Liquid purification or separation – Processes – Ion exchange or selective sorption
Reexamination Certificate
2002-06-18
2004-11-02
Hopkins, Robert A. (Department: 1724)
Liquid purification or separation
Processes
Ion exchange or selective sorption
C210S690000, C525S480000
Reexamination Certificate
active
06811703
ABSTRACT:
1.0 FIELD OF THE INVENTION
The present invention relates generally to the removal of organic compounds and inorganic ions from soils, hazardous spills, and aqueous environments and to the use of this polymer as an adhesive to affix an ion exchanger to remove inorganic compounds. More particularly, this invention pertains to a technology for reducing runoff and/or leaching of organic compounds such as pesticides present in an agricultural, environmental or industrial setting.
In preferred embodiments, compositions and methods are disclosed for stabilized organic polymer formulations capable of binding organic compounds, such as insecticides, herbicides, fungicides and nematicides. Also provided are methods of using such compounds in the remediation of environmental contamination, in the reduction of pesticide leaching from soil, in the containment of such pollutants, as an amendment to soil and method of coating sand particles with other particles to impart ion exchange characteristics, water holding, and plant growth enhancement capacities without reduction of soil percolation rate.
2.0 BACKGROUND OF THE INVENTION
Water pollution remains a major concern although numerous substances and methods exist for its prevention or reduction. Contamination of the groundwater also can occur thus containment of the pollutants at their source is a goal. Conventional water treatment involves collection of wastewater in a central plant to be processed. This treatment mandates constant maintenance and monitoring by knowledgeable persons in the field. In U.S. Pat. No. 4,971,698 to Weber et al., biodegradable contaminants in wastewater are removed by a decentralized process dependent on microorganisms or products thereof. This method may be economically feasible for containing compounds at the source, but because of its dependence on the viability of the microorganisms it may require reapplication and its usefulness may be limited to specific biodegradable compounds.
A. Landfill Leachate Treatment
Microbes in landfills tend to produce a large amount of organic acids due in large part to anaerobic metabolism. Organic acids can complex with metal ions thereby mobilizing the metals and protecting them from oxidation which may result in precipitation from solution. This association of organic acids and inorganic materials is referred to as landfill leachate. Other pollutants that comprise landfill leachate include pathogenic organisms, solvents, pesticides, hazardous wastes, and industrial and wastewater.
Studies relating to the extent to which leachate leaves a landfill location by groundwater or surface water have shown that in arid and semiarid climate sites the water transport rates are slow, however, for sites in temperate climate the leaching happens fast, presenting a serious environmental concern. This landfill leachate contamination of aquifer and groundwater continues despite landfill construction and design criteria to minimize it.
Lining landfills with impermeable membranes has also been considered wherein leachate is collected and treated either on or off-site. Off-site treatment may involve piping the leachate to a nearby sewer system, and combining it with the municipal sanitary sewage. This off-site treatment methodology, not only requires a municipal treatment facility capable of processing the leachate loadings but also a small concentration of leachate to wastewater for effective processing. For large landfill operations, on-site treatment of leachate with package plants has been attempted; but with limited success.
In U.S. Pat. No. 4,995,969 to LaVigne describes an on-site leachate treatment method in which the leachate is forced to run through leachate-tolerant plants and microorganisms that are capable of metabolizing organic carbon compounds and adsorbing heavy metals within the leachate. Although economical and effective, it may require substantial time and experimentation to establish the ecosystem in any given landfill. As materials in the landfill change, time to adjust the ecosystem may be necessary and such time may allow an inordinate amount of leachate to escape into the environment. Also, some landfills may not be able to support the growth of the necessary organisms.
Oxidation ponds or lagoons for treating leachate tend to be unsightly, malodorous, relatively slow, require large land areas and are a breeding ground for mosquitoes.
B. Adsorbents
One method of removing organic compounds from the environment has been through adsorbents which are generally solid phase materials having very high surface area-to-weight ratios and which have the ability to concentrate adsorbates on their surfaces (U.S. Pat. No. 4,147,624). Inorganic adsorbents include activated carbon, silica, silicates, alumina natural, and synthetic zeolites and clays.
Solid phase extraction (SPE) has been used in analytical chemistry to extract, purify, and concentrate analytes such as pollutants from large volume samples such as environmental water. Also, SPE's are used as a chromatographic matrix for the separation of mixtures whose components have different polarities.
The most common SPE material is octadecyl silica (C18 silica) although, for some applications, C8, C6, C4, C2 silica are also available. C18 silica is composed of pure silicon dioxide grains with surface silanol groups that are reacted with trichlorosilyloctadecyl groups. The result is 18 carbon chains bound to the silica. The resultant material is known as reverse phase (i.e., non-polar) silica.
When water containing relatively non-polar contaminants are passed through this material, the hydrophobic components associate with the C18 surface and the bulk of the water passes through to waste. In analytical work the contaminants are then eluted from the SPE via a solvent less polar than water.
In reverse phase chromatography, a solvent gradient from more to less polar is often used to selectively elute the different components.
The efficiency of the removal of contaminants from water by C18 silica is a function of the relative affinity of the component for the C18 hydrocarbon versus water. Thus somewhat polar compounds are not very effectively removed by C18 silica.
Importantly, the system that maximizes retention on the C18 matrix would include an extremely hydrophobic analyte dispersed in an extremely polar solvent (e.g., pure water). Solutes of intermediate polarity will be sorbed to a lesser extent by C18 silica.
The adsorption of non-polar compounds within an aqueous matrix by the C18 coated surface of the silica is preceded by the wetting of the SPE by the aqueous sample. Due to the hydrophobic nature of the C18 coating the SPE surface is quite water repellent. This inherent hydrophobiciy must be overcome before the C18 surface can efficiently adsorb the compounds of interest.
Many methods have been developed to circumvent this problem of surface wetting. Among these are the prewetting of the C18 coated silica with a solvent, such as methanol, which is miscible in both the C18 surface and water. The aqueous sample is then applied to the prewetted SPE.
Older SPE's used minimal C18 loading on the silica surface. This allowed the residual (highly polar) silanol groups on the silica surface to Interact with the aqueous lad sample. Other examples include using a C3 spacer onto silica (via silanol) to which a proprietary polar group is attached, then a C8 chain is added; an unspecified reverse phase coating on silica; a C6 hexyvphenyl on silica, only reverse phase.
In an attempt to circumvent the inherent hydrophobicity associated with a highly non-polar stationary phase, the synthesis of mixed mode solid phase sorbents has become the current technology. Typically, the mixed mode SPE polymers contains both hydrophilic and hydrophobic moieties. In this mixed mode arrangement, the small hydrophilic moiety merely allows the polymer surface (i.e. divinylbenzene, styrene, etc.) to be water-wetted. The non-polar moiety is still the only component responsible for the actual adsorption of the pollutant. Thus the “hydrophobicity” of the
Hopkins Robert A.
Richards Joanne S.
Stoll Keenon & Park, LLP
LandOfFree
Methods for adsorption and retention of solvated compounds... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods for adsorption and retention of solvated compounds..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods for adsorption and retention of solvated compounds... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3324691