CN106588459B

CN106588459B - Preparation method of chicken feather crosslinked cellulose multifunctional zinc fertilizer

Info

Publication number: CN106588459B
Application number: CN201611103202.4A
Authority: CN
Inventors: 耿增超; 曹胜磊; 许强; 许晨阳; 孙润仓
Original assignee: Northwest A&F University
Current assignee: Northwest A&F University
Priority date: 2016-12-04
Filing date: 2016-12-04
Publication date: 2020-04-17
Anticipated expiration: 2036-12-04
Also published as: CN106588459A

Abstract

The invention discloses a preparation method of a chicken feather crosslinked cellulose multifunctional zinc fertilizer, which takes chicken feather and paper pulp as raw materials, takes a potassium hydroxide/water/urea system as a composite solvent, discusses the influence of the proportion of the composite solvent system and experimental conditions on the hydrolysis rate of the chicken feather and the dissolution rate of cellulose, and results show that each milliliter of the composite solvent reacts for 120min at 75 ℃ and can hydrolyze 0.1g of the chicken feather; precooling the chicken feather hydrolysate to-12 ℃, adding 0.06g of cellulose into each milliliter of the chicken feather hydrolysate to form a gelled mixture, and finally preparing the gel into the chicken feather crosslinked cellulose gel which contains 150.6mg/g of nitrogen, 136.7mg/g of potassium and 13.9mg/g of zinc and contains nutrient elements such as sulfur, polypeptide, amino acid and the like. The results of soil culture experiments and corn pot culture experiments show that the Cell-CF has high biological effectiveness and can be used as a long-acting zinc fertilizer.

Description

Preparation method of chicken feather crosslinked cellulose multifunctional zinc fertilizer

Technical Field

The invention belongs to the technical field of agriculture, and particularly relates to a preparation method of a chicken feather crosslinked cellulose multifunctional zinc fertilizer.

Background

Cellulose is the first major biomass resource in nature and is widely applied in various fields such as papermaking, textile, new materials and the like. As a natural protein resource, the protein content of the feather is 85-99%, the global feather yield per year can reach 85 hundred million tons, and in addition, a large amount of natural protein resources such as hair, hoofs and horns of animals and the like are not well utilized, so that serious resource waste and environmental pollution are caused. Because intermolecular and intramolecular hydrogen bonds are strong, the solubility of cellulose is poor, and in addition, a solvent and a reactant are difficult to enter a crystallization area of the cellulose, and the development and the utilization of the cellulose are limited due to low reaction accessibility. Feather keratin is a rigid protein, and the structure of the feather keratin has high stability, poor water solubility and poor biodegradability through intermolecular disulfide bonds, hydrogen bonds, salt bonds and other crosslinking actions. Therefore, the development of excellent cellulose and feather keratin dissolving agents is the premise and the basis for improving the development and utilization values of the two natural resources. The new cellulose composite solvent of an alkali/urea system developed by Zhang Li Na subject group in recent years has the advantages of low price, green and environmental protection. Many researches show that functional groups of small molecular substances such as polypeptide and amino acid generated after feather hydrolysis are exposed, so that the feather water-soluble chitosan/chitosan composite material has good hydrophilicity and metal ion complexing capability and the biological effectiveness is improved. After being applied to soil, inorganic trace element fertilizers such as iron, zinc and the like are easily affected by pH, soil minerals and environment and are quickly converted into invalid nutrients, and the effectiveness of the trace element fertilizers in the soil can be improved by chelating the trace element fertilizers with organic matters. In addition, hydrogel with excellent performance can be prepared by utilizing the interpenetration crosslinking among hydrophilic macromolecules, can absorb a large amount of water and has wide application prospect in the aspect of slow release of fertilizer. For example, the gel fertilizer prepared by the crosslinking action of carboxymethyl cellulose and metal ions can obviously improve the utilization rate of the fertilizer.

At present, a preparation method of the chicken feather crosslinked cellulose multifunctional zinc fertilizer with low cost and environmental friendliness is urgently needed in the prior art.

Disclosure of Invention

The invention aims to provide a preparation method of a chicken feather crosslinked cellulose multifunctional zinc fertilizer with low cost and environmental friendliness. Using potassium hydroxide/water/urea (KOH/H)₂O/CO(NH₂)₂) The feather is hydrolyzed by a compound solvent, then pulp cellulose is added, the pH value is adjusted to 6.5 by dilute sulfuric acid, zinc sulfate is added, a gel slow-release zinc fertilizer (Cell-CF) of polypeptide cross-linked cellulose is prepared, and the structure, the water absorption performance, the slow-release performance and the biological effectiveness of the zinc fertilizer are researched.

The specific technical scheme is as follows:

a preparation method of a chicken feather crosslinked cellulose multifunctional zinc fertilizer comprises the following steps:

step 1, passing the feathers through KOH/H₂O/CO(NH₂)₂Hydrolyzing the composite solvent, namely destroying hydrogen bonds for maintaining the space structure of keratin in the process, and breaking disulfide bonds and hydrolytic peptide bonds to change feather keratin into protein peptides and amino acids with small molecular weight and good water solubility, so as to obtain chicken feather hydrolysate;

step 2, adding cellulose into the chicken feather hydrolysate, wherein the cellulose swells due to absorption of the chicken feather hydrolysate in the process, meanwhile, hydrogen bonds of a crystalline region and an amorphous region of the cellulose are destroyed, the crystallinity is reduced, the reaction accessibility is improved, and the cellulose chain and the protein peptide chain are highly interpenetrated and folded in the process to form composite gel;

step 3, adjusting the pH value of the composite gel to be faintly acid 6.5 by using dilute sulfuric acid, neutralizing the alkalinity of the composite gel fertilizer by using the sulfuric acid, eliminating the swelling effect of alkali on cellulose, forming a large amount of hydrogen bonds between a protein peptide chain and a cellulose chain, tightly binding the protein peptide chain and the cellulose chain together, modifying the cellulose chain into a cellulose polypeptide composite chain with stronger hydrophilicity and metal ion complexing ability, and slightly crosslinking and folding the chain and the chain to form a three-dimensional network structure;

step 4, adding metal trace elements into the composite gel, complexing with metal ions by utilizing functional groups in the gel,

adding zinc sulfate heptahydrate into the gel, continuously stirring for 1h, pouring the gel fertilizer into a mould, and drying and molding in a drying oven at 60 ℃.

Preferably, the KOH concentration in step 1 is 1.5mol/L, CO (NH)₂)₂The content is 0.12g/mL, each milliliter of the composite solvent reacts for 120min at the temperature of 75 ℃, and 0.1g of chicken feather is hydrolyzed.

Preferably, the chicken feather hydrolysate is pre-cooled to-12 ℃ in the step 2, and 0.06g of cellulose is added into each milliliter of the chicken feather hydrolysate.

Preferably, the mold described in step 4 is provided with 1cm × 1cm × 1cm small squares.

Compared with the prior art, the invention has the beneficial effects that:

the invention successfully prepares the hydrogel matrix Cell-CF, the preparation process fully utilizes the chemical properties of potassium hydroxide and urea and can ensure that the gel is rich in nitrogen and potassium elements, and the preparation process of the Cell-CF is economical and environment-friendly. Research results show that the crystal structures of the Cell and CF raw materials are completely damaged through composite solvent treatment, no chemical cross-linking agent is needed, and the CF and the Cell are closely combined through intermolecular interpenetration folding and intermolecular hydrogen bonds. After the cellulose is combined with the polypeptide and the amino acid, the hydrophilic performance is improved, and the Cell-CF shows better water-absorbing swelling property. Cell-CF is a substrate rich in functional groups, can perform complex reaction with zinc ions, plays an important role in preparing the long-acting zinc fertilizer, can maintain the effectiveness of zinc in soil for a long time, and is the long-acting zinc fertilizer. The corn pot experiment shows that the biological effectiveness of the Cell-CF zinc fertilizer is higher. The chicken feather grafted cellulose-based hydrogel material synthesized by the experiment can be used as a long-acting zinc fertilizer and has great potential application value in the preparation of long-acting copper fertilizers, magnesium fertilizers, iron fertilizers, calcium fertilizers, cobalt, nickel and other trace fertilizers, and in addition, the gel fertilizer has great development space on the functions of preserving water and improving soil structures.

Drawings

FIG. 1 is the chicken feather hydrolysis conditions, wherein FIG. 1a is the KOH concentration, FIG. 1b is the reaction temperature (T), FIG. 1c is the hydrolysis time (T), FIG. 1d is the chicken feather to lye ratio (S/L);

FIG. 2 is a graph of the effect of urea on cellulose dissolution rate;

FIG. 3 shows the steps for synthesizing Cell-CF;

FIG. 4 is an infrared spectrum of a sample, wherein FIG. 4a is an infrared spectrum of CF and U-CF, FIG. 4b is an infrared spectrum of Cell and U-Cell, and FIG. 4c is an infrared spectrum of Cell-CF;

FIG. 5 is an XRD pattern of the sample, wherein FIG. 5a is an XRD pattern of CF and U-CF, FIG. 5b is an XRD pattern of Cell and U-Cell, and FIG. 5c is an XRD pattern of Cell-CF;

FIG. 6 is an XPS spectrum of Cell-CF, wherein FIG. 6a is an XPS broad spectrum of Cell-CF; FIGS. 6 b-6 d are Cell-CF C1s, N1s and Zn2p3/2, respectively, XPS high resolution maps;

FIGS. 7A, C and E are bright field images of U-CF, U-Cell and Cell-CF after water immersion; b, D and F are fluorescence images of U-CF, U-Cell and Cell-CF after being soaked in water;

FIG. 8(a-c) 0min, 5min, 10min after Cell-CF is submerged; (A-C) 0min, 5min and 10min after the U-Cell enters water;

FIG. 9 is the hydrostatic release profile of K and Zn in Cell-CF;

FIG. 10 is the nutrient content of experimental soil and corn plants, CKO in the graph being blank control; CK1 ZnSO₄,CO(NH₂)₂,K₂SO₄,(NH₄)₂HPO₄；CK2:Zn-EDTA,CO(NH₂)₂,K₂SO₄,(NH₄)₂HPO₄；Cell-CF:Cell-CF,(NH₄)₂HPO₄；-20％:-20％Cell-CF,(NH₄)₂HPO₄Wherein FIG. 10a is a soil layerNitrogen content, fig. 10b soil available potassium content, fig. 10c soil available zinc content, fig. 10d corn seedling zinc content.

Detailed Description

The technical solution of the present invention will be described in further detail with reference to specific embodiments.

1 experimental part

1.1 materials and reagents

Cellulose (Cell): comminuted hardwood pulp; chicken Feather (CF): collecting the poultry slaughter house, removing impurities, washing with tap water for several times, and air drying; potassium hydroxide, urea, sulfuric acid, zinc sulfate heptahydrate, potassium sulfate and diammonium phosphate are all commercially available analytical pure reagents.

1.2 preparation of Slow-Release Zinc Fertilizer

1.2.1 hydrolysis of Chicken feather

The influence of four factors, namely KOH concentration, reaction temperature (T), hydrolysis time (T) and chicken feather-to-alkali liquor ratio (S/L) on the yield (PDI) of the water-soluble protein of the chicken feather is explored by adopting a single factor variable control method. The method comprises the following steps of carrying out experiments at different levels according to the set four factors (1) - (4), adding 5mL of alkali liquor into a 50mL centrifuge tube each time, and carrying out magnetic stirring on the whole reaction process. Adjusting pH of the hydrolyzed mixture to neutral after hydrolysis of chicken feather, centrifuging at 3500rpm for ten minutes, separating precipitate, oven drying at 60 deg.C in oven to determine insoluble matter amount (m)₁). Protein solubility (PDI) was calculated according to equation one under different conditions. Each treatment level was averaged in triplicate.

PDI＝(m-m₁) X 100/m formula one

In the formula m₁: mass of precipitate fraction (mass of solid), m: quality of chicken feathers (mass of chicken feather).

(1) Effect of KOH concentration on PDI

Adding 0.5g of chicken feather, and reacting at 50 ℃ for 60 min. The influence of the concentrations of KOH of 0, 0.3, 0.6, 0.9, 1.2, 1.5 and 1.8mol/L on the solubility of chicken feather protein was investigated.

(2) Effect of reaction temperature (T) on PDI

Adding 0.5g of chicken feather, wherein the KOH concentration is 0.9mol/L, and the reaction time is 60 min. The influence of the reaction temperatures of 35, 55, 75, 95 and 115 ℃ on the solubility of the chicken feather protein is studied.

(3) Effect of reaction time (t) on PDI

0.5g of chicken feather is added, the KOH concentration is 0.9mol/L, and the reaction temperature is 75 ℃. The influence of the reaction time of 20, 60, 100, 120, 140 and 180min on the solubility of the chicken feather protein is researched.

(4) Effect of solid-to-liquid ratio (S/L) on PDI

The KOH concentration is 0.9mol/L, the reaction temperature is 75 ℃, and the reaction time is 60 min. The influence of the dosages of the chicken feathers of 0.1, 0.3, 0.5, 0.7, 0.9, 1.2 and 1.4g on the solubility of the chicken feather protein is researched.

1.2.2 dissolving cellulose

The effect of urea content of the complex solvent on cellulose solubility at-12 ℃ (complex solvent is more likely to break hydrogen bonds between cellulose molecules near freezing point) was further investigated under the conditions of optimum KOH concentration for hydrolysis of chicken feather (1.5moL/L) obtained in experiment 1.2.1. A composite solvent system containing 0, 2, 4, 6, 8, 10, 12 and 14g of urea per 100mL of KOH (1.5mol/L) solution is prepared. Taking 50mL of composite solvent in a 100mL centrifuge tube, precooling the composite solvent to-12 ℃ in a low-temperature constant-temperature stirring reaction bath (DHJF-4002), adding 1.45g of paper pulp cellulose, stirring the mixture for reaction for half an hour, centrifuging the mixture for 10 minutes at 3500rpm, washing the lower layer of insoluble substances with deionized water until the pH value of the lower layer of the insoluble substances is neutral, drying the insoluble substances in an oven at 60 ℃ to determine the mass of the insoluble substances, and calculating the solubility of the composite solution to the cellulose (the experiment is repeated three times to obtain an average value). The optimal compatibility of the composite solvent is determined, and the composite solvent with the optimal compatibility is used for hydrolyzing chicken feather (U-CF) and dissolving cellulose (U-Cell).

1.2.3 determination of the amount of cellulose required for the gelation of the cellulose composite solution

The sol-gel transition of the polymer solution was determined by the falling ball method, KOH/H per 50mL₂O/CO(NH₂)₂Precooling the composite solution to-12 ℃ in a low-temperature constant-temperature stirring reaction bath, and then gradually increasing pulp celluloseThe addition amount of the cellulose was used for preparing a gel fertilizer (Cell-CF), and a stainless steel ball with a radius (r) of 2mm was placed after the intermittent stirring reaction, and the sol of the cellulose was considered to have a gelation transition when the ball could be left to stand in the gel, and the addition amount of the cellulose was recorded. The synthetic path is shown in FIG. 3.

1.3X-ray diffraction analysis (XRD) and Infrared analysis (FTIR) of gel fertilizers

XRD and FTIR tests are carried out on the chicken feather raw material (CF), a dried sample of the composite solvent chicken feather hydrolysate (U-CF), the cellulose raw material (Cell), a dried sample of the composite solution of the cellulose (U-Cell) and the synthesized gel fertilizer (Cell-CF). XRD test method: the sample is ground into fine powder, placed on a sample holder, and tested after stabilizing the conditions. And (3) testing conditions are as follows: cu target Ka ray, Ni sheet filtering to eliminate CuKa radiation, lambda being 0.154nm, tube voltage 40kV, tube current 30mA, scanning speed 2 degree/min, and scanning range 5-40 degree. FTIR testing: the sample and KBr are tabletted together and then a Nicolet 750 type Fourier infrared spectrometer is used at 400-4000cm^-1The range is scanned and recorded.

1.4X-ray photoelectron spectroscopy (XPS) of gel Fertilizer (Cell-CF)

The synthesized gel fertilizer (Cell-CF) was analyzed by scanning with an ESCALAB 250Xi (Thermo Fisher, usa) type photoelectron spectrometer using a monochromatic Al Ka (hv-1486.6 eV). (XPS testing was done by the laboratory of the institute of Material, Qinghua university)

1.5 Observation of the binding state and swelling behavior of gel Fertilizer (Cell-CF) in Water with fluorescence microscope and stereomicroscope, respectively

A little powder of U-CF, U-Cell and Cell-CF is put on a glass slide respectively, and a drop of deionized water is dripped on each glass slide, so that the sample is kept in a droplet wrapping state for more than 8 hours all the time, and the water is supplemented in the period. The coverslip was then covered and bright field and fluorescence images of the sample were collected separately using a LEICADM2500 type fluorescence microscope. Approximately 0.5g each of the U-Cell and Cell-CF blocks was cut out, and placed in a petri dish containing 200mL of tap water in advance, and a state change image of the two samples in water was collected by a stereomicroscope.

1.6 measurement of still water nutrient dissolution curve of Zn and K and 24h dissolution rate of N in Cell-CF

The determination of the hydrostatic nutrient dissolution curves of Zn and K is designed on the basis of the reference HG/T3997-2008 as follows: weighing 0.5g of block Cell-CF, filling the block Cell-CF into a small bag made of a 100-mesh nylon gauze, sealing the small bag, then placing the small bag into a 250mL triangular flask with a plug, accurately adding 100mL deionized water, plugging and sealing the small bag, then placing the small bag into a constant-temperature water bath kettle preheated to 38 ℃, taking out the triangular flask every 2 hours, slightly turning the triangular flask upside down three times to ensure that the concentration of the solution in the flask is uniform, and transferring 1mL of the solution into a 50mL volumetric flask and fixing the volume. The zinc and potassium concentrations were measured using an atomic absorption spectrometer (Z-2000) and a flame photometer (FP6410), respectively. After 24 hours, the remaining liquid in the flask was dry-filtered, 50mL of the filtrate was taken up, and the filtrate was concentrated to 10mL by evaporation in an oven at 60 ℃ and then the total nitrogen elution amount was measured for 24 hours according to the specification in GB/T8572.

1.7Cell-CF Zinc Fertilizer evaluation experiment

The zinc fertilizer efficiency evaluation scheme comprises five treatments: blank Control (CKO), zinc sulfate heptahydrate fertilizer (CK1), EDTA chelated zinc fertilizer (CK2), chicken feather cross-linked cellulose gel fertilizer (Cell-CF), and 20% reduced Cell-CF treatment (-20%). The nutrient composition of Cell-CF is shown in Table 2. The treatments except the blank control and-20% treatment were equal nutrient fertilization. The specific fertilizing amount per kilogram of air-dried soil is as follows, CK 0: the soil basic fertility is listed in table 3; CK1: 0.3227g of urea, 0.20g of diammonium phosphate, 0.3046g of potassium sulfate and 0.0610g of zinc sulfate heptahydrate; CK 2: 0.3227g of urea, 0.20g of diammonium phosphate, 0.3046g of potassium sulfate and 53.1mL of EDTA chelated zinc fertilizer (the molar ratio of EDTA to zinc ions is 1:1 and is 0.01 moL/L); Cell-CF: 1.00g of gel fertilizer and 0.20g of diammonium phosphate; -20%: 0.80g of gel fertilizer and 0.16g of diammonium phosphate.

1.7.1 soil culture experiment

2.5Kg of soil and fertilizer are uniformly mixed according to the fertilization requirements of each experiment treatment, then are put into seedling raising pots (190 multiplied by 135 multiplied by 170mm), small holes are reserved at the bottoms, the seedlings are placed in the open sun, and 200mL of tap water is respectively irrigated twice a day in the morning and at night. The soil culture experiment starts from 7 months and 21 days, and is respectively carried out at the following 5 days, 15 days, 25 days,35. And taking about 50g of soil in each pot after 45 and 55 days, and measuring the effective zinc, the effective potassium and the total nitrogen of the soil after air drying. (available Zinc: DTPA leached atomic absorption flame photometer determination, available Potassium: Cold 2MHNO₃Leaching-flame photometry determination, total nitrogen: kjeldahl method).

1.7.2 corn pot experiment to explore the bioavailability of zinc fertilizer

The fertilizer application amount of the corn pot culture experiment and the soil culture experiment are consistent and synchronous, 2.5Kg of soil and fertilizer mixture is put into pots, four holes of corn are sown in each pot, and two corn seeds are sown in each hole. Placing the seedlings in the open air and setting seedlings for 7 days, and reserving four corn seedlings with consistent growth in each pot. 200mL of tap water is respectively irrigated twice in the morning and at the evening in each pot in the early stage, the transpiration effect is strong when the corn seedlings grow to the 5-leaf stage, and the irrigation amount is increased to 250mL each time. After 55 days of corn seedling growth, underground part and overground part are harvested respectively, and after deactivation of enzymes, drying, crushing and ashing treatment, the zinc content is measured.

2 results and analysis

2.1 Synthesis of gel fertilizers

2.1.1 determination of gel Fertilizer Synthesis conditions

The influence of four factors, namely KOH concentration, reaction temperature (T), hydrolysis time (T) and ratio of chicken feather to alkali liquor (S/L) on the yield (PDI) of water-soluble protein of the chicken feather is respectively explored by adopting a single factor control variable method without adding urea in the chicken feather hydrolysate in advance. As shown in FIG. 1a, the PDI value increased with the increase of the alkali concentration within the potassium hydroxide concentration of 1.5moL/L, and the PDI was stabilized at a high value with the potassium hydroxide concentration of 1.5 moL/L. The hydrolysis temperature is in the range of 35-75 ℃, the PDI value is in a straight line rising trend along with the rising of the temperature, and the PDI is stable after the reaction temperature is higher than 75 ℃ from the graph shown in figure 1 b. The hydrolysis time was 120min, and the PDI value gradually increased with the time, and it is understood from FIG. 1c that the PDI value reached a maximum value after 120 min. The material ratio PDI also has a larger influence, the PDI is gradually reduced along with the increase of the input amount of the chicken feather, but the gradient of the PDI reduction is smaller when the addition amount of the chicken feather in every 5mL of potassium hydroxide solution is lower than 0.5g, and on the premise of ensuring better decomposition of the chicken feather, 0.1g/mL is preferably selected for analyzing S/L (g/mL) by a graph 1d in order to ensure that the polypeptide and the amino acid in the chicken feather hydrolysate have higher concentrations.

1.5moL/L potassium hydroxide solution and urea are compatible to dissolve cellulose, the capacity of the composite solution for dissolving cellulose is gradually improved along with the increase of the addition amount of the urea, and the figure 2 shows that the capacity of the composite solution for dissolving cellulose tends to be stable when the addition amount of the urea is 12g/100 mL. Therefore, the proportion of the composite solution is that each 100mL of potassium hydroxide solution with the concentration of 1.5moL/L contains 12g of urea, and a falling ball method is further adopted to determine that cellulose with the concentration of 0.06g is added into each milliliter of the composite solvent to form cellulose gel. The PDI of the composite solvent for hydrolyzing the chicken feathers is close to 100 percent and is better than that of a KOH solution, and the finally determined components and experimental conditions of the composite solvent are listed in Table 1.

TABLE 1 preparation conditions for Cell-CF obtained by experimental optimization

S/L solid-to-liquid ratio

2.1.2 Synthesis of gel Fertilizer (Cell-CF)

As shown in figure 3, the preparation of the multifunctional zinc fertilizer by the chicken feather crosslinked cellulose is divided into four steps. First step passing feather through KOH/H2O/CO (NH)₂)₂The hydrolysis of the composite solvent breaks the hydrogen bond of the space structure of the keratin, and breaks the disulfide bond and the hydrolysis peptide bond, so that the feather keratin is changed into protein peptide and amino acid with small molecular weight and good water solubility. And secondly, adding cellulose into the chicken feather hydrolysate, wherein the cellulose swells due to absorption of the chicken feather hydrolysate in the process, hydrogen bonds of a crystalline region and an amorphous region of the cellulose are destroyed, the crystallinity is reduced, the reaction accessibility is improved, and the cellulose chain and the protein peptide chain are highly interpenetrated and folded in the process. Thirdly, the pH value of the composite gel is adjusted to be 6.5 with weak acidity by using dilute sulfuric acid, the swelling effect of alkali on cellulose disappears due to the neutralization of the alkalinity of the gel fertilizer by the sulfuric acid, a large number of hydrogen bonds are formed between a protein peptide chain and a cellulose chain, the protein peptide chain and the cellulose chain are tightly bound together, the cellulose chain is modified into a cellulose polypeptide composite chain with stronger hydrophilicity and metal ion complexing ability, and the chain are slightly cross-linkedAnd the three-dimensional net structure is formed by folding. Fourthly, adding metal trace elements into the gel, complexing with metal ions by utilizing functional groups in the gel, continuously stirring for 1h, pouring the gel fertilizer into a mould (small square grids with the size of 1cm multiplied by 1 cm) and drying and molding in a drying oven at the temperature of 60 ℃. The nutrient composition of the final synthetic fertilizer is shown in table 2.

The element utilization rate of the input materials in the preparation process of the chicken feather cross-linked cellulose multifunctional zinc fertilizer almost reaches 100 percent. Potassium hydroxide and urea in the composite solvent can respectively provide potassium and nitrogen nutrition for plants, and hydrolysate polypeptide and amino acid of the chicken feather can be absorbed and utilized by crops and has the function of stimulating the growth of the crops. The functional groups such as hydroxyl, carboxyl, amino, sulfinic acid group and the like contained in the gel can generate complex reaction with the trace elements, so that metal ions are absorbed in a gel system, the trace elements are protected, and the trace elements are not easy to be converted into invalid nutrients in the soil environment. The cellulose is modified by chicken feather hydrolysate to form a hydrophilic three-dimensional network structure, has the water absorption, swelling and water loss shrinkage performances, and can play an active role in improving the water holding capacity of soil and improving the soil structure. In addition, the gel is beneficial to the interpenetration growth of plant root systems in the gel after absorbing water and swelling in soil, and the plant root systems have water fertility and can directly absorb nutrition and moisture from the inside of the gel.

TABLE 2 chemical composition of Cell-CF

2.2FTIR and XRD analysis

FIG. 4a is an IR spectrum of CF and U-CF, as can be seen. 3297cm^-1Near the peak of hydroxyl characteristic absorption and the stretching vibration of secondary amide N-H, the stretching vibration of primary amide N-H is two peaks with medium intensity, and the peak is 3500cm^-1And 3400cm^-1The vicinity (corresponding to the antisymmetric stretching vibration of N-H) moves to a low frequency region due to the influence of hydrogen bonds, respectively. At 3080cm^-1The vicinity is a characteristic absorption peak of the polypeptide (-CO-NH) -, 1630-1690 cm^-1The wavelength range is C ═ O absorption of stretching vibration (called amide I band), 1512cm^-1Nearby absorption of secondary amide N-H bending vibration (amide II band), the amide C-N absorption band is called amide III band, and the C-N absorption band of secondary amide is at 1305-^-1The C-N absorption band of the primary amide is at 1420-1400cm in the wavelength range^-12929cm in the wavelength range^-1The absorption is due to the C-H stretching vibration of the methyl and methylene groups. CF exhibits polypeptide character, is rich in amide bonds (secondary amines), and belongs to keratin. The characteristic absorption peak of the secondary amine of U-CF is reduced while the absorption peak of the primary amine is enhanced, on the one hand because the hydrolysis of the peptide bond generates a primary amide; on the other hand may be similar to LiOH/H₂O/CO(NH₂)₂The mechanism of action of the system with cellulose, potassium hydroxide/water/urea (KOH/H)₂O/CO(NH₂)₂Polypeptide generated by feather hydrolysis of the system can form hydrogen bonds with urea, the urea is coated on the periphery of polypeptide particles, and C-H stretching vibration absorption peaks of methyl and methylene of U-CF reflected in an infrared spectrum are weaker, and meanwhile, very strong primary amide characteristic absorption peaks are shown.

FIG. 4b is an IR spectrum of Cell and U-Cell, as can be seen. 3345cm^-1The absorption peak is a characteristic absorption peak of hydroxyl groups shared by cellulose, 2929cm^-1The absorption of (B) is due to the C-H stretching vibration of methyl and methylene groups, 1640cm^-1The nearby absorption peak is the absorption peak of the moisture absorbed by the cellulose, 1355cm^-1In-plane bending vibration and CH having an absorption peak of O-H₂Rocking vibration of CH₂Has a shear vibration absorption peak at a wavelength of 1431cm^-1Is treated as a crystalline band of cellulose I, 1050cm^-1The C-O stretching vibration peak of the cellulose is one of the characteristic peaks of the cellulose, and is 1164cm^-1The absorption peak is the asymmetric stretching vibration of C-O-C, 896cm^-1Is annular C-O-C asymmetric out-of-plane stretching vibration or CH₂(CH₂OH) non-planar rocking vibrations produce characteristic peaks associated with amorphous regions of cellulose. Compared with Cell, the infrared characteristic peak position and peak intensity of U-Cell are obviously changed, the absorption peak of cellulose crystal area disappears, and the characteristic absorption peak of cellulose is reducedThe absorption peak of urea is weak and the absorption peak of urea is strong (the characteristic absorption peak of the primary amide dominates). In a potassium hydroxide/urea solvent system, alkali destroys hydrogen bonds among cellulose molecules and swells the cellulose, and urea destroys hydrogen bonds in the molecules and is coated outside the cellosilk to play a role of a stabilizer.

The IR spectrum of Cell-CF is shown in FIG. 4 c. The infrared spectrum of the product is greatly changed compared with that of U-CF and U-Cell, and the wavelength is 3500cm^-1And 3400cm^-1The two medium intensity peaks of antisymmetric stretching vibration of the nearby primary amide N-H disappeared, 2929cm^-1The C-H stretching vibration with stronger methyl and methylene and the characteristic peaks of cellulose and protein peptide in the fingerprint area are shown. It is shown that the Cell-CF surface is no longer mainly made of urea, and probably the combination of urea and polypeptide is transferred to the interior of the fiber filament in the swelling process of cellulose. 1620cm^-1An absorption peak of C ═ O stretching vibration (referred to as an amide I band) in the vicinity of the wavelength; 1355cm^-1In-plane bending vibration having absorption peak at wavelength of O-H and CH₂1050cm of rocking vibration^-1The C-O stretching vibration peak is a characteristic peak of cellulose, 896cm^-1Is annular C-O-C asymmetric out-of-plane stretching vibration or CH₂(CH₂OH) characteristic peak generated by non-planar rocking vibration^.The Cell-CF surface is mainly characterized by the characteristic absorption peak of cellulose and simultaneously has an amide characteristic peak, which shows that the polypeptide is combined with the cellulose in an interpenetration mode, most of the polypeptide enters the cellulose and is partially exposed outside the cellosilk.

The crystallinity of CF and U-CF was analyzed by XRD, as shown in FIG. 5a, the weak diffraction peak of CF at about 10 ° 2 θ was diffraction of keratin α -helix structure, at about 20 ° 2 θ was diffraction of keratin β -fold structure, and at about 30 ° 2 θ was the overlap of keratin β -fold structure and β -turn structure, the diffraction peaks of U-CF, keratin α -helix structure, keratin β -fold and β -turn structure disappeared, indicating that the crystal structure of hydrolyzed CF passing through the complex solution was completely destroyed, the U-CF appeared many narrow diffraction peaks in the range of 20 ° to 27.5 ° 2 θ, and the XRD spectra of U-Cell (FIG. 5b) and Cell-CF (FIG. 5c) were compared, and the peak positions of their diffraction peaks were found to be consistent, indicating that the diffraction peak of 2 θ at 20 ° to 27.5 ° 2 θ was the diffraction peak of the complex solvent and inorganic salt after neutralization of pH.

The XRD patterns of Cell and U-Cell are shown in FIG. 5 b. The undissolved hardwood pulp cellulose (Cell) is a cellulose I-type crystal structure, the 101 and 002 crystal faces of the hardwood pulp cellulose respectively correspond to diffraction peaks of 15 degrees and 22.8 degrees, and the diffraction peaks of a crystal area disappear after the hardwood pulp cellulose is treated by the composite solvent, which shows that the composite solvent can completely damage the crystal structure of the Cell.

The XRD spectrum of Cell-CF is shown in FIG. 5 c. Except the diffraction peak of inorganic salt, no other diffraction peak exists, which indicates that the polypeptide obtained by chicken feather hydrolysis and the combination product of amino acid and cellulose are in a disordered structure, because the hydrolysis products of chicken feather are different in size and irregular in alternate folding among molecules.

2.3XPS analysis

XPS analysis of Cell-CF is carried out, as shown in FIG. 6, an XPS element full scan map (6a) shows that the surface of the Cell-CF contains a large amount of C, N, O, S and Zn elements and also contains a plurality of other elements because chicken feather and pulp cellulose are natural organic materials and are various in element composition, but the weak photoelectron intensity of K2p shows that the surface potassium element content of the Cell-CF is less and hydrated potassium hydroxide is probably transferred to the interior of the gel fertilizer in the swelling process of the cellulose. High-resolution photoelectron spectroscopy analysis is carried out on C1s (281-291eV), N1s (395-405eV) and Znp3/2(1019-1025eV) by Gaussian analysis, the possible combination forms of chemical bonds are explored, and the electronic combination energy distinction among different chemical bonds is mainly referred to the XPS analysis manual. C1s shown in FIG. 6b mainly has 4 peaks with different properties, which are respectively located at 284.61eV, 286.2eV, 287.9eV and 288.7eV, and respectively represent C-C, carbon of cellulose, carboxyl carbon of amino acid (carboxyl terminal of polypeptide) and carbon in urea state, and characteristic peaks of four different carbon bonds, and reveal that the main organic components on the surface of Cell-CF are cellulose, amino acid and part of urea. N1s in fig. 6c has mainly 2 peaks of different nature, located at 399.5eV and 400.6eV respectively, representing urea nitrogen and amino acid nitrogen respectively. FIG. 6d shows that Zn2p3/2 has 3 main peaks with different properties, which are respectively located at 1021.8eV, 1022eV and 1023.1eV, and respectively represent Zn-O, Zn-S and ZnSO₄The state of zinc indicates that the added zinc ion is partially bonded to the functional group in Cell-CF, and some zinc ions are present in a free state.

2.4 binding State and swelling Properties of gel Fertilizer (Cell-CF) in Water

As can be seen from FIG. 7A, the U-CF aqueous solution contains many small particulate matters, which are residues of chicken feather hydrolyzed by the composite solution, because the feather handle and the feather shaft of the chicken feather are hard and hard to be decomposed, but the particle size of the residues is below 20 μm, which has little influence on the material migration and combination of the chicken feather hydrolyzed solution to the inside of cellulose; FIG. 7B shows that the aqueous solution of U-CF exhibits strong and uniform fluorescence, indicating that most of the chicken feather hydrolysate contains polypeptides and small amino acids with good water solubility. U-Cell presents a three-dimensional network structure interpenetrating with each other in water as shown in FIG. 7C; U-Cell fluorescence image is shown in FIG. 7D, and the entire field of view is black, since cellulose is a non-fluorescent material. As shown in FIG. 7E, the Cell-CF exists in a three-dimensional network structure in water, during the gelation process, the cellulose swells and absorbs all the chicken feather hydrolysate, the water-soluble substances permeate into the inside of the cellosilk, and the larger chicken feather keratin particle part penetrates into the inside of the cellosilk or is attached to the surface of the cellosilk. The Cell-CF fluorescence image shows strong fluorescence by taking the contour of the fiber as a frame, and the fluorescence of the Cell-CF fiber cage after being soaked in the aqueous solution for 8 hours is not weakened, so that the combination strength of the polypeptide and the amino acid with the cellulose is high, and a good combination can be formed.

As shown in FIG. 8, Cell-CF shows very strong water-absorbing swelling property after entering water, and rapidly expands 4-5 times its original volume within 10 min. And U-Cell showed no significant swelling after entering water. The polypeptide and the amino acid contain a large amount of hydrophilic functional groups, the combination of the polypeptide and the amino acid with the cellulose can obviously improve the water absorption performance of the cellulose, and the Cell-CF can hold a large amount of water due to the mutually-interpenetrated reticular structure among the cellosilks.

2.5 determination of still Water nutrient dissolution Rate of Cell-CF

As shown in FIG. 9, the release curves of Zn and K in Cell-CF are logarithmic in the hydrostatic release curve within 24h, the release rate is high in the first four hours, and then the release is slow and reaches a steady state after about 12 h. The 24-hour leaching rate of Zn is 50.2%, and the 24-hour leaching rate of k is 55.5%. The Cell-CF has outstanding water absorption and swelling performance, nutrients in the gel are dissolved and form osmotic pressure after water absorption, and pores among the fiber filaments are rapidly increased after swelling, so that the nutrients of zinc, potassium and urea which are not combined in the Cell-CF are rapidly released. The diffusion rate decreases with decreasing concentration gradient of nutrients in the gel and solution. In addition, functional groups in the gel fertilizer have strong complexing ability and charge attraction, and metal cation nutrients can be bound in the gel fertilizer to form slow-acting nutrients. The nutrient can be changed to be effective by the alternate growth of the plant root system and the degradation of the gel fertilizer. The release rate and dissolution rate of K are higher than those of Zn because Zn can complex with functional groups inside the gel with stronger binding force.

The measured dissolution rate of nitrogen for 24 hours was 93.8. + -. 4.2%, and it is considered that all urea nitrogen was dissolved in 24 hours in Cell-CF, and the remaining nitrogen that was not dissolved was nitrogen contained in the polypeptide and amino acid bound to cellulose. The nitrogen in Cell-CF is mainly urea, and the urea has good water solubility and is neutral molecules, so the urea has high diffusion rate and high dissolution rate in the swollen gel fertilizer.

2.6 evaluation of Fertilizer Effect of Cell-CF

After the traditional fertilizer is applied to soil, the fertilizer is easily converted into invalid nutrients due to the self properties of the fertilizer and the influence of the soil environment, and the utilization rate of the fertilizer is low. The dynamic change of available nutrients of zinc and potassium in different treated soils is researched by adopting a soil culture experiment, and the change of the total nitrogen content of the soil is measured. The basic fertility of the soil used in the experiment is given in table 3.

TABLE 3 physicochemical properties of the experimental soils

OM is organic matter; n is total nitrogen of soil; p is soil total phosphorus; k is soil available potassium; zn effective zinc in soil

As shown in FIG. 10a, the total nitrogen content of the soil treated by the same species was not changed much within 55 days of soil cultivation.Overall the total nitrogen content of CK1, CK2, Cell-CF and-20% was significantly higher than CK0, while the differences between CK1, CK2, Cell-CF and-20% were not significant. FIG. 10b shows that the effective potassium content of the soil gradually decreases with the increase of the cultivation time in the same treatment. The effective potassium content of CK1, CK2, Cell-CF and-20% among different treatments is significantly higher than that of CK 0. In addition, the effective potassium content of CK1, CK2 and Cell-CF is higher than that of CK0 in general. The effective potassium content differences among CK1, CK2 and Cell-CF are not significant. In conclusion, short-term soil culture experiments showed that Cell-CF acts as a nitrogenous and potash fertilizer in combination with CO (NH)₂)₂And K₂SO₄The comparison does not show advantages. The effective zinc content of CK1, CK2, Cell-CF and-20% in 55d cultivated in soil as shown in FIG. 10c are all significantly higher than CK 0; the content of CK2, Cell-CF and-20% of effective zinc in the first 35 days is obviously higher than that of CK1, which indicates that the inorganic zinc fertilizer becomes ineffective in a short time after being applied to soil; the effective zinc content of CK2 was higher than other treatments within the first 15 days but was not significantly different from Cell-CF; the effective zinc content of CK2 is higher in the first 15 days of a soil culture test, and then rapidly decreases, and the effective zinc content of CK2 is no longer higher than that of CK1 even after the soil is cultured for 35 days, so that the EDTA chelated zinc fertilizer can only keep higher fertilizer efficiency in the initial stage of soil application and is a quick-acting zinc fertilizer; the Cell-CF keeps higher effective zinc extraction amount in the whole period of a soil culture experiment, and the effective zinc content does not show a trend of reduction along with the prolonging of the culture time, which indicates that the zinc in the Cell-CF is a long-acting zinc fertilizer; the effective zinc content of the soil is obviously higher than that of ZnSO under the condition that the Cell-CF is applied for 20 percent less₄The effective zinc content of the soil (CK1) is always obviously higher than that of the soil (CK2) which is applied with EDTA chelated zinc fertilizer after 15 days of culture experiment.

FIG. 10d reflects the zinc content in the plants of the different treated potted maize plants. The zinc content of the root system and the overground part CK1, CK2, Cell-CF and-20% is obviously higher than that of CK0, and in addition, CK2, Cell-CF and-20% are obviously higher than that of CK 1; the zinc content CK2, Cell-CF and-20% in the root system are all obviously higher than CK 1; the differences among CK2, Cell-CF and-20% are not obvious; the zinc content of the above ground CK2 was significantly higher than the other treatments. The above results show that the bioavailability of zinc in EDTA chelated state and Cell-CF is higher for the current season crops, but the EDTA chelated state zinc has more advantage in the migration in plants than the Cell-CF. The economy, the environmental friendliness and the long-term effect of the zinc fertilizer in the preparation process of the Cell-CF are comprehensively considered, so that the Cell-CF is the zinc fertilizer with excellent performance.

The above description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, and any simple changes or equivalent substitutions of technical solutions that can be obviously obtained by those skilled in the art within the technical scope of the present invention are within the scope of the present invention.

Claims

1. A preparation method of a chicken feather crosslinked cellulose multifunctional zinc fertilizer is characterized by comprising the following steps:

step 1, passing the feathers through KOH/H₂O/CO(NH₂)₂Alkaline hydrolysis of the composite solvent, namely, destroying hydrogen bonds for maintaining the space structure of keratin in the process, and breaking disulfide bonds and hydrolytic peptide bonds to change feather keratin into protein peptides and amino acids with small molecular weight and good water solubility, so as to obtain chicken feather hydrolysate;

and 4, adding metal trace elements into the composite gel, complexing with metal ions by utilizing functional groups in the gel, continuously stirring for 1h, pouring the gel fertilizer into a mould, and drying and molding in a drying oven at 60 ℃.

2. The method for preparing the chicken feather crosslinked cellulose multifunctional zinc fertilizer as claimed in claim 1, wherein the KOH concentration in the step 1 is 1.5mol/L, and CO (NH)₂)₂The content is 0.12g/mL, each milliliter of the composite solvent reacts for 120min at the temperature of 75 ℃, and 0.1g of chicken feather is hydrolyzed.

3. The method for preparing the chicken feather crosslinked cellulose multifunctional zinc fertilizer as claimed in claim 1, wherein the chicken feather hydrolysate is pre-cooled to-12 ℃ in step 2, and 0.06g of cellulose is added per ml of the chicken feather hydrolysate.