CN108486199B - Water-soluble chelating agent, preparation method thereof and heavy metal wastewater treatment method using water-soluble chelating agent - Google Patents
Water-soluble chelating agent, preparation method thereof and heavy metal wastewater treatment method using water-soluble chelating agent Download PDFInfo
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- CN108486199B CN108486199B CN201810261038.2A CN201810261038A CN108486199B CN 108486199 B CN108486199 B CN 108486199B CN 201810261038 A CN201810261038 A CN 201810261038A CN 108486199 B CN108486199 B CN 108486199B
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- C—CHEMISTRY; METALLURGY
- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
- C12P21/00—Preparation of peptides or proteins
- C12P21/06—Preparation of peptides or proteins produced by the hydrolysis of a peptide bond, e.g. hydrolysate products
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07K—PEPTIDES
- C07K1/00—General methods for the preparation of peptides, i.e. processes for the organic chemical preparation of peptides or proteins of any length
- C07K1/14—Extraction; Separation; Purification
- C07K1/34—Extraction; Separation; Purification by filtration, ultrafiltration or reverse osmosis
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/58—Treatment of water, waste water, or sewage by removing specified dissolved compounds
- C02F1/62—Heavy metal compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
Abstract
A water-soluble chelate, a preparation method thereof and a heavy metal wastewater treatment method adopting the water-soluble chelate. The heavy metal wastewater treatment method comprises the following steps: the subcritical protein extraction, the protease hydrolysis method and the ultrafiltration technology are combined to prepare a water-soluble chelating agent solution, the prepared solution and heavy metal in the wastewater are subjected to chelation reaction, the mixed solution after the reaction is concentrated and separated by an ultrafiltration membrane to generate a heavy metal chelate concentrated solution, the pH value of the obtained heavy metal chelate concentrated solution is adjusted, the heavy metal chelate concentrated solution is concentrated and separated by the ultrafiltration membrane, the heavy metal concentrated solution is subjected to extraction and electrolysis processes to obtain high-purity metal, and the water-soluble chelating agent solution is recycled. The raw materials are cheap and easy to obtain, and the prepared chelating agent has excellent performance and is biodegradable; the molecular weight of the prepared water-soluble chelating agent can be controlled according to the pore diameter characteristics of the ultrafiltration membrane, and the molecular weight is adjustable and uniform; the heavy metal in the heavy metal wastewater has high removal rate, is not influenced by impurity ions such as calcium, magnesium and the like, and the purity of the recycled valuable metal is high.
Description
Technical Field
The invention relates to the field of wastewater recycling treatment, in particular to a water-soluble chelate, a preparation method thereof and a heavy metal wastewater treatment method adopting the water-soluble chelate.
Background
Heavy metals generally exist in natural environment in natural concentration, but due to activities such as mining, smelting, processing and commercial manufacturing of heavy metals, such as non-ferrous metal mining, ore dressing, non-ferrous metal smelting, steel smelting, electroplating, tanning, chlor-alkali industry and the like, human activities generate a large amount of heavy metal wastewater to cause environmental pollution, heavy metals existing in various states and forms cannot be degraded by microorganisms after entering the environment, but enter a biological chain of an ecosystem to precipitate, enrich and migrate, so that the normal metabolic function of organisms is destroyed for a long time, serious harm is brought to human society and natural environment, how to economically and effectively remove heavy metals in wastewater, and the threat of industrial drainage to ecological environment is reduced, which becomes an urgent problem to be solved.
At present, the methods for removing heavy metals in wastewater mainly comprise a chemical precipitation method, an ion exchange method, an adsorption method and a membrane separation method. The membrane separation method for treating the heavy metal wastewater has the advantages of simple operation, no phase change, high heavy metal ion retention rate, valuable metal recovery and the like, however, the separation membrane for treating the heavy metal wastewater at present is a nanofiltration membrane and a reverse osmosis membrane, the membrane component is expensive, the operation pressure is high, the energy consumption is high, and the treatment cost is high; heavy metals in the wastewater are intercepted by the nanofiltration membrane and the reverse osmosis membrane together with impurities such as calcium ions and magnesium ions, membrane pollution caused by the calcium ions and the magnesium ions is easy to form, the content of the impurities such as the calcium ions and the magnesium ions in the heavy metal concentrated solution is high, and the subsequent recovery of valuable metals is influenced.
The ultrafiltration membrane technology has the advantages of high membrane flux, low operating pressure, low energy consumption, low treatment cost and investment conservation, impurity ions such as calcium, magnesium and the like are not intercepted, the recovery of valuable metals from concentrated solution is simple, the purity of the recovered valuable metals is high, and the advantage of the ultrafiltration membrane technology for treating heavy metal wastewater is obvious. The ultrafiltration technology generally needs to be coupled with other technologies to treat the heavy metal in the wastewater, for example, the water-soluble polymer complexing ultrafiltration coupling technology, a water-soluble chelating agent containing functional groups and heavy metal ions perform a chelation reaction, and when the molecular weight of the water-soluble chelating agent is larger than the cutting molecular weight of the ultrafiltration membrane, the heavy metal ions chelated with the water-soluble chelating agent are intercepted, so that the separation of the metal ions is realized. When the concentration of heavy metal ions in the ultrafiltration membrane concentrated solution reaches a certain level, adjusting the pH value of the ultrafiltration concentrated solution to separate the water-soluble chelating agent from the heavy metal in the ultrafiltration concentrated solution, treating the mixed solution with the ultrafiltration membrane, allowing the heavy metal to pass through the ultrafiltration membrane to generate a high-concentration heavy metal solution, and intercepting the water-soluble chelating agent for reuse.
The water-soluble polymers mainly comprise polyethyleneimine, sodium polyacrylate and the like, and the water-soluble polymers are high in price, difficult to realize large-scale use, poor in biodegradability and high in secondary pollution risk, so that the coupling of the water-soluble biodegradable chelate with low cost and excellent performance and the ultrafiltration technology has important significance in resource treatment of heavy metal-containing wastewater.
Disclosure of Invention
In view of the disadvantages of the prior art, the main object of the present invention is to provide a water-soluble chelate, a method for preparing the same, and a method for treating heavy metal wastewater using the same, so as to at least partially solve at least one of the above technical problems.
In order to achieve the above object, as one aspect of the present invention, there is provided a method for preparing a water-soluble chelating agent, comprising the steps of:
cleaning and crushing industrial raw materials, leftover materials or waste materials containing water-soluble biological protein, wherein the particle size of the crushed raw materials is less than or equal to 5 mm;
pumping the cleaned and crushed raw materials into a subcritical extraction device, and extracting water-soluble biological protein under certain reaction conditions to obtain a water-soluble biological protein solution;
concentrating the water-soluble biological protein in the water-soluble biological protein solution obtained in the step to 0.01-0.1 g/mL by using an ultrafiltration membrane;
adding a certain amount of neutral protease or alkaline protease into the water-soluble biological protein concentrated solution obtained in the step, stirring and dissolving, adding a sodium hydroxide solution, adjusting the pH value to 7-10, putting the solution into a constant-temperature oscillator, reacting for 1-4 hours at a certain temperature, wherein the oscillation speed of the constant-temperature oscillator is 10-60 r/min, then freezing to inactivate the enzyme, and performing centrifugal filtration to obtain a protein peptide solution;
concentrating the protein peptide in the protein peptide solution to 0.05-0.5 g/mL by using an ultrafiltration membrane, and taking ultrafiltration membrane retentate to obtain a protein peptide concentrated solution, namely the water-soluble chelating agent solution.
As another aspect of the present invention, there is also provided a water-soluble chelating agent solution prepared according to the preparation method as described above.
As a further aspect of the present invention, there is also provided a heavy metal wastewater treatment method, comprising the steps of:
step 1, adjusting the pH value of heavy metal wastewater to be treated, adding the water-soluble chelating agent solution into the heavy metal wastewater, and stirring for a period of time to obtain a heavy metal chelate solution formed by complexing the water-soluble chelating agent and heavy metal;
step 2, concentrating and separating the obtained heavy metal chelate solution by an ultrafiltration membrane to obtain ultrafiltration concentrated solution, and recycling or discharging permeate;
step 3, adjusting the pH value of the ultrafiltration concentrated solution to decomplex and separate the heavy metal chelate;
step 4, treating the solution subjected to decomplexation separation by using an ultrafiltration membrane, enriching a water-soluble chelating agent to form a concentrated solution for recycling, wherein a permeate is a heavy metal concentrated solution;
and 5, purifying and recycling the heavy metal concentrated solution.
Based on the technical scheme, compared with the prior art, the invention has the advantages that: the invention uses industrial raw materials, leftover materials or waste materials containing water-soluble biological protein as raw materials to prepare the water-soluble chelating agent, the raw materials are cheap and easy to obtain, and the prepared chelating agent has excellent performance and is biodegradable; the water-soluble chelating agent is prepared by subcritical extraction and alkaline protease hydrolysis, the molecular weight of the prepared water-soluble chelating agent can be controlled according to the pore diameter characteristics of the ultrafiltration membrane, and the membrane pollution is small; the prepared water-soluble chelating agent is coupled with an ultrafiltration technology and is used for the resource treatment of the wastewater containing the heavy metals, the removal rate of the heavy metals is high, the water-soluble chelating agent is not influenced by impurity ions such as calcium, magnesium and the like, and the purity of the recycled valuable metals is high.
Drawings
FIG. 1 is a schematic process flow diagram of the present invention.
Detailed Description
In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.
The water-soluble protein is a natural polymer consisting of a plurality of amino acids, has a large number of functional groups such as hydroxyl, carboxyl, amino, amido and the like, and can generate chelation reaction with heavy metals. Some industrial raw materials, leftover materials or waste materials contain water-soluble protein, such as cocoon shells, waste silk after silk reeling, sericin, fish meal, rice bran, mushroom stems, rapeseed dregs, bean dregs and the like, have the characteristics of rich sources, low price, easy biodegradation and the like, and are potential raw materials for preparing the water-soluble chelating agent.
In order to fully utilize the raw materials, the invention discloses a preparation method of a water-soluble chelating agent solution, which comprises the following steps:
cleaning and crushing industrial raw materials, leftover materials or waste materials containing water-soluble biological protein, wherein the particle size of the crushed raw materials is less than or equal to 5 mm;
pumping the cleaned and crushed raw materials into a subcritical extraction device, and extracting water-soluble biological protein under certain reaction conditions to obtain a water-soluble biological protein solution;
concentrating the water-soluble biological protein in the water-soluble biological protein solution obtained in the step to 0.01-0.1 g/mL by using an ultrafiltration membrane;
adding a certain amount of neutral protease or alkaline protease into the water-soluble biological protein concentrated solution obtained in the step, stirring and dissolving, adding a sodium hydroxide solution, adjusting the pH value to 7-10, putting the solution into a constant-temperature oscillator, reacting for 1-4 hours at a certain temperature, wherein the oscillation speed of the constant-temperature oscillator is 10-60 r/min, then freezing to inactivate the enzyme, and performing centrifugal filtration to obtain a protein peptide solution;
concentrating the protein peptide in the protein peptide solution to 0.05-0.5 g/mL by using an ultrafiltration membrane, and taking ultrafiltration membrane retentate to obtain a protein peptide concentrated solution, namely the water-soluble chelating agent solution.
Preferably, the industrial raw material, leftover or waste material containing the water-soluble biological protein is one or more of cocoon shell, waste silk after silk reeling, sericin, fish meal, rice bran, mushroom stem, rapeseed meal and bean dregs;
preferably, in the step of cleaning the industrial raw material, leftover or waste material containing water-soluble biological protein, firstly, ultrasonic cleaning is carried out, then, ethyl ether with the bath ratio of 1:20 is used for soaking for 24 hours, the soaked raw material is taken out, cleaned and dried by distilled water, then, soaked by absolute ethyl alcohol for 12 hours, and the soaked raw material is taken out, cleaned by distilled water and dried;
preferably, the subcritical extraction reaction conditions of the water-soluble biological protein are as follows: one of distilled water, a sodium carbonate aqueous solution, a potassium bicarbonate aqueous solution or a urea aqueous solution is used as an extracting agent, the reaction temperature is 100-320 ℃, and the pressure is 2-5.2 Mpa; the reaction device is made of nickel alloy, titanium alloy or stainless steel nickel-plated material.
Preferably, the water-soluble biological protein solution is added with the neutral protease or the alkaline protease in an amount of 0.1-2.5 mg/mL.
Preferably, the ultrafiltration membrane for concentrating the sericin peptide solution is made of polyvinylidene fluoride, polyether sulfone or polyacrylonitrile, and the pore diameter of the membrane is 0.005-0.01 mu m.
The invention also discloses the water-soluble chelating agent solution prepared according to the preparation method.
The invention also discloses a heavy metal wastewater treatment method, which comprises the following steps:
step 1, adjusting the pH value of heavy metal wastewater to be treated, adding the water-soluble chelating agent solution into the heavy metal wastewater, and stirring for a period of time to obtain a heavy metal chelate solution formed by complexing the water-soluble chelating agent and heavy metal;
step 2, concentrating and separating the obtained heavy metal chelate solution by an ultrafiltration membrane to obtain ultrafiltration concentrated solution, and recycling or discharging permeate;
step 3, adjusting the pH value of the ultrafiltration concentrated solution to decomplex and separate the heavy metal chelate;
step 4, treating the solution subjected to decomplexation separation by using an ultrafiltration membrane, enriching a water-soluble chelating agent to form a concentrated solution for recycling, wherein a permeate is a heavy metal concentrated solution;
and 5, purifying and recycling the heavy metal concentrated solution.
Preferably, in the step 1, the pH value of the heavy metal wastewater to be treated is adjusted to 3.5-7;
preferably, in the step 1, the mass ratio of the water-soluble chelating agent added into the heavy metal wastewater to the heavy metal in the wastewater is 1.2-10: 1.
Preferably, in the step 2 and the step 4, the ultrafiltration membrane material selected in the ultrafiltration concentration separation step is polyvinylidene fluoride, polyether sulfone or polyacrylonitrile, and the membrane aperture is 0.001-0.01 μm;
preferably, in steps 2 and 4, the ultrafiltration membrane concentration is carried out under the following operating conditions: the water inlet pressure is less than 0.5Mpa at room temperature.
Preferably, when the heavy metal chelate complex is decomplexed in the step 3, the pH value of the solution is adjusted to be 2-6.
Preferably, the step of purifying and recycling the heavy metal concentrated solution in the step 5 comprises: obtaining a high-purity metal product by adopting an extraction-reextraction-electrolysis process;
preferably, in the extraction process, a phosphoric acid extractant or a chelating extractant is selected;
further preferably, in the extraction process, 30-40% of P204 and 260# kerosene are selected as organic phases, or a chelating extraction agent and the kerosene are selected as the organic phases;
preferably, in the extraction process, the concentration of the extracting agent is 10%, compared with the ratio of O/A to 1: 1.
As a preferred embodiment of the invention, the invention discloses a heavy metal wastewater treatment method adopting the water-soluble chelating agent solution, as shown in figure 1, the method comprises the following steps: cleaning industrial raw materials, leftover materials or waste materials containing water-soluble biological protein by using distilled water, diethyl ether, absolute ethyl alcohol and the like, airing, adding the dried materials into a subcritical extraction device to extract the water-soluble biological protein to obtain a water-soluble biological protein solution, concentrating the prepared water-soluble biological protein solution by using an ultrafiltration membrane, adding protease into the concentrated solution to hydrolyze to obtain a protein peptide solution, and concentrating the prepared protein peptide solution by using the ultrafiltration membrane to obtain a water-soluble chelating agent solution; adding a water-soluble chelating agent solution into heavy metal-containing wastewater, carrying out chelation reaction on heavy metals in the wastewater and the water-soluble chelating agent, treating the reacted solution by using an ultrafiltration membrane, discharging or recycling the permeated solution, adding acid into a concentrated solution for decomplexing, treating the decomplexed solution by using the ultrafiltration membrane, recycling the concentrated solution, and recovering valuable metals from the permeated solution through extraction and electrolysis processes to finally obtain a high-purity metal product.
More specifically, the preparation of the water-soluble chelating agent and the method for the resource treatment of the heavy metal-containing wastewater by using the water-soluble chelating agent provided by the invention comprise the following specific steps:
(1) preparation of water-soluble chelating agent: the industrial raw material, offal or waste material containing water-soluble bioprotein is washed with distilled water and dried, wherein ultrasonic cleaning, for example, can be employed. Soaking in diethyl ether at bath ratio of 1:20 for 24 hr, taking out, washing with distilled water, and air drying. Soaking in anhydrous ethanol for 12 hr, taking out, washing with distilled water, and air drying. Putting the dried raw materials into a subcritical extraction device, and extracting water-soluble biological protein to obtain a water-soluble biological protein solution; and (2) condensing the water-soluble biological protein in the obtained water-soluble biological protein solution to 0.05g/mL by using an ultrafiltration membrane, adding a certain amount of neutral protease or alkaline protease into a water-soluble biological protein concentrated solution with a certain volume, stirring and dissolving the water-soluble biological protein concentrated solution, adding a sodium hydroxide solution to adjust the pH value to 7-10, putting the solution into a constant-temperature oscillator, reacting for 2 hours at a certain temperature, rotating at the speed of 30r/min, freezing at the temperature of-40 ℃, inactivating the enzyme, carrying out centrifugal filtration to obtain a protein peptide solution, and concentrating the protein peptide in the solution to 0.1g/mL by using the ultrafiltration membrane to obtain a protein peptide concentrated solution, namely a water-soluble chelating agent solution.
(2) And (2) adjusting the pH value of the wastewater containing heavy metals, adding the water-soluble chelating agent solution prepared in the step (1), and stirring for reaction to obtain a chelate solution formed by a water-soluble polymer and the heavy metals.
(3) Concentrating and separating the chelate solution formed by the water-soluble polymer and the heavy metal obtained in the step (2) by using an ultrafiltration membrane, enriching the chelate solution formed by the water-soluble polymer and the heavy metal to obtain ultrafiltration concentrated solution, and recycling or discharging the permeate.
(4) Adjusting pH value of the ultrafiltration concentrated solution to decomplex and separate the water-soluble polymer and the chelating agent formed by heavy metals.
(5) And (3) concentrating the solution subjected to decomplexing separation into a concentrated solution by using an ultrafiltration membrane, enriching the water-soluble chelating agent into the concentrated solution for recycling, wherein the permeate solution is a high-concentration heavy metal concentrated solution.
(6) Extracting and electrolyzing the high-concentration concentrated solution to obtain a high-purity metal solid product.
As a further improvement, in the step (1), the industrial raw material, leftover or waste material containing water-soluble biological protein is one or more of cocoon shell, waste silk after reeling silk, sericin, fish meal, rice bran, mushroom stem, rapeseed meal and bean dregs.
As a further improvement, in the step (1), the water-soluble bioprotein extracting solution is one of distilled water, a sodium carbonate aqueous solution, a potassium bicarbonate aqueous solution or a urea aqueous solution.
As a further improvement, in the step (1), the water-soluble biological protein extraction reaction conditions are as follows: the reaction temperature is 150-310 ℃.
As a further improvement, in the step (1), the sericin solution is added in an amount of 0.1-2.5 mg/mL of alkaline protease.
As a further improvement, in the step (2), the pH value of the wastewater containing the heavy metals is adjusted to 3.5-7.
As a further improvement, in the step (2), the mass ratio of the content of the water-soluble chelating agent in the water-soluble chelating agent solution to the content of the heavy metal in the wastewater is 1.2-10: 1, preferably 2-10: 1.
As a further improvement, in the step (3), the ultrafiltration membrane used in the ultrafiltration concentration separation step has a molecular weight cut-off greater than 5000.
As a further improvement, in the step (3), the operating conditions of the ultrafiltration concentration separation are as follows: the water inlet pressure is less than 0.5Mpa at room temperature.
As a further improvement, in the step (4), the pH value of the solution is adjusted to 2-6, preferably 3-6.
The technical solution and effects of the present invention are further described by several embodiments below.
Example 1
The mass fraction of water-soluble biological protein in the cocoon shell is 70%, and the cocoon shell is soaked in distilled water, then is subjected to ultrasonic cleaning and is crushed. 2000g of cleaned and crushed raw materials are taken, 80L of distilled water is added, and the raw materials are put into a subcritical extraction device for subcritical extraction, wherein the reaction temperature is 300 ℃, and the pressure is 2.5 MPa. Preparing a water-soluble biological protein solution, cooling at room temperature, concentrating the water-soluble biological protein in the prepared solution to 0.05g/mL by using an ultrafiltration membrane, taking 5L of water-soluble biological protein concentrated solution, adding 5g of alkaline protease, stirring and dissolving, adding a sodium hydroxide solution (1mol/L) to adjust the pH value to 9, putting the solution into a constant-temperature oscillator, reacting for 2 hours at 35 ℃ at the rotating speed of 30r/min, freezing at-40 ℃ to inactivate enzyme, carrying out centrifugal filtration, concentrating the supernatant to 0.1g/mL by using the ultrafiltration membrane to obtain a protein peptide solution, namely a water-soluble chelating agent solution, wherein the weight average molecular weight of protein peptide in the solution is 8000-10000.
Taking 50L of Cu-containing wastewater, adjusting the pH value of the wastewater to be 6.5, adjusting the Cu concentration to be 40mg/L and the calcium concentration to be 230mg/L, adjusting the pH value of the heavy metal-containing wastewater to be 6 by using 1mol/L sulfuric acid solution, adding 70mL of the prepared water-soluble chelating agent solution, and stirring for reaction to obtain a chelate solution formed by the water-soluble chelating agent and the heavy metal.
Concentrating and separating the obtained chelate solution formed by the water-soluble chelating agent and the heavy metal by a polyvinylidene fluoride ultrafiltration membrane (the molecular weight cutoff is 6000), enriching the chelate solution formed by the water-soluble polymer and the heavy metal to obtain an ultrafiltration concentrated solution, wherein the Cu concentration in the permeate liquid is 0.003mg/L, and the permeate liquid is discharged or recycled.
Adjusting pH of the ultrafiltration concentrated solution to 4.5 with 1mol/L sulfuric acid solution to decomplex and separate chelate formed by water soluble chelating agent and heavy metal.
And (3) concentrating the solution subjected to decomplexation separation into concentrated solution by using a polyvinylidene fluoride ultrafiltration membrane (the molecular weight cutoff is 7000), enriching the water-soluble chelating agent into the concentrated solution for recycling, wherein the recovery rate of the water-soluble chelating agent is 100%, the permeate solution is high-concentration heavy metal concentrated solution, and the concentration of Cu in the concentrated solution is 1200 mg/L.
Extracting and electrolyzing the high-concentration concentrated solution to obtain a high-purity metal solid product with the Cu grade of 98%.
Example 2
Washing and drying the waste silk after silk reeling with distilled water, wherein the mass fraction of water-soluble biological protein in the waste silk after silk reeling is 40%, and ultrasonically washing the waste silk raw material with distilled water. Taking 8000g of cleaned and crushed raw materials, adding 320L of distilled water into a subcritical extraction device for subcritical extraction, centrifugation and precipitation, carrying out subcritical extraction at the temperature of 310 ℃ and under the pressure of 3MPa to obtain a water-soluble biological protein solution, cooling at room temperature, concentrating the water-soluble biological protein in the prepared solution to 0.05g/mL by using an ultrafiltration membrane, taking 20L of the water-soluble biological protein concentrate, adding 12g of alkaline protease, stirring and dissolving, adding a sodium hydroxide solution (1mol/L) to adjust the pH value to 9, putting the solution into a constant-temperature oscillator, reacting at 35 deg.C for 2h at a rotation speed of 30r/min, freezing at-40 deg.C to inactivate enzyme, centrifuging, filtering, concentrating supernatant with ultrafiltration membrane, concentrating protein peptide in the solution to 0.1g/mL to obtain protein peptide solution, namely, the weight average molecular weight of the protein peptide in the water-soluble chelating agent solution is between 10000 and 15000.
Taking 50L of nickel-containing wastewater, adjusting the pH value of the wastewater to be 7.4, the Ni concentration to be 60mg/L, the calcium concentration to be 350mg/L and the magnesium concentration to be 180mg/L, adjusting the pH value of the wastewater containing heavy metal to be 6 by using 1mol/L of sulfuric acid solution, adding 150mL of the prepared water-soluble chelating agent solution into the wastewater, and stirring for reaction to obtain a chelate solution formed by a water-soluble polymer and heavy metal.
Concentrating and separating the obtained chelate solution formed by the water-soluble polymer and the heavy metal by a polyvinylidene fluoride ultrafiltration membrane (the cut-off molecular weight is 7000), enriching the chelate solution formed by the water-soluble chelating agent and the heavy metal to obtain an ultrafiltration concentrated solution, wherein the Ni concentration in the permeate is 0.06mg/L, and the permeate is discharged or recycled.
Adjusting pH value of the ultrafiltration concentrated solution to 5 with 1mol/L sulfuric acid solution to decomplex and separate chelate formed by the water-soluble chelating agent and heavy metal.
And (3) concentrating the solution subjected to decomplexation separation into concentrated solution by using a polyvinylidene fluoride ultrafiltration membrane (the molecular weight cutoff is 7000), enriching the water-soluble chelating agent into the concentrated solution for recycling, wherein the recovery rate of the water-soluble chelating agent is 100%, the permeate solution is high-concentration heavy metal concentrated solution, and the concentration of nickel in the concentrated solution is 1800 mg/L.
Extracting and electrolyzing the high-concentration concentrated solution to obtain a high-purity metal solid product, wherein the Ni grade of the product is 97%.
Example 3
Cleaning and airing the bean dregs with distilled water, wherein the mass fraction of water-soluble biological protein in the bean dregs is 20%, and ultrasonically cleaning the raw materials with distilled water. Putting 2000g of the cleaned raw material into 80L of aqueous solution for subcritical extraction (reaction temperature is 260 ℃, pressure is 2MPa), centrifuging, precipitating, taking supernatant to obtain water-soluble biological protein solution, cooling at room temperature, concentrating the water-soluble biological protein in the prepared solution to 0.05g/mL by using an ultrafiltration membrane, taking 5L of water-soluble biological protein concentrate, adding 3g of neutral protease, stirring for dissolution, adding sodium hydroxide solution (1mol/L) to adjust the pH value to 7, putting the solution into a constant temperature oscillator, reacting at 35 deg.C for 2 hr at rotation speed of 30r/min, freezing at-40 deg.C to inactivate enzyme, centrifuging, filtering, concentrating the supernatant with ultrafiltration membrane to obtain protein peptide concentrate with concentration of 0.1g/mL, namely a water-soluble chelating agent solution, wherein the weight average molecular weight of the protein peptide in the solution is 9000-14000.
Taking 50L of zinc-containing wastewater, wherein the pH value of the wastewater is 7.8, the Zn concentration is 90mg/L, the calcium concentration is 230mg/L, and the magnesium concentration is 110mg/L, adjusting the pH value of the heavy metal-containing wastewater to be 5.5 by using 1mol/L sulfuric acid solution, adding 180mL of the prepared water-soluble chelating agent solution, and stirring for reaction to obtain a chelate solution formed by the water-soluble chelating agent and the heavy metal.
Concentrating and separating the obtained chelate solution formed by the water-soluble chelating agent and the heavy metal by a polyvinylidene fluoride ultrafiltration membrane (the molecular weight cutoff is 6000), enriching the chelate solution formed by the water-soluble chelating agent and the heavy metal to obtain an ultrafiltration concentrated solution, wherein the concentration of Zn in the permeate is 0.02mg/L, and the permeate is discharged or recycled.
Adjusting pH of the ultrafiltration concentrated solution to 4.8 with 1mol/L sulfuric acid solution to decomplex and separate chelate formed by water-soluble polymer and heavy metal.
And (3) concentrating the solution subjected to decomplexation separation into concentrated solution by using a polyvinylidene fluoride ultrafiltration membrane (the molecular weight cutoff is 7000), enriching the water-soluble chelating agent into the concentrated solution for recycling, wherein the recovery rate of the water-soluble polymer is 100%, the permeate solution is high-concentration heavy metal concentrated solution, and the concentration of zinc in the concentrated solution is 2600 mg/L.
Extracting and electrolyzing the high-concentration concentrated solution to obtain a high-purity metal solid product with the zinc grade of 99%.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. The heavy metal wastewater treatment method is characterized by comprising the following steps:
step 1, preparation of a water-soluble chelating agent: cleaning and crushing industrial raw materials, leftover materials or waste materials containing water-soluble biological protein, wherein the particle size of the crushed raw materials is less than or equal to 5 mm; in the cleaning step, firstly, ultrasonic cleaning is carried out, then, ethyl ether with the bath ratio of 1:20 is used for soaking for 24 hours, the soaked raw materials are taken out and cleaned by distilled water and dried in the air, then, the raw materials are soaked by absolute ethyl alcohol for 12 hours, and the soaked raw materials are taken out and cleaned by distilled water and dried in the air;
pumping the cleaned and crushed raw materials into a subcritical extraction device, extracting water-soluble biological protein by using one of distilled water, a sodium carbonate aqueous solution, a potassium bicarbonate aqueous solution or a urea aqueous solution as an extracting agent at the reaction temperature of 100-320 ℃ and the pressure of 2-5.2 Mpa to obtain a water-soluble biological protein solution;
concentrating the water-soluble biological protein in the water-soluble biological protein solution obtained in the step to 0.01-0.1 g/mL by using an ultrafiltration membrane;
adding a certain amount of neutral protease or alkaline protease into the water-soluble biological protein concentrated solution obtained in the step, stirring and dissolving, and adding a water-soluble biological protein solution with the amount of the neutral protease or the alkaline protease being 0.1-2.5 mg/mL; adding a sodium hydroxide solution to adjust the pH value to 7-10, putting the solution into a constant temperature oscillator, reacting for 1-4 h at 150-310 ℃, wherein the oscillation speed of the constant temperature oscillator is 10-60 r/min, then freezing to inactivate enzyme, and carrying out centrifugal filtration to obtain a protein peptide solution;
concentrating the protein peptide in the protein peptide solution to 0.05-0.5 g/mL by using an ultrafiltration membrane, and taking ultrafiltration membrane retentate to obtain a protein peptide concentrated solution, namely a water-soluble chelating agent solution;
step 2, adjusting the pH value of the heavy metal wastewater to be treated to 3.5-7, and stirring the water-soluble chelating agent solution for a period of time to obtain a heavy metal chelate solution formed by complexing the water-soluble chelating agent and heavy metal; the mass ratio of the water-soluble chelating agent added into the heavy metal wastewater to the heavy metal in the wastewater is 2-10: 1;
step 3, concentrating and separating the obtained heavy metal chelate solution by using an ultrafiltration membrane to obtain ultrafiltration concentrated solution, and recycling or discharging permeate;
step 4, adjusting the pH value of the ultrafiltration concentrated solution to 3-6, and decomplexing and separating the heavy metal chelate;
step 5, treating the solution subjected to decomplexation separation by using an ultrafiltration membrane, enriching a water-soluble chelating agent to form a concentrated solution for recycling, wherein a permeate is a heavy metal concentrated solution;
step 6, purifying and recycling the heavy metal concentrated solution, and obtaining a high-purity metal product by adopting an extraction-back extraction-electrolysis process;
in the steps 3 and 5, the ultrafiltration membrane material selected in the ultrafiltration concentration separation step is polyvinylidene fluoride, polyether sulfone or polyacrylonitrile, and the cutoff molecular weight of the selected ultrafiltration membrane is larger than 5000; the operating conditions of ultrafiltration membrane concentration are as follows: the water inlet pressure is less than 0.5Mpa at room temperature.
2. The heavy metal wastewater treatment method of claim 1, wherein in the extraction process of step 6, a phosphoric acid extractant or a chelating extractant is selected.
3. The heavy metal wastewater treatment method of claim 2, wherein 30-40% of P204 and 260# kerosene are selected as the organic phase in the extraction process of step 6, or a chelating extractant and kerosene are selected as the organic phase.
4. The heavy metal wastewater treatment method of claim 2, wherein in the extraction process of step 6, the concentration of the extracting agent is 10% compared with that of O/A (1: 1).
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| CN1495225A (en) * | 2002-07-24 | 2004-05-12 | 山东美林亚生物科技有限公司 | Heavy metal chelator compound containing chitosan derivative |
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| CN102432123A (en) * | 2011-11-03 | 2012-05-02 | 北京大学 | Reproducible heavy metal complexing agent and application method thereof |
| WO2018035245A1 (en) * | 2016-08-18 | 2018-02-22 | Axiom Foods, Inc. | Chelating agents for reducing metal content in food products and methods related thereto |
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| CN102080118A (en) * | 2010-06-23 | 2011-06-01 | 东北农业大学 | Preparation method of rice bran antioxidant active protein peptide |
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| CN1495225A (en) * | 2002-07-24 | 2004-05-12 | 山东美林亚生物科技有限公司 | Heavy metal chelator compound containing chitosan derivative |
| CN1899985A (en) * | 2006-07-10 | 2007-01-24 | 三达膜科技（厦门）有限公司 | Treating, recovering and reutilizing method for electroplating waste liquid containing heavy metals |
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