Peel residue organic fertilizer and application thereof in heavy metal contaminated soil remediation

Abstract

The invention relates to the technical field of environmental protection, particularly discloses a pericarp residue organic fertilizer and application thereof in heavy metal contaminated soil remediation, and aims to solve the problem that resources cannot be recycled in the prior art. The method comprises the following steps: 1, obtaining compost raw materials: a mixture material of pineapple peel residues, rice bran and cow dung in a mass ratio of 10: 4: 1; 2, fully stirring and uniformly mixing, and watering to control the water content of the compost to be about 40-50%; 3, stacking the uniformly mixed materials into strip stacks with the height of 70-80 cm and the width of 1.5-2 m, and covering the strip stacks with a layer of thin film to facilitate temperature maintenance and fermentation promotion; 4, the fermentation period is 15-20 days, in the composting process, compost piles need to be turned over regularly to promote decomposition and fermentation of waste, agricultural organic waste is reasonably utilized, and environmental pollution caused by waste such as pericarp residues is reduced; on the other hand, pineapple peel residue compost is applied to soil remediation and fertility improvement, agricultural sustainable development is promoted, and quality safety of agricultural products is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection, in particular to fruit peel residue organic fertilizer and application thereof in the restoration of heavy metal polluted soil. Background Art

[0002] With the development of industry and agriculture, the degradation of farmland soil environmental quality and heavy metal pollution have become prominent. Heavy metals are highly toxic, easy to enrich, and difficult to decompose, which leads to the decline of soil quality and threatens the quality and safety of agricultural products. Existing soil heavy metal remediation technologies have the characteristics of high cost, slow effect, and easy reduction of soil nutrients. It is urgent to select new soil heavy metal remediation materials and methods. On the other hand, my country's pineapple production and consumption are among the highest in the world. The output of pineapple peel residues removed during the edible processing accounts for about 50%-60% of the total pineapple, resulting in a large amount of waste accumulation. Pineapple peel residue is rich in nitrogen, phosphorus, potassium and other elements, and can be used as a potential raw and auxiliary material for soil remediation and nutrient improvement. However, existing research on pineapple peel residue composting and its application in heavy metal contaminated soil rarely reports, resulting in a large amount of resource waste and environmental pollution caused by the accumulation of peel residues. Summary of the invention

[0003] The purpose of the present invention is to provide a peel residue organic fertilizer and its application in the restoration of heavy metal contaminated soil, thereby solving the problem that resources cannot be recycled in the prior art.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A method for preparing fruit peel residue organic fertilizer comprises the following steps:

[0006] Step 1: Obtain compost raw materials: a mixture of pineapple peel residue, rice bran and cow dung in a mass ratio of 10:4:1;

[0007] Step 2: Stir and mix thoroughly, and water the pile to control the moisture content to about 40%-50%;

[0008] Step 3: Pile the mixed materials into strips with a height of 70-80cm and a width of 1.5-2m, and cover them with a layer of film to help maintain temperature and promote fermentation;

[0009] Step 4: The fermentation cycle is 15-20 days. During the composting process, the compost pile needs to be turned regularly to promote the decomposition and fermentation of the waste;

[0010] Step 5: During the composting process of pineapple peel residue, the 0th to 5th day is the warming stage, the 5th to 12th day is the thermophilic stage, and cooling begins after the 12th day. The temperature of the pile gradually approaches room temperature, which means that the peel residue compost is fully decomposed.

[0011] Based on the above technical solutions, the present invention further provides the following optional technical solutions:

[0012] In an optional solution: a fermentation inoculant is added in step one. The fermentation inoculant includes a mixed fermentation inoculant of Bacillus subtilis, Trichoderma, and photosynthetic bacteria, and the fermentation inoculant is added in a ratio of 500:1 by mass of raw materials to strains.

[0013] In an optional solution: the nitrogen-carbon ratio in the compost raw materials in step one is 1:(26 - 35).

[0014] In an optional solution: sufficient air holes should be left at the edges of the film in step three to facilitate aerobic fermentation of microorganisms.

[0015] In an optional solution: in step four, when the temperature rises to 50°C / when the winter temperature reaches above 55°C, the first turning of the pile starts, and thereafter, whenever the pile temperature rises to around 60 - 70°C and is maintained for 1 - 2 days, the pile is turned.

[0016] In an optional solution: during the composting process, it is necessary to control the temperature of the compost pile. The temperature inside the pile should be maintained at 50 - 70°C. If the temperature is too high, the compost pile can be turned timely or the ventilation volume can be increased to lower the temperature; if the temperature is too low, methods such as covering with heat-insulating materials can be adopted to increase the temperature.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] In this experiment, pineapple peel residue was used as the material, and it was subjected to aerobic composting fermentation to obtain organic fertilizer with good fertilizer efficiency, which was used to passivate soil heavy metals and simultaneously improve the soil nutrient content, providing a reference for the use of agricultural waste in the remediation of heavy metal-contaminated soil. On the one hand, the project reasonably utilized agricultural organic waste and reduced environmental pollution caused by waste such as fruit peel residue; on the other hand, applying the pineapple peel residue compost to soil remediation can passivate soil heavy metals, increase the content of soil nutrients such as potassium, promote the sustainable development of agriculture, and ensure the quality and safety of agricultural products. Description of the Drawings

[0019] Figure 1 It is the process diagram of the pineapple composting of the present invention.

[0020] Figure 2 It is the passivation rate diagram of each treatment at different times of the present invention.

[0021] Figure 3 It is the change diagram of the pH and organic matter content of different treatment groups of the present invention at different passivation times.

[0022] Figure 4 It is the three-dimensional fluorescence spectrum diagram of different treated soils after passivation of the present invention.

[0023] Figure 5 This is the test report of the present invention. Specific Embodiments

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] As Figures 1-5 shown, the embodiments of the present invention provide a method for preparing organic fertilizer from fruit peel residues, including the following steps:

[0026] Step 1: Obtain compost raw materials: a mixture of pineapple peel residues, rice bran, and cow dung with a mass ratio of 10:4:1. Add a fermentation inoculant, which includes a mixed fermentation inoculant of Bacillus subtilis, Trichoderma, and photosynthetic bacteria, and add the fermentation inoculant according to the mass ratio of raw materials to the strain of 500:1;

[0027] In Step 1, the nitrogen-carbon ratio in the compost raw materials is 1:(26-35);

[0028] Step 2: Stir well and evenly, and water to control the moisture of the compost material at about 40%-50%;

[0029] Step 3: Stack the uniformly mixed materials into a strip stack with a height of 70-80 cm and a width of 1.5-2 m, and cover it with a layer of film on it, which is beneficial to maintaining the temperature and promoting fermentation;

[0030] In Step 3, enough air holes should be left at the edges of the film to facilitate aerobic fermentation of microorganisms;

[0031] Step 4: The fermentation cycle is 15-20 days. During the composting process, it is necessary to regularly turn the compost pile to promote the decomposition and fermentation of the waste;

[0032] In Step 4, when the temperature rises to 50°C / above 55°C in winter, start the first turning of the pile, and then turn the pile every time the pile temperature rises to about 60-70°C and maintain it for 1-2 days before turning the pile;

[0033] Step 5: During the composting process of pineapple peel residues, the 0-5th day is the heating-up stage, the 5-12th day is the thermophilic stage, and cooling is carried out after the 12th day, and the temperature of the pile gradually tends to room temperature, that is, the composting of the fruit peel residues is completely mature.

[0034] During the composting process, the temperature of the compost pile needs to be controlled and maintained at 50-70°C. If the temperature is too high, the compost pile can be turned over or ventilation can be increased to lower the temperature; if the temperature is too low, the temperature can be raised by covering it with insulation materials.

[0035] During the composting process of pineapple peel residue, the 0th to 5th day is the warming stage, the 5th to 12th day is the thermophilic stage, and the cooling and cooling are carried out after the 12th day. The temperature of the pile gradually approaches room temperature, that is, the compost of the peel residue is fully decomposed. Three samples are collected from the top, center and bottom of the compost, each sample is 500g, freeze-dried and ground and sieved, and its properties are determined according to the standard requirements of the Ministry of Agriculture and Rural Affairs "Organic Fertilizer" (NY / T525-2021). The remaining compost samples are sieved and packaged when the moisture content of the compost drops below 30%, and stored in a cool place;

[0036] The pineapple peel residue organic fertilizer prepared by the above method meets the standard quality requirements of "Organic Fertilizer" (NY / T 525-2021). The peel residue fertilizer is dark brown in color, dry, and cannot be pressed into blocks by hand. The material shape and outline collapse, the appearance is uniform, and it is in the form of fine particles or powder, without stench, and has a faint sour taste after compost fermentation. The analysis and test results of a third-party testing company (check whether it is necessary to specify that it is a valid test report issued by an authoritative third-party company) show that the organic fertilizer prepared by the present invention has a pH value of 8.1, an organic matter content of up to 44%, and a total nutrient content of nitrogen, phosphorus and potassium of 7.0%, of which the mass fraction of potassium (K2O) is 3.2%, which can be used as a potassium-rich fertilizer. The seed germination index (GI) is 92%, which is much higher than the standard requirements. Heavy metals As and Hg were not detected, the Pb content was 4.0 mg / kg, and the heavy metals Cr and Cd were 3.0 mg / kg and 0.2 mg / kg respectively, which met the criteria for organic fertilizer; sanitary indicators such as ascaris egg mortality rate and fecal coliform count also met the standards, making it a clean and safe organic fertilizer.

[0037]

[0038]

[0039] Table 1 Pineapple peel residue organic fertilizer index test results (on a drying basis)

[0040] Note: The detection limit of total arsenic is 0.01 mg / kg; the detection limit of total mercury is 0.003 mg / kg; Ascaris egg mortality rate is not detected, indicating that Ascaris eggs were not detected;

[0041] Compared with tea leaf compost and other commercial organic fertilizers, the pineapple peel residue organic fertilizer prepared by the present invention has simple raw materials, high organic matter content and total nutrient content, and a potassium content much higher than that of general commercial organic fertilizers. It is a natural potassium-rich fertilizer and has a good effect on the growth of potassium-requiring crops.

[0042] Table 2 shows the comparison of the main properties between the pomace organic fertilizer and other organic fertilizers

[0043]

[0044] Application of potassium-rich pomace organic fertilizer in the remediation of heavy metal contaminated soil;

[0045] Soil sample collection and chemical analysis:

[0046] The heavy metal contaminated soil was collected from the abandoned farmland around a plating factory in the Chengdu Plain. The sampling depth was 0 - 20 cm. After removing plant residues and granular stones, the soil was ground and passed through an 8 mm sieve to obtain soil samples. 5 kg of soil samples were placed in PVC flower pots with holes. Pomace compost was added according to the soil sample mass. A total of 6 treatment groups were set up: a blank control (without applying organic fertilizer) was set, denoted as CK; the addition amounts of pomace compost were applied at 0.750% and 1.50% of the soil sample mass, denoted as T1 and T2 respectively, and each treatment was repeated 3 times. The experiment was sprayed with 300 mL of water every 2 days to ensure the same dry-wet state, and continuously cultured for 60 days. Samples were taken at regular intervals. After air-drying and grinding, the samples passed through a 2 mm nylon sieve and were ready for testing;

[0047] Determination indexes and methods:

[0048] Determination of basic physical and chemical properties of soil. Soil pH was measured with a Leici PHSJ-3F pH meter; soil organic matter (OM) was determined by the external heating method of H2SO4-K2Cr2O7; total nitrogen (TN) in soil was determined by the semi-micro Kjeldahl method; total phosphorus (TP) was determined by NaOH melting spectrophotometry; total potassium (TK) was determined by NaOH melting and flame photometry; available nitrogen (AN) was determined by the alkaline hydrolysis diffusion method; available phosphorus (AP) was determined by ammonium fluoride-hydrochloric acid extraction and inductively coupled plasma spectrometry (ICP-OES); available potassium (AK) was determined by ammonium acetate extraction and flame photometry;

[0049] Determination of total amount and forms of heavy metal Pb in soil. Weighed 1.00 g of soil sample into an acid-washed polytetrafluoroethylene crucible, added 5 mL of HF and soaked overnight, then added 15 mL of a mixed acid of 1:1 HNO3 and HClO4, digested until the sample was transparent and had no obvious particles, fixed the volume with ultrapure water and passed through a 0.45 μm filter membrane, and determined the total amount of heavy metal Pb by ICP-OES. Two active state components of Pb, F1 exchangeable state (Exc) and F2 carbonate-bound state (Car), were extracted by the modified Tessier sequential extraction method. The specific operation was as follows: Weighed 1.00 g of soil sample passed through a 0.25 mm sieve into a centrifuge tube, added 10 mL of MgCl2 solution with a concentration of 1 mol / L and a pH of 7.00, oscillated at 25℃ and 200 r·min -1 for 2 h and then at 5000 r·min -1Centrifuge for 10 min, and the filtrate is the F1 exchangeable state; Add 10 mL of ammonium acetate solution with a concentration of 1 mol / L and a pH of 5.00 to the F1 residue, and at 25 °C and 200 r·min -1 Oscillate for 5 h, and then centrifuge at 5000 r·min -1 Centrifuge for 10 min, and the filtrate is the F2 carbonate-bound state. After filtering the above filtrate through a 0.45 μm filter membrane, it is measured by ICP-OES.

[0050] The soil dissolved carbon components are characterized by three-dimensional fluorescence. Weigh 2.00 g of soil sample passing through 0.25 mm and place it in a centrifuge tube. Add 40 mL of deionized water according to the soil-water ratio of 1:20, and at 25 °C and 200 r·min -1 Oscillate for 1 h, and then centrifuge at 5000 r·min -1 After centrifuging for 10 min, filter through a 0.45 μm filter membrane, and the filtrate is measured by a fluorescence spectrometer. The excitation slit and emission wavelength range of the spectrometer are 200 - 650 nm and 250 - 650 nm respectively. The excitation slit and emission slit are set to 5 nm and 1 nm respectively, and the scanning speed is 3000 nm·min -1 ;

[0051] Passivation and remediation effect

[0052] (1) Passivation effect of pineapple peel organic fertilizer on heavy metal Pb

[0053] After adding the organic fertilizer of the present invention to the soil polluted by heavy metal Pb, with the passage of time, the content of the active state Pb component decreases, and the passivation effect of heavy metal Pb is significant ( Figure 2 ). After the 4th day of passivation, there are significant differences among the treatment groups, and the passivation efficiency of heavy metal Pb is T2>T1>CK, indicating that the higher the application ratio of pineapple peel organic fertilizer, the better the passivation effect on heavy metals. After 60 days of passivation, the mobile indexes of T1 and T2 decreased by 23.66% and 44.96% respectively. It can be seen that applying the pineapple peel organic fertilizer prepared in the present invention can promote the reduction of the bioavailability and mobility of soil Pb, weaken the reduction of the environmental risk of heavy metal Pb, and the higher the application ratio of pineapple peel organic fertilizer, the better the passivation effect on heavy metals. Therefore, the organic fertilizer disclosed in the present invention has a strong heavy metal passivation effect and is a new material for the remediation of heavy metal polluted soil;

[0054] (2) Changes in soil pH value and organic matter after adding pineapple peel organic fertilizer

[0055] Adding the pineapple peel organic fertilizer of the present invention can improve the acidic state of the soil and increase the soil organic matter content ( Figure 3) The original polluted soil had a pH value of 5.5, being a weakly acidic soil. After adding 1.5% of the pomace organic fertilizer, the soil pH value became 6.5, an increase of about 1 unit. After adding 0.75% (T1) and 1.5% (T2), the soil organic matter content increased by 35.5% - 68.9%. These results indicate that the organic fertilizer disclosed in the present invention has the effects of alleviating soil acidic conditions and increasing soil organic matter content;

[0056] (3) Changes in soil carbon components after adding pomace organic fertilizer

[0057] Soil organic carbon is of great significance for maintaining soil fertility and the CO2 balance. After adding the pomace organic fertilizer disclosed in the present invention to the soil for 60 days, the fluorescence peak height in Region V of the three-dimensional fluorescence spectra of the soil solutions of T1 (addition amount 0.75%) and T2 (addition amount 1.5%) was still higher than that of the CK (no addition) soil, indicating that applying pineapple pomace organic fertilizer increased the content of humus-like substances in the soil; however, there was a fluorescence peak in Region IV of the three-dimensional fluorescence spectra of the original soil (CK), but the fluorescence peak intensity weakened after applying pineapple pomace organic fertilizer, indicating that there were a small amount of microbial residues and microbial metabolites in the soil, and these unstable carbon components were transformed into more stable humus-like substances through microbial transformation after applying pineapple pomace organic fertilizer. It can be seen that adding the organic fertilizer disclosed in the present invention to the soil can promote carbon storage and increase the soil carbon sink capacity;

[0058] (4) Nitrogen, phosphorus, and potassium nutrient conditions in the soil after adding pomace organic fertilizer

[0059] Applying the fruit peel residue compost of the present invention to the soil can also significantly increase the nitrogen, phosphorus, and potassium contents (Table 3). Especially after adding 1.5% of the pomace organic fertilizer to the soil, the available phosphorus in the soil increased by 54.3%, the total potassium in the soil increased by 25.2%, and the available potassium content increased by about 1 time. Compared with ordinary commercial organic fertilizers, the organic fertilizer disclosed in the present invention can significantly increase the potassium content in the soil, is a natural potassium-rich fertilizer, and is especially suitable for being applied to soils of potassium-loving plants to improve potassium nutrient;

[0060] Table 3 shows the changes in soil nutrients after adding organic fertilizer

[0061]

[0062] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing organic fertilizer from fruit peel residue, characterized in that: The following steps are involved: Step 1: Obtain compost raw materials: a mixture of pineapple peel residue, rice bran and cow dung in a mass ratio of 10:4:1; Step 2: Stir and mix thoroughly, and water the pile to control the moisture content to about 40%-50%; Step 3: Pile the mixed materials into strips with a height of 70-80cm and a width of 1.5-2m, and cover them with a layer of film to help maintain temperature and promote fermentation; Step 4: The fermentation cycle is 15-20 days. During the composting process, the compost pile needs to be turned regularly to promote the decomposition and fermentation of the waste; Step 5: During the composting process of pineapple peel residue, the 0th to 5th day is the warming stage, the 5th to 12th day is the thermophilic stage, and cooling begins after the 12th day. The temperature of the pile gradually approaches room temperature, which means that the peel residue compost is fully decomposed.

2. The preparation method of the pericarp residue organic fertilizer according to claim 1, characterized in that, In the step 1, a fermentation agent is added, wherein the fermentation agent includes a mixed fermentation agent of Bacillus subtilis, Trichoderma, and photosynthetic bacteria, and the fermentation agent is added at a ratio of 500:1 of the mass ratio of the raw material to the strain.

3. The preparation method of the pericarp residue organic fertilizer according to claim 1, characterized in that, The nitrogen-carbon ratio in the composting raw materials in step 1 is 1:(26-35).

4. The preparation method of the pericarp residue organic fertilizer according to claim 1, characterized in that, In step 3, sufficient pores should be left on the edge of the film to facilitate aerobic fermentation of microorganisms.

5. The preparation method of the pericarp residue organic fertilizer according to claim 1, characterized in that, In step 4, when the temperature rises to 50°C / the temperature in winter reaches above 55°C, the first turning of the pile begins. Thereafter, the pile is turned every time the temperature rises to around 60-70°C and maintained for 1-2 days.

6. The preparation method of the pericarp residue organic fertilizer according to claim 1, characterized in that, During the composting process, the temperature of the compost pile needs to be controlled. The temperature inside the pile should be maintained at 50-70℃. If the temperature is too high, the compost pile can be turned over or ventilation can be increased to lower the temperature. If the temperature is too low, cover it with insulation materials to raise the temperature.

7. A pericarp residue organic fertilizer, characterized in that, The organic fertilizer is prepared by using the peel residue organic fertilizer described in any one of claims 1 to 6.

8. Use of the fruit peel residue organic fertilizer according to claim 7 in the remediation of heavy metal contaminated soil.

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