阅读说明：本技术 一种用于环境修复中微藻固定化的改性环保载体的制备方法 (Preparation method of modified environment-friendly carrier for microalgae immobilization in environmental remediation ) 是由 陆胤 虞哲富 赵永纲 叶明立 许晓路 张雯 于 2021-01-05 设计创作，主要内容包括：本发明公开了一种用于环境修复中微藻固定化的改性环保载体的制备方法,属于环境保护技术领域。该方法以玉米秸秆、菌草和甘蔗渣这些有机废物为原料,将其压榨脱水、脱毛粉碎、改性处理,并将多糖凝胶等新型碳源与之混合,制成有利于异养微藻定植和碳源缓释的有机生物固定化载体,用以培育和诱导藻类生长,修复富营养化水体。本发明的改性环保载体的制备方法具有操作方便、经济环保和有利于微藻定植的特点。(The invention discloses a preparation method of a modified environment-friendly carrier for microalgae immobilization in environmental remediation, and belongs to the technical field of environmental protection. The method takes corn straws, Juncao and bagasse as raw materials, the organic wastes are subjected to squeezing dehydration, unhairing and crushing, modification treatment, and polysaccharide gel and other novel carbon sources are mixed with the organic wastes to prepare the organic biological immobilized carrier which is beneficial to heterotrophic microalgae field planting and carbon source slow release, and is used for cultivating and inducing algae growth and restoring eutrophic water. The preparation method of the modified environment-friendly carrier has the characteristics of convenience in operation, economy, environmental friendliness and contribution to microalgae planting.)

1. A preparation method of a modified environment-friendly carrier for microalgae immobilization in environmental remediation is characterized by comprising the following steps:

(1) the raw materials comprise: weighing 30-50 parts of corn straw, 12-18 parts of juncao and 1-6 parts of bagasse in parts by weight, and uniformly mixing to obtain a mixed sample;

(2) unhairing and crushing: filtering the mixed sample by using a stainless steel screen mesh of 1-5 meshes, drying at 100-110 ℃, taking out, cooling to normal temperature, and crushing by using a crusher to obtain mixed powder with the particle size of 0.2-0.9 mm;

(3) squeezing and dewatering: placing the mixed powder obtained in the step (2) in a NaOH solution with the volume concentration of 10%, uniformly stirring, standing and soaking for 12-15 h to obtain a feed liquid, filtering the feed liquid and squeezing to obtain a squeezed material; the weight ratio of the mixed powder to the NaOH solution is 1: 15-20;

(4) modification treatment: pouring epoxy chloropropane into a reaction kettle containing a squeezed material until the squeezed material is completely soaked, and reacting for 6-8 h at the temperature of 60-70 ℃ and the rpm of 150-250; pouring out the liquid, pouring trimethylamine until the squeezed material is completely soaked, and reacting for 4-6 h at the temperature of 70-80 ℃ and the speed of 150-250 rpm; after the reaction is finished, filtering the squeezed material, washing the squeezed material by using a mixed solution of equivalent ethanol and 0.1mol/L hydrochloric acid, finally washing the squeezed material by water to be neutral, and drying the washed material to obtain modified organic fiber powder;

(5) mixing: preparing the polysaccharide gel into a hot dissolving solution with the mass concentration of 2-3% by using water at the temperature of more than 80 ℃, mixing the organic fiber powder obtained in the step (4) with the hot dissolving solution to form a suspension, and cooling to room temperature to form organic fiber rubber balls; the weight ratio of the organic fiber powder to the heat dissolving liquid is 1: 15-20.

Technical Field

The invention belongs to the technical field of environmental protection, and particularly relates to a preparation method of a modified environment-friendly carrier for microalgae immobilization in environmental remediation.

Background

In recent years, the repair capability of microalgae in eutrophic ecosystems is receiving attention internationally. The microalgae has short growth period and high growth speed, has the capability of absorbing a large amount of water nutrition, can produce high-added-value products such as grease, protein, carotene, DHA, EPA and the like, and effectively carries out resource development and utilization on nutrient-rich substances. The bio-utilization of microalgae includes two major groups, one is photoautotrophic algae, which synthesize glucose, starch, oil and many carotenes by fixing carbon dioxide by photosynthesis using sunlight as energy, and the biosynthesis of such microalgae is well known. The large-scale culture of the microalgae mainly depends on a photobioreactor and a running pond, the main limiting factors are light and carbon dioxide, and inorganic nutrition is mainly utilized. Another class of microalgae is heterotrophic microalgae, which actively absorb and utilize organic carbon, convert it to energy in the presence of oxygen, and synthesize glucose, lipids and carotene. This class of algae lives primarily at the bottom water interface and needs to have sufficient oxygen to aid its digestion and absorption. Another class of algae is mixed nutrition, which combines the capabilities of photoautotrophy and heterotrophy, and can actively utilize inorganic and organic nutrients for cell growth and propagation. At present, the international attention is paid to the sewage treatment of mixed nutrition and heterotrophic algae, the mixed nutrition and heterotrophic algae have special effects on the aspect of pollutant recycling, the effects and the efficiency are even higher than those of microorganisms, and products of the mixed nutrition and heterotrophic algae can be transferred through a food chain, so that the mixed nutrition and heterotrophic algae have great market potential and are a new hopeful star for sewage treatment.

In the aspect of nitrogen and phosphorus removal by microalgae immobilization, Heng Liang research group finds that the immobilized microalgae can be used for treating organic matters in anaerobic digestion waste liquid, can also be used for rapidly recovering the microalgae, and simultaneously reduces membrane pollution. Wuyi Cheng utilizes the biochar-sodium alginate combined immobilization chlorella to promote the growth of the chlorella and remove ammonia nitrogen in water, and the removal rate of the ammonia nitrogen is improved along with the increase of the addition amount of the rubber balls and the particle size of the rubber balls. The research of the university of Cranfield and the university of RMIT jointly discovers that 60% of application cost is reduced while nitrogen and phosphorus in a water body are removed in the operation of the immobilized microalgae reactor. In addition, the wenqi Yuan research group carries out attachment research on microalgae and materials, and further provides advantages of microalgae semi-immobilization on nitrogen and phosphorus removal and microalgae harvesting.

At present, the existing microalgae immobilization methods can be roughly divided into four types: entrapment, adsorption, cross-linking and covalent bonding. The embedding method is to limit the microalgae in a limited space such as a tiny lattice or a microcapsule of gel, or to diffuse the microalgae cells into a porous carrier, and simultaneously to allow the matrix to permeate and the product to diffuse out. The adsorption method is a method for fixing microalgae cells on the surface and inside of a carrier to form a biological membrane according to the action of static electricity, surface tension and adhesion force between the charged microalgae cells and the carrier. The cross-linking method is also called carrier-free immobilization method, and utilizes the reaction of amino and hydroxyl of enzyme molecules in the microalgae and functional groups of a cross-linking agent to form covalent bonds through cross-linking, so that the microalgae mutually form a network structure to realize the immobilization purpose. The covalent method is to bind the water-insoluble carrier and the enzyme in a covalent bond.

The immobilized material has the characteristics of low toxicity to microalgae, porosity, fast mass transfer, good stability, no specific adsorption, functional groups suitable for introducing ligands, difficult degradation by the microalgae, high strength, long service life, low price and the like. Different materials have differences of performance and fixing modes, wherein SA (sodium alginate), carrageenan, agar, gelatin and the like are natural carriers, but have the defects of poor stability and the like; the artificial synthesis carriers such as PVA (polyvinyl alcohol), ACRM (polyacrylamide) and the like are used, so that secondary environmental pollution is easily caused in the material degradation process; the activated carbon, the porous argil and the microporous glass are inorganic carriers, so the economic cost is higher.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a preparation method of a modified environment-friendly carrier for immobilizing microalgae in environmental remediation.

In order to achieve the purpose, the invention adopts the following technical scheme: a preparation method of a modified environment-friendly carrier for microalgae immobilization in environmental remediation specifically comprises the following steps:

(1) the raw materials comprise: weighing 30-50 parts of corn straw, 12-18 parts of juncao and 1-6 parts of bagasse in parts by weight, and uniformly mixing to obtain a mixed sample;

(2) unhairing and crushing: filtering the mixed sample by using a stainless steel screen mesh of 1-5 meshes, drying at 100-110 ℃, taking out, cooling to normal temperature, and crushing by using a crusher to obtain mixed powder with the particle size of 0.2-0.9 mm;

(3) squeezing and dewatering: placing the mixed powder obtained in the step (2) in a NaOH solution with the volume concentration of 10%, uniformly stirring, standing and soaking for 12-15 h to obtain a feed liquid, filtering the feed liquid and squeezing to obtain a squeezed material; the weight ratio of the mixed powder to the NaOH solution is 1: 15-20;

(4) modification treatment: pouring epoxy chloropropane into a reaction kettle containing a squeezed material until the squeezed material is completely soaked, and reacting for 6-8 h at the temperature of 60-70 ℃ and the rpm of 150-250; pouring out the liquid, pouring trimethylamine until the squeezed material is completely soaked, and reacting for 4-6 h at the temperature of 70-80 ℃ and the speed of 150-250 rpm; after the reaction is finished, filtering the squeezed material, washing the squeezed material by using a mixed solution of equivalent ethanol and 0.1mol/L hydrochloric acid, finally washing the squeezed material by water to be neutral, and drying the washed material to obtain modified organic fiber powder;

(5) mixing: preparing the polysaccharide gel into a hot dissolving solution with the mass concentration of 2-3% by using water at the temperature of more than 80 ℃, mixing the organic fiber powder obtained in the step (4) with the hot dissolving solution to form a suspension, and cooling to room temperature to form organic fiber rubber balls; the weight ratio of the organic fiber powder to the heat dissolving liquid is 1: 15-20.

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

(1) the operation is convenient: the preparation method of the modified environment-friendly carrier is beneficial to industrial large-scale production;

(2) economic and environment-friendly: the raw materials selected in the invention are organic waste residues, so that the cost is greatly reduced; low toxicity to microorganism, porosity, fast mass transfer, good stability, no specific adsorption, suitability for introducing functional groups of ligands, difficult degradation, high strength, long service life and the like.

(3) Beneficial to microalgae planting: microalgae are fixedly planted in the organic fiber colloidal spheres, microalgae cells can diffuse into the porous carrier, simultaneously matrix can permeate and products can diffuse out, and the survival rate of the microalgae is higher than that of single polysaccharide gel colloidal particles.

(4) Is beneficial to environmental remediation: the prepared environment-friendly carrier is planted in a specific water area, and the carbon slow-release effect of the polysaccharide micelle is utilized under the aerobic condition to induce the germination of the benthic mixed nutrient algae, thereby playing an environment-repairing role in eutrophic water quality.

Drawings

FIG. 1 is a microscope image of the initial algal membrane on the surface of the carrier;

FIG. 2 is a scanning electron microscope image of the mixed sample and the modified organic fiber powder; fig. 2(a) is an SEM of the mixed sample, and fig. 2(b) is an SEM of the modified organic fiber powder;

fig. 3 is a Cls and Nls orbital energy spectrum of the mixed sample and modified organic fiber powder: fig. 3(a) is a Cls orbital spectrum of the mixed sample and the modified organic fiber powder, and fig. 3(b) is an Nls orbital spectrum of the mixed sample and the modified organic fiber powder.

Detailed Description

The invention is further illustrated by the following examples in conjunction with the accompanying drawings and examples, which are set forth to further illustrate the invention and are not to be construed as limiting the scope thereof.

Example 1

(1) The raw materials comprise: weighing 500g of corn straw, 180g of juncao and 60g of bagasse, and uniformly mixing to obtain a mixed sample;

(2) unhairing and crushing: filtering the mixed sample by a stainless steel screen mesh with 5 meshes to remove impurities in the mixed sample, drying at 110 ℃, taking out, cooling to normal temperature, and crushing and screening by a crusher to finally obtain mixed powder with the particle size of 0.9 mm.

(3) Squeezing and dewatering: putting the mixed powder obtained in the step (2) into a NaOH solution with the volume concentration of 10%, wherein the weight ratio of the mixed powder to the NaOH solution is 1: 15; stirring uniformly by a glass rod, standing and soaking for 15h to obtain a feed liquid, filtering the feed liquid by a Buchner funnel, and squeezing to obtain a squeezed material.

(4) Modification treatment: and (3) putting the squeezed material obtained in the step (3) into a glass reaction kettle, pouring 1000mL of epoxy chloropropane to ensure that the squeezed material is completely soaked, reacting for 8h at 70 ℃ and 250rpm, pouring off liquid, slowly pouring 1000mL of trimethylamine to ensure that the material is completely soaked, and reacting for 6h at 80 ℃ and 250 rpm. After the reaction is finished, filtering the squeezed material by using gauze, washing the squeezed material by using a mixed solution of equal amount of ethanol and 0.1mol/L hydrochloric acid, finally washing the squeezed material by using ultrapure water to be neutral, and drying the washed material to obtain 387g of modified organic fiber powder.

(5) Mixing: preparing the polysaccharide gel into a hot dissolving solution with the mass concentration of 3% by using water, mixing 387g of the organic fiber powder obtained in the step (4) with the hot dissolving solution according to the weight ratio of 1:20 to form a suspension, cooling to room temperature, and forming a large number of organic fiber rubber balls under the action of surface tension.

The organic fiber rubber ball collected by the method is subjected to microalgae planting and observed under a microscope, and the result is shown in figure 1, and the microalgae cells are fixed on the surface of the carrier to form a biological film according to the action of static electricity, surface tension and adhesion force between the charged microalgae cells and the carrier. The result shows that the microalgae grows well on the modified environment-friendly carrier after the immobilization is finished, the ammonia nitrogen in water is removed while the growth of the microalgae is promoted under the synergistic effect of the adsorption effect of the biochar and the nutrition absorption capacity of the microalgae, and the removal rate of the ammonia nitrogen is improved along with the increase of the addition amount of the rubber balls and the particle size of the rubber balls.

Example 2

(1) The raw materials comprise: weighing 30g of corn straw, 12g of juncao and 1g of bagasse, and uniformly mixing to obtain a mixed sample;

(2) unhairing and crushing: filtering the mixed sample by a stainless steel screen mesh of 1 mesh, drying at 100 ℃, taking out, cooling to normal temperature, crushing and screening by a crusher to obtain mixed powder with the particle size of 0.2 mm.

(3) Squeezing and dewatering: putting the mixed powder obtained in the step (2) into a NaOH solution with the volume concentration of 10%, wherein the weight ratio of the mixed powder to the NaOH solution is 1: 20; stirring uniformly by a glass rod, standing and soaking for 12h to obtain a feed liquid, and filtering and squeezing the obtained feed liquid by a Buchner funnel to obtain a squeezed material.

(4) Modification treatment: putting the squeezed material into a glass reaction kettle, pouring 100mL of epoxy chloropropane to ensure that the squeezed material is completely impregnated, and reacting for 6h at the temperature of 60 ℃ and the speed of 150 rpm; the liquid was decanted off and 100mL of trimethylamine was slowly poured in to completely impregnate the squeezed material, and the reaction was carried out at 70 ℃ and 150rpm for 4 hours. And after the reaction is finished, filtering the squeezed material by using gauze, washing the squeezed material by using a mixed solution of equivalent ethanol and 0.1mol/L hydrochloric acid, finally washing the squeezed material by using ultrapure water to be neutral, and drying the washed material to obtain 38g of modified organic fiber powder. FIG. 2(a) is a SEM of a mixed sample with a more compact surface structure and no significant voids. Fig. 2(b) is an SEM of the modified organic fiber powder, and it can be seen that the modified surface is smoother, homogeneous cellulose filaments are almost completely exposed, and the bundles are tightly bound together and have diameters of substantially about 5 μm. By comparing the surface microscopic images of the mixed sample and the modified organic fiber powder, it is speculated that most of the cellulose filaments are exposed after modification, and the modification process can better directly react with cellulose, so that quaternary ammonium groups can be introduced to the surface of the cellulose filaments to become active adsorption sites of microalgae cells.

(5) Mixing: preparing the polysaccharide gel into a hot dissolving solution with the mass concentration of 2% by using water, mixing 38g of the organic fiber powder obtained in the step (4) with the hot dissolving solution according to the weight ratio of 1:15 to form a suspension, cooling to room temperature, and forming organic fiber rubber balls under the action of surface tension.

The organic fiber rubber balls collected by the method are subjected to microalgae planting, so that the microalgae grow well on the modified environment-friendly carrier.

Example 3

(1) The raw materials comprise: weighing 100g of corn straw, 40g of juncao and 8g of bagasse, and uniformly mixing to obtain a mixed sample;

(2) unhairing and crushing: filtering the mixed sample by a stainless steel screen mesh with 3 meshes to remove impurities in the mixed sample, drying at 105 ℃ for 1h, taking out, cooling to normal temperature, and crushing and screening by a crusher to finally obtain mixed powder with the particle size of 0.5 mm.

(3) Squeezing and dewatering: putting the mixed powder obtained in the step (2) into a NaOH solution with the volume concentration of 10%, wherein the weight ratio of the mixed powder to the NaOH solution is 1: 18; stirring uniformly by using a glass rod, standing and soaking for 13h to obtain a feed liquid, filtering the feed liquid by using a Buchner funnel, and squeezing to obtain a squeezed material.

(4) Modification treatment: and (4) putting the squeezed material obtained in the step (3) into a glass reaction kettle, pouring 300mL of epoxy chloropropane to completely soak the material, reacting for 7h at 65 ℃ and 200rpm, pouring out liquid, slowly pouring 300mL of trimethylamine to completely soak the material, and reacting for 5h at 75 ℃ and 200 rpm. After the reaction is finished, filtering the squeezed material by using gauze, washing the squeezed material by using a mixed solution of equivalent ethanol and 0.1mol/L hydrochloric acid, finally washing the squeezed material by using ultrapure water to be neutral, and drying the washed material to obtain 131g of modified organic fiber powder.

(5) Mixing: preparing the polysaccharide gel into a hot dissolving solution with the mass concentration of 2.5% by using water, mixing 131g of the organic fiber powder obtained in the step (4) with the hot dissolving solution according to the weight ratio of 1:15 to form a suspension, cooling to room temperature, and forming organic fiber rubber balls under the action of surface tension.

Surface elemental analysis of the mixed sample and the modified organic fiber powder by XPS measurement (results are shown in Table 1), it was found that the ratio of the N element to the Cl element increased after modification, the increase in N was due to the presence of the quaternary ammonium group after modification, and the increase in Cl element was due to the large amount of Cl when the pressed material was washed with HCl solution^-Replaces the original OH on the surface of the adsorbent^-。

FIG. 3(a) shows a mixture of samples andthe Cls orbital spectrum of the modified organic fiber powder, in which the peak at 285eV is related to the C-C/C-H bonds in hydrocarbons, especially methyl and methylene; the peak at 286.5eV is associated with a C-O bond in the carboxyl group or an ether group C-O-C; in addition, in the presence of an amino group, the C-N bond may cause a peak around 286.5 eV. The proportions of C-C/C-H bonds and C-O/C-N/C-O-C bonds in the mixed sample and the modified organic fiber powder reach more than 80 percent, which indicates that the surfaces of the mixed sample and the modified organic fiber powder both use methyl/methylene, hydroxyl or amino as main groups. After modification, the proportion of C-C/C-H bonds decreased from 65% to 35%; whereas the C-O/C-N/C-O-C bonds increased from 25% to nearly 52%. This is due, on the one hand, to the fact that the epoxy cellulose ethers formed during the modification increase the ether and hydroxyl groups on the surface of the material and, on the other hand, to the fact that the proportion of C-N bonds increases during the quaternization of the trimethylamine reaction. FIG. 3(b) is the Nls spectrum of the mixed sample and the modified organic fiber powder, the peak at 400eV is represented by the formula-N (CH)₂/-NH₂The peak around 402.7eV is related to quaternary ammonium group or protonated amino group (-N (CH)₃)₃ ⁺/-NH₃ ⁺) In this connection, it can be seen that the peak area of the quaternary ammonium group increases after modification, again because of the presence of the quaternary ammonium group. This result further demonstrates that the surface element distribution measured by XPS before and after modification can find that the ratio of the N element and the Cl element increases after modification. The increase of N is caused by the existence of quaternary ammonium group after modification, and the increase of Cl element is caused by a large amount of Cl when the modified straws are washed by HCl solution^-Replaces the original OH on the surface of the adsorbent^-。

In conclusion, the main structural skeleton of the modified organic fiber is cellulose, and the main functional groups are quaternary ammonium groups and hydroxyl groups, which indicates that a large amount of quaternary ammonium groups are introduced into the organic slag mixture through modification.

Table 1: composition of surface elements of material before and after modification

Sample (I)	C	O	N	Cl
					Raw organic waste residue mixture	69.4％	28.8％	1.2％	0.3％
Modified organic fiber	72.0％	24.0％	2.9％	0.9％

The organic fiber rubber balls collected by the method are subjected to microalgae planting, so that the microalgae grow well on the modified environment-friendly carrier.