KR0144796B1 - Method for preparing porous polyurethane spherical spheres and their use in wastewater treatment - Google Patents

Abstract

Foamed polyurethane microspheres for the immobilization of microorganisms were polymerized, and the density was generally lower when water and benzene, water and cyclohexane were used as solvents. Such a carrier had excellent foaming power and a large amount after polymerization, and spherical density increased with addition of activated carbon and zeolite during polymerization.

In order to evaluate the performance of the foamed polyurethane microspheres as carriers, comparative experiments were conducted with the sintered porous glass spheres. WA, WCA, and GB showed 79%, 87%, and 88% COD removal after 24 hours in primary culture, but 94%, 99%, and 98% removal after 10 hours in 10 culture. .

Description

Method for preparing porous polyurethane spherical spheres and their use in wastewater treatment

1 is an explanatory view showing a polymerization apparatus of the present invention.

2 and 3 are electron micrographs of microorganisms immobilized on porous polyurethane spheres, spherical carriers and sintered porous glass spheres.

The present invention relates to a method for producing a porous polyurethane sphere and its use in wastewater treatment of a porous polyurethane sphere prepared therefrom.

There has recently been a growing interest in the immobilization of microorganisms and significant progress has been made. Targets for biological advancement include compactness, high efficiency, and energy saving. Among them, researches on silica sand and lightweight aggregates aiming at miniaturization while maintaining the performance of wastewater treatment have been actively conducted. However, such carriers are difficult to attach the microorganisms, and once the microorganisms are attached, they may enlarge or leak over time. So they forced the biofilm off or placed a screen at the exit. In order to compensate for this disadvantage, a relatively large porous carrier is used to immobilize the microorganisms in the carrier and prevent the microorganisms from falling off due to collision between the carriers. One of the carriers used for this purpose is porous polyurethane. Porous polyurethane is chemically and mechanically stable and inexpensive, and researches for using it as a carrier for wastewater treatment have been actively conducted.

Polyurethane has been used for immobilization of cells through encapsulation using a polymer precursor or adsorption using a foam.

In 1975, compared with the activated sludge method in which the activated sludge method and the porous porous carrier made of polyurethane were introduced at the University of Tokyo, the processing performance by the carrier injection was extremely excellent and the emergence microorganisms were more diverse than the activated sludge method. It was.

In the early 1980s, the processes of CAPTOR and LINPOR were developed in the UK and Germany respectively, and these systems used tailored polyurethane carriers.

Masao Kondo of Japan and others confirmed that material selection is an important determinant of long-term stability in the advanced treatment by intermittent aeration method with porous sponge-like carrier. It has been reported that simultaneous removal of BOD and nitrogen is possible using a carrier made of a wear resistant polyurethane having a cell number of 12 × 12 × 12 mm 40 in a system using an FRP tube having a depth of 2 m.

However, the use of conventional porous polyurethane is not only to reduce the size of the carrier, but also to control the pore or density in the carrier arbitrarily because it is manufactured after cutting to a large volume. In addition, since the size of the carrier cannot be reduced, when the microorganism is immobilized in the carrier, there is a disadvantage in that the carrier is anaerobic due to mass transfer resistance, and the carrier is not easily circulated in the reactor due to the low density of the carrier.

Therefore, in the present invention, in order to solve such disadvantages, a porous polyurethane sphere was polymerized using a solvent, and physical properties such as size and foaming degree of macropore according to the type of solvent were investigated. In addition, in order to control the density of the carrier and improve the ability of the microorganism to adhere to the carrier, the presence of activated carbon and zeolite was added during polymerization to examine the ability of the microorganism to adhere. Therefore, according to the present invention, not only can the porous polyurethane be polymerized into the sphere, but also the pore size, pore distribution, density, etc. of the sphere can be arbitrarily controlled. It was examined whether polyurethane particles having such macropores were suitable for immobilization.

Synthesis of porous polyurethane sphere

In order to prepare a porous polyurethane sphere, polyol and diisocyanate were used, and 28 g and 10 g of each were mixed and polymerized. At this time, water and organic solvents such as benzene, toluene, xylene, and cyclohexane were used.

In addition, in order to increase the density of the porous polyurethane sphere and to increase the microbial adhesion and the adsorption of organic matter, 5 g each of activated activated carbon of TEDIA COMPANY, INC and natural zeolites of 50 μm or less were added and polymerized.

1 is a reaction apparatus for synthesizing foamed polyurethane microspherical carrier. The reactor is a spherical reactor, a thermometer installed to penetrate the reactor from the inside to the outside, and driven by the motor of the upper portion of the reactor from the motor to agitate inside the reactor using the driving force generated from the motor The structure includes a stirrer connected to the inside of the reactor, a heater for interviewing the reactor to heat the inside of the reactor, and a condenser connected to the reactor to recover the used organic solvent.

The addition reaction of the porous polyurethane spheres is shown in Table 1. This reaction is exothermic and the reaction rate depends on the structure of isocyanate and polyol, and the blowing agent is contained in the polyol. The blowing agent used in the present invention is a Freon gas and can be replaced with another blowing agent.

After 500 ml of water was added to the reactor, the temperature was maintained at 60 to 80 ° C. Polyol and hexanemethylene diisocyanate are added sequentially and then aged for 10 minutes. In this case, when benzene, toluene, xylene, and cyclohexane are used as the solvent, hexamethylene isocyanate is mixed with the solvent and then introduced into the reactor. In addition, additives for increasing the density of the carrier, activated carbon, zeolite, celite, sand and other additives are added at this time.

As the granular solids, activated carbon (A) and zeolite (Z) are alternatively used, respectively, and the blowing agent is contained in the polyol. In addition, water (W), benzene (B), toluene (T), xylene (X) and cyclonucleic acid (C) were used as solvents, and the synthesized polyurethane of Table 5 was prepared by the following 12 methods. . In order to synthesize porous polyurethane, isocyanate, polyol and water are necessary, and other organic solvents such as benzene (B), toluene (T), xylene (X), cyclonucleic acid (C) and fine solids Phosphorus activated carbon (A) and zeolite (Z) were optionally used.

① isocyanate + polyol + water (W)

② isocyanate + polyol + water (W) + activated carbon (A)

③ isocyanate + polyol + water (W) + zeolite (Z)

④ isocyanate + polyol + water (W) + benzene (B)

⑤ isocyanate + polyol + water (W) + benzene (B) + activated carbon (A)

⑥ isocyanate + polyol + water (W) + benzene (B) + zeolite (Z)

⑦ isocyanate + polyol + water (W) + cyclonucleic acid (C)

⑧ isocyanate + polyol + water (W) + cyclonucleic acid (C) + activated carbon (A)

⑨ Isocyanate + polyol + water (W) + cyclonucleic acid (C) + zeolite (Z)

소 isocyanate + polyol + water (W) + xylene (X)

소 isocyanate + polyol + water (W) + xylene (X) + activated carbon (A)

12 It contains 12 methods of isocyanate + polyol + water (W) + xylene (X) + zeolite (Z).

Control the pore size and pore distribution, density and foaming capacity of foamed polyurethane microspherical carrier according to heating temperature and aging temperature during polymerization, rotation speed of stirrer, addition of fine solids, amount and type of blowing agent, and type of solvent. Can be.

The addition reaction of the porous polyurethane spheres is shown in Table 1.

This reaction is exothermic and the reaction rate is dependent on the structure of isocyanate and polyol, and the blowing agents chlorofluorocarbon, azobisisobutyronitrile and azodica Azodi-carbonamide is contained in polyols.

In order to control the particle size of the microspheres, at first, the stirring speed of the reactor is maintained at 500 to 700 for 1 minute, and as the reaction proceeds, the stirring speed is gradually increased to change the particle size. The temperature of the reactor is initially slowly heated to react for 5 to 10 minutes at 40 to 50 ° C., and the stirring speed is maintained at 500 to 700 for 1 minute. The temperature is raised to 65 to 75 ℃ to react for 5 to 10 minutes, at this time to adjust the size of the fine spherical particles according to the speed of the stirrer. At this time, when the stirring speed of 1 minute was set to 2000, the particle size was 200 to 500 μm, and when the stirring speed of 1 minute was set to 1500, particles in the range of 400 to 900 μm were obtained. The temperature of the reactor is maintained at 100 ° C. in order to volatilize all the solvents that inhibit the growth of microorganisms.

Example 1

Physical and chemical properties and foaming

The bulk and wet densities were measured by measuring the size of 425 to 850 ㎛ as a standard for the polymerized spheres using the respective solvents, and the surface roughness and pore size distribution were determined by electron micrograph. Foaming was investigated.

Table 2 shows the physical properties of each sphere polymerized with each solvent. Surface roughness, which is important for microbial adhesion, was measured as a relative value.

Solvent: W: Water, WA: Water + Activated Carbon, WZ: Water + Zeolite, WB: Water + Benzene,

WBA: water + benzene + activated carbon, WCA: water + benzene + zeolite,

WC: water + cyclohexane, WCA: water + cyclohexane + activated carbon,

WX: Water + Xylene, WXA: Water + Xylene + Activated Carbon, WXZ: Water + Xylene + Zeolite

The bulk density was relatively high when water alone or water and xylene were used as the solvent, compared to the use of other solvents, which means that the foaming state was not good. When water and benzene, water and cyclohexane were used, the values were generally low, and the amount of total sphere after polymerization was the highest. In addition, both the volume and the wet density of the spheres increased with the addition of activated carbon and zeolite during polymerization.

2, A, B, and C show electron micrographs of spheres using water, cyclohexane, water and xylene as a solvent.

The pore size of the spheres for each solvent was less than 8 ㎛ and evenly distributed on the plane for each pore size for water, but for other solvents, the plane was uneven. Surface roughness was observed by electron micrographs, and the cyclohexane was generally excellent, and water, cyclohexane, and zeolite were the best.

Example 2

Microorganism Adhesion and Removal Efficiency

For the immobilization experiment, microorganisms were used in Pseudomonas genus, which is an ethyleneglycol degrading bacterium isolated by the present inventors, and the medium is shown in Table 3.

Pollen cultivation was carried out to measure the adhesion of ethylene glycol degrading bacteria to the porous polyurethane and the degree of ethylene glycol degradation according to adhesion. When the identified ethylene glycol degrading bacteria were previously incubated, 7 mL of this culture medium and 93 mL of synthetic wastewater using only ethylene glycol as a carbon source were added to each Erlenmeyer flask, and 20 ml of the carrier was added thereto to remove 80% of the concentration from the shaker. Incubated until. At this time, the culture solution was completely discarded, and 100 mL of fresh medium (Table 3) was added thereto and cultured again. This operation was repeated several times, and as the recovery of the batch culture increased, the amount of microorganisms attached to the carrier increased, and thus the increase in ethylene glycol degradation rate was investigated.

The shake incubator was rotatable and maintained at a temperature of 35 [deg.] C., pH 7.5 and a 1 minute rotational speed of 180. The concentration of ethylene glycol was quantified by indirect method by measuring COD.

Table 4 shows the concentration of COD according to the change of time in the first batch culture. When activated carbon and zeolite were added at the time of polymerization, a significant amount of COD was removed at the beginning of the culture having excellent adsorption capacity, and activated carbon had better adsorption capacity than zeolite. After 24 hours for W and WA and WZ when water was used as the solvent, COD was 534mg / L, 845mg / L and 480mg / L, respectively, 87%, 79% and 88%. A removal rate of% is shown. In addition, when water and cyclohexane were used as the solvent, and activated carbon and zeolite were added, the COD was 2027 mg / L, 527 mg / L, and 2573 mg / L after 24 hours, showing removal rates of 48%, 49%, and 87%, respectively. When activated carbon was added, the COD removal efficiency was excellent, and when the water was added as a solvent, the efficiency was lowered except for the addition of activated carbon than when other organic solvents were added together. The reason for this is that the organic solvent inhibits the growth of microorganisms. As the culture order increases, the inhibitory effect of the organic solvent decreases, and the carrier having excellent foamability with more specific surface area to which microorganisms can adhere and remove COD is removed. It is considered that the efficiency is excellent.

3, A, B, C, D, E, and F show electron micrographs of each carrier to which microorganisms are attached after the 10th culture. A microbial film is formed on the surface of each carrier.

Table 5 shows the concentration of COD according to the change of time in the 10th batch culture. It can be seen that the decomposition time of ethylene glycol was significantly reduced by the increase of adherent microorganisms. Water and benzene and water and cyclohexane were the best removal efficiencies. Solvent was used only when water was used, and COD removal was lower than that of other organic solvents due to insufficient foamability. As a result, addition of an organic solvent is required in preparing a porous polyurethane, and the used organic solvent can be recovered by attaching a condenser.

Example 3

Performance Comparison

In order to compare the adhesion of microorganisms with other conventional microorganisms and microbial resolution, a comparative experiment was performed using Schinter's sintered porous glass. Scott's porous sintered glass has a size of 0.4 to 1 mm, a bulk density of 0.6 g / mL, and a surface area of 90 m 2 / g m 2 / L.

The culture conditions were the same as above, and the removal efficiency of organic matter according to the change of time in the first and the tenth culture was shown in Tables 4 and 5. Electron micrographs of the glass spheres in which the microorganisms were immobilized after the 10th culture are shown in FIG. 4.

The glass spheres are much larger in pore size than the porous polyurethane spheres, and micropores are not formed in the large pores. In addition, both the porous polyurethane sphere and the sintered porous glass sphere significantly shortened the decomposition time of organic matter with the increase of the culture order, which is due to the increase of the microorganisms immobilized on the carrier. WA, WCA, and GB showed 79%, 87%, and 88% removal rates after 24 hr in the primary culture, but 94%, 99%, and 98% removal after 18 hr in the 10th culture.

Therefore, porous polyurethane spheres polymerized using solvent have excellent performance as carriers for wastewater treatment and are considered to be very economical carriers compared to sintered porous glass spheres.

Claims (4)

In the method for producing a porous polyurethane sphere, a first step of introducing water into the reactor, a second step of maintaining the temperature of the reactor at 60 ℃ to 80 ℃ after the first process, and water, benzene, toluene as a solvent , A third step of sequentially introducing polyol and diisocyanate into the reactor using xylene and cyclonucleic acid, and a fourth step of aging for 10 minutes after the addition. Way. In the porous polyurethane spherical manufacturing apparatus, the inside of the reactor is stirred using a spherical reactor, a thermometer installed through the reactor from the inside to the outside, and a driving force generated from the motor driven by a motor on the upper portion of the reactor. Porous polyurethane production comprising a stirrer connected to the inside of the reactor from the motor to function, a heater for heating the inside of the reactor interviewed with the reactor, and a condenser for recovering the organic solvent used in connection with the reactor Device. The method of claim 1, wherein benzene, toluene, xylene and cyclonucleic acid are used as a solvent during the aging process, and activated carbon, zeolite celite, and sand are added as additives to increase carrier density. The method for preparing a porous polyurethane sphere according to claim 1, which is controlled using a blowing agent, chlorofluorocarbon, azobisisobutyronitrile and azodicarbonamide, in order to control the pore distribution and pore size of the microspheres.