JP2006167632A - Heavy metal recovery system from heavy metal absorbing plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heavy metal recovery system from heavy metal absorbing plant bodies and its method reducing possibility of occurrence of various problems like scattering of heavy metals by incineration, and allowing effective utilizing of plant biomass, having less environmental load. <P>SOLUTION: This heavy metal recovery method from heavy metal absorbing plant bodies comprises processes for: hydrolyzing heavy metal absorbing plant to recover pentose and/or hexose; applying alcohol fermentation to the pentose and/or hexose recovered in the previous process and separating and recovering alcohol obtained in the previous process; and recovering heavy metals from residual aqueous solution after separating and recovering alcohol from the fermentation liquid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heavy metal recovery system and a heavy metal recovery method capable of converting heavy metal and carbohydrates in the plant into alcohol from the plant that has absorbed heavy metal and recovering heavy metal.

  A technology (phytoremediation technology) that absorbs heavy metals from heavy metal-contaminated soil or contaminated water using plants is known (for example, Patent Document 1 (Japanese Patent Laid-Open No. 2003-319787)). In addition, as a post-treatment method for plants that have absorbed heavy metals, the plants are generally incinerated (Non-Patent Document 1 (Civil Engineering, 2003, vol. 44, No. 12)).

  As shown in Non-Patent Document 1, when heavy metals contained in contaminated soil and water are removed by plants and plants that have absorbed heavy metals are incinerated, some heavy metals are likely to be scattered by incineration, such as arsenic. As with dioxins, dust countermeasures such as the installation of bug filters are required. In this case, the incineration facility is expensive. In addition, simply incinerating plant bodies, which are biomass resources, and releasing carbon dioxide to the atmosphere increases energy utilization and increases the concentration of carbon dioxide in the air, leading to global warming. Absent. Therefore, in a system for removing heavy metals by plants, a method for treating heavy metals in plants that is not incinerated is desired.

JP2003-319787 Civil engineering, 2003, vol.44, No.12

  Therefore, in view of the actual situation as described above, the present invention reduces the possibility that various problems such as scattering of heavy metals due to incineration processing occur, and enables the effective use of plant biomass, which is a heavy metal-absorbing plant with less environmental impact. An object of the present invention is to provide a heavy metal recovery system and a heavy metal recovery method from the body.

  The present invention that has achieved the above-described object includes the following.

  (1) Applying a hydrolysis treatment to a plant that has absorbed heavy metals to recover pentose and / or hexose, and a solution containing pentose and / or hexose collected in the above step And a step of separating and recovering alcohol from the fermentation broth obtained in the above step, and a step of recovering heavy metal from the residual aqueous solution after separating and recovering alcohol from the fermentation broth. A method for recovering heavy metals from heavy metal-containing plants.

  (2) The method for recovering heavy metal according to (1), wherein the hydrolysis treatment is performed under a condition in which the plant that has absorbed the heavy metal is heated and pressurized in sulfuric acid.

  (3) The heavy metal recovery method according to (1), wherein the heavy metal is at least one heavy metal selected from cadmium, arsenic, and lead.

  (4) The method for recovering heavy metals according to (1), wherein the method for converting the sugar in the hydrolysis treatment liquid into alcohol is alcohol fermentation by microorganisms.

  According to the heavy metal recovery method of the present invention, heavy metals can be efficiently recovered from plants that have absorbed heavy metals from heavy metal-contaminated soil or contaminated water, and plant biomass can also be used effectively. .

  Hereinafter, the present invention will be described in detail.

  A system to which the heavy metal recovery method according to the present invention is applied is schematically shown in FIG. That is, this system is a system that utilizes plants that have absorbed heavy metals as heavy metal-containing plant biomass, recovers heavy metals, and effectively converts biomass components and recovers them as energy.

  In this system, the plant is not particularly limited, but rice, sorghum, corn, reed canary grass, herbaceous (lawn), poplar and tamarix trees (hardwood and conifers), fern and other terrestrial plants, water hyacinth, Aquatic plants such as lotus, water lettuce, reed and eelgrass can be used. Moreover, as a plant, it is desirable to use the thing excellent in decomposition | disassembly efficiency to the monosaccharide level by the hydrolysis process mentioned later. More specifically, it is preferable to use a plant having a high monosaccharide, disaccharide, oligosaccharide, or polysaccharide (starch, hemicellulose, cellulose, pectin) content. Examples of hemicellulose include xylan having pentose as a main chain and xyloglucan having pentose as a side chain. In particular, from the viewpoints of absorption efficiency of heavy metals, environmental adaptability, etc., mallow, akaza, arabiaceae, echaeaceae, Brassicaceae, Rubiaceae, iridaceae, iridaceae, gramineceae, lobsteraceae, Inogayaceae Family, Laboraceae, Duckweed, Udonaceae, Pteridomyceae, Papilioceae, Ominae, Pteridomycete, Cannaceae, Gammaidae, Mapleaceae, Birchaceae, Cyperaceae, Oleaceae, Lepidoptera, Oleanderaceae, Ranunculaceae, Ranunculaceae Gyoryaceae, Asteraceae, Walnut Family, Camphoraceae, Peacockaceae, Anemoneaceae, Gummyaceae, Mulberry Family, Poppyaceae, Ganodermaaceae, Sesame Family, Rubber Family, Taro Family, Shikimidae, Shiso Family, Perillaceae Family , Ginger family, Dendrobaceae family, Lindenaceae family, Honeysuckle family, Prunus family, Violet family, Seri family, Ze Myrtaceae, Cryptomeriaceae, Nymphaea, Ceramidaceae, Bromeliaceae, Tamaidae, Tadeidae, Azalea, Camellia, Camellia, Periwinkle, Periwinkle, Euphorbiaceae, Crestaceae, Passifloridae, Toberidae , Cypressaceae, eucommia, eggplant, urchinaceae, eleganaceae, genus genus, genus genus, cedaraceae, radish, elm, genus, genus genus, genus, rose, cypress, cypress, cypress Family, Amaranthaceae, Cleopteraceae, Auriculariaceae, Amaranthaceae, Grapeaceae, Beechaceae, Myrtaceae, Bentillaceae, Button, Saturniidae, Acaciaceae, Leguminosae, Pinaceae, Amaranthaceae, Purpleaceae, Barberry, Oleaceae, magnoliaceae, ilexaceae, willowaceae, japonica, cypressaceae, straw Family, palm family, lily family, for example, spinach of the family Rabbitaceae, chard, redwood, spinach, scallops, mustards belonging to the Brassicaceae family, Alpsgunbainasuna, yellow mustards, kenaf, okra, troroaoi Rice, Reed, Tsuruyoshi, Reed canary glass, Canary glass, Pampas grass, Sorghum, Centipede, Naginata gaya, Japanese barnyard millet, Tall fescue, Shiba, Koraishiba, Vetiver grass, Tall fescue, Sudan grass, Orchard grass, Perennial ryegrass, Bahia grass, Guinea Grass, corn, oats, spruce, rush, barley, barbaceae, barnaceae, cinnamon sunflower, asteraceae sunflower , Gypsaceae Tamarix, Ceramaceae Giant Plover, Poleaceae Itadori, Pseudozoaceae Tutanashiko, Rosaceae Porcupine, Papaveraceae Papaver, Convolvulaceae Daikandra, Papaveraceae Mexican Mannengusa, Pepperaceae belonging to Legumes It is preferable to use plants such as white clover, crimson clover, astragalus, sesbania, fairy vetch, alfalfa, water hyacinth belonging to the family Mulberry, red willow, poplar.

  By cultivating these plants in contaminated soil containing heavy metals, the heavy metals in the contaminated soil can be accumulated in the plants. Moreover, these plants are not limited to contaminated soil containing heavy metals, and can be cultivated in contaminated water areas containing heavy metals, dredged bottom mud, and the like. Here, “cultivate plants” means to sow and cultivate seeds of these plants and to transplant and cultivate plants from different places.

  The plant cultivation period can be determined based on the plant type, heavy metal concentration in the contaminated soil, and weather conditions. For example, in the case of kenaf 80 to 120 days, in the case of rice 90 to 180 days, In the case of sorghum, it can be 90 to 150 days, and in the case of lead canary glass, it can be 180 to 210 days.

  After harvesting the plant that has absorbed the heavy metal, the plant is hydrolyzed as described later, and it is desirable to silage the harvested plant prior to the hydrolysis treatment. Here, silageization means lactic acid fermentation of harvested plants in a storage such as a silo. By silaging harvested plants, plants containing heavy metals can be stored for a relatively long time. As a result, by silaging a plant containing heavy metals, the steps described below can be performed in a distributed manner, and the plant scale for performing the steps described below can be reduced.

Next, in the present system, the plant containing the harvested heavy metal or the silaged plant is subjected to a hydrolysis treatment to recover pentose and / or hexose. This step includes, for example, a sulfuric acid solution (preferably 1% to 75% sulfuric acid concentration), a hydrolase solution, a microorganism having ethanol fermentation ability to secrete a hydrolase, and ethanol in which the hydrolase is fixedly exposed on the cell surface. A microorganism or the like having fermentation ability can be used. More specifically, as a method for recovering pentose and hexose, first, a plant is treated in a sulfuric acid solution under relatively mild conditions to recover pentose and hexose in hemicellulose. Thereafter, the hexose can be recovered by treating the plant residue in a sulfuric acid solution under relatively severe conditions.

  In addition, the method for recovering pentose and / or hexose by hydrolysis treatment is not limited to the acid treatment described above, but has a supercritical water method, an enzymatic decomposition method, and an ethanol fermentation ability to secrete a hydrolase. Techniques such as microorganisms and microorganisms having ethanol fermentation ability in which hydrolytic enzymes are fixedly exposed on the surface of the cells can also be applied.

  Next, in this system, an alcohol fermentation process is performed on the solution containing the pentose and / or hexose collected in the above step, and the saccharide in the solution is converted into alcohol. In this step, as an alcoholic fermentation treatment, a treatment for adding an enzyme involved in alcoholic fermentation to a solution containing pentose and / or hexose collected in the above step to advance an alcoholic fermentation reaction, and The process which adds the microorganisms which have alcohol-fermenting ability with respect to the solution containing the pentose and / or 6-sugars collect | recovered at the said process and advances alcohol fermentation reaction by the effect | action of the said microorganisms can be mentioned. The solution containing pentose and / or hexose collected in the above step is adjusted to a pH suitable for the alcohol fermentation treatment and then subjected to the alcohol fermentation treatment.

  Here, as a series of enzymes involved in the production of alcohol from glucose, hexokinase, glucose phosphate isomerase, aldolase, triose phosphate isomerase, glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase, phosglycerome mutase, enolase And pyruvate kinase, pyruvate decarboxylase, and alcohol dehydrogenase.

  In addition, microorganisms having alcohol fermentation ability include budding yeast Saccharomayces genus (genus Saccharomayces), fission yeast Schizosaccharomyces genus (genus Schizosaccharomyces), genus Pichia (genus Pichia), genus Brettanomyces (genus Brettanomyces), genus Candida (Candida Genus), Zymomonas genus, Thermoanaerobium brockii, Clostridium genus, and genetically modified microorganisms.

  According to this step, the heavy metal can be separated from the plant that has absorbed the heavy metal into an aqueous layer, and at the same time, alcohol conversion can be performed using a carbohydrate such as cellulose or hemicellulose of the plant as a raw material.

  Next, in this system, heavy metals are recovered from the residual aqueous solution separated in the above process. Examples of the heavy metal recovery method include a coagulation precipitation method, ion flotation, ion exchange method, amalgam method, oxidative decomposition-mineralization method, and adsorption method. Specifically, a suitable method is used from among the methods described above according to the type of heavy metal. For example, when the heavy metal is cadmium, it is preferable to use a hydroxide coagulation precipitation method, a sulfide coagulation precipitation method, an ion flotation method, or an ion exchange method. Further, when the heavy metal is arsenic, it is preferable to use an agglomeration coprecipitation method, a sulfide precipitation method, an adsorption method, or an ion exchange method. Further, when the heavy metal is lead, it is preferable to use an aggregated precipitate or an ion exchange method.

  Moreover, in this system, after converting into alcohol by alcohol fermentation process, alcohol can be collect | recovered from a fermented liquor. The recovered alcohol can be used in various fields. Although the method of collect | recovering alcohol from alcohol aqueous solution is not specifically limited, For example, the distillation method, the membrane separation method, or the method which combined both can be mentioned. The distillation method includes a normal distillation method, an azeotropic method, and an extractive distillation method from the viewpoint of classification by vapor-liquid equilibrium, but any method may be used in this system. The distillation method includes a depressurization method, a normal pressure method, and a pressurization method from the viewpoint of classification by operating pressure, but any method may be used in this system. As the apparatus form, there are a single type, a continuous type, a general distillation method, a composite distillation method, and a multi-effect distillation method, but any method may be used in this system. Depending on the operation method, there are a continuous distillation method and a batch method, but any method may be used in this system. In this system, a combination of an azeotropic method and a multi-effect distillation method is desirable from the viewpoint of alcohol purity. As the membrane separation method, there are a reverse osmosis method, a membrane distillation method, a vapor permeation method, and a pervaporation method, and any method may be used in this system. Among these, the use of a zeolite membrane in the pervaporation method is desirable from the viewpoint of energy saving.

  Furthermore, in this system, lignin can also be recovered as a by-product in addition to carbohydrates of alcohol raw materials from plants that have absorbed heavy metals. As a method for recovering lignin, for example, there is a method of separating a solid after hydrolysis by filtration or centrifugation.

  As described above, according to the heavy metal recovery method and the system to which the method is applied according to the present invention, heavy metals can be efficiently recovered from contaminated soil and the plant biomass used for recovery of heavy metals is effectively used. be able to. Moreover, according to the heavy metal collection | recovery method concerning this invention, and the system to which the said method is applied, scattering of heavy metal can also be prevented when collect | recovering heavy metal. In particular, according to the heavy metal recovery method and the system to which the method is applied according to the present invention, it is possible to provide an excellent environmental purification technology that can avoid the conventional incineration processing of used plant biomass. Furthermore, according to the heavy metal recovery method according to the present invention and the system to which the method is applied, plant biomass can be used effectively, and therefore, combined with the improvement of the recovery efficiency of heavy metals, the recovery cost of heavy metals is greatly increased. It is also possible to reduce this to a minimum.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, the technical scope of this invention is not limited to a following example.

[Example 1]
Cadmium recovery from kenaf and ethanol-producing cadmium-containing black soil (cadmium content 7ppm) was filled in 200g as dry soil in a Wagner pot. On the other hand, the hydroponic medium (composition of the International Rice Research Institute (IRRI) as fertilizer) 42 ml of Table 1) was added to prepare a test soil.

  On the other hand, the kenaf used in this example was sown in a seedling culture soil in which vermiculite and pearlite were mixed in a 1: 1 ratio and transplanted to the test soil on the 13th day after germination. After transplanting, the kenaf grown on the 100th day was harvested in both the above-ground part and the below-ground part and subjected to primary crushing (50 mm or less) and secondary crushing (6 mm or less). A part was sampled and the cadmium content was measured. As a result, it contained 35 mg / kg cadmium per dry weight.

10 kg of the crushed material was soaked in 1% sulfuric acid, and a pressure of 5 to 6 kg / cm ² , which was a temperature of 150 to 160 ° C. and a saturated vapor pressure, was applied for 10 minutes in a pressure kettle. By this treatment, pentose and hexose components were extracted from the sulfuric acid solution. Next, slaked lime was added to this solution for neutralization. The neutralized solution was placed in a primary fermenter and ethanol fermentation yeast (Candida shehatae, IFO1983T) was added for ethanol fermentation.

Next, the plant residue in the solution was collected, immersed in 2% sulfuric acid, and a temperature of 200 ° C. and a pressure of 20 kg / cm ² were applied for 1 minute in a pressure cooker. By this treatment, 6 carbon sugar components could be extracted. Next, slaked lime was added to this solution for neutralization. The neutralized solution was placed in a secondary fermenter and budding yeast (Saccharomyces cerevisiae, IFO2347) was added to perform ethanol fermentation.

  Next, after recovering the fermented liquor from the primary fermentor and secondary fermenter, distillation and dehydration were performed, and 1.1 L of ethanol could be recovered.

On the other hand, the waste liquid after alcohol is recovered from the primary fermenter and secondary fermenter is concentrated, and slaked lime is added to adjust the pH to 9-10 to produce a hydroxide agglomeration and precipitation reaction {CdSO ₄ + Ca (OH) ₂ → Cd (OH) ₂ ↓ + CaS0 ₄ ↓} was performed. As a result, 290 mg of cadmium could be recovered in the precipitate. Furthermore, as a result of investigating the cadmium concentration of 1.7 kg of the supernatant after the hydroxide coagulation precipitation reaction, it was about 1 ppm. Therefore, 6 g of the collecting agent Xanthate was added and the precipitation flotation was performed. As a result, 2 mg of cadmium was recovered, and the cadmium concentration in the waste liquid could be reduced to 0.01 ppm or less.

  Through the above treatment, 99% of cadmium contained in the kenaf used for purification was recovered, and ethanol was recovered at a rate of 0.11 L / kg from the saccharide part excluding 12% of lignin contained in biomass. .

[Example 2]
Arsenic recovery and ethanol production from fern (Hevinonegoza) In this example, Hebnonegoza collected from the mountainous area in Japan was used. 200g of Wagner pot filled with arsenic-containing black soil (arsenic content 600mg / kg) as dry soil, and 42ml of the above-mentioned IRRI hydroponic medium (Table 1) was added as a fertilizer. .

  Next, a plant that had passed 5 months from the spore seeding of Hebinonegoza was transplanted to the test soil. 20 kg of all the above-ground and underground parts of Hevinonegoza grown on the 120th day after transplanting was first crushed (50 mm or less) and secondary crushed (6 mm or less). When a part was sampled and the arsenic content was measured, it contained 5,000 mg / kg arsenic per dry weight.

The crushed material was immersed in 1% sulfuric acid, and a temperature of 150 to 160 ° C. and a pressure of 5 to 6 kg / cm ² serving as the saturated vapor pressure were applied in a pressure kettle for 10 minutes. By this treatment, pentose components could be extracted in the sulfuric acid solution. Next, slaked lime was added to this solution for neutralization. The neutralized solution was placed in a primary fermentor, and ethanol fermentation microorganisms were added to perform ethanol fermentation.

Next, the plant residue in the solution was collected, immersed in 2% sulfuric acid, and a temperature of 200 ° C. and a pressure of 20 kg / cm ² were applied for 1 minute in a pressure cooker. By this treatment, 6 carbon sugar components could be extracted. Next, lime was added to this solution to neutralize it. The neutralized solution was placed in a secondary fermenter and budding yeast (Saccharomyces cerevisiae, IFO2347) was added to perform ethanol fermentation.

  Next, after recovering alcohol from the primary fermenter and the secondary fermenter, and then performing distillation dehydration, 2.7 L of ethanol could be recovered.

  On the other hand, the waste liquid after recovering alcohol from the primary fermenter and the secondary fermenter was concentrated to 1.9 kg. The concentration of arsenic after concentration was 12857 ppm. After confirming that the pH was 3-8, sodium hypochlorite and ferric chloride were added to the concentrated waste liquid and stirred for 30 minutes. The arsenic concentration in the waste liquid was about O.1 ppm, and 25 g of arsenic was observed in the precipitate.

  Through the above treatment, 99% or more of arsenic contained in the Hebinonegoza used for purification could be recovered. In addition, ethanol was recovered at a rate of 0.13 L / kg from the carbohydrate portion excluding 25% of the lignin component contained in the biomass.

Example 3
Recovery of cadmium from rice straw stored after silage and storage and ethanol production Cadmium-containing black soil (cadmium content 7ppm) was filled in a 200g dry soil in a Wagner pot, while IRRI's hydroponic medium was used as fertilizer 42 ml of (Table 1) was added to prepare a test soil.

  Rice used in this example was sown in a seedling culture soil in which vermiculite and pearlite were mixed in a 1: 1 ratio, and transplanted to the test soil on the 13th day after germination. After transplanting, the rice grown on the 100th was harvested both above and below. The harvested rice straw for silage was sealed with a wrapping machine. After 2 months of storage, the rice straw wrapping was opened. 10 kg of rice straw stock (water content 15%) was first crushed (50 mm or less) and secondary crushed (6 mm or less). When a part was sampled and the content of cadmium was measured, it contained 2.3 mg / kg of cadmium per dry weight.

The crushed material was immersed in 1% sulfuric acid, and a temperature of 150 to 160 ° C. and a pressure of 5 to 6 kg / cm ² serving as the saturated vapor pressure were applied in a pressure kettle for 10 minutes. By this treatment, pentose components could be extracted in the sulfuric acid solution. Next, lime was added to this solution to neutralize it. The neutralized solution was placed in a primary fermentor, and ethanol fermentation was performed by adding ethanol fermentation microorganisms.

Next, the plant residue in the solution was collected, immersed in 2% sulfuric acid, and a temperature of 200 ° C. and a pressure of 20 kg / cm ² were applied for 1 minute in a pressure cooker. By this treatment, 6 carbon sugar components could be extracted. Next, lime was added to this solution to neutralize it. The neutralized solution was placed in a secondary fermentor, and budding yeast (Saccharomyces cerevisiae, IFO2347) was added to perform ethanolano fermentation.

  Next, after recovering alcohol from this primary fermenter and secondary fermentor, and performing distillation dehydration, 1.2 L of ethanol could be recovered.

  On the other hand, the waste liquid after recovering alcohol from the primary fermenter and the secondary fermenter was concentrated, and slaked lime was added to adjust the pH to 9 to 10 to conduct a hydroxide agglomeration precipitation reaction. As a result, 1.8 mg of cadmium could be recovered in the precipitate. Furthermore, as a result of investigating the cadmium concentration of 0.3 kg of the waste liquid after the hydroxide agglomeration precipitation reaction, it was about 0.5 ppm. Therefore, 0.5 g of the collection agent sanzeate (amyl sanzeate) was added and precipitation flotation was performed, and the cadmium concentration in the waste liquid could be reduced to 0.01 ppm.

  Through the above process, 99% of the cadmium contained in silaged rice straw can be recovered, and ethanol can be recovered at a rate of 0.19 L / kg from the carbohydrate part, excluding 12% of the lignin component in the biomass. It was.

Example 4
Lead recovery from shiba and ethanol-produced lead-contaminated soil (lead content 10000 mg / kg) was filled in 200g as dry soil in a Wagner pot, and 42m1 of IRRI hydroponic medium (Table 1) was added as fertilizer. A test soil was prepared.

  Shiba (tall fescue) used in this example was sown on the test soil. After transplanting, the above-ground part of Shiba grown on the 100th eye was harvested. 30 kg of the harvested product (water content 75%) was subjected to primary crushing (50 mm or less) and secondary crushing (6 mm or less). When a part was sampled and the lead content was measured, it contained 250 mg / kg of lead per dry weight.

The crushed material was immersed in 1% sulfuric acid, and a temperature of 150 to 160 ° C. and a pressure of 5 to 6 kg / cm ² serving as the saturated vapor pressure were applied in a pressure kettle for 10 minutes. By this treatment, pentose components could be extracted in the sulfuric acid solution. Next, slaked lime was added to this solution to adjust to pH 3.0. After adding ferric sulfate to this solution, slaked lime was further added for neutralization. The neutralized solution was placed in a primary fermentor, and ethanol fermentation was performed by adding ethanol fermentation microorganisms.

Next, the plant residue in the solution was collected, immersed in 2% sulfuric acid, and a temperature of 200 ° C. and a pressure of 20 kg / cm ² were applied for 1 minute in a pressure cooker. By this treatment, 6 carbon sugar components could be extracted. Next, slaked lime was added to this solution to adjust to pH 3.0. After adding ferric sulfate to this solution, slaked lime was further added for neutralization. The neutralized solution was placed in a secondary fermenter and budding yeast (Saccharomyces cerevisiae, IFO2347) was added to perform ethanol fermentation.

  Next, after recovering alcohol from this primary fermenter and secondary fermenter, and performing distillation dehydration, 1.9 L of ethanol could be recovered.

  On the other hand, the waste liquid after recovering alcohol from the primary fermenter and the secondary fermenter was concentrated, and slaked lime was added to adjust the pH to 9 to 10 to conduct a hydroxide agglomeration precipitation reaction. As a result, 187 mg of lead could be recovered in the precipitate. Furthermore, as a result of investigating the lead concentration of 1.5 kg of the waste liquid after the hydroxide coagulation precipitation reaction, it was about 0.1 ppm.

  Through the above treatment, 99% of the lead contained in the above-ground part of tall fescue was recovered, and ethanol was recovered at a rate of 0.065 L / kg from the saccharide part excluding 25% of the lignin component contained in the biomass.

It is a figure which shows typically the system to which the heavy metal collection | recovery method which concerns on this invention is applied.

Claims (4)

  Hydrolyzing a plant that has absorbed heavy metals to recover pentose and / or hexose, and alcohol to the solution containing pentose and / or hexose collected in the above step A heavy metal-containing plant comprising a step of performing a fermentation treatment and separating and collecting alcohol from the fermentation broth obtained in the above step, and a step of collecting heavy metal from the residual aqueous solution after separating and collecting the alcohol from the fermentation broth For heavy metal recovery from wastewater.   2. The heavy metal recovery method according to claim 1, wherein the hydrolysis treatment is performed under a condition in which the plant that has absorbed the heavy metal is heated and pressurized in sulfuric acid.   2. The heavy metal recovery method according to claim 1, wherein the heavy metal is at least one heavy metal selected from cadmium, arsenic and lead.   2. The heavy metal recovery method according to claim 1, wherein the method for converting the sugar content in the hydrolysis treatment liquid into alcohol is alcohol fermentation by microorganisms.

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