(139a) Ultralight, Reusable Cellulose Diacetate Aerogels for Selective Fluid Sorption

Uncontrolled
oil or chemical spillage into fresh water can trigger a cascade of events
including toxic loading and contamination of food resources, all of which are
heavily detrimental to the ecosystem^1,2. Widespread
technologies proposed to deal with oil spills include oil skimming, in-situ
burning, mechanical containment and utilization of dispersants, solidifiers and
degrading microorganisms^3–8. However, these
methods are either inefficient or environmentally unfriendly. The need for
efficient oil spill cleaning technologies was imminent in 2010 deep water
horizon spill, one of the largest man-made disasters in the recent history,
where oil gushed out in the Gulf of Mexico for straight 87 days, pouring out
over 200 million gallons of crude oil⁹. In this type of
scenario, the use of sorbents is attractive as they are easy to deploy and do
not generate byproducts. There are three categories of sorbent materials:
organic (milkweed, wood chips, rice straw, among others), inorganic
(organo-clay, perlite and sand, zeolites, etc.) and synthetic (non-woven
polypropylene mats, for example).^10–12 However, they (1)
suffer from low sorption capability (typically less than 10 g per gram of solid
support); (2) are difficult to recover (they are not buoyant), and (3) are not
biodegradable.

In recent years, aerogels
have gained attention as sorbent materials because of their light weight and
high pore volume. In this study, highly porous (99.7% air volume) and
ultra-light (4.3 mg/ml density) cellulose ester aerogels were synthesized for
unprecedented water uptake (45-90 g/g) while affording wet strength and
mechanical robustness (maximum compressive stress and strain of 350 kPa and
92%, respectively). The high compression strains are generally achieved with carbon
nanofiber aerogels but the 92% strain is higher than those of nanocellulose
aerogel reported in literature. The compressive stress of 350 kPa is 100 times
higher than the reported cellulosic aerogels (see Figure 1). The aerogels were
further adjusted towards hydrophobicity and oleophilicity via chemical vapor
deposition with an organo-silane species. The as-modified aerogel exhibited
high oil retention (20-30 g/g aerogel) while maintaining mechanical integrity
for fast oil cleanup from aqueous media under marine conditions.

Figure 1:
a) Image of a 2 w/v% aerogel (density 4.3 mg/ml) on a dandelion leaf; b)
Compressive stress-strain profile for 4 w/v% aerogels with the maximum
compressive stress of 350 kPa and maximum strain of 92%. Inset: SEM image
showing the radial cross-section of 4 w/v% CDA aerogel with a “honeycomb” like
structure.

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