Porous oil binder and method for the production thereof

Abstract

The invention relates to a hydrophobed porous oil binder in the form of a nonwoven fabric composed of lignocellulose-containing raw materials having a biologically functionalized surface for removing mineral-oil-based contaminants in seas, rivers, inland waters, and stormwater basins or wastewater treatment plants, wherein the density of the oil binder is 10 to 900 kg/m.sup.3, the oil binder is 1 to 25 mm thick, the broad surface of the oil binder has a dimension of 9 to 200 cm.sup.2, the porosity of the oil binder is 30 to 96%, measured with respect to the total fraction of the oil binder, and the flexural strength of the oil binder is at least 1.5 N/mm.sup.2.

Claims

1. A porous oil sorbent in the form of a nonwoven material, comprising fibres formed from lignocellulosic raw materials, wherein: a) the density of the oil sorbent is 80 to 300 kg/m.sup.3, b) the oil sorbent is 3 to 6 mm thick, wherein thickness of the oil sorbent refers to the length of the shortest edge of the oil sorbent, c) the large surface of the oil sorbent has a dimension of 9 to 200 cm.sup.2, d) the pore fraction of the oil sorbent is 30% to 96%, wherein the pore fraction is determined in accordance with DIN EN 310, and e) the bending strength of the oil sorbent is at least 1.5 N/mm.sup.2, wherein the bending strength is determined using DIN EN 310.

2. The oil sorbent according to claim 1, wherein the oil sorbent comprises hydrophobized fibres, wherein the fibres are hydrophobized with natural or nature-identical additives, wherein natural or nature-identical additives are paraffins, waxes, synthetic or natural latex, bark extracts, tannins or mixtures thereof.

3. The oil sorbent according to claim 1, wherein the lignocellulosic raw materials are obtained from wood, grain, flax, rape, rice or cotton straw, coconut fibres, bagasse, bamboo, cork, seaweed, tree bark or mixtures thereof.

4. The oil sorbent according to claim 1, wherein the lignocellulosic raw materials contained in the oil sorbent are in the form of partially degraded lignocellulosic raw materials due to thermal modification, wherein the partial degradation due to thermal modification is achieved in the absence of air and/or in a nitrogen atmosphere in an autoclave in a temperature range of 160 C. to 260 C., wherein the lignocellulosic raw materials absorbs less water due to the thermal modification.

5. The oil sorbent according to claim 1, wherein the oil sorbent further comprises animal-based raw materials in a proportion by weight in the range 5% to 15% by weight, wherein animal-based raw materials are wool, feathers or leather, or mixtures thereof.

6. The oil sorbent according to claim 1, wherein the fibre surface further comprises a natural or synthetic binder, wherein the natural or synthetic binder are starches, proteins, urea resins, isocyanates or mixtures thereof.

7. The oil sorbent according to claim 1, wherein the moisture content of the oil sorbent is 5% to 20% by weight, measured as the dry matter content of the fibrous material after it has been dried to constant weight.

8. The oil sorbent according to claim 1, wherein the surface of the fibres or the oil sorbent further comprises immobilized microorganisms, wherein oil-degrading microorganisms are immobilized by a spraying or dipping method on the surface of the fibres of the nonwoven material which has been hydrophobized.

9. The oil sorbent according to claim 8, wherein the microorganism community consists of alkanotrophic bacteria of the genera Rhodococcus, Pseudomonas and Sphingomonas as well as phototrophic algae and cyanobacteria from the genera Microcoleus, Phormidium, Lyngbya, Oscillatoria and Anabaena.

10. The oil sorbent according to claim 1 further comprising lyophilised microorganisms or microorganisms in suspension, wherein lyophilised microorganisms or microorganisms in suspension are added during the production of the oil sorbent and/or prior to use of the oil sorbent.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) Accordingly, the object of the invention is achieved by means of a porous oil binder in the form of a nonwoven material, consisting of fibres formed from lignocellulosic raw materials. The oil binder has the following features: a) the density of the oil binder is 10 to 900 kg/m.sup.3, preferably 80 to 300 kg/m.sup.3, particularly preferably 220 to 290 kg/m.sup.3. b) the oil binder is 1 to 25 mm, preferably 3 to 6 mm, particularly preferably 3.5 to 4.5 mm thick. c) the large surface of the oil binder has a dimension of 9 to 200 cm.sup.2, preferably a dimension of 25 to 100 cm.sup.2, particularly preferably in the range 25 to 30 cm.sup.2. d) the pore fraction of the oil binder is 30% to 96%, preferably 80% to 90%, measured over the entirety of the oil binder. e) the bending strength of the oil binder is at least 1.5 N/mm.sup.2.

(2) Surprisingly, it has been shown that oil binders which are used with a degree of coverage of at least 10% obtain a clean-up percentage in the range 10% to 100%, preferably 80%. Advantageously, the oil absorption due to the construction of the oil binder is in the range 100 to 700 kg/m.sup.3, preferably in the range 400 to 600 kg/m.sup.3, wherein after absorbing oil from the environment, an oil binder advantageously has a buoyancy on the surface of the water of at least 3 days, preferably at least 7 days. More advantageously, after absorbing oil from the environment, by producing an overpressure of up to 0.1 bar on the oil binder, the oil binder of the invention does not release any oil. The oil retaining power of the oil binder at an overpressure of 0.1 bar was checked using the LTwS-No 27 guidelines known to the person skilled in the art (Storage and Transport of Water-polluting Substances from the Federal Ministry Advisors on the Environment, Natural Protection and Reactor Safety, issued by the Environmental Agency).

(3) In the context of the invention, oil means all of the usual types of oil, such as crude oil, light oil and heavy oil.

(4) The term density of the oil binder should be understood to mean the mass of the oil binder in kg with respect to its volume in m.sup.3.

(5) The thickness of the oil binder refers to the length of the shortest edge of the oil binder.

(6) The large surface of the oil binder as used in the context of the invention is the area of the oil binder which comes into contact with the water or oil.

(7) The pore fraction of the oil binder describes the volume available for oil absorption with respect to the total volume of the oil binder and was determined in accordance with DIN EN 310, which is familiar to the person skilled in the art. The pore fraction in the context of the invention consists of the voids in the lumen (void in a cell enclosed by the cell wall) of the wood fibres or wood cells and the voids which lie between the wood fibres in the oil binder. The volume of the intermediate fibre voids correlates with the density of the oil binder.

(8) The oil binders have a higher bending strength in order to meet the challenges of deployment and recovery. The bending strength of the oil binder is determined using DIN EN 310, which is known to the person skilled in the art.

(9) The porous oil binder in the form of a nonwoven material may be in the form of flat structures of various shapes, such as polygonal, rectangular, square, round or oval, preferably rectangular.

(10) Preferably, the primarily rectangular structures have a length of side of 10 cm, particularly preferably 5 cm. The length of side in this regard refers to the two longest sides of the rectangular structure.

(11) The invention also concerns a porous oil binder in the form of a nonwoven material, consisting of hydrophobic fibres formed from lignocellulosic raw materials, which are wetted with natural and/or nature-identical additives as hydrophobizing agents and have the following features: a) the density of the oil binder is in the range 10 to 900 kg/m.sup.3, preferably in the range 80 to 300 kg/m.sup.3, particularly preferably in the range 220 to 290 kg/m.sup.3. b) the thickness of the oil binder is in the range 1 to 25 mm, preferably in the range 3 to 6 mm, particularly preferably in the range 3.5 to 4.5 mm. c) the large surface of the oil binder has a dimension of 9 to 200 cm.sup.2, preferably a dimension of 25 to 100 cm.sup.2, particularly preferably in the range 25 to 30 cm.sup.2. d) the pore fraction of the oil binder is in the range 30% to 96%, preferably in the range 80% to 90%, measured over the entirety of the oil binder. e) the bending strength of the oil binder is at least 1.5 N/mm.sup.2.

(12) Preferably, the oil binder comprises hydrophobic fibres formed from lignocellulosic raw materials.

(13) Preferably, the lignocellulosic raw materials consist of wood, grain, flax, rape, rice or cotton straw, coconut, bagasse, bamboo, cork, seaweed, tree bark or mixtures thereof. Seaweed, which occurs on beaches as flotsam, is preferred. Conifers are particularly preferred.

(14) The lignocellulosic raw materials are present in the oil binders in the form of fibres which have a length of 0.1 to 6 mm in the context of the invention. With oil binders formed from coniferous nonwoven materials, the conifer fibres have a length of 0.5 to 4.0 mm.

(15) In a particular embodiment of the invention, the lignocellulosic raw materials are thermally modified. The person skilled in the art will know of various methods for thermally modifying wood fibres. As an example, the wood fibres or the wood are treated prior to milling in the absence of air and/or in a nitrogen atmosphere in an autoclave in a temperature range of 160 C. to 260 C. Advantageously, the wood fibres absorb less water due to the thermal modification.

(16) Preferably, the slenderness ratio of the fibres is 0.5 to 5, particularly preferably 1.0 to 4, more particularly preferably 1.5 to 3, wherein in particular long, slim fibres are advantageous since these have a positive effect on the strength of the oil binder. The term slenderness ratio as used in the context of the invention is understood by the person skilled in the art to mean the ratio of the length of the fibres to the diameter of the fibres (Wood Technology Dictionary, 4.sup.th edition, Leipzig Specialist Publishers, 1990, p 640).

(17) The oil binder of the invention has various pore sizes; advantageously, various types of oils can thus be absorbed.

(18) Furthermore, it is advantageous for the high pore fraction to result in a large specific surface area for the oil binder, whereupon the oil absorption due to adhesion is accelerated.

(19) Preferably, the oil binder may comprise animal-based raw materials in a proportion by weight in the range 5% to 15% by weight, particularly preferably in the range 8% to 12% by weight. Preferably, the animal-based raw materials are wool, feathers or leather, or mixtures thereof.

(20) The combination of lignocellulosic raw materials and animal-based raw materials results in an improved/accelerated oil absorption into the oil binder. Particularly volatile fractions of the oil mixture can be absorbed faster due to the high affinity of the animal-based raw materials.

(21) In a particular embodiment of the invention, the fibres are hydrophobized with natural or nature-identical additives such as paraffins, waxes, synthetic or natural latex, bark extracts, tannins, particularly preferably tannic acid or mixtures thereof. Preferably, the tannins are obtained from wood and/or bark of a quebracho tree and/or an oak.

(22) Surprisingly, it has been shown that the oil absorption in the oil binder in accordance with the invention, because the fibres have been hydrophobized, is much faster than the absorption of water. In moving water, up to 99% by weight of the oil has been absorbed after just 10 to 15 min, while the absorption of water takes several days to weeks. More advantageously, the buoyancy of the oil binder fully loaded with oil is improved by hydrophobizing the surface of the fibre or the oil binder.

(23) Preferably, the fibre surface is wetted with a natural or synthetic binder such as starches, proteins, urea resins, isocyanates or mixtures thereof.

(24) Advantageously, the strength of the oil binder is improved by the binder.

(25) Advantageously, the moisture content of the oil binder of the invention is 5% to 20% by weight, particularly preferably 8% to 15% by weight, measured as the ATRO weight of the fibrous material.

(26) The person skilled in the art will be familiar with the term ATRO which describes the dry matter content of the solid after it has been dried to constant weight.

(27) The term moisture content is understood by the person skilled in the art to mean the moisture which the oil binder contains when stored in the respective prevailing climate.

(28) Preferably, the surface of the fibre or the oil binder comprises immobilized microorganisms.

(29) Preferably, the microorganisms consist of microorganism communities from alkanotrophic bacteria of the genuses Rhodococcus, Pseudomonas and Sphingomonas as well as phototrophic algae and cyanobacteria from the genuses Microcoleus, Phormidium, Lyngbya, Oscillatoria and Anabaena.

(30) In a preferred variation, a microorganism community consisting of oil-degrading microorganisms with a phototrophic partner, for example algae or cyanobacteria, is used. These form a biocoenosis, in which the algae produce molecular oxygen for the heterotrophic oil-degrading bacteria and thus prevent oxygen limitation of the bacteria.

(31) Preferably, lyophilized microorganisms accompany the oil binder in accordance with the invention, which microorganisms are suspended just before use in a liquid, preferably water, and then are immobilized on the oil binder.

(32) In accordance with the invention, the buoyant porous oil binders in the form of a nonwoven material for an accelerated degradation or removal of oil contamination from the surface of water in marine environments, rivers, inland waters and also storage reservoirs or wastewater treatment plants are produced by a wet method or by a dry method.

(33) The wet method comprises the following steps: a) producing fibres from lignocellulosic raw materials by thermal, hydrothermal, mechanical, thermomechanical or chemical digestion methods, b) isolating and suspending the fibres in a mixing tank with water, c) adding a hydrophobizing agent and mixing, d) shaping, dewatering and drying a nonwoven material, e) shaping the dried nonwoven material,

(34) wherein the proportion of fibre in the suspension is 0.5% to 4.5% by weight, particularly preferably 2.5% to 3.5% by weight measured as the total weight of the suspension.

(35) In accordance with the invention, a nonwoven material formed from lignocellulosic raw materials is produced. The lignocellulosic raw materials may be milled into fibres using thermal, hydrothermal, mechanical, thermomechanical or chemical digestion methods such as milling or comminuting methods.

(36) Pre-dewatering of the suspension and shaping of the nonwoven material are carried out by introduction into a screen of a desired size. By pressing, the nonwoven material which is obtained is dewatered further and calibrated to the desired thickness and density and then dried in a dryer. Larger nonwoven materials are then separated into small sheets of the desired size.

(37) Advantageously, the density and bending strength of the oil binder can be adjusted by the size of the screen and the proportion of solid matter in the suspension. The person skilled in the art will be aware of how to select the proportion of solid matter and the screen size in order to obtain a specific density and bending strength.

(38) The dried nonwoven materials are shaped using methods known to the person skilled in the art, for example by cutting or sawing the nonwoven materials into the desired shape.

(39) The dry method comprises the following process steps: a) producing fibres from lignocellulosic raw materials by thermal, hydrothermal, mechanical, thermomechanical or chemical digestion methods, b) drying the fibres, c) sizing and/or wetting the fibres with a natural or synthetic binder and/or a hydrophobizing agent, d) forming a nonwoven material by pneumatic or manual spreading of the sized and/or wetted fibres, e) pressing and hardening the nonwoven material.

(40) In accordance with the invention, a nonwoven material is thus produced from lignocellulosic raw materials. The lignocellulosic raw materials are processed into fibres using thermal, hydrothermal, mechanical, thermomechanical or chemical digestion methods.

(41) After digestion, the fibres are dried.

(42) In accordance with a particular embodiment of the invention, natural or nature-identical additives such as paraffins, waxes, synthetic or natural latex, bark extracts, tannins, particularly preferably tannic acid or mixtures thereof are added to the fibres. Preferably, the tannins added are from wood and/or bark from a quebracho tree and/or an oak tree.

(43) Optionally, after drying, natural or synthetic binders such as starches, proteins, urea resins or isocyanates, or mixtures thereof, may be added to the fibres.

(44) Preferably, the natural binders starch and proteins are added in a proportion of 2% to 40% by weight, particularly preferably 5% to 30% by weight with respect to the ATRO weight of the fibrous material.

(45) Preferably, urea resins are added in a proportion of 5% to 18% by weight, particularly preferably 8% to 12% by weight with respect to the ATRO weight of the fibrous material.

(46) Preferably, isocyanates are added in a proportion of 1% to 10% by weight, particularly preferably 2% to 8% by weight with respect to the ATRO weight of the fibrous material.

(47) A nonwoven material is formed by pneumatic or manual spreading of the sized and/or wetted fibres to the desired dimensions.

(48) The nonwoven material is pressed to the desired thickness and hardened.

(49) Larger nonwoven materials are separated into smaller flat structures with various shapes and the desired dimensions, examples of which are polygonal, rectangular, square, round or oval, Rectangular structures are preferred.

(50) Preferably, the rectangular structures have a length of side of 10 cm, particularly preferably 5 cm, in this regard, length of side refers to the two longest edges of the rectangular structure.

(51) Preferably, the lignocellulosic raw material used is wood, seaweed, tree bark, grain, flax, rape, rice or cotton straw, coconut fibres, bagasse, bamboo, cork or mixtures thereof. Preferably, seaweed, which occurs as flotsam on beaches, is used. Particularly preferably, coniferous wood is used.

(52) Preferably, animal-based raw materials in a proportion by weight in the range 10% to 15% by weight, particularly preferably in the range 8% to 12% by weight with respect to the total weight of the oil binder, are used. Preferably, wool, feathers or leather, or mixtures thereof, is used as the animal-based raw material.

(53) Preferably, the natural binders such as starches and proteins are added in amounts in the range 2% to 40% by weight, particularly preferably in the range 5% to 30% by weight with respect to the ATRO weight of the fibrous material.

(54) Preferably, oil-degrading microorganisms are immobilized by a spraying and dipping method on the surface of the fibres of the nonwoven material which has been hydrophobized.

(55) Preferably, alkanotrophic bacteria from the genuses Rhodococcus, Pseudomonas and Sphingomonas as well as phototrophic algae and cyanobacteria from the genuses Microcoleus, Phormidium, Lyngbya, Oscillatoria and Anabaena are employed.

(56) Immobilisation is carried out during the production or prior to use of the oil binders.

(57) Preferably, for immobilisation, microorganisms which are still lyophilized or in suspension are added during the production of the oil binder and/or prior to use of the oil binder.

(58) The binders obtained act both as a support material for immobilising oil-degrading microorganism communities and also to absorb the oil after deployment. For the accelerated degradation of the oil absorbed by the support material, during production and/or prior to deploying the oil binder material, oil-degrading microorganism communities are immobilized on the surface and/or in the pores of the support material. The microorganisms may be immobilised during or after production of the oil binder, or just before use. On the one hand, oil binders of this type are produced by immersing the nonwoven material in tanks containing microorganisms or by spraying the nonwoven material with oil-degrading microorganisms. On the other hand, in order to ensure a longer storage time (survival), the retained microorganisms are suspended in and applied from an aqueous solution shortly before being used at the scene of the incident.

(59) The oil binders of the invention are provided for the degradation or removal of oil contamination from the surface of the water in seas, rivers, inland waters as well as storage reservoirs or wastewater treatment plants.

(60) By using biogenic, biologically degradable oil binders, the contamination of bodies of water into which the binder is deployed, is reduced or prevented. Inexpensive residual material is used as the support material.

(61) The oil binders can be deployed rapidly both with and without microorganisms using traditional shipping and fishing technology, but also from an aircraft in the region of the oil contamination in the water. In this manner, they can also be used in regions with shallow waters, as well as under difficult weather conditions.

(62) The oil binders are distributed in the region of the oil contamination in the water with a coverage of at least 10%. Surprisingly in this regard, the oil is absorbed to saturation point within a few minutes because of the low density of the oil and the high porosity of the binder while, because of the hydrophobic nature of the fibre, water is absorbed much more slowly, over several days to weeks. In this manner, a clean-up rate for the water surface of more than 80% can be obtained even with a low coverage of only 10%. Absorption of the oil by the oil binder material prevents further contamination of the body of water and the coast and reduces the danger to water birds. In this regard, the oil binder has a buoyant on the water surface which lasts several days.

(63) After absorbing the oil, the loaded oil binder is simply removed from the water using nets and sent for thermal processing.

(64) When loaded oil binders remain in the body of water because of inclement weather conditions or are washed up on inaccessible coasts, the microorganism community can get to work. In a preferred variation, a microorganism community is used which consists of oil-degrading microorganisms with a phototrophic partner, for example algae or cyanobacteria. These form a biocoenosis in which the algae produce molecular oxygen for the heterotrophic oil-degrading bacteria, and thus oxygen limitation of the bacteria is avoided.

(65) Growth is stimulated by contact with the water or oil, the microorganisms colonize the oil film and start to degrade it. Advantageously, microorganisms are used which are suitable for the environmental conditions of the scene of operations. The microorganism community introduced with the oil binder material can accelerate colonization and degradation of the oil contamination by several weeks and months. Degradation of the chemically harmless support material is also carried out with the help of microorganisms which colonise the support material after or during degradation of the toxic oil residues. As a result, the burden on the environment is substantially reduced.

EXAMPLES

(66) The invention will now be explained in more detail with the aid of the following examples.

Example 1a: Production of Oil Binder Material with Latex and Paraffin

(67) Spruce wood chips were processed into fibrous material by thermomechanical milling and a suspension with a solid matter content of 3% by weight was produced therefrom in a mixing tank. The suspension was supplemented with 7% latex milk and 2% paraffin (ATRO fibre solid weight) and it was stirred at 60 C. for approximately 20 min. Al.sub.2(SO.sub.4).sub.2 was added to precipitate it out and the suspension was dewatered using a screen with a vacuum of 0.8 bar. The 4 mm thick nonwoven material was calibrated and dried at 180 C. to a residual moisture content of 8%. The nonwoven material which was produced had a bulk density of 280 kg/m.sup.3 and was divided into oil binders with a 55 cm length of side. The porosity of the binder was 80% by weight, measured with respect to the entirety of the oil binder (measured with a helium pycnometer in accordance with DIN 51913). The bending strength was 1.98 N/mm.sup.2 (in accordance with DIN EN 310).

Example 1b: Production of Oil Binder Material with Natural Latex

(68) Spruce wood fibres were softened in water at a temperature of 50 C. (solids content 3%). Next, 7% of natural latex in a solution was added to the suspension of fibrous material with continuous stirring. Al.sub.2(SO.sub.4).sub.3 was added to the suspension to precipitate it out. Next, the suspension was processed further as described in Example 1a. The bulk density of the oil binder was 265 kg/m.sup.3 and the porosity was 81% by weight measured with respect to the entirety of the oil binder. The bending strength was 1.96 N/mm.sup.2 (in accordance with DIN EN 310).

Example 1c: Production of Oil Binder Material with Tannin

(69) Spruce wood fibres were softened in water at a temperature of 50 C. (solids content 3%). Next, 5% of quebracho tannin in a solution was added to the suspension of fibrous material with continuous stirring. Al.sub.2(SO.sub.4).sub.3 was added to the suspension to precipitate it out. Next, the suspension was processed further as described in Example 1a and 1b. The bulk density of the oil binder was 279 kg/m.sup.3 and the porosity was 80% by weight. The bending strength was 1.97 N/mm.sup.2 (in accordance with DIN EN 310).

Example 2: Use of Material as an Oil Binder

(70) 50 g of crude oil was measured into individual Petri dishes. 11 g (40 cm.sup.3) of the oil binder material from Examples 1a, 1b and 1c were added thereto. After 1 min, in each case the oil binder material had absorbed approximately 27 g of oil (approximately 2.5 times its own weight).

Example 3: Use of Oil Binder in Oil/Water Mixture and Long-Term Buoyancy

(71) 1.5 L of water was placed in a container of a shaker. 22.5 g of crude oil (0.3 mm oil layer thickness) and 11 g of oil binder (from Example 1a) with a volume of 40 cm.sup.3 was added, corresponding to a coverage of 11%. The container was moved at a frequency of 0.5 Hz. In the first 15 minutes, the increase in weight was measured every 5 min, and thereafter every 10 min. After 10 min, the binder had absorbed an oil/water mixture of 22 g, corresponding to a volume of approximately 600 kg/m.sup.3. After a further 80 minutes, a total of 25 g of oil/water mixture had been absorbed. An analysis of the residual water content in the container (separating funnel) showed that 18.41 g of oil and only 7.31 g of water had been absorbed by the binder. This corresponded to an oil uptake of approximately 660 kg/m.sup.3 and a clean-up percentage of approximately 85%. The binders floated for a further 14 days in the shaker tank before the test was stopped.

(72) The test was also carried out with oil binders in accordance with Examples 1b and 1c, wherein the oil uptakes were similar to those with the oil binders of Example 1a and the buoyancy was retained for at least 8 days.