Liquid purification or separation – Processes – Ion exchange or selective sorption
Reexamination Certificate
1999-09-03
2003-01-14
Cintins, Nars (Department: 1724)
Liquid purification or separation
Processes
Ion exchange or selective sorption
C210S691000, C210S924000
Reexamination Certificate
active
06506307
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates generally to the use of a fibrous material to sorb liquids. Particularly, this invention relates to the use of processed, naturally hydrophobic tropical fibers such as banana, plantain, cavendish plant, pineapple, coconut, and palm, to recover spilled oil, gasoline, kerosene, solvents, hydrocarbons, pentachlorophenol (PCP), creosote or other liquids.
2. Description of the Prior Art
Spills of oil, solvents and hazardous materials are a continuing problem having serious environmental consequences, including damage to the oceans, beaches, inland rivers, streams and creeks, as well as detrimental effects upon the health of wildlife and humans. The need for oil and chemical products has created consistent growth in the chemical industry, including the transport and manufacturing of these compounds, resulting in increasing environmental problems associated with spills, accidents and improper disposal.
Sorbent materials, including both materials that absorb and materials that adsorb, have been used for many years in the cleanup of oil and hazardous materials by private industry and the federal government. Sorbent clay materials are currently the material of choice for absorbing or recovering oil or other hazardous chemicals on land. In industrial applications, these materials have the disadvantages of low sorbent capacity and a high density which make them both heavy and difficult to transport. Additionally, the abrasiveness and friability of these products may lead to increased wear of nearby industrial machinery. These clay based sorbents are not biodegradable and, therefore, pose an additional environmental problem because they must be disposed of in the limited space available in landfills. Peat, diatomaceous earth and vermiculite are sometimes used as alternatives to the clay based sorbents.
The primary sorbents used in remediation of spills of oil or other hazardous substances on water consist of synthetic materials such as polypropylene, which is currently the product of choice for industry and remediation specialists. However, since polypropylene is itself a synthetic chemical, its production handling can be the source of other environmental problems. Additionally, because these synthetic sorbents are not biodegradable and currently must be disposed of in landfills, they increase the load on the limited available landfill capacity. Therefore, a need exists for an efficient natural sorbent material which is not a source of environmental problems.
One process for alleviating the environmental problems associated with the production of oil or chemical sorbent materials is to use a sorbent system based on natural fibers. Over the last several decades, a wide variety of treated natural fibers have been used as sorbents of hazardous materials. These have included tree bark, peat, wood fiber, dealginate kelp, powdered lily, kenaf cores, puffed cereals, and a variety of other cellulosic materials. Each of these fiber types has disadvantages which have prevented them from becoming the material of choice for remediation of oil and chemical spills on land or in water.
The primary disadvantage of most of these fiber types is that they are naturally hydrophilic and, therefore, tend to sorb large quantities of water. Sorption of water increases the weight of these materials and can seriously decrease their ability to sorb the oil or hazardous chemical which these materials are intended to recover. It is possible to reduce or eliminate the tendency of some of these materials to sorb water by treatment with chemical additives to increase their hydrophobicity.
For example, in U.S. Pat. No. 5,021,390, Hatton teaches a composition for sorbing liquids consisting of various fibrous plant materials treated with the waterproofing agent sodium methyl silicate. In U.S. Pat. No. 5,492,881, Diamond teaches a sorbent system using finely ground cellulose treated with a hydrophobic agent such as paraffin, other waxes, polyvinyl alcohol, hydroxyethyl cellulose or the like. In U.S. Pat. No. 4,172,794, Akiyama discloses an oil absorbent composition made from a vegetable material, such as coconut husk, which has been impregnated with a hydrophobic-oleophilic substance such mineral oil, naphtha, kerosene, light oil, paraffin, or various other similar oils and fatty substances. In U.S. Pat. No. 4,072,039, Tomita et al. disclose an oil absorbent material comprising natural fibers, such as grass peat, coconut husk, or jute, which have been coated with a water-repellent, hydrophobic layer of paraffin and an elastic layer of latex. In each of these cases, hydrophobic additives must be used to make the fibers suitable for use as an oil sorbent material, adding to the manufacturing expense of the sorbent material and potentially further harming the environment.
Another disadvantage of previously disclosed natural fiber based sorbents is that most are generally only capable of sorbing 5-10 times their mass in oil or other chemicals. Additionally, most of these natural fiber compositions have a tendency to sink as they become saturated with oil, water or other chemicals, making recovery of these materials and sorbed chemical from a body of water extremely difficult or impossible.
Several of the previously disclosed fiber compositions are not readily biodegradable and therefore pose an additional environmental problem since these fibers will not easily degrade when disposed of in a landfill. For example, in U.S. Pat. No. 3,791,990, Fischer et al. teach an oil sorbent material composed of peat fibers dried to less than 10% by weight water. These fibers are not biodegradable, which, although beneficial from the stand point of reducing leaching of the liquids, results in a long lifetime in landfills. Overuse of the limited landfill capacity is a major environmental problem, and it is therefore desirable to provide a sorbent material which is readily biodegradable after use and recovery of the oil, solvent or other liquids.
Agricultural waste products also constitute an environmental problem. For example, banana stalks, plantain stalks, cavendish plant stalks, pineapple crowns, palm, palmetto and coconut fronds, and a variety of other tropical plant portions are presently thought of as waste agricultural byproducts in the countries in which they are produced. Currently these byproducts are disposed of in landfills, where they can attract insects and contribute to landfill capacity problems. Additionally, they may be discarded into rivers, where they oxidize and can cause potential environmental problems. In other instances, the byproducts are left on the ground to act as a natural fertilizer. Therefore, it would be beneficial to find a use for these agricultural byproducts products rather than disposing of them as waste.
Many of these tropical plant waste materials include a substantial content of naturally hydrophobic fibers. Accordingly, one potential use for these materials is as a source of fibers to be used as an oil sorbent material. Unfortunately, in their natural state, these plant materials also include a high content of natural liquids which permeate the fibers, making them impractical for use in oil sorbent applications.
Accordingly, it is an object of the present invention to provide a process for sorbing liquid environmental contaminants such as spilled oil, kerosene, gasoline, solvents, hydrocarbons, PCP, and creosote.
Furthermore, it is an object of the present invention to provide a process for converting agricultural byproducts into fibers useful for sorbing liquid environmental contaminants.
It is yet another object of the present invention to provide a process for sorbing liquid environmental contaminants which minimizes the use of toxic or potentially environmentally harmful chemicals.
SUMMARY OF THE INVENTION
The above objectives are accomplished according to the present invention by providing a process for sorbing a hydrophobic liquid. In the present process, a plurality of dried, washed fibers are provided, which originate from a t
Bergquist-Kingham Katherine Tracy
Hondroulis Dimitrios George
Kingham Neville William
Boss Gerald R.
Cintins Nars
Fybx Enviromental, Inc.
Troutman Sanders LLP
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