JP2017061739A - Method of recovering rare earth element with green algae - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of recovering rare earth elements which can recover low-concentration rare earth elements with high selectivity while reducing environmental load without environment contamination.SOLUTION: A method of recovering rare earth elements comprises the step of bringing green algae of Scenedesmus, or an algal processed product thereof, or an extract therefrom into contact with a rare earth element.SELECTED DRAWING: None

Description

The present invention relates to a method for recovering rare earth elements with high selectivity.

Rare earth elements (rare earths) are indispensable materials for improving the performance of electronic parts such as phosphors, storage batteries and light emitting diodes. Japan's waste contains a rare earth element corresponding to the 10th place in the world's reserves, and there is a need to develop technology for recovering rare earth elements from waste and recycling them in Japan. Yes. Conventionally, a method of using a chemical such as a strong acid to recover a rare earth element is known, but it has a problem of high risk and toxicity and a large environmental load.

On the other hand, as a method for recovering rare earth elements with a small environmental load, a technique for adsorbing and separating rare earth elements by the biological action of microorganisms has been developed.

Patent Document 1 discloses a method of adsorbing rare earth ions in an aqueous solution using chlorella or spirulina. However, in the method using chlorella, the selectivity to the metal is not sufficient, and metals other than rare earth elements are also mixed.

Patent Document 2 and Non-Patent Documents 1 and 2 disclose a method of recovering or removing metal ions contained in a solution by culturing red algae isolated from a sulfuric acid hot spring in the solution. However, rare earth elements are recovered under the condition of pH 2.5, and in order to improve the selectivity for metals, it is necessary to further make a strong acid condition of pH 1. When recovering at an industrial scale and recovering under these pH conditions, it is difficult to manage the reaction conditions, and there is a problem that the load on the environment is large.

JP-A-6-212309 JP2013-67826A

Minoda et al. , Appl Microbiol Biotechnol 2015 Feb; 99 (3): 1513-9 University of Tsukuba, National Institute of Advanced Industrial Science and Technology, Osaka University, Japan Science and Technology Agency Press Release “Sulfuric hot spring red algae efficiently absorb rare earths under strongly acidic conditions” October 1, 2014

It is an object of the present invention to provide a method for recovering rare earth elements that can recover a low concentration of rare earth elements with high selectivity while reducing environmental burden without causing environmental pollution.

The present invention relates to a method for recovering a rare earth element, which comprises a step of bringing a green algae belonging to squid duck, a processed alga body thereof, or an extract thereof into contact with the rare earth element.

It is preferable to carry out the step of bringing the green algae belonging to squid duck or the processed alga body thereof or the extract thereof into contact with a rare earth element at a pH of 5 to 9.

The rare earth element is preferably yttrium, europium, neodymium, or dysprosium.

It is preferable to perform the step of contacting the green algae belonging to squid duck, the processed alga body thereof, or these extracts with a rare earth element under the presence of glucose.

It is preferable that the processed alga body is a heat-dried product, a freeze-dried product, or a dried product under reduced pressure.

It is preferable that a green alga belonging to squid duck, a processed product of the alga body, or an extract thereof be immobilized on a carrier or included in a membrane.

It is preferable that the green algae belonging to Ikadamo is a green algae belonging to the genus Scenedesmus.

It is preferable that the green algae belonging to Ikadamo is a green algae belonging to Scenedesmus acumintus.

Moreover, this invention relates to the collection | recovery agent of rare earth elements containing the green algae which belong to squid duck, its alga body processed material, or these extracts.

It is preferable that the green algae belonging to Ikadamo is a green algae belonging to the genus Scenedesmus.

It is preferable that the green algae belonging to Ikadamo is a green algae belonging to Scenedesmus acumintus.

According to the rare earth element recovery method and recovery agent of the present invention, a low concentration of rare earth elements can be selectively recovered without overloading the environment, contributing significantly to the effective use of resources and the preservation of the global environment. It is expected to do.

The sorption of Eu by green algae is shown. The sorption of Y by green algae is shown. The time course of Eu sorption by Sample 8 is shown. 4A to C are microscopic observation views of algae A to C, respectively. The sorption of Eu by algaeA-C which comprises Sample8 is shown. FIG. 6A shows Eu sorption by algaeA. FIG. 6B shows Y sorption by algaeA. FIG. 7A shows Eu sorption by algaeB. FIG. 7B shows Y sorption by algaeB. FIG. 8A shows the yield of metal by algaeA under carbonless / light conditions, FIG. 8B shows carbonless / dark conditions, FIG. 8C shows glucose addition / light conditions, and FIG. 8D shows glucose addition / dark conditions. The sorption of Nd, Eu, Dy, Y by green algae is shown.

The present invention relates to a method for recovering a rare earth element, which comprises a step of bringing a green algae belonging to squid duck, a processed alga body thereof, or an extract thereof into contact with the rare earth element.

In the present invention, squid shellfish is used as the green algae. By using squid damo, rare earth elements can be selectively recovered while suppressing the mixing of elements other than rare earth elements.
Examples of the squid damo include green alga belonging to the genus Scenedesmus or the genus Desmodesmus. In the present invention, among these, it is preferable to use Ikadamamo belonging to the genus Scenedesmus. The Scenedesmus genus may also be referred to by the alias Actodedesmus genus.

The Scenedesmus genus, Scenedesmus acuminatus (Acutodesmus acuminatus), Scenedesmus abundans, Scenedesmus acutus, Scenedesmus armatus, Scenedesmus balatonicus, Scenedesmus brasiliensis, Scenedesmus carinatus, Scenedesmus circumfusus, Scenedesmus communis, Scenedesmus costatus, Scenedesmus dactyloccoides, Scenedesmus denticulatus, Scenedesmus dispar, Scened esmus elegans, Scenedesmus ecornis, Scenedesmus granulatus, Scenedesmus intermedius, Scenedesmus javanensis, Scenedesmus longispina, Scenedesmus maximus, Scenedesmus microspina, Scenedesmus nanus, Scenedesmus oahuensis, Scenedesmus opoliensis, Scenedesmus pannonicus, Scenedesmus pecsensis, Scenedesmus perforates, Scenedesmus polyglobulus, Scenedesmus olydenticulatus, Scenedesmus product-capitatus, Scenedesmus protuberans, Scenedesmus quadricauda, Scenedesmus qutwinskii, Scenedesmus raciborskii, Scenedesmus rostrato-spinosus, Scenedesmus serratus, Scenedesmus sooi, Scenedesmus spinosus, Scenedesmus spicatus, Scenedesmus unicus, include Scenedesmus vesiculosus. Among these, Scenedesmus accuminatus is preferable.

As a Desmodesmus species, Desmodesmus abundans, Desmodesmus acuminatus, Desmodesmus acutus, Desmodesmus armatus, Desmodesmus balatonicus, Desmodesmus brasiliensis, Desmodesmus carinatus, Desmodesmus circumfusus, Desmodesmus communis, Desmodesmus costatus, Desmodesmus dactyloccoides, Desmodesmus denticulatus, Desmodesmus dispar, Desmodesmus elegans, Desmodesmu s ecornis, Desmodesmus granulatus, Desmodesmus intermedius, Desmodesmus javanensis, Desmodesmus longispina, Desmodesmus maximus, Desmodesmus microspina, Desmodesmus nanus, Desmodesmus oahuensis, Desmodesmus opoliensis, Desmodesmus pannonicus, Desmodesmus pecsensis, Desmodesmus perforates, Desmodesmus polyglobulus, Desmodesmus polydenticulatus, Desmode mus product-capitatus, Desmodesmus protuberans, Desmodesmus quadricauda, Desmodesmus qutwinskii, Desmodesmus raciborskii, Desmodesmus rostrato-spinosus, Desmodesmus serratus, Desmodesmus sooi, Desmodesmus spinosus, Desmodesmus spicatus, Desmodesmus unicus, include Desmodesmus vesiculosus.

Squidamo can also be identified by its 18S rDNA sequence. The 18S rDNA sequence of Ikadamo used in the present invention preferably has 90% or more homology with the base sequence described in SEQ ID NO: 1, more preferably 95% or more, and more preferably 98% or more. It is further preferable to have a homology of 99% or more.

Green algae belonging to Ikadamo can be cultured by a usual method. For example, in a liquid medium containing phosphorus, nitrogen, carbon, and trace elements (boron, manganese, zinc, copper, molybdenum, iron), 20-30 ° C, preferably 20-25 ° C, preferably 4-17 days, A method of culturing for 7 to 14 days can be mentioned.

As the green algae belonging to Ikadamo, a culture solution obtained by culturing Ikadamo can also be used, and an algal body obtained by removing liquid components from the culture solution of Ikadamo can also be used. The algal body may be a wet alga body or a dry alga body. When using a wet algal body, it can be used after washing | cleaning ikadamo after culture | cultivation with an ultrapure water.

In order to recover the rare earth element, a processed product of green algae belonging to Ikadamo can also be used. Examples of the processed alga body include a freeze-dried product, a dried product under reduced pressure, a dried product by heating, a concentrated product, a processed paste product, and a diluted product.

In order to recover rare earth elements, green algae belonging to Ikadamo or extracts of processed alga bodies can also be used. The extract preferably contains an enzyme, a structural protein, a cell membrane, a cell wall, or the like that contributes to the sorption of rare earth elements.

The rare earth elements are scandium (Sc), yttrium (Y), and lanthanoids classified into Group 3 in the periodic table. Lanthanoids include cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Td), dysprosium (Dy), holmium ( Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu). The rare earth element recovered in the present invention is preferably yttrium, europium, neodymium, or dysprosium. The rare earth element may be present as a salt. Examples of such salts include YCl ₃ , EuCl ₃ , NdCl ₃ , and DyCl ₃ .

The contact method between the green alga belonging to Ikadamo and the rare earth element is not particularly limited as long as the rare earth element can be sorbed by Ikadamo. For example, a wet alga body of squid shellfish is suspended in ultrapure water, and the suspension and a rare earth element-containing liquid are mixed and reacted. In the recovery method of the present invention, the rare earth element can be efficiently recovered even when the concentration of the rare earth element in the solution is low. The concentration of the rare earth element in the reaction liquid containing squid damo and the rare earth element may be 0.5 mg / L or less, or 50 mg / L or less.

The pH condition of the reaction solution containing green algae belonging to squid duck and rare earth elements is preferably pH 5-9, more preferably pH 6-8, and even more preferably pH 7-8. When the pH exceeds 9, the rare earth element tends to form an insoluble salt. If the pH is less than 5, the sorption amount tends to decrease.

The temperature of the reaction solution containing green algae belonging to squid duck and rare earth elements is preferably 20 to 30 ° C, and more preferably 20 to 25 ° C. The light condition may be a bright condition or a dark condition. Examples of the contact time between the squid duck and the rare earth element include 12 to 24 hours.

It is preferable that the reaction liquid containing the green alga belonging to Ikadamo and the rare earth element further contains a carbon source. By including a carbon source, the recovery efficiency for rare earth elements can be improved. Examples of the carbon source include glucose, lactose, sucrose, and maltose. The concentration of the carbon source is preferably 100 to 1000 mg / L. Moreover, carbon can also be supplied by bubbling carbon dioxide gas through a reaction solution containing squid duck and rare earth elements.

After sorption of rare earth elements to green algae belonging to Ikadamo, the green algae belonging to Ikadamo are precipitated by centrifugation, and an eluent is added to the precipitate, whereby the rare earth elements can be eluted from Ikadamo. Examples of the eluent include an acid solution, and among these, HNO ₃ is preferable. The sorption amount of the rare earth element can be measured using, for example, a high frequency inductively coupled plasma emission analysis method (ICP emission analysis method).

Moreover, this invention relates to the collection | recovery agent of the rare earth elements containing the green algae which belong to a squid duck, or its alga-body processed material, or these extracts. Examples of the form of the recovery agent include pellets, tablets, and cultures. The collection agent is lightweight and has good storage stability. An appropriate number can be set according to the concentration of the rare earth element and the amount of the solution containing the rare earth element, and the necessary amount can be used when necessary. .

The recovery agent may contain an excipient, a stabilizer, and an antioxidant in addition to the green algae belonging to squid duck, or a processed product of the alga body, or an extract thereof.

In the method for recovering rare earth elements, the alga bodies, processed alga bodies, and algal body extracts of green algae belonging to squid duck may be contacted with the rare earth elements in a state of being immobilized on a carrier. By bringing algae bodies, algae body processed products, and algae body extracts into contact with rare earth elements in a state of being immobilized on a carrier, the collection of rare earth elements can be carried out in large quantities in a shorter time. The body treatment product and the algal extract can be recovered from the treatment target liquid and reused.

Examples of the carrier for immobilizing algal bodies, processed algal bodies, and algal body extracts include synthetic resins such as alumina, silica, activated carbon, and polyacrylamide, and polysaccharides such as carrageenan. Immobilization of the algal body, the processed algal body, and the algal body extract to the carrier can also be performed using a crosslinking agent. A carrier on which algal bodies, processed alga bodies, and algal body extracts are immobilized is also referred to as an immobilized carrier. In general, a carrier on which a biocatalyst is immobilized is known as an immobilized biocatalyst. Putting alga bodies, processed alga bodies, and algal body extracts into capsules also falls under the immobilization method. By inclusion fixing, alga bodies, processed alga bodies, and algal body extracts can be protected and kept at a high concentration. As a result, it is possible to contribute to high efficiency by long-term use of the recovery agent and high concentration.

Examples of the contact method between the algal body, the processed algal body, the carrier on which the algal extract is immobilized, and the rare earth element include a floating method and a contact method using a column.

In the floating method, an algal body, a processed algal body, an algal body extract, or a carrier on which these are immobilized is brought into contact with a rare earth element in a suspended state in a reaction solution. The specific gravity of the immobilized carrier obtained by immobilizing the algal body, the processed alga body, and the algal body extract on the carrier is preferably close to 1. By bringing the specific gravity closer to 1, the floating property in water is improved, and the relative contact area between the rare earth element and the algal body, the processed algal body, and the algal body extract is increased, and the sorption efficiency can be improved. In general, in water treatment, it is said that the power required for blower and stirring for air blowing to suspend the immobilization carrier accounts for about 70% of the cost. If it can improve, processing cost can be reduced. In addition, since alga bodies are likely to settle, the contact area with the rare earth element can be increased by providing an appropriate buoyancy, and the recovery efficiency can be improved.

In the contact method using a column, a carrier on which algal bodies, processed algal bodies, and algal body extracts are immobilized is packed into a column, and a solution containing rare earth elements is passed through the column to selectively remove rare earth elements. Sorption. Thereafter, if necessary, the column is washed under appropriate conditions, and the sorbed rare earth element is desorbed, whereby the rare earth element can be recovered as a concentrated liquid. The desorption of rare earth elements can be performed by changing pH, changing temperature, pressurizing / depressurizing, applying voltage, and changing light conditions. The flow direction of the solution containing the rare earth element to the column may be an upward flow or a downward flow. By setting the upward flow, the column bed filled with the immobilization carrier in the column can be filled with the liquid to be treated, so that sorption becomes easy. In the case of a downward flow, since it is a natural flow, liquid passing energy to the column is unnecessary.

The contact with the alga body, the alga body processed product, and the algal body extract can be performed in combination with a membrane separation treatment method. Specifically, an alga body, an alga body processed product, an algal body extract, or a carrier carrying them is wrapped in a membrane and brought into contact with a liquid to be processed. By this method, alga bodies, processed alga bodies, algal body extracts, or carriers carrying them can be maintained at a high concentration and can be protected with a membrane. Examples of the membrane include a membrane, a semipermeable membrane, and a ceramic membrane. Membranes enclosing the alga bodies, the processed alga bodies, the algal body extracts, or the carrier carrying them can be modularized, and the modules can be increased or decreased and replaced as necessary.

(Reference Example 1) Collection and cultivation of green algae Water containing green algae was collected from a plurality of environments. Green algae were cultured in a culture solution containing P (phosphorus), N (nitrogen), C (carbon), and a trace amount of minerals at a temperature of 23 ° C. for 12 hours in the dark and light. Culture fluid components are shown in Tables 1-3. A5 solution and Fe solution shown in Tables 2-3 were diluted 1000 times and added to the culture solution.

Green algae that reached the stationary phase were dispensed into a centrifuge tube, washed with ultrapure water, and then the wet weight of the alga bodies was measured. 100 mg / L EuCl ₃ or YCl ₃ solution was added, and the mixture was shaken for 24 hours at 23 ° C. in a bright place.

After the 24-hour shaking, the green algae and the metal solution were centrifuged, and the green algae were washed with ultrapure water. 0.1M HNO ₃ was added and allowed to stand for 1 hour to elute the metal in the algal cells. Then it was centrifuged again. The amount of Eu and Y contained in the HNO ₃ solution is defined as the amount of rare earth elements (rare earth) recovered by sorption of green algae, and the concentration of Eu and Y contained in the separated metal solution and 0.1 M HNO ₃ solution Measurement was performed using a high frequency inductively coupled plasma optical emission spectrometry (ICP optical emission spectrometry).

For 24 samples in which Eu and Y sorption was confirmed, the sorption amount of Eu per 1 g of wet weight of the alga is shown in FIG. 1, and the sorption amount of Y is shown in FIG. As shown in FIGS. 1-2, Sample8 (S8) can collect many rare earth elements.

Furthermore, the time course of Eu sorption by Sample 8 was examined when the EuCl ₃ concentration was 100 mg / L. The result is shown in FIG. In FIG. 3, black represents the sorption amount of the rare earth element per algal body unit wet weight, and white represents the recovery rate. As shown in FIG. 3, when Sample 8 is used, when green algae are brought into contact with the rare earth element, sorption of the rare earth element is started rapidly and is considered to end in 24 hours.

(Example 1, Comparative Examples 1 and 2) Isolation of algae Sample 8 selected in Reference Example 1 contained a community state in which a plurality of algae were mixed. In order to isolate algae that contribute to the sorption of rare earth elements, the algae were isolated by pipette washing using a microscope and cultured in an inorganic nutrient medium. As a result, three types of green algae could be isolated. For convenience, the isolated algae were designated as algaeA, algaeB, and algaeC. FIGS. 4A to C show microscopic views of algae A to C, respectively.

Eu sorption was again performed by the method described in Reference Example 1 using the isolated algae bodies of Algae A (Example 1) and algae B to C (Comparative Examples 1 and 2). The results of Example 1 and Comparative Examples 1 and 2 are shown in FIG. FIG. 5 shows that algaeA greatly contributed to Eu sorption in the algae group, and algaeC hardly contributed to Eu sorption. Thereafter, as a result of repeated microscopic observations, it was determined that algaeA belongs to squid damo and algaeC belongs to chlorella.

(Example 2, Comparative Example 3) In order to find the optimum conditions for recovering more rare earth elements than the sorption test of rare earth elements with algae A and algae B, the light conditions for algae A (Example 2) and algae B (Comparative Example 3) The effects of carbon and carbon conditions on the recovery efficiency of rare earth elements were investigated. Two series of light and dark places were set when the metal solution contacted for 24 hours in an artificial meteorograph. In addition, the carbon source contained in the metal solution was set to 3 series of 0 mg / L (control), 100 mg-C ₆ H ₁₂ O ₆ / L, or CO ₂ gas, and the sorption amount of rare earth elements was compared. The sorption amount of the rare earth element by algaeA is shown in FIGS. 6A to B, and the sorption amount of the rare earth element by algaeB is shown in FIGS. 6-7, white represents the collection result in a bright place, and black represents the collection result in a dark place.

As shown in FIGS. 6A and 6B, algae A (Example 2) did not change the Eu sorption amount depending on the presence or absence of light, and the Eu sorption amount decreased in the presence of glucose and CO ₂ . On the other hand, the sorption amount of Y does not change significantly due to light conditions when no carbon source is present or in the presence of CO _2, but the sorption amount increases in the dark in the presence of glucose. . In the presence of CO _{2, the} amount of sorption increased compared to the case where no carbon source was present regardless of the light conditions.

As shown in FIGS. 7A and 7B, argae B (Comparative Example 3) increased the amount of sorption when Eu and Y were both in a bright place. As for the carbon source, the sorption amount decreased in the presence of CO _{2 in the} light place, and no change in the sorption amount due to the carbon source was observed in the dark place.

(Example 3) Selective recovery test of rare earth element The selective recovery of rare earth element when heavy metal elements coexist was examined using an algae A isolate which is a kind of squid. Cultured green algae (algae A isolate) in a solution containing 7 metals of Eu, Y, Zn, Ni, Mo, Cu, and Mn at a concentration of 5 mg / L, respectively, at a concentration of 4.0 mg-wet / mL Added in. Thereafter, the mixture was shaken at 190 rpm for 24 hours. When shaking for 24 hours, it was shaken under four conditions depending on whether it was light or dark, and whether or not glucose (100 mg / L) was present. Thereafter, the metal solution and the algal bodies were separated by centrifugation (2500 rpm, 10 min), and the solution was further centrifuged (10000 rpm, 10 min) and diluted 10 times. 0.1M HNO ₃ was added to the algae, stirred and allowed to stand for 1 hour, then centrifuged in the same manner, and the supernatant was diluted 10-fold. With respect to the prepared solution, the above-mentioned seven kinds of metal concentrations were measured using ICP emission spectrometry, and the respective recoveries were obtained.

FIG. 8A shows the yield of metal by algaeA under carbonless / light conditions, FIG. 8B shows carbonless / dark conditions, FIG. 8C shows glucose addition / light conditions, and FIG. 8D shows glucose addition / dark conditions. 8A to 8D, white indicates the amount of metal remaining in the solution as a ratio, and gray indicates the amount of metal sorbed and recovered by the algal bodies as a yield (ratio).

8A to 8D, Eu and Y were recovered with extremely high selectivity compared to Zn, Ni, Mo, Cu, and Mn. Under bright conditions, Eu and Y selectivity of glucose addition (FIG. 8C) was improved compared to carbon-free (FIG. 8A). Even in the dark condition, Eu and Y selectivity of glucose addition (FIG. 8D) was improved compared to carbon-free (FIG. 8B).

(Example 4) Rare earth element sorption test The amount of sorption of Nd, Eu, Dy, Y by algae A was examined. The sorption conditions were as described in Reference Example 1 except that the sorption conditions were performed in the light for 24 hours and the initial metal concentration was 0.5 mg / L, 5 mg / L, 15 mg / L, 25 mg / L, or 50 mg / L. Performed according to the described sorption conditions. The amount of sorption of each element is shown in FIG. Similarly to Eu and Y, Nd and Dy also sorbed on the algae.

(Example 5) Identification of algae The 18S rDNA sequence of algae A was identified. The base sequence is shown in SEQ ID NO: 1 in the sequence listing. Subsequently, a sequence homologous to the nucleotide sequence of SEQ ID NO: 1 was searched by BLAST from the international nucleotide sequence database. As a result, the 18S rDNA sequence of algaeA showed the highest homology with the 18S rDNA of Scenedesmus accuminatus Hagewald 1986-2 strain (Accession No. AB037088), and the homology was 99.8%. algaeA was determined to belong to Scenedesmus accuminatus. The specification of 18S rDNA sequence and the search for homologous sequences were carried out at Techno Suruga Lab.

Claims (11)

A method for recovering a rare earth element, comprising a step of contacting a green algae belonging to squid duck, a processed alga body thereof, or an extract thereof with a rare earth element. The method according to claim 1, wherein the step of contacting the green alga belonging to squid duck, the processed alga body thereof, or an extract thereof with a rare earth element is performed at pH 5-9. The method according to claim 1 or 2, wherein the rare earth element is yttrium, europium, neodymium, or dysprosium. The method according to any one of claims 1 to 3, wherein the step of contacting the green algae belonging to squid duck, the processed alga body thereof, or the extract thereof with a rare earth element is performed under the presence of glucose. The method according to any one of claims 1 to 4, wherein the processed alga body is a heat-dried product, a freeze-dried product, or a vacuum-dried product. The method according to any one of claims 1 to 5, wherein a green alga belonging to squid damo, a processed product of the alga body, or an extract thereof is immobilized on a carrier or included in a membrane. The method according to any one of claims 1 to 6, wherein the green alga belonging to the squid damo is a green alga belonging to the genus Scenedesmus. The method according to any one of claims 1 to 7, wherein the green alga belonging to Ikadamo is a green alga belonging to Scenedesmus acminatus. A rare earth element recovery agent comprising green algae belonging to squid duck, or a processed product of the algae, or an extract thereof. The collection | recovery agent of Claim 9 whose green algae which belongs to Squidamo is a green algae which belongs to Scenedesmus genus. The collection agent according to claim 9 or 10, wherein the green alga belonging to Ikadamo is a green alga belonging to Scenedesmus accumintus.