Soil water-retaining agent, its preparation method and application

Abstract

The application relates to the technical field of environmental treatment, and particularly discloses a soil water-retaining agent, a preparation method and application thereof, wherein the soil water-retaining agent is composed of the following components in parts by weight: vermiculite powder 5-20 parts, wheat straw powder 10-30 parts, peat soil 10-30 parts, attapulgite 10-20 parts, acrylic acid 40-60 parts and acrylamide 5-10 parts. The soil water-retaining agent can improve the water-retaining capacity of soil, increase the organic matter content of soil and reduce the cadmium content in soil.

Description

Technical Field

[0001] This invention relates to the field of environmental remediation technology, specifically to a soil water-retaining agent, its preparation method, and its application. Background Technology

[0002] Soil water-retaining agents are a chemically-based drought-resistant, water-saving, and yield-increasing technology that has garnered significant attention in recent years, and their application in agricultural production is increasingly promising. As a high-molecular polymer with strong water absorption capacity, water-retaining agents can repeatedly absorb and release water, thereby loosening the soil, reducing the rate of water evaporation, and playing a role in drought resistance, water retention, and soil and water conservation. This provides a suitable water environment for crops and promotes crop growth. However, the water-retaining agents currently on the market are diverse, with complex compositions, numerous manufacturing processes, high costs, and most pose significant safety risks, leading to secondary environmental pollution. Therefore, finding a soil water-retaining agent with safe raw materials and no pollution is particularly important. Summary of the Invention

[0003] To develop a safe and environmentally friendly soil water-retaining agent, this invention provides a soil water-retaining agent, its preparation method, and its application. The soil water-retaining agent provided by this invention is used to improve soil water retention capacity, increase soil organic matter content, and reduce cadmium content in the soil.

[0004] The present invention provides a soil water-retaining agent, which is made of the following components in parts by weight: 5 to 20 parts vermiculite powder, 10 to 30 parts wheat straw powder, 10 to 30 parts peat moss, 10 to 20 parts attapulgite, 40 to 60 parts acrylic acid, and 5 to 10 parts acrylamide. The raw materials were weighed according to the weight proportions, and the acrylic acid was neutralized with an alkaline solution. Vermiculite powder, wheat straw powder, peat moss, attapulgite clay and acrylamide were added to the mixture to obtain a mixture. After adding a crosslinking agent and an initiator to the mixture, a crosslinking reaction was carried out. The obtained product was dried and ground to obtain a water-retaining agent.

[0005] This invention addresses existing acrylic water-retaining agents by crosslinking a certain amount of straw powder, vermiculite powder, attapulgite, and peat moss. The acrylic water-retaining agent serves as the base material, while the straw powder, peat moss, and vermiculite powder act as functional synergists, enhancing soil water retention capacity while providing nutrients. The attapulgite moss, in turn, can passivate heavy metals in the soil, thereby improving soil quality.

[0006] Furthermore, the soil water-retaining agent is composed of the following components in parts by weight: 20 parts vermiculite powder, 30 parts wheat straw powder, 20 parts peat moss, 20 parts attapulgite, 60 parts acrylic acid, and 10 parts acrylamide.

[0007] Furthermore, the soil water-retaining agent is composed of the following components in parts by weight: 10 parts vermiculite powder, 20 parts wheat straw powder, 20 parts peat moss, 10 parts attapulgite, 60 parts acrylic acid, and 5 parts acrylamide.

[0008] The present invention also provides a method for preparing the aforementioned soil water-retaining agent, comprising the following steps: The raw materials were weighed according to the weight proportions, and the acrylic acid was neutralized with an alkaline solution. Vermiculite powder, wheat straw powder, peat moss, attapulgite clay and acrylamide were added to the mixture to obtain a mixture. After adding a crosslinking agent and an initiator to the mixture, a crosslinking reaction was carried out. The obtained product was dried and ground to obtain a water-retaining agent.

[0009] Furthermore, the mass ratio of the crosslinking agent to the initiator is 1 to 1.5:1.

[0010] Furthermore, the crosslinking agent is N,N-methylenebisacrylamide.

[0011] Furthermore, the initiator is potassium persulfate.

[0012] Furthermore, the crosslinking reaction is carried out at 60℃~65℃ for 0.2h~0.3h.

[0013] Furthermore, the drying and grinding process is as follows: the product obtained by the cross-linking reaction is dried at 70℃~75℃ for 24 h~26 h, granulated, crushed and ground through an 85~100 mesh sieve to obtain a water-retaining agent.

[0014] The present invention also provides the application of the soil water-retaining agent in improving the soil environment, wherein the soil water-retaining agent is used to improve the soil's water retention capacity, increase the soil's organic matter content, and reduce the cadmium content in the soil.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The soil water-retaining agent of this invention has a simple and easy-to-promote formula, uses economical and safe raw materials, does not cause environmental pollution, and can be used to improve soil water retention capacity, increase soil organic matter content, reduce soil cadmium content, and protect soil quality.

[0016] This invention addresses existing acrylic water-retaining agents by crosslinking a certain amount of straw powder, vermiculite powder, attapulgite, and peat moss. The acrylic water-retaining agent serves as the base material, while the straw powder, peat moss, and vermiculite powder act as functional synergists, enhancing soil water retention capacity while providing nutrients. Attapulgite moss can passivate heavy metals in the soil, thereby improving soil quality. Furthermore, the raw materials used in this invention are economical and simple, and will not impose a significant burden on the environment. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 The effect of the soil water-retaining agent prepared according to the present invention on the soil water retention capacity.

[0019] Figure 2 The effect of the soil water-retaining agent prepared in this invention on soil organic matter content; different lowercase letters indicate significant differences at the P<0.05 level; all data are the mean ± standard error of three replicates.

[0020] Figure 3 The effect of the soil water-retaining agent prepared according to the present invention on the available Cd in the soil.

[0021] Figure 4 The effect of the soil water-retaining agent prepared for the invention on soil DOC. Detailed Implementation

[0022] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0023] The source information of the raw materials used in this invention is as follows: Vermiculite powder was purchased from Hebei Hongyao Mineral Products Processing Co., Ltd., with a particle size of 100 mesh; wheat straw powder was purchased from Taobao Su Rui Agricultural Products Processing, with a particle size of 100 mesh; peat moss was purchased from Chenxing Agricultural Co., Ltd., with a particle size of 50 mesh; attapulgite was purchased from Xincheng Mining Co., Ltd., produced in Ulanqab, Inner Mongolia, and is classified as earthy palygorskite with a particle size of 200 mesh; acrylic acid and acrylamide were purchased from Maclean's Shanghai Biotechnology Co., Ltd., with CAS numbers 79-10-7 and 79-06-1.

[0024] Example 1: A soil water-retaining agent and its preparation method.

[0025] Take 60ml of acrylic acid, add 16.7g of NaOH and 240ml of water to neutralize the acrylic acid, prepare an acrylic acid solution with a mass percentage of 20% and a degree of neutralization of 50%, then add 20g of vermiculite powder, 30g of wheat straw powder, 20g of peat moss, 20g of attapulgite, and 10g of acrylamide in sequence and mix to obtain a mixture. 1g of N,N-methylenebisacrylamide was added to the mixture as a crosslinking agent and stirred until fully dissolved. Then, 1g of potassium persulfate was added as an initiator, and the crosslinking reaction was carried out at 65℃ for 0.2h to obtain a solid product. The product was then dried at 70℃ for 24h, granulated, dried at 70℃ for 24h, pulverized and ground through a 100-mesh sieve to obtain the water-retaining agent.

[0026] Example 2: A soil water-retaining agent and its preparation method.

[0027] Take 60ml of acrylic acid, add 16.7g of NaOH and 240ml of water to neutralize the acrylic acid, prepare an acrylic acid solution with a mass percentage of 20% and a degree of neutralization of 50%, then add 10g of vermiculite powder, 10g of wheat straw powder, 20g of peat moss, 10g of attapulgite, and 5g of acrylamide in sequence and mix to obtain a mixture. 1g of N,N-methylenebisacrylamide was added to the mixture as a crosslinking agent and stirred until fully dissolved. Then, 1g of potassium persulfate was added as an initiator, and the crosslinking reaction was carried out at 60℃ for 0.3h to obtain a solid product. The product was then dried at 70℃ for 24h, granulated, dried at 72℃ for 24h, pulverized and ground through a 100-mesh sieve to obtain the water-retaining agent.

[0028] Example 3: A soil water-retaining agent and its preparation method.

[0029] Take 40 ml of acrylic acid, add 11.1 g of NaOH and 160 ml of water to neutralize the acrylic acid, and prepare an acrylic acid solution with a mass percentage of 20% and a degree of neutralization of 50%. Then add 5 g of vermiculite powder, 20 g of wheat straw powder, 10 g of peat moss, 15 g of attapulgite, and 7 g of acrylamide in sequence and mix to obtain a mixture. Add 1.5g of N,N-methylenebisacrylamide as a crosslinking agent to the mixture, stir until fully dissolved; then add 1g of potassium persulfate as an initiator, and crosslink at 65℃ for 0.2h to obtain a solid product, then dry at 70℃ for 24h, granulate, then dry at 75℃ for 26h, pulverize and grind through a 100-mesh sieve to obtain the water-retaining agent.

[0030] Comparative Example 1: A soil water-retaining agent and its preparation method.

[0031] Take 60ml of acrylic acid, add 16.7g of NaOH and 240ml of water to neutralize the acrylic acid, prepare an acrylic acid solution with a mass percentage of 20% and a degree of neutralization of 50%, then add 10g of vermiculite powder, 20g of peat moss, 20g of attapulgite, and 10g of acrylamide in sequence and mix to obtain a mixture. 1g of N,N-methylenebisacrylamide was added to the mixture as a crosslinking agent and stirred until fully dissolved. Then, 1g of potassium persulfate was added as an initiator, and the crosslinking reaction was carried out at 65℃ for 0.2h to obtain a solid product. The product was then dried at 70℃ for 24h, granulated, dried at 70℃ for 24h, pulverized and ground through a 100-mesh sieve to obtain the water-retaining agent.

[0032] Comparative Example 2: A soil water-retaining agent and its preparation method.

[0033] Take 60ml of acrylic acid, add 16.7g of NaOH and 240ml of water to neutralize the acrylic acid, and prepare an acrylic acid solution with a mass percentage of 20% and a degree of neutralization of 50%. Then add 30g of wheat straw powder, 10g of vermiculite powder, 20g of peat moss and 10g of acrylamide in sequence and mix to obtain a mixture. 1g of N,N-methylenebisacrylamide was added to the mixture as a crosslinking agent and stirred until fully dissolved. Then, 1g of potassium persulfate was added as an initiator, and the crosslinking reaction was carried out at 65℃ for 0.2h to obtain a solid product. The product was then dried at 70℃ for 24h, granulated, dried at 70℃ for 24h, pulverized and ground through a 100-mesh sieve to obtain the water-retaining agent.

[0034] The soil water-retaining agents prepared using Examples 1-2 and Comparative Examples 1-2 were tested for their water absorption rates of deionized water and 0.9% saline solution. The specific experimental procedures are as follows: Water absorption capacity is the fundamental indicator for judging soil water-retaining agents, and it is commonly expressed as the water absorption ratio. First, weigh 1g of the water-retaining agent into a beaker, then add distilled water and 0.9% saline solution respectively. After swelling to water saturation at room temperature, let it stand under a 200-mesh sieve for 30 minutes, then weigh the mass of the water-retaining agent at this point and calculate the water absorption ratio. The water absorption ratio is calculated using the following formula:

[0035] Q= (m1-m2) / m2 In the formula, Q---water absorption ratio, g / g; m1---mass of the water-retaining agent after water absorption saturation, g; m2---mass of the water-retaining agent before water absorption, g; Table 1 shows the water absorption rate of the prepared soil water-retaining agent. Example 1 59.71 28.03 Example 2 56.66 23.50 Comparative Example 1 34.78 15.42 Comparative Example 2 42.21 16.38 The test results are shown in Table 1. The soil water-retaining agent prepared in Example 1 above had the highest water absorption rate for deionized water and 0.9% saline solution, while the water absorption rates of Comparative Examples 2 and 3 were significantly lower than those of Examples 1 and 2. Application Examples: Taking the soil water-retaining agents prepared in Examples 1 and 2 as examples, the effects on soil biochemical properties were studied. The soil used in the experiment was collected from Hengkou Town, Hanbin District, Ankang City, Shaanxi Province, and is a typical cadmium-contaminated soil.

[0036] Five portions of 500g of air-dried soil that had passed through a 2mm sieve were weighed. The first portion served as a blank control group and was designated CK. The second portion was a soil mixture obtained by adding 2g of the soil water-retaining agent prepared in Example 1 and was designated Example 1. The third portion was a soil mixture obtained by adding the soil water-retaining agent prepared in Example 2 and was designated Example 2. The fourth portion was a soil mixture obtained by adding the soil water-retaining agent prepared in Example 3 and was designated Comparative Example 1. The fifth portion was a soil mixture obtained by adding the soil water-retaining agent prepared in Example 4 and was designated Comparative Example 2. The soil mixtures of the above examples were each added to a beaker, and then 250ml of deionized water was added to each beaker. After the soil mixtures had completely absorbed the deionized water, they were placed in the greenhouse of Northwest A&F University for cultivation. During the experiment, the temperature in the greenhouse was set at 25℃, and the cultivation lasted for 11 days.

[0037] Soil moisture content was measured every 48 hours in soil mixtures from CK, Example 1, Example 2, Comparative Example 1, and Comparative Example 2. Finally, on day 11, soil organic matter content, available Cd content, and soluble organic carbon (DOC) content were measured. Specific testing methods are as follows:

[0038] Soil moisture content: Take 4g of soil samples and spread them evenly in weighing bottles that have been dried to constant weight. Open the caps and dry at 100℃~105℃ for 8 hours. Close the caps, transfer the bottles to a desiccator, cool for 30 minutes, and determine their mass. Repeat the drying process at the same temperature for 1 hour, cool, and weigh until the difference between two consecutive weighings does not exceed 5mg. Calculate the moisture content (%) of the sample based on the weight loss.

[0039] Calculation formula: Moisture content = (W total - W1 / W total - W bottle) * 100%.

[0040] W1 is the weight of the bottle and sample after constant weight (g); W_bottle is the weight of the weighing bottle after constant weight (g); W_total is the weight of the weighing bottle plus the sample (g).

[0041] Soil organic matter content: The organic matter content in soil samples was determined using the H2SO4-K2Cr2O7 oxidation method.

[0042] Available Cd content in soil: Weigh 5.00 ± 0.05 g of sample passed through a 20-mesh sieve into a 100 mL polyethylene centrifuge tube, add 25 mL of DTPA extraction solution with pH = 7.30 ± 0.05, and shake on a horizontal shaker at 180 r / min for two hours at 25 ± 2℃ (temperature must be strictly controlled). Remove the dry filter (filter with rapid qualitative filter paper), discard the initial filtrate (5 mL), and filter the remaining filtrate into a 50 mL PP digestion tube. The filtrate is analyzed by the AAS method.

[0043] Soil dissolved organic carbon (DOC) content: The dissolved organic carbon (DOC) content in rhizosphere soil was determined using a total organic carbon analyzer (TOC-L, Shimadzu, Japan). Specifically, soil and deionized water were mixed at a ratio of 1:10000 (w / v) and shaken on a shaker for 24 h. The mixture was then centrifuged at 5000 × g for 10 min, and the supernatant was filtered through a 0.45 μm aqueous filter membrane. Finally, the extract was analyzed using the total organic carbon analyzer.

[0044] The results are as follows: 1. The impact of soil water-retaining agents on soil water retention capacity The results are as follows Figure 1 As shown, after applying the soil water-retaining agents prepared in Examples 1 and 2, there was no significant difference in water retention capacity between the two. However, the soil water retention capacity of Comparative Examples 1 and 2 was significantly reduced compared to Examples 1 and 2. Nevertheless, the soil moisture content after adding the water-retaining agent was significantly higher than that of the control (CK) at all time points, with a maximum increase of 12% compared to the CK. This result indicates that applying the water-retaining agent can improve soil water retention capacity and reduce soil moisture loss.

[0045] 2. The effect of soil water-retaining agents on soil organic matter content Furthermore, this invention measured the soil organic matter content after the addition of a water-retaining agent, and obtained the following results: Figure 2 The results are shown. Adding the soil water-retaining agents prepared in Examples 1, 2, and 2 (Comparative Example 2) all significantly increased the organic matter content in the soil. The organic matter content in the soils of Examples 1, 2, and 2 (Comparative Example 2) increased by 38.4%, 57.2%, and 33.5% compared to the control (CK), respectively, while Comparative Example 1 showed no significant difference. These results indicate that the water-retaining agent obtained by adding wheat straw powder according to the present invention can significantly increase the soil organic matter content.

[0046] 3. Effects of different components of soil water-retaining agents on available Cd in soil like Figure 3As shown, the soil available Cd content significantly decreased after adding the soil water-retaining agents prepared in Examples 1 and 2, with a maximum reduction of 0.025 mg / kg. While the soil available Cd content decreased after adding Comparative Example 1, the difference was not significant, and Comparative Example 2 did not show a decreasing trend compared to the control (CK). This may be because the attapulgite added to the raw materials is a soil passivating agent that can reduce the soil available Cd content, thereby mitigating the environmental hazards of Cd pollution to a certain extent.

[0047] 4. Effects of different components of soil water-retaining agents on soil DOC like Figure 4 As shown, the soil DOC content all showed an increasing trend after adding the soil water-retaining agents prepared in Examples 1 and 2 of this invention, as well as Comparative Examples 1 and 2, with Example 2 showing the largest increase. DOC, as a relatively fast-moving and unstable portion of organic carbon in the soil, readily combines with Cd in the soil. 2+ Complexation, therefore, the significant increase in DOC content after the addition of water-retaining agents may be an important factor causing the reduction of available Cd in the soil.

[0048] In summary, this invention significantly improves soil water retention capacity and increases soil organic matter content, while also significantly reducing available Cd content. This is because the addition of straw powder increases the organic matter content of the soil water-retaining agent. After application to the soil, the organic matter enters the soil and, together with the attapulgite in the water-retaining agent, binds with heavy metal ions, thereby reducing the bioavailability of heavy metals. Furthermore, vermiculite powder and peat moss, along with straw powder and attapulgite, increase the water absorption and retention capacity of the soil water-retaining agent and result in a higher organic matter content. Therefore, the addition of this water-retaining agent to the soil significantly increases the soil DOC content due to the increased organic matter content. On the other hand, DOC readily complexes with available Cd in the attapulgite raw materials, thus achieving Cd passivation in the soil. Therefore, this invention can improve soil water retention capacity and reduce the harm of Cd pollution in the soil, thus having broad application prospects.

[0049] Although preferred embodiments of the invention have been described, those skilled in the art, once they have learned the basic inventive concept, can make other changes and modifications to these embodiments.

[0050] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A soil water-retaining agent for increasing soil organic matter content and reducing cadmium content in soil, characterized in that, The soil water-retaining agent is made from the following components in parts by weight: 10 parts vermiculite powder, 10 parts wheat straw powder, 20 parts peat moss, 10 parts attapulgite, 60 parts acrylic acid, and 5 parts acrylamide; the soil water-retaining agent is prepared by the following method: The raw materials were weighed according to the weight proportions. After neutralizing the acrylic acid with an alkaline solution, vermiculite powder, wheat straw powder, peat moss, attapulgite clay and acrylamide were added to obtain a mixture. After adding a crosslinking agent and an initiator to the mixture, a crosslinking reaction was carried out. The obtained product was dried and ground to obtain a water-retaining agent. The soil water-retaining agent is used to improve the soil's water retention capacity, increase the soil's organic matter content, and reduce the cadmium content in the soil.

2. A method for preparing the soil water-retaining agent according to claim 1, characterized in that, Includes the following steps: The raw materials were weighed according to the weight proportions. After neutralizing the acrylic acid with an alkaline solution, vermiculite powder, wheat straw powder, peat moss, attapulgite clay and acrylamide were added to obtain a mixture. After adding a crosslinking agent and an initiator to the mixture, a crosslinking reaction was carried out. The obtained product was dried and ground to obtain a water-retaining agent. The mass ratio of the crosslinking agent to the initiator is 1:1; The crosslinking agent is N,N-methylenebisacrylamide; The initiator is potassium persulfate; The crosslinking reaction was carried out at 60°C for 0.3 h; The drying and grinding process is as follows: the product obtained by the cross-linking reaction is dried at 72°C for 24 hours, granulated, crushed and ground through a 100-mesh sieve to obtain a water-retaining agent.

3. The application of the soil water-retaining agent according to claim 1 in improving the soil environment, characterized in that, The soil water-retaining agent is used to improve the soil's water retention capacity, increase the soil's organic matter content, and reduce the cadmium content in the soil.

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