Controlling and Recovering Oil Spills From the Environment

1. Field of Invention

This invention relates to a method for controlling and recovering oil spills from bodies of water and, in particular, for preventing oil contamination of shorelines.

2. Brief Statement of the Prior Art

The increasing demand of the industrial countries for energy sources has resulted in greatly accelerated shipments of imported oil and the increasing concern to protect the environment has greatly intensified the search for safe and efficient oil transportation. The threat of oil spills cannot be eliminated so long as industrial countries remain dependent on oil as an energy source, and this threat will be present for the foreseeable future. Sound management may minimize the frequency of the occurrences of oil spills, but will never completely eliminate them. An effective method of containment and recovery of oil spills from bodies of water such as rivers, lakes and seas is thus in urgent need.

Various techniques have been proposed for protection of coastlines from oil contamination resulting from spills of oil from tanker vessels. The current practice is to contain the oil with floating barricades. These techniques utilize floating booms which are interconnected to form a barricade against movement of the oil. Some techniques have been provided to skim the surface of the water to recover the oil. All of these techniques are not very effective. The surface of the water is usually too turbulent for efficient recovery and skimming operations and the oil slick often breaks through the various containment barriers which are erected. The oil emulsifies with the water, its volatile constituents evaporate, and a thick oily residue is formed on the water surface which defies recovery with conventional handling techniques and equipment. When that residue reaches a shoreline, it forms a tacky coating on all solid surfaces it contacts, and that coating is extremely difficult to remove. Following a major oil spill, which usually occurs near a shoreline, there is an unavoidable contamination of the coast with oil, at substantial peril to marine and aquatic life and requiring costly and labor intensive efforts for its removal.

Various materials have been suggested as absorbent for an oil slick. The best and most widely used absorbent is straw, and the news media has shown heroic efforts being made in attempts to absorb oil with straw. The results have been pitiful. Heretofore, no material has been provided which has the desirable, or even necessary, characteristics for this application. The materials which have been suggested do not absorb the oil and do not provide a non-sticky or dry adsorbate. Additionally, the materials are often of greater density than oil or water and will immediately sink away from the surface and the oil slick.

It is an object of this invention to provide a method for preventing the contamination of a shoreline with oil from an oil slick.

It is a further object of this invention to provide a simple and efficient method to absorb oil from an oil slick.

It is also an object of this invention to provide a method utilizing an absorbent which will absorb oil from water including sea water and form a dry composition.

It is an object of this invention to convert an oil slick on a body of water to a dry agglomerated powder.

It is further an object of this invention to provide a method for the recovery of oil from the surface of a body of water.

Other and related objects will be apparent from the following description of the invention.

This invention is a method for treatment of an oil slick resulting from an oil spill on a body of water. In the method, the oil slick is treated with a granular elastomeric composition comprising a block copolymer of styrene and an ethylene elastomer, particularly ethylene/butylene. The polymer structure can be a diblock or a triblock copolymer, however, the most preferred copolymer is a triblock copolymer which comprises an ethylene/butylene copolymer which has end blocks of polystyrene, thus providing an elastomeric middle block. The amount of styrene in the block polymer can be from 20 to about 40 percent; in the commercial triblock product which is most preferred, polystyrene is 29 percent of the triblock polymer. The polystyrene endblocks are mutually attracted, resulting in a "physical crosslinking" which, of course, decreases when an oil is absorbed by the triblock polymer.

The block polymers are available in various physical forms; solid pellet, porous pellet and powder. It is preferred to use the porous pellet form, as that form is more conducive to recover than the powder form, and the porous nature enhances oil absorption. The granular block polymer has a low density, typically from 14 to about 15 pounds per cubic foot. The specific gravity of the polymer is about 0.9, insuring that it will float on water and thus will remain at the location of the oil spill, and not separate as do clays and most inorganic absorbents. It will absorb oil and form a dry solid material which has a non-tacky and non-oily surface. The copolymer granular elastomeric composition is broadcast on the surface of an oil slick in proportions from about 0.2 to about 1 part per weight part of oil. The wave action on the body of water is generally sufficiently turbulent to admix the absorbent with the oil of the oil slick, resulting in the formation of floating solids which are dry to the touch and which have a non-oily, non-tacky surface. These solids can be readily recovered from the water or from a shoreline.

This invention comprises the treatment of an oil slick on a body of water with a unique absorbent which forms a dry, non-oily and non-tacky adsorbate when contacted with oil. The solid is broadcast or otherwise distributed across the surface of the body of water. This can be accomplished manually, from small boats when treating small to moderate sized oil slicks. In instances where the oil has spread over a wide area, the solid can be readily broadcast over the surface of the oil slick with conventional airplanes. The solid is distributed over the oil in weight proportions from 0.1 to about 1.5 parts per part of oil, preferably from about 0.25 to about 0.75 parts per part of oil.

The solid should be dispersed over the oil as quickly as possible, following the release of the oil on the surface of the water. As the oil is weathered by exposure to the sea and by evaporation, it will become less and less amenable to the treatment. Accordingly, it is preferred to treat the oil before it has weathered more than one day, and, most preferably within hours of the spill.

The particular material which is useful in the invention is available under the trade designation as Kraton G-1652 from the Shell Chemical Company, Houston, Tex. This material has a physical property similar to gum rubber and is an elastomeric block copolymer of ethylene and styrene. The material has a very low density, typically from 14 to about 15 pounds per cubic foot and is available in a granular state, typically having a particle size with an average particle size from 700 to 1000 microns average diameter. It is known as a modifier for oils and has been mixed with oils at elevated temperatures to prepare mixtures which gel upon cooling, typically forming greases, or when used at low concentrations, to modify the viscosity of oils.

The absorption of the oil by the elastomeric gum absorbent proceeds quite rapidly and complete absorption will be achieved within about 10 to 15 minutes and in no instance later than approximately 1 hour after the treatment. Although wave action on the surface of the body of water will aid dispersion and contacting, such agitation is not required. The absorption is so effective that it proceeds rapidly even with quiescent bodies of water. This absorption efficiency is believed to result from the high absorbency and low density of the particular elastomeric gum polymer.

After contacting of the absorbent with the oil slick, the resulting dry solid adsorbate floats on the surface of the water and can be easily recovered. Preferably, the powder is contained and collected with conventional floating oil booms and is skimmed from the surface of the water with skimming barges or other equipment. The adsorbate is much more susceptible of recovery as its surface is dry and free of oily or tacky properties. Accordingly, the skimming and recovery equipment does not become clogged with oil crusts or oil deposits.

In the event that any of the solid adsorbate is washed onto a beach or shoreline, it can be readily removed since it is free flowing and does not stick or adhere to sand, rocks and the like. Accordingly, it can readily be recovered by sweeping or vacuuming of the shoreline.

The following examples will illustrate the practice of the invention and demonstrate results obtainable thereby.

In the following series of experiments, a 750 milliliter sample of the selected water was placed in a glass vessel, and approximately 70 to 100 milliliters of the selected oil were poured onto the water. Thereafter, the indicated quantity of the solid absorbent was added. In each experiment, the vessel contents were permitted to stand in a quiescent state and the condition of the liquid was noted during the experiment.

In the first experiment, seawater was placed in the vessel, 70 milliliters of crude oil was poured onto the seawater and thereafter the solid dispersant (Kraton G-1650D) was scattered on the surface of the oil floating on the water. After a period of five minutes it was noted that all of the oil had been completely absorbed onto the solid absorbent and the seawater was clear and free of oil, with a dry solid and granular adsorbate floating on its surface. The solid was readily removed from the surface of the seawater as a dry solid which left no oily residue on one's hands. The seawater after separation of the solid absorbent was clear and exhibited no residue of the crude oil.

The procedure of Example 1 was repeated using fresh water and the same results were observed.

The procedure of Example 1 was repeated using gasoline rather than crude oil. The solid adsorbate which was formed congealed into a homogeneous crust in which the individual particles of the solid absorbent were consolidated into a thin brown-colored solid which could be readily picked up off the surface of the water.

The procedure of Example 1 was repeated using a lubricating oil of 10/30 weight designation. Again, the same results were observed and the water was entirely purified of oil by treatment with the solid absorbent.

The procedure of Example 1 was repeated using a commercial oil absorbent (Oil Absorbent marketed by 3M Occupational Health and Safety Products Division). The material absorbed most, but not all of the oil, and a visible oil slick remained on the water surface following treatment.

The procedure of Example 1 was repeated using various solid absorbents, including ground corn cobs, clays, silicates. In all cases, these absorbents failed to absorb all the oil, and in most cases, a considerable quantity of oil remained on the surface of the water after removal of the solid absorbent.

The procedure of Example 1 was repeated using another Kraton rubber product; Kraton 1101D, which is a thermoplastic elastomeric styrene-butylene-styrene triblock copolymer. The material absorbed most, but not all of the oil, and a visible oil slick remained on the water surface following treatment. Additionally, the solid removed from the water had an oily and tacky surface, and left a residue of oil on surfaces which it contacted.

The invention has been described with reference to the illustrated and presently preferred embodiment. It is not intended that the invention be unduly limited by this disclosure of the presently preferred embodiment. Instead, it is intended that the invention be defined, by the means, and their obvious equivalents, set forth in the following claims: