CN108249534B

CN108249534B - Flocculating agent for rapidly treating high-density algae water body

Info

Publication number: CN108249534B
Application number: CN201810140710.2A
Authority: CN
Inventors: 安振华
Original assignee: Yangzhou University
Current assignee: Yangzhou University
Priority date: 2018-02-11
Filing date: 2018-02-11
Publication date: 2020-05-05
Anticipated expiration: 2038-02-11
Also published as: CN108249534A

Abstract

The invention discloses a flocculating agent for rapidly treating a high-density algae water body, which is a chitosan modified tourmaline composite bentonite flocculating agent, and the components of the flocculating agent are polymerized by black iron-magnesium tourmaline, calcium bentonite and chitosan, wherein the mass ratio of the components is 7: 10: 1. the organic-inorganic composite flocculant prepared by fully utilizing the cation providing capacity of chitosan, the adsorbability of calcium bentonite and the ionization characteristic of iron-magnesium tourmaline structurally contains a cation group and a hydrophobic group at the same time, and can stabilize the pH value of a water body, so that the organic-inorganic composite flocculant has stronger adsorption bridging and electric neutralization performances and has better treatment effect on waste water containing more algae. The invention is mainly used for water quality treatment of algae outbreak in aquaculture, and can also be used for drinking water treatment, ornamental fish culture, garden water treatment and other directions. By adjusting the proportion of the three components, the density and the flocculation speed of the flocculant can be controlled, and the flocculant has good popularization value and economic and social benefits.

Description

Flocculating agent for rapidly treating high-density algae water body

Technical Field

The invention relates to a flocculating agent, and belongs to the technical field of sewage treatment.

Background

In the aquaculture area of China, large algae blooms are often seen in summer with high water temperature due to high culture density and large bait feeding amount, the density of algae in a water body is high, the water color is dark green, and the transparency is much lower than 25 cm. Although the algae are the most important source of the dissolved oxygen in the aquaculture water body, more than 70% of the dissolved oxygen in the water body is from the photosynthesis of the algae, more than 80% of the dissolved oxygen in the water body is finally consumed by the algae every day, and the more the algae are, the higher the risk is particularly at night. When the density of the algae is too high, the algae is gathered on the surface layer of water, so that light can be prevented from penetrating through the water body, photosynthesis oxygenation is limited to the shallow surface layer, and the oxygen yield of the whole water body is reduced. The massive growth of algae poses a great hazard to the organisms cultured in ponds, so the control and rapid reduction of the density of algae is a difficult point of pond aquaculture.

The density of the algae in the culture pond is quickly reduced, and the most direct mode except water changing is to utilize a flocculating agent to flocculate algae. The existing flocculating agents are various in types and mainly comprise inorganic flocculating agents, organic flocculating agents and composite flocculating agents (including organic composite flocculating agents, inorganic polymer composite flocculating agents and organic-inorganic composite flocculating agents). The method is widely applied to industrial and domestic sewage treatment, but has certain disadvantages in agricultural cultivation water treatment:

(1) inorganic flocculant or composite flocculant containing inorganic matter contains aluminum salt or ferric salt generally, and aluminum ions have obvious toxicity to aquaculture organisms in aquatic product production. Research shows that when the concentration of aluminum ions in water is higher than 0.5 mg/L, salmon can be killed; even precipitated aluminum hydroxide causes chronic poisoning of salmon; at a pH of about 5, elemental aluminum deposits in the gill as alumina, which prevents oxygen from entering the blood and causes the salinity in the fish to become imbalanced, leading to fish death. The increase of the aluminum concentration in water causes the precipitation of soluble phosphorus in water body, reduces the remineralization rate of phosphorus and brings great threat to the life of aquatic animals (AWWA, 1978; Fuyulong, 2000). The aluminum salt also has animal embryo toxicity and teratogenicity, and prevents reproduction of river bottom microorganism and fish and shellfish.

The low-molecular inorganic flocculant has slow flocculation and precipitation speed, and the slower the speed, the more easily the breathing capacity of the fish and the shrimp is damaged. For example, besides the problem that ferric salt flocculant is easy to generate water color deepening after treating water body, the following researches show that: ferric sulphate reagent was observed in lethal and sublethal experiments as the precipitation of iron-containing flocs on the epithelial cells of gills, leading to blockage and damage of gills (Appel et al, 2001). Sludge obtained after treatment of sewage with ferric chloride as a flocculant has chronic toxicity to daphnia magna, which can cause decreased egg laying rate and increased mortality (Sotero-Santos et al, 2005).

(2) The most widely used in the synthesis of organic polymeric flocculants is Polyacrylamide (PAM). In China, polyacrylamide is also the most widely used polymer flocculant in water treatment, accounting for 50% of the municipal water supply and drainage amount, and is currently used for sewage treatment in large quantities, but researches show that cationic polyacrylamide reacts with anionic mucus secreted by fishes in natural water, and reactants adhere to the surfaces of gills to cause the fishes to lose the oxygen absorption capacity, thereby causing the death of the fishes (Takigami et al, 1998).

(3) The natural high molecular organic flocculant has rich material source, low cost, high selectivity, safety, no toxicity, complete biodegradation, no secondary pollution, low and unstable molecular weight, high use amount, poor effect, BOD and other problems. The organic flocculant treatment process is greatly influenced by the pH value of the sewage, and a reagent is required to be added to adjust the pH value of the sewage in practical application, so that the number of processes and equipment is increased, and the treatment process is increased. A large amount of organic matters are left in the discharged water after being treated by part of organic flocculants, and if the discharged water cannot be utilized by aquatic organisms, new pollution is easily formed, and the self-cleaning capacity of natural water is influenced.

Disclosure of Invention

In combination with the current situation, for the problem of algae outbreak in the aquaculture pond, the method needs to rapidly flocculate and precipitate the algae, and also needs to ensure that the flocculant is safe to aquaculture organisms and environment-friendly, and a natural organic-inorganic high molecular weight composite flocculant which is natural and harmless in inorganic components and safe and utilizable in organic components is a feasible solution. The present invention has thus been made.

The invention aims to solve the defects of the prior art and provide a flocculating agent for rapidly treating high-density algae water.

In order to solve the technical problems, the invention provides the following technical scheme:

the flocculating agent for rapidly treating the high-density algae water body is prepared by polymerizing black iron-magnesium tourmaline, calcium bentonite and chitosan, wherein the mass ratio of the components is 7: 10: 1;

preferably, the chitosan has deacetylation degree of more than 85%, and is white or light yellow semi-transparent solid with slightly pearl luster.

The amino group in the chitosan molecule is combined with proton to make the chitosan self-positively charged, and the chitosan molecule is a rare high molecular substance with positive charge in natural polysaccharide. The chitosan is derived from chitin shells of crustaceans, is natural and harmless, has good chemical stability and strong hygroscopicity, and is easily decomposed when meeting water; the chitosan has excellent biocompatibility, can be dissolved by lysozyme and the like, can be biodegraded, has nontoxic metabolites, and can be completely absorbed by organisms.

As a preferred proposal, the tourmaline is preferably Xinjiang black iron magnesium tourmaline which is used for preparing tourmaline powderThe number is preferably 1500 meshes, and the density is 3.03-3.25g/cm³The powder is gray black.

The spontaneous electric pole of the tourmaline is a permanent electrode, the spontaneous polarization value of the tourmaline is a value independent of temperature, and the high field intensity of 104-107V/m exists only in the range of tens of microns of the surface thickness of the tourmaline. The electric field effect is represented by the electrolysis action on water molecules on one hand and the adsorption and neutralization action of an electrostatic field on charged particles in the water molecules on the other hand. The tourmaline passes through the high-strength electrostatic field H on the surface of the tourmaline⁺And OH^-Ions are adsorbed to both poles of tourmaline, H⁺Has a migration velocity of OH^-Twice of the amount of the hydrogen peroxide, thereby adjusting the pH value of the aqueous solution to rise and excessive H⁺Is released in the form of hydrogen. Along with the surface H of the tourmaline⁺Reduction of ions, under concentration difference, of distant H⁺Continuously moving towards the surface of the tourmaline until reaching the balance.

Preferably, the bentonite is calcium bentonite, and the density of the bentonite is 2-3g/cm³The appearance is loose soil, the soil is smooth when rubbed by fingers, the small blocks swell by a plurality of times to 20-30 times after being added with water, the small blocks are suspended in water, and the powder is white in appearance.

The invention also provides a preparation method of the flocculant for rapidly treating the high-density algae water body, which comprises the following steps:

(1) taking 1500-mesh black tourmaline, distilled water and silica sol, wherein the weight ratio of the black tourmaline to the distilled water to the silica sol is 7: 1: 2, fully and uniformly stirring, then uniformly mixing with calcium bentonite with equal mass, and uniformly brushing the mixture on the surface of a ceramic flat plate by using a small brush, wherein the thickness is about 1mm on average (silica sol is favorable for the adhesion of tourmaline and bentonite, and is equivalent to a binder for integrating the components of the tourmaline and the bentonite through high-temperature sintering); the ceramic flat plate is placed at the temperature of 250-300 ℃ and is fired for 15 minutes, tourmaline powder and bentonite are sintered on the surface of the flat plate to form a film, and the film is clamped out and cooled by a dry pot clamp.

(2) Shoveling the tourmaline and bentonite sintered film on the surface of the ceramic flat plate, putting the ceramic flat plate into a crusher with the rotating speed of more than 1000 revolutions per second, crushing the ceramic flat plate, and screening the crushed ceramic flat plate for later use.

(3) Preparing chitosan and a 1% acetic acid solution, wherein the mass ratio of the chitosan to the 1% acetic acid solution is 1: 99, fully dissolving the chitosan in the acetic acid solution under the stirring of a magnetic stirrer to prepare the chitosan acetic acid solution.

(4) Measuring 100 mL of chitosan solution, adding 20g of tourmaline-bentonite powder under stirring of a magnetic stirrer, dropwise adding dilute hydrochloric acid to adjust the pH value to be 2.0-3.0, uniformly mixing, standing for 2 hours, and then heating to 60 ℃. The bentonite in the structure of the flocculating agent absorbs water and swells to form a flocculating agent composite copolymerization colloid with the content of 0.2 g/mL.

The results show that: the optimal composite conditions are that the pH value is 2.0-3.0, the tourmaline-bentonite powder: chitosan acetic acid solution (mass ratio) = 1: 5, and the mass ratio of tourmaline, bentonite and chitosan in the flocculant powder = 7: 10: 1; the optimal temperature for mixing to form the copolymer colloid is 60-70 ℃, and the reaction time is more than 16 hours.

And (3) drying the flocculant composite copolymerization colloid at 60 ℃, putting the dried flocculant composite copolymerization colloid into a crusher with the rotating speed of more than 1000 revolutions per second for crushing, and screening by a 600-mesh screen (the particle size is less than 25 um) to obtain the finished product powder.

The organic-inorganic composite flocculant with high molecular weight and excellent flocculation performance prepared by the invention utilizes chitosan and tourmaline powder to modify bentonite, so that the bentonite structurally contains cationic groups and hydrophobic groups at the same time, and therefore, the organic-inorganic composite flocculant has stronger adsorption bridging and electric neutralization performances and has better treatment effect on wastewater containing more algae.

The flocculant prepared by the method has the advantages compared with the prior conditions and the problems to be solved:

(1) algae cells (especially blue algae) often contain tiny bubbles, have low specific gravity, and a low molecular weight flocculating agent cannot rapidly settle the algae. The flocculating agent ensures that the flocs are not easy to adhere to the surfaces of fish and shrimp branchia filaments so as to prevent the fish and shrimp from losing the capability of absorbing oxygen. This requires that the flocculant be structured to have both a large surface area (more algae adsorbed) and a certain density to ensure rapid settling.

(2) During the growth process of algae, an acidic polysaccharide organic substance is released to the outside of cells, and an organic colloidal layer is formed outside the cells, so that the surfaces of the algae are electronegative, and the efficient flocculant needs to have both cationic groups (ensuring efficient adsorption of algae cells) and a small amount of hydrophobic groups (ensuring rapid dispersion in water), so that the efficient flocculant has a good treatment effect in treatment of the culture water rich in algae.

(3) The flocculation effect of common organic flocculants is greatly influenced by the pH value of a water body, and a reagent is required to be added to adjust the pH value of the water body in practical application, so that the number of processes and equipment is increased, and the treatment process and the treatment time are increased; if the flocculant has the capability of adjusting the pH value of the water body (mainly ensuring that the pH value of the water body is weak and alkaline), the treatment effect is more stable, and the operation is simpler.

The beneficial effects produced by the invention can be divided into two types:

(1) the flocculant prepared according to the invention has obvious effect of removing algae, is effective to the algae, the components of tourmaline and bentonite are natural non-toxic mineral substances, chitosan is originated from crustacean, the use does not pollute the environment, and the flocculant has small irritation and no toxicity to the cultured organisms. In the past, the sewage containing algae mostly adopts inorganic chemical oxidants, and the traditional algicide easily releases part of algal toxins contained in algae into water, thereby causing secondary pollution. The flocculant prepared by the invention mainly adsorbs algae, does not basically crack algae cells, the algae are wrapped and quickly settled to the water bottom to be covered with the flocculant, and the intracellular algal toxins are gradually degraded under the anoxic condition and are not released into the water body.

(2) The chitosan, the tourmaline and the bentonite are combined for use, and the generated synergistic effect is far greater than the flocculation effect of the chitosan or the bentonite which is used alone. The tourmaline has the effect of stabilizing the pH value of the water body, the adsorption effect of the bentonite can ensure that the growth speed of algae is greatly reduced after flocculation, and the tourmaline has the effect of controlling the algae for a long time.

Drawings

FIG. 1 is a schematic representation of the combination of three components.

FIG. 2 is a schematic diagram of adsorption of algae by a polymeric flocculant.

FIG. 3 is a schematic diagram of the adsorption of algae by the chitosan modified tourmaline composite bentonite flocculant of the present invention.

FIG. 4 XRD analysis diagram of black iron magnesium tourmaline

Detailed Description

The manufacturing and implementation difficulty of the preparation method is mainly concentrated in the preparation of the powder of the flocculating agent, and the key steps comprise the following points:

1. material selection

The varieties of the tourmaline are more, the worth of the tourmaline for adjusting the pH value of the water body are different, the tourmaline powder is suitable for selecting black tourmaline in Xinjiang area, the crushing granularity reaches more than 1000 meshes, and the tourmaline powder needs to be screened for later use.

FIG. 4 is XRD analysis diagram of tourmaline containing iron-magnesium tourmaline as main component and small amount of SiO₂Impurities. The tourmaline is columnar and granular, the median variation range of 1000 mesh tourmaline particle size is 10-30um, and the particle size is 15-25um and accounts for 80% of the total particle number.

The chemical analysis result of the black iron-magnesium tourmaline micropowder is as follows (%)₂46.03，Al₂O₃16.71，B₂O₃10.24，FeO 0.92，Fe₂O₃18.24，TiO₂0.45，Na₂O 1.12，K₂O 0.06，MgO 2.28，CaO 3.95。

The tourmaline has a complex chemical general formula of NaR3Al6[ Si6O18] [ BO3]3(OH, F)4, wherein R represents metal cations, and when R is Mg2+, Fe2+ or (Li + + Al3 +), the tourmaline, the schorlite and the lithium tourmaline respectively form three mineral species.

2. The preparation method of the flocculant comprises the following steps:

(1) taking black iron-magnesium tourmaline, distilled water and silica sol according to the weight ratio of 7: 1: 2, fully stirring uniformly, then uniformly mixing with calcium bentonite with equal mass, and uniformly brushing the mixture on the surface of a ceramic flat plate by using a small brush, wherein the thickness is about 1mm on average; placing the ceramic flat plate at the temperature of 250-300 ℃, firing for 15 minutes, sintering tourmaline powder and bentonite on the surface of the flat plate to form a film, clamping the film by a dry pot and cooling;

(2) shoveling the tourmaline and bentonite sintered film on the surface of the ceramic flat plate, putting the ceramic flat plate into a rotating speed crusher for crushing, and screening for later use;

(3) fully dissolving chitosan in an acetic acid solution to prepare a chitosan acetic acid solution;

(4) and (3) adding the chitosan acetic acid solution prepared in the step (3) into the tourmaline-bentonite powder prepared in the step (2) under the stirring of a magnetic stirrer, dropwise adding dilute hydrochloric acid to adjust the pH value to be 2.0-3.0, uniformly mixing, standing for 2 hours, and then heating to 60-70 ℃ for reaction to prepare the flocculant composite copolymer colloid.

In the process of firing the tourmaline and the bentonite by combining silica sol, the firing temperature is controlled to be not higher than 350 ℃, the temperature is too high, the black tourmaline powder is denatured, the color is changed from black to ochre yellow, and the thermoelectric effect is lost, so that the expected effect cannot be achieved. The proportion of the tourmaline powder and the adhesive-silica sol is slightly different due to the difference of the quality of the tourmaline raw material and the silica sol, and can be properly changed on the basis of the proportion of the tourmaline powder and the adhesive-silica sol.

3. In practical application, the culture water body has large algae content difference, algae body specific gravity is also different according to species, organic matters are numerous, flocculation conditions are complex, the flocculation speed is very high when the method is usually applied to a pond A, and flocculation is difficult to occur in a pond B for a long time. Therefore, the specific gravity of the flocculating agent can be adjusted by adjusting the proportion of the tourmaline powder and the bentonite in the components aiming at different areas in the actual use process. The higher the density of the algae, the more difficult the sedimentation, the higher the density of the flocculant is required, and the proportion of tourmaline powder can be increased appropriately.

The novel flocculant prepared by the application is mainly used for water bodies with severe eutrophication algae outbreaks in aquaculture industry; especially for the treatment of pond culture water with high turbidity and rich nutrient organic matter content, and can also be used for drinking water treatment, ornamental fish culture, garden water treatment and other directions. Has good popularization value and economic and social benefits.

Claims

1. Flocculant for rapidly treating high-density algae water bodyCharacterized in that the flocculant is a chitosan modified tourmaline composite bentonite flocculant which is polymerized by black iron-magnesium tourmaline, calcium bentonite and chitosan, and the mass ratio of the flocculant to the calcium bentonite is 7: 10: 1, wherein the chitosan requires a degree of deacetylation>85 percent, the mesh number of the prepared tourmaline powder is 1000-1500 meshes, and the density of the calcium bentonite is 2-3g/cm³The preparation method specifically comprises the following steps:

(1) taking black iron-magnesium tourmaline, distilled water and silica sol according to the weight ratio of 7: 1: 2, fully stirring uniformly, then uniformly mixing with calcium bentonite with equal mass, and uniformly brushing the mixture on the surface of a ceramic flat plate by using a small brush, wherein the thickness is about 1mm on average; placing the ceramic flat plate at the temperature of 250-300 ℃, firing for 15 minutes, sintering tourmaline powder and bentonite on the surface of the flat plate to form a film, clamping the film by a dry pan and cooling;

2. The flocculant of claim 1, wherein the chitosan is white or yellowish translucent solid in appearance, and has a slightly pearl luster.

3. The flocculant of claim 1, wherein the tourmaline is Xinjiang black iron magnesium tourmaline with a density of 3.03-3.25g/cm³The powder is gray black.

4. The flocculant of claim 1, wherein the calcium bentonite is loose and smooth in appearance when rubbed with fingers, and the small blocks swell by several times to 20-30 times after being added with water, are suspended in water, and are white in powder appearance.