LiuShen Docket No.FllW1959 t PLANT-DERIVED FLOCCULANT, FLOCCULANT MIXTURE, METHOD OF FLOCCULATION, AND METHOD FOR PREPARING PLANT-DERIVED FLOCCULANT -, • TECHNICAL FIELD [0001] The invention relates to a plant-derived flocculant, a flocculant mixture, a" method of flocculation, and a method for preparing the plant-derived flocculant. BACKGROUND [0002] With mass production and mass consumption in recent years, suspended tparticles discharged in water such as plant drained water keep increasing. Therefore, synthetic polymer flocculants such as polyacrylamide and copolymers thereof are generally used as flocculants for flocculate/separate microparticles dispersed in water, so as to clarify the water. However, there exist the following issues for the synthetic polymer flocculants: [1] Even they are discharged into soil, they are accumulated rather than degraded. [2] Their monomers themselves (acrylamide, etc.) are toxic. [3] They are synthesized using fossil resources such as petroleum which are not renewable materials for human. [0003] Therefore, from the perspective of environmental pollution, safety concerns and exhaustion of fossil resources, development of flocculants having good biodegradability and high safety are desired. [0004] For natural polymer flocculants, although guar gum (seed extract of guar from Family Fabaceae), sodium alginate (extract of brown algae such as kelp, Ecklonia cava, Eisenia bicyclis, etc.), starch, gelatin, chitosan, etc. have been studied, these materials have not been widely used yet because they either are difficult to raise and cultivate, or have limited use and poor flocculability. [0005] Moreover, according to Japanese Patent Laid-open Hll-114313, a flocculant that comprises at least one of Molokheiya, dried Molokheiya, and Molokheiya extract is widely known. [0006] Prior art document . • 09/06/13-Version 1 ' i ' " -• • ' - - LiuShen Docket No.FUW1959 t Patent document Patent document 1: Japanese Patent Laid-open Hll-114313 SUMMARY [0007] Problems to be solved by the invention Although the flocculant disclosed in the aforementioned Japanese Patent Laid-open Hll-114313 can effectively flocculate suspended particles, a flocculant with a higher flocculability is still desirable. [0008] Therefore, an object of the invention is to provide a plant-derived flocculant with a higher flocculability, a flocculation mixture based on said plant-derived flocculant, and a method for preparing said plant-derived flocculant. [0009] Means to solve the problems The plant-derived flocculant of the invention for achieving the aforementioned object has a colloid equivalent of -1.5 mEq/g to -0.20 mEq/g, and its 2 weight% aqueous solution has a viscosity of more than 6.0* 10"3 Pa-s (6.0 cP). [0010] The flocculant mixture of the invention for achieving the aforementioned object comprises the plant-derived flocculant of the invention and a synthetic polymer flocculant having a colloid equivalent of -4.5 mEq/g to -1.2 mEq/g, whose 0.2 weight% aqueous solution has a viscosity of 1.3x10"1 Pa-s to 4x10"1 Pa-s (130 cP to 400 cP). [0011] The flocculation method of the invention for achieving the aforementioned Y object is adding the aforementioned plant-derived flocculant of the invention into a suspension to flocculate and isolate the microparticles in the suspension. [0012] The method for preparing the plant-derived flocculant of the invention for achieving the aforementioned. object is a method for preparing the aforementioned plant-derived flocculant of the invention by drying the plant (sometimes also called the "plant raw material") at a temperature lower than 100°C. [0013] The use of the plant-derived dried material for achieving the aforementioned object is to prepare a flocculant, wherein the colloid equivalent of the plant-derived dried material is -1.5 mEq/g to -0.20 mEq/g, and its 2 weight% aqueous solution has a viscosity of at least 6.0xl0"3 Pa-s. - ' ' • - . 09/06/13-Version 2.;. LiuShen Docket No.FUW1959 H • [0014] Effect of the invention [0015] For the plant-derived fiocculant of the invention, the plant-derived flocculant in the fiocculant mixture of the invention, the plant-derived flocculant in the flocculation method of the invention, or the plant-derived flocculant prepared by the method for preparing the plant-derived flocculant of the invention, it has an excellent flocculation performance since its colloid equivalent and the viscosity of its 2 weight% aqueous solution have been defined. Hence, the supernatant after the flocculation treatment and the filtered water after the dehydration filtration are highly clear. Furthermore, it has high safety to the environment and human beings. Moreover, it is renewable and has excellent flocculation activity, which can be used widely: it is applicable to various fields such as drained water treatment field, water supply/sewage field, fermentation industry, paper industry, construction industry, etc. DETAILED DESCRIPTION [0016J The invention is illustrated below based on examples. However, the invention is not limited by the examples. The various values and materials in the examples are merely exemplary. Moreover, the illustration is conducted in the following order. [0017] 1. General description of the plant-derived flocculant, the flocculant mixture, the flocculating method, and the method for preparing the plant-derived flocculant of the invention [0018] 2. Example 1 (the plant-derived flocculant, the flocculant mixture, the flocculant method,- and the method for preparing the plant-derived flocculant of the invention), etc. [0019] [General description of the plant-derived flocculant, the flocculant mixture, the flocculant method, and the method for preparing the plant-derived flocculant of the invention] [0020] The plant-derived flocculant of the invention, the plant-derived flocculant in the flocculant mixture of the invention, the plant-derived flocculant in the flocculation method of the invention, or the plant-derived flocculant prepared by the method for preparing 1 09/06/13- Version : '• - . 3 ' ' i ' I LiuShen Docket No.FUW1959 the plant-derived flocculant of the invention (the aforementioned is sometimes called "the flocculant in the invention" in general, hereinafter) can be in a form of a dry material comprising Corchorus olitorius, or in a form of a dry material comprising Begonia fimbristipula, or in a form of a dry material comprising bananas, or in a form of a dry material comprising Corchorus capsularis, or in a form of at least one dry material selected from the dry material of Corchorus olitorius, the dry material of Begonia fimbristipula, the dry material of bananas, and the dry material of Corchorus capsularis. For the plant material, any parts such as leaves, stalks, stems, roots, fruits and petals can be used, especially preferred parts such as leaves, stalks, stems and flowers, more preferred parts such as leaves and stalks are desirable because they are convenient for powder processing. As to plant raw material, the location and season of cultivation are not particularly limited. Corchorus olitorius is mostly cultivated and harvested in China; Begonia fimbristipula is mostly cultivated and harvested in Japan; and bananas are mostly cultivated and harvested in Southeast Asia. [0021] The flocculant of the invention, including the aforementioned preferred forms, is preferably in a form of a dry material obtained by drying the plant (plant material) at a temperature of lower than 100°C. When the plant material is dried at a temperature of at least 100°C, it is possible that heat deterioration occurs to one soluble polymer component of the plant raw material (specifically, for example, polysaccharides which undergo breakage of main chains and pending chains to reduce the molecular weight, and render infusible and carbonized due to intramolecular crosslinking) thereby reducing the flocculation performance. For the drying method, sun drying, drying in the shade, hot wind drying, vacuum drying, freeze drying, and cold drying, etc. can be exemplified. [0022] For the flocculant mixture of the invention, including the aforementioned preferred forms, when in each unit weight of the flocculant mixture, the weight of the plant-derived flocculant is Wi and the weight of the synthetic polymer flocculant is W2, it is desirable that they satisfy the following conditions: 2/8<10"2Pa-s (50 cP). In addition, the flocculant mixture of Example 1 comprised the plant-derived flocculant of Example 1 and a synthetic polymer • flocculant having a colloid equivalent of -4.5 mEq/g to -1.2 mEq/g whose 0.2 weight% aqueous solution has a viscosity of 1.3 xlO"1 Pa-s to 4x10"1 Pa-s (130 cP to 400 cP). The flocculation method of Example 1 was adding the plant-derived flocculant of Example 1 to the suspension and flocculating and isolating the microparticles in the suspension. The method for preparing the plant-derived flocculant of Example 1 was the method for preparing the plant-derived flocculant of Example 1 by drying the plant (sometimes also called "plant raw material") at a temperature of lower than 100°C. [0047] For Example 1, Corchorus olitorius (leaves, stalks, stems, flowers and roots), Begonia fimbristipula (leaves), banana (skin), and Corchorus capsularis (leaves and stalks) served as the plant raw material of the plant-derived flocculant. Furthermore, Mizuna (leaves and stalks), Komatsuna (leaves and stalks), spinach (leaves and stalks), Garland chrysantheum (leaves and stalks), Perilla frutescens viridis (leaves), Chinese cabbage (leaves and stalks), butterbur, napa cabbage (leaves), cabbage (leaves), mimosa, and Japanese Angelica tree were used as the plant raw material of the flocculant of Comparative Example 1. Then, these plant raw materials were dried at a certain temperature for a certain time with a heat drier so as to obtain the flocculants of Example 1 and Comparative Example 1. The water content of the flocculants of Example I and Comparative Example 1, although . 09/06/13-Version TO LiuShen Docket No.FllW1959 depending on the drying conditions, could be 4.5 weight%~25 weight%. The flocculants of Example 1 and Comparative Example 1 were obtained by crushing with a food processor for cooking! [0048] Furthermore, for the synthetic polymer flocculant, the commercially available partial hydrolysates of polyacrylamide having different colloid equivalent and aqueous solution viscosity (polymer flocculant A~polymer flocculant F) was used. It should be noted that the extents of the partial hydrolysis of the polymer flocculant A~polymer flocculant F were different. [0049] The measurement of the viscosity of the aqueous solution was based oh the follow method, i.e., the flocculants of the example and the comparative example were added into pure water and dissolved/dispersed, thereby forming a 2 weight% aqueous solution. Then, the viscosity of the aqueous solution was measured using B Type viscometer (manufactured by Toky Sangyo). More particularly, the temperature of the aqueous solution was adjusted to 25°C, and the measurement was conducted using No. 1 rotor at the spinning speed of 60 rpm. It should be noted that for viscosity measurement of the aqueous solution of the synthetic polymer flocculant, it was formulated into 0.2 weight% aqueous solution. [0050] The measurement of the colloid equivalent value was based on the following method, i.e., 50 ppm aqueous solutions of the flocculants of Example 1 and Comparative Example 1 were formulated. Specifically, 0.2 of various flocculants of Example 1 and Comparative Example 1 (converted to the weight of the dry product) were precisely weighed and placed in a conical flask and dissolved/dispersed with 100 ml ion exchange water. Furthermore, 390 ml ion exchange water was added to 10 ml of such aqueous solution as the measurement sample. [0051] For the measurement of the colloid equivalent value, 100 ml measurement sample was placed in the conical flask and 0.5 ml of 1/10 equivalent concentration sodium hydroxide aqueous solution was added with agitation. Then, -5 ml of 1/200 equivalent concentration methyl glycol chitosan solution was added with agitation for 5 minutes. Furthermore, 2 to 3 drops of toluidine blue was added and a titration was conducted with 1/400 equivalent concentration of polyvinyl potassium sulfate reagent. The titration speed was 2 ml/min. The endpbint was when the test sample turned purple from blue and 09/06/13-Version " " 11 LiuShen Docket No.FllW1959 m maintained this state for at least 30 seconds. [0052] It should be noted that as the biank experiment for the colloid equivalent value measurement, 100 ml ion exchange water was used as the test sample for the same operations as above. [0053] Here, the absolute value of the colloid equivalent value (unit: mEq/g) could be calculated according to the following equation. [0054] The absolute value of the colloid equivalent value =| 1/2* (titration amount of the test sample -titration amount of the blank experiment) x(titration value of 1/400 equivalent concentration polyvinyl potassium sulfate reagent)| [0055] The following suspension was used as the suspension (drained water) for the flocculation assessment. That is, the pH of the waste solution discharged from a semiconductor plant (containing hydrogen fluoride and phosphoric acid) was adjusted to 8 by adding slaked lime. 500 ppm aluminum sulfate was added to the precipitated calcium fluoride and calcium phosphate for condensation, and the resultant solution was used as the suspension for assessment. It should be noted that the suspension for assessment had a pH of 6.8, suspended solids (SS) of 2.5 weight%, and an electric conductivity (EC) of 0.246 S/m. [0056] For assessment of flocculation, the following method was used. That is, 100 ml suspension for assessment was added to a 200 ml cylinder with a cork of the same material. Then, the flocculants of the example and comparative example were added by pipetting, so that certain concentration of the polymer components and the solid components relative to the suspension were reached (2.5 ppm or 10 ppm). Then, the cylinder was immediately inverted for agitation for 10 times. Subsequently, it was left to stand to measure the settling speed of the suspended particles. It should be noted that the settling speed was calculated according to the time consumed for the flocculation interface dropping from 80 ml to 60 ml. Moreover, the clarity of the supernatant after 3 minute stand was assessed by visual observation. Then, the flocculation solution was filtered by gravity using filter cloth (twill) made by polypropylene and the clarity of the filtrate was assessed by visual observation. The aforementioned measurement resultsare shown in Tables 1 -Table 3. - . • • " 09/06/J 3-Version - " 12 | • ' . . _ • • • i ' ' • - - £ W I—I—I : 1—' 1 1 1 -~ fe fe •£ ' * • - &, 1 " ^ •' • "Q § o vo ^ , , ', 5 ^ n n W • | o vq £ , , , ^ g • • • • " s • w • r ^ '^ •s: - vJ -, O ^ ° I • I _ l : • s d a . 2 .2 • • S d d d >• >• | m^tf ^ f 1.8.8 -a • n ^ > >£ "' . d d t/3 C/3 • t> S> ^ ___^_ •' • a § s § J3 -3 "S-^S I a £ * ^ e ^° v5 U -S ^ O o a >, « § d fe M -b -o, -S ^ O o rs >v | H ^ OQ > . . ^- 1 1 1 1 1 I 1 1 1 ; 1 OS i ' • ^ OH r^ W d o o f> o> i i r S ^ v v ' 5 i V* x "$. oj i—i • >v o . C ^ Q O ""> W> i . i S ^ v y | - -S ON vd ^ ' ' ' o V >< x ^ : : • /) x x X O o v W ; ^ v v O V O § I o ^. r3 • , , , § V? x x ^ S ^ ^ ^ o 2 V x x O JO . • 5ft ^ y y O V X X •—i : Tf ' D u ' • S ^ x x - | > > ^ o ' .... 2 V XX . 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H x 3 . g 3 '"E, . : r x w •' s 1 •< C C co V hn hn ^ S g _ .2 _ .2 ^ es o o 3 .2 £ i E 8 ! 1 - - - £ ! • • i—i •G ° a J 3 2 S3 B +=; ^, co «£ 3 a " ^ I ^ | 3 TJ I « 3 • ^ a - J « . I 1 — L I I 1 I 1 1 PU i i n 5 2 * d = S 2 x x • ' . • £ ' ' • '• d 3 • o O ; • .• ^ n a © °- § V? x x ' - o d u rt ^ • o o eg -S £ -3- > 3 "3 -a jl ' * . I I I o 1 « 111••£ I. : ... §. . 1 a | i a i u f . .. 5 t i l ° ' • • • . . 1 LiuShen Docket No.FllW1959 ™ [0060] Based on the results of Table 1, it can be known that compared to other plant-derived flocculants (Comparative Example l-A~Comparative Example 1-K), the plant-derived flocculants of Example l-A~Example 1-D obtained from Corchorus olitorius, Begonia fimbristipula, banana, and Corchorus capsular is having a certain colloid equivalent value and aqueous solution viscosity exhibit excellent flocculation properties as settling speed, as well as the clarity of the supernatant after the flocculation treatment and the filtrate after the dehydration filtration. [0061] In addition, it is known by comparing Example 1-E and Example 1-F in which the drying temperature was lower than 100°C and Comparative Example 1-L~Comparative Example 1-0 in which the drying temperature was at least 100°C that the flocculation performance of Comparative Example l-L~Comparative Example 1-0 is poorer. It is presumed that when the plant raw materials were dried at a temperature of more than 100°C, heat deterioration occurred to one water soluble polymer component of the plant raw materials so as to make the flocculation performance poorer. [0062] Furthermore, for the flocculant mixtures of Example l-G~Example 1-L which were the mixtures of synthetic polymer flocculants, which were anionic polymer flocculants having certain colloid equivalent values and aqueous solution viscosities, and plant-derived flocculants, it was determined that they had excellent flocculation properties with lower amount of addition (2.5 ppm). it should be noted, when the synthetic polymer flocculants without the certain colloid equivalent values and aqueous solution viscosities (Comparative Example l-Q~Comparative Example 1-S) were used, and when the synthetic polymer flocculants were used themselves (Comparative Example 1-P), the desirable flocculation effect could not be obtained. [0063] As mentioned above, the flocculants of Example 1, compared to the flocculants of Comparative Example 1 or traditional flocculants, have excellent flocculation properties (for example, settling speed and filtrate turbidity). Moreover, because. the flocculants of Example 1 are natural occurring substances, they are renewable and safe to human beings and environment, therefore, the cake (the dehydrated) and coagulum, which have long since been subject to the disposal by burning or dumping, can be re-used as compost or feed. The cake is very easy to be made fuel or compost. From the perspectives 09/06/13-Version ''. 18 LiuShen Docket No.FllW1959 ^r of saving resources, reducing harmful substances and effectively using the disposed materials, great contribution can be made to the environmental protection of the earth. Furthermore, since the flocculants of Example 1 have large quantities of plant fiber components, the cake and the flocculate are very easy to he stripped off from the press cloth when the cake and the flocculate are subject to dehydration. Moreover, the cake and the flocculate have deodorization effect on the processing water. [0064] The invention has been illustrated on the basis of the preferred examples, but the invention is not limited by these examples and can have various modifications. In the example, Corchorus olitorius, Begonia fimbristipula, banana and Corchorus capsularis'were used individually, but the same flocculation properties can also been obtained by using the combination of {Corchorus olitorius, Begonia fimbristipula), the combination of {Corchorus olitorius, banana), the combination of {Corchorus olitorius, Corchorus capsularis), the combination of {Begonia fimbristipula, banana), the combination of {Begonia fimbristipula, Corchorus capsularis), the combination of (banana, Corchorus capsularis), the combination • of {Corchorus olitorius, Begonia fimbristipula, banana), the combination of {Corchorus olitorius, Begonia fimbristipula, Corchorus capsularis), the combination of {Corchorus olitorius, banana, Corchorus capsularis), the combination of {Begonia fimbristipula, banana, Corchorus capsularis), and the combination of {Corchorus olitorius, Begonia fimbristipula, banana, Corchorus capsularis). 09/06/13-Version 19 . LiuShen Docket No.FllW1959 W CLAIMS 1. A plant-derived flocculant having a colloid equivalent of -1.5 mEq/g to -0.20 mEq/g, whose 2 weight% aqueous solution has a viscosity of at least 6.0*10"3 Pa-s, 2. The plant-derived flocculant according to claim 1, which comprises a dried matter of Corchorus olitorius. 3. The plant-derived flocculant according to claim 1, which comprises a dried matter of Begonia fimbristipula. 4. The plant-derived flocculant according to claim 1, which comprises a dried matter of bananas. 5. The plant-derived flocculant according to claim 1, which comprises a dried matter of Corchorus capsularis. 6. The plant-derived flocculant according to claim 1, which comprises at least one dried material selected from a dried matter of Corchorus olitorius, a dried matter of Begonia fimbristipula, a dried matter of bananas, and a dried matter of Corchorus capsularis. 7. The plant-derived flocculant according to any one of claims 1~6, which comprises a dried matter obtained by drying a plant at a temperature of lower than 100°C. 8. A flocculant mixture, comprising: a plant-derived flocculant having a colloid equivalent of -1.5 mEq/g to -0.20 mEq/g, whose 2 weight% aqueous solution has a viscosity of at least 6.0x10" Pa-s; and a synthetic polymer flocculant having a colloid equivalent of -4.5 mEq/g to -1.2 mEq/g, whose 0.2 weight% aqueous solution has a viscosity of 1.3 x 10"1 Pa-s to 4x 10"1 Pa-s. 9. The flocculant mixture according to claim 8, wherein the plant-derived flocculant comprises at least one dried material selected from a dried matter of Corchorus olitorius, a dried matter of Begonia fimbristipula, a dried matter of bananas, and a dried matter of Corchorus capsularis. 10. The flocculant mixture according to claim 8 or 9, wherein when in each unit weight of the flocculant mixture, the weight of the plant-derived flocculant is Wi and the weight of the synthetic polymer flocculant is W2, they satisfy the following conditions: 2/8