Soil heavy metal passivator containing selenium-modified biochar as well as preparation method and application of soil heavy metal passivator

Abstract

The invention belongs to the technical field of heavy metal repair, and particularly relates to a soil heavy metal passivator containing selenium modified charcoal and a preparation method and application of the soil heavy metal passivator. According to the soil heavy metal passivator based on the selenium-modified biochar, the biochar is modified through the selenium element, the selenium element loaded on the biochar achieves effective adsorption of mercury, arsenic and cadmium in soil through the synergistic effect of the selenium element loaded on the biochar and organic functional groups of the biochar, and the selenium element loaded on the biochar and the biochar achieve the synergistic effect; effective adsorption of part of cadmium, arsenic and mercury is realized, effective fixation of arsenic, mercury and cadmium in soil is finally realized, and the fixation efficiency is high. The invention further provides application of the selenium modified charcoal soil heavy metal passivator obtained by the scheme or the selenium modified charcoal soil heavy metal passivator obtained by the preparation method in remediation of soil mercury pollution, soil arsenic pollution and soil cadmium pollution. The selenium modified charcoal soil heavy metal passivator disclosed by the invention can be directly added into soil to effectively fix arsenic, mercury and cadmium.

Description

Technical Field

[0001] The present invention belongs to the technical field of heavy metal remediation, and particularly relates to a soil heavy metal passivator of selenium-modified biochar, a preparation method thereof, and an application thereof. Background Art

[0002] As an important natural resource, the safety of soil has become increasingly important. Currently, common pollutants in soil include various heavy metals, including mercury, chromium, cadmium, lead, and arsenic, etc. Among them, mercury is highly toxic and causes great harm to crops and workers. Cadmium has extremely strong enrichment properties and has certain toxicity and carcinogenicity. Therefore, how to remove mercury pollution and cadmium pollution in soil is a difficult problem faced by this field.

[0003] Currently, the remediation methods for mercury, cadmium, and arsenic contaminated soil mainly include soil washing method, thermal desorption method, and in-situ passivation method, etc. Among them, the in-situ passivation method is simple in operation and low in cost, and has been recognized by people. However, limited by the performance of the passivator, the soil remediation effect of the in-situ passivation method is generally poor, and it is difficult to effectively fix heavy metal pollution in soil. Summary of the Invention

[0004] The purpose of the present invention is to provide a soil heavy metal passivator of selenium-modified biochar, a preparation method thereof, and an application thereof. The soil heavy metal passivator of selenium-modified biochar provided by the present invention can effectively fix arsenic, mercury, and cadmium in soil.

[0005] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a soil heavy metal passivator of selenium-modified biochar, including biochar, selenium elements loaded and fixed in the pores of the biochar, and selenium elements fixed on the outer surface of the biochar.

[0007] Preferably, the mass ratio of the biochar to the selenium elements loaded and fixed in the pores of the biochar is 1×10 3 : 1.5 - 8.72.

[0008] Preferably, the mass ratio of the biochar to the selenium elements fixed on the outer surface of the biochar is 1×10 3 : 1.11 - 3.75.

[0009] Preferably, the thickness of the selenium elements fixed on the outer surface of the biochar is 5 - 12 Å.

[0010] Preferably, the particle size of the soil heavy metal passivator of selenium-modified biochar is 0.01 - 2.5 mm.

[0011] The present invention also provides a preparation method of the soil heavy metal passivator of selenium-modified biochar as described in the above scheme, including the following steps:

[0012] Mix a selenium source and biomass, granulate them after carbonization in a supercritical carbon dioxide fluid device to obtain a soil heavy metal passivator of selenium-modified biochar; the temperature of the supercritical carbon dioxide fluid device is controlled at 28-31 °C, and the pressure is controlled at 5.38-7.38 MPa.

[0013] Preferably, the selenium source includes one or more of selenol, selenoether, and ore selenium.

[0014] Preferably, the carbonization includes first carbonization, second carbonization, and third carbonization in sequence; the temperature of the first carbonization is 100-300 °C, and the heat preservation time is 0.5-1 h; the temperature of the second carbonization is 300-500 °C, and the heat preservation time is 0.5-1 h; the temperature of the third carbonization is 500-700 °C, and the heat preservation time is 2-3 h.

[0015] Preferably, the mass ratio of the selenium source to the biomass is 2-15:1×10 4 ~3×10 4 .

[0016] The present invention also provides the application of the soil heavy metal passivator of the selenium-modified biochar described in the above scheme or the soil heavy metal passivator of the selenium-modified biochar obtained by the preparation method described in the above scheme in the remediation of soil mercury pollution, soil arsenic pollution, or soil cadmium pollution.

[0017] The present invention provides a soil heavy metal passivator of selenium-modified biochar. The soil heavy metal passivator of selenium-modified biochar provided by the present invention uses selenium elements to modify biochar. The selenium elements in the biochar pores achieve effective adsorption and fixation of mercury, arsenic, and cadmium in the soil through synergistic action with the organic functional groups in the biochar pores. The selenium elements on the outer surface of the biochar act synergistically with the biochar to achieve effective adsorption and fixation of part of the mercury, arsenic, and cadmium in the soil, and finally effectively passivate the activities of arsenic, mercury, and cadmium in the soil, with good passivation effects.

[0018] The present invention also provides a preparation method for the soil heavy metal passivator of the selenium-modified biochar described in the above scheme. The preparation method provided by the present invention has simple steps, convenient operation, high feasibility, and is suitable for large-scale industrial production.

[0019] The present invention also provides the application of the soil heavy metal passivator of the selenium-modified biochar described in the above scheme or the soil heavy metal passivator of the selenium-modified biochar obtained by the preparation method described in the above scheme in the remediation of mercury-polluted soil, arsenic-polluted soil, or cadmium-polluted soil. The soil heavy metal passivator of selenium-modified biochar provided by the present invention is convenient to use. It can directly be added to the soil to effectively passivate arsenic, mercury, and cadmium, reducing the labor cost and having broad application prospects. Specific Embodiments

[0020] The present invention provides a soil heavy metal passivator of selenium-modified biochar, which comprises biochar, selenium elements fixed in the pores of the biochar, and selenium elements fixed on the outer surface of the biochar.

[0021] The soil heavy metal passivator of selenium-modified biochar provided by the present invention comprises biochar; the particle size of the biochar is preferably 0.1 - 2 mm, more preferably 0.5 - 1.5 mm, and further preferably 0.8 - 1.2 mm.

[0022] The soil heavy metal passivator of selenium-modified biochar provided by the present invention comprises selenium elements fixed in the pores of the biochar; the mass ratio of the biochar to the selenium elements fixed in the pores of the biochar is preferably 1×10 3 : 1.5 - 8.72, more preferably 1×10 3 : 1.89 - 5.44, and further preferably 1×10 3 : 2.31 - 3.11.

[0023] The soil heavy metal passivator of selenium-modified biochar provided by the present invention comprises selenium elements fixed on the outer surface of the biochar; the mass ratio of the biochar to the selenium elements fixed on the outer surface of the biochar is preferably 1×10 3 : 1.11 - 3.75, more preferably 1×10 3 : 1.76 - 3.22, and further preferably 1×10 3 : 2.45 - 2.56.

[0024] In the present invention, the particle size of the soil heavy metal passivator of selenium-modified biochar is preferably 0.01 - 2.5 mm, more preferably 0.03 - 2.3 mm, and further preferably 0.05 - 2.1 mm.

[0025] The soil heavy metal passivator of selenium-modified biochar provided by the present invention modifies the biochar with selenium elements. The selenium elements in the pores of the biochar, through the synergistic effect with the organic functional groups in the pores of the biochar, realize the effective adsorption and fixation of mercury, arsenic and cadmium in the soil. The selenium elements on the outer surface of the biochar and the biochar act synergistically to realize the effective adsorption and fixation of part of mercury, arsenic and cadmium in the soil, and finally realize the effective passivation of mercury, arsenic and cadmium in the soil, and the passivation effect is good.

[0026] The present invention also provides a preparation method of the soil heavy metal passivator of selenium-modified biochar according to the above scheme, which comprises the following steps:

[0027] Mix a selenium source and biomass, carry out carbonization in a carbon dioxide supercritical fluid device and then granulate to obtain a soil heavy metal passivator of selenium-modified biochar; the temperature of the carbon dioxide supercritical fluid device is controlled at 28-31 °C, and the pressure is controlled at 5.38-7.38 MPa.

[0028] In the present invention, a selenium source and biomass are mixed. In the present invention, the selenium source preferably includes one or more of selenol, selenoether and ore selenium, more preferably ore selenium; the selenol preferably includes one or both of methyl selenol and ethyl selenol; the selenoether preferably includes one or both of dimethyl selenide and diethyl diselenide.

[0029] In the present invention, the biomass preferably includes one or more of rice straw, rice husk and wood chips.

[0030] In the present invention, the mass ratio of the selenium source to the biomass is preferably 2-15:1×10 4 ~3×10 4 , more preferably 4-11:1.2×10 4 ~2.8×10 4 ,further preferably 7-8:1.5×10 4 ~2.6×10 4 .

[0031] After mixing, in the present invention, the obtained mixture is carbonized in a carbon dioxide supercritical fluid device and then granulated to obtain a soil heavy metal passivator of selenium-modified biochar. In the present invention, the carbonization preferably includes first carbonization, second carbonization and third carbonization in sequence.

[0032] In the present invention, the temperature of the first carbonization is preferably 100-300 °C, more preferably 140-250 °C, further preferably 170-200 °C, and the heat preservation time is preferably 0.5-1 h, more preferably 0.6-0.9 h, further preferably 0.75 h.

[0033] In the present invention, the temperature of the second carbonization is preferably 300-500 °C, more preferably 340-470 °C, further preferably 370-420 °C, and the heat preservation time is preferably 0.5-1 h, more preferably 0.7-0.9 h, further preferably 0.8 h.

[0034] In the present invention, the temperature of the third carbonization is preferably 500-700 °C, more preferably 580-670 °C, further preferably 610-640 °C, and the heat preservation time is preferably 2-3 h, more preferably 2.2-2.4 h, further preferably 2.3 h.

[0035] In the present invention, the granulation is preferably crushing; the target particle size of the granulation is preferably 0.01 - 0.5 mm.

[0036] The present invention also provides the application of the soil heavy metal passivator of the selenium-modified biochar described in the above solution or the soil heavy metal passivator of the selenium-modified biochar obtained by the preparation method described in the above solution in the remediation of soil arsenic pollution, soil mercury pollution or soil cadmium pollution.

[0037] In the present invention, the application preferably includes the following steps: applying the soil heavy metal passivator of the selenium-modified biochar to the contaminated soil; the contaminated soil is mercury-contaminated soil, arsenic-contaminated soil or cadmium-contaminated soil.

[0038] In the present invention, the ratio of the mass of the soil heavy metal passivator of the selenium-modified biochar to the dry weight of the contaminated soil is preferably 1 - 8:1000, more preferably 2.33 - 7.21:1000, further preferably 3.45 - 6.34:1000, and even more preferably 4.34 - 5.01:1000.

[0039] The soil heavy metal passivator of the selenium-modified biochar provided by the present invention is convenient to use. It can directly be added to the soil to effectively remove mercury, arsenic and cadmium, reducing the labor cost and having broad application prospects.

[0040] To further illustrate the present invention, the solutions of the present invention will be described in detail below in conjunction with examples, but they cannot be construed as limiting the protection scope of the present invention.

[0041] Example 1

[0042] This example provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.01 mm), and the mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 :1.5, the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 :1.11, and the thickness of the selenium element fixed on the outer surface of the biochar is 5 Å.

[0043] The preparation method of the soil heavy metal passivator of the selenium-modified biochar in this example includes the following steps:

[0044] Mix methaneselenol and rice straw, and the mass ratio of methaneselenol to rice straw is 2:1×10 4 , carry out first carbonization at 300 °C for 1 h, second carbonization at 500 °C for 1 h, third carbonization at 700 °C for 2 h in supercritical carbon dioxide fluid in sequence, and then granulate to obtain the soil heavy metal passivator of selenium-modified biochar.

[0045] Example 2

[0046] This embodiment provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.01 mm), and the mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 :1.5, and the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 :1.76, and the thickness of the selenium element fixed on the outer surface of the biochar is 5.3 Å.

[0047] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this embodiment includes the following steps:

[0048] Mix dimethyl selenide and rice straw, and the mass ratio of dimethyl selenide to rice straw is 2:1×10 4 , and successively carry out the first carbonization at 200 °C for 0.5 h, the second carbonization at 400 °C for 0.5 h, the third carbonization at 600 °C for 2.5 h in supercritical carbon dioxide fluid, and then granulate to obtain the soil heavy metal passivator of selenium-modified biochar.

[0049] Example 3

[0050] This embodiment provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.02 mm), and the mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 :1.5, and the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 :2.45, and the thickness of the selenium element fixed on the outer surface of the biochar is 8.4 Å.

[0051] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this embodiment includes the following steps:

[0052] Mix ore selenium and rice straw, and the mass ratio of ore selenium to biomass is 15:2×10 4 , and successively carry out the first carbonization at 200 °C for 0.5 h, the second carbonization at 300 °C for 1 h, the third carbonization at 550 °C for 2.5 h in supercritical carbon dioxide fluid, and then granulate to obtain the soil heavy metal passivator of selenium-modified biochar.

[0053] Example 4

[0054] This embodiment provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.02 mm), and the mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 :1.5, and the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3: 2.56, and the thickness of the selenium element fixed on the outer surface of the biochar is 9.1 Å.

[0055] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this example includes the following steps:

[0056] Mix ethyl selenol and rice husk, and the mass ratio of ethyl selenol to rice husk is 5:1×10 4 , and carry out first carbonization at 300 °C for 0.6 h, second carbonization at 400 °C for 2 h, and third carbonization at 500 °C for 2.2 h in supercritical carbon dioxide fluid in sequence, and then granulate to obtain the soil heavy metal passivator of selenium-modified biochar.

[0057] Example 5

[0058] This example provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.05 mm), and the mass ratio of biochar to the selenium element fixed in the pores of the biochar is 1×10 3 : 1.89, and the mass ratio of biochar to the selenium element fixed on the outer surface of the biochar is 1×10 3 : 3.22, and the thickness of the selenium element fixed on the outer surface of the biochar is 11 Å.

[0059] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this example includes the following steps:

[0060] Mix methyl selenol and wood chips, and the mass ratio of methyl selenol to wood chips is 8:1×10 4 , and carry out first carbonization at 250 °C for 1 h, second carbonization at 350 °C for 1 h, and third carbonization at 550 °C for 2.1 h in supercritical carbon dioxide fluid in sequence, and then granulate to obtain the soil heavy metal passivator of selenium-modified biochar.

[0061] Example 6

[0062] This example provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.05 mm), and the mass ratio of biochar to the selenium element fixed in the pores of the biochar is 1×10 3 : 1.89, and the mass ratio of biochar to the selenium element fixed on the outer surface of the biochar is 1×10 3 : 3.22, and the thickness of the selenium element fixed on the outer surface of the biochar is 11 Å.

[0063] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this example includes the following steps:

[0064] Mix dimethyl selenide and rice husk, and the mass ratio of dimethyl selenide to rice husk is 12:1×10 4, first carbonization is carried out in supercritical carbon dioxide fluid at 150 °C for 0.8 h, second carbonization at 450 °C for 0.5 h, third carbonization at 600 °C for 2 h, and then granulation is carried out to obtain a soil heavy metal passivator of selenium-modified biochar.

[0065] Example 7

[0066] This example provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.1 mm), and the mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 : 1.89, and the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 : 3.75, and the thickness of the selenium element fixed on the outer surface of the biochar is 12 Å.

[0067] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this example includes the following steps:

[0068] Mix dimethyl selenide and wood chips, and the mass ratio of dimethyl selenide to wood chips is 15:1×10 4 , first carbonization is carried out in supercritical carbon dioxide fluid at 270 °C for 1 h, second carbonization at 420 °C for 1 h, third carbonization at 650 °C for 2.5 h, and then granulation is carried out to obtain a soil heavy metal passivator of selenium-modified biochar.

[0069] Example 8

[0070] This example provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.1 mm), and the mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 : 1.89, and the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 : 3.75, and the thickness of the selenium element fixed on the outer surface of the biochar is 12 Å.

[0071] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this example includes the following steps:

[0072] Mix ore selenium and rice husks, and the mass ratio of ore selenium to rice husks is 2:2×10 4 , first carbonization is carried out in supercritical carbon dioxide fluid at 200 °C for 0.5 h, second carbonization at 500 °C for 0.7 h, third carbonization at 600 °C for 2 h, and then granulation is carried out to obtain a soil heavy metal passivator of selenium-modified biochar.

[0073] Example 9

[0074] This embodiment provides a soil heavy metal passivator of selenium-modified biochar (particle size: 0.15 mm). The mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 : 2.31, and the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 : 1.76. The thickness of the selenium element fixed on the outer surface of the biochar is 6 Å.

[0075] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this embodiment includes the following steps:

[0076] Mix methylselenol and rice straw. The mass ratio of methylselenol to rice straw is 3:1.9×10 4 , and carry out first carbonization at 220 °C for 0.5 h, second carbonization at 440 °C for 1 h, and third carbonization at 600 °C for 2 h in supercritical carbon dioxide fluid in sequence, and then granulate to obtain the soil heavy metal passivator of selenium-modified biochar.

[0077] Example 10

[0078] This embodiment provides a soil heavy metal passivator of selenium-modified biochar (particle size: 0.15 mm). The mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 : 2.31, and the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 : 1.76. The thickness of the selenium element fixed on the outer surface of the biochar is 6.2 Å.

[0079] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this embodiment includes the following steps:

[0080] Mix methylselenol and rice straw. The mass ratio of methylselenol to rice straw is 15:1×10 4 , and carry out first carbonization at 280 °C for 1 h, second carbonization at 480 °C for 0.8 h, and third carbonization at 550 °C for 2.5 h in supercritical carbon dioxide fluid in sequence, and then granulate to obtain the soil heavy metal passivator of selenium-modified biochar.

[0081] Example 11

[0082] This embodiment provides a soil heavy metal passivator of selenium-modified biochar (particle size: 0.2 mm). The mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 : 2.31, and the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 : 2.45. The thickness of the selenium element fixed on the outer surface of the biochar is 7.3 Å.

[0083] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this embodiment includes the following steps:

[0084] Mix dimethyl selenide and rice husks, and the mass ratio of dimethyl selenide to rice husks is 10:2×10 4 , and carry out first carbonization in supercritical carbon dioxide fluid at 300 °C for 0.5 h, second carbonization at 500 °C for 1 h, third carbonization at 600 °C for 2.5 h, and then granulate to obtain the soil heavy metal passivator of selenium-modified biochar.

[0085] Example 12

[0086] This embodiment provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.2 mm), and the mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 : 3.11, and the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 : 2.45, and the thickness of the selenium element fixed on the outer surface of the biochar is 7.7 Å.

[0087] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this embodiment includes the following steps:

[0088] Mix ore selenium and rice husks, and the mass ratio of ore selenium to rice husks is 9:1×10 4 , and carry out first carbonization in supercritical carbon dioxide fluid at 230 °C for 1 h, second carbonization at 320 °C for 0.9 h, third carbonization at 570 °C for 2.1 h, and then granulate to obtain the soil heavy metal passivator of selenium-modified biochar.

[0089] Example 13

[0090] This embodiment provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.25 mm), and the mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 : 3.11, and the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 : 2.56, and the thickness of the selenium element fixed on the outer surface of the biochar is 8.1 Å.

[0091] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this embodiment includes the following steps:

[0092] Mix dimethyl selenide and rice straw, and the mass ratio of dimethyl selenide to rice straw is 7:1×10 4, first carbonization is carried out in supercritical carbon dioxide fluid at 130 °C for 1 h, second carbonization at 440 °C for 0.75 h, third carbonization at 580 °C for 2.5 h, and then granulation is carried out to obtain a soil heavy metal passivator of selenium-modified biochar.

[0093] Example 14

[0094] This example provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.25 mm), and the mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 : 3.11, the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 : 2.56, and the thickness of the selenium element fixed on the outer surface of the biochar is 8.5 Å.

[0095] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this example includes the following steps:

[0096] Mix dimethyl selenide and rice straw, and the mass ratio of dimethyl selenide to rice straw is 6:1×10 4 , first carbonization is carried out in supercritical carbon dioxide fluid at 200 °C for 0.5 h, second carbonization at 400 °C for 1 h, third carbonization at 550 °C for 2.5 h, and then granulation is carried out to obtain a soil heavy metal passivator of selenium-modified biochar.

[0097] Example 15

[0098] This example provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.3 mm), and the mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 : 5.44, the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 : 3.22, and the thickness of the selenium element fixed on the outer surface of the biochar is 10.5 Å.

[0099] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this example includes the following steps:

[0100] Mix dimethyl selenide and rice straw, and the mass ratio of dimethyl selenide to rice straw is 5:1×10 4 , first carbonization is carried out in supercritical carbon dioxide fluid at 200 °C for 0.5 h, second carbonization at 500 °C for 1 h, third carbonization at 650 °C for 2.5 h, and then granulation is carried out to obtain a soil heavy metal passivator of selenium-modified biochar.

[0101] Example 16

[0102] This embodiment provides a soil heavy metal passivator of selenium-modified biochar (particle size: 0.3 mm), and the mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 :5.44, and the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 :3.22, and the thickness of the selenium element fixed on the outer surface of the biochar is 10.9 Å.

[0103] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this embodiment includes the following steps:

[0104] Mix dimethyl selenide and rice straw, and the mass ratio of dimethyl selenide to rice straw is 4:1×10 4 , and successively perform first carbonization at 200 °C for 0.5 h, second carbonization at 500 °C for 0.5 h, and third carbonization at 700 °C for 2.5 h in supercritical carbon dioxide fluid, and then granulate to obtain the soil heavy metal passivator of selenium-modified biochar.

[0105] Example 17

[0106] This embodiment provides a soil heavy metal passivator of selenium-modified biochar (particle size: 0.4 mm), and the mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 :5.44, and the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3 :3.75, and the thickness of the selenium element fixed on the outer surface of the biochar is 11.4 Å.

[0107] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this embodiment includes the following steps:

[0108] Mix dimethyl selenide and rice straw, and the mass ratio of dimethyl selenide to rice straw is 3:1×10 4 , and successively perform first carbonization at 300 °C for 1 h, second carbonization at 500 °C for 1 h, and third carbonization at 700 °C for 2 h in supercritical carbon dioxide fluid, and then granulate to obtain the soil heavy metal passivator of selenium-modified biochar.

[0109] Example 18

[0110] This embodiment provides a soil heavy metal passivator of selenium-modified biochar (particle size: 0.4 mm), and the mass ratio of biochar to selenium element fixed in the pores of the biochar is 1×10 3 :8.72, and the mass ratio of biochar to selenium element fixed on the outer surface of the biochar is 1×10 3: 3.75, the thickness of the selenium element fixed on the outer surface of the biochar is 11.1 Å.

[0111] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this example includes the following steps:

[0112] Mix dimethyl selenide and rice straw, and the mass ratio of dimethyl selenide to rice straw is 2:1×10 4 , carry out first carbonization in supercritical carbon dioxide fluid at 300 °C for 1 h, second carbonization at 500 °C for 1 h, third carbonization at 600 °C for 2 h, and then granulate to obtain the soil heavy metal passivator of selenium-modified biochar.

[0113] Example 19

[0114] This example provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.5 mm), and the mass ratio of biochar to the selenium element fixed in the pores of the biochar is 1×10 3 : 8.72, and the mass ratio of biochar to the selenium element fixed on the outer surface of the biochar is 1×10 3 : 3.75, and the thickness of the selenium element fixed on the outer surface of the biochar is 11.7 Å.

[0115] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this example includes the following steps:

[0116] Mix dimethyl selenide and rice straw, and the mass ratio of dimethyl selenide to rice straw is 13:1×10 4 , carry out first carbonization in supercritical carbon dioxide fluid at 200 °C for 1 h, second carbonization at 370 °C for 1 h, third carbonization at 600 °C for 2 h, and then granulate to obtain the soil heavy metal passivator of selenium-modified biochar.

[0117] Example 20

[0118] This example provides a soil heavy metal passivator of selenium-modified biochar (particle size is 0.5 mm), and the mass ratio of biochar to the selenium element fixed in the pores of the biochar is 1×10 3 : 8.72, and the mass ratio of biochar to the selenium element fixed on the outer surface of the biochar is 1×10 3 : 3.75, and the thickness of the selenium element fixed on the outer surface of the biochar is 11.9 Å.

[0119] The preparation method of the soil heavy metal passivator of selenium-modified biochar in this example includes the following steps:

[0120] Mix dimethyl selenide and rice straw, and the mass ratio of dimethyl selenide to rice straw is 14:1×104 , first carbonization is carried out in supercritical carbon dioxide fluid, heat preservation is carried out at 240 °C for 1 h, second carbonization, heat preservation is carried out at 450 °C for 1 h, third carbonization, heat preservation is carried out at 600 °C for 2 h, and then granulation is carried out to obtain a soil heavy metal passivator of selenium-modified biochar.

[0121] Test Example 1

[0122] Detect the initial contents of mercury in mercury-contaminated soil and cadmium in cadmium-contaminated soil, and then apply 1 g of the soil heavy metal passivator of selenium-modified biochar prepared in Example 1 to mercury-contaminated soil (dry weight is 1000 g) and cadmium-contaminated soil (dry weight is 1000 g) respectively, age for 30 days, detect the contents of mercury in mercury-contaminated soil and cadmium in cadmium-contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate and cadmium activity passivation rate. The results are shown in Table 1.

[0123] Table 1 Heavy metal passivation efficiency of Test Example 1

[0124] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 35.89％ 45.42％ 42.55％

[0125] Test Example 2

[0126] Detect the initial contents of mercury in mercury-contaminated soil and cadmium in cadmium-contaminated soil, and then apply 3 g of the soil heavy metal passivator of selenium-modified biochar prepared in Example 2 to mercury-contaminated soil (dry weight is 1000 g) and cadmium-contaminated soil (dry weight is 1000 g) respectively, age for 30 days, detect the contents of mercury in mercury-contaminated soil and cadmium in cadmium-contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate and cadmium activity passivation rate. The results are shown in Table 2.

[0127] Table 2 Heavy metal passivation efficiency of Test Example 2

[0128] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 36.76 46.47 45.51

[0129] Test Example 3

[0130] Detect the initial contents of mercury in mercury-contaminated soil and cadmium in cadmium-contaminated soil, and then apply 5 g of the soil heavy metal passivator of selenium-modified biochar prepared in Example 3 to mercury-contaminated soil (dry weight is 1000 g) and cadmium-contaminated soil (dry weight is 1000 g) respectively, age for 30 days, detect the contents of mercury in mercury-contaminated soil and cadmium in cadmium-contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate and cadmium activity passivation rate. The results are shown in Table 3.

[0131] Table 3 Heavy metal passivation efficiency of Test Example 3

[0132] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 37.85 47.36 42.45

[0133] Test Example 4

[0134] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 7 g of the soil heavy - metal passivator of selenium - modified biochar prepared in Example 4 to the mercury - contaminated soil (dry weight is 1000 g) and the cadmium - contaminated soil (dry weight is 1000 g) respectively. Age for 30 days, detect the contents of mercury in the mercury - contaminated soil and cadmium in the cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 4.

[0135] Table 4 Heavy - metal passivation efficiency of Test Example 4

[0136] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 38.25 46.11 47.94

[0137] Test Example 5 [[ID=!0]]

[0138] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 8 g of the soil heavy - metal passivator of selenium - modified biochar prepared in Example 5 to the mercury - contaminated soil (dry weight is 1000 g) and the cadmium - contaminated soil (dry weight is 1000 g) respectively. Age for 30 days, detect the contents of mercury in the mercury - contaminated soil and cadmium in the cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 5.

[0139] Table 5 Heavy - metal passivation efficiency of Test Example 5

[0140] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 37.78 47.78 45.17

[0141] Test Example 6

[0142] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 6 g of the soil heavy - metal passivator of selenium - modified biochar prepared in Example 6 to the mercury - contaminated soil (dry weight is 1000 g) and the cadmium - contaminated soil (dry weight is 1000 g) respectively. Age for 30 days, detect the contents of mercury in the mercury - contaminated soil and cadmium in the cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 6.

[0143] Table 6 Heavy - metal passivation efficiency of Test Example 6

[0144] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 38.28 44.93 46.31

[0145] Test Example 7

[0146] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 4 g of the soil heavy - metal passivator of selenium - modified biochar prepared in Example 7 to the mercury - contaminated soil (dry weight is 1000 g) and the cadmium - contaminated soil (dry weight is 1000 g) respectively. Age for 30 days, detect the contents of mercury in the mercury - contaminated soil and cadmium in the cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 7.

[0147] Table 7 Heavy metal passivation efficiency of Test Example 7

[0148] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 38.20 45.36 43.57

[0149] Test Example 8

[0150] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 2 g of the soil heavy metal passivator, selenium - modified biochar prepared in Example 8, to the mercury - contaminated soil (dry weight 1000 g) and cadmium - contaminated soil (dry weight 1000 g) respectively. Age for 30 days, detect the contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 8.

[0151] Table 8 Heavy metal passivation efficiency of Test Example 8

[0152] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 37.86 47.38 47.05

[0153] Test Example 9

[0154] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 2 g of the soil heavy metal passivator, selenium - modified biochar prepared in Example 9, to the mercury - contaminated soil (dry weight 1000 g) and cadmium - contaminated soil (dry weight 1000 g) respectively. Age for 30 days, detect the contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 9.

[0155] Table 9 Heavy metal passivation efficiency of Test Example 9

[0156] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 38.09 47.19 42.85

[0157] Test Example 10

[0158] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 2 g of the soil heavy metal passivator, selenium - modified biochar prepared in Example 10, to the mercury - contaminated soil (dry weight 1000 g) and cadmium - contaminated soil (dry weight 1000 g) respectively. Age for 30 days, detect the contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 10.

[0159] Table 10 Heavy metal passivation efficiency of Test Example 10

[0160] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 38.69 48.81 48.07

[0161] Test Example 11

[0162] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 1 g of the soil heavy - metal passivator of selenium - modified biochar prepared in Example 11 to the mercury - contaminated soil (dry weight is 1000 g) and cadmium - contaminated soil (dry weight is 1000 g) respectively. Age for 30 days, detect the contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate and cadmium activity passivation rate. The results are shown in Table 11.

[0163] Table 11 Heavy - metal passivation efficiency of Test Example 11

[0164]

[0165]

[0166] Test Example 12

[0167] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 1 g of the soil heavy - metal passivator of selenium - modified biochar prepared in Example 12 to the mercury - contaminated soil (dry weight is 1000 g) and cadmium - contaminated soil (dry weight is 1000 g) respectively. Age for 30 days, detect the contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate and cadmium activity passivation rate. The results are shown in Table 12.

[0168] Table 12 Heavy - metal passivation efficiency of Test Example 12

[0169] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 37.72 47.52 47.16

[0170] Test Example 13

[0171] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 3 g of the soil heavy - metal passivator of selenium - modified biochar prepared in Example 13 to the mercury - contaminated soil (dry weight is 1000 g) and cadmium - contaminated soil (dry weight is 1000 g) respectively. Age for 30 days, detect the contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate and cadmium activity passivation rate. The results are shown in Table 13.

[0172] Table 13 Heavy - metal passivation efficiency of Test Example 13

[0173] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 37.12 47.06 43.09

[0174] Test Example 14

[0175] Detect the initial content of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 3 g of the soil heavy - metal passivator, selenium - modified biochar prepared in Example 14, to the mercury - contaminated soil (dry weight is 1000 g) and cadmium - contaminated soil (dry weight is 1000 g) respectively. Age for 30 days, detect the content of mercury in the mercury - contaminated soil and cadmium in the cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 14.

[0176] Table 14 Heavy - metal passivation efficiency of Test Example 14

[0177] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 35.82 47.34 45.35

[0178] Test Example 15

[0179] Detect the initial content of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 5 g of the soil heavy - metal passivator, selenium - modified biochar prepared in Example 15, to the mercury - contaminated soil (dry weight is 1000 g) and cadmium - contaminated soil (dry weight is 1000 g) respectively. Age for 30 days, detect the content of mercury in the mercury - contaminated soil and cadmium in the cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 15.

[0180] Table 15 Heavy - metal passivation efficiency of Test Example 15

[0181] Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 36.93 46.62 45.55

[0182] Test Example 16

[0183] Detect the initial content of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 5 g of the soil heavy - metal passivator, selenium - modified biochar prepared in Example 16, to the mercury - contaminated soil (dry weight is 1000 g) and cadmium - contaminated soil (dry weight is 1000 g) respectively. Age for 30 days, detect the content of mercury in the mercury - contaminated soil and cadmium in the cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 16.

[0184] Table 16 Heavy - metal passivation efficiency of Test Example 16

[0185] k Mercury passivation rate Cadmium passivation rate 37.92 47.31 44.28

[0186] Test Example 17

[0187] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 8 g of the soil heavy - metal passivator, selenium - modified biochar prepared in Example 17, to the mercury - contaminated soil (dry weight: 1000 g) and cadmium - contaminated soil (dry weight: 1000 g) respectively. Age for 30 days, detect the contents of mercury in the mercury - contaminated soil and cadmium in the cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 17.

[0188] Table 17 Heavy - metal passivation efficiency of Test Example 17

[0189] Arsenic passivation rate Mercury passivation rate Cadmium passivation rate 38.97 48.82 46.35

[0190] Test Example 18

[0191] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 8 g of the soil heavy - metal passivator, selenium - modified biochar prepared in Example 18, to the mercury - contaminated soil (dry weight: 1000 g) and cadmium - contaminated soil (dry weight: 1000 g) respectively. Age for 30 days, detect the contents of mercury in the mercury - contaminated soil and cadmium in the cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 18.

[0192] Table 18 Heavy - metal passivation efficiency of Test Example 18

[0193] Arsenic passivation rate Mercury passivation rate Cadmium passivation rate 36.78 46.13 45.76

[0194] Test Example 19

[0195] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 6 g of the soil heavy - metal passivator, selenium - modified biochar prepared in Example 19, to the mercury - contaminated soil (dry weight: 1000 g) and cadmium - contaminated soil (dry weight: 1000 g) respectively. Age for 30 days, detect the contents of mercury in the mercury - contaminated soil and cadmium in the cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 19.

[0196] Table 19 Heavy - metal passivation efficiency of Test Example 19

[0197] Arsenic passivation rate Mercury passivation rate Cadmium passivation rate 35.70 45.04 42.35

[0198] Test Example 20

[0199] Detect the initial contents of mercury in mercury - contaminated soil and cadmium in cadmium - contaminated soil. Then, apply 6 g of the soil heavy - metal passivator, selenium - modified biochar prepared in Example 20, to the mercury - contaminated soil (dry weight is 1000 g) and the cadmium - contaminated soil (dry weight is 1000 g) respectively. Age for 30 days, detect the contents of mercury in the mercury - contaminated soil and cadmium in the cadmium - contaminated soil, and calculate the mercury activity passivation rate, arsenic activity passivation rate, and cadmium activity passivation rate. The results are shown in Table 20.

[0200] Table 20 Heavy - metal passivation efficiency of Test Example 20

[0201] Arsenic passivation rate Mercury passivation rate Cadmium passivation rate Arsenic passivation rate 38.61 48.03 45.53

[0202] As can be seen from the above examples, the soil heavy - metal passivator of selenium - modified biochar provided by the present invention can effectively remove mercury, arsenic, and cadmium in the soil.

[0203] Although the above - mentioned examples have described the present invention in detail, they are only a part of the embodiments of the present invention, not all of them. Other embodiments can be obtained based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A soil heavy metal passivator of selenium-modified biochar, characterized in that, It includes biochar, selenium element fixed in the pores of the biochar, and selenium element fixed on the outer surface of the biochar.

2. The soil heavy metal passivator of selenium-modified biochar according to claim 1, wherein The mass ratio of the biochar to the selenium element fixed in the pores of the biochar is 1×10 3 : 1.5 to 8.

72.

3. The soil heavy metal passivator of selenium-modified biochar according to claim 1 or 2, characterized in that, The mass ratio of the biochar to the selenium element fixed on the outer surface of the biochar is 1×10 3 :1.11 to 3.

75.

4. The soil heavy metal passivator of selenium-modified biochar according to claim 1, characterized in that, The thickness of the selenium element fixed on the outer surface of the biochar is 5-12 angstroms.

5. The soil heavy metal passivator of selenium-modified biochar according to claim 1 or 4, characterized in that The particle size of the soil heavy metal passivator of the selenium-modified biochar is 0.01-2.5 mm.

6. The preparation method of the soil heavy metal passivator of selenium-modified biochar according to any one of claims 1 to 5, characterized in that, It includes the following steps: Mix the selenium element and biomass, and granulate after carbonization in a supercritical carbon dioxide fluid device to obtain the soil heavy metal passivator of the selenium-modified biochar; the temperature of the supercritical carbon dioxide fluid device is controlled at 28-31 °C, and the pressure is controlled at 5.38-7.38 MPa.

7. The preparation method according to claim 6, characterized in that, The selenium source includes one or several of selenol, selenoether, and ore selenium.

8. The preparation method according to claim 6, characterized in that, The carbonization includes first carbonization, second carbonization, and third carbonization in sequence; the temperature of the first carbonization is 100-300 °C, and the heat preservation time is 0.5-1 h; the temperature of the second carbonization is 300-500 °C, and the heat preservation time is 0.5-1 h; the temperature of the third carbonization is 500-700 °C, and the heat preservation time is 2-3 h.

9. The preparation method according to claim 6, characterized in that, The mass ratio of the selenium element to the biomass is 2 to 15: 1×10 4 ~3×10 4 .

10. Application of the soil heavy metal passivator of the selenium-modified biochar according to any one of claims 1-5 or the soil heavy metal passivator of the selenium-modified biochar obtained by the preparation method according to any one of claims 6-9 in the remediation of soil mercury pollution, soil arsenic pollution, or soil cadmium pollution.

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