Saline-alkali modifier as well as preparation method and application thereof

Abstract

The invention provides a saline-alkali modifier as well as a preparation method and application thereof, and belongs to the technical field of solid waste treatment and soil remediation. According to the method, decomposed sludge is mixed with potassium hydroxide, sodium alpha-hydroxymethyl sulfonate and ferric salt for catalytic pyrolysis, oxidative cracking and recombination of humic acid are achieved, high-activity fulvic acid is generated, potassium hydroxide provides a strong alkaline environment, lignin beta-O-4 bonds are promoted to break, phenolic hydroxyl active sites are released, and accordingly the high-activity fulvic acid is obtained. The sodium alpha-hydroxymethyl sulfonate introduces a sulfonic acid group through a sulfomethylation reaction to improve the water solubility of the product, the ferric salt provides iron ions as an electron transfer medium to improve the fulvic acid generation efficiency, and the sodium alpha-hydroxymethyl sulfonate, the ferric salt and the fulvic acid have a synergistic effect to improve the content and the water solubility index of the fulvic acid; the inositol, the copper salt and the potassium silicate are added to form a copper ion-inositol-silicate chelating network, so that nutrients in the pyrolysis sludge can be fixed to form a slow-release particle structure, the specific surface area of the improver is increased, and the improvement effect and adaptability of the improver are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste treatment and soil remediation, and particularly relates to a saline-alkali soil conditioner, a preparation method thereof, and an application thereof. Background Art

[0002] Saline-alkali soil refers to soil containing harmful salts such as chlorides, sulfates, and bicarbonates of potassium, sodium, calcium, and magnesium. The main characteristics of saline-alkali soil are a relatively high pH value and the presence of harmful salts, which severely restrict the growth of plants. Among them, sodium ions have a serious inhibitory and toxic effect on the growth of plant roots. These lands cannot be cultivated normally and need to be repaired before reproduction.

[0003] Currently, the main chemical method for treating saline-alkali soil is to add soil conditioners. Using fermented and matured domestic sewage sludge as a soil conditioner can not only improve the soil but also enable the resource utilization of domestic sewage sludge, and it has a wide application in soil improvement. However, in the prior art, the soil conditioner obtained by fermenting and maturing domestic sewage sludge has a relatively general improvement effect and poor adaptability (failure due to high-salt inhibition).

[0004] Therefore, how to improve the improvement effect and adaptability of the conditioner has become a difficult problem in the prior art. Summary of the Invention

[0005] The purpose of the present invention is to provide a saline-alkali soil conditioner, a preparation method thereof, and an application thereof. The saline-alkali soil conditioner prepared by the present invention has excellent improvement effect and adaptability. [[ID=2 O]]

[0006] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a preparation method of a saline-alkali soil conditioner, comprising the following steps:

[0008] (1) Mixing sludge with a lignocellulosic conditioner, and successively performing aerobic fermentation, composting, and aging to obtain matured sludge;

[0009] (2) Mixing the matured sludge obtained in step (1) with potassium hydroxide, sodium α-hydroxy methylsulfonate, and an iron salt, and performing catalytic pyrolysis to obtain pyrolyzed sludge;

[0010] (3) Mixing the pyrolyzed sludge obtained in step (2) with inositol, a copper salt, and potassium silicate, and successively performing extrusion granulation and drying to obtain the saline-alkali soil conditioner.

[0011] Preferably, in step (1), based on the dry basis mass of the sludge, the mass ratio of the sludge to the lignocellulosic conditioner is 100:(4 - 6).

[0012] Preferably, in the step (1), the temperature of aerobic fermentation is 60 - 65°C, the oxygen supply for aerobic fermentation is ≥ 0.5 m 3 / (m 3 ·min), and the time of aerobic fermentation is ≥ 120 h.

[0013] Preferably, in the step (1), the aging time is 90 - 120 d.

[0014] Preferably, in the step (2), based on the dry basis mass of the matured sludge, the mass ratio of the matured sludge, potassium hydroxide, sodium α - hydroxymethylsulfonate, and iron salt is 100:(4 - 5):(2 - 3):(0.1 - 0.2).

[0015] Preferably, in the step (2), the temperature of catalytic pyrolysis is 150 - 170°C, and the time of catalytic pyrolysis is 20 - 25 min.

[0016] Preferably, in the step (3), the mass ratio of the pyrolyzed sludge, inositol, copper salt, and potassium silicate is (92 - 96):(2 - 3):(0.3 - 0.5):(2 - 4).

[0017] Preferably, in the step (3), the pressure of extrusion granulation is 1.5 - 2 MPa.

[0018] The present invention also provides a saline - alkali soil conditioner prepared by the preparation method described in the above technical solution.

[0019] The present invention also provides the application of the saline - alkali soil conditioner described in the above technical solution in soil improvement.

[0020] The present invention provides a preparation method of a saline - alkali soil conditioner, comprising the following steps: (1) mixing sludge with a lignocellulosic conditioner, and successively performing aerobic fermentation, ripening, and aging to obtain matured sludge; (2) mixing the matured sludge obtained in the step (1) with potassium hydroxide, sodium α - hydroxymethylsulfonate, and iron salt, and performing catalytic pyrolysis to obtain pyrolyzed sludge; (3) mixing the pyrolyzed sludge obtained in the step (2) with inositol, copper salt, and potassium silicate, and successively performing extrusion granulation and drying to obtain the saline - alkali soil conditioner. In the present invention, the matured sludge is mixed with potassium hydroxide, sodium α - hydroxymethylsulfonate, and iron salt and subjected to catalytic pyrolysis to achieve the oxidative cleavage and recombination of humic acid to generate highly active fulvic acid. Among them, potassium hydroxide provides a strong alkaline environment to promote the cleavage of the β - O - 4 bond of lignin and release phenolic hydroxyl active sites. Sodium α - hydroxymethylsulfonate introduces - SO3H groups through sulfomethylation reaction to improve the water solubility of the product. Iron salt provides ferric ions as an electron transfer medium to catalyze the quinone - phenol redox cycle and improve the production efficiency of fulvic acid. Moreover, the three have a synergistic effect to increase the content and water solubility index of fulvic acid; adding inositol, copper salt, and potassium silicate to form Cu 2+-Inositol-silicate chelation network can fix nutrients in pyrolyzed sludge to form a slow-release granular structure, increase the specific surface area of the soil conditioner, and improve the improvement effect and adaptability of the soil conditioner. The results of the examples show that after applying the saline-alkali soil conditioner prepared by the present invention to saline-alkali cotton fields (total salt 11.4 g / kg), the soil desalination rate reaches 21.9%, the pH value decreases by 0.23, the cation exchange capacity increases by 17.8%, and the cotton yield increases by 12.7%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flowchart of the preparation method of the saline-alkali soil conditioner provided by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention provides a preparation method of a saline-alkali soil conditioner, comprising the following steps:

[0023] (1) Mix sludge with a lignocellulosic conditioner, and carry out aerobic fermentation, composting and aging in sequence to obtain composted sludge;

[0024] (2) Mix the composted sludge obtained in step (1) with potassium hydroxide, sodium α-hydroxymethyl sulfonate and an iron salt, and carry out catalytic pyrolysis to obtain pyrolyzed sludge;

[0025] (3) Mix the pyrolyzed sludge obtained in step (2) with inositol, a copper salt and potassium silicate, and carry out extrusion granulation and drying in sequence to obtain a saline-alkali soil conditioner.

[0026] Unless otherwise specified, the present invention has no special limitation on the sources of various raw materials, and commercially available products well-known to those skilled in the art can be used.

[0027] The present invention mixes sludge with a lignocellulosic conditioner, and carries out aerobic fermentation, composting and aging in sequence to obtain composted sludge.

[0028] In the present invention, the sludge is preferably domestic sewage sludge. The present invention has no special limitation on the source of the domestic sewage sludge, and domestic sewage sludge well-known to those skilled in the art can be used.

[0029] In the present invention, the sludge is preferably dehydrated before use.

[0030] In the present invention, the water content of the dehydrated sludge is preferably 60-65 wt%. As an example, the water content of the dehydrated sludge can specifically be 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt% or 65 wt%.

[0031] The present invention has no special limitation on the operation of the dehydration treatment. The technical solutions for dehydration well-known to those skilled in the art can be adopted to ensure that the moisture content of the sludge after dehydration treatment is within the above range. In the embodiments of the present invention, the sludge is dehydrated by a plate and frame filter press.

[0032] In the present invention, the lignocellulosic conditioner is preferably agricultural and forestry waste, and more preferably includes one or more of wood chips, cottonseed hulls and straws. As an implementation manner, the lignocellulosic conditioner may specifically be pine sawdust. In the present invention, the lignocellulosic conditioner plays a role in ventilation, which is more conducive to the subsequent process.

[0033] In the present invention, the particle size of the lignocellulosic conditioner is preferably ≤5 mm.

[0034] In the present invention, based on the dry basis mass of the sludge, the mass ratio of the sludge to the lignocellulosic conditioner is preferably 100:(4 - 6). As an implementation manner, the mass ratio of the sludge to the lignocellulosic conditioner may specifically be 100:4, 100:4.5, 100:5, 100:5.5 or 100:6. By controlling the particle size and dosage of the lignocellulosic conditioner within the above range in the present invention, it is more conducive to the subsequent processes such as aerobic fermentation.

[0035] The present invention has no special limitation on the operation of mixing the sludge and the lignocellulosic conditioner. The technical solutions for mixing well-known to those skilled in the art can be adopted to ensure that the two are mixed evenly.

[0036] In the embodiments of the present invention, the mixing is carried out in a double-shaft mixer.

[0037] The present invention preferably stacks the mixed material obtained by mixing the sludge and the lignocellulosic conditioner into a trapezoidal strip stack and then carries out aerobic fermentation.

[0038] In the present invention, the lower bottom width of the trapezoidal strip stack is preferably 2 - 2.5 m, the upper bottom width is preferably 0.8 - 1.2 m, and the height is preferably 1.2 - 1.5 m. The present invention has no special limitation on the length of the trapezoidal strip stack, which can be selected according to actual needs. Stacking the mixed material into a trapezoidal strip stack in the present invention is more conducive to the aerobic fermentation process.

[0039] In the present invention, the temperature of the aerobic fermentation is preferably 60 - 65 °C. As an implementation manner, the temperature of the aerobic fermentation may specifically be 60 °C, 61 °C, 62 °C, 63 °C, 64 °C or 65 °C.

[0040] In the present invention, the oxygen supply amount for the aerobic fermentation is preferably ≥0.5 m 3 / (m 3·min), more preferably 0.5 - 0.8 m 3 / (m 3 ·min). The present invention preferably uses an intermittent forced ventilation system to control the oxygen supply. The present invention has no special limitation on the source and model of the intermittent forced ventilation system, and commercially available instruments well-known to those skilled in the art can be used.

[0041] In the present invention, the time of aerobic fermentation is preferably ≥ 120 h, more preferably 120 - 168 h. In the present invention, humic acid precursor substances (lignin degradation products) are directionally enriched during the aerobic fermentation process. By controlling the parameters of aerobic fermentation within the above range in the present invention, it is more conducive to the full fermentation of sludge.

[0042] In the present invention, during the aerobic fermentation process, turning and throwing is preferably carried out every 23 - 25 h, more preferably every 24 h. In the present invention, the turning and throwing is preferably carried out by an automatic turning and throwing device. The present invention has no special limitation on the model of the automatic turning and throwing device, and commercially available automatic turning and throwing devices well-known to those skilled in the art can be used. The turning and throwing in the present invention serves the purpose of dewatering and cooling.

[0043] In the present invention, the time of composting is preferably 216 - 384 h. As an implementation manner, the time of composting can specifically be 216 h, 240 h, 288 h, 336 h or 384 h.

[0044] In the present invention, during the composting process, turning the pile is preferably carried out every 72 - 96 h; the number of times of turning the pile during the composting process is preferably 3 - 4 times. The present invention has no special limitation on the operation of turning the pile, and technical solutions for turning the pile well-known to those skilled in the art can be used. By controlling the time of composting within the above range in the present invention, the product after aerobic fermentation can be further humified. In the present invention, during the composting process, the temperature of the composting material gradually decreases to the ambient temperature.

[0045] In the present invention, the time of aging is preferably 90 - 120 d; the aging is preferably carried out under natural ventilation conditions. As an implementation manner, the time of aging can specifically be 90 d, 100 d, 110 d or 120 d.

[0046] In the present invention, during the aging process, stacking is preferably turned over every 29 - 31 d, more preferably every 30 d. The present invention has no special limitation on the operation of turning over the stack, and technical solutions for turning over the stack well-known to those skilled in the art can be used. By controlling the time of aging within the above range in the present invention, it is more conducive to the full formation of humic acid in the sludge.

[0047] In the present invention, the seed germination index of the composted sludge is preferably ≥ 85%.

[0048] After obtaining the matured sludge, the present invention mixes the matured sludge with potassium hydroxide, sodium α-hydroxymethyl sulfonate (SMS) and an iron salt, and performs catalytic pyrolysis to obtain pyrolyzed sludge.

[0049] In the present invention, the purity of the potassium hydroxide is preferably ≥85%.

[0050] In the present invention, the iron salt preferably includes ferric sulfate or polyferric sulfate; the mass content of iron in the polyferric sulfate is preferably ≥19%.

[0051] In the present invention, based on the dry basis mass of the matured sludge, the mass ratio of the matured sludge, potassium hydroxide, sodium α-hydroxymethyl sulfonate and the iron salt is preferably 100:(4 - 5):(2 - 3):(0.1 - 0.2), more preferably 100:4.5:2.5:0.15. The present invention introduces an alkali activation-sulfonation-oxidation ternary coupling composite catalytic pyrolysis system to realize the oxidative cleavage and recombination of humic acid, and generate highly active fulvic acid. Among them, potassium hydroxide provides a strong alkaline environment to promote the cleavage of the lignin β-O-4 bond and release phenolic hydroxyl active sites. Sodium α-hydroxymethyl sulfonate introduces -SO3H groups through sulfomethylation reaction to improve the water solubility of the product. The iron salt provides iron ions as an electron transfer medium to catalyze the quinone-phenol redox cycle and improve the generation efficiency of fulvic acid. The present invention controls the mass ratio of the matured sludge, potassium hydroxide, sodium α-hydroxymethyl sulfonate and the iron salt within the above range, which can further increase the content of fulvic acid and further improve the improvement effect of the soil conditioner for saline-alkali soil.

[0052] As an embodiment, the mixing of the matured sludge, potassium hydroxide, sodium α-hydroxymethyl sulfonate and the iron salt is carried out in a twin-screw mixer; the rotation speed of the twin-screw mixer is 20 - 30 rpm; the mixing time is 5 - 8 min. The present invention does not have special limitations on the model of the twin-screw mixer, and a commercially available twin-screw mixer well-known to those skilled in the art can be used.

[0053] In the present invention, deionized water is preferably sprayed during the mixing process to adjust the moisture content of the mixture of the matured sludge, potassium hydroxide, sodium α-hydroxymethyl sulfonate and the iron salt to 63 - 67 wt%. The present invention controls the moisture content within the above range, which is more conducive to uniform mixing.

[0054] In the present invention, the temperature of the catalytic pyrolysis is preferably 150 - 170 °C. As an embodiment, the temperature of the catalytic pyrolysis can specifically be 150 °C, 155 °C, 160 °C, 165 °C or 170 °C.

[0055] In the present invention, the time of the catalytic pyrolysis is preferably 20 - 25 min. As an embodiment, the time of the catalytic pyrolysis can specifically be 20 min, 21 min, 22 min, 23 min, 24 min or 25 min. In the present invention, humic acid in the matured sludge reacts to generate fulvic acid during the catalytic pyrolysis process. By controlling the temperature, time, etc. of the catalytic pyrolysis within the above ranges in the present invention, the content of fulvic acid can be increased, and the improvement effect of the saline-alkali improver can be further enhanced.

[0056] In the present invention, the catalytic pyrolysis is preferably carried out under stirring conditions; the stirring rate is preferably 8 - 12 rpm.

[0057] In the present invention, during the catalytic pyrolysis process, the dehydration rate of the mixed material obtained by mixing the matured sludge, potassium hydroxide, sodium α-hydroxymethylsulfonate and iron salt is preferably 35 - 40 wt%.

[0058] As an embodiment, the catalytic pyrolysis is carried out in a paddle dryer. The present invention has no special limitation on the model of the paddle dryer, and a commercially available instrument well-known to those skilled in the art can be used.

[0059] In the present invention, the water solubility index of the pyrolyzed sludge is preferably ≥30%; the content of fulvic acid in the pyrolyzed sludge is preferably ≥10 wt%.

[0060] After obtaining the pyrolyzed sludge, the present invention mixes the pyrolyzed sludge with inositol (C6H 12 O6), copper salt and potassium silicate, and successively carries out extrusion granulation and drying to obtain a saline-alkali improver.

[0061] In the present invention, the copper salt is preferably copper sulfate pentahydrate.

[0062] In the present invention, the modulus of the potassium silicate is preferably 2 - 3, more preferably 2.5. By controlling the modulus of the potassium silicate in the present invention, its solubility is better, and rapid dissolution and dispersion can be achieved.

[0063] In the present invention, the mass ratio of the pyrolyzed sludge, inositol, copper salt and potassium silicate is preferably (92 - 96):(2 - 3):(0.3 - 0.5):(2 - 4), more preferably 94.1:2.5:0.4:3. The present invention uses the Cu 2+ -inositol-silicate chelation network for granulation, constructs a porous-coated composite structure, can fix the nutrients in the pyrolyzed sludge to form a slow-release granular structure, increases the specific surface area of the improver, and improves the improvement effect and adaptability of the improver. By controlling the mass ratio of the pyrolyzed sludge, inositol, copper salt and potassium silicate within the above ranges in the present invention, the improvement effect of the saline-alkali improver can be further enhanced.

[0064] In the present invention, the mixing of the pyrolyzed sludge with inositol, copper salt and potassium silicate is preferably carried out under stirring conditions; the rotation speed of the stirring is preferably 800 - 1200 rpm; the mixing time is preferably 10 - 15 min; the coefficient of variation after mixing is preferably ≤5%.

[0065] As an embodiment, the mixing of the pyrolyzed sludge with inositol, copper salt and potassium silicate is carried out in a high-speed shear disperser.

[0066] In the present invention, the temperature of the extrusion granulation is preferably 45 - 50 °C; the pressure of the extrusion granulation is preferably 1.5 - 2 MPa. By controlling the temperature and pressure of the extrusion granulation within the above ranges in the present invention, the obtained granules can be dense and uniform, and have excellent strength.

[0067] As an embodiment, the extrusion granulation is carried out in a twin-screw extrusion granulator; the barrel temperature of the twin-screw extrusion granulator is 45 - 50 °C; the die head pressure of the twin-screw extrusion granulator is 1.5 - 2 MPa. The present invention has no special limitation on the model of the twin-screw extrusion granulator, and a commercially available instrument well-known to those skilled in the art can be used.

[0068] In the present invention, the particle size of the granules obtained by extrusion granulation is preferably 2 - 3.5 mm; the strength of the granules is preferably ≥15 N / granule.

[0069] In the present invention, the drying temperature is preferably 60 - 65 °C. The present invention has no special limitation on the drying time, and it is only necessary to ensure that the moisture content of the saline-alkali soil conditioner after drying is within the required range.

[0070] In the present invention, the moisture content of the saline-alkali soil conditioner is preferably ≤15 wt%.

[0071] As an embodiment, the drying is carried out in a fluidized bed drying system; the inlet air temperature of the fluidized bed drying system is 60 - 65 °C; the wind speed of the fluidized bed drying system is 1.2 - 1.5 m / s.

[0072] In the present invention, the coating rate of the saline-alkali soil conditioner is preferably ≥95%.

[0073] The present invention constructs a three-stage combined method of "biological composting - catalytic pyrolysis - chelating granulation". The first stage of biological composting directionally enriches humic acid precursor substances (lignin degradation products) through aerobic fermentation at 60 - 65 °C; the second stage of catalytic pyrolysis introduces a KOH / Fe 3+ catalytic system to realize the oxidative cracking and recombination of humic acid, generating highly active fulvic acid; the third stage of chelating granulation utilizes Cu 2+-Inositol-silicate chelation network fixes nutrients, forms a slow-release granular structure, improves the improvement effect and adaptability of the saline-alkali improver, and realizes the high-value utilization of sludge.

[0074] The flow chart of the preparation method of the saline-alkali improver provided by the present invention is as Figure 1 shown: After the sludge is dewatered by plate and frame, a conditioner (lignocellulose conditioner) is added, followed by aerobic fermentation, composting, and aging. A catalyst (potassium hydroxide, α-hydroxymethylsulfonate, and iron salt) is added for mixing and conditioning (adjusting the moisture content during the mixing process), catalytic pyrolysis is carried out, and then a synergist (inositol, copper salt, and potassium silicate) is added for mixing, extrusion granulation, and drying to obtain the saline-alkali improver, which is then packaged as a finished product.

[0075] The present invention also provides a saline-alkali improver prepared by the preparation method described in the above technical solution.

[0076] After the saline-alkali improver prepared by the present invention is applied to moderately salinized cotton fields, it can significantly improve the physical and chemical properties of the soil, and has a certain increase in the content of soil nutrients such as organic matter, total nitrogen, and available phosphorus. It has a good improvement effect on moderately saline-alkali soil and plays a significant role in improving the emergence rate, promoting growth, and increasing the yield of cotton.

[0077] After the saline-alkali improver prepared by the present invention is applied to a moderately salinized (total salt 11.4 g / kg) cotton field, the soil desalination rate reaches 21.9%, the pH value decreases by 0.23, the cation exchange capacity increases by 17.8%, and the cotton yield increases by 12.7%.

[0078] The present invention also provides the application of the saline-alkali improver described in the above technical solution in soil improvement.

[0079] The present invention has no special limitation on the operation of the application, and the technical solutions of the application well-known to those skilled in the art can be adopted.

[0080] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0081] The seed germination index is obtained according to the test of NY-T 3442-2019;

[0082] The water-soluble index is obtained according to the determination method of GB / T 35818-2018;

[0083] The fulvic acid content is obtained according to the spectrophotometry of NY-T 3161-2017;

[0084] The particle strength is tested according to the determination method of GB / T 24891-2010;

[0085] The coating rate is tested by SEM-EDS surface element analysis;

[0086] The specific surface area is tested by the BET method.

[0087] Example 1

[0088] A preparation method of a saline-alkali improver:

[0089] (1) Take 1000 kg of domestic sewage sludge with a water content of 80 wt%, dehydrate it by plate and frame pressure filtration to a water content of 62 wt%, add pine sawdust (particle size ≤ 5 mm, based on the dry mass of the domestic sewage sludge, the mass ratio of domestic sewage sludge to pine sawdust is 100:5), mix it with a double-shaft mixer (rotation speed 25 rpm, time 10 min), stack it into a trapezoidal strip stack with a bottom width of 2.2 m, a top width of 1 m, and a height of 1.3 m, and use an intermittent forced ventilation system to control the oxygen supply to 0.6 m 3 / (m 3 ·min), carry out aerobic fermentation at 63 °C for 120 h, turn it over with an automatic turning machine every 24 h, then carry out composting, the composting time is 288 h, turn the pile every 96 h, turn the pile 3 times in total, and then age it for 120 d under natural ventilation conditions, turn the stack every 30 d to obtain matured sludge, and the seed germination index is 85%;

[0090] (2) Mix the matured sludge obtained in step (1) with KOH (purity 87%), sodium α-hydroxymethyl sulfonate (SMS, CAS 870-72-4) and polyferric sulfate (Fe content is 23 wt%) (based on the dry mass of the matured sludge, the mass ratio of matured sludge, KOH, sodium α-hydroxymethyl sulfonate and polyferric sulfate is 100:4.5:2.5:0.15), mix it with a twin-screw mixer (rotation speed 28 rpm, time 7 min), spray deionized water during the mixing process to make the water content reach 65 wt%, and then carry out catalytic pyrolysis through a paddle dryer, the temperature is 165 ± 2 °C, the time is 23 min, the paddle rotation speed is 10 rpm, the dehydration rate is 38 wt%, cool it to 48 °C and discharge to obtain pyrolyzed sludge, in which the water-soluble index (WSI) is 38.44%, the fulvic acid content is 15.24 wt%, and the specific surface area is 199.82 m 2 / g;

[0091] (3) Mix the pyrolyzed sludge obtained in step (2) with inositol (purity 99%), copper sulfate pentahydrate, and potassium silicate (modulus 2.5) using a high-speed shear mixer (1000 rpm, 12 min, the mass ratio of pyrolyzed sludge, inositol, anhydrous copper sulfate, and potassium silicate is 94.1:2.5:0.4:3), and extrude and granulate using a twin-screw extrusion granulator. The die head pressure is 1.8 MPa, the barrel temperature is 48 °C, and then dry in a fluidized bed drying system. The inlet air temperature is 63 °C, the inlet air velocity is 1.3 m / s, and dry until the moisture content is 13.2 wt%. The particles are dense and uniform, the particle strength is 16.3 N / particle, the porosity is 41%, and the coating rate is 97.5%.

[0092] Example 2

[0093] Replace the catalytic pyrolysis temperature in step (2) of Example 1 with 160 °C, the time with 20 min, and the dehydration rate with 35 wt%, and keep other parameters the same as in Example 1.

[0094] Comparative Example 1

[0095] The difference from Example 2 is that only KOH is added in step (2), and the mass ratio of matured sludge to KOH is 100:4.5 based on the dry basis mass of the matured sludge.

[0096] Comparative Example 2

[0097] The difference from Example 2 is that only KOH and sodium α-hydroxymethylsulfonate are added in step (2), and the mass ratio of matured sludge, KOH, and sodium α-hydroxymethylsulfonate is 100:4.5:2.5 based on the dry basis mass of the matured sludge.

[0098] Test the fulvic acid content, water solubility index, and specific surface area of the pyrolyzed sludge in Example 2, Comparative Example 1, and Comparative Example 2, and the results are shown in Table 1.

[0099] Table 1 Fulvic acid content, water solubility index (WSI), and specific surface area of the pyrolyzed sludge in Example 2, Comparative Example 1, and Comparative Example 2

[0100] Humic acid content wt% WSI% <![CDATA[Specific surface area m 2 / g]]> Comparative Example 1 5.48 22.34 101 Comparative Example 2 10.62 28.62 144.43 Example 2 15.24 38.44 199.82

[0101] As can be seen from Table 1, the content of fulvic acid (FA) in Example 2 increased by 178% compared with that in Comparative Example 1, and Comparative Example 2 was the intermediate value (an increase of 94%), indicating that the catalytic efficiency in Example 2 was significantly optimized. The WSI of Example 2 increased by 72% compared with that in Comparative Example 1, showing a significant enhancement in the hydrophilicity of the product. The specific surface area of Example 2 increased by 98% compared with that in Comparative Example 1, reflecting a substantial improvement in the pore structure of the material. The possible reasons are as follows: Comparative Example 1 was the basic treatment group without introducing an efficient catalytic system, resulting in limited generation of FA, a dense structure (low specific surface area), and poor water solubility. In Comparative Example 2, KOH + SMS was added, which partially promoted the sulfomethylation conversion of humic acid modification, but the synergistic effect was insufficient. Example 2 used a KOH + Fe 3+ + SMS composite catalytic system to achieve efficient generation and structural optimization of FA through the synergistic effects of alkali activation, oxidative cleavage, and sulfonation modification.

[0102] The fulvic acid content, phenolic hydroxyl density, quinone group content, molecular weight distribution, and water solubility index of the pyrolyzed sludge in Example 2 and Comparative Example 1 are shown in Table 2.

[0103] Table 2 Fulvic acid content, phenolic hydroxyl density, quinone group content, molecular weight distribution, and water solubility index of the pyrolyzed sludge in Example 2 and Comparative Example 1

[0104] Parameter Example 2 Comparative Example 1 Improvement rate Detection method Humic acid content (FA) 15.24 wt% 5.48 wt% 178％ NY / T3161 - 2017 Density of phenolic hydroxyl groups 1.5 mmol / g 0.4 mmol / g 275％ Folin - Ciocalteu method Quinone group content (C=O) 1.1 mmol / g 0.2 mmol / g 450％ UV - Vis quantitative method Molecular weight distribution index (Mw / Mn) 2.22 3.65 Decreased by 39.18% GPC (PEG standard sample) Water solubility index (WSI) 38.44％ 22.34％ 72％ GB / T35818 - 2018

[0105] As can be seen from Table 2, the catalytic system in Example 2 significantly increased the fulvic acid content, probably by promoting the decomposition or directional conversion of organic matter through catalytic reactions. The increase in the fulvic acid content helps to enhance the biological activity of humic acid (such as soil improvement and plant growth regulation). The catalytic system in Example 2 greatly increased the phenolic hydroxyl density, indicating that the catalytic system may introduce more phenolic hydroxyl structures through oxidation or condensation reactions. Phenolic hydroxyl is an important active group of humic acid, and the increase in its density can enhance antioxidant capacity, metal chelation ability, and the adsorption performance of environmental pollutants. The increase in the quinone group content was the largest (450%), indicating that the catalytic system in Example 2 significantly promoted the oxidation reaction to generate quinone structures. The catalytic system in Example 2 made the molecular weight distribution narrower (Mw / Mn decreased from 3.65 to 2.22), and the catalytic system in Example 2 effectively controlled the uniformity of the polymerization reaction.

[0106] Comparative Example 2

[0107] Replace the die head pressure in step (3) of Example 1 with 1.0 MPa, and keep other parameters the same as those in Example 1. The obtained particles are loose, with a strength of 8.5 N / particle and a porosity of 28%.

[0108] Comparative Example 3

[0109] Replace the die head pressure in step (3) of Example 1 with 2.5 MPa, and keep other parameters the same as those in Example 1. The obtained particles have surface cracks, the strength is 13.2 N / particle, and the porosity is 33%.

[0110] It can be seen from Example 1 and Comparative Examples 2-3 that the extrusion granulation pressure in Example 1 is more appropriate, taking into account both strength and pore structure.

[0111] Field application verification

[0112] In the field plot experiment, using the saline-alkali improver prepared in Example 1, two application rates of 200 kg / mu (W200) and 400 kg / mu (W400) were set, plus a blank control (CK), with a total of 3 treatments and three replicates, resulting in a total of 9 plots. The width of each plot is 2.28 m / seed sowing width × 4 seed sowing widths = 9.12 m, the length is 14.6 m, and the area is 133.152 m 2 The plot arrangement is shown in Table 3. The saline-alkali improver was applied together with the base fertilizer before spring land preparation, and other management measures were the same as the local management level.

[0113] Table 3 Plot arrangement table during the field plot experiment

[0114] Ⅰ W200 W400 CK Ⅱ W400 CK W200 Ⅲ CK W200 W400

[0115] The experimental field is located in Yingawat Village, Yingmaili Township, Jiashi County, Kashgar Region. The selected plot of the experimental field is flat, neat, with uniform fertility and is a representative plot. The soil texture is clay, the soil fertility level is low. Before cotton sowing, the basic soil sample has an organic matter content of 5.90 g / kg, total nitrogen of 0.29 g / kg, available nitrogen of 51.3 mg / kg, available phosphorus of 8.90 mg / kg, available potassium of 247 mg / kg, pH value of 8.35, total salt of 11.4 g / kg, and CEC of 4.19 cmol / kg.

[0116] The test crop is cotton, and the variety is Tahe No. 2. Wide-film covering (the width of the plastic film is 2.08 m), drip irrigation under the film planting mode, 1 film with 6 rows and 3 bands, the row spacing configuration of the cultivation mode is (10 + 66 + 10 + 66 + 10) + 66 cm, the plant spacing is 11 cm, and the theoretical plant number is 15,950 plants / mu. The plots were demarcated on April 11, 2024. The saline-alkali improver prepared in Example 1 was applied in combination with the base fertilizer, and the land was plowed and prepared. Sowing was carried out on April 16. A total of 10 irrigations were carried out during the whole growth period, with an irrigation quota of 320 m³ / mu, 28 - 35 m³ / mu for each irrigation. Topdressing was carried out 8 times, with 45 kg / mu of urea, 15 kg / mu of monoammonium phosphate, and 20 kg / mu of potassium dihydrogen phosphate for topdressing during the growth period. Chemical regulation with mepiquat chloride was carried out 7 times during the whole growth period, with a total dosage of 25 g / mu.

[0117] Determination of soil physical and chemical properties: Before the experiment, basic soil samples were collected. According to the requirements of the "Technical Specification for Soil Testing and Formulated Fertilization", 0-20 cm mixed soil was collected, air-dried naturally indoors, passed through a 2 mm sieve, and thoroughly mixed. Then, pH value, CEC, total salt, eight major ions, organic matter, total nitrogen, available nitrogen, available phosphorus, and available potassium were measured.

[0118] Investigation of plant physiological properties: Cotton plant emergence rate, plant height, number of main stem leaves, etc.

[0119] Yield determination: The cotton yield was measured by selecting 3 points in each plot. For the cotton with uniform growth and representativeness, a 4-meter-long film was selected, and the number of plants, number of bolls, single boll weight, lint percentage, etc. were investigated to calculate the mu yield of seed cotton. <s

[0120] The cotton emergence rates of the W200, W400, and CK groups are shown in Table 4.

[0121] Table 4 Cotton emergence rates of the W200, W400, and CK groups (%)

[0122] Ⅰ Ⅱ Ⅲ Average + / - CK 60.0 62.5 66.7 63.1±3.37b - W200 71.2 69.2 70.0 70.1±1.02a 7.0 W400 73.4 76.7 72.3 74.1±2.27a 11.0

[0123] It can be seen from Table 4 that compared with the control, the cotton emergence rates of the W400 and W200 treatments increased by 11.0 and 7.0 percentage points respectively, both reaching significant differences, indicating that the application of the saline-alkali ameliorant of the present invention can significantly increase the cotton emergence rate; there is no significant difference between the W400 treatment and the W200 treatment.

[0124] The cotton plant heights and numbers of main stem leaves of the W200, W400, and CK groups are shown in Table 5.

[0125] Table 5 Cotton plant heights and numbers of main stem leaves of the W200, W400, and CK groups

[0126]

[0127] It can be seen from Table 5 that compared with the control, the cotton plant heights were all increased to varying degrees after the treatment with the saline-alkali ameliorant, indicating that the growth of cotton can be promoted after the application of the saline-alkali ameliorant, and the difference of W400 is significant; the numbers of main stem leaves of cotton also increased to varying degrees, and the difference of W400 is significant, indicating that the saline-alkali ameliorant can also accelerate the cotton growth process to varying degrees; there is no significant difference in plant height and number of main stem leaves between the W400 and W200 treatments with different dosages of the saline-alkali ameliorant.

[0128] The cotton yield structures of the W200, W400, and CK groups are shown in Table 6.

[0129] Table 6 Cotton yield structures of the W200, W400, and CK groups

[0130]

[0131] As can be seen from Table 6, compared with the control, there were significant differences in the cotton yields treated with the saline-alkali improver, indicating that the saline-alkali improver could significantly improve the emergence rate, thereby increasing the effective harvested cotton plants, and further effectively increasing the cotton yield. The cotton yields of the W400 treatment and the W200 treatment were 353.2 kg / mu and 344.6 kg / mu respectively, with an increase of 39.7 kg and 31.1 kg compared with the cotton yield of 313.5 kg / mu of the control, and the increase rates were 12.7% and 9.9% respectively; there were significant differences between the W400 treatment and the W200 treatment.

[0132] The pH values of the basic soil samples, W200, W400 and CK group after treatment are shown in Table 7.

[0133] Table 7 pH values of the basic soil samples, W200, W400 and CK group after treatment

[0134]

[0135] As can be seen from Table 7, after a growth period of cotton, there were no significant differences in the change of the pH value of the soil treated with the control. The pH values of the soils treated with the saline-alkali improver all decreased significantly compared with those before the experiment (basic soil samples), and there was a trend of gradual decrease in the pH value with the increase of the application rate. The pH value of the soil treated with W400 decreased by 0.21, and that of the W200 treatment decreased by 0.16; there were significant differences compared with the control (CK). Compared with the control (CK) treatment, the saline-alkali improver treatments decreased by 0.23 and 0.18 respectively.

[0136] The total salts of the basic soil samples, W200, W400 and CK group after treatment are shown in Table 8.

[0137] Table 8 Total salts of the basic soil samples, W200, W400 and CK group after treatment

[0138]

[0139]

[0140] As can be seen from Table 8, compared with the basic soil samples before cotton planting, the salts in the soil decreased to a certain extent after a growth period of cotton, and the differences all reached a significant level; the natural desalination rate of the soil treated with the control after a growth period was 8.8%, and the desalination rates of the soils treated with W400 and W200 reached 21.9% and 18.4% respectively. Compared with the control (CK) treatment, the W200 and W400 treatments significantly reduced the total water-soluble salt content in the soil by 1.1 g / kg and 1.5 g / kg respectively, and both reached a significant difference level; with the increase of the dosage of the saline-alkali improver, the reduction range of the total salt increased, but the difference was not significant.

[0141] The cation exchange capacity (CEC) of the basic soil sample, W200, W400, and CK group after treatment is shown in Table 9.

[0142] Table 9 Cation exchange capacity of the basic soil sample, W200, W400, and CK group after treatment

[0143]

[0144] The cation exchange capacity (CEC) of soil can be used as an index to evaluate the soil's fertilizer retention capacity. It is the main source of the soil's buffering performance and an important basis for soil improvement and rational fertilization. As can be seen from Table 9, the CEC of the control treatment soil without applying the saline-alkali modifier increased after one cotton growth period compared with the basic soil sample, but the difference was not significant. Compared with the basic soil sample before the experiment, the CEC of the soil treated with the saline-alkali modifier increased significantly, and the increase amplitude also reached a significant difference compared with the control treatment (CK).

[0145] The contents of eight major ions in the plow layer of the basic soil sample, W200, W400, and CK group after treatment are shown in Table 10.

[0146] Table 10 Contents of eight major ions in the plow layer of the basic soil sample, W200, W400, and CK group after treatment (g / kg)

[0147]

[0148] The eight major ions in the 0-20 cm plow layer of the soil mainly include CO3 2- , HCO3 － , Cl － , SO4 2－ , Ca 2+ , Mg 2+ , Na + , K + . As can be seen from Table 10, compared with the basic soil sample before cotton planting, after one cotton growth period, among the eight major ions of soil salinity, HCO 3－ , Cl － , SO4 2－ , K + , Na + , Mg 2+ all decreased to varying degrees, and this downward trend became more significant with the increase in the dosage of the saline-alkali modifier; the Ca 2+ of the total soil salt increased significantly, and with the increase in the application amount of the saline-alkali modifier, the influence amplitude also gradually increased.

[0149] The soil nutrients of the basic soil sample, W200, W400, and CK group after treatment are shown in Table 11.

[0150] Table 11 Soil Nutrients after Treatment of Basic Soil Samples, W200, W400 and CK Groups

[0151]

[0152] As can be seen from Table 11, compared with the basic soil samples, the soil organic matter, total nitrogen, and available phosphorus in each treatment increased significantly, while the soil available nitrogen (alkali-hydrolyzable nitrogen) and available potassium decreased slightly; compared with the control, the soil organic matter, total nitrogen, and available phosphorus in the treatment with the saline-alkali modifier increased, and showed an increasing trend with the increase in the dosage of the saline-alkali modifier, the soil available nitrogen (alkali-hydrolyzable nitrogen) decreased, and the available potassium decreased slightly.

[0153] In summary, the saline-alkali modifier prepared by the present invention can significantly increase the cotton yield. The cotton yields of the W400 treatment and the W200 treatment are 353.2 kg / mu and 344.6 kg / mu respectively, which are 39.7 kg and 31.1 kg higher than the cotton yield of 313.5 kg / mu in the control treatment, and the yield increase rates are 12.7% and 9.9% respectively; it can significantly reduce the soil pH value and total salt. Compared with the control (CK), the pH values of the W400 and W200 treatments decreased by 0.23 and 0.18 respectively, and the total water-soluble salt content in the soil decreased by 1.5 g / kg and 1.1 g / kg respectively; it can significantly increase the soil desalination rate and CEC. Compared with the control (CK), the soil CEC of the W400 and W200 treatments increased by 0.76 cmol / kg and 0.64 cmol / kg respectively. After the saline-alkali modifier prepared by the present invention is applied to moderately salinized cotton fields in Xinjiang, it can significantly improve the physical and chemical properties of the soil, increase the content of soil nutrients such as organic matter, total nitrogen, and available phosphorus to a certain extent, has a good improvement effect on moderately saline-alkali soils in Xinjiang, and has a significant effect on improving cotton emergence, promoting growth, and increasing yield.

[0154] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a saline-alkali improver, comprising the following steps: (1) Mix sludge with a lignocellulosic conditioner, and successively carry out aerobic fermentation, composting and aging to obtain composted sludge; (2) Mix the composted sludge obtained in step (1) with potassium hydroxide, sodium α-hydroxymethylsulfonate and an iron salt, and carry out catalytic pyrolysis to obtain pyrolyzed sludge; (3) Mix the pyrolyzed sludge obtained in step (2) with inositol, a copper salt and potassium silicate, and successively carry out extrusion granulation and drying to obtain the saline-alkali improver.

2. The preparation method according to claim 1, characterized in that, In step (1), based on the dry basis mass of the sludge, the mass ratio of the sludge to the lignocellulosic conditioner is 100:(4 - 6).

3. The preparation method according to claim 1, characterized in that, In the step (1), the temperature of aerobic fermentation is 60 - 65°C, the oxygen supply amount of aerobic fermentation is ≥ 0.5 m 3 / (m 3 ·min), and the time of aerobic fermentation is ≥ 120 h.

4. The preparation method according to claim 1, characterized in that, The aging time in step (1) is 90 - 120 d.

5. The preparation method according to claim 1, wherein In step (2), based on the dry basis mass of the composted sludge, the mass ratio of the composted sludge, potassium hydroxide, sodium α-hydroxymethylsulfonate and the iron salt is 100:(4 - 5):(2 - 3):(0.1 - 0.2).

6. The preparation method according to claim 1, wherein, In step (2), the temperature of the catalytic pyrolysis is 150 - 170 °C, and the time of the catalytic pyrolysis is 20 - 25 min.

7. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of the pyrolyzed sludge, inositol, the copper salt and potassium silicate is (92 - 96):(2 - 3):(0.3 - 0.5):(2 - 4).

8. The preparation method according to claim 1, characterized in that, In step (3), the pressure of the extrusion granulation is 1.5 - 2 MPa.

9. A saline-alkali improver prepared by the preparation method according to any one of claims 1 - 8.

10. Use of the saline-alkali improver according to claim 9 in soil improvement.

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