KR0122753B1 - Method of heavy metal absorbent from microorganism culture - Google Patents

Abstract

Absorbent for heavy metals is manufactured by fixing biopolymer extracted from microbial culture broth to sodium alginate and odium metasilicate. Sodium metasilicate is added to optimum culture broth of Zoogloea ramigera at the concentration of 10 g/l. with stirring at 40 C for 1 hr. 2% Sodium alginate is added to above mixture at the ratio of 1:1 and stirred for 10 min. Then saturated solution of calcium chloride is droped to the mixture with stirring to give the bead type of absorbent with the constant size. absorbent obtained can be used for the treatment of heavy metals in waste water, underground water, soil and wastes.

Description

Method for preparing heavy metal adsorbent with microbial culture

The present invention relates to a method for producing a heavy metal adsorbent immobilized using a culture solution of Zugria ramizera and a biopolymer sodium metasilicate and sodium alginate extracted therefrom.

The present invention relates to a heavy metal adsorbent obtained by optimally cultivating Zoogloea ramigera and immobilizing the culture medium and the biopolymers extracted therein using sodium metasilicate and sodium alginate, and a method for preparing the same.

In each country, research on the removal and recovery of metals from wastewater, groundwater, soil, or wastes has not only increased the value of metals as oil resources but also increased concern about the ecological effects of toxic metals released into the natural environment. Is being actively performed.

Conventional methods of treating heavy metal wastewater include oxidation / reduction method, flocculation sedimentation method, adsorption, ion exchange method, electrolysis method, neutralization method, extraction method, etc. The flocculation sedimentation method and ion exchange resin method are most commonly used. These processes have the disadvantage of being inefficient or very expensive, especially when the solution contains 1-100 mg / L of metal (Water Treatment Principles and Design, John Wiley and Sons, 1985). It has the advantages of being the most commonly used method because of the easy and maintenance costs and relatively low energy consumption, but has a big problem, such as sludge treatment is a low heavy metal removal rate and a large amount of chemical coagulant is used. The ion exchange resin method has the advantage of higher removal rate and selective removal of heavy metal ions compared to the precipitation method. However, since expensive resin must be used, the recovery and reuse of metals are not performed in comparison with other treatment methods. It can be called economic.

Zugria lamize, a major cohesive microorganism that naturally lives in activated sludge, produces polysaccharides from several carbon and nitrogen sources. The produced polysaccharides affect the sludge properties such as cell aggregation and heavy metal adsorption capacity, and play a major role in the sludge separation and ultimately reducing the biological oxygen demand (BOD) in the wastewater.

The present inventors have conducted extensive research on the method of mass-producing polysaccharides, which are used as biopolymers in wastewater treatment, through the pure culture of Zugria ramizera. The patent application (No. 92-638) was completed by completing an invention relating to an optimum culture condition and a medium composition for producing biopolymers and a method for producing biopolymers using the same. Subsequently, studies on the adsorption performance of heavy metals of the Zugria ramizera culture medium and the biopolymers extracted therefrom were continued, and it was found that the culture medium and the biopolymers extracted therefrom exhibited excellent heavy metal adsorption performance. However, in the heavy metal adsorption process, using the original biosorbent without immobilization has several difficulties in practical terms. In other words, dry microorganisms, fine powders or granules or lumps are easily swelled when wet, and are difficult to handle, such as being broken. Therefore, these materials are suitable carriers having a certain hardness in order to be applied to an actual process. It should be fixed by using. Known immobilization methods include acrylamide as a carrier, polyvinyl alcohol and boric acid, sodium alginate, and the like. However, the beads made by these methods have disadvantages such as swelling and breaking of beads during long-term operation, which is not suitable for long-term operation. The present invention has been made to solve the above-mentioned drawbacks, and invents a method of immobilizing the culture medium and the extracted biopolymer onto the carrier using a suitable carrier having the characteristics of an effective heavy metal adsorbent. Through experiments of adsorption, an excellent method for preparing a heavy metal adsorbent was invented.

An object of the present invention is to provide a heavy metal adsorbent in which the optimal culture of the Zugria ramizera is extracted and the biopolymers are extracted and the extracted biopolymers are immobilized. Other objects and advantages of the present invention are apparent from the following detailed description of the present invention. The present inventors have optimally cultured Zugria ramizera to extract the biopolymers and to investigate the adsorption characteristics of the extracted biopolymers in the culture medium, dry cells and unextracted biopolymers, activated sludge, alcoholic wastewater, anaerobic granular sludge. As a result of the heavy metal adsorption experiment by selecting as an adsorbent, it was found that the culturing of Zugria ramizera culture and dried cells, unextracted biopolymers and extracted biopolymers showed better heavy metal adsorption performance than other materials selected as adsorbents. The present invention was completed by confirming that the immobilized culture medium and the biopolymers stably and effectively adsorb heavy metals even in continuous heavy metal adsorption, desorption and resorption experiments. .

The present invention relates to a method for producing a heavy metal adsorbent in which a culture solution of Zugria ramizera and a biopolymer extracted therefrom are immobilized using sodium metasilicate and sodium alginate.

The immobilization method according to the present invention immobilizes the culture medium and the biopolymers of Zugria ramizera to obtain a stable hardness which is harder than the immobilization using only sodium alginate, which is a conventional general immobilization method. Even if the adsorption, desorption and resorption experiments are carried out, the function of the adsorbent having a stable adsorption performance without changing the shape can be performed.

Hereinafter, the present invention will be described in more detail with reference to Examples. In the following example, a representative floc producing bacterium Juglia Ramizera 115 (ATCC 25935) was purchased from the US ATCC and used for storage of this strain, and arginine medium was used. The composition of the medium is as follows. Arginine Hydrochloride 0.5g / L, Alanine 1.0g / L, Magnesium Sulfate Heptahydrate 0.2g / L, Dipotassium Hydrogen Phosphate 2.0g / L, Potassium Dihydrogen Phosphate 0.5g / L, Glucose 25g / L, Vitamin B ₁₂ 1.5 ^10-6 g / L (see Applied Microbiology, 1971).

Example 1

Adsorption Characteristics of Zugria Ramizera Culture and Extracted Biopolymers

In order to optimize the culturing of Zugria ramizera and extract biopolymers from them, to investigate the adsorption characteristics of the extracted biopolymers, the culture medium, dry cells and unextracted biopolymers, extracted biopolymers, activated sludge, alcoholic wastewater, anaerobic Granular sludge was selected as an adsorbent and heavy metal adsorption experiments were performed. When the cadmium artificial wastewater was used as a sample, the adsorption equilibrium of each adsorbent was performed between 1 hour and 1 hour and 20 minutes under the conditions of pH 7, temperature 25 ° C. The adsorption test results of each adsorbent under the above test conditions are as follows. Adsorption amount of fermenter broth adsorbed 200 milligrams of cadmium per gram, dry cells and unextracted biopolymers were 170, extracted biopolymers were 140, anaerobic granular sludge was 80, alcoholic wastewater was 60 and activated sludge was 40 milligrams. Cadmium was adsorbed. As a result, the fermenter culture broth containing biopolymer showed 5 times adsorption capacity compared to activated sludge known to have heavy metal adsorption capacity.

Example 2

Preparation of Heavy Metal Adsorbents by Immobilization of Zugria Ramizera Culture and Extracted Biopolymers

After optimal cultivation of Zugria ramizera, 10 grams of sodium metasilicate per liter of the culture medium was added and vigorously stirred for 1 hour while maintaining the temperature at 40 ° C. The microbial cells and biopolymers in the culture medium were mixed with sodium metasilicate. The viscosity of the solution itself sharply increases while forming a lattice. 2% sodium alginate solution is mixed in a 1: 1 ratio to the solution with increased viscosity, followed by vigorous stirring for 10 minutes. When the mixed solution is agitated while falling to a saturated solution of calcium chloride at a fixed rate using an immobilization device, beads of a certain size, which are heavy metal adsorbents of the present invention, are formed. Such bead particles are formed because the substitution between sodium methsilicate in the mixed liquid and sodium ions of sodium alginate and calcium ions of calcium chloride is performed. The immobilized beads themselves are based on a lattice of calcium metasilicate and calcium alginate, and microbial cells and biopolymers are stably trapped therein. Such a structure was confirmed through a scanning electron microscope.

Example 3

Adsorption Characteristics of Heavy Metals in Immobilized Zugria Lamigera Cultures

Adsorption isotherms were prepared to examine the adsorption performance of each heavy metal of the adsorbent prepared in Example 2. The tested heavy metals were Cd, Cr, Cu, Mn, and Zn. The heavy metal concentration range was up to 6400 ppm, and valuable metals were tested with Au and Ag. Experimental results For the adsorbent prepared in Example 2, Cd 480 mg / g, Cu 360.4 mg / g, Zn 140.8 mg / g, Mn 115 mg / g, Cr 26.6 mg / g, Ag 45.5 mg / g, Au 9.8 mg Maximum adsorption performance was shown in the order of / g. As a comparative experiment, heavy metal adsorption experiment of CR20 (trade name), which is a commercially available ion exchange resin, was also performed. As a result, Cd 40 mg / g, Mn 107 mg / g, Zn 140 mg / g, Cu 600 mg / g Adsorption performance was shown. Comparing the above results, it can be seen that in the case of Cd, the adsorbent prepared in Example 2 showed better adsorption capacity than the ion exchange resin, and in the case of Cu, the ion exchange resin had better adsorption capacity, and Mn and Zn showed similar adsorption performance. In addition, adsorption experiments for Cu in the presence of Ca and Mg were carried out to consider adsorption of heavy metals in groundwater. In the case of the adsorbent prepared in Example 2, only Ca and Mg were selectively adsorbed without adsorption, whereas SKIB, a commercially available ion exchange resin, significantly reduced the adsorption performance to Cu due to Ca and Mg. And Ca was also adsorbed in large quantities. From the above results, it can be seen that the use of a plate adsorbent in Example 2 is suitable for the selective adsorption of heavy metals contained in groundwater and the like.

Example 4

Adsorption Experiment of Packed Reactor with Immobilized Zugria Ramizera Culture

For continuous heavy metal adsorption experiment of the adsorbent of the present invention, a packed column was packed with the adsorbent prepared in Example 2 to carry out continuous adsorption experiments on Cr, Zn, Mn, Cu, Cd heavy metals. As a comparative experiment, CR20 resin, which is a commercial ion exchange resin, was also packed into a packed column, and adsorption experiment was carried out on the heavy metals. The concentration of the heavy metals was 100 ppm and the residence time in the packed column was 30 minutes. Experimental results In the case of the adsorbent prepared in Example 2, the breakthrough of heavy metals appeared in the order of Cr, Mn, Zn, Cd, Cu, and the adsorption amount of heavy metals at the breakthrough point was 0.4 g of Cr, Cu showed the best adsorption performance with Mn 2.03g, Zn 2.52g, Cd 3.21g and Cu 5.44g. In the case of CR20, the amount of heavy metal adsorption at breakthrough was found to be Mn 03.g, Zn 0.42g, Cd 0.43g, and Cu 4.2g. From the above results it can be seen that the heavy metal adsorption capacity of the adsorbent prepared in Example 2.

Example 5

Continuous adsorption-desorption-resorption experiment of the adsorbent prepared in Example 2

In the desorption experiment for the purpose of recovering the heavy metal adsorbed to the adsorbent of the present invention, 1 N sulfuric acid was used. In the sulfuric acid concentration of 1N or less, it was confirmed that the heavy metal is desorbed, but in the case of 1N sulfuric acid, complete desorption is performed within 5 seconds, and the form of beads is also maintained in its original shape. Experiment with 1N sulfuric acid. In the subsequent adsorption-desorption-resorption experiment after desorption, the experiment was performed under the same conditions as the heavy metals used in the adsorption experiment. The throughput at the time of adsorption-desorption-resorption for each heavy metal is shown in Table 1. When defining adsorption-desorption-resorption as one batch, it can be seen that there is almost no change in treatment efficiency up to five batches.

Claims (1)

After optimally incubating Zugria ramizera, add 10 grams of sodium metasilicate per liter of culture and vigorously stir at 40 ° C for 1 hour, then mix 2% sodium alginate solution in this solution at a ratio of 1: 1 for 10 minutes. A method for producing a heavy metal adsorbent with a microbial culture solution, which is stirred vigorously and stirred with a saturated calcium chloride solution.