Preparation method and application of hydrothermal carbon rich in humic acid and / or plant available phosphorus

Abstract

The invention relates to a preparation method and application of hydrothermal carbon rich in humic acid and / or plant available phosphorus, and belongs to the technical field of waste resource utilization. The hydrothermal carbon rich in humic acid and / or plant available phosphorus is obtained by taking the organic solid waste as a raw material and performing hydrothermal carbonization, and the content of the plant available phosphorus in the prepared hydrothermal carbon can be remarkably increased by taking the calcium-rich organic solid waste or the calcium-added organic solid waste as the raw material; calcium in the calcium-rich organic solid waste forms a calcium-humic acid-phosphorus complex with humic acid and phosphorus, so that the effect of synchronously enriching humic acid and phosphorus is achieved; the content of humic acid and / or plant available phosphorus in the prepared hydrothermal carbon is high. The organic solid waste is used as the raw material and is low in price and easy to obtain, so that the resource treatment cost is reduced; the preparation process of the hydrothermal carbon has the advantages of simple route, cheap and easily available raw materials, low energy consumption, no need of practical strong acid and strong alkali, safety in operation and suitability for large-scale synthesis and preparation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste resource utilization, and particularly relates to a preparation method and application of hydrothermal carbon rich in humic acid and / or plant available phosphorus. BACKGROUND

[0002] With the development of economy and society, the output of organic solid waste is increasing year by year, and the annual output has exceeded 2 billion tons. The treatment, disposal and resource utilization of organic solid waste have become a worldwide problem. Traditional treatment methods such as landfill and incineration can realize the treatment of organic solid waste, but have obvious defects, such as easy to cause secondary pollution to the environment, low resource recovery rate, and difficult to effectively recover biomass energy and nutrient elements (such as phosphorus and nitrogen) in organic solid waste. Therefore, an environmentally friendly and high resource recovery rate treatment method is needed to realize the reduction, resource utilization and harmless treatment of organic solid waste.

[0003] Humic acid is a mixture of complex oxygen-containing compounds and aromatic compounds, which widely exists in soil and plays an important role in global carbon cycle. Humic acid contains various active groups such as hydroxyl, carboxyl, phenolic hydroxyl and quinone groups. These active groups are conducive to the combination of humic acid with various metal elements or pollutants in soil, and improve the soil environment. Phosphorus is an essential element for modern agriculture and food production. At present, the production of phosphorus fertilizer mainly comes from the exploitation of non-renewable phosphorus ore, and it is estimated that phosphorus ore will be depleted in the next few decades, thereby affecting agricultural production and food supply. If the phosphorus and other nutrients in organic solid waste are not recycled, not only will it cause water eutrophication, but also will further exacerbate the loss of phosphorus resources. According to the European Union directive standard (77 / 535 / EEC 3.1.3), the bioavailability of phosphorus can be evaluated by the solubility of phosphorus in 2% citric acid in solid samples. Therefore, this method can be used to evaluate the plant availability of phosphorus in organic solid waste.

[0004] Hydrothermal treatment technology can decompose and transform organic solid waste into high-value products while significantly reducing its solid content. During hydrothermal treatment, organic matter undergoes dehydration, decarboxylation, and condensation reactions to form hydrothermal char rich in humic acid. Simultaneously, phosphorus in the organic solid waste reacts with metal ions during the hydrothermal process to form phosphate minerals that are retained in the hydrothermal char. Therefore, hydrothermal char rich in humic acid and phosphorus prepared by hydrothermal treatment has good land use prospects. Chinese patent CN106588313A discloses a method for preparing functional liquid fertilizer using agricultural waste biomass catalytic hydrothermal carbonization. This method uses the mixed liquid produced after the catalytic hydrothermal carbonization of agricultural waste biomass as the mother liquor, and adds nitrogen, phosphorus, potassium, and humic acid to prepare the functional liquid fertilizer. However, this method requires the additional addition of humic acid, resulting in high costs. Chinese patent CN108753324A discloses a method for producing humic acid and briquette fuel by hydrothermal carbonization of corn stalks. While this method can produce humic acid, it cannot increase the content of plant-available phosphorus in the hydrothermal char. Chinese patent CN114292145A discloses a method for preparing artificial humic acid urea slow-release fertilizer. This method involves adding an alkali as an active agent to prepare artificial humic acid, and then mixing the artificial humic acid powder with urea to prepare the slow-release fertilizer. However, this method requires the addition of an additional alkali, has a long reaction time (20-28 hours), and does not yield plant-available phosphorus. Chinese patent CN 110540479A discloses a method for the resource-based disposal of sludge. This method involves adding an alkali for hydrothermal treatment of the sludge to recover heavy metal ions. The prepared hydrothermal solution is rich in phosphorus and humic substances. The phosphorus can be absorbed and utilized by plants, with an absorbable phosphorus content of 70%-85%, and the humic substance content is 0.01-0.03%. Besides adding a strong alkali, the hydrothermal char produced by this method requires further digestion with strong acid, centrifugation, and the addition of a reducing agent for a reaction time of 2-24 hours. The entire preparation process requires the addition of strong acids and bases, and the reaction time is long, requiring 16-28 hours. Furthermore, it can only produce liquid fertilizer. This method is complex, has high production costs, requires strict control of process parameters, and the resulting liquid fertilizer is difficult to transport and store. Therefore, there is an urgent need to develop a novel method for preparing and applying hydrothermal carbon rich in humic acid and plant-available phosphorus. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing and applying hydrothermal char rich in humic acid and plant-available phosphorus.

[0006] This invention addresses the problem of low plant-available phosphorus content in existing hydrothermal charcoal, which leads to low efficiency in its use as fertilizer. Using organic solid waste as raw material, it provides a method for enriching humic acid and / or plant-available phosphorus in hydrothermal charcoal. The organic solid waste is subjected to hydrothermal carbonization to increase the content of humic acid and / or plant-available phosphorus in the hydrothermal charcoal.

[0007] To achieve the above object, the technical scheme adopted by the present application is: In a first aspect, the present application provides a preparation method of hydrothermal carbon rich in humic acid and / or plant available phosphorus, comprising the following steps: S1, drying, crushing and sieving the organic solid waste to obtain organic solid waste powder; S2, mixing the organic solid waste powder obtained in step S1 with water, and fully hydrothermally reacting in a hydrothermal reactor, cooling to room temperature, filtering, collecting the solid substance, and drying the obtained solid substance to obtain hydrothermal carbon.

[0008] In the present application, the organic solid waste is directly prepared into hydrothermal carbon after being prepared into powder, and the whole hydrothermal reaction lasts for a relatively short time, which can be as short as 0.5-1h. The content of humic acid and / or plant available phosphorus in the prepared hydrothermal carbon is significantly improved compared with that of the original organic solid waste powder, and hydrothermal carbon rich in humic acid and / or plant available phosphorus is obtained.

[0009] As a preferred embodiment of the preparation method of the present application, in step S1, the calcium element content of the organic solid waste powder is greater than 15mg / g dry basis, or a calcium source is added to the organic solid waste powder to make the calcium element content greater than 15mg / g dry basis. In the hydrothermal carbon prepared by using pig manure powder (calcium element content greater than 15mg / g dry basis) or pig manure powder with additional calcium element, the content of humic acid and plant available phosphorus is significantly improved, and hydrothermal carbon rich in humic acid and plant available phosphorus is obtained. In the hydrothermal carbon prepared by using sludge powder (calcium element content of the initial sludge powder is less than 15mg / g dry basis) to which a calcium source is added to make the calcium element content greater than 15mg / g dry basis, the content of plant available phosphorus is significantly improved, and hydrothermal carbon rich in plant available phosphorus is obtained.

[0010] The presence of calcium element increases the concentration of alkaline earth metal in the hydrothermal reaction process on the one hand, and increases the alkalinity in the hydrothermal reaction process on the other hand, which promotes the transformation of the form of phosphorus in the organic solid waste from other metal combined state phosphorus (such as iron / aluminum combined state phosphorus) to calcium combined state phosphorus. The solubility of calcium combined state phosphorus in citric acid is higher than that of iron / aluminum combined state phosphorus and other metal combined state phosphorus, which is beneficial to the increase of the content of plant available phosphorus in the hydrothermal carbon.

[0011] As a preferred embodiment of the preparation method of the present application, the calcium source includes at least one of calcium carbonate, calcium chloride, calcium oxide, calcium sulfate, calcium phosphate, calcium fluoride and calcium silicate.

[0012] The plant available phosphorus in the present application refers to the phosphorus component in the hydrothermal carbon that can be directly absorbed and utilized by plant roots.

[0013] As a preferred embodiment of the preparation method, in step S1, the organic solid waste comprises at least one of municipal sludge, pig manure, sawdust and garden weeds.

[0014] As a preferred embodiment of the preparation method, in step S1, the organic solid waste comprises at least one of municipal sludge and pig manure.

[0015] As a preferred embodiment of the preparation method, in step S1, the organic solid waste is pig manure.

[0016] As a preferred embodiment of the preparation method, in step S1, the sieving is sieving through a 40-60 mesh sieve.

[0017] As a preferred embodiment of the preparation method, in step S2, the temperature of the hydrothermal reaction is 100-280℃.

[0018] As a preferred embodiment of the preparation method, in step S2, the temperature of the hydrothermal reaction is 100-180℃. At this temperature, the content of plant available phosphorus in the hydrothermal carbon is higher.

[0019] As a preferred embodiment of the preparation method, in step S2, the temperature of the hydrothermal reaction is 180-280℃. At this temperature, the content of humic acid in the hydrothermal carbon is higher.

[0020] As a preferred embodiment of the preparation method, in step S2, the temperature of the hydrothermal reaction is 180℃. At this temperature, the contents of humic acid and plant available phosphorus in the hydrothermal carbon are higher.

[0021] As a preferred embodiment of the preparation method, in step S2, the ratio of the organic solid waste powder to water is 1-3g:10mL.

[0022] As a preferred embodiment of the preparation method, in step S2, the temperature increasing rate of the hydrothermal reaction is 5-10℃ / min; the time of the hydrothermal reaction is 0.5-4h; and the atmosphere of the hydrothermal reaction is nitrogen atmosphere.

[0023] As a preferred embodiment of the preparation method, in step S2, the drying is drying in an environment at 60-105℃.

[0024] In a second aspect, the present application provides a hydrothermal carbon prepared by the above preparation method.

[0025] In a third aspect, the present application provides an application of the above hydrothermal carbon in preparing humic acid and / or sodium humate.

[0026] The humic acid content of the hydrothermal carbon of the present application is high, up to 122.4 mg C / g of hydrothermal carbon, and the hydrothermal carbon can be converted into water-soluble sodium humate by the method of sodium pyrophosphate-sodium hydroxide, and after the reaction is completed, sodium humate solution is obtained by suction filtration, and humic acid can be obtained by acidifying the suction filtrate; or sodium humate can be obtained by concentrating and drying the suction filtrate.

[0027] In a fourth aspect, the present application provides the use of the above-mentioned hydrothermal carbon as a seedling substrate.

[0028] The hydrothermal carbon prepared by the present application has high humic acid and / or plant available phosphorus content, and rich pore structure, strong water and fertilizer retention capacity, and can effectively promote seed germination and plant growth, and has potential as a seedling substrate. The hydrothermal carbon of the present application can significantly improve the seed germination rate and promote the growth of plant roots and leaves when used as a seedling substrate for growing plants such as ryegrass.

[0029] In a fifth aspect, the present application provides the use of the above-mentioned hydrothermal carbon as an adsorbent.

[0030] The hydrothermal carbon prepared by the present application has high humic acid and / or plant available phosphorus content, and rich pore structure, strong water and fertilizer retention capacity, and can effectively promote seed germination and plant growth, and has potential as a seedling substrate. The hydrothermal carbon of the present application can significantly improve the seed germination rate and promote the growth of plant roots and leaves when used as a seedling substrate for growing plants such as ryegrass.

[0031] Compared with the prior art, the present application has the following advantages: The present application uses organic solid waste as raw material, and through hydrothermal carbonization, hydrothermal carbon rich in humic acid and / or plant available phosphorus is obtained. The use of organic solid waste rich in calcium or organic solid waste with added calcium as raw material can significantly increase the content of plant available phosphorus in the prepared hydrothermal carbon. The calcium in the organic solid waste rich in calcium forms a calcium-humic acid-phosphorus complex with humic acid and phosphorus, which plays a role in simultaneous enrichment of humic acid and phosphorus. The humic acid content of the prepared hydrothermal carbon is as high as 122.4 mg C / g, and the plant available phosphorus content is as high as 19.9 mg / g. The present application uses organic solid waste as raw material, which is cheap and easy to obtain, reducing the resource disposal cost of organic solid waste. The preparation process of the hydrothermal carbon of the present application is simple, the raw material is cheap and easy to obtain, and the energy consumption is low. No strong acid or strong base is needed, the operation is safe, and it is suitable for large-scale synthesis and preparation. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The present application provides a preparation process flow chart of hydrothermal carbon rich in humic acid and / or plant available phosphorus; Figure 2 The present application provides a preparation process flow chart of hydrothermal carbon rich in humic acid and / or plant available phosphorus; Figure 3The influence of the hydrothermal carbon of the present application on the germination rate, root length and leaf length of ryegrass as a seedling substrate. DETAILED DESCRIPTION

[0033] In order to better illustrate the purposes, technical solutions and advantages of the present application, the present application will be further described below in combination with specific examples.

[0034] Other materials, reagents, etc. used in the examples can be obtained from commercial channels if not otherwise specified.

[0035] The plant available phosphorus in the present application refers to the phosphorus component in the hydrothermal carbon that can be directly absorbed and utilized by the plant root system.

[0036] Example 1 One embodiment of the hydrothermal carbon rich in humic acid and / or plant available phosphorus of the present application comprises the following steps: S1, drying the collected sludge sample in a cool and ventilated place, and crushing the dried sludge to a size of less than 50 mesh (0.282 mm) to obtain a sludge powder; the carbon element in the sludge powder accounts for 16.3wt%, the phosphorus element content is 20.2mg / g, and the calcium element content is 7.1mg / g; S2, the sludge powder obtained in step S1 is placed in a hydrothermal reactor, pure water is added, and then hydrothermal reaction is carried out at 100℃ for 2h, after cooling to room temperature, filtration is carried out, the solid material is collected, and the obtained solid material is dried at 105℃ to obtain the hydrothermal carbon; the ratio of the sludge powder to pure water is 1g:10mL. The hydrothermal carbon of the present embodiment is named sludge-100-0.

[0037] Example 2 One embodiment of the hydrothermal carbon rich in humic acid and / or plant available phosphorus of the present application, the difference between the present embodiment and example 1 is only that the hydrothermal reaction temperature in step S2 is different. The hydrothermal reaction temperature in step S2 of example 1 is adjusted to 180℃ in the present embodiment. The hydrothermal carbon of the present embodiment is named sludge-180-0.

[0038] Example 3 One embodiment of the hydrothermal carbon rich in humic acid and / or plant available phosphorus of the present application, the difference between the present embodiment and example 2 is only that the raw material for hydrothermal reaction in step S2 is sludge powder added with calcium chloride. The preparation method comprises the following steps: S1, the same as example 2; S2, the sludge powder obtained in step S1 was placed in a hydrothermal reactor, pure water was added, and then a hydrothermal reaction was carried out at 180℃ for 2h. After cooling to room temperature, filtration was performed, and the solid substance was collected. The obtained solid substance was placed in an oven at 105℃ for drying, and the hydrothermal carbon was obtained. The ratio of the sludge powder to pure water was 1g:10mL. The amount of calcium chloride added was 30mg of calcium element per 1g of sludge powder (i.e. the amount added was 30mg Ca / g dry basis). The hydrothermal carbon of this embodiment was named sludge-180-30.

[0039] Example 4 An embodiment of the hydrothermal carbon rich in humic acid and / or plant available phosphorus of the present application, the difference between this embodiment and Example 1 is only that the organic solid waste in steps S1 and S2 is different. The organic solid waste sludge of Example 1 is adjusted to pig manure. The preparation method comprises the following steps: S1, the collected pig manure sample was placed in a cool and ventilated place for drying, and the dried pig manure was crushed to a size of less than 50 mesh (0.282mm), obtaining pig manure powder. The carbon element in the pig manure powder accounted for 32.48wt%, the phosphorus element content was 18mg / g, and the calcium element content was 17.5mg / g; S2, the pig manure powder obtained in step S1 was placed in a hydrothermal reactor, pure water was added, and then a hydrothermal reaction was carried out at 100℃ for 2h. After cooling to room temperature, filtration was performed, and the solid substance was collected. The obtained solid substance was placed in an oven at 105℃ for drying, and the hydrothermal carbon was obtained. The ratio of the pig manure powder to pure water was 1g:10mL. The hydrothermal carbon of this embodiment was named pig manure-100-0.

[0040] The process flow chart of the preparation of the hydrothermal carbon rich in humic acid and / or plant available phosphorus of the present application is shown in Figure 1 .

[0041] Examples 5-6 Two embodiments of the hydrothermal carbon rich in humic acid and / or plant available phosphorus of the present application, the difference between Examples 5-6 and Example 4 is only that the hydrothermal reaction temperature in step S2 is different. Specifically, Example 5: Compared with Example 4, the temperature of the hydrothermal reaction in step S2 of Example 4 was adjusted from 100℃ to 180℃. The hydrothermal carbon of this embodiment was named pig manure-180-0.

[0042] Example 6: Compared with Example 4, the temperature of the hydrothermal reaction in step S2 of Example 4 was adjusted from 100℃ to 280℃. The hydrothermal carbon of this embodiment was named pig manure-280-0.

[0043] Example 7 One embodiment of the humic acid and plant available phosphorus rich hydrochar, the difference between this embodiment and embodiment 5 is only in step S2, the raw material of hydrothermal reaction is pig manure powder added with calcium chloride. The preparation method comprises the following steps: S1, same as embodiment 1; S2, the pig manure powder obtained in step S1 is added with calcium chloride and then placed in a hydrothermal reactor, pure water is added, and then hydrothermal reaction is carried out at 180 DEG C, the reaction time is 2h, after cooling to room temperature, filtration is carried out, the solid substance is collected, the obtained solid substance is placed in an environment of 105 DEG C for drying, and the hydrochar is obtained; the ratio of the pig manure powder to pure water is 1g:10mL; the added amount of calcium chloride is: 30mg of calcium element is added per 1g of pig manure powder (that is, the added amount is 30mg Ca / g of dry basis). The hydrochar in this embodiment is named pig manure-180-30.

[0044] Embodiment 8 One embodiment of the humic acid and plant available phosphorus rich hydrochar, the difference between this embodiment and embodiment 4 is only in step S2, the raw material of hydrothermal reaction is pig manure powder added with calcium chloride. The preparation method comprises the following steps: S1, same as embodiment 1; S2, the pig manure powder obtained in step S1 is added with calcium chloride and then placed in a hydrothermal reactor, pure water is added, and then hydrothermal reaction is carried out at 100 DEG C, the reaction time is 2h, after cooling to room temperature, filtration is carried out, the solid substance is collected, the obtained solid substance is placed in an environment of 105 DEG C for drying, and the hydrochar is obtained; the ratio of the pig manure powder to pure water is 1g:10mL; the added amount of calcium chloride is: 30mg of calcium element is added per 1g of pig manure powder (that is, the added amount is 30mg Ca / g of dry basis). The hydrochar in this embodiment is named pig manure-100-30.

[0045] Embodiment 9 One embodiment of the humic acid and plant available phosphorus rich hydrochar, the difference between this embodiment and embodiment 8 is only in step S2, the added amount of calcium in the raw material of hydrothermal reaction is different, the added amount of calcium element in step S2 in embodiment 8 is adjusted to 60mg of calcium element per 1g of pig manure powder (that is, the added amount is 60mg Ca / g of dry basis). The hydrochar in this embodiment is named pig manure-100-60.

[0046] Embodiment 10 The embodiment of the water heat carbon rich in humic acid and / or plant available phosphorus is different from the embodiment 5 only in the ratio of pig manure powder to water in step S2. The ratio of pig manure powder to water in step S2 in the embodiment 5 is adjusted from 1g:10mL to 3g:10mL.

[0047] Test Example 1 The humic acid content and the plant available phosphorus content in the water heat carbon of the embodiments 1-10, the original sludge powder (the sludge powder in the embodiment 1) and the original pig manure powder (the pig manure powder in the embodiment 4) are tested as samples.

[0048] 1. The humic acid content is evaluated by using sodium hydroxide-sodium pyrophosphate extraction method.

[0049] Specifically, a 0.1mol / L sodium hydroxide+0.1mol / L sodium pyrophosphate mixed solution is configured, the water heat carbon (or pig manure powder) and the sodium hydroxide-sodium pyrophosphate mixed solution are added in a ratio of 1g:20mL, after the solid-liquid mixture is uniformly mixed, it is placed in a 90℃ water bath, and reacted for 30min, then centrifuged, the yellow-brown supernatant is collected and filtered through a 0.45μm filter membrane, and the operation is repeated until there is no obvious color in the liquid after centrifugation, and the supernatant is collected. 6mol / L hydrochloric acid solution is added to the collected supernatant, the solution pH is adjusted to <2 for acidification treatment, humic acid precipitates, filtration, and the acidification supernatant and humic acid solids are collected respectively. The dissolved organic carbon content in the supernatant before and after acidification is tested and calculated by combustion oxidation method and difference method respectively by using total organic carbon analyzer (TOC5000 RN, Yuanzhi instrument, Shanghai), and the difference value of total organic carbon before and after acidification is the humic acid content.

[0050] 2. The plant available phosphorus content is evaluated by using 2% citric acid extraction method.

[0051] Specifically, a 2% citric acid solution is configured, the water heat carbon and the 2% citric acid solution are added in a ratio of 1g solid to 100mL solution; after the solid-liquid mixture is uniformly mixed, it is placed in a shaker for reaction for 30min, the temperature is room temperature, and the rotation speed is 120-180rpm, then centrifuged, the precipitate is discarded, the supernatant is filtered through a 0.45μm filter membrane, the phosphorus content in the supernatant is measured by using ammonium molybdate spectrophotometry, and reference is made to “Determination of total phosphorus in water-molybdenum spectrophotometric method (GB 11893-89)”.

[0052] The test results of the humic acid content in the water heat carbon of the embodiments 1, 2, 4-6 are shown in Table 1. Table 1 The results of Table 1 show that the humic acid content of the organic solid waste such as sludge and pig manure is significantly improved after hydrothermal carbonization. The humic acid content of the hydrothermal carbon prepared at a hydrothermal reaction temperature of 180°C is more significantly improved, indicating that a hydrothermal reaction temperature of 180°C is more optimal.

[0053] The results of the test of the plant available phosphorus content of the hydrothermal carbon of Examples 4-6 are shown in Table 2. Table 2 According to the results of Table 1 and Table 2, the humic acid content and the plant available phosphorus content of the pig manure are both improved after hydrothermal carbonization. The humic acid content and the plant available phosphorus content of the hydrothermal carbon prepared at a hydrothermal reaction temperature of 180°C are more significantly improved, indicating that a hydrothermal reaction temperature of 180°C is more optimal.

[0054] The results of the test of the plant available phosphorus content of the hydrothermal carbon of Examples 2-3, 5, 7 are shown in Table 3. The results of Table 3 show that the plant available phosphorus content of the hydrothermal carbon prepared from the organic solid waste such as sludge and pig manure can be improved by adding calcium element before hydrothermal carbonization.

[0055] The results of the test of the humic acid content and the plant available phosphorus content of the hydrothermal carbon of Examples 4, 8, 9 are shown in Table 4. The results of Table 4 show that the humic acid content and the plant available phosphorus content of the hydrothermal carbon prepared by adding calcium element before hydrothermal reaction of pig manure at 100°C are both significantly improved.

[0056] The humic acid content and the plant available phosphorus content of the hydrothermal carbon of Example 10 are also both significantly higher than those of the original pig manure powder, indicating that hydrothermal carbonization is beneficial to improve the humic acid content and the plant available phosphorus content of the hydrothermal carbon prepared from pig manure.

[0057] In summary, hydrothermal carbonization of organic solid waste is beneficial to improve the humic acid content of the hydrothermal carbon, and additional addition of calcium element is beneficial to improve the plant available phosphorus content of the hydrothermal carbon. The humic acid content and the plant available phosphorus content of the hydrothermal carbon prepared from pig manure are both improved after hydrothermal carbonization, indicating that hydrothermal carbonization is beneficial to improve the humic acid content and the plant available phosphorus content of the hydrothermal carbon prepared from pig manure. Additional addition of calcium element is also beneficial to improve the humic acid content and the plant available phosphorus content of the hydrothermal carbon prepared from pig manure at 100°C.

[0058] Test Example 2 The hydrothermal carbon of Examples 4-6 is used as a seedling substrate to test its effect on plant growth.

[0059] The preparation of the hydrothermal carbon rich in humic acid and / or plant available phosphorus and its application is shown in the following schematic diagram Figure 2 .

[0060] Specific method: 0.1 g of hydrothermal carbon was evenly sprinkled in a seedling box containing seedling paper, and then 50 seeds of ryegrass were evenly placed (the seeds were soaked in pure water for 30 minutes before use), 10 mL of pure water was added to each seedling box. The prepared seedling box was placed in a plant incubator, with a light duration of 12 h per day and a humidity of 70%, and cultured for five days. The five-day germination rate of ryegrass was measured and calculated, and 10 ryegrass plants with five-day germination were randomly selected to measure and record the root length and leaf length.

[0061] The results of the effect of the hydrothermal carbon of examples 4-6 on the germination rate, root length and leaf length of ryegrass are shown in the following table Figure 3 The results show that the seed germination rate of the pig manure raw material culture is 92%, while the seed germination rate of the prepared hydrothermal carbon rich in humic acid and plant available phosphorus is 96-98%, which promotes the germination rate of ryegrass; at the same time, compared with the ryegrass cultured with pig manure powder raw material (leaf length 9.7 cm, root length 8.35 cm), the leaf length (10.3-10.6 cm) and root length (7.9-10.4 cm) of the ryegrass cultured with the hydrothermal carbon rich in humic acid and plant available phosphorus are increased (although the root length of example 4 is not significantly increased, but the leaf length is significantly increased). This shows that the prepared hydrothermal carbon rich in humic acid and / or plant available phosphorus of the present application is beneficial to the growth of plants and has the potential to be used as a seedling substrate for plants.

[0062] In summary, the preparation of the hydrothermal carbon of the present application realizes the enrichment of humic acid and / or plant available phosphorus in the hydrothermal carbon, which is beneficial to the growth of plants and further improves the resource utilization of organic solid waste.

[0063] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limited to the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for producing a hydrothermally carbonaceous material rich in humic acid and / or plant available phosphorus, characterized in that, The method comprises the following steps: S1, drying, crushing and sieving the organic solid waste to obtain organic solid waste powder; S2, mixing the organic solid waste powder obtained in step S1 with water, and performing hydrothermal reaction in a hydrothermal reactor, cooling to room temperature, filtering, collecting the solid substance, drying the obtained solid substance to obtain hydrothermal carbon.

2. The production method according to claim 1, wherein In step S1, the calcium content of the organic solid waste powder is greater than 15 mg / g dry basis, or a calcium source is added to the organic solid waste powder to make the calcium content greater than 15 mg / g dry basis; and / or, in step S1, the organic solid waste comprises at least one of municipal sludge, pig manure, sawdust, and garden grass.

3. The production method according to claim 2, wherein The calcium source comprises at least one of calcium carbonate, calcium chloride, calcium oxide, calcium sulfate, calcium phosphate, calcium fluoride, and calcium silicate.

4. The production method according to claim 1, wherein In step S2, the temperature of the hydrothermal reaction is 100-280℃.

5. The production method according to claim 1, wherein In step S2, the ratio of the organic solid waste powder to water is 1-3 g:10 mL.

6. The production method according to claim 1, wherein In step S2, the temperature rising rate of the hydrothermal reaction is 5-10℃ / min; and / or, in step S2, the time of the hydrothermal reaction is 0.5-4h; and / or, in step S2, the atmosphere of the hydrothermal reaction is nitrogen atmosphere.

7. Hydrothermal carbon prepared by the method of any one of claims 1-6.

8. Use of the hydrothermal carbon of claim 7 in the preparation of humic acid and / or sodium humate.

9. Use of the hydrothermal carbon of claim 7 as a seedling substrate.

10. Use of the hydrothermal carbon of claim 7 as an adsorbent.

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