CN102234617B - Method for separating and collecting microalgae by using magnetic medium - Google Patents

Abstract

The invention belongs to the field of separation of microalgae, in particular, the invention relates to a method for separating and collecting microalgae by using a magnetic medium. The method of the present invention comprises: (1) preparing Fe ₃ O ₄ nanoparticles, making it dispersed to form a stable suspension; (2) adjusting the pH value of the microalgae culture solution to 8-10; (3) adding step (1) The obtained magnetic separation medium is used in an amount of 0.01-0.04% w/v, and stirred; (4) performing magnetic separation on the microalgae obtained in step (3), and collecting the separated microalgae. According to the method of the invention, the synthesis steps of the magnetic separation medium are simple and easy to scale up; the amount of the magnetic separation medium is small; the stirring time is short, the efficiency is high, the operation of the separation process is simple, and the magnetic separation medium can be used repeatedly, which is beneficial to reduce the production cost.

Description

A method for separating and collecting microalgae using magnetic media

technical field

The invention belongs to the field of separation of microalgae, in particular, the invention relates to a method for separating and collecting microalgae by using a magnetic medium.

Background technique

Microalgae cultivation has been widely used in the fields of aquaculture, food, pharmaceuticals, and energy. However, the separation and collection of microalgae has become one of the main factors restricting the large-scale expansion of microalgae cultivation. The current separation and collection methods of microalgae mainly include: centrifugation, filtration, flocculation, and air flotation. The centrifugal method requires expensive investment in fixed assets (centrifuge) and high energy consumption; the efficiency of the filtration method is low, the membrane is easily blocked, and the operation is difficult; the separation and collection of microalgae using the flocculation method requires the use of various magnetic separation media, and Magnetic separation medium is difficult to separate from microalgae, and it is easy to cause contamination of the target product; air flotation separation usually needs the assistance of magnetic separation medium or surfactant when applied to microalgae, which has the same problem as flocculation method.

Due to the characteristics of easy separation and simple separation operation of magnetic materials, methods for separating microalgae using magnetic materials have been reported in recent years. Gao and Peng et al. successfully separated harmful microalgae Microcystis aeruginosa from water by using a composite of montmorillonite and copper-iron oxide. The magnetic separation medium can be reused, but the synthesis of the magnetic composite is cumbersome. And the amount is relatively large (Gao Z.W., Peng X.J., Zhang H.M., Luan Z.K., Fan B.Desalination, 2009, 247, 337); Liu and Li et al. used chitosan-modified magnetic polymers as magnetic separation media to successfully remove freshwater Algal blooms in the medium, but the synthesis of the magnetic separation medium is relatively complicated, the magnetic separation medium cannot be reused, and is greatly affected by the ionic strength (Liu D., Li F.T., Zhang B.R. Water Sci. Technol. 2009, 59, 1085). It can be seen that the separation and collection of microalgae using existing magnetic materials requires complex material synthesis, and often requires modification or coating of polymers to couple with algal cells, which greatly increases the cost. Therefore, many It is difficult to apply it on a large scale, and its separation of microalgae in the culture fluid system has not yet been experimentally verified.

Contents of the invention

The object of the present invention is to provide an efficient and fast microalgae separation and collection method using magnetic nanoparticles as a magnetic separation medium.

In the present invention _{, Fe3O4} nanoparticles are used as the magnetic separation medium, and the magnetic separation medium is added after the cultivation of the microalgae is completed, and after being fully mixed by stirring, the magnetic separation and collection of the microalgae is realized by using a permanent magnet.

According to the method for separating and collecting microalgae using magnetic media of the present invention, the method comprises the following steps:

(1) Prepare Fe ₃ O ₄ nanoparticles, disperse them to form a stable suspension, and obtain a magnetic separation medium for subsequent use;

(2) adjusting the pH value of the microalgae culture solution to 8-10, within the pH range, the algae cells are positively charged, so that they can be combined with the magnetic medium through the force of charge;

(3) adding the magnetic separation medium obtained in step (1), the amount of the magnetic separation medium is 0.01-0.04% w/v, and stirring;

(4) Carry out magnetic separation to the microalgae obtained in step (3), remove the supernatant, and collect the microalgae obtained by separation, wherein Fe ₃ O ₄ nanometers can be combined with the microalgae cell surface, and can also enter in the microalgae, Combine with it.

Preferably, according to the method of the present invention, in step (2), the microalgae culture solution is placed in a stirred reactor, the temperature in the stirred reactor is adjusted to 20-35°C, and the stirring time is 1-3 minutes If the stirring time is too short, Fe ₃ O ₄ nanometers and microalgal cells cannot be fully combined. If the stirring time is too long, the shear force of mechanical stirring will re-disperse the surface-bound Fe ₃ O ₄ nanometers and microalgal cells. Reduce the separation effect of microalgae.

Preferably, according to the method for separating and collecting microalgae using magnetic media according to the present invention, in step (4), the magnetic field strength of 1000-3000 Oersted is selected for the magnetic separation of microalgae.

According to the method for separating and collecting microalgae using magnetic media of the present invention, wherein the microalgae collected in step (4) is subjected to the extraction of target metabolites, the microalgae residue containing the magnetic separation medium obtained after separation is heated at a high temperature of 200-400 Calcining under nitrogen atmosphere at ℃ for 1-2 hours to remove cell residues, recover Fe ₃ O ₄ nanoparticles, and reuse them for separation and collection of microalgae.

According to the method for separating and collecting microalgae using magnetic media, the concentration of the Fe ₃ O ₄ nanoparticle suspension is 1-5% w/v, preferably 2% w/v. If the concentration of the suspension is too thin, the amount of nanoparticle suspension added in the microalgae culture system will be increased, which will cause the concentration of microalgae cells to be diluted and reduce the separation effect of microalgae; if the concentration of the suspension is too high, the collision of nanoparticles in the suspension will be increased. chance, resulting in the agglomeration of nanoparticles and eventually precipitation, the suspension is not easy to preserve, and the separation effect of microalgae is reduced.

Therefore, preferably, adopt magnetic medium to separate according to the present invention, the method for collecting microalgae comprises the following steps:

(1) Prepare Fe ₃ O ₄ nanoparticles by using the method reported in the literature (Peng ZG, Hidajat K., Uddin MS, J.ColloidInterface Sci., 2004, 271, 277), and disperse them in deionized In water, a stable suspension is formed to obtain a magnetic separation medium, which is then stored in a refrigerator for later use;

(2) Put the microalgae culture solution obtained from the cultivation into a stirred reactor, and adjust the temperature in the stirred reactor to be 20-30° C., and the pH value to be 8-10;

(3) at a rotating speed of 100-300rpm, add the magnetic separation medium obtained in step (1) to separate the microalgae in the culture solution, the consumption of the magnetic separation medium is 0.01-0.04% (w/v), and the stirring time 1-3 minutes;

The magnetic separation medium is in the form of a solution, and Fe ₃ O ₄ nanoparticles are the effective components of the magnetic separation medium, which are uniformly dispersed in the solution, and the concentration is controlled at 1-5% (w/v), so that it can be stored in a refrigerator. Still maintain high activity in the process, its preferred value is 2% (w/v);

(4) Selecting a permanent magnet with a magnetic field strength of 1000-3000 Oersted is placed on the bottom of the reactor, and the microalgae in the step (3) are magnetically separated, and the time for standing the magnetic separation is 1-3 minutes, and finally the upper layer is removed supernatant, collecting the isolated microalgae cells;

(5) The microalgae cells (containing magnetic separation medium) collected in step (4) are subjected to the extraction of target metabolites, and the microalgae cell residues (containing magnetic separation medium) obtained after separation are placed under a nitrogen atmosphere at a high temperature of 200-400°C Calcination for 1-2 hours to remove microalgae residues, the heating rate is 2-5°C/min, the recovered Fe ₃ O ₄ nanoparticles are washed 3 times with deionized water to remove a small amount of ash, and then ultrasonically treated with a power of 200-400w for 10-30 Minutes, the magnetic separation medium was prepared with deionized water and reused for the separation and collection of microalgae.

The microalgae cells (magnetic separation medium) collected in the step (5) can also be directly calcined and followed up according to the conditions in step (5) without extraction and other treatments according to actual needs, so as to realize the repeated use of the magnetic separation medium .

The advantages of the method for separating and collecting microalgae cells using magnetic nanoparticles as a magnetic separation medium of the present invention are:

(1) The synthesis steps of the magnetic separation medium are simple and easy to scale up;

(2) Due to the large specific surface area of magnetic nanoparticles, the amount of magnetic separation medium is small;

(3) The stirring time is short, the efficiency is high, and the separation process is easy to operate;

(4) The magnetic separation medium can be used repeatedly, which is beneficial to reduce the production cost.

Description of drawings

Fig. 1 is the transmission electron microscope TEM photo of the botrytis obtained after the separation in Example 1 of the present invention.

Figure 2 is the effect of stirring time on the separation effect of botrytis in Example 1 of the present invention.

Detailed ways

Example 1

Separate and collect the botrytis in the botrytis culture fluid with the method of the present invention, its step is as follows:

The prepared Fe ₃ O ₄ nanoparticles were dispersed in deionized water to form a stable suspension, prepared into a magnetic separation medium with a concentration of 2% (w/v), and then placed in a refrigerator for later use. The botrytis culture solution obtained by cultivating is placed in a stirred reactor, the temperature in the adjusted stirred reactor is 20° C., the pH value is 8, and a magnetic separation medium is added at a rotating speed of 100 rpm. The consumption of the magnetic separation medium is 0.04% (w /v), the stirring time was 1 minute; a permanent magnet with a magnetic field strength of 1000 Oersted was selected to be placed on the bottom of the reactor, and the botrytis was magnetically separated, left to stand for 1 minute, the supernatant was removed, and the botrytis obtained by separation was collected , the recovery rate of botrytis reached 99.8%. After the isolated botrytis (containing magnetic separation medium) is extracted from oil, the isolated botrytis residue (containing magnetic separation medium) is calcined at a high temperature of 200°C under a nitrogen atmosphere for 2 hours to remove microalgae cell residues, and the heating rate is 2 °C/min, the recovered Fe ₃ O ₄ nanoparticles were washed 3 times with deionized water to remove a small amount of ash, and then ultrasonically treated with a power of 200w for 30 minutes, and deionized water was used to prepare a magnetic separation medium for reuse in the separation and collection of botrytis . The transmission electron microscope TEM photo of the botrytis obtained after separation is shown in Figure 1, and the effect of stirring time on the separation effect of the botrytis is shown in Figure 2.

Example 2

Separate and collect the botrytis in the botrytis culture fluid with the method of the present invention, its step is as follows:

The prepared Fe ₃ O ₄ nanoparticles were dispersed in deionized water to form a stable suspension, prepared into a magnetic separation medium with a concentration of 1% (w/v), and then placed in a refrigerator for later use. Put the botrytis culture solution obtained by cultivating into a stirred reactor, adjust the temperature in the stirred reactor to be 30°C, and the pH value is 10, add a magnetic separation medium at a rotating speed of 300rpm, and the consumption of the magnetic separation medium is 0.02% (w /v), the stirring time was 2 minutes; a permanent magnet with a magnetic field strength of 2000 Oersted was selected to be placed on the bottom of the reactor, and the botrytis was magnetically separated, left to stand for 2 minutes, the supernatant was removed, and the botrytis obtained by separation was collected , the recovery rate of botrytis reached 97.5%. After the isolated botrytis (containing magnetic separation medium) is extracted from oil, the isolated botrytis residue (containing magnetic separation medium) is calcined at a high temperature of 400°C under a nitrogen atmosphere for 1 hour to remove microalgae cell residues at a heating rate of 5 °C/min, the recovered Fe ₃ O ₄ nanoparticles were washed 3 times with deionized water to remove a small amount of ash, and then ultrasonically treated with a power of 400w for 10 minutes, and deionized water was used to prepare a magnetic separation medium for reuse in the separation and collection of botrytis .

Example 3

Separate and collect the botrytis in the botrytis culture fluid with the method of the present invention, its step is as follows:

The prepared Fe ₃ O ₄ nanoparticles were dispersed in deionized water to form a stable suspension, prepared into a magnetic separation medium with a concentration of 5% (w/v), and then placed in a refrigerator for later use. The botrytis culture solution obtained by cultivating is placed in a stirred reactor, the temperature in the stirred reactor is adjusted to be 25° C., the pH value is 9, and a magnetic separation medium is added at a rotating speed of 200 rpm. The consumption of the magnetic separation medium is 0.01% (w /v), the stirring time was 3 minutes; a permanent magnet with a magnetic field strength of 3000 Oersted was selected to be placed on the bottom of the reactor, and the botrytis was magnetically separated, left to stand for 3 minutes, and finally the supernatant was removed, and the grapes obtained by separation were collected. The recovery rate of algae and botrytis reached 98.6%. After the isolated botrytis (containing magnetic separation medium) is extracted from oil, the isolated botrytis residue (containing magnetic separation medium) is calcined at a high temperature of 300°C under a nitrogen atmosphere for 1.5 hours to remove microalgae cell residues at a heating rate of 3 °C/min, the recovered Fe ₃ O ₄ nanoparticles were washed 3 times with deionized water to remove a small amount of ash, and then ultrasonically treated with a power of 300w for 20 minutes, and deionized water was used to prepare a magnetic separation medium for reuse in the separation and collection of botrytis .

Example 4

Using the method of the present invention to separate and collect the chlorella in the chlorella culture fluid, the steps are as follows:

The prepared Fe ₃ O ₄ nanoparticles were dispersed in deionized water to form a stable suspension, prepared into a magnetic separation medium with a concentration of 2% (w/v), and then placed in a refrigerator for later use. The chlorella culture solution obtained by cultivating is placed in a stirred reactor, the temperature in the stirred reactor is adjusted to be 25° C., the pH value is 10, and a magnetic separation medium is added at a rotating speed of 300 rpm. The consumption of the magnetic separation medium is 0.04% ( w/v), and the stirring time was 2 minutes; a permanent magnet with a magnetic field strength of 1000 Oersted was selected to be placed on the bottom of the reactor, and the chlorella was magnetically separated, left to stand for 2 minutes, and finally the supernatant was removed, collected and separated to obtain Chlorella, the recovery rate of chlorella reaches 98.9%. After the isolated chlorella (containing magnetic separation medium) is subjected to oil extraction, the isolated chlorella residue (containing magnetic separation medium) is calcined at a high temperature of 400° C. for 1 hour under a nitrogen atmosphere to remove chlorella cell residues, The heating rate is 5°C/min, and the recovered Fe ₃ O ₄ nanoparticles are washed 3 times with deionized water to remove a small amount of ash, and then ultrasonically treated with a power of 400w for 10 minutes, and the magnetic separation medium is prepared with deionized water and reused in pellets Separation and collection of algae.

Example 5

Using the method of the present invention to separate and collect the chlorella in the chlorella culture fluid, the steps are as follows:

The prepared Fe ₃ O ₄ nanoparticles were dispersed in deionized water to form a stable suspension, prepared into a magnetic separation medium with a concentration of 1% (w/v), and then placed in a refrigerator for later use. The chlorella culture solution obtained by cultivating is placed in a stirred reactor, the temperature in the stirred reactor is adjusted to be 20° C., the pH value is 8, and a magnetic separation medium is added at a speed of 200 rpm. The consumption of the magnetic separation medium is 0.01% ( w/v), and the stirring time was 3 minutes; a permanent magnet with a magnetic field strength of 3000 Oersted was selected to be placed on the bottom of the reactor, and the chlorella was magnetically separated, left to stand for 3 minutes, and finally the supernatant was removed, collected and separated to obtain Chlorella, the recovery rate of chlorella reaches 99.5%. After the isolated chlorella (containing the magnetic separation medium) is subjected to oil extraction, the isolated chlorella residue (containing the magnetic separation medium) is calcined at a high temperature of 200° C. under a nitrogen atmosphere for 2 hours to remove the chlorella cell residues, The heating rate is 2°C/min, the recovered Fe ₃ O ₄ nanoparticles are washed 3 times with deionized water to remove a small amount of ash, and then ultrasonically treated with a power of 200w for 30 minutes, and the magnetic separation medium is prepared with deionized water and reused in pellets Separation and collection of algae.

Example 6

Using the method of the present invention to separate and collect the chlorella in the chlorella culture fluid, the steps are as follows:

The prepared Fe ₃ O ₄ nanoparticles were dispersed in deionized water to form a stable suspension, prepared into a magnetic separation medium with a concentration of 5% (w/v), and then placed in a refrigerator for later use. The chlorella culture solution obtained by cultivating is placed in a stirred reactor, the temperature in the stirred reactor is adjusted to be 30° C., the pH value is 9, and a magnetic separation medium is added at a rotating speed of 100 rpm. The consumption of the magnetic separation medium is 0.03% ( w/v), the stirring time is 1 minute; the permanent magnet with a magnetic field strength of 2000 Oersted is selected to be placed on the bottom of the reactor, and the flocculated chlorella is magnetically separated, and the flocculated chlorella is left to stand for 1 minute, and finally the supernatant is removed, collected and separated The obtained chlorella has a recovery rate of 97.8%. After the isolated chlorella (containing magnetic separation medium) is extracted from oil, the isolated chlorella residue (containing magnetic separation medium) is calcined at a high temperature of 300° C. under a nitrogen atmosphere for 1.5 hours to remove chlorella cell residues, The heating rate is 4°C/min, and the recovered Fe ₃ O ₄ nanoparticles are washed 3 times with deionized water to remove a small amount of ash, and then ultrasonically treated with a power of 300w for 20 minutes, and deionized water is used to prepare a magnetic separation medium and reuse it for pellets Separation and collection of algae.

Claims (3)

1. method that adopts magnetic medium to separate, collect little algae said method comprising the steps of:

(1) preparation Fe ₃O ₄Nano particle, making it disperse to form stable concentration is 1-5%w/v suspension-s, it is subsequent use to obtain the magnetic resolution medium;

(2) the pH value of adjusting micro algae culturing liquid is 8-10;

(3) add the magnetic resolution medium that step (1) obtains, the consumption of magnetic resolution medium is 0.01-0.04%w/v, and stirs 1-3 minute in 20-30 ℃;

(4) the little algae that obtains in the step (3) is carried out magnetic and separate, remove supernatant liquid, collect and separate the little algae that obtains; When little algae carried out the magnetic separation, selecting magneticstrength for use was the 1000-3000 oersted.

2. employing magnetic medium according to claim 1 separates, collects the method for little algae, it is characterized in that Fe ₃O ₄The concentration of nano granule suspension is 2%w/v.

3. employing magnetic medium according to claim 1 separates, collects the method for little algae; It is characterized in that; Little algae that step (4) is collected carries out the extraction of purpose meta-bolites, and the little algae residue that contains the magnetic resolution medium that obtains after the separation was calcined 1-2 hour under high temperature 200-400 ℃ nitrogen atmosphere, removed a small amount of ash content 3 times with deionized water wash; Use power 200-400w again supersound process 10-30 minute, obtain Fe ₃O ₄Nano particle is reused for the separated and collected of little algae.

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