Green low-carbon external admixture for contaminated soil sintered brick and preparation and application method thereof

Abstract

The present application relates to the technical field of soil remediation materials, and provides a green low-carbon external admixture for contaminated soil sintered bricks and a preparation and application method thereof.The raw materials of the external admixture include: 25-35 parts of magnesium reduction slag, 5-15 parts of pyrite slag, 5-15 parts of waste manganese slag, 2-8 parts of lignin, 2-8 parts of shell powder and / or eggshell powder, 10-20 parts of molasses, 2-8 parts of corn syrup, 15-25 parts of dry blue-green algae powder, and 5-15 parts of lithium iron phosphate waste.The external admixture can effectively reduce the sintering temperature and energy consumption of the contaminated soil for preparing sintered bricks, effectively control the multi-valence heavy metal form in the soil, reduce the secondary risk of pollutant migration in the whole production process and products, and the raw materials of the external admixture are widely sourced, the preparation and use method is simple, the synchronous reduction of energy consumption, material consumption and carbon emission is effectively realized, and the advantages of green low-carbon and "waste pollution control" are prominent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of soil remediation, and particularly relates to a green low-carbon external admixture for contaminated soil sintered brick and a preparation and application method thereof. BACKGROUND

[0002] For industrial soil remediation, the industrial contaminated site has a large stock, a large remediation volume and high treatment pressure. In addition, traditional wall materials such as sintered bricks are widely used in many fields such as building and transportation, and the material cost accounts for about 30% of the total construction cost. However, as clay is continuously consumed, the stock of related natural resources has become increasingly scarce, and it is increasingly important to develop waste-friendly and environmentally friendly wall materials. In the relevant field industry standards, the use of clean clay resources to produce sintered bricks has been limited, and alternative new building materials are encouraged.

[0003] Using contaminated soil as raw material and adopting a tunnel kiln or other methods for co-disposal to produce sintered bricks can effectively and safely dispose of heavy metal and organic matter pollution in the soil, reduce the cost of contaminated soil treatment, replace valuable clean clay resources, and improve the economy of sintered brick production. Internationally, resource utilization such as the preparation of building materials is an important way to dispose of contaminated soil at the site, which not only effectively alleviates environmental pressure but also solves the demand for space and building materials in urban construction. The safe disposal and reuse of contaminated soil sintered bricks as building materials has become one of the research hotspots in the field of domestic contaminated site remediation.

[0004] However, compared with the research on contaminated site remediation technology, the current resource recycling technology and industry development of contaminated soil for sintered brick production are not mature enough, and there are the following main problems: 1) Contaminated soil for sintered brick production still mostly uses simple addition of clean clay or coal gangue as mixed burning material for material proportioning balance, resulting in a high sintering temperature, high energy consumption, material consumption and carbon emissions; 2) In the pretreatment, aging and drying of contaminated soil, heavy metals and organic pollutants are easily migrated and diffused through dust, leakage and volatilization, which poses a great risk to the surrounding environment and human health, and the secondary pollution control is difficult; 3) In the production process, the multi-valence heavy metals in the soil are easy to maintain high toxicity and high mobility, and the possibility of re-dissolution in finished bricks is large, and the environmental safety is questionable. Therefore, whether a new environmentally friendly external admixture that can effectively control the form of multi-valence heavy metals in soil, reduce the sintering temperature and effectively inhibit the secondary pollution risk in the whole process can be developed is a bottleneck technical problem that needs to be solved in the field of resource utilization of contaminated soil for sintered brick production. SUMMARY

[0005] In order to overcome the deficiencies of the prior art, the purpose of the present application is to provide a green low-carbon external admixture for contaminated soil sintered brick and its preparation and application method, which can effectively reduce the sintering temperature and energy consumption of contaminated soil for preparing sintered brick, effectively control the multi-valence heavy metal form in the soil, reduce the secondary risk of pollutant migration in the whole production process and product, and at the same time, the raw material source of the external admixture is extensive, the preparation and use method is simple, and the synchronous reduction of energy consumption, material consumption and carbon emission is effectively realized, and the advantages of green low-carbon and 'waste pollution control' are prominent.

[0006] In a first aspect of the present application, a green low-carbon external admixture for contaminated soil sintered brick is provided, and the green low-carbon external admixture comprises the following component raw materials in parts by weight: 25-35 parts of magnesium reduction slag, 5-15 parts of pyrite slag, 5-15 parts of waste manganese slag, 2-8 parts of lignin, 2-8 parts of shell powder and / or eggshell powder, 10-20 parts of molasses, 2-8 parts of corn syrup, 15-25 parts of dry cyanobacteria powder, and 5-15 parts of lithium iron phosphate waste.

[0007] Optionally, the lignin is papermaking waste lignin, and the molasses is sugar industry waste molasses.

[0008] In a second aspect of the present application, a preparation method of the green low-carbon external admixture for contaminated soil sintered brick is provided, comprising the following steps:

[0009] S101: After the magnesium reduction slag, the pyrite slag and the waste manganese slag are stirred and uniformly mixed, water is added and stirred to form a mixed slurry A;

[0010] S102: After the cyanobacteria is washed, freeze-dried, ground and sieved, it is dry-mixed with the lignin, and stirred to form a mixed solid powder B;

[0011] S103: The lithium iron phosphate waste and the mixed solid powder B are added into the mixed slurry A, heated and activated, then pyrolyzed to complete dryness under the protection of a nitrogen atmosphere, and ground and sieved to obtain a mixed solid powder C;

[0012] S104: The molasses, the corn syrup, the shell powder and / or the eggshell powder are stirred and mixed, dried, ground and sieved to obtain a mixed solid powder D;

[0013] S105: The mixed solid powder C and the mixed solid powder D are dry-mixed to obtain the green low-carbon external admixture.

[0014] Optionally, the heating and activation in the step S103 is heating to 80 DEG C and microwave activation.

[0015] Optionally, the pyrolysis in the step S103 is heating at 300 DEG C.

[0016] Optionally, the drying in the step S104 is drying at 65 DEG C until the water content is ≤3%.

[0017] In a third aspect, the application provides the use of the green low-carbon admixture or the green low-carbon admixture prepared by the preparation method in the repair of contaminated soil.

[0018] Optionally, the application method comprises adding the green low-carbon admixture to the contaminated soil to prepare the sintered brick.

[0019] Optionally, the preparation method of the sintered brick comprises:

[0020] S201: adding water to the contaminated soil to be treated so that the water content of the contaminated soil is 3 times the liquid limit of the contaminated soil, to obtain a contaminated slurry to be treated;

[0021] S202: adding the green low-carbon admixture to the contaminated slurry to be treated, and stirring to mix uniformly to form a mixed slurry E;

[0022] S203: vibrating and sieving the mixed slurry E to remove large particles with a particle size greater than 2 mm to obtain a mixed slurry F;

[0023] S204: adding the green low-carbon admixture to the mixed slurry F again, stirring to mix uniformly, and then standing to age to obtain an aged material;

[0024] S205: transporting the aged material to a brick machine, extruding the aged material into a brick blank through an extruder, and cutting the brick blank;

[0025] S206: after stacking the brick blank, the brick blank enters a sintered brick tunnel kiln, is dried, and is sintered;

[0026] S207: naturally cooling the sintered brick blank to obtain a sintered brick product.

[0027] Optionally, the drying temperature is 110°C, and the drying time is 8h.

[0028] Optionally, the sintering temperature is 600-700°C.

[0029] Optionally, the sintering time is 6-8h.

[0030] Optionally, the green low-carbon admixture in step S202 is added in an amount of 15-25% by weight.

[0031] Optionally, the green low-carbon admixture in step S204 is added in an amount of 25-35% by weight.

[0032] The admixture of this invention can effectively reduce the content of hexavalent chromium in contaminated soil, converting it into low-toxicity trivalent chromium, and effectively control the risk of secondary pollution throughout the sintering and brick-making process of contaminated soil. Through the optimization of the raw material formula, the sintering temperature can be reduced. At the same time, the raw materials are widely available, with biomass and industrial waste as the main components, effectively realizing the safe disposal and utilization of solid waste resources. Furthermore, the preparation and application process is simple, which can significantly reduce the energy and material consumption throughout the process. The sintered brick products prepared can also fix carbon and resist acid rain erosion, with outstanding green and low-carbon advantages. Detailed Implementation

[0033] This invention provides a green and low-carbon admixture for sintered bricks made from contaminated soil. The green and low-carbon admixture comprises the following raw materials by weight: 25-35 parts magnesium reduction slag, 5-15 parts pyrite slag, 5-15 parts waste manganese slag, 2-8 parts lignin, 2-8 parts shell powder and / or eggshell powder, 10-20 parts molasses, 2-8 parts corn steep liquor, 15-25 parts cyanobacteria powder, and 5-15 parts lithium iron phosphate waste.

[0034] In some implementation schemes, the aforementioned raw materials can make full use of industrial waste.

[0035] Specifically, the magnesium reduction slag is a solid waste generated from the production of industrial metallic magnesium using the Pidgeon process; pyrite slag refers to the waste residue generated from roasting pyrite during the industrial production of sulfuric acid; and waste manganese slag refers to the solid waste obtained by soaking manganese ore powder in sulfuric acid and then separating the solid and liquid components during the industrial production of manganese.

[0036] The 2-8 parts of shell powder and / or eggshell powder may be 2-8 parts of shell powder alone, or 2-8 parts of eggshell powder alone, or a mixture of shell powder and eggshell powder totaling 2-8 parts.

[0037] The cyanobacteria powder mentioned above can be obtained by freeze-drying fresh cyanobacteria harvested from rivers and lakes and then grinding them.

[0038] The lithium iron phosphate waste mentioned above refers to the positive electrode material in a fully discharged lithium-ion battery.

[0039] The lignin can be lignin from papermaking waste, mainly referring to lignin byproducts obtained from the separation of cellulose from plants in the pulp and paper industry; the molasses can be waste molasses from the sugar industry, mainly the waste liquid generated in the washing, boiling and vacuum filtration processes of industrial sugar making, containing abundant sucrose, invert sugar, colloids and other reducing substances; the corn steep liquor can be a yellowish-brown liquid made by concentrating the soaking liquid after soaking corn kernels in sulfurous acid during the industrial production of corn starch, containing abundant reducing sugars and other solid substances.

[0040] The preparation method of the green low-carbon external admixture includes some embodiments of preferred parameter settings such as activation, pyrolysis, drying and the like, and mainly includes the following steps:

[0041] S101. After the magnesium reduction slag, pyrite slag and waste manganese slag are stirred and uniformly mixed, clean tap water is added and mechanically stirred to form a mixed slurry A;

[0042] S102. After the blue-green algae is washed, freeze-dried, ground and sieved, a blue-green algae dry powder is formed, which is dry-mixed with papermaking waste lignin to form a mixed solid powder B;

[0043] S103. The lithium iron phosphate waste and the mixed solid powder B obtained in step S102 are added to the mixed slurry A obtained in step S101, heated to 80 DEG C and microwave-activated, then dried at 300 DEG C under the protection of a nitrogen atmosphere, and ground and sieved to obtain a mixed solid powder C;

[0044] S104. Molasses, corn syrup and shell powder are artificially stirred and mixed, dried at 65 DEG C to a water content of less than or equal to 3%, and then ground and sieved to 200 mesh to obtain a mixed solid powder D;

[0045] S105. The mixed solid powder C obtained in step S103 and the mixed solid powder D obtained in step S104 are dry-mixed by hand and packaged in a moisture-proof manner to obtain the final green low-carbon external admixture.

[0046] The application also provides the use of the above-mentioned green low-carbon external admixture in soil remediation. The use method includes but is not limited to mixing the external admixture into contaminated soil to promote the change of the valence state of the heavy metal pollutants in the contaminated soil and the weakening of the toxicity, improve the adsorption and solidification capacity of the pollutants in the soil, etc.

[0047] In some embodiments, the use method is to use the green low-carbon external admixture as a material in the preparation process of contaminated soil sintered bricks to help the contaminated soil to be made into sintered brick products to achieve solidification and remediation of the contaminated soil.

[0048] In some more specific embodiments, the green low-carbon external admixture and the contaminated soil to be remediated are used as raw materials to prepare sintered bricks, and the method includes the following steps:

[0049] S201. Clean tap water is added to the contaminated soil to be treated to make the water content in the soil about 3 times the liquid limit to prepare a contaminated slurry to be treated;

[0050] S202. The green low-carbon external admixture is added to the contaminated slurry and stirred and mixed uniformly to form a mixed slurry E;

[0051] S203. The mixed mud E is vibrated and sieved to remove large particles such as gravel and construction waste with a particle size greater than 2 mm, to obtain mixed mud F;

[0052] S204. Green low-carbon admixture is added to the mixed mud F again, and after artificial stirring and uniform mixing, it is placed and aged for 24 hours to obtain aged material;

[0053] S205. The aged material after standing and aging is transported to the brick machine, extruded by the extruder, and cut into a brick billet according to the specified size;

[0054] S206. After the brick billet obtained in step S205 is stacked, it enters the tunnel kiln for sintered brick, wherein the drying section temperature is 110 DEG C for 8 hours, and the sintering section sintering temperature is 600-700 DEG C for 6 hours;

[0055] S207. The sintered brick billet is naturally cooled and packaged to obtain the final harmless sintered brick product.

[0056] The green low-carbon admixture of the present application is applied to the preparation of sintered brick from contaminated soil, which can effectively reduce the sintering temperature and energy consumption of sintered brick prepared from contaminated soil, effectively control the form of multi-valence heavy metals in soil, reduce the secondary risk of pollutant migration in the whole production process and product, and the raw material source of the admixture is wide, the preparation and use method is simple, and the synchronous reduction of energy consumption, material consumption and carbon emission is realized, and the advantages of green low-carbon and "waste pollution control" are prominent.

[0057] More specifically, the beneficial effects of the present application also include:

[0058] (1) The main components of the green low-carbon admixture of the present application include biomass waste (molasses, shell powder, corn syrup, etc.), industrial and mining waste (magnesium reduction slag, pyrite slag, waste manganese slag, etc.), and battery waste (lithium iron phosphate waste), the raw material source is wide, realizes the effective reuse of solid waste resources, can effectively reduce material consumption, realize resource saving, and the preparation process is simple, easy to prepare and use.

[0059] (2) The magnesium reduction slag, pyrite slag and waste manganese slag components in the green low-carbon admixture can significantly reduce the sintering temperature of soil sintered brick after being mixed with soil under the activation of lithium iron phosphate waste, from more than 1000 DEG C to 600-700 DEG C, significantly reducing the energy consumption of the sintering process, and also effectively achieving the purpose of not destroying the carbon components in the soil and the product during sintering.

[0060] (3)The added molasses and corn steep liquor material effectively reduces the heavy metals in the soil, enabling the heavy metals to be converted from high-toxicity high-valence state to low-toxicity low-valence state, and further realizing the adsorption of heavy metal elements in the soil under the combined action of lithium iron phosphate waste and shell powder and eggshell powder, thereby reducing the secondary pollution risk of contaminated soil production and preparation of sintered bricks due to dusting, leachate leakage and the like.

[0061] (4)The blue-green algae powder and papermaking waste lignin in the green low-carbon external additive raw material can effectively adsorb organic pollutants in the contaminated soil through the material micropore structure and surface functional groups after being added to the contaminated soil, thereby avoiding the risk of volatile pollution in the whole process, and generating biochar components with high carbon adsorption performance and high acid buffering capacity at a relatively low sintering temperature (600-700 DEG C), which can significantly improve the long-term safety performance of sintered brick products, such as acid rain erosion resistance, and the sintered brick products can adsorb CO2 in the air to realize the capture and fixation of carbon in the environment.

[0062] (5)The preparation method of the green low-carbon external additive mainly comprises stirring, low-temperature drying, grinding and sieving, and has the advantages of simple operation, low preparation cost, and the like, and only needs to be added to the contaminated soil in the process of use, thereby ensuring the environmental effect and product performance, and having small energy consumption and outstanding economic and social comprehensive benefits.

[0063] Examples 1-9

[0064] Examples 1-9 are respectively carried out according to the data in Table 1 below.

[0065] Table 1 Numerical summary table of examples 1-9

[0066] Embodiments Value a Value b Value c 1 25：5：5：8：8：20：8：25：15 15％ 25％ 2 25：5：5：8：8：20：8：25：15 20％ 30％ 3 25：5：5：8：8：20：8：25：15 25％ 35％ 4 35：15：15：2：2：10：2：15：5 15％ 25％ 5 35：15：15：2：2：10：2：15：5 20％ 30％ 6 35：15：15：2：2：10：2：15：5 25％ 35％ 7 30：10：10：5：5：15：5：20：10 15％ 25％ 8 30：10：10：5：5：15：5：20：10 20％ 30％ 9 30：10：10：5：5：15：5：20：10 25％ 35％

[0067] Note:

[0068] (1) The value a is the relative weight percentage of magnesium reduction slag, pyrite slag, waste manganese slag, papermaking waste lignin, shell and / or eggshell powder, molasses, corn steep liquor, blue-green algae dry powder and lithium iron phosphate waste in sequence;

[0069] (2) The value b and the value c are respectively the mixing amount of the green low-carbon external additive in the preparation of the mixed mud and the preparation of the aging material in the weight percentage.

[0070] The magnesium reduction slag is collected from the magnesium slag yard of a magnesium metal enterprise in Yulin, Shaanxi, the pyrite slag is collected from a sulfuric acid plant in Suzhou, and the waste manganese slag is purchased from a manganese slag plant in Chizhou, Anhui.

[0071] Table 2 Composition table of magnesium reduction slag, pyrite slag and waste manganese slag

[0072]

[0073] The lithium iron phosphate waste powder was collected from a company in Ganzhou, Jiangxi Province, and its main components (mass percentage) were as follows: Li 3.55%, Fe 28.43%, P 15.75%, Al 1.53%, and other components 50.74%.

[0074] The lignin was obtained from a plant processing factory in Luohe City, Henan Province, and was a yellow-brown, powdery solid with a certain aromatic odor, which contained about 60-80% lignin and its derivatives, a small amount of cellulose, and water.

[0075] The total sugar content in the waste molasses was 43%, of which the sucrose content was 24%, the alcohol concentration was 8%, and the water content was 49%.

[0076] The corn syrup used in the examples had a reducing sugar content of 4.6%.

[0077] 1.1 Artificially prepared contaminated soil

[0078] For the collected clay, chromium nitrate (Cr 6+) and hexachlorobenzene were used as exogenous pollutants, representing heavy metals and organic pollutants, respectively, to prepare artificially contaminated soil, in which the addition concentrations of hexavalent chromium (Cr 6+ ) and hexachlorobenzene were 4000 mg / kg and 800 mg / kg, respectively.

[0079] 1.2 Preparation of green low-carbon external admixture

[0080] According to the weight parts given in Table 1, the corresponding total amounts of magnesium reduction slag, pyrite slag, waste manganese slag, papermaking waste lignin, shell powder, eggshell powder, sugar industry waste molasses, corn syrup, dry cyanobacteria powder, and lithium iron phosphate waste were weighed.

[0081] (1) After the magnesium reduction slag, pyrite slag, and waste manganese slag were stirred and mixed uniformly, clean tap water was added in a liquid-solid ratio of 1:1, and then mechanical stirring was performed to form a mixed slurry A;

[0082] (2) After the obtained cyanobacteria was washed and freeze-dried at -30°C, it was ground by a ball mill and then sieved through a 200-mesh sieve. The sieved cyanobacteria powder was dry-mixed with the papermaking waste lignin according to the proportion, and stirring was performed to form a mixed solid powder B;

[0083] (3) The lithium iron phosphate waste and the mixed solid powder B were added to the mixed slurry A, heated to 80°C, and microwave-activated for 2 h. Then, under the protection of a nitrogen atmosphere, the mixture was heated to complete drying at 300°C, and then the dried solid was ground through a 150-mesh sieve to obtain a mixed solid powder C;

[0084] (4) Mix molasses, corn steep liquor and shell powder by hand, dry at 65℃ until the water content is less than or equal to 3%, and then grind through a 200-mesh sieve to obtain mixed solid powder D;

[0085] (5) Mix mixed solid powder C and mixed solid powder D by hand, and then seal and package to obtain green low-carbon external admixture.

[0086] 1.3 Preparation of contaminated soil sintered brick

[0087] (1) Add clean tap water to the contaminated soil to be treated so that the water content in the soil is about 3 times the liquid limit, to prepare contaminated slurry to be treated;

[0088] (2) Add green low-carbon external admixture to the contaminated slurry, with an addition amount of value b, and mix by hand to obtain mixed slurry E;

[0089] (3) Vibrate the mixed slurry E to remove large particles such as gravel and construction waste with a particle size greater than 2 mm to obtain mixed slurry F;

[0090] (4) Add green low-carbon external admixture to the mixed slurry F, with an addition amount of value c, and mix by hand to obtain aged material after aging for 24 hours;

[0091] (5) Transport the aged material to a brick machine, extrude it into a brick billet through an extruder, and cut it into a brick billet according to the specified size;

[0092] (6) After the brick billet obtained in step (5) is stacked, it is put into a sintered brick tunnel kiln, with a drying section temperature of 110℃ for 8 hours and a sintering section sintering temperature of 600-700℃ for 6 hours;

[0093] (7) Naturally cool the sintered brick billet and obtain the final harmless sintered brick product.

[0094] 1.4 Process detection and product detection

[0095] During the preparation of the contaminated soil sintered brick, a handheld photoionization detector (PID) is used to detect the concentration of volatile organic pollutants in the ambient air, and the concentration peak value is used as the basis for judging the influence of air pollution. Meanwhile, the brick billet before entering the tunnel kiln and the sintered brick product after entering the tunnel kiln are collected, the valence state of heavy metals and the total amount of pollutants are analyzed, and the Cr 6+The total chromium proportion and the hexachlorobenzene residual rate, wherein the hexachlorobenzene residual rate is obtained by dividing the total concentration value of hexachlorobenzene in the brick blank before entering the tunnel kiln by the corresponding added concentration value of hexachlorobenzene in the artificially prepared soil; in addition, for the sintered brick product, a 200-ton hydraulic press is carried out to carry out the compressive strength detection; and the solid waste leaching toxicity detection method of sulfuric acid and nitric acid method (HJ / T 299-2007) is used to carry out the pollutant leaching toxicity detection in the sintered brick.

[0096] Comparative Examples 1-6

[0097] No external admixture of the application is added in the sintered brick preparation process of each comparative example. The specific process is as follows:

[0098] Comparative Example 1: The artificially prepared hexavalent chromium contaminated soil is mixed with clean clay and coal gangue in a mass ratio of 75:15:10, and after adding a water content of 16%, it is aged for 24 hours, then pressed into a brick blank, and then enters the tunnel kiln for firing, wherein the drying environment is dried at 110℃ for 6 hours, and the sintering link is fired at 1000℃ for 8 hours.

[0099] Comparative Example 2: The artificially prepared hexachlorobenzene contaminated soil is mixed with clean clay and coal gangue in a mass ratio of 75:15:10, and after adding a water content of 16%, it is aged for 24 hours, then pressed into a brick blank, and then enters the tunnel kiln for firing, wherein the drying environment is dried at 110℃ for 6 hours, and the sintering link is fired at 1000℃ for 8 hours.

[0100] Comparative Example 3: The artificially prepared hexavalent chromium contaminated soil is mixed with clean clay and coal gangue in a mass ratio of 75:15:10, and after adding a water content of 16%, it is aged for 24 hours, then pressed into a brick blank, and then enters the tunnel kiln for firing, wherein the drying environment is dried at 110℃ for 6 hours, and the sintering link is fired at 850℃ for 8 hours.

[0101] Comparative Example 4: The artificially prepared hexachlorobenzene contaminated soil is mixed with clean clay and coal gangue in a mass ratio of 75:15:10, and after adding a water content of 16%, it is aged for 24 hours, then pressed into a brick blank, and then enters the tunnel kiln for firing, wherein the drying environment is dried at 110℃ for 6 hours, and the sintering link is fired at 850℃ for 8 hours.

[0102] Comparative Example 5: The artificially prepared hexavalent chromium contaminated soil is mixed with clean clay and coal gangue in a mass ratio of 75:15:10, and after adding a water content of 16%, it is aged for 24 hours, then pressed into a brick blank, and then enters the tunnel kiln for firing, wherein the drying environment is dried at 110℃ for 6 hours, and the sintering link is fired at 650℃ for 6 hours.

[0103] Comparative Example 6: The artificially prepared hexachlorobenzene contaminated soil was mixed with clean clay and coal gangue in a mass ratio of 75:15:10, and after adding 16% moisture content, it was aged for 24 hours, then pressed into a brick body, and then put into a tunnel kiln for firing, wherein the drying environment was 110°C for 6 hours, and the sintering section was 650°C for 6 hours.

[0104] The above example and comparative example test results are summarized in Table 3.

[0105] Table 3: Comparison of test data of Examples 1-9 and Comparative Examples 1-6

[0106]

[0107]

[0108] As can be seen from Table 3, the green low-carbon external additive in the present application can effectively reduce the content of highly toxic hexavalent chromium in chromium-contaminated soil, and the heavy metal Cr 6+ in the sintered brick product is also significantly lower than that of Comparative Example 1, and the compressive strength is slightly higher than that of Comparative Example 1; the green low-carbon external additive in the present application can effectively control the volatilization and diffusion of hexachlorobenzene into the atmosphere during the sintering process, and the residual rate of hexachlorobenzene in the brick body before entering the tunnel kiln is more than 93%, which is significantly higher than 42.33% of Comparative Example 2, proving that the external additive of the present application can effectively control the volatilization and diffusion of hexachlorobenzene into the atmosphere during the sintering process, and the sintered product does not detect hexachlorobenzene, and the sintered brick strength is comparable to that of Comparative Example 2, meeting the strength requirements of sintered brick. The above test results show that the green low-carbon external additive of the present application can effectively reduce the toxicity of hexavalent chromium in contaminated soil, control the secondary pollution risk of heavy metals and organic pollutants during the sintering process, and the leaching toxicity and strength of the sintered brick product during the production process meet the utilization requirements.

[0109] In addition, the sintering temperature of the sintered bricks of embodiments 1-9 is 600-700℃, the sintering time is 6h, and the related properties of the related products are all better than those of comparative examples 1-4, and more significantly better than those of comparative examples 5-6 (sintered at 650℃ for 6h) under the same sintering conditions; wherein the sintering parameters used in comparative examples 1-2 are temperature 1000℃ and sintering time 8h, the sintering parameters used in comparative examples 3-4 are temperature 850℃ and sintering time 8h, and the sintering parameters used in comparative examples 5-6 are temperature 650℃ and sintering time 6h. The lower the sintering temperature, the higher the hexavalent chromium leaching concentration or the total value of hexachlorobenzene of the sintered brick product, and the lower the strength. The wall material of a building should generally be selected to be not less than the ordinary sintered brick of MU15.0 level, i.e., the average compressive strength is required to be not less than 15.0MPa, and the compressive strength of the sintered brick products in comparative examples 3-6 is lower than the above requirement; at the same time, the hexavalent chromium leaching concentration corresponding to comparative examples 3-6 is significantly higher than the fourth water standard (0.1mg / L) in the Groundwater Quality Standard (GB14848-2017), and the total value of hexachlorobenzene is more than 5 times higher than the second land control value (10mg / kg) in the Soil Environmental Quality Standard for Construction Land Soil Pollution Risk Control (Trial Implementation) (GB36600-2018).

[0110] In addition, long-term safety and air CO2 absorption rate tests under acid rain erosion environment are carried out for embodiments 1-9 and comparative examples 1-6 respectively. Among them:

[0111] (1) The hexavalent chromium leaching concentration test under the action of long-term acid rain erosion is carried out according to the method of the United States Environmental Protection Agency (Method 1315 Mass transfer rates of constituents in monolithic or compacted granular materials using a semi-dynamic tank leaching procedure), the leaching liquid is simulated acid rain with pH of 2.5, the liquid-solid contact surface area ratio (L / A) is 9±1mL / cm 2 , the leaching liquid is updated at time intervals of 23h, 23h, 5d, 7d, 14d, 14d, 7d and 14d, the test lasts for 63d, 9 times of sampling are tested, and the last leaching liquid is used to carry out hexavalent chromium concentration test, as the hexavalent chromium leaching concentration under the action of long-term acid rain erosion, to evaluate the long-term environmental safety of the sintered brick.

[0112] (2) The CO2 absorption rate test procedure is as follows: 1) Place the sintered brick sample in an artificial climate simulation test box, set the initial air CO2 concentration C0 in the range of 0.04%, the temperature range: 22℃, the relative humidity 85%; 2) Incubate for 60 days under strictly sealed conditions (eliminate the infiltration of ambient air), and then measure the air CO2 concentration C 60 in the test box. 60 (1-C 60 ) / C0x100%, to calculate the atmospheric CO2 absorption rate.

[0113] The test results are shown in Table 4 below.

[0114] Table 4 Long-term safety and air CO2 absorption rate of sintered brick in acid rain erosion environment of Examples 1-9 and Comparative Examples 1-6

[0115]

[0116] The hexavalent chromium leaching concentration of the green low-carbon external additive of the application applied in Examples 1-9 is significantly lower than that of the corresponding comparative examples under the action of long-term acid rain erosion, and meets the four-class water standard (0.1 mg / L) requirement in the “Groundwater Quality Standard” (GB14848-2017), and the atmospheric CO2 absorption rate is 1 order of magnitude higher than that of the corresponding comparative examples. It can be seen that the green low-carbon external additive for sintered brick for contaminated soil and the preparation and application method thereof provided by the application can significantly improve the long-term safety performance such as acid rain erosion resistance of sintered brick products for contaminated soil, and the sintered brick products prepared by the preparation method can more effectively capture and reduce the CO2 concentration in the air, realizing the capture and fixation of carbon in the environment.

[0117] Therefore, by applying the green low-carbon external additive of the application, compared with the traditional sintering brick making process, while ensuring the performance of the sintered brick product, the sintering temperature of the sintered brick for contaminated soil can be significantly reduced, energy consumption and material consumption can be saved, and the low-carbon green advantage characteristics are prominent.

[0118] The application has been described in detail in combination with specific embodiments and exemplary examples, but these descriptions cannot be understood as limiting the application. Those skilled in the art understand that the technical solutions and embodiments of the application can be variously replaced, modified or improved without deviating from the spirit and scope of the application, and these all fall within the scope of the application.

Claims

1. A green low-carbon admixture for contaminated soil sintered brick, characterized in that, The green low-carbon external additive comprises the following components by weight: 25-35 parts of magnesium reduction slag, 5-15 parts of pyrite slag, 5-15 parts of waste manganese slag, 2-8 parts of lignin, 2-8 parts of shell powder and / or eggshell powder, 10-20 parts of molasses, 2-8 parts of corn syrup, 15-25 parts of dry blue algae powder, and 5-15 parts of lithium iron phosphate waste.

2. The green low-carbon external admixture for contaminated soil sintered brick according to claim 1, characterized in that, The lignin is papermaking waste lignin, and the molasses is sugar industry waste molasses.

3. The process for the preparation of green low carbon admixture for contaminated soil sintered brick according to claim 1 or 2, characterized in that, The method comprises the following steps: S101: magnesium reduction slag, pyrite slag, and waste manganese slag are stirred and uniformly mixed, and then water is added and stirred to form a mixed slurry A; S102: blue algae is washed, freeze-dried, ground, and sieved to form dry blue algae powder, which is dry-mixed with lignin to form a mixed solid powder B; S103: lithium iron phosphate waste and the mixed solid powder B are added to the mixed slurry A, heated and activated, pyrolyzed to complete dryness under the protection of a nitrogen atmosphere, and then ground and sieved to obtain a mixed solid powder C; S104: molasses, corn syrup, shell powder, and / or eggshell powder are stirred and mixed, dried, ground, and sieved to obtain a mixed solid powder D; S105: the mixed solid powder C is dry-mixed with the mixed solid powder D to obtain the green low-carbon external additive.

4. The production method according to claim 3, characterized by, The heating and activation in step S103 is heating to 80°C and microwave activation, and the pyrolysis is heating at 300°C.

5. The production method according to claim 3, wherein The drying in step S104 is drying at 65°C until the water content is less than or equal to 3%.

6. The green low-carbon external additive of claim 1 or 2 or the green low-carbon external additive prepared by the method of any one of claims 3-5 is applied in the remediation of contaminated soil.

7. Use according to claim 6, characterized in that, The green low-carbon external additive is added to contaminated soil to prepare sintered bricks.

8. Use according to claim 7, characterized in that, The preparation method of the sintered bricks comprises the following steps: S201: water is added to the contaminated soil to be treated so that the water content of the contaminated soil is 3 times the liquid limit of the contaminated soil, to obtain treated contaminated slurry; S202: the green low-carbon external additive is added to the treated contaminated slurry and stirred and mixed uniformly to form a mixed slurry E; S203: the mixed slurry E is sieved by vibration to remove large particles with a particle size greater than 2 mm, to obtain a mixed slurry F; S204: the green low-carbon external additive is added to the mixed slurry F, stirred and mixed uniformly, and then aged to obtain aged material; S205: the aged material is transported to a brick machine, extruded by an extruder, and cut into green bricks; S206: the green bricks are stacked and then put into a sintered brick tunnel kiln for drying and sintering; S207: the sintered green bricks are naturally cooled to obtain sintered brick products.

9. Use according to claim 8, characterized in that, The sintering temperature is 600-700°C, and the sintering time is 6-8 h.

10. Use according to claim 8, characterized in that, The amount of the green low-carbon external additive added in step S202 is 15-25% by weight, and the amount of the green low-carbon external additive added in step S204 is 25-35% by weight.

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