Cleaning and liquid contact with solids – Processes – Using sequentially applied treating agents
Reexamination Certificate
1999-10-22
2001-08-28
Einsmann, Margaret (Department: 1751)
Cleaning and liquid contact with solids
Processes
Using sequentially applied treating agents
C134S019000, C405S128350
Reexamination Certificate
active
06280533
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention resides in a method for in situ cleanup of soil contaminated by pollutants wherein the pollutants are extracted from the soil by a micro-emulsion containing oil compounds and further in a micro-emulsion containing oil compounds that are suitable for the method.
Micro-emulsions are thermodynamically stable, optically isotropic dispersions of two or more immiscible liquids, liquid mixtures or solutions which are stabilized by adding at least a third amphiphilic component.
Most natural and technical micro-emulsions are comprised of water and oil or fat as immiscible phases. Such micro-emulsions can be stabilized by molecules having hydrophilic as well as lipophilic properties, for example, by surfactants. Depending on the composition and ratio of the phases there are three possibilities of distribution. If water is the outer and oil is the inner phase, an O/W micro-emulsion is present whose basic character is determined by the water. If oil is the outer and water the inner phase, a W/O micro-emulsion is present whose basic character is determined by the oil. In bi-continuous micro-emulsions the two immiscible liquids are not present as discrete droplets but are continuously distributed.
A wide range of technical applications is known for micro-emulsions, including their use as solvents for chemical reactions, as formulations in the medical, pharmaceutical, and cosmetics fields, and as extraction agents, for example, for removing pollutants from soils.
For the in situ cleanup of contaminated soils according to known methods, solutions containing surfactants are used (see, for example, Visser, J. et al.: Surfactants in the Mobilization of Pollutants, in: Contaminated Soil >95, Vol. II, eds.: van den Brink, W. J. et al., Kluwer Academic Publishers, Dordrecht, 1995, 1373-1374; Rosenstock, F. et al.: Process of Treating Contaminated Soils, U.S. Pat. No. 5,223,147; Schäfer, G. et al.: Reinigung eines mit Dieselöl kontaminierten künstlichen Aquifers unter Einsatz von Tensiden, in: In-situ Technologie zur Grundwasser- und Altlasternsanierung, Kurzfassung zum VEGAS Workshop & BMBF/PWAB-Seminar, eds.: Institut für Wasserbau der Universität Stuttgart, Stuttgart, 1996, 19-20). For the elimination of pollutants that are nearly insoluble in water, such as polycyclic aromatic hydrocarbons, the use of oil-in-water micro-emulsions with very low oil contents (<1%) has been suggested (see, for example, Bonkhoff, K et al.: Extraktion von polyzyklischen aromatischen Kohlenwasserstoffen aus belasteten Böden, in: Fremdstoffe in Böden Akkumulation, Bioverfügbarkeit, Bewertungsansätze, eds.: Arbeitsgemeinschaft der Gro&bgr;forschungseinrichtungen AGF, Bonn 1994, 34-36; Bonkhoff K. et al.: Extraktion von PAK aus belasteten Böden, in: Erdöl & Kohle Erdgas Petrochemie 1995, 48 (2) 63-64; Bonkhoff et al.: Basic investigations for an in situ-soil remediation with O/W micro-emulsion, in: Contaminated Soil >95, Vol. II, eds.: van den Brink, W. J. et al., Kluwer Academic Publishers, Dcrdrecht 1995, 957-967; Bonkhoff, K. et al. Bodensanierung mit Mikroemulsion —von der Extraktion bis zu mikrobiellen Nachsorge, in: Schriftenreihe Biologische Abwasserreinigung, eds.: SFB 193; Biologische Behandlung industrieller und gewerblicher Abwässer, Technische Universität Berlin, Berlin 1996). Furthermore, a cleanup method is known from published international patent application WO 94/04289 and also from U.S. Pat. No. 5,833,756 according to which the organic pollutants are extracted from the fine grains of solids by means of a micro-emulsion.
The use of micro-emulsions for all of the aforementioned applications has the disadvantage that, at low temperatures, the stability of the micro-emulsion is often impaired. At temperatures of □20□ C. a micro-emulsion forms liquid crystals and is then no longer suitable for the aforementioned applications.
It is therefore an object of the present invention to provide a method for in situ cleanup of soils in which the pollutants are extracted from the soil by a micro-emulsion without the micro-emulsion forming liquid crystals so that the micro-emulsion can be used at temperatures of 0° C. to 20□° C. It is further an object of the present invention to provide suitable micro-emulsions for the method.
SUMMARY OF THE INVENTION
In the method of the invention for in situ cleanup of soil contaminated with a pollutant, a micro-emulsion is prepared having an oil component and a surfactant component, wherein the oil component comprises one or more compounds from the group of triglycerides, essential oils and fatty acid esters, and wherein the sufactant component comprises one or more surfactants selected from the group consisting of branched anionic surfaciants, multi-chain anionic surfactants, and branched multi-chain anionic surfactants. The pollutant is extracted with the micro-emulsion from the contaminated soil at a temperature range of 0° C. to 20° C.
The micro-emulsion of the invention for in situ cleanup of soil contaminated with a pollutant has an oil component comprising one or more triglycerides or fatty acid esters in amounts ≧5% by weight and <50% by weight, one or more dialkyl sulfosuccinic acid compounds as an anionic surfactant, and one or more non-ionic surfactants selected from the group consisting of a branched non-ionic surfactant, a multi-chain non-ionic surfactant, and a branched multi-chain non-ionic surfactant. The anionic and non-ionic surfactants are present in the micro-emulsion in an amount (total surfactant contents) of ≦30% by weight.
DETAILED DESCRIPTION OF THE INVENTION
The method according to the invention for in situ cleanup of soils contaminated with pollutants is performed at temperatures of 0° C. to 20° C., preferably above approximately 10° C., wherein the pollutants are extracted from the soil by a micro-emulsion which contains as an oil component one or more triglycerides, essential oil, and/or fatty acid esters and one or more branched and/or multi-chain anionic surfactants. It was surprisingly found that such micro-emulsions are suitable for soil cleanup at the aforementioned low temperatures because no liquid crystal form. Furthermore, it was found that when using the aforementioned micro-emulsion for the in situ soil cleanup, the extraction efficiency that is the pollutant removal is considerably improved in comparison to conventional oil-in-water-micro-emulsions, especially when the micro-emulsion has a high oil contents (≧5% (. by weight), preferably in the form of rape seed oil methyl ester (RME).
Preferably, an anionic surfactant with multiple and/or branched alkyl chains is used, especially sulfosuccinic acid-bis-2-ethylhexylester (Aerosol OT, AOT) or the corresponding sodium salt (see
FIG. 5
, top formula). Other anionic surfactants which, in principle, are also suitable are alkylbenzenesulfonate or dialkyl phosphate.
For performing the inventive method, the micro-emulsion contains furthermore especially one or more branched and/or multi-chain surface active components, preferably a surfactant and especially a non-ionic surfactant. The addition of a non-ionic surfactant has primarily the advantage that the insoluble calcium and/or magnesium salts of the anionic surfactants are kept in solution. Especially surfactants with branched chains, as, for example, trimethylnonyl hexaethoxylate ether (Tergitol TMN6, see
FIG. 5
, center formula), can be used as non-ionic surfactants because these components further reduce the liquid crystal formation. When adding a non-ionic surfactant, the ratio of anionic to non-ionic surfactant should be selected such that the phase behavior corresponds to that of an anionic surfactant. Ternary mixtures of water, oil, and nonionic surfactants which are able to form micro-emulsions exhibit at high temperatures always a two-phase region (2&PHgr;) in which the surfactant is preferably dissolved within the oil, while at low temperatures a two-phase region (2&PHgr;) is formed in which the surfactant is substantially enriched within the lower aq
Dierkes Frank
Haegel Franz-Hubert
Hoppe Karin
Mönig Kirsten
Subklew Gunter
Bach Klaus J.
Dr. Fauz-Hubert Haegel
Einsmann Margaret
Webb Gregory E.
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