CN117779210A - Salt dissolving degumming method for hemp/straw - Google Patents

Abstract

The invention relates to a salt dissolving degumming method for hemp/straw, which comprises the steps of sequentially carrying out puffing pre-acid, primary salt bath, acid-base callback and secondary salt bath on raw materials, and respectively separating and recovering primary pectin, primary hemicellulose, primary lignin and fibers, wherein the primary salt bath uses compound salts including disodium ethylenediamine tetraacetate, ammonium oxalate, sodium tripolyphosphate and sodium gluconate, and the secondary salt bath uses compound salts including sodium p-benzenesulfonate and sulfite; according to the invention, degumming treatment is carried out on hemp/straw by using different composite salts, so that colloid in raw materials can be rapidly and effectively dissolved, the obtained plant fiber has low residual colloid rate, the composite salts are relatively mild, the damage to fibers is small, and high-quality fibers can be obtained. In addition, the degumming and the fiber extraction are carried out by the method of the invention without damaging colloid, and pectin, hemicellulose and lignin are extracted at the same time, thus greatly improving the processing added value of hemp/straw.

Description

Salt dissolving degumming method for hemp/straw

Technical Field

The invention relates to the technical field of fiber extraction, in particular to a salt dissolving degumming method for hemp/straw.

Background

Hemp bast parts such as ramie, kenaf, jute, hemp, green hemp, flax, apocynum and the like, hemp leaves such as pineapple hemp, abaca, sisal and the like, and straws such as common rice, wheat and the like contain 50-70% of cellulose and 20-50% of colloid, and are important fiber raw materials. The pectin mainly comprises pectin, hemicellulose, lignin and the like, which are inlaid between cells and in cell walls, and non-cellulose extracted fibers can be removed through a degumming process.

Traditional hemp/straw degumming mainly comprises chemical degumming, biological degumming and other methods, and other amplification methods are not applied in large scale.

The chemical degumming method adopts a chemical degumming method taking caustic soda cooking as a center. Caustic soda scouring is to separate plant fiber under the action of strong acid and strong alkali at high temperature and high pressure, and generally comprises the procedures of pickling, alkali liquor scouring, beating hemp, acid washing, water washing, dehydration, bleaching, refining, oil feeding, drying and the like. The pickling is usually carried out by sulfuric acid with the concentration of 1-2g/L, the alkaline boiling is usually carried out by high-pressure secondary boiling, the consumption of caustic soda is 12-15g/L, and 300-500 tons of water is needed for processing 1 ton of raw hemp. Patent CN201711097990.5 discloses a chemical degumming method for jute and kenaf, and patent CN201210238029.4 discloses a chemical degumming method for ramie.

Biological degumming mainly comprises enzyme degumming and bacterial degumming. Biological degumming is to utilize enzyme secreted by microorganism to catalyze and degrade colloid to extract plant fiber, and generally comprises the procedures of pretreatment, strain culture, inoculation, raw material fermentation, inactivation, water washing, dehydration, refining, bleaching, oil feeding, drying and the like, wherein the strain culture time generally needs 6-8h, and the raw material fermentation degumming needs 8-12h. For example, patent CN201410812506.2 discloses an application of bacillus alcalophilus in biological degumming of ramie and a method for biological degumming of ramie, patent CN201710942751.9 discloses a strain capable of degumming by using hemp microorganism and a hemp degumming process thereof, and patent CN202010269923.2 discloses a compound enzyme degumming agent and a degumming method.

However, each 1 ton of raw hemp processed by chemical degumming needs to generate 300-500 tons of wastewater, and the COD of the wastewater reaches over 20000mg/L, so that the environment is seriously polluted, the processing cost of enterprises is greatly increased by the wastewater treatment cost, the processing process needs high temperature and high pressure, the energy consumption cost is increased, and unsafe factors are brought to production operation. In addition, the chemical degumming processing conditions are extremely high, and the fiber is damaged to a certain extent while the glass is non-cellulose, so that the quality of the fiber is reduced.

The cost of the microorganism culture process or the enzyme extraction process used for biological degumming is high, so that the industrial profit is low; the specificity of bacteria or enzymes is strong, the bacteria or enzymes are difficult to match with complex colloid components, the residual colloid rate is high, the degumming is incomplete, a plurality of enzymes are generally required to be compounded, the degumming process is complex, the requirements on technology and process conditions are high, equipment is specialized, the improvement investment of a production line is large, and the large-scale use is difficult in a short time.

Disclosure of Invention

In view of the defects of the prior art for degumming herbaceous plants such as hemp and straw, the invention aims to provide a salt dissolving degumming method for the hemp and straw, which dissolves colloid of the herbaceous plants by different compound salts for a plurality of times, can rapidly complete colloid degradation of the herbaceous plants, especially raw materials of the hemp and the straw, so as to obtain plant fibers, and simultaneously obtain functional components such as pectin, hemicellulose, lignin and the like in the raw materials, thereby greatly improving the processing added value while obtaining high-quality plant fibers.

Based on the above purpose, the technical scheme of the invention is as follows:

a salt dissolving degumming method for hemp/straw comprises the following steps:

s1, puffing pre-acid: dedusting and impurity-removing the herbaceous plants, cutting, puffing, and soaking in dilute hydrochloric acid solution;

s2, primary salt bath: adding the first compound salt into the solution in the step S1 according to the amount of 2-8g/L, and reacting at the temperature of 90-100 ℃; after the reaction is completed, carrying out solid-liquid separation to obtain a first filtrate and a first filter residue; collecting first filter residues, and precipitating the first filter liquor by ethanol to obtain primary pectin;

s3, acid-base callback: soaking the first filter residue in water, adding alkali, uniformly mixing, heating to 70-90 ℃ for reaction, and carrying out solid-liquid separation after the reaction is completed to obtain a second filtrate and a second filter residue; collecting second filter residues, regulating the pH value of the second filter liquor to 5.0-5.5, and then carrying out solid-liquid separation to obtain a first precipitate; adding ethanol into the filtrate, performing solid-liquid separation to obtain a second precipitate, and combining the first precipitate and the second precipitate to obtain primary hemicellulose;

s4, secondary salt bath: adding water into the second filter residue, adding a second compound salt according to the amount of 1-3g/L, heating to 90-100 ℃ for pressurized digestion, and carrying out solid-liquid separation to obtain a third filter residue and a third filtrate; collecting filter residues to obtain fibers, and further extracting the third filtrate to obtain primary lignin;

wherein the first compound salt comprises disodium ethylenediamine tetraacetate, ammonium oxalate, sodium tripolyphosphate and sodium gluconate; the second complex salt includes sodium p-benzenesulfonate and sulfite.

In some embodiments, the mass ratio of disodium edetate, ammonium oxalate, sodium tripolyphosphate, and sodium gluconate in the first complex salt is 1:1-2:1-2:1-2.

In some embodiments, the mass ratio of the sodium p-benzenesulfonate to the sulfite in the second complex salt is 1:1-2.

In some embodiments, the sulfite comprises at least one of sodium sulfite, calcium sulfite, magnesium sulfite, and ammonium sulfite.

In some embodiments, in step S3, the base is sodium hydroxide and/or potassium hydroxide; the concentration of the alkali is 5-8% after the alkali is added.

In some embodiments, in step S3, the first filter residue is soaked with tap water at a bath ratio of 1:10-30; in the step S4, the second filter residue is soaked in tap water according to the bath ratio of 1:10-30.

In some embodiments, in step S2, the temperature is raised to 90-100℃for reaction for 90-150min, and then filtered through a 60-100 mesh sieve, and solid-liquid separation is performed.

In some embodiments, in step S3, the temperature is raised to 70-90 ℃ for reaction for 1-3 hours, and then the mixture is filtered by a 60-100 mesh sieve for solid-liquid separation.

In some embodiments, in step S4, the reaction is carried out for 90-150min at a temperature of 90-100 ℃, and then the mixture is filtered by a 60-100 mesh sieve, and solid-liquid separation is carried out.

In some embodiments, in step S1, the specific treatment method of the puffing pre-acid is:

dedusting and removing impurities from herbaceous plants, cutting into 10-15cm long fragments, and puffing the raw materials for 1-2 times by a puffing machine; then the raw materials are soaked in dilute hydrochloric acid solution according to the bath ratio of 1:10-30, and the pH value is regulated to 4.0-5.0.

In some embodiments, the dilute hydrochloric acid solution has a concentration of 0.005 to 0.015mol/L.

In some embodiments, in step S1, the specific treatment method of the puffing pre-acid is:

the herbaceous plants are dedusted and decontaminated, cut into 10-15cm long fragments by a kneader or a pulverizer, and are subjected to puffing treatment for 1-2 times by a screw puffing machine, and then are soaked in 0.005-0.015mol/L dilute hydrochloric acid solution according to a bath ratio of 1:10-30, and the pH is regulated to 4.0-5.0.

In some embodiments, the hemp comprises ramie, kenaf, jute, hemp, kenaf, flax, kenaf, pineapple hemp, abaca, sisal, and the like; the straw comprises rice straw, wheat straw, corn straw, sorghum straw and the like.

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

according to the invention, degumming treatment is carried out on hemp/straw by using different composite salts, so that colloid in raw materials can be rapidly and effectively dissolved, the obtained plant fiber has low residual colloid rate, the composite salts are relatively mild, the damage to fibers is small, and high-quality fibers can be obtained. In addition, the degumming and the fiber extraction are carried out by the method of the invention without damaging colloid, and pectin, hemicellulose and lignin are extracted at the same time, thus greatly improving the processing added value of hemp/straw.

In addition, the method of the invention avoids the use of high-concentration strong acid and strong alkali, has milder reaction conditions and reduces the pollution of strong acid and strong alkali to the environment.

The degumming method provided by the invention has the advantages of low cost, high added value, simple process and less damage to the fiber, and is suitable for popularization and use; specifically, the advantages of the present invention are as follows:

(1) The cost is low: the degummed material mainly relates to 2 different compound salts, the raw materials of the compound salts are common, the price is low, the proportion is simple, the dosage of the compound salts is small, and the processing cost of ton raw materials is reduced by more than 50 percent compared with the traditional chemical degummed or biological degummed materials;

(2) High added value and reduced pollution: whether biological degumming or chemical degumming is carried out, pectin, hemicellulose, lignin and the like are destroyed and treated as waste for degrading colloid, but the invention achieves the purpose of degumming by separating and stripping each component in a grading way, can gradually collect pectin, hemicellulose and lignin, increases the added value, and prevents organic matters from entering wastewater from the source;

(3) The process is simple: the whole treatment process of the invention does not need special equipment, high temperature and high pressure, the main working procedure only needs 2 times of salt bath, and the process flow is simple;

(4) The fiber adhesive residue rate is low, and the fiber damage is small: according to the invention, pectin, hemicellulose and lignin can be effectively extracted through 2 salt baths and 1 acid-base callback, and fibers with higher purity are released, so that the whole process is not applicable to high temperature and high pressure and cellulase, and the obtained fibers are not damaged and have good quality.

Drawings

FIG. 1 is a process flow diagram of the present invention;

FIG. 2 shows pectin precipitated after a single salt bath extraction of examples 1 and 2;

FIG. 3 shows the fibers obtained after a single salt bath extraction of example 1 and example 2;

FIG. 4 shows the fibers obtained after the acid-base callback in example 1;

FIG. 5 is the fiber obtained after the secondary salt bath in example 1;

fig. 6 shows the fiber obtained after one salt bath with different salts or acids.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit or scope of the invention, which is therefore not limited to the specific embodiments disclosed below.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Example 1

As shown in fig. 1, the salt dissolving degumming method of the ramie raw ramie comprises the following steps:

s1, cutting raw ramie into sections with the length of about 10cm, puffing the raw materials for 1 time by a screw puffing machine, taking 5kg of raw materials, soaking the raw materials in 100L of 0.01mol/L dilute hydrochloric acid solution, and adjusting the pH value to 4.5;

s2, preparing disodium ethylenediamine tetraacetate: preparing a composite salt from ammonium oxalate, sodium tripolyphosphate and sodium gluconate in a mass ratio of 1:1:1, adding 500g of the composite salt into the solution in the step S1, uniformly mixing, heating to 90 ℃, preserving heat for 120min, filtering with a 80-mesh sieve to obtain a first filtrate and a first filter residue, collecting the first filter residue, adding equal volume of ethanol into the first filtrate for precipitation, and filtering with a 400-mesh sieve to obtain primary pectin;

s3, taking 1kg of first filter residue, soaking in 10L of tap water, adding 0.6kg of sodium hydroxide, stirring uniformly, heating to 80 ℃, preserving heat for 2 hours, and filtering by using a 80-mesh sieve after the reaction is completed to obtain second filter residue and second filtrate; regulating the pH value of the second filtrate to 5.0 by using dilute hydrochloric acid to obtain flocculent precipitate, centrifuging and drying the flocculent precipitate; adding 2 times of absolute ethyl alcohol into the supernatant after centrifugation, centrifuging, drying the precipitate, and combining the precipitate to obtain primary hemicellulose;

s4, soaking second filter residues in tap water according to a bath ratio of 1:10, and mixing with sodium p-benzenesulfonate: preparing a composite salt with the sodium sulfite ratio of 1:1, adding the composite salt according to the amount of 2g/L, heating to 100 ℃, preserving heat for 100min, heating in a pressure cooker, filtering by using a 80-mesh sieve after the reaction is finished, and further extracting primary lignin from the filtrate; the filter residue is the fiber.

The filter residues obtained in the steps S2, S3 and S4 are shown in the figures 3-5; the step S2 of alcohol precipitation of pectin is shown in figure 2.

Example 2

Example 2 differs from example 1 in that in step S2, the amount of the complex salt added is 400g (i.e., the complex salt is added to the solution in an amount of 4 g/L).

Step S2, alcohol precipitation of pectin is shown in figure 2; the filter residue obtained in step S2 is shown in fig. 3.

The fiber yields obtained after the primary and secondary salt bath treatments of examples 1 and 2 were examined and are shown in table 1 below.

Table 1 fiber yields (relative to initial raw materials) for examples 1 and 2

	Example 1	Example 2
			Disposable salt bath	78.6％	79.2％
Secondary salt bath	64.9％	67.5％

Comparative example

The first salt bath was performed using different acids or salts, respectively, instead of the complex salts of example 1, as follows:

a: treatment with 0.1mol/L citric acid;

b: treatment with 5g/L ammonium oxalate;

c:4g/L sodium polyphosphate treatment;

d:5g/L sodium polyphosphate treatment;

e:0.0001mol/L HCl treatment;

f: f, 0.001mol/L HCl treatment;

g: g.0.01mol/L HCl treatment;

h: treatment of the complex salt of example 1;

i:0.01mol/L HCl+5g/L sodium polyphosphate;

the acid-base callback is carried out on the material obtained after the first salt bath, and the performances of the obtained material are shown in fig. 6 and table 2:

TABLE 2 weight loss and pectin yields of materials after different salt bath treatments (relative to the initial raw materials)

	Weight loss rate	Pectin yield	Softness and softness	Whiteness degree	Residual glue rate
						A	12.36％	1.52％	3	4	/
B	22.47％	3.01％	4	4	5.38％
						C	16.12％	1.73％	2	3	/
D	17.35％	1.79％	3	3	/
						E	14.55％	1.49％	1	1	/
F	15.27％	1.55％	1	1	/
						G	15.78％	1.65％	2	1	/
H	27.42％	4.12％	4	5	3.12％
						I	18.75％	2.07％	2	2	/

As is apparent from table 2 and fig. 6, except that the fiber was dispersed by one-time salt bath using ammonium oxalate and the complex salt of the present application, the fiber was dispersed by other treatments, and the degumming effect was not achieved.

As shown in Table 2, the fiber product obtained after the ammonium oxalate bath has a residual gum rate of 5.38%, and the fiber product obtained after the composite salt treatment of the present application has a residual gum rate of 3.12%, which is significantly higher than the treatment result of ammonium oxalate and has reached the requirements of the degummed ramie standard (GB/T20793-2015).

In addition, the quality of the fiber extracted by the composite salt is obviously improved compared with that of other treatments, the softness of the composite salt bath fiber reaches 4 grades by taking 5 grades of softness as the highest standard, and in other treatments, the softness of the fiber treated by ammonium oxalate is close to 4 grades, and the other treatments are 1-3 grades; the whiteness of the 5-grade pure white is the highest standard, the whiteness of the composite salt bath fiber reaches 5-grade, and the other treatments are similar to 4-grade treatments such as ammonium oxalate, citric acid and the like, and the other treatments are only 1-3 grade.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims (10)

1. The salt dissolving degumming method for the hemp/straw is characterized by comprising the following steps of:

s1, puffing pre-acid: dedusting and impurity-removing the herbaceous plants, cutting, puffing, and soaking in dilute hydrochloric acid solution;

s2, primary salt bath: adding the first compound salt into the solution in the step S1 according to the amount of 2-8g/L, and reacting at the temperature of 90-100 ℃; after the reaction is completed, carrying out solid-liquid separation to obtain a first filtrate and a first filter residue; collecting first filter residues, and precipitating the first filter liquor by ethanol to obtain primary pectin;

s3, acid-base callback: soaking the first filter residue in water, adding alkali, uniformly mixing, heating to 70-90 ℃ for reaction, and carrying out solid-liquid separation after the reaction is completed to obtain a second filtrate and a second filter residue; collecting second filter residues, regulating the pH value of the second filter liquor to 5.0-5.5, and then carrying out solid-liquid separation to obtain a first precipitate; adding ethanol into the filtrate, performing solid-liquid separation to obtain a second precipitate, and combining the first precipitate and the second precipitate to obtain primary hemicellulose;

s4, secondary salt bath: adding water into the second filter residue, adding a second compound salt according to the amount of 1-3g/L, heating to 90-100 ℃ for pressurized digestion, and carrying out solid-liquid separation to obtain a third filter residue and a third filtrate; collecting filter residues to obtain fibers, and further extracting the third filtrate to obtain primary lignin;

wherein the first compound salt comprises disodium ethylenediamine tetraacetate, ammonium oxalate, sodium tripolyphosphate and sodium gluconate; the second complex salt includes sodium p-benzenesulfonate and sulfite.

2. The method for dissolving and degumming a hemp/straw salt according to claim 1, wherein the mass ratio of the disodium ethylenediamine tetraacetate, the ammonium oxalate, the sodium tripolyphosphate and the sodium gluconate in the first compound salt is 1:1-2:1-2:1-2.

3. The method for degumming a hemp/straw salt according to claim 1, wherein the mass ratio of the sodium p-benzenesulfonate to the sulfite in the second composite salt is 1:1-2.

4. The method for salt-dissolving degumming of hemp/straw according to claim 1, wherein in step S3, the alkali is sodium hydroxide and/or potassium hydroxide; the concentration of the alkali is 5-8% after the alkali is added.

5. The method for salt-dissolving degumming of hemp/straw according to claim 1, wherein in step S3, the first filter residue is soaked with tap water according to a bath ratio of 1:10-30; in the step S4, the second filter residue is soaked in tap water according to the bath ratio of 1:10-30.

6. The method for degumming a hemp/straw salt according to claim 1, wherein in the step S2, the temperature is raised to 90-100 ℃ and the reaction is maintained for 90-150min, and then the mixture is filtered by a 60-100 mesh sieve and subjected to solid-liquid separation.

7. The method for degumming a hemp/straw salt according to claim 1, wherein in the step S3, the temperature is raised to 70-90 ℃ for reaction for 1-3 hours, and then the mixture is filtered by a 60-100 mesh sieve for solid-liquid separation.

8. The method for degumming a hemp/straw salt according to claim 1, wherein in the step S4, the temperature is raised to 90-100 ℃ for reaction for 90-150min, and then the mixture is filtered by a 60-100 mesh sieve for solid-liquid separation.

9. The method for degumming a hemp/straw by salt dissolution according to claim 1, wherein in the step S1, the specific treatment method of puffing pre-acid is as follows:

dedusting and removing impurities from herbaceous plants, cutting into 10-15cm long fragments, and puffing the raw materials for 1-2 times by a puffing machine; then the raw materials are soaked in dilute hydrochloric acid solution according to the bath ratio of 1:10-30, and the pH value is regulated to 4.0-5.0.

10. The process for salt-dissolving degumming of hemp/straw according to claim 9, characterized in that the concentration of the dilute hydrochloric acid solution is between 0.005 and 0.015mol/L.