Powder, powder composition, method for use thereof and use of the powder and powder composition

Abstract

An iron-boron alloy powder or an iron-boron alloy powder composition suitable for remediation of halogenated hydrocarbon polluted soil, water or groundwater as well as the use of the powder or powder composition. The boron-iron alloy powder suitable for remediation of polluted soil or waters may have 0.1-40% by weight of boron and inevitable impurities up to a content of 10% by weight. Further, a method for remediation of halogenated hydrocarbon polluted soil, water or groundwater.

Claims

1. A method for remediation of polluted soil, groundwater or aquifer comprising the steps of; providing a boron-iron alloy powder comprising 0.7-40% by weight of boron and inevitable impurities up to a content of 10% by weight, contacting the boron-iron alloy powder with the polluted soil, water or groundwater, incubating the mixture of boron-iron alloy powder with the polluted soil, water or groundwater to decompose the pollutants.

2. The method according to claim 1, wherein the boron-iron alloy powder remains in the soil or aquifer after the decomposition reactions have ceased.

3. The method according to claim 1, wherein the pollutants are hydrocarbons comprising halogenated and brominated hydrocarbons, other organics or metals.

4. The method according to claim 3, wherein the pollutants are selected from the group consisting of: the group of chlorinated ethenes comprising tetrachloroethylene (PCE), trichloroethylene (TCE) and, cis-dichloroethylene (cDCE); the group of chloroethanes comprising 1,1,1,2 tetrachloroethane (1111 TeCE), 1,1,2,2 tetrachloroethenes (1122 TeCE), and 1,1,1 trichloroethane (111-TCA), 1,1,2 trichloroethane and 1,1 Dichloroethane (11-DCA); the group of chloromethanes comprising chloroform, dichlorobromomethane-; and the group of chlorinated propanes comprising 1,2,3-trichloropropane.

5. The method according to claim 1, wherein the boron-iron alloy powder consists of 0.7-40% by weight of boron and inevitable impurities up to a content of 10% by weight.

6. The method according to claim 1, wherein the boron-iron alloy powder has an iron content of more than 80% by weight.

7. The method according to claim 1, wherein the boron-iron alloy powder has a boron content of 0.7-4% by weight.

8. The method according to claim 1, wherein the boron-iron alloy powder comprises particles having a particle size range between 10 mm and 1 mm.

9. The method according to claim 1, wherein the boron-iron alloy powder comprises particles having a particle size range between 250 μm and 10 μm.

10. A method for remediation of polluted soil, groundwater or aquifer comprising the steps of: providing a boron-iron alloy powder composition containing a boron-iron alloy powder comprising 0.7-40% by weight of boron and inevitable impurities up to a content of 10% by weight, contacting the boron-iron alloy powder composition with the polluted soil, water or groundwater, incubating the mixture of boron-iron alloy powder composition with the polluted soil, water or groundwater to decompose the pollutants.

11. The method according to claim 1, wherein the boron-iron alloy powder has a boron content between 2% and 40% by weight.

12. The method according to claim 5, wherein the boron-iron alloy powder has a boron content between 0.7 and 40% by weight and an iron content between 60% and 75% by weight.

13. The method according to claim 1, wherein the boron-iron alloy powder has an inevitable impurities content of less that 3% by weight.

14. The method according to claim 1, wherein the inevitable impurities comprise copper and sulfur, and the boron-iron alloy powder has a content of copper and sulfur between 0.5% and 5% by weight.

15. The method according to claim 5, wherein the boron-iron alloy powder has an inevitable impurities content of less that 3% by weight.

16. The method according to claim 1, wherein the boron-iron alloy powder has an iron content of more than 60% by weight.

17. The method according to claim 1, wherein the boron-iron alloy powder has a boron content of 0.7-30% by weight.

18. The method according to claim 1, wherein the boron-iron alloy powder comprises particles having a particle size range between 20 mm and 0.5 mm.

19. The method according to claim 1, wherein the boron-iron alloy powder comprises particles having a particle size range between 0.5 mm and 10 μm.

20. The method according to claim 1, wherein the boron-iron alloy powder comprises particles having a particle size range between 50 μm to 1 μm.

21. The method according to claim 18, wherein the boron-iron alloy powder comprises aggregated particles.

22. The method according to claim 18, wherein the boron-iron alloy powder is produced from a gas atomized or water atomized molten iron-boron alloy.

23. The method according to claim 18, wherein the boron-iron alloy powder is produced from grinded or milled solidified pieces of various size of an iron-boron alloy melt.

Description

DETAILED DESCRIPTION

(1) The present invention provides a solution to the above mentioned problems and is based on the unexpected finding that ZVI particles, alloyed with boron (B), exhibit a surprisingly high efficiency in terms of decomposing halogenated/chlorinated hydrocarbon polluted water and soil. It has also been shown that ZVI, alloyed with B, having a relatively coarse particle size, well above so called nano-sized scale, have the same or higher efficiency for decomposing halogenated/chlorinated hydrocarbon polluted water and soil compared to finer ZVI and/or nano-scale ZVI.

(2) Furthermore, the materials according to the invention exhibit a relatively long life-time making them suitable for remediation purposes, especially remediation of polluted soil/groundwater. In a first aspect of the present invention it is provided a B-iron alloy powder (also denominated as B-ZVI alloy powder) having a B-content of 0.1-40% by weight, preferably 0.1-30% by weight, preferably 0.1-20% by weight, preferably 0.1-10% by weight, preferably 0.1-5% by weight or preferably 0.3-4% by weight. Other intervals of boron contents according to the first aspect of the present invention are 0.5-15% by weight, 0.5-10% by weight, 0.5-7% by weight, 0.5-5% by weight, 0.5-4% by weight, 0.7-4% by weight, 0.7-3.5% by weight or 0.8-3% by weight. A content of B above 40% by weight does not contribute to improved properties in terms of reaction efficiency and will also considerably increase the cost of the material. B-content below 0.1% by weight will not render the alloy powder the desired properties. In this context, B-content above 20% by weight, or above 10%, or even above 7% by weight may increase the risk that excessive amounts of B are released to the recipient, thus constituent a potential environmental problem. The optimal B-content is depending of e.g. type and concentration of chemicals (for instance chlorinated hydrocarbons) to be decomposed and type of polluted soil, water or groundwater.

(3) Preferably, the B-ZVI alloy powder has a content of Fe of more than 60% iron, preferably more than 80% by weight, preferably more than 85%, preferably more than 90% by weight, preferably more than 93% by weight, preferably more than 95% by weight, preferably more than 96% by weight, preferably more than 96.5% by weight.

(4) The amount of inevitable impurities such as carbon, oxygen, sulphur, manganese and phosphorus should be less than 10%, preferably less than 7%, preferably less than 5% by weight, preferably less than 3% by weight.

(5) Carbon and sulphur may in some embodiments contribute to the remediation and thus the contents of these elements can be controlled to desired levels. Such levels may be up to 5% by weight.

(6) In addition other elements such as copper, silver, gold, platinum and palladium may be intentionally added.

(7) The particle size may be in the interval of 20 mm and 1 μm. The optimal particle size range is depending of e.g. type and concentration of halogenated hydrocarbons to be decomposed and type of polluted soil or groundwater.

(8) In one embodiment the B-ZVI alloy powder particles according to the present invention may have a particle size between 20 mm and 0.5 mm, preferably between 10 mm and 1 mm. Alternatively or in addition to this embodiment the particle size may be defined by the weight average particle size, X.sub.50, as measured by standard sieving according to SS EN 24497 or by laser diffraction according to SS-ISO 13320-1, being between 8 and 3 mm.

(9) In another embodiment a particle size between 0.5 mm and 10 μm, preferably 250 μm and 10 μm may be used. Alternatively or in addition to this embodiment the particle size may be defined by the weight average particle size, X.sub.50, as measured by standard sieving according to SS EN 24497 or by laser diffraction according to SS-ISO 13320-1, being between 150 μm and 20 μm. In a further embodiment, a particle size between 50 μm to 1 μm, preferably 30 μm to 1 μm may be used. Alternatively or in addition to this embodiment the particle size may be defined by the weight average particle size, X.sub.50, as measured according to SS-ISO 13320-1, by laser diffractometry, being between 20 μm and 5 μm.

(10) It may for certain applications be interesting to use coarser particle sizes which may be produced from finer particles and turned into coarser porous or non-porous particles, thereby forming aggregate(s), by known methods such as agglomeration, compaction and milling, heat treatment and milling, or compaction, heat treatment and milling. Examples of such known methods may be found in Metals Handbook, Ninth Edition, Volume 7, Powder Metallurgy, American Society for Metals, 1984, page 293-492, Consolidation of Metal Powders. Depending on the application, i.e. type of soil or fluid to be treated and type of contaminants, various mixes of B-ZVI alloy powder with known substances may be chosen in order to obtain optimal efficiency, forming a ZVI-B-alloy powder composition (also denominated as B-iron alloy powder composition or B-ZVI alloy powder composition). The particle size being determined by standard sieving according to SS EN 24497 or by laser diffraction according to SS-ISO 13320-1. The particle size intervals shall be interpreted as 80% or more, by weight of the particles being within the intervals.

(11) The B-ZVI alloy powder used may originate directly from atomization a molten-iron-boron alloy, e.g. from gas atomization or water atomization as described in Metals Handbook, Ninth Edition, Volume 7, Powder Metallurgy, American Society for Metals, 1984, page 25-30, Atomization. Alternatively the B-ZVI alloy powder may be produced through milling of an atomized iron-boron alloy or through milling solidified pieces of various size of an iron-boron alloy melt. Examples of milling operations are described in Metals Handbook, Ninth Edition, Volume 7, Powder Metallurgy, American Society for Metals, 1984, page 56-70, Milling of Brittle and Ductile Materials. In another embodiment of the first aspect of the present invention the B-ZVI alloy powder particles are dispersed in a carrier or thickener such as guar gum or carboxymethyl cellulose thus avoiding sedimentation of the particles and facilitating handling of the material, e.g. facilitating injection of a water dispersion containing B-ZVI alloy powder into polluted soil or aquifer. In one embodiment the thickener is guar gum solution at a concentration 0.1-10% by weight, preferably 0.1-6% by weight, in which the B-ZVI alloy powder composition is dispersed. It has also been shown that the presence of boron increases the viscosity of a guar gum based dispersion compared to a dispersion with similar material but without boron. This enables additions of lower amount of guar gum, thus decreasing the cost.

(12) In a second aspect of the present invention there is provided a method for remediation of polluted soil, water or groundwater. Pollution may be due to the presence of hydrocarbons (e.g. halogenated hydrocarbons such as e.g. chlorinated or boronated compounds, dyes, etc.), other organics, or metals. The method comprising the steps of providing a B-ZVI alloy powder or B-ZVI alloy powder composition according to the first aspect, contacting the B-ZVI alloy powder or B-ZVI alloy powder composition with the polluted soil water or groundwater by placing the B-ZVI alloy powder or B-ZVI alloy powder composition in a trench or in an aquifer in the polluted area, alternatively injecting the B-ZVI alloy powder or B-ZVI alloy powder composition into the polluted soil or aquifer, for a time sufficient to decompose the pollutants. In one embodiment of the method according to the present invention, the B-ZVI alloy powder or B-ZVI alloy powder composition will be allowed to remain in the soil or aquifer after the decomposition reactions have diminished or ceased. The B-ZVI alloy powder or B-ZVI alloy powder composition according to the invention may also be applied in material reactor type recipients, above ground or below ground level. The B-ZVI alloy powder or B-ZVI alloy powder composition according to the invention may also be applied in soilmixing.

(13) In a third aspect of the present invention there is provided the use of the B-ZVI alloy powder or B-ZVI alloy powder composition for remediation of soil or (ground)water polluted with halogenated hydrocarbons such as Chlorinated Aliphatic Hydrocarbon (CAH Other non-limiting examples of pollutants may be chlorinated ethenes comprising tetrachloroethylene (PCE), trichloroethylene (TCE) and cis-dichloroethylene (cDCE); the group of chloroethanes comprising 1,1,1,2 tetrachloroethane (1111 TeCE), 1,1,2,2 tetrachloroethenes (1122 TeCE), 1,1,1 trichloroethane (111-TCA), 1,1,2 trichloroethane and 1,1 Dichloroethane (11-DCA); the group of chloromethanes comprising chloroform, dichlorobromomethane; and the group of chlorinated propanes comprising 1,2,3-trichloropropane.

EXAMPLES

(14) The following examples illustrate the various aspects and embodiments of the present invention but shall not be interpreted as restricting the invention thereto.

(15) Various iron materials known in the art were chosen as reference materials and compared to the powders and compositions according to the invention. All materials were characterized with respect to particle size distribution, chemical analysis and specific surface area. Particle size distributions X10, X50 and X90 were measured according to SS-ISO 13320-1 by laser diffractometry with a HELOS laser diffraction sensor together with RODOS dispersing unit diffraction. The units X10, X50 and X90 represent the particles sizes—a percentage (10%, 50%, 90%) of the particles of the material is smaller than the indicated size. The focal lengths were R3 and R5. The trigger thresholds for start/stop conditions were 2%, respectively. The light scattering model was according to Fraunhofer. Dry dispersion was used, with an injection diameter of 4 mm, primary pressure was 3 bar. The dispersion unit was set up to reach an optical concentration between 5 to 15%.

(16) The specific surface areas were analyzed by single point measurement with a Micromeritics Flowsorb III instrument according to the BET method (Brunauer-Emmett-Teller method) using adsorption of N.sub.2 at the temperature of liquid N.sub.2. All the samples were degassed at 110° C. for 30 minutes before analysis.

(17) Chemical analysis was performed using standard analytical methods. The following Tablel shows characteristics of the materials used. Materials 1 to 3 are reference materials against which the compositions of the invention were benchmarked.

(18) TABLE-US-00001 TABLE 1 characteristics of materials used; Product name X10 X50 X90 BET B C O S N No (supplyer) [μm] [μm] [μm] [m2/kg] [%] [%] [%] [%] [%] 1 RNIP-10DS nano-iron 0.07* 4970* NA NA NA NA (TODA Kogyo Corp.) 2 HQ (BASF) 0.6 1.2 2.4 818 0.75 0.44 0.00 0.75 3 Atomized iron powder 22 41 62  94 0.00 0.09 0.01 0.00 (Höganäs) 4 Fe0.8B (Höganäs) 20 58 103  76 0.8 0.02 1.1 0.01 0.01 Fe1.5B 18 55 105 700 1.43 0.04 0.68 0.00 0.01 5 Fe3B (Höganäs) 2 30 59 515 3 0.28 1.86 0.00 0.00 6 Fe18B (Höganäs) 1 5 12 1098  18 0.01 0.71 0.00 0.00 *data from supplier; NA: not available

Example 1—Reactivity Tests

(19) The following examples show the capacity for degradation of some CAHs for the various materials according to Table 1. CAHs used were tetrachloroethylene (PCE), trichloroethylene (TCE), cis-dichloroethylene (cDCE) and 1,1,1 trichloroethane (111-TCA).

(20) All batch tests were prepared in 160 ml glass vials with butyl/PFTE grey septum containing 100 ml of anaerobic simulated groundwater and 60 ml of headspace, 5 g ZVI was added for samples 2 to 6 and 0.5 g for the nano-scale ZVI sample 1. Lower concentrations of nano-scale particles were selected due to their high reactivity. The simulated groundwater was spiked with approximately 5 mg/l of PCE, 5 mg/l of TCE, 5 mg/l of c-DCE and 5 mg/l of 111-TCA. The experiments were set up under anaerobic conditions and in triplicates. The vials were then placed for continuously gently mixing at 12° C. H.sub.2, CAHs, acetylene, ethane and methane were measured as start up (only blank) and after 14, 28, 49, and 105 days. CAH concentrations (including breakdown products) were measured using a GC-FID instrument (VARIAN).

(21) Hydrogen production at each sampling time was analyzed using a GC-TCD instrument (Interscinece). At each sampling time the redox potential and pH were measured using a redox/pH meter (Radiometer).

(22) The concentrations of PCE, TCE and c-DCE with respect to time are shown in Tables 2 to 4. Tables 5 and 6 show concentrations with respect to time of the breakdown products ethene and ethane.

(23) TABLE-US-00002 TABLE 2 Concentration of PCE [μg/l] DAYS 0 14 25 49 105 No Concentration μg/l PCE 1 RNIP-10DS 5000 2100 1400 1000 200 nano-iron 2 HQ 4000 300 50 0 0 3 Atomized 3600 1700 1000 500 0 iron powder 4 Fe0.8B 5300 1000 100 0 0 5 Fe1.5B 3700 1500 500 50 0 6 Fe3B 4600 1700 600 50 0 7 Fe18B 4600 1000 0 0 0

(24) TABLE-US-00003 TABLE 3 Concentration of TCE [μg/l] Days 0 14 25 49 105 No Concentration μg/l TCE 1 RNIP-10DS 5100 1600 700 400 100 nano-iron 2 HQ 4000 1500 400 0 0 3 Atomized 5100 1800 400 200 100 iron powder 4 Fe0.8B 5500 100 0 0 0 5 Fe1.5B 4300 400 20 0 0 6 Fe3B 4800 0 0 0 0 7 Fe18B 4800 0 0 0 0

(25) TABLE-US-00004 TABLE 4 Concentration of c-DCE [μg/l] Days 0 14 25 49 105 No Concentration c-DCE [μg/l] 1 RNIP-10S 5800 4800 4600 4400 3800 nano-iron 2 HQ 4000 2100 1300 900 500 3 Atomized 5700 5500 4900 3900 200 iron powder 4 Fe0.8B 5600 200 0 0 0 5 Fe1.5B 5000 700 0 0 0 6 Fe3B 4800 0 0 0 0 7 Fe18B 4800 0 0 0 0

(26) TABLE-US-00005 TABLE 5 Concentration of ethene [μg/l] Days 0 14 25 49 105 No Concentration ethene [μg/l] 1 RNIP-10DS 100 400 800 1000 1200 nano-iron 2 HQ 0 500 600 700 500 3 Atomized 0 300 600 800 700 iron powder 4 Fe0.8B 0 1300 800 400 100 5 Fe1.5B 0 1200 900 500 50 6 Fe3B 0 1000 500 200 0 7 Fe18B 0 50 0 0 0

(27) TABLE-US-00006 TABLE 6 Concentration of ethane [μg/l] Days 0 14 25 49 105 No Concentration ethane [μg/l] 1 RNIP-10DS 50 300 400 500 400 nano-iron 2 HQ 0 400 600 700 500 3 Atomized 0 500 600 800 1000 iron powder 4 Fe0.8B 0 1000 1300 1800 2000 5 Fe1.5B 0 750 1000 1800 1900 6 Fe3B 0 1100 1700 2300 2600 7 Fe18B 0 2700 2900 2900 3000

(28) As can be seen from the Tables 2 to 4 above, the boron containing materials according to the invention nos. 4 to 7, show a superior reactivity rate for reducing the contaminants TCE and c-DCE compared to the reference materials nos 1 to 3. The commercially available material no 2 (HQ, Carbonyl Iron Powder; BASF) shows a comparable reactivity rate related to decomposition of the contaminant PCE, when compared to the materials according to the invention. Tables 5 and 6 above show the concentration of the less harmful reaction products of the decomposition reactions, ethene and ethane. It can be noticed that the concentrations of ethene and ethane increase more rapidly for the materials according to the invention compared to the reference materials.

Example 2—Corrosion Rates

(29) During the decomposition of the pollutants according to Example 1 the various ZVI materials were partially consumed, but also the anaerobic water reacted with the ZVI materials was producing hydrogen. Thus a corrosion rate could be calculated for each ZVI material through measurement of the produced hydrogen. The following Table 7 shows the corrosion rate and life time for some of the ZVI materials in Example 1.

(30) TABLE-US-00007 TABLE 7 Corrosion rates [mol/(gs)] and Life time [years] Corrosion rate Life time No [mol/(gs)] [years] 1 RNIP-10DS 3.50*10.sup.−10 1.62 nano-iron 2 HQ 3.32*10.sup.−11 17.1 3 Atomized  2.1*10.sup.−11 26.3 iron powder 4 Fe0.8B 6.01*10.sup.−11 9.44 5 Fe1.5B 3.32*10.sup.−11 17.1 6 Fe3B 3.78*10.sup.−11 15.0 7 Fe18B 3.22*10.sup.−11 17.6

(31) As can be seen from Table 7 above, the materials according to the invention show life times in the same order as known microscale ZVI and considerably longer than the nano ZVI material 1.

Example 3

(32) Dechlorination rates of a number pollutants in the presence of the ZVI were calculated using the pseudo-first order rate equation; C=C.sub.0*e.sup.−kt, whereas C is the concentration at any time, C.sub.0 is the initial concentration, k is the first order decay constant [day-1] and t is the reaction time [days]. Half-lives were calculated as t½=ln 2/k [days]

(33) TABLE-US-00008 TABLE 8 Half-lives [days] for contaminants PCE, TCE, c-DCE and 1,1,1 TCA PCE TCE c-DCE 1,1,1 TCA t½ t½ t½ t½ No [days] [days] [days] [days] 1 RNIP-10DS 4.1 3.0 33 1.9 nano-iron 2 HQ 10.0 8.64 29.6 1.17 3 Atomized 16.7 16.0 24.9 4.68 iron powder 4 Fe0.8B 5.25 2.41 2.43 1.15 Fe1.5B 10.0 3.81 1.52 0.75 5 Fe3B 8.00 1.15 1.15 1.17 6 Fe18B 6.0 1.15 1.15 1.17

(34) The above table 8 shows that over-all half-lives for the pollutants PCE, TCE, c-DCE and 1,1,1 TCA treated with the material according to the invention, nos. 4 to 6, are considerably lower compared to pollutants treated with the comparative microscale materials, nos. 2 and 3. Only for PCE the known nanoscale iron (no. 1) shows better results.