阅读说明：本技术 一种贝类酶解液中重金属的脱除方法 (Method for removing heavy metals in shellfish enzymolysis liquid ) 是由 聂鸿涛 姜坤银 李宁 黄金玉 闫喜武 于 2019-11-04 设计创作，主要内容包括：本发明公开了一种贝类酶解液中重金属的脱除方法,属于水产品加工技术领域,本发明首先制备原位掺铁的分子筛,然后制备改性壳聚糖,将原位掺铁的分子筛和改性壳聚糖交联形成分子筛/壳聚糖复合物,无需调节贝类酶解液的pH,直接将其加入贝类酶解液中,对多种金属离子均有良好的脱除率,分子筛/壳聚糖复合物易于回收,可重复利用。(The invention discloses a method for removing heavy metals in shellfish enzymolysis liquid, which belongs to the technical field of aquatic product processing.)

1. A method for removing heavy metals in shellfish enzymolysis liquid is characterized by comprising the following steps:

step 1: grinding coal gangue into powder, placing the powder in a cupel, adding sodium carbonate into the cupel, roasting for 1-2h at the temperature of 1000-1200 ℃, grinding to obtain a pretreated sample, oxidizing the pretreated sample for 1-1.2h at the temperature of 300-350 ℃, adding a hydrochloric acid solution, soaking for 1-1.5h at the temperature of 50-60 ℃, filtering, collecting filtrate and filter residue, adding oxalic acid into the filtrate, mixing uniformly to obtain a mixed solution, washing the filter residue, adding sodium hydroxide, grinding uniformly, treating for 1-1.2h at the temperature of 600-650 ℃ to obtain molten slag, adding deionized water, standing for 2-3h at the temperature of 50-60 ℃ to obtain a mixture, adding the mixed solution into the mixture, performing ultrasonic treatment for 3-5h to obtain an iron-doped molecular sieve, placing the iron-doped molecular sieve under the protection of nitrogen at the pressure of 0.1MPa and the flow of 60ml/min, treating for 2h at 700 ℃ in a tubular furnace, introducing hydrogen with the pressure of 0.1MPa and the flow rate of 40ml/min, treating for 3h, and introducing nitrogen with the pressure of 0.1MPa and the flow rate of 60ml/min to obtain the magnetic iron in-situ doped molecular sieve;

step 2: dissolving chitosan powder in methanol, adding benzaldehyde, stirring at room temperature for 15-17h, filtering, extracting with methanol in a Soxhlet extractor for 4h, washing with diethyl ether, drying to obtain a product I, preparing a mixed solution consisting of epichlorohydrin, hydrochloric acid, ethanol and water, stirring uniformly, adding the product I, stirring, carrying out a constant-temperature water bath at 90-100 ℃, carrying out a reflux reaction for 3-5h, filtering, washing the product with acetone, drying at 50 ℃ to obtain a product II, putting the product II, thiourea and anhydrous sodium carbonate into a three-neck flask to form a mixture, adding water into the three-neck flask, adding ClCH, adding thiourea and anhydrous sodium carbonate, stirring to obtain a mixture, and adding water into the mixture₂Refluxing COOH at 90 ℃ for 2-3h, filtering, washing with distilled water to be neutral to obtain a product III, soaking the product III in HCl with the mass fraction of 4% for 48h, and then soaking in 0.5mol/L NaOH for 5min to obtain thiourea acetic acid chitosan;

and step 3: uniformly mixing a magnetic iron in-situ doped molecular sieve and thiourea acetic acid chitosan, adding the mixture into 23.1-24.2 volume percent glutaraldehyde solution, reacting at 70-80 ℃ for 1-2h, washing the product to be neutral, drying in a drying oven at 50-60 ℃ for 12h, and crushing the dried product to obtain a molecular sieve/chitosan compound;

and 4, step 4: and (3) carrying out enzymolysis and enzyme deactivation on the shellfish homogenate, cooling to room temperature, centrifuging, carrying out ultrafiltration on the obtained supernatant, collecting filtrate to obtain shellfish enzymolysis liquid, adding the molecular sieve/chitosan compound into the shellfish enzymolysis liquid, carrying out ultrasonic oscillation for 1-2h, and separating the precipitate through an external magnetic field to obtain the shellfish enzymolysis liquid without heavy metals.

2. The method for removing heavy metals from shellfish enzymolysis liquid according to claim 1, wherein the mass ratio of the sodium carbonate to the coal gangue powder in step 1 is 1: (3-4).

3. The method for removing heavy metals in shellfish enzymolysis liquid as claimed in claim 1, wherein the oxalic acid and Fe in filtrate in step 1³⁺The molar ratio of (2-3): 1.

4. the method for removing heavy metals from shellfish enzymolysis liquid according to claim 1, wherein the mass ratio of the sodium hydroxide to the filter residue in step 1 is 1:1, and the molar ratio of the deionized water to the sodium hydroxide is 30: 1.

5. The method for removing heavy metals in shellfish enzymolysis liquid according to claim 1, characterized in that the feed-liquid ratio of chitosan powder to methanol in step 2 is 7g:350mL, and the volume ratio of benzaldehyde to methanol is 7: 100.

6. The method for removing heavy metals from shellfish enzymolysis liquid according to claim 1, wherein the volume ratio of the mixed solution of oxychloropropane, hydrochloric acid, ethanol and water in step 2 is oxychloropropane: hydrochloric acid: ethanol: water 100:2:125: 125.

7. The method for removing the heavy metals in the shellfish enzymolysis liquid as claimed in claim 1, wherein the feed-liquid ratio of the product I in the step 2 to the mixed solution of epichlorohydrin, hydrochloric acid, ethanol and water is 1g:4 mL.

8. The method for removing the heavy metals in the shellfish enzymolysis liquid as claimed in claim 1, wherein the mass ratio of the product II, thiourea and anhydrous sodium carbonate in the step 2 is 0.6:0.8: 1.

9. The method for removing heavy metals in shellfish enzymolysis liquid as claimed in claim 1, wherein the ClCH in step 2₂The feed-liquid ratio of COOH to distilled water was 1g:15 mL.

10. The method for removing the heavy metals in the shellfish enzymolysis liquid as claimed in claim 1, wherein the molecular sieve doped with the magnetic iron in situ and the thiourea chitosan acetate in step 3 are uniformly mixed according to the mass ratio of (2-3) to 1.

Technical Field

The invention relates to the technical field of aquatic product processing, in particular to a method for removing heavy metals in shellfish enzymolysis liquid.

Background

The marine shellfish enzymolysis liquid contains a large amount of bioactive micromolecules such as amino acids, polypeptides and the like, has unique physiological activity, has special effects in the aspects of immunoregulation, tumor inhibition, enzyme inhibition, antibiosis, antivirus, antioxidation, radioresistance and the like, and is widely applied to the industries of food, medical care, cosmetics and the like.

China is a world large country for shellfish culture, and the yield of the shellfish reaches 1000 million tons per year, which accounts for 60 percent of the total yield. The seawater shellfish culture yield accounts for 80% of the total seawater shellfish culture yield, and the shellfish marine products reaching the large-scale production level at present mainly comprise oysters, clams, scallops, razor clams, mussels and the like. With the economic development, the offshore environment is seriously damaged by the discharge of industrial wastewater and municipal sewage. The marine shellfish is easy to be exposed in polluted water due to poor activity, and has stronger enrichment capacity on heavy metals compared with other organisms due to the characteristic of filter feeding property, so that the marine shellfish is more easily polluted by the heavy metals to cause the heavy metals to exceed the standard. Shenzhen disease control center publishes a data, and the detection of 21 types of food in 2012 shows that the heavy metal content of shellfish food in aquatic products exceeds standard seriously, and the cadmium content exceeds standard in 69 samples of spot check. The shellfish aquatic products including belts, scallops, mussels, blood clam, fresh oysters, pangolins, sargassum, razor clams, abalones, clams and the like all have cadmium exceeding samples. The highest detection value of the cadmium content is 21.4mg/kg, which exceeds the national safety standard by 10 times. A large number of investigation results show that the shellfish heavy metal problem in China is particularly prominent, mainly manifested in that the cadmium and lead exceed the standard seriously, and the cadmium content of most shellfish exceeds the 'human body sanitary consumption standard'. The pollution directly influences the food safety of people and influences the deep processing and utilization of marine shellfish protein; meanwhile, the marine product outlet of China is also influenced, and the loss is caused to local economy. The effective control of heavy metal pollution in marine shellfish becomes a problem to be solved urgently.

At present, the method for removing the heavy metal from the marine shellfish comprises two directions of purifying the living shellfish and removing the heavy metal from the shellfish proteolytic solution. The living shellfish purification technology is characterized in that shellfish is transferred to clean water environment for temporary culture, and pollutants such as heavy metal in the body are discharged out of the body by utilizing the metabolic process of the shellfish until the safety standard is reached. The method has the advantages of long time consumption, high temporary culture loss rate and certain pollution to the water quality of the temporary culture area. The marine shellfish protein is enzymolyzed into micromolecular soluble components such as amino acid, polypeptide and the like by the protease, so that the resource utilization rate of the marine shellfish is effectively improved, the economic added value of the marine shellfish is improved, and the method is a necessary way for preparing marine products. The enzymolysis liquid obtained after enzymolysis is a liquid medium, which is more beneficial to the removal of heavy metals.

Common methods for removing heavy metals in the enzymatic hydrolysate include a chemical precipitation method and an ion exchange method. The chemical precipitation method is to add alkali into the liquid which needs to remove heavy metals to precipitate heavy metal ions, then remove the heavy metals after precipitation by a physical method, the method not only can change the pH value of the liquid, but also can introduce some other ions, if the method is used to remove chromium ions and cadmium ions in the liquid protein fertilizer, the aluminum ions and iron ions additionally introduced by the precipitator can cause the protein in the protein fertilizer to be denatured, and can also influence the growth of crops applied by the protein fertilizer; the ion exchange method is a method for separating ions by utilizing the exchange action of an ion exchanger and the ions in liquid, an ion exchange resin is an insoluble high molecular compound, and if chromium and cadmium ions in the protein enzymolysis liquid are removed by using the method, the ion exchange resin is difficult to remove after being added into the protein enzymolysis liquid, thereby influencing the application effect of the subsequent protease enzymolysis liquid.

The chitosan molecular chain contains a large amount of hydroxyl and amino, can be chelated with heavy metal cadmium ions through hydrogen bonds and ionic bonds, has rich sources, high adsorption efficiency, no toxicity and biodegradability, and is an ideal heavy metal cadmium ion remover applied to the marine shellfish enzymolysis liquid. At present, in the prior art (preliminary research on removing heavy metal cadmium in oyster homogenate by chitosan, food industry science and technology, liangpeng and the like), a method for removing heavy metal cadmium in oyster homogenate by using chitosan is disclosed, in the document, oyster meat is hydrolyzed by acid, and then the chitosan is adopted to desorb heavy metal cadmium ions in the oyster meat homogenate. The method has the following defects: (1) chitosan has poor stability and is easy to run off from a solution at low pH, so that the applicable pH range is narrow (the pH is 8); (2) the chitosan has lower adsorption capacity, long adsorption equilibrium time and removal time (6h), and low removal efficiency; (3) the chitosan is difficult to granulate, has small specific gravity, is difficult to separate from a water body, and is difficult to separate; (4) the combination of the chitosan and the heavy metal cadmium can only occur in the external structure of the chitosan, and the adsorption effect needs to be improved; (5) the adsorption of chitosan to heavy metals is only limited to cadmium, and the adsorption performance to other kinds of heavy metal ions is poor.

Disclosure of Invention

The invention aims to provide a method for removing heavy metals in shellfish enzymolysis liquid, which aims to solve the problems.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a method for removing heavy metals in shellfish enzymolysis liquid, which comprises the following steps:

step 1: grinding coal gangue into powder, placing the powder in a cupel, adding sodium carbonate into the cupel, roasting for 1-2h at the temperature of 1000-1200 ℃, grinding to obtain a pretreated sample, oxidizing the pretreated sample for 1-1.2h at the temperature of 300-350 ℃, adding a hydrochloric acid solution, soaking for 1-1.5h at the temperature of 50-60 ℃, filtering, collecting filtrate and filter residue, adding oxalic acid into the filtrate, mixing uniformly to obtain a mixed solution, washing the filter residue, adding sodium hydroxide, grinding uniformly, treating for 1-1.2h at the temperature of 600-650 ℃ to obtain molten slag, adding deionized water, standing for 2-3h at the temperature of 50-60 ℃ to obtain a mixture, adding the mixed solution into the mixture, performing ultrasonic treatment for 3-5h to obtain an iron-doped molecular sieve, placing the iron-doped molecular sieve under the protection of nitrogen at the pressure of 0.1MPa and the flow of 60ml/min, treating for 2h at 700 ℃ in a tubular furnace, introducing hydrogen with the pressure of 0.1MPa and the flow rate of 40ml/min, treating for 3h, and introducing nitrogen with the pressure of 0.1MPa and the flow rate of 60ml/min to obtain the magnetic iron in-situ doped molecular sieve;

step 2: dissolving chitosan powder in methanol, adding benzaldehyde, stirring at room temperature for 15-17h, filtering, extracting with methanol in a Soxhlet extractor for 4h, washing with diethyl ether, drying to obtain a product I, preparing a mixed solution consisting of epoxy chloropropane, hydrochloric acid, ethanol and water, stirring uniformly, adding the product I, stirring, carrying out a constant-temperature water bath at 90-100 ℃, carrying out a reflux reaction for 3-5h, filtering, washing the product with acetone, drying at 50 ℃ to obtain a product II, adding the product II, thiourea and anhydrous sodium carbonate into a three-neck flask to form a mixture, adding water into the three-neck flask, adding ClCH₂COOH, refluxing for 2-3h at 90 ℃, filtering, washing with distilled water to neutrality to obtain the productIII, soaking the product III in HCl with the mass fraction of 4% for 48 hours, and then soaking for 5 minutes by using 0.5mol/L NaOH to obtain thiourea acetic acid chitosan;

and step 3: uniformly mixing a magnetic iron in-situ doped molecular sieve and thiourea acetic acid chitosan, adding the mixture into 23.1-24.2 volume percent glutaraldehyde solution, reacting at 70-80 ℃ for 1-2h, washing the product to be neutral, drying in a drying oven at 50-60 ℃ for 12h, and crushing the dried product to obtain a molecular sieve/chitosan compound;

and 4, step 4: and (3) carrying out enzymolysis and enzyme deactivation on the shellfish homogenate, cooling to room temperature, centrifuging, carrying out ultrafiltration on the obtained supernatant, collecting filtrate to obtain shellfish enzymolysis liquid, adding the molecular sieve/chitosan compound into the shellfish enzymolysis liquid, carrying out ultrasonic oscillation for 1-2h, and separating the precipitate through an external magnetic field to obtain the shellfish enzymolysis liquid without heavy metals.

Preferably, the mass ratio of the sodium carbonate to the gangue powder in the step 1 is 1: (3-4).

Preferably, the oxalic acid and the Fe in the filtrate in the step 1³⁺The molar ratio of (2-3): 1.

preferably, in the step 1, the mass ratio of the sodium hydroxide to the filter residue is 1:1, and the molar ratio of the deionized water to the sodium hydroxide is 30: 1.

Preferably, the feed-liquid ratio of the chitosan powder to the methanol in the step 2 is 7g:350mL, and the volume ratio of the benzaldehyde to the methanol is 7: 100.

Preferably, the volume ratio of the mixed solution of the oxychloropropane, the hydrochloric acid, the ethanol and the water in the step 2 is that of the oxychloropropane: hydrochloric acid: ethanol: water 100:2:125: 125.

Preferably, the feed-liquid ratio of the product I in the step 2 to a mixed solution of epichlorohydrin, hydrochloric acid, ethanol and water is 1g:4 mL.

Preferably, the mass ratio of the product II, the thiourea and the anhydrous sodium carbonate in the step 2 is 0.6:0.8: 1.

Preferably, ClCH in step 2₂The feed-liquid ratio of COOH to distilled water was 1g:15 mL.

Preferably, the molecular sieve doped with the magnetic iron in situ in the step 3 and the thiourea chitosan acetate are uniformly mixed according to the mass ratio of (2-3) to 1.

Preferably, 0.2-1.0 g of molecular sieve/chitosan compound is added into every 100g of shellfish enzymolysis liquid.

The invention discloses the following technical effects:

the molecular sieve/chitosan compound is prepared by compounding the molecular sieve and chitosan, and the molecular sieve is internally doped with iron, and after the molecular sieve and the chitosan are compounded, the molecular sieve/chitosan compound can be recovered under the magnetic condition, and the recovery rate is more than 80%.

In the process of preparing the molecular sieve, oxalate is used for complexing iron ions, and the iron-doped molecular sieve is directly generated in situ with an aluminum-silicon source so as to prepare the magnetic molecular sieve, namely Fe₃O₄The Fe-doped framework molecular sieve enters crystal lattices of the molecular sieve to form the Fe-doped framework molecular sieve, the performance of the molecular sieve is further improved while the separation of a molecular sieve/chitosan compound is facilitated, crystal cavities and pore channels in the iron-doped molecular sieve crystal are communicated, the volume of an inner hole of the framework structure is 60-70% of the total volume, the pore size is uniform, the adsorption capacity is large, the problem that the adsorption effect needs to be improved due to the fact that the adsorption of heavy metals only occurs in an external structure in the process of using the chitosan alone is solved, and the removal rate of the heavy metals in the shellfish enzymolysis liquid is improved.

The modified chitosan is prepared, the surface of the modified chitosan contains a plurality of chelating groups such as carboxyl, thiourea and amino, when the amount of the molecular sieve/chitosan compound added into the shellfish enzymolysis liquid is small, the chitosan with a chain structure is contained, molecules can be freely bent to form a stable chelate with metal ions, and the chitosan shows strong adsorption capacity; when the addition amount is more, the modified chitosan is crosslinked into a net shape, the mesh effect and the action of the newly grafted functional group on metal ions are stronger, so that the selective adsorption performance of the chitosan on the heavy metal ions is widened, and the Cd can be adsorbed by the chitosan²⁺、Hg²⁺、Pb²⁺、Cr⁶⁺、Co²⁺、Ni²⁺The method has good removal effect on various heavy metal ions, and the removal efficiency is more than 99.9 percent. In-situ iron-doped molecular sieve and modified chitosan have small volume shrinkage in the cross-linking and drying processesThe obtained composite has good toughness and pore structure and large specific surface area.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

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. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The specification and examples are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.