JPH0732874B2 - Metal adsorbent - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

[0001] The present invention is a novel metal adsorbent using algae of red tide plankton, more specifically, it can adsorb and recover valuable metals in mine drainage, factory drainage, etc. with high efficiency, In addition, the present invention relates to a novel metal adsorbent that uses algae of red tide plankton that can be regenerated and reused.

[0002]

2. Description of the Related Art Industrial waste liquors generated from mines and factories contain heavy metals that are toxic to biological systems. If they are drained as they are, they will cause environmental pollution. Therefore, they must be removed before they are discharged into rivers. is necessary. In addition, there are cases where many useful heavy metals are contained in these industrial waste liquids, but it is not preferable to discard them as they are from the viewpoint of effective use of resources.

Therefore, in terms of preventing environmental pollution and securing resources, removal and recovery of heavy metals in various industrial waste liquids have become important social problems.

Until now, inorganic adsorbents such as activated carbon, synthetic zeolite, silica gel, activated alumina and activated clay have been mainly used as adsorbents for recovering and removing heavy metals from aqueous solutions.

However, these inorganic adsorbents are
Since the adsorption capacity is limited, in order to treat a large amount of waste liquid, a large amount must be used accordingly, and desorption treatment has a lot of troubles and equipments. There are many problems to solve.

[0006] On the other hand, some microorganisms and algae have the ability to accumulate specific heavy metals. Therefore, it is attempted to recover the heavy metals in the waste liquor by utilizing them, and plant biomass, mold, chlorella A method using such as is proposed. However, the microorganisms and algae used so far are not always satisfactory in terms of the adsorption capacity for heavy metals, and they are difficult to reuse again, and have not yet been put into practical use.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made with the object of providing a biological adsorbent which has a higher heavy metal adsorption capacity than conventional microorganisms and algae and which can be easily regenerated. Is.

[0008]

Means for Solving the Problems As a result of various studies to obtain a substance having a high adsorption capacity for heavy metals from various algae, the present inventors have found that one of the causes of water pollution has been
Chattonella anka, a species of red tide plankton that has been regarded as troublesome in the fishing industry
It has been found that (tiqua) has a large adsorbing ability for various heavy metals, and that when it is cultured under stimulating conditions, the adsorbing ability remarkably increases, and the present invention has been completed based on this finding. It was

That is, according to the present invention, a metal adsorbent comprising an alga of Chattonella antica and Shatonella antica are cultivated at a high density in a medium containing inorganic nutrient salts, and the alga is extracted from the culture solution to extract the metal. A method for producing an adsorbent is provided.

The Shatonella antica used in the present invention is
It is a species of plankton that grows in the ocean and has a size of 5
It consists of single cells of 0-60 microns and can be easily collected from the red tide. This Chattonella Antica is
It is a photosynthetic compound that grows in the presence of carbon dioxide, light energy, inorganic nitrogen and phosphorus, and can be grown by adjusting the illuminance of light, temperature, and element concentration in the medium to conditions that stimulate growth. You can

Therefore, in the metal adsorbent of the present invention, the Chattonella antica thus collected is contained in a medium rich in inorganic nutrient salts, for example, in 1 liter of seawater, in an amount of 1 to 10 mg of alkali metal dihydrogen phosphate. , Alkali metal sulfate 10 to 100 mg, and iron content 0.5 to 5 mg in a medium containing 20 to 26 ° C., preferably 25 ° C.
Keep it back and forth, illuminate more than 15,000 lux,
It is produced by culturing with aeration and stirring.

At this time, the atomic ratio of nitrogen to phosphorus in the medium is 3: 1 to 1: 1, preferably 2: 1, and the atomic ratio of iron to phosphorus is 1: 4 to 1: 7, preferably 1 :. It is 5. Under such culture conditions, the production of metal adsorbents is improved by maintaining a higher concentration so that the nutrient elements in the medium become constant when the growth of Chattonella antica is stopped. be able to.

Further, as described above, the production amount can be further increased by changing the culture conditions, particularly the elemental composition in the medium to stimulate the proliferation ability of Chattonella antica.

Therefore, in the production of the metal adsorbent of the present invention, it is advantageous to keep the growth environment of Chattonella antica in an extreme state and maximize its production capacity. One of the means is to add iron or arsenic to the medium. For example, when an aqueous solution containing iron is added to the medium, this is taken up by the cells of Chattonella antica, and at the same time, the heavy metal adsorption amount of Chattonella antica increases to a high value of 300 mg per 1 g (dry weight) of algal cells.

In the medium thus cultivated, when the growth of Chattonella antica reaches the maximum density (usually 10 ⁶ cells / ml or more), the medium is cooled,
Centrifugation treatment is performed to precipitate and concentrate the algal cells, which are then collected. This culturing time depends on the culturing conditions, but is usually 1 to
10 days.

Next, the wet algal cells thus obtained are subjected to extraction treatment with a mixture of chloroform and methanol, the solvent is removed, and distilled water is added to the residue to boil it.

The metal adsorbent of the present invention can be obtained by centrifuging the treated product and freeze-drying the obtained solid content.

The metal adsorbent thus obtained usually has an ability to adsorb 300 mg or more of heavy metal per 1 g.

In order to separate and recover heavy metals from an aqueous solution containing heavy metals using the metal adsorbent of the present invention, the metal adsorbent is packed in, for example, a column and weakly acidic (pH 6).
Pass the heavy metal-containing aqueous solution adjusted to about At this time, the heavy metal-containing aqueous solution is preferably adjusted to a salt concentration of 0.05 to 1.0 mol.

By this treatment, the heavy metals in the aqueous solution are rapidly adsorbed by the adsorbent, separated and removed.

Next, in order to recover the heavy metal from the metal adsorbent having adsorbed the heavy metal in this way, the metal adsorbent may be brought into contact with an aqueous hydrochloric acid solution. The concentration of this hydrochloric acid aqueous solution is 2
The range of 6 to 6 is appropriate. By this treatment, heavy metals can be recovered with a yield of 90% or more.

Heavy metals that can be adsorbed by the metal adsorbent of the present invention include, for example, copper, cobalt, nickel, cadmium, manganese, gallium and zinc.

[0023]

The present invention will be described in more detail with reference to Examples.

Example 1 Seawater containing Chattonella antica was added to an inorganic nutrient medium prepared by adding 21 mg of sodium sulfate, 13 mg of sodium dihydrogen phosphate, and 1 mg of iron to 1 liter of seawater. The cells were aerated under light irradiation of 1,000 lux and agitated for 6 days.

Then, the culture solution is centrifuged to separate the alga bodies, and the obtained wet alga bodies are first extracted with an equal volume mixture of chloroform and methanol and then with boiling distilled water.

A metal adsorbent was produced by freeze-drying the thus extracted alga cells.

Example 2, Comparative Examples 1 and 2 Metal chlorides shown in Table 1 were added in an amount of 0.
The pH of the aqueous solution containing 5 mg was adjusted to 6.0 with hydrochloric acid, the metal adsorbent obtained in Example 1 was added at a rate of 2 g per liter of the aqueous solution, and the mixture was allowed to stand at room temperature for 30 minutes. The amount of metal remaining in the sample was measured, and the recovery rate of each metal by the metal adsorbent was determined. The results are shown in Table 1.

For comparison, two kinds of phytoplankton other than Shatonella antica, namely, Heterosigma akashiw, are used.
o) and Dunaliella Salina
Salina) 19/30 was also used, and the recovery rate when the same metal-containing aqueous solution was treated with the same metal adsorbent was also shown.

[0029]

[Table 1]

Example 3 In Example 1, the algal cells were simply treated with an equal volume mixture of chloroform and methanol (defatted algal cells), and the algal cells were further subjected to boiling treatment with distilled water (heat-treated algal cells). )
Using the above, the same experiment as in Example 2 was carried out for a metal-containing aqueous solution containing only cadmium and having a pH adjusted to 5.9, and the cadmium recovery rate was obtained. As a result, it was 80.2% in the case of defatted algal cells, whereas it was 94.8% in the case of heat-treated algal cells.

Example 4 and Comparative Examples 3 to 7 Using various algae collected from seawater, a metal adsorbent was produced in the same manner as in Example 1, and each of cadmium, copper, nickel and cobalt was added to 1 liter of seawater. The recovery rate for each metal of each algae was determined in the same manner as in Example 2 using a sample having a pH of 5.8 contained at a ratio of 1 mg, and the results are shown in Table 2.

[0032]

[Table 2]

As is clear from this table, the recovery rate of the metal adsorbent using the Shatonella antica of the present invention is remarkably superior to the other ones.

[0034]

INDUSTRIAL APPLICABILITY The adsorbent of the present invention can be produced by utilizing red tide plankton, which has been regarded as a troublesome source of environmental damage, and has a high adsorption capacity for various heavy metals. It is suitable for removing harmful metals from waste liquid and recovering useful heavy metals.

Claims (2)

[Claims] 1. Chattonella Antica (Chatton)
A metal adsorbent consisting of algal cells of ella antiqua). 2. Chattonella Antica (Chatton)
A method for producing a metal adsorbent, which comprises culturing ella antiqua) at a high density in a medium containing inorganic nutrients, separating algal cells from the culture solution, and subjecting to extraction treatment.