Preparation method of low-cost multifunctional washing-free acid carbon

Abstract

The invention belongs to the related technical field of biochar preparation, and relates to a preparation method of low-cost multifunctional wash-free acid charcoal, in particular to a method for preparing multifunctional wash-free acid biochar with the functions of reducing alkali, increasing fertility and removing heavy metal at low cost through a one-step method. The method comprises the following steps: crushing a biomass raw material, mixing the crushed biomass raw material with a binder and water, carrying out extrusion molding, carrying out rolling mixing of a potash fertilizer and ammonium polyphosphate on the surface of a molded body or only mixing of ammonium polyphosphate, putting the raw material into a pyrolysis furnace, carrying out pyrolysis, and cooling to obtain the product. The method has the remarkable technical advantages that the preparation process is simple, the pyrolysis temperature is low, the energy consumption is low, the carbon emission is low, acid pickling, water washing and inert gas protection are not needed, and the economic feasibility and applicability of the technology are contributed by'three-low and three-zero '. And the prepared product has multiple effects of efficiently adsorbing heavy metal pollutants and slowly releasing ammonia nitrogen, potassium and other crop growth fertilizers. More prominently, the prepared carbon is not conventional alkali carbon, and belongs to acid carbon which can be used for saline-alkali soil treatment.

Description

Technical Field

[0001] The invention belongs to the technical field related to biochar preparation, and relates to a method for preparing low-cost multifunctional wash-free acidic biochar, which is a one-step low-cost method for preparing multifunctional wash-free acidic biochar with the functions of reducing alkali, increasing fertilizer, and removing heavy metals. Background Art

[0002] Most saline-alkali soils are alkaline, with high pH values ​​and high exchangeable sodium content in the soil, which causes soil compaction, poor water holding capacity, and low crop yields. Saline-alkali land resources are important reserve soil resources in my country. The development and rational use of saline-alkali land plays an important role in ensuring absolute food security and maintaining the stability of existing cultivated land. At present, the main improvement measures for saline-alkali land include physical measures, chemical measures, and biological measures. Biochar is a common soil conditioner that can improve the physical, chemical, and biological properties of the soil, and has multiple functions such as removing heavy metal pollutants from the soil and providing organic fertilizers for the soil. In addition, the rich pore structure of biochar also provides attachment sites for microorganisms, promoting the growth and reproduction of soil microorganisms. However, most biochars are alkaline at present, and most of the research on soil improvement is reflected in acidic soils. The unreasonable application of alkaline biochar in saline-alkali land will aggravate the degree of soil salinization. Therefore, it is necessary to develop an acidic biochar suitable for saline-alkali soil.

[0003] So far, the number of patents for the preparation of acidic biochar is limited, and the preparation methods of acidic biochar disclosed in most patents are: first pyrolysis to prepare biochar, and then add acidic agents for adjustment. For example, patent document CN118344874A discloses a modified biochar for saline-alkali land improvement and its preparation method, firstly, raw materials such as bamboo are fed into a carbonization furnace through a feeder, and carbonized at 650-700°C under anaerobic conditions, and the biochar obtained by pyrolysis is then mixed with oxalic acid and ascorbic acid, wood vinegar, acetone, microbial agents, etc. in turn, and each mixing needs to be dried for 6-8 hours. Patent document CN110790607A discloses an acidic biochar fertilizer suitable for saline-alkali soil and its preparation method, firstly, the raw materials are subjected to hydrothermal reaction, and the samples after the reaction are reacted and cleaned with ethanol, and the biochar is obtained after drying, and then the biochar is mixed with nitric acid and impregnated for 6-24 hours, dried after soaking, and then granulated using a disc granulator. Patent document CN106381150A discloses a method for preparing an acidic biochar improver for improving saline-alkali soil, the preparation steps include first carbonizing and pyrolyzing the raw material to obtain biochar, then mixing it with an acidic solution for adsorption and soaking for 20-28 hours, then mixing calcium phosphate, potassium chloride, humic acid, amino acid polymer, etc. in a certain proportion, and finally mixing the mixture with the acid-soaked biochar to obtain acidic biochar. The preparation method of the acidic biochar described in the above patent is complicated, the steps are cumbersome, the cost needs to be further reduced, and the multifunctionality needs to be further improved. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a one-step low-cost method for preparing multifunctional wash-free acidic biochar with the functions of reducing alkali, increasing fertilizer and removing heavy metals.

[0005] The technical solution of the present invention:

[0006] A method for preparing low-cost multifunctional no-wash acid carbon, the steps are as follows:

[0007] Step (1) crushing the biomass raw material and sieving it to obtain a powder raw material with a particle size of 40 to 100 meshes, then adding a binder and water, and extruding and molding it to obtain a molding raw material;

[0008] Step (2) rolling and mixing a layer of potash fertilizer on the surface of the molding raw material obtained in step (1), wherein the mass ratio of the raw material to the potash fertilizer is 1:0 to 1:0.4, and then rolling and mixing ammonium polyphosphate, wherein the mass ratio of the raw material to the ammonium polyphosphate is 1:0.05 to 1:0.8, and standing for 1 to 6 hours;

[0009] Step (3) placing the mixed raw materials in step (2) into a pyrolysis furnace for pyrolysis, and obtaining wash-free acid charcoal after cooling, without any post-processing steps such as acid washing, water washing and pre-drying.

[0010] The biomass in step (1) can be any one or a combination of two or more of common biochar raw materials such as corn cobs, straw, rice husks, coconut shells, bamboo powder, sawdust, etc.

[0011] The binder in step (1) can be an organic binder, such as one or a combination of two or more of phenolic resin, carboxymethyl cellulose, polyvinyl butyral, asphalt and sodium carboxymethyl starch; or an inorganic binder, such as one or a combination of two or more of bentonite, calcium hydroxide, phosphate and silicate.

[0012] The potash fertilizer in step (2) can be one or a combination of two or more of potassium chloride, potassium phosphate and potassium carbonate.

[0013] The degree of polymerization of the ammonium polyphosphate in the step (2) should be less than 200.

[0014] The pyrolysis temperature in step (3) is 200-500° C., and the pyrolysis time is 5-60 minutes.

[0015] Preferably, in step (2), the mass ratio of the raw material to the potash fertilizer is 1:0.05 to 1:0.1, and the mass ratio of the raw material to the ammonium polyphosphate is 1:0.1 to 1:0.3.

[0016] Preferably, in step (3) of the present invention, the optimal pyrolysis temperature is 300-400°C.

[0017] Beneficial effects of the present invention:

[0018] (1) From the perspective of performance: the biochar prepared by the present invention has the triple effects of lowering the pH of saline-alkali soil, efficiently adsorbing heavy metal pollutants, and slowly releasing ammonia nitrogen, potassium and other fertilizers for crop growth.

[0019] (2) Analysis from the preparation process: The method of the present invention has significant technical advantages over the traditional pyrolysis method for preparing biochar: ① low pyrolysis temperature, low energy consumption and low carbon emissions. The traditional pyrolysis carbonization or activation process for preparing biochar often requires the temperature to be set to above 500°C, while the present invention can achieve low-temperature preparation of biochar. The lower pyrolysis temperature not only reduces production energy consumption, but also reduces production costs. Low power consumption means low carbon emissions, which is in line with the current development trend of global carbon emissions; ② Simple preparation process: The biochar prepared by the present invention is multifunctional, but the preparation process is simple, breaking the traditional preparation of slow-release biochar-based fertilizers or acidic biochar. The multi-step cumbersome preparation method of first preparing biochar and then adding agents. The simplification of the preparation process further promotes the reduction of production costs and the practical feasibility of the technology; ③ No additional inert gas protection is required, and no water washing or acid washing is required. By reviewing many existing patents and published papers, it can be found that: At present, most of the pyrolysis projects for preparing biochar still use inert protective gases such as nitrogen or argon, and the prepared biochar often needs to be cleaned with strong acids such as hydrochloric acid and hydrofluoric acid, and also requires a large amount of water for cleaning. This subsequent cleaning process consumes a lot of reagents and water resources, and also produces a lot of waste liquid, which requires secondary treatment. In the pyrolysis process of the present invention, no external inert gas protection is required, and the flame retardant mechanism of ammonium polyphosphate is used to isolate the outside air to prevent the ashing of the material during the pyrolysis process. The biochar after pyrolysis can be used directly after natural cooling without cleaning, because ammonium polyphosphate is a typical soil conditioner that has the effect of increasing the efficiency of nitrogen and phosphorus fertilizers.

[0020] (3) From the perspective of product characteristics, the present invention can prepare a multi-layer core-shell structure with a biochar inner shell, a potash fertilizer middle shell, and a nitrogen and phosphorus fertilizer outer shell. The ammonium polyphosphate in the outermost layer has dual properties. It promotes carbonization processes such as thermal polycondensation during pyrolysis. The ammonium polyphosphate remaining after pyrolysis has the function of providing nitrogen and phosphorus fertilizers for the soil. During the application process, the middle layer of potash fertilizer can not only passivate heavy metals in the soil through cation exchange, but also provide nutrients for the soil. The biochar in the inner shell can also remove heavy metals and provide nutrients for the soil due to its own adsorption and organic fertilizer properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a comparison chart of the adsorption performance of heavy metal lead by biochar prepared in Examples 1-5 and Comparative Examples 1-5;

[0022] Figure 2It is a comparison chart of the adsorption performance of heavy metal lead by biochar prepared by different potassium phosphate addition ratios in Example 6-10 and Comparative Example 6-10;

[0023] Figure 3 It is a comparison chart of the adsorption performance of heavy metal lead by biochar prepared at different pyrolysis temperatures of Examples 2, 11-13 and Comparative Examples 2, 11-13;

[0024] Figure 4 This is a graph showing the change in soil pH after Example 3 was applied to saline-alkali land at different dosages for 30 days. DETAILED DESCRIPTION

[0025] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0026] Example 1

[0027] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 40 mesh. A binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.05. After standing for 1 hour, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, and the pyrolysis is performed for 30 minutes. After cooling, multifunctional and wash-free acid charcoal of biochar can be obtained.

[0028] Example 2

[0029] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 80 meshes, a binder and 10% water are added in a mass ratio of raw material: binder = 5:1, and after extrusion molding, ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.1. After standing for 3 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is performed for 30 minutes, and after cooling, multifunctional biochar no-wash acid charcoal is obtained.

[0030] Example 3

[0031] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 meshes, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.3. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, and the pyrolysis is performed for 30 minutes. After cooling, multifunctional and wash-free acid charcoal of biochar can be obtained.

[0032] Example 4

[0033] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 mesh. A binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.5. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is performed for 30 minutes, and after cooling, multifunctional and wash-free acid charcoal of biochar can be obtained.

[0034] Example 5

[0035] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 meshes, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.8. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is performed for 30 minutes, and after cooling, multifunctional and wash-free acid charcoal of biochar can be obtained.

[0036] Example 6

[0037] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 meshes, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the molding material is mixed with potassium phosphate in a mass ratio of 1:0.05, and then ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of the molding material to ammonium polyphosphate of 1:0.1. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is performed for 30 minutes, and after cooling, multifunctional and wash-free acid charcoal of biochar can be obtained.

[0038] Example 7

[0039] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 meshes, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the molding material is mixed with potassium phosphate in a mass ratio of 1:0.1, and then ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of the molding material to ammonium polyphosphate of 1:0.1. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is performed for 30 minutes, and after cooling, multifunctional and wash-free acid charcoal of biochar can be obtained.

[0040] Example 8

[0041] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 meshes, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the molding material is mixed with potassium phosphate in a mass ratio of 1:0.2, and then ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of the molding material to ammonium polyphosphate of 1:0.1. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is performed for 30 minutes, and after cooling, multifunctional and wash-free acid charcoal of biochar can be obtained.

[0042] Example 9

[0043] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 meshes, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the molding material is mixed with potassium phosphate in a mass ratio of 1:0.3, and then ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of the molding material to ammonium polyphosphate of 1:0.1. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is performed for 30 minutes, and after cooling, biochar multifunctional wash-free acid charcoal can be obtained.

[0044] Example 10

[0045] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 meshes, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the molding material is mixed with potassium phosphate in a mass ratio of 1:0.4, and then ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of the molding material to ammonium polyphosphate of 1:0.1. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is performed for 30 minutes, and after cooling, multifunctional and wash-free acid charcoal of biochar can be obtained.

[0046] Embodiment 11

[0047] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 80 meshes, a binder and 10% water are added in a mass ratio of raw material: binder = 5:1, and after extrusion molding, ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.1. After standing for 3 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set at 200°C, the pyrolysis is performed for 30 minutes, and after cooling, multifunctional and wash-free acid charcoal of biochar can be obtained.

[0048] Example 12

[0049] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 80 meshes, a binder and 10% water are added in a mass ratio of raw material: binder = 5:1, and after extrusion molding, ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.1. After standing for 3 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 400°C, the pyrolysis is performed for 30 minutes, and after cooling, multifunctional and wash-free acid charcoal of biochar can be obtained.

[0050] Example 13

[0051] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 80 meshes, a binder and 10% water are added in a mass ratio of raw material: binder = 5:1, and after extrusion molding, ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.1. After standing for 3 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 500°C, the pyrolysis is performed for 30 minutes, and after cooling, multifunctional and wash-free acid charcoal of biochar can be obtained.

[0052] Comparative Example 1

[0053] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 mesh. A binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.05. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is performed for 30 minutes, and the raw material is washed with water after cooling, and then dried for use.

[0054] Comparative Example 2

[0055] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 mesh, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.1. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is performed for 30 minutes, and the raw material is washed with water after cooling, and then dried for use.

[0056] Comparative Example 3

[0057] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 mesh, and a binder and 10% water are added in a ratio of raw material: binder = 5:1. After extrusion molding, the ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.3. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is performed for 30 minutes, and the raw material is washed with water after cooling, and then dried for use.

[0058] Comparative Example 4

[0059] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 mesh. A binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.5. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is performed for 30 minutes, and the raw material is washed with water after cooling, and then dried for use.

[0060] Comparative Example 5

[0061] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 mesh. A binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.8. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is performed for 30 minutes, and the raw material is washed with water after cooling, and then dried for use.

[0062] Comparative Example 6

[0063] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 meshes, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the molding material is mixed with potassium phosphate in a mass ratio of 1:0.05, and then ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.1. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is carried out for 30 minutes, and the raw material is washed with water after cooling, and then dried for use.

[0064] Comparative Example 7

[0065] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 meshes, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the molding material is mixed with potassium phosphate in a mass ratio of 1:0.1, and then ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of the molding material to ammonium polyphosphate of 1:0.1. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is carried out for 30 minutes, and the raw material is washed with water after cooling, and then dried for use.

[0066] Comparative Example 8

[0067] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 mesh, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the molding material is mixed with potassium phosphate in a mass ratio of 1:0.2, and then ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.1. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is carried out for 30 minutes, and the raw material is washed with water after cooling, and then dried for use.

[0068] Comparative Example 9

[0069] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 meshes, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the molding material is mixed with potassium phosphate in a mass ratio of 1:0.3, and then ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.1. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is carried out for 30 minutes, and the raw material is washed with water after cooling, and then dried for use.

[0070] Comparative Example 10

[0071] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 100 meshes, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the molding material is mixed with potassium phosphate in a mass ratio of 1:0.4, and then ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.1. After standing for 6 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 300°C, the pyrolysis is carried out for 30 minutes, and the raw material is washed with water after cooling, and then dried for use.

[0072] Comparative Example 11

[0073] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 80 mesh, and a binder and 10% water are added in a ratio of raw material: binder = 5:1. After extrusion molding, the ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.1. After standing for 3 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set at 200°C, the pyrolysis is performed for 30 minutes, and the raw material is washed with water after cooling, and then dried for use.

[0074] Comparative Example 12

[0075] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 80 meshes, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.1. After standing for 3 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 400°C, the pyrolysis is performed for 30 minutes, and the raw material is washed with water after cooling, and then dried for use.

[0076] Comparative Example 13

[0077] The corn stalks are crushed and sieved to obtain a powder raw material with a particle size of 80 meshes, and a binder and 10% water are added in a mass ratio of raw material: binder = 5:1. After extrusion molding, the ammonium polyphosphate with a polymerization degree of 50 is rolled and mixed in a mass ratio of molding material to ammonium polyphosphate of 1:0.1. After standing for 3 hours, the raw material is put into a pyrolysis furnace, the pyrolysis temperature is set to 500°C, the pyrolysis is performed for 30 minutes, and the raw material is washed with water after cooling, and then dried for use.

[0078] pass Figure 1 , Figure 2 and Figure 3 The data show that the adsorption capacity of Pb(II) by the unwashed acid carbon prepared in the examples is higher than that by the water-washed carbon in the comparative example. The reason for the low adsorption capacity of the water-washed carbon may be that the water-washing process changes the physical and chemical properties of the carbon material, especially some surface active groups such as phosphate and ammonium groups are removed during the water-washing process. Figure 1 The adsorption capacity of acid carbon prepared with different ammonium polyphosphate ratios was compared. Among them, the unwashed acid carbon prepared in Example 3 had the highest adsorption capacity for Pb(II), up to 250 mg / g, which was about 6 times higher than that of water-washed carbon under the same preparation conditions. Figure 2 By comparing the adsorption capacity of acid carbon prepared with different potassium phosphate addition ratios, it can be seen that the best adsorption capacity is the potassium phosphate addition ratio of 1:0.1 and 1:0.2, with adsorption capacities as high as 314 mg / g and 318 mg / g. Among them, the potassium phosphate addition ratio is 1:0.05, and the adsorption capacity is also very good, reaching 256 mg / g. Taking into account the cost-effectiveness and raw material consumption, the preferred mass ratio of raw materials to potash fertilizer is 1:0.05 to 1:0.1. Figure 3 The effect of pyrolysis temperature on adsorption was investigated. From the data, it can be seen that except for the special case of 200℃, the other temperatures have no significant effect on adsorption. Considering that the stability of acid char under 200℃ pyrolysis conditions is extremely poor, which is not conducive to soil application, and the pyrolysis temperature of 500℃ is too high, resulting in large energy loss, the preferred pyrolysis temperature is 300-400℃. Figure 4 From the data, we can see that: No. 0 represents the original pH value of saline-alkali soil without adding any acid carbon, which is about 9.5. After 30 days of acid carbon treatment in different proportions, the pH dropped significantly, and as the amount of acid carbon added increased, the pH dropped faster. Figure 4The data fully demonstrate the functional properties of the prepared acid carbon in lowering the pH of saline-alkali soil.

Claims

1. A method for preparing low-cost multifunctional no-wash acid charcoal, characterized in that: Here are the steps: Step (1) crushing the biomass raw material and sieving it to obtain a powder raw material, then adding a binder and water, and extruding it to obtain a molding raw material; Step (2) rolling and mixing a layer of potash fertilizer on the surface of the molding raw material obtained in step (1), wherein the mass ratio of the raw material to the potash fertilizer is 1:0 to 1:0.4, and then rolling and mixing ammonium polyphosphate, wherein the mass ratio of the raw material to the ammonium polyphosphate is 1:0.05 to 1:0.8, and letting it stand; Step (3) placing the mixed raw materials in step (2) into a pyrolysis furnace for pyrolysis, and obtaining wash-free acid charcoal after cooling.

2. The method for preparing a low-cost multifunctional no-wash acid charcoal according to claim 1, characterized in that: The particle size of the powder raw material obtained in step (1) is 40 to 100 meshes.

3. The method for preparing a low-cost multifunctional no-wash acid charcoal according to claim 1, characterized in that: The standing time in step (2) is 1 to 6 hours.

4. The method for preparing a low-cost multifunctional no-wash acid charcoal according to claim 1, characterized in that: The biomass in step (1) is one or a combination of two or more of corn cobs, straws, rice husks, coconut shells, bamboo powder and sawdust.

5. The method for preparing a low-cost multifunctional no-wash acid charcoal according to claim 1, characterized in that: When the binder in step (1) is an organic binder, it is one or a combination of two or more of phenolic resin, carboxymethyl cellulose, polyvinyl butyral, asphalt, and sodium carboxymethyl starch; when it is an inorganic binder, it is one or a combination of two or more of bentonite, calcium hydroxide, phosphate, and silicate.

6. The method for preparing a low-cost multifunctional no-wash acid charcoal according to claim 1, characterized in that: The potash fertilizer in step (2) is one or a combination of two or more of potassium chloride, potassium phosphate and potassium carbonate.

7. The method for preparing a low-cost multifunctional no-wash acid carbon according to claim 1, characterized in that: The degree of polymerization of the ammonium polyphosphate in the step (2) is less than 200.

8. The method for preparing a low-cost multifunctional no-wash acid carbon according to claim 1, characterized in that: The pyrolysis temperature in step (3) is 200-500° C., and the pyrolysis time is 5-60 minutes.

9. The method for preparing a low-cost multifunctional no-wash acid carbon according to claim 8, characterized in that: In step (3), the pyrolysis temperature is 300-400°C.

10. The method for preparing a low-cost multifunctional no-wash acid carbon according to claim 1, characterized in that: In step (2), the mass ratio of the raw material to the potash fertilizer is 1:0.05 to 1:0.1, and the mass ratio of the raw material to the ammonium polyphosphate is 1:0.1 to 1:0.3.

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