A recent body of papers/patent applications describes the preparation, structure/properties and applications of aerogels produced from combinations of clays and polymers, using an environmentally-friendly freeze drying process. One material which resulted from this effort is a low density (<0.1 g/cm3) aerogel material which floats on, and rejects water, but has a high affinity for oil; the oil can be easily squeezed from the aerogels, which can then be placed back into service. Basic knowledge as to how polymer compositional changes in the aerogel composite materials determine the degree of oil absorption is lacking, as are details of the morphology of clay within the cellular structure and its impact upon the oil absorption process. A one year program at Case Western Reserve University (CWRU) is proposed during which the family of polymers which currently exhibit the greatest level of oil absorption when converted into aerogels, poly(amide-imides), would be compared with epoxy resins. The use of epoxy resins would represent a major cost reduction and would facilitate commercial adoption of this technology. Polymers (2-5 wt% solids in water) would be converted into aerogel structures, with the quantity and rate of oil uptake used to evaluate efficacy. The aerogel materials would be characterized by (i) density/BET surface area, (ii) compressive strength/modulus, and (iii) physical structure measured by SEM and XRD. The placement of clay particles within polymer/clay cell walls would be further investigated using high resolution SEM. Torlon® AI-30 and aliphatic/aromatic epoxies produced from combinations of 1,4-butanediol diglycidyl ether, bisphenol-A diglycidyl ether, and poly(ethylene glycol) diglycidyl ether, crosslinked by triethylene tetramine and/or 2,6-diamino pyridine would be evaluated; these are currently used in marine paint. Sodium montmorillonite and laponite would be used as the clay component (0-5 wt%) in the aerogel structures. An absorbance model would be a deliverable of this program.
NON-TECHNICAL SUMMARY:
At this moment, the Gulf of Mexico is awash with an oil spill of unprecedented size, representing one of the Nation's worst environmental disasters to date. Such oil spills, as well as more routine fugitive spills from refineries and marinas continue to impact and threaten marine life, the fisheries industry, and broadly the quality of life for a large number of Americans. Development of an effective material for efficiently removing oil from water is in the national interest. Research at Case Western Reserve University (Cleveland OH) has resulted in the development of polymer/clay "aerogel" materials which float on, and do not absorb water, but rapidly absorb 8 times their weight in oil; this oil can then be squeezed out of the aerogels, like with a sponge, and the aerogel can be returned to service in the water. A one year program is proposed which will identify the key factors necessary in optimizing this environmental protection product. The basic knowledge obtained in the proposed study will enable translation of the technology from the laboratory to manufacturing in the most effective and economical means possible. STEM workforce development will be impacted by this study as well. A high school student and an undergraduate researcher will combine with the funded Ph.D. student to form a work group; such teams have been demonstrated to work effectively together, and the PI and his institution have a significant track record of promoting young researchers into college and graduate institutions by using research as a means of making STEM fields attractive and relevant to students.
There exists a need for high-performance porous materials which can act as an oil absorbing media in the case of a water-borne spills. Polymer-clay aerogels show promise both in terms of performance as such absorbants, absorbing oil while rejecting water. This research first identified the material properties that need to be optimized for oil absorbance, then creating materials which fit those criteria. The materials created in this study are able to absorb up to fifteen times their weight in oil and in contrast to other oil spill remedies (dispersants) the use of aerogels allow for the recovery of spilled oil through simple mechanical extraction, through at least 10 cycles (each time the material is squeezed, over 90% of the absorbed oil is reclaimed). Three families of polymers were evaluated in conjunction with two added types of clays; these polymer/clay combinations were combined in water, then freeze dried to produce the low density, sponge-like absorbants using an environmentally friendly, commercially scalable process. The best of these products were found to float on, but not absorb water, and would absorb large amounts of oil. The aerogel materials are typically about 95% void fraction (i.e. 5% solids and 95% air); between 68-80% of that void space was found to fill with oil upon exposure to oil slicks. This research has shown that while clay is useful in forming strong aerogel structures, it does not help with absorbing oil, but does undesirably increases water absorption. Minimization of clay levels is therefore important in these products. Among the families evaluated, epoxy resins did not exhibit sufficient selectivity towards oil, and therefore are not candidates for commercialization, whereas poly(amide-imide) and olefinic polymers showed great promise. When commercial dispersions of polymers were used, it was advantageous to extract them with a cleaning solvent which removed surfactant processing aids - this extraction vastly reduced the amount of water that the systems could absorb. Chemical treatment with chemical agents further reduced water absorption while having no effect upon oil performance. A path forward which starts with inexpensive, commercial olefin dispersions and a minimal amount of clay, freeze dried into an aerogel, extracted once to remove processing aids, and treated with a common chemical treatment produced the highest levels of oil removal from spills, and the highest oil:water selectivities. When frozen at the optimum temperature, these materials appear to meet all known commercial requirements. The previous best candidate material was tested under real life conditions in a harbor by a third party company, removing oil such than can be found in any working port. The aerogel material out performed all other products, and now needs to be scaled up to commercial volumes.
