g:(90-120)mL:(10-14)mL, the heating treatment temperature is 180-200℃, the treatment time is 48-52h, the mass ratio of the pretreated corn stalk to potassium hydroxide is (1-1.3):(2-2.6), the heat treatment process is: first, heating from room temperature to 400℃ at a heating rate of 10℃ / min and keeping for 30min, then, heating from 400℃ to 800℃ at a heating rate of 10℃ / min and keeping for 2h, finally, cooling from 800℃ to 200℃ at a cooling rate of 10℃ / min and then naturally cooling to room temperature, washing with distilled water until neutral, and the drying temperature is 50-80℃ and the drying time is 10-12h.

[0017] As preferred, in the Q2, the sieving particle size is 180-200 meshes, the ratio of the use amount of sepiolite raw ore, distilled water and sodium pyrophosphate is (5-10)g:(50-100)mL:(1.5-3)g, the soaking time is 20-24h, stirring at a speed of 300rpm and 800rpm for 1h and 2h respectively, the drying temperature is 60-70℃, the drying time is 12-14h, the ratio of the use amount of sepiolite powder and sulfuric acid solution is (3-5)g:(45-75)mL, the volume fraction of the sulfuric acid solution is 13vt%, the oscillation reaction time is 10-12h, the drying temperature is 80-90℃, and the time is 12-14h; in the Q3, the ratio of the use amount of corn stalk biochar, distilled water and acidified sepiolite is (10-20)g:(15-30)mL:(3-5)g, the ultrasonic dispersion time is 30-45min, the vigorous stirring time is 1-2h, the heating treatment temperature is 200℃, the time is 20-24h, washing with distilled water until neutral, the drying temperature is 40-50℃, and the time is 12-15h.

[0018] As preferred, in the step (1), the ratio of the use amount of the composite biochar material and the soil contaminated by heavy metals is (30-40)g:(10-20)kg, and the standing treatment time is 7-14d.

[0019] As preferred, the preparation method of the composite chitosan comprises the following steps:

[0020] S1: placing chitosan in a container containing isopropyl alcohol, magnetically stirring, mixing sodium hydroxide with ultrapure water and then adding to the container, continuously adding isopropyl alcohol, water-bath heating and magnetic stirring, then dissolving chloroacetic acid in isopropyl alcohol, adding to the container in several times, heating and stirring, filtering, washing, drying, and obtaining modified chitosan;

[0021] S2: adding aminopropyltriethoxysilane into ultrapure water for dissolution, then adding modified chitosan for oscillation, subsequently, adding glutaraldehyde for crosslinking, centrifuging, filtering, washing, drying to obtain a crosslinking product, mixing a ferric chloride hexahydrate solution with the crosslinking product, oscillating reaction, after the reaction is completed, centrifuging, washing, drying to obtain a composite chitosan.

[0022] In the above process, the preparation reaction of the composite chitosan is as follows:

[0023]

[0024] Preferably, in the S1, the amount ratio of chitosan, the first added isopropyl alcohol, sodium hydroxide, ultrapure water, the second added isopropyl alcohol, chloroacetic acid and isopropyl alcohol for dissolving chloroacetic acid is (3-3.5) g:(75-80) mL:(8.15-8.25) g:(10-12) mL:(10-12) mL:(14.4-15.1) g:(20-24) mL, the magnetic stirring time is 0.5-1 h, the water bath heating temperature is 50-60℃, the magnetic stirring time is 1-2 h, the addition is in four times, one time every 5 min, the heating and stirring temperature is 50-55℃, the stirring time is 4-6 h, the washing is performed with anhydrous ethanol, and the drying temperature is 60-70℃ and the time is 10-12 h.

[0025] Preferably, in the S2, the amount ratio of aminopropyltriethoxysilane, ultrapure water, modified chitosan, glutaraldehyde and a ferric chloride hexahydrate solution is (1-2) mL:(25-50) mL:(0.5-1.0) g:(0.5-1) mL:(50-60) mL, the oscillation frequency is 250-300 rpm, the oscillation time is 1-2 h, the crosslinking time is 5-8 min, the mass fraction of the ferric chloride hexahydrate solution is 4 wt%, the oscillation frequency is 250-300 rpm, the reaction time is 1-2 h, the washing is performed with ultrapure water, the drying temperature is 60-80℃, and the drying time is 10-12 h.

[0026] Preferably, in the step (2), the amount ratio of the composite chitosan and the pretreated soil is (50-100) g:(5-10) kg.

[0027] In summary, due to the adoption of the above technical solutions, the present application has the following beneficial effects:

[0028] 1. The present application first uses corn stalks and sepiolite as raw materials to prepare a composite biochar material, and then uses chitosan, chloroacetic acid, aminopropyl triethoxysilane and ferric chloride hexahydrate as raw materials to prepare a composite chitosan, and the composite biochar material and the composite chitosan are added to the soil contaminated by heavy metals, the synergistic effect of the two can effectively adsorb heavy metals, and then the Pteris vittata is planted on the surface of the soil to further reduce the content of heavy metals in the soil, so as to achieve the purpose of treating soil heavy metal pollution.

[0029] 2. The present application composites corn stalk biochar and acidified sepiolite to obtain a composite biochar material, which is used in heavy metal contaminated soil, not only can reduce the content of heavy metals, but also can increase the stability of heavy metals, reduce the migration and bioavailability in the soil environment, and the acidification process of acidified sepiolite increases the interlayer spacing and surface acidity of sepiolite in the process of removing impurities, so that the adsorption performance is enhanced, and the acidified sepiolite and the corn stalk biochar composite form a composite biochar material with larger specific surface area and more abundant pore structure after being compounded, thereby providing more adsorption sites, and more effectively adsorbing heavy metal ions in the soil through electrostatic action, ion exchange and surface complexation.

[0030] 3. The present application uses chitosan, chloroacetic acid, aminopropyl triethoxysilane and ferric chloride hexahydrate as raw materials to prepare a composite chitosan, which is used in the repair and treatment of heavy metal soil, can effectively reduce the content of heavy metals, and the iron ions contained in the composite chitosan can enhance its stability, so that it is not easy to be degraded or damaged in the process of adsorbing heavy metal ions, prolonging the service life, and the presence of iron ions can also change the surface charge and polarity of the composite chitosan, affecting the diffusion and migration of heavy metal ions on its surface, and improving the adsorption rate. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0032] Embodiment 1

[0033] The present embodiment discloses a preparation method of a composite biochar material, comprising the following steps:

[0034] Q1: 60 g of corn stalks collected were dried, then cut into sections, soaked in anhydrous ethanol for 7 days, taken out, dried, and then placed in a container containing a mixture of 100 mL of concentrated sulfuric acid and 12 mL of distilled water, heated at 180℃ for 48 h, cooled, washed, and dried to obtain pretreated corn stalks. Then, 12 g of pretreated corn stalks were placed in an argon environment and mixed with 24 g of potassium hydroxide for heat treatment. The heat treatment process was as follows: first, the temperature was raised from room temperature to 400℃ at a rate of 10℃ / min and maintained for 30 min, then the temperature was raised from 400℃ to 800℃ at a rate of 10℃ / min and maintained for 2 h, finally the temperature was lowered from 800℃ to 200℃ at a rate of 10℃ / min and naturally cooled to room temperature. After the treatment was completed, the sample was washed with distilled water until it was neutral, dried at 80℃ for 10 h, and corn stalk biochar was obtained;

[0035] Q2: 7.5 g of raw sepiolite sieved to 200 mesh was placed in a container containing 75 mL of distilled water, soaked for 24 h, then 2.5 g of sodium pyrophosphate was added, stirred at 300 rpm and 800 rpm for 1 h and 2 h respectively, filtered, washed, and the filter cake was dried in a 70℃ oven for 12 h. Grinding obtained sepiolite powder, then 4 g of sepiolite powder was mixed with 65 mL of 13 vt% sulfuric acid solution, and the mixture was shaken for 12 h. After the reaction was completed, the mixture was filtered, washed, and dried at 90℃ for 12 h. Grinding obtained acidified sepiolite;

[0036] Q3: 15 g of corn stalk biochar was uniformly dispersed in 22 mL of distilled water, ultrasonic dispersion for 30 min to obtain a solution containing corn stalk biochar. 4 g of acidified sepiolite was added to the solution containing corn stalk biochar, stirred vigorously for 1 h, then placed in an autoclave and heated at 200℃ for 24 h. After cooling, the sample was washed with distilled water until it was neutral, and dried at 50℃ for 12 h to obtain a composite biochar material.

[0037] The present embodiment discloses a preparation method of a composite chitosan, comprising the following steps:

[0038] S1: 3.25 g of chitosan was placed in a container containing 78 mL of isopropanol, and stirred magnetically for 1 h. Then, 8.2 g of sodium hydroxide was mixed with 11 mL of ultrapure water and added to the container. 11 mL of isopropanol was further added, and the mixture was heated in a 60℃ water bath and stirred magnetically for 2 h. Then, 14.7 g of chloroacetic acid was dissolved in 22 mL of isopropanol and added to the container in four portions, each portion being added every 5 min. The mixture was heated and stirred at 55℃ for 6 h. The mixture was filtered, washed with anhydrous ethanol, and dried at 70℃ for 10 h to obtain modified chitosan;

[0039] S2: 1.5 mL of aminopropyltriethoxysilane was added to 40 mL of ultrapure water for dissolution, then 0.75 g of modified chitosan was added, oscillated at 300 rpm for 2 h, then 0.7 g of glutaraldehyde was added and crosslinked for 5 min, centrifuged, filtered, washed, dried to obtain a crosslinked product, 55 mL of a 4wt% mass fraction of a ferric chloride hexahydrate solution was mixed with the crosslinked product, oscillated at 300 rpm for 2 h, after the reaction was completed, centrifuged, washed at 300 rpm, and dried at 60°C for 12 h to obtain a composite chitosan.

[0040] The embodiment discloses a method for treating heavy metal pollution in soil by using a composite biochar material, comprising the following steps:

[0041] Step (1): 35 g of the prepared composite biochar material was mixed with 15 kg of soil contaminated by heavy metals, and the mixture was allowed to stand for 14 d to obtain pretreated soil;

[0042] Step (2): 75 g of the composite chitosan was added to 7.5 kg of the pretreated soil, and the mixture was uniformly mixed to obtain treated soil;

[0043] Step (3): Pteris spp. was planted on the surface of the treated soil, and after 60 days of planting, the Pteris spp. was removed, and the concentration of heavy metals in the soil was determined.

[0044] Example 2

[0045] The embodiment discloses a method for preparing a composite biochar material, comprising the following steps:

[0046] Q1: 50 g of collected corn stalks were dried, then cut into sections, soaked in anhydrous ethanol for 7 d, taken out, dried, and then placed in a container containing a mixture of 90 mL of concentrated sulfuric acid and 10 mL of distilled water, heated at 180°C for 48 h, cooled, washed, and dried to obtain pretreated corn stalks. Then, 10 g of the pretreated corn stalks were placed in an argon environment, mixed with 20 g of potassium hydroxide, and then subjected to heat treatment, the heat treatment process being: first, the temperature was raised from room temperature to 400°C at a rate of 10°C / min and maintained for 30 min, then the temperature was raised from 400°C to 800°C at a rate of 10°C / min and maintained for 2 h, and finally, the temperature was lowered from 800°C to 200°C at a rate of 10°C / min and naturally cooled to room temperature. After the treatment was completed, the pretreated corn stalks were washed with distilled water until neutral, and then dried at 80°C for 10 h to obtain corn stalk biochar.

[0047] Q2: 5 g of sepiolite raw ore after sieving 200 meshes was placed in a container containing 50 mL of distilled water, soaked for 24 h, then 1.5 g of sodium pyrophosphate was added, stirred at 300 rpm and 800 rpm for 1 h and 2 h respectively, suction filtered, washed, and the filter cake was placed in a 70°C oven for drying for 12 h, ground to obtain sepiolite powder, then 3 g of sepiolite powder was mixed with 45 mL of a sulfuric acid solution with a volume fraction of 13 vt%, and the mixture was shaken for 12 h, after the reaction was completed, suction filtration, washing, drying at 90°C for 12 h, grinding, to obtain acidified sepiolite;

[0048] Q3: 10 g of corn straw biochar was uniformly dispersed in 15 mL of distilled water, and an ultrasonic dispersion was performed for 30 min to obtain a solution containing corn straw biochar, 3 g of acidified sepiolite was added to the solution containing corn straw biochar, and after being stirred vigorously for 1 h, it was placed in an autoclave and heated at 200°C for 24 h, then cooled, washed with distilled water until neutral, and dried at 50°C for 12 h to obtain a composite biochar material.

[0049] The embodiment discloses a preparation method of a composite chitosan, comprising the following steps:

[0050] S1: 3 g of chitosan was placed in a container containing 75 mL of isopropanol, and after being magnetically stirred for 1 h, 8.15 g of sodium hydroxide was mixed with 10 mL of ultrapure water and added to the container, 12 mL of isopropanol was further added, and the mixture was magnetically stirred in a 60°C water bath for 2 h, then 14.4 g of chloroacetic acid was dissolved in 20 mL of isopropanol, and the solution was added to the container in four portions, with each portion being added every 5 min, and the mixture was heated and stirred at 55°C for 6 h, then filtered, washed with anhydrous ethanol, and dried at 70°C for 10 h to obtain modified chitosan;

[0051] S2: 1 mL of aminopropyltriethoxysilane was added to 25 mL of ultrapure water for dissolution, then 0.5 g of modified chitosan was added, and the mixture was shaken at 300 rpm for 2 h, then 0.5 g of glutaraldehyde was added for crosslinking for 5 min, centrifuged, filtered, washed, and dried to obtain a crosslinked product, then 50 mL of a 4 wt% iron trichloride hexahydrate solution was mixed with the crosslinked product, and the mixture was shaken at 300 rpm for 2 h, after the reaction was completed, the mixture was centrifuged, washed at 300 rpm, and dried at 60°C for 12 h to obtain a composite chitosan.

[0052] The embodiment discloses a method for treating heavy metal pollution in soil by using a composite biochar material, comprising the following steps:

[0053] Step (1): 30 g of the prepared composite biochar material was mixed with 10 kg of soil contaminated by heavy metals, and the mixture was allowed to stand for 14 d to obtain pretreated soil;

[0054] Step (2): 50 g of the composite chitosan was added to 5 kg of the pretreated soil and mixed evenly to obtain the treated soil;

[0055] Step (3): Pteris multifida was planted on the surface of the treated soil, and after 60 days, the Pteris multifida was removed, and the concentration of heavy metals in the soil was determined.

[0056] Example 3

[0057] The present embodiment discloses a preparation method of a composite biochar material, comprising the following steps:

[0058] Q1: 70 g of collected corn stalks were dried, then cut into sections, soaked in anhydrous ethanol for 7 days, taken out, dried, and then placed in a container containing a mixture of 120 mL of concentrated sulfuric acid and 14 mL of distilled water, heated at 180℃ for 48 h, cooled, washed, and dried to obtain pretreated corn stalks. Then, 13 g of the pretreated corn stalks were placed in an argon environment, mixed with 25 g of potassium hydroxide, and then heat-treated. The heat treatment process was as follows: first, the temperature was raised from room temperature to 400℃ at a rate of 10℃ / min and maintained for 30 min, then the temperature was raised from 400℃ to 800℃ at a rate of 10℃ / min and maintained for 2 h, and finally the temperature was lowered from 800℃ to 200℃ at a rate of 10℃ / min and naturally cooled to room temperature. After the treatment was completed, the sample was washed with distilled water until it was neutral, and then dried at 80℃ for 10 h to obtain corn stalk biochar;

[0059] Q2: 10 g of sepiolite raw ore sieved to 200 mesh was placed in a container containing 100 mL of distilled water, soaked for 24 h, then 3 g of sodium pyrophosphate was added, and stirred at speeds of 300 rpm and 800 rpm for 1 h and 2 h respectively, then filtered, washed, and the filter cake was dried in an oven at 70℃ for 12 h, and then ground to obtain sepiolite powder. Then, 5 g of the sepiolite powder was mixed with 75 mL of a sulfuric acid solution with a volume fraction of 13 vt%, and the mixture was shaken for 12 h. After the reaction was completed, the mixture was filtered, washed, and dried at 90℃ for 12 h, and then ground to obtain acidified sepiolite.

[0060] Q3: 20 g of corn stalk biochar was uniformly dispersed in 30 mL of distilled water, and ultrasonic dispersion was performed for 30 min to obtain a solution containing corn stalk biochar. Then, 5 g of acidified sepiolite was added to the solution containing corn stalk biochar, and stirred vigorously for 1 h, then placed in an autoclave and heated at 200℃ for 24 h. After cooling, the mixture was washed with distilled water until it was neutral, and then dried at 50℃ for 12 h to obtain a composite biochar material.

[0061] The present embodiment discloses a preparation method of a composite chitosan, comprising the following steps:

[0062] S1: 3.5 g of chitosan was placed in a container containing 80 mL of isopropyl alcohol, and after magnetic stirring for 1 h, 8.25 g of sodium hydroxide was mixed with 12 mL of ultrapure water and added to the container, followed by the addition of 10 mL of isopropyl alcohol, and then the container was heated in a 60°C water bath and stirred magnetically for 2 h. Then, 15.1 g of chloroacetic acid was dissolved in 24 mL of isopropyl alcohol and added to the container in four portions, with each portion being added every 5 min, and the container was heated and stirred at 55°C for 6 h. The mixture was filtered, washed with anhydrous ethanol, and dried at 70°C for 10 h to obtain modified chitosan;

[0063] S2: 2 mL of aminopropyltriethoxysilane was added to 50 mL of ultrapure water and dissolved, and then 1.0 g of modified chitosan was added and oscillated at 300 rpm for 2 h. Subsequently, 1.0 g of glutaraldehyde was added and cross-linked for 5 min, and then the mixture was centrifuged, filtered, washed, and dried to obtain a cross-linked product. Then, 60 mL of a 4 wt% iron trichloride hexahydrate solution was mixed with the cross-linked product, and the mixture was oscillated at 300 rpm for 2 h. After the reaction was completed, the mixture was centrifuged, washed at 300 rpm, and dried at 60°C for 12 h to obtain a composite chitosan.

[0064] The present embodiment discloses a method for treating heavy metal pollution in soil using a composite biochar material, comprising the following steps:

[0065] Step (1): 40 g of the prepared composite biochar material was mixed with 20 kg of soil contaminated with heavy metals, and the mixture was allowed to stand for 14 d to obtain pretreated soil;

[0066] Step (2): 100 g of the composite chitosan was added to 10 kg of the pretreated soil and mixed evenly to obtain treated soil;

[0067] Step (3): Pteris spp. was planted on the surface of the treated soil, and after 60-90 days of planting, the Pteris spp. was removed, and the concentration of heavy metals in the soil was determined.

[0068] Example 4

[0069] The present embodiment discloses a method for preparing a composite biochar material, comprising the following steps:

[0070] Q1: 55 g of corn stalks collected were dried, then cut into sections, soaked in anhydrous ethanol for 7 days, taken out, dried, and then placed in a container containing a mixture of 110 mL of concentrated sulfuric acid and 11 mL of distilled water, heated at 180℃ for 48 h, cooled, washed, and dried to obtain pretreated corn stalks. Then, 10.5 g of pretreated corn stalks were placed in an argon environment, mixed with 23 g of potassium hydroxide, and then heat treated. The heat treatment process was as follows: first, the temperature was raised from room temperature to 400℃ at a rate of 10℃ / min and maintained for 30 min, then the temperature was raised from 400℃ to 800℃ at a rate of 10℃ / min and maintained for 2 h, and finally the temperature was lowered from 800℃ to 200℃ at a rate of 10℃ / min and then naturally cooled to room temperature. After the treatment was completed, the sample was washed with distilled water until it was neutral, dried at 80℃ for 10 h, and then corn stalk biochar was obtained;

[0071] Q2: 8 g of raw sepiolite sieved to 200 mesh was placed in a container containing 80 mL of distilled water, soaked for 24 h, then 1.8 g of sodium pyrophosphate was added, and stirred at speeds of 300 rpm and 800 rpm for 1 h and 2 h respectively, filtered, washed, and the filter cake was dried in an oven at 70℃ for 12 h. The sepiolite powder was obtained by grinding. Then, 3.5 g of sepiolite powder was mixed with 60 mL of a 13 vt% sulfuric acid solution, and the mixture was shaken for 12 h. After the reaction was completed, the mixture was filtered, washed, and dried at 90℃ for 12 h. The acidified sepiolite was obtained by grinding.

[0072] Q3: 12 g of corn stalk biochar was uniformly dispersed in 18 mL of distilled water, and the mixture was ultrasonically dispersed for 30 min to obtain a solution containing corn stalk biochar. Then, 3.5 g of acidified sepiolite was added to the solution containing corn stalk biochar, and the mixture was stirred vigorously for 1 h and then placed in an autoclave. The mixture was heated at 200℃ for 24 h, cooled, washed with distilled water until it was neutral, and dried at 50℃ for 12 h to obtain a composite biochar material.

[0073] The present embodiment discloses a preparation method of a composite chitosan, which comprises the following steps:

[0074] S1: 3.1 g of chitosan was placed in a container containing 77 mL of isopropanol, and magnetically stirred for 1 h. Then, 8.17 g of sodium hydroxide was mixed with 10.5 mL of ultrapure water and added to the container. Then, 11.5 mL of isopropanol was added, and the mixture was magnetically stirred in a 60℃ water bath for 2 h. Then, 14.6 g of chloroacetic acid was dissolved in 23 mL of isopropanol and added to the container in four portions, with each portion being added every 5 min. The mixture was heated and stirred at 55℃ for 6 h. The mixture was filtered, washed with anhydrous ethanol, and dried at 70℃ for 10 h to obtain modified chitosan.

[0075] S2: 1.3 mL of aminopropyl triethoxysilane was added to 27 mL of ultrapure water for dissolution, then 0.6 g of modified chitosan was added, oscillated at 300 rpm for 2 h, then 0.6 g of glutaraldehyde was added and crosslinked for 5 min, centrifuged, filtered, washed, dried to obtain a crosslinked product, 52 mL of a 4 wt% mass fraction of a ferric chloride hexahydrate solution was mixed with the crosslinked product, oscillated at 300 rpm for 2 h, after the reaction was completed, centrifuged, washed at 300 rpm, and dried at 60°C for 12 h to obtain a composite chitosan.

[0076] The embodiment discloses a method for treating heavy metal pollution in soil by using a composite biochar material, comprising the following steps:

[0077] Step (1): 32 g of the prepared composite biochar material was mixed with 12 kg of soil contaminated by heavy metals, and the mixture was allowed to stand for 14 d to obtain pretreated soil;

[0078] Step (2): 80 g of the composite chitosan was added to 6 kg of the pretreated soil, and the mixture was uniformly mixed to obtain treated soil;

[0079] Step (3): Pteris spp. was planted on the surface of the treated soil, and after 60-90 days of planting, the Pteris spp. was removed, and the concentration of heavy metals in the soil was determined.

[0080] Comparative Example 1

[0081] Comparative Example 1 and Example 1 are compared, and in the preparation of the composite biochar material of Comparative Example 1, sepiolite is not added, and other conditions remain unchanged.

[0082] Comparative Example 2

[0083] Comparative Example 2 and Example 1 are compared, and in the preparation of the composite biochar material of Comparative Example 2, the sepiolite is not acidified, and other conditions remain unchanged.

[0084] Comparative Example 3

[0085] Comparative Example 3 and Example 1 are compared, and in the preparation of the composite chitosan of Comparative Example 3, chloroacetic acid is not added, and other conditions remain unchanged.

[0086] Comparative Example 4

[0087] Comparative Example 4 and Example 1 are compared, and in the preparation of the composite chitosan of Comparative Example 4, aminopropyl triethoxysilane is not added, and other conditions remain unchanged.

[0088] Comparative Example 5

[0089] Comparative Example 5 and Example 1 are compared, and in the preparation of the composite chitosan of Comparative Example 5, ferric chloride hexahydrate is not added, and other conditions remain unchanged.

[0090] Comparative Example 6

[0091] Comparative Example 6 is compared with Example 1, and in the process of treating heavy metal contaminated soil, no composite biochar material is added in Comparative Example 6, and other conditions are unchanged.

[0092] Comparative Example 7

[0093] Comparative Example 7 is compared with Example 1, and in the process of treating heavy metal contaminated soil, no composite chitosan is added in Comparative Example 7, and other conditions are unchanged.

[0094] Comparative Example 8

[0095] Comparative Example 8 is compared with Example 1, and in the process of treating heavy metal contaminated soil, no Pteris spp. is planted in Comparative Example 8, and other conditions are unchanged.

[0096] The methods of Examples 1-4 and Comparative Examples 1-8 are used to treat heavy metal contaminated soil, and the heavy metal ions in the soil are measured according to DB13 / T5396-2021, and the test results are shown in Table 1:

[0097] Table 1

[0098]

[0099] As can be seen from the test results in Table 1, the method of Examples 1-4 of the present application can effectively treat heavy metal pollution in soil. As can be seen from the comparison of Comparative Example 1 and Examples 1-4, adding sepiolite can effectively reduce the content of heavy metals in soil; as can be seen from the comparison of Comparative Example 2 and Examples 1-4, acidizing sepiolite can effectively reduce the content of heavy metals in soil; as can be seen from the comparison of Comparative Example 3 and Examples 1-4, adding chloroacetic acid can effectively reduce the content of heavy metals in soil; as can be seen from the comparison of Comparative Example 4 and Examples 1-4, adding aminopropyl triethoxysilane can effectively reduce the content of heavy metals in soil; as can be seen from the comparison of Comparative Example 5 and Examples 1-4, adding iron trichloride hexahydrate can effectively reduce the content of heavy metals in soil; as can be seen from the comparison of Comparative Example 6 and Examples 1-4, adding composite biochar material can effectively reduce the content of heavy metals in soil; as can be seen from the comparison of Comparative Example 7 and Examples 1-4, adding composite chitosan can effectively reduce the content of heavy metals in soil; as can be seen from the comparison of Comparative Example 8 and Examples 1-4, planting Pteris spp. can effectively reduce the content of heavy metals in soil.

[0100] The above description is only a preferred embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent replacements or changes within the technical scope disclosed in the present application and the inventive concept of the present application, which should be covered within the protection scope of the present application.

[0101] The preferred embodiments of the application disclosed above are only to help explain the application. The preferred embodiments are not intended to limit the application to specific embodiments. Obviously, many modifications and variations are possible in light of the above teachings. The preferred embodiments are chosen and described in order to provide the best explanation of the principles and their applications. Those skilled in the art will understand and appreciate that the application is practiced with the claimed scope and equivalents thereof.

Claims

1. A method for remediation of heavy metal contaminated soil using a composite biochar material, characterized in that, The method comprises the following steps: Step (1): corn straw and sepiolite are used as raw materials to prepare a composite biochar material, which is mixed with soil contaminated by heavy metals, and the mixture is left to stand to obtain pretreated soil; Step (2): the composite chitosan is added to the pretreated soil and mixed uniformly to obtain treated soil; Step (3): Pteris spp. is planted on the surface of the treated soil, and after 60-90 days of planting, the Pteris spp. is removed, and the concentration of heavy metals in the soil is determined; The preparation method of the composite chitosan comprises the following steps: S1: the chitosan is placed in a container containing isopropyl alcohol, and after magnetic stirring, sodium hydroxide and ultrapure water are mixed and added to the container, isopropyl alcohol is continuously added, and water bath heating and magnetic stirring are performed, then chloroacetic acid is dissolved in isopropyl alcohol and added to the container in portions, heating and stirring are performed, filtration, washing and drying are performed to obtain modified chitosan; S2: the aminopropyl triethoxysilane is dissolved in ultrapure water, then the modified chitosan is added for oscillation, and then glutaraldehyde is added for crosslinking, centrifugation, filtration, washing and drying are performed to obtain a crosslinked product, and the crosslinked product is mixed with a solution of ferric chloride hexahydrate, oscillation reaction is performed, after the reaction is completed, centrifugation, washing and drying are performed to obtain the composite chitosan.

2. The method for remediation of heavy metal contaminated soil using composite biochar material according to claim 1, characterized in that, The preparation method of the composite biochar material comprises the following steps: Q1: the collected corn straw is dried, then cut into sections, soaked in anhydrous ethanol, taken out, dried, placed in a container containing a mixed solution of concentrated sulfuric acid and distilled water, heated, cooled, washed, and dried to obtain pretreated corn straw, then the pretreated corn straw is placed in an argon environment, mixed with potassium hydroxide, and heated to obtain corn straw biochar; Q2: the sieved sepiolite ore is placed in a container containing distilled water, soaked, sodium pyrophosphate is added, stirred, suction filtered, washed, and the filter cake is placed in an oven for drying and grinding to obtain sepiolite powder, which is then mixed with a sulfuric acid solution, oscillation reaction is performed, after the reaction is completed, suction filtration, washing and drying are performed, and grinding is performed to obtain acidified sepiolite; Q3: the corn straw biochar is uniformly dispersed in distilled water, ultrasonic dispersion is performed to obtain a solution containing corn straw biochar, the acidified sepiolite is added to the solution containing corn straw biochar, and after vigorous stirring, the mixture is placed in an autoclave for heating treatment, cooled, washed, and dried to obtain a composite biochar material.

3. The method for remediation of heavy metal contaminated soil using composite biochar material according to claim 2, characterized in that, In the Q1, the soaking time with anhydrous ethanol is 5-8 days, the ratio of the use amount of corn stalk, concentrated sulfuric acid and distilled water is (50-70) g:(90-120) mL:(10-14) mL, the heating treatment temperature is 180-200 ℃, the treatment time is 48-52 h, the mass ratio of pretreated corn stalk to potassium hydroxide is (1-1.3):(2-2.6), the heat treatment process is: first, the temperature is raised from room temperature to 400 ℃ at a rate of 10 ℃ / min and kept for 30 min, then, the temperature is raised from 400 ℃ to 800 ℃ at a rate of 10 ℃ / min and kept for 2 h, finally, the temperature is lowered from 800 ℃ to 200 ℃ at a rate of 10 ℃ / min and naturally cooled to room temperature, washed with distilled water until neutral, and the drying temperature is 50-80 ℃ and the drying time is 10-12 h.

4. The method for remediation of heavy metal contaminated soil using composite biochar material according to claim 2, characterized in that, In the Q2, the sieved particle size is 180-200 meshes, the ratio of the use amount of sepiolite raw ore, distilled water and sodium pyrophosphate is (5-10) g:(50-100) mL:(1.5-3) g, the soaking time is 20-24 h, the stirring speed is 300 rpm and 800 rpm respectively for 1 h and 2 h, the drying temperature is 60-70 ℃, the drying time is 12-14 h, the ratio of the use amount of sepiolite powder to sulfuric acid solution is (3-5) g:(45-75) mL, the volume fraction of sulfuric acid solution is 13 vt%, the oscillation reaction time is 10-12 h, the drying temperature is 80-90 ℃, and the time is 12-14 h; in the Q3, the ratio of the use amount of corn stalk biochar, distilled water and acidified sepiolite is (10-20) g:(15-30) mL:(3-5) g, the ultrasonic dispersion time is 30-45 min, the vigorous stirring time is 1-2 h, the heating treatment temperature is 200 ℃, and the time is 20-24 h, the distilled water is used to wash until neutral, the drying temperature is 40-50 ℃, and the time is 12-15 h.

5. The method for remediation of heavy metal contaminated soil using composite biochar material according to claim 1, characterized in that, In the step (1), the ratio of the use amount of composite biochar material to heavy metal contaminated soil is (30-40) g:(10-20) kg, and the standing treatment time is 7-14 days.

6. The method for remediation of heavy metal contaminated soil using composite biochar material according to claim 1, characterized in that, In the S1, the ratio of the use amount of chitosan, first added isopropyl alcohol, sodium hydroxide, ultrapure water, second added isopropyl alcohol, chloroacetic acid and isopropyl alcohol for dissolving chloroacetic acid is (3-3.5) g:(75-80) mL:(8.15-8.25) g:(10-12) mL:(10-12) mL:(14.4-15.1) g:(20-24) mL, the magnetic stirring time is 0.5-1 h, the water bath heating temperature is 50-60 ℃, the magnetic stirring time is 1-2 h, the chitosan is added in four times, one time every 5 min, the heating stirring temperature is 50-55 ℃, the stirring time is 4-6 h, the anhydrous ethanol is used for washing, the drying temperature is 60-70 ℃, and the time is 10-12 h.

7. The method for remediation of heavy metal contaminated soil using composite biochar material according to claim 1, characterized in that, In the S2, the amount ratio of aminopropyltriethoxysilane, ultrapure water, modified chitosan, glutaraldehyde and ferric chloride hexahydrate solution is (1-2) mL:(25-50) mL:(0.5-1.0) g:(0.5-1) mL:(50-60) mL, the oscillation frequency is 250-300 rpm, the oscillation time is 1-2 h, the crosslinking time is 5-8 min, the mass fraction of ferric chloride hexahydrate solution is 4 wt%, the oscillation frequency is 250-300 rpm, the reaction time is 1-2 h, the washing is performed with ultrapure water, the drying temperature is 60-80 ℃, and the drying time is 10-12 h. 8.The method for treating heavy metal pollution in soil with composite biochar material according to claim 1, characterized in that, In the step (2), the amount ratio of the composite chitosan and the pretreated soil is (50-100) g:(5-10) kg.

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