Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
  • C22B3/18—Extraction of metal compounds from ores or concentrates by wet processes with the aid of microorganisms or enzymes, e.g. bacteria or algae
• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01H—NEW PLANTS OR NON-TRANSGENIC PROCESSES FOR OBTAINING THEM; PLANT REPRODUCTION BY TISSUE CULTURE TECHNIQUES
  • A01H6/00—Angiosperms, i.e. flowering plants, characterised by their botanic taxonomy
  • A01H6/20—Brassicaceae, e.g. canola, broccoli or rucola
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B17/00—Obtaining cadmium
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• the invention relates to plants that hyperaccumulate cadmium and zinc and the use thereof to recover cadmium and zinc from soil.
• hyperaccumulators can be used to reduce the level of cadmium in rice paddies deposited from mine wastes. Prolonged consumption of rice grain produced on contaminated fields can harm human and animal health even if the cadmium concentration is low. A concentration as low as about 1.0 ppm Cd can cause harm if the rice is grown on soil with little ability to adsorb Cd.
• high levels of soil metals deposited by, for example, an industrial accident can be removed using hyperaccumulators. Such removal would be economically feasible.
• phytoextraction Growing plants, including crops, on contaminated soil to extract contaminants is referred to as phytoextraction. This method is particularly effective in arable contaminated soils because it causes little disruption or dispersal, while preserving soil fertility and landscapes.
• Thlaspi caerulescens (alpine pennycress), a non-crop member of the Brassicaceae family, is zinc- and cadmium-tolerant and can accumulate exceptionally high levels of both metals in its shoot tissue.
• T. caerulescens for soil remediation is thought to be limited by its small size (about 15 cm high), slow growth rate and rosette growth habit which would make mechanical harvesting difficult. Dry weight yield over a 6-month growing season has been estimated at 5 t ha "1 (Chaney et al., Current Opinion in Biotech. 8: 279-284 (1997)). Based on the results of preliminary greenhouse and field studies, the time required for phytoremediation of zinc-contaminated soils using T. caerulescens has been estimated to be between 13 and 28 years.
• the metal contents of the biosolids-treated soils were 119, 144 and 181 mg/kg Zn and 1.0, 3.0 and 5.5 mg/kg Cd, respectively.
• Shoot zinc concentration was highest in 71 caerulescens with a maximum of 4440 mg/kg.
• the cadmium concentration of 71 caerulescens which reached a maximum of 28 mg/kg on the soil with the highest metal concentration and the lowest pH, was not significantly different from that of lettuce, but was higher than that of S. vulgaris (18 mg/kg Cd). However, the authors suggested that S.
• vulgaris may be the better choice for phytoremediation of cadmium because, although it accumulated a lower concentration of cadmium in its shoot tissue than 71 caerulescens, the more vigorous growth of S. vulgaris would make it easier to establish and harvest.
• Brainssica oleracea (cabbage), raphanus sativus (radish) and Arabidopsis thaliana) were grown for 5 weeks on soil to which high-metal sewage sludge had been applied from 1942 to 1961, resulting in a metal content of 380 mg/kg Zn and 1 1 mg/kg Cd, both in excess of European (EEC) regulatory levels, i.e., 300 mg/kg Zn and 3.0 mg/kg Cd.
• EEC European
• the hyperaccumulator plants did not accumulate economically useful levels of metals from the contaminated soil.
• the zinc content in 71 caerulescens leaves was about 2000 mg/kg dry weight and the cadmium content was about 20 mg/kg dry weight.
• the soil contains greater than about 1.0 ppm to about 10,000 ppm Cd and/or greater than about 300 ppm to about 100,000-150,000 ppm Zn.
• this invention relates to zinc and cadmium hyperaccumulating plants and systems for recovering metals such as zinc and cadmium using phytoextracting techniques.
• a preferred method of recovering cadmium and/or zinc from soil containing cadmium and/or zinc comprises cultivating at least one 71 caerulescens plant that accumulates cadmium and zinc in above-ground tissues and optionally recovering the cadmium and/or zinc produced.
• the at least one 71 caerulescens plant accumulates from about 0.01 % (100 mg/kg) to about 0.6% (6000 mg/kg) cadmium in above-ground tissues on a dry weight basis and/or from about 0.5% (5000 mg/kg) to about 3.0% (30,000 mg/kg) zinc in above-ground tissues on a dry weight basis.
• the at least one Thlaspi caerulescens plant accumulates from about 1000 to about 6000 mg cadmium/kg above-ground tissues on a dry weight basis and/or from about 15,000 to about 30,000 mg zinc/kg above- ground tissues on a dry weight basis.
• the at least one 71 caerulescens plant is harvested as biomass material after accumulation of the metals and the metals are recovered from the biomass material.
• the metals are recovered by drying and combusting the harvested biomass material to oxidize and vaporize organic material present.
• the metals are recovered from the harvested biomass material by incineration and reduction to ash with energy recovery to produce a cadmium- and/or zinc-containing ore.
• the soil is acidified or at least one chloride salt is added to the soil prior to the cultivation of the at least one 7. caerulescens plant.
• the invention further relates to a method of decontaminating soil containing cadmium and/or zinc, comprising cultivating at least one Thlaspi caerulescens plant that accumulates from about 100 to about 6000 mg cadmium kg above-ground tissues on a dry weight basis and/or from about 5000 to about
• the invention further relates to an isolated Thlaspi caerulescens plant cultivated on cadmium- and/or zinc-containing soil that accumulates cadmium in above-ground tissue at a concentration of from about 100 mg/kg dry weight of the tissue to about 6000 mg/kg dry weight of the tissue and/or accumulates zinc in above-ground tissue at concentration of from about 5000 mg/kg dry weight of the tissue to about 30,000 mg/kg dry weight of the tissue.
• the invention further relates to pollen of the Thlaspi caerulescens plant.
• the invention further relates to plant having all the physiological and morphological characteristics of the Thlaspi caerulescens plant.
• the invention further relates to propagation material of the Thlaspi caerulescens plant.
• the isolated Thlaspi caerulescens plant is 71 caerulescens G15.
• the invention further relates to cultivated Thlaspi caerulescens G15, the seeds of which have been deposited under ATCC Accession No. 203439.
• FIG. 1 illustrates the genotypic difference in cadmium-uptake in plant shoots.
• FIG. 2 is a plot showing the Cd:Zn ratio in shoots of several T. caerulescens genotypes harvested from zinc and cadmium contaminated soils.
• certain metals can be selectively recovered from metal-rich soil using phytoextracting techniques employing plants classified as metal-hyperaccumulators.
• a high concentration of the metals absorbed by the roots is translocated to above-ground tissues, such as the stems, leaves, flowers and other leaf and stem tissues. This facilitates recovery of the metal extracted from the soil such that land contaminated with the metals can be reclaimed and the metals optionally harvested.
• cadmium and/or zinc are recovered from soil containing cadmium and/or zinc by cultivating at least one T. caerulescens plant that accumulates cadmium and/or zinc in above-ground tissues and recovering the cadmium and/or zinc produced.
• the at least one 71 caerulescens plant accumulates from about 0.01% (about 100 mg/kg) to about 0.6% (6000 mg/kg) cadmium in above-ground tissues on a dry weight basis and/or from about 0.5% (5000 mg/kg) to about 3.0% (30,000 mg/kg) zinc in above- ground tissues on a dry weight basis.
• the at least one T. caerulescens plant accumulates from about 0.1% (1000 mg/kg) to about 0.6% (6000 mg/kg) cadmium in above-ground tissues on a dry weight basis, and/or from about 1.5% (about 15,000 mg/kg) to about 3.0% (30,000 mg/kg) zinc in above- ground tissues on a dry weight basis.
• the hyperaccumulator is 71 caerulescens G15, a subspecies of 71 caerulescens, which accumulates much more cadmium than other zinc-accumulators or other T. caerulescens subspecies (FIG. 2).
• this subspecies has the ability to accumulate at least about 1000 mg/kg Cd dry shoots and at least about 18,000 mg/kg Zn dry shoots (FIG. 1).
• the hyperaccumulator plant may be harvested in a conventional fashion, i.e., by cutting the plant at soil level.
• the harvested materials may then be left to dry in much the same fashion that alfalfa is dried, so as to remove most of the water present in the plant tissue.
• the plant tissue may be collected from the field by normal agricultural practices of hay-making, incinerated and reduced to an ash with or without energy recovery.
• the dried plant material may be hydrolyzed with concentrated acid to produce sugars and the metals recovered according to U.S. Patent Nos.
• the sugars may then be fermented to produce ethanol.
• the temperature of the off gas from the incinerator could be monitored such that Cd and Zn metals in gaseous form are condensed from the hot gasses separately from the bulk of the ash components which would condense at a higher temperature or lower temperature in a manner similar to distilling liquids and recovering different fractions at different temperatures.
• this is not possible in the first processing step at a smelter. But with phytoextraction plant incineration, the distillation would most likely be effective during the burning and power production.
• the resulting dried plant material may be further treated by known roasting, sintering or smelting methods which allow the metals in the ash or ore to be recovered according to conventional metal refining methods such as acid dissolution and electro winning. Conventional smelting, roasting and sintering temperatures from about
• 260° C to about 1000° C are sufficient to combust the dried plant material to oxidize and vaporize the organic material present. This leaves a residue of the accumulated metal with few contaminants known to interfere with metal refining. Further, it is expected that the concentration of other components in the ash, such as lead, will be lower than with conventional mined ore concentrates.
• the plant tissue is collected, incinerated and reduced to ash with energy recovery.
• the elements in the ash of T. caerulescens cause little interference with the recovery of Zn and Cd from the ash.
• the result is plant ash of a high grade ore.
• an initial lab study was conducted wherein twenty genotypes of 71 caerulescens were collected from different contaminated sites.
• the collected plants were evaluated in a nutrient solution system treated with high concentrations of zinc and cadmium (2000 mM Zn, 40 mM Cd) and low concentrations of zinc and cadmium (3.16 mM Zn, 0.063 mM Cd).
• the nutrient solution system was half-strength Hoagland Solution which contains a selective ferric chelating agent to keep the Fe soluble in the presence of the Zn and Cd.
• Significant differences were found among the twenty genotypes tested for shoot zinc and cadmium concentrations, plant Cd:Zn ratio and shoot biomass, i.e., shoot yield.
• Several genotypes tested had a low tolerance for the high concentrations of zinc and cadmium.
• caerulescens genotype group confirmed a wide range of zinc tolerance and a wide range of Cd:Zn ratios in shoots obtained from different 7. caerulescens genotypes. As can be seen from FIGS. 1 and 2, remarkable variations in cadmium accumulation and Cd:Zn ratio were observed. Additionally, it was found that lower soil pH favored zinc and cadmium accumulation in shoots. Further, although the "Prayon" genotype (Gl 8) performed well with about 20 g/kg Zn dry shoots and about 200 mg/kg Cd dry shoots, one of the high Cd:Zn ratio genotypes, T. caerulescens G15, accumulated about 1800 mg/kg Cd dry shoots and about 18 g/kg Zn dry shoots.
• soil Cd when soils contain both Cd and Zn, soil Cd will be about 0.5 to about 2.0% of soil Zn. For example, soils with about 150,000 ppm (about 15%) Zn will often not contain more than about 3000 ppm (about 0.3%) Cd. Thus, if the shoot yield is about 2.5% Zn, then the highest Cd one could hope to recover with genotypes used in most research in Thlaspi would be about 0.025%, provided the soil has typical Cd and Zn levels. However, G15 can reach 0.6% mg/kg Cd without plant injury since Genotype G15 has the ability to accumulate additional Cd per unit Zn. Seeds of T. caerulescens G15 were deposited on November 6,
• the higher cadmium-accumulating genotypes are useful for rapid phytoremediation of cadmium-contaminated soil which causes adverse health effects in subsistence consumers of rice or tobacco grown on contaminated soils as described above.
• 71 caerulescens G15 is capable of hyperaccumulating zinc and cadmium in its above-ground plant tissues, fertilizer for growth and/or weed control, particularly in polluted soil, can be used to increase hyperaccumulation because, inter alia, the ability of T.
• Preferred fertilizers are ammonium-containing or ammonium-generating fertilizers.
• the use of fertilizers per se is well-known, and acceptable fertilizers and protocols can be readily determined with no more than routine experimentation, by those of ordinary skill in the art. Normal soil test values for P (required for the growth of all plants), K, Ca and Mg used in farming and gardening will allow the skilled artisan to obtain the needed information regarding fertilization for growing 7. caerulescens plants.
• soil acidification can increase uptake of zinc and cadmium as indicated above.
• soil contains at or near regulatory Zn and
• the pH can be reduced to about 4.5 to about 6.5 to maximize metal uptake.
• the Al and Mn present in the soil become soluble which in turn reduces plant yield.
• the soil pH can be raised to as high as about 9.0.
• the preferred soil pH ranges from about 4.5 to about 9.0.
• acids such as organic and inorganic acids can be used.
• inorganic sulfur is used to reduce the soil pH.
• Inorganic sulfur is oxidized by soil microbes to generate sulfuric acid within the soil. If the soil pH is too low, then bases such as limestone or dolomitic limestone, lime or dolomitic lime, hydrated lime or dolomitic hydrated lime or byproducts thereof that contain a calcium carbonate equivalent or mixtures thereof could be used to raise the soil pH.
• the concentration of acid or base to add to the soil will depend upon the initial soil pH, the desired final soil pH and the soil properties. One of ordinary skill in the art would be able to readily determine the appropriate concentration of acid or base necessary using common soil analysis methods well-known in the art.
• Table 1 shows the effect of fertilizer and acidification treatments on zinc, cadmium and lead accumulation in 71 caerulescens and in a 1993 crop of lettuce.
• the initial condition of the soil was highly calcareous with 25 mg/kg Cd, 475 mg/kg Zn and 155 mg/kg Pb.
• the soil at the test field had become metal enriched by application of ash from a sewage sludge incinerator during a period when the sludge from St. Paul, Minnesota, was highly contaminated with cadmium from a Cd-Ni battery manufacturer. Lime was used to dewater the sludge, however, it prevented the sulfur treatment from acidifying the soil as much as had been expected.
• chelating agents such as nitrolotriacetic acid (NT A), ethylenediaminetetraacetic acid (EDTA), ethyleneglycol-bis-(p-aminoethylether-N, N-tetraacetic acid) or any of a variety of amino-acetic acids known to those of ordinary skill in the art as chelating agents, to the soil improves the movement of soil metals to root surfaces for uptake and translocation into above-ground tissues.
• Preferred chelating agents are NTA or EDTA.
• chelating agents are added at a concentration ranging from about 50 kg/ha to about 3000 kg/ha after the plants are established.
• the optimum concentration of chelating agents can be readily determined with no more than routine experimentation. For example, if EDTA is preferably 10 millimoles/kg soil, then the amount added would be 2.92 kg EDTA/t or 2.921 EDTA/ha since EDTA acid is 292 mg/millimole and one would need to add 2.92 g EDTA/kg soil to achieve 10 millimoles EDTA/kg soil.
• An alternative which improves Cd uptake, but has little effect on Zn uptake, is the addition of a chloride salt that liberates free chloride ion in soil. However, NaCl repeatedly added to soil may harm the soil.
• Chloride forms a complex with Cd (inorganic monochloro-Cd and dichloro-Cd-Cd at levels of chloride tolerated by plants) which increases the rate of diffusion of Cd to the root and causes Cd to leak into the root.
• Preferred concentrations of chloride result in a soil solution containing about 10 to about 200 millimoles of chloride per liter (about 10 to about 200 mM). At the high end, chloride will be toxic to even Thlaspi plants, but Cd removal will increase.

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• 1999
  • 1999-11-23 AU AU17432/00A patent/AU765573B2/en not_active Ceased
  • 1999-11-23 WO PCT/US1999/027731 patent/WO2000031308A1/en active IP Right Grant
  • 1999-11-23 JP JP2000584115A patent/JP4806120B2/ja not_active Expired - Fee Related
  • 1999-11-23 EP EP99960564A patent/EP1200633A4/en not_active Ceased
  • 1999-11-23 CA CA002352179A patent/CA2352179A1/en not_active Abandoned
• 2010
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