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Article
A Novel Solution to Oil Spill Recovery; Using Thermo-degradable Polyolefin Oil Super-absorbent (oil-SAP)"
Xuepei Yuan, and T. C. Mike ChungEnergy Fuels, Just Accepted Manuscript • DOI: 10.1021/ef300388h • Publication Date (Web): 09 Jul 2012
Downloaded from http://pubs.acs.org on July 9, 2012
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Energy & Fuels
A Novel Solution to Oil Spill Recovery; Using Thermo-degradable
Polyolefin Oil Super-absorbent (oil-SAP)
Xuepei Yuan and T. C. Mike Chung*
Department of Materials Science and Engineering,
The Pennsylvania State University
University Park, Pennsylvania 16802
* Author to whom all correspondences should be addressed (chung@ems.psu.edu)
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Abstract
This paper discusses a novel approach that may provide a complete solution to combating
oil spills. The technology is centered on a cross-linked polyolefin terpolymer (x-OS-DVB),
containing 1-octene, styrene, and divinylbenzene units, which is an oil super-absorbent (oil-SAP)
with aliphatic and aromatic side chains that have similar solubility parameters (oleophilic and
hydrophobic properties) with the hydrocarbons in crude oil. Some x-OS-DVB terpolymers, with
desirable morphology (amorphous, low Tg, and high free volume) and lightly cross-linked
(complete network) structure, show rapid oil absorption and swelling to reach a capacity 45
times of their weight. The capacity of oil uptake (swelling) is inversely proportional to the cross-
linking density. The combination of selective oil absorption (without water) and tough
mechanical strength offers buoyancy, stability, and easy recovery on water surfaces. The
recovered oil-swelled gel, containing more than 98% oil and 2% of x-OS-DVB, is suitable for
regular oil refining processes (an economic, no waste, and no pollutant approach). The bulk side
chains in x-OS-DVB result in relatively low ceiling temperature for depolymerization and zero
heating residue at 450o C, well below the first distillation step (>600o C) in oil refining.
Furthermore, polyolefins are the most inexpensive polymeric material, with a large production
capability around the world. Overall, this cost-effective new polyolefin oil-SAP technology shall
dramatically reduce the environmental impacts from oil spills and help recover one of our most
precious natural resources.
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Introduction
In light of the 2010 BP oil spill in the Gulf of Mexico—more than 20 years after the
Exxon Valdez disaster in Alaska—we still have no effective technology for removing,
recovering, and cleaning up oil spills or oil slicks from the surfaces of water bodies and
shorelines. Despite the government’s "all hands on deck" approach to combating the oil spill,
currently-used methods (booms and skimmers, dispersants, and in situ burning) are decades-old,
low-tech, and manpower-intensive, some with unknown environmental consequences. Based on
these current methods, most spilled oil is wasted and becomes pollutants in our air and waters.
Furthermore, any small fraction that is actually recovered generates a large quantity of solid and
liquid waste itself, from tons of soiled boom and other oily waste. It is treated as industrial waste
and buried at specially-designated dumps, some near residential neighborhoods. In fact, oil spill
accidents around the world are actually more frequent than the few highly-publicized cases in
United States. As shown in Figure S1, every few years there has been a major oil spill, due to
storage tanks and cracked pipes, oil tanker collisions or wrecks, even from war with delivery
destroying oil facilities. The Exxon Valdez spilled 11 million gallons oil into the Prince William
Sound, but even that case did not make the top ten list of the largest oil spills (the smallest spill
on the list was four times larger than that of Exxon Valdez). Indeed, more than 30 oil spills were
measured as larger and more devastating in the past 40 years.
There have been some reports discussing the sorption of crude oils, which is an attractive
approach to the actual removal of spilled oil. Two general sorption mechanisms include
adsorption (surface sorption) mechanism by employing porous or fibrous (high surface area)
materials and absorption (matrix sorption/swelling) mechanism by using cross-linked oleophilic
and hydrophobic materials [1]. The economic and environmental concerns surrounding oil spills
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encouraged many researchers to investigate natural sorption materials, such as multifarious
inorganic porous products (i.e. clay, talc, zeolites, silica aerogel, calcium fly ash, etc.) [2,3], and
organic biodegradable products (straw, hull, corncob, peat moss, sugarcane bagasse, wood/cotton
fibers, wool-based materials, silkworm cocoon waste, etc.) [4-10]. However, most of them show
limited oil sorption capacity and also absorb water, thus making the recovered solids unsuitable
for calcinations; most of them end up in the landfills. Meltblown PP pads and booms [11,12] are
the most commonly used oil sorbent materials, adsorbing oil in their interstices via capillary
action. Due to the weak oil-substrate interaction (adsorption mechanism), the fiber-based
adsorbers exhibit many disadvantages, including failure to maintain oil of low viscosity and easy
re-bleeding of adsorbed oil under a slight external force. There are also some reports disclosing
the usage of hydrophobic alkyl acrylate oil absorbents [13-16], such as cross-linked
styrene/acrylate, 1-octene/acylate, and octadecene/maleic anhydride copolymers. However, these
resins contain some hydrophilic polar groups and require an additional procedure for cross-
linking reaction after copolymerization. In addition, this method has the drawback of a long
absorbing time, especially for aliphatic hydrocarbon components. Some synthesized rubbers [17-
22], such as polybutadiene, butyl rubber, SBR, and EPDM, were also modified (grafting and
cross-linking) to achieve the network structure for oil absorption. However, the solution cross-
linking is hardly controlled; they usually require extensive solvent extraction to remove soluble
fraction. The resulting sol-free materials possess various degrees of cross-linking density,
reducing the overall oil swelling capability. Some methods, i.e. milling, electric-spinning, and
foaming of the oil absorbents to increase surface area, have also been applied to improve oil
absorbing speed. However, many materials [23-25], similar to that of meltblown PP, only
physically adsorb oil at the surface by capillary action. Recently, several papers applied the high
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surface area materials, including nanowire membranes [26], nanocellulose aerogels [27], carbon
nanotube aerogels [28], to increase oil adsorption capacity. The treatment of the recovered solid
materials is always a major concern, including waste disposal, recyclability, and biodegradability.
Overall, it is still a major scientific challenge to identify a suitable oil-SAP material that can
offer a comprehensive solution for combating future oil spills.
Experimental Section
Materials and Instrumentation
All O2 and moisture sensitive manipulations were carried out inside an argon filled Vacuum
Atmosphere dry box. 1-Octene, styrene, p-divinylbenzene (Sigma-Aldrich) were distilled over CaH2
under argon. Toluene (Wiley Organics) was dried via refluxing over sodium metal for 48 hours
under argon. TiCl3.AA (AA: activated by aluminum metal), AlEt2Cl (25 wt% in toluene) (Sigma-
Aldrich), and hexane, benzene, cyclohexane, petroleum (VWR) were used as received. Gasoline
(octane# 98) and diesel were purchased from a service station of Shell Oil Company. Meltblown PP
pads were kindly provided by Newpig Corporation in Pennsylvania.
All 1H spectra were recorded on a Bruker AM-300 instrument in chloroform-d at room
temperature. The thermal properties of the polymers were measured by differential scanning
calorimetry (DSC) using a Perkin-Elmer DSC-7 instrument controller with a heating and cooling
rate of 20o C/min under nitrogen. The molecular weight of the polymer was determined using a
Waters GPC. The columns used were Phenomenex Phenogel of 105, 104, 103, and 500 Å. A flow
rate of 0.7 ml/min was used, and the mobile phase was THF. Narrow molecular weight
polystyrene standards were used to estimate the molecular weight.
Synthesis of 1-octene/styrene/divinylbenzene Terpolymers
In a typical 1-octene/styrene/divinylbenzene terpolymerization reaction, 50 ml of toluene,
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5 ml of 1-octene, 5 ml of styrene and 0.2 ml of DVB were charged into a Parr 450 ml stainless
autoclave equipped with a mechanical stirrer in an argon-filled dry-box. The reactor was sealed
and moved out of the dry box, then purged with nitrogen gas at 25o C. About 0.101g of
TiCl3(AA) and 4ml of AlCl2Et (25 wt% in toluene) were added under nitrogen pressure to
initiate the polymerization. After agitation for 3 hours at elevated temperature (~45o C), the
reaction was terminated by adding 100 ml of dilute HCl solution in methanol. The polymer was
isolated by filtration and washed completely with methanol, then dried under vacuum for 8 hours.
About 4 g of OS-DVB terpolymer was obtained. The terpolymers were completely soluble in
common organic solvents, including toluene, THF, and decalin. They were analyzed by 1H NMR
and GPC to determine their molecular structures.
Oil Absorption Evaluation
Oil absorption tests were conducted following the standard method (ASTM F726-06)
using various oils. Typically, a piece of polymers around 0.2 g was put into gasoline. After
certain time, the sample was picked up with a tweezer and laid on a filter paper to remove the
excess gasoline before weighing it on a balance. Oil absorbency (g/g) was calculated by the
weight ratio between the absorbed oil to the origin dried materials. In order to study swelling
kinetics, the above measurements were carried out from time to time. In addition, the absorption
study was also extended to the individual crude oil components, including alkanes (such as
heptane), cycloalkanes (such as cyclohexane), and aromatic hydrocarbons (toluene and xylene),
respectively. Evidently, these amorphous x-OS-DVB based oil-SAP samples are very effective
absorbing both aliphatic (linear and cyclic) and aromatic hydrocarbon molecules, and their
capacities are basically controlled by cross-linking density (swelling ability), lower cross-linking
density higher swelling and absorption capacity.
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Results and Discussion
Our research approach has been focused around the design of a new oil super-absorbent
polymer (oil-SAP) that can simultaneously exhibit a combination of several essential properties,
including (a) high oil absorption capacity, (b) fast kinetics, (c) no water absorption, (d) buoyancy
and good mechanical strength for easy recovery from water surface, (e) the recovered oil/oil-
SAP mixture suitable in regular oil refining process, and (f) cost-effectiveness. The study has
been centered on new polyolefin-based oil-SAP polymers that are petroleum downstream
products, having similar solubility parameters (oleophilic and hydrophobic properties) with the
hydrocarbon components in crude oil, and low production cost. With a suitable polyolefin
structure and morphology, the polymer shall rapidly absorb oil (without water) and swell its
volume to accommodate a large quantity of absorbed oil. The resulting oil/oil-SAP mixture (pure
hydrocarbons) shall float on the water surface with good stability for easy recovery. In addition,
it is highly desirable that the oil-SAP polymer can be thermally decomposed back to low
molecular weight hydrocarbons (monomers) at <600o C during the first refining (distillation) step.
Therefore, the recovered oil/oil-SAP mixtures shall be suitable for regular oil refining processes
and resolving concerns regarding disposal, recyclability, biodegradability, and environmental
issues caused by the initial oil spill.
As illustrated in Scheme 1, a series of amorphous 1-octene/styrene/divinylbenzene (OS-
DVB) terpolymers (I) were systematically synthesized using a common heterogeneous Ziegler-
Natta catalyst that shows to be suitable for preparing high molecular weight OS-DVB
terpolymers with good control of composition and random structure, and only engaging mono-
enchainment for divinylbenzene (DVB). As will be discussed, a lightly cross-linked oil-SAP
material (an oil-swellable network) is crucial for achieving a high oil absorption capability,
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which requires a high molecular weight OS-DVB terpolymer (I) with few DVB cross-linker
units in every polymer chain. The resulting OS-DVB terpolymer (I), containing some pendent
styrene moieties (thermal cross-linkers), is completely processible (soluble) in forming various
product sizes and shapes (II). However, upon thermal heating (>220o C) it becomes a completely
insoluble network structure (III) by engaging in a Diels-Alder [2+4] inter-chain cycloaddition
reaction between two pendent styrene units in the adjacent polymer chains [28-30]. This solid-
state cross-linking reaction (effective and without any by-product) eliminates the requirement of
an expensive solution-removal of hydrocarbon-soluble fractions shown in many papers, in which
the cross-linking reactions were usually carried out in dilute solutions with a considerable
amount of intra-chain coupling activities.
CH3
+
(I)
(II)(III)
(CH2-CH)x (CH2-CH)y
OS
OS
CH2=CH
(CH2)5
CH=CH2
CH2=CHCH2=CH + (CH2-CH)z
CH3
(CH2)5
CH=CH2
Ziegler-Natta
catalyst
Processing
OS-DVB
productthermal cross-linking
oil-SAP
Scheme 1. Synthesis of cross-linked x-OS-DVB terpolymer material for oil absorption.
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Table 1. Synthesis and oil absorption evaluation of cross-linked 1-octene/styrene/divinylbenzene terpolymersa.
Run no.
Polymerization condition Absorption capacity (weight times)f
Monomer A/B/Cb
(ml)
Terpolymerc [A]/[B]/[C] (mole ratio)
Yield (g)
Mwd
(Kg/mol) Gele (%)
Gasoline Petroleum Diesel Toluene Hexane Benzene Cyclo- hexane
A-1 5/5/0.2 82.3/17.4/0.3 3.07 330 100 41.3 40.3 41.1 47.1 42.8 40.7 43.5 A-2 5/5/0.5 79.3/20.2/0.5 3.76 410 100 21.1 19.6 20.0 22.7 20.4 19.8 22.0 A-3 5/5/1 78.4/20.7/0.9 3.94 420 100 13.7 11.6 11.9 11.6 11.9 14.1 14.1 A-4 5/5/2.5 76.3/22.3/1.4 4.02 460 100 6.41 6.28 6.39 6.24 5.62 5.59 7.02 A-5 5/5/5 74.1/24.0/1.9 4.56 520 100 5.45 5.34 5.40 4.75 5.10 5.21 5.80 PPg - - - - - 9.21 9.71 9.09 10.0 8.10 10.4 11.3 a. Polymerization condition: TiCl3(AA)/AlCl2Et= 0.101g/4ml (25 wt% in toluene), 50 ml of toluene, 45o C for 3 h; Cross-linking condition: 240o C
for 2 h. b. A: 1-octene, B: styrene, and C: divinylbenzene. c. Determined by 1H NMR spectra. d. Measured by GPC with a standard polystyrene calibration curve. e. After thermal cross-linking reaction, the gel content was determined from the toluene-insoluble part after Soxhlet extraction. f. Absorption time: 24 hours g. Commercial meltblown PP pad (adsorption mechanism).
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Table 1 summarizes the experimental results of the terpolymerization reaction with 1-
octene, styrene, and divinylbenzene (DVB) using a heterogeneous Ziegler-Natta catalyst (i.e.
TiCl3(AA)/AlCl2Et; AA: activated by aluminum metal). This traditional Ziegler-Natta catalyst
shows an effective incorporation of both 1-octene and styrene co-monomers and mono-
enchainment of DVB to form the homogeneous OS-DVB terpolymer (I) solution with a rather
narrow molecular weight and composition distribution. In general, the terpolymerization results
are quite consistent with the previous observation in the copolymerization reactions between 1-
octene and styrene [31] and 1-octene and p-methylstyrene [32]. Although 1-octene exhibits
higher reactivity than styrenic monomers (styrene and p-methylstyrene), the styrenic
comonomers can be homogeneously incorporated in the copolymer with high molecular weight
and a broad range of copolymer compositions using heterogeneous Ziegler-Natta catalysts.
Figure S2 in the Supplemental Information shows a typical GPC curve of the terpolymer (run A-
1) with high molecular weight (Mw~330,000 g/mol) and relatively narrow molecular weight
distribution (Mw/Mn~2.1). As will be discussed, the DSC curves also show a sharp Tg that is
proportional to the styrene content, and the styrene and DVB contents are directly proportional to
the monomer feed ratios. The high OS-DVB terpolymers, containing more than 20 mol%
aromatic units (styrene and DVB), have been prepared without any detectable cross-linking
reaction. All resulting OS-DVB terpolymers were completely soluble in common hydrocarbon
solvents, such as hexane and toluene, at ambient temperature.
Figure 1 shows a typical 1H NMR spectrum of OS-DVB terpolymer (run A-5). There are
several aliphatic proton chemical shifts at 0.8 ppm, corresponding to CH3 in the 1-octene units,
and a band between 0.9 and 1.7 ppm, corresponding to CH2 and CH in the polymer backbone and
1-octene side chains. In the expanded region, there are three minor bands around 5.2 and 5.7 ppm
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(CH=CH2) and 6.7 ppm (CH=CH2), corresponding to the vinyl groups in the pendent styrene
groups (after mono-enchainment of DVB units). There is also a broad aromatic proton band
between 6.9 and 7.4 ppm (C6H4) from both styrene and DVB units. The integrated intensity ratio
between all three vinyl protons from the DVB units and the phenyl protons from both styrene and
DVB units determines the styrene and divinylbenzene mole ratio. The mole ratio of 1-octene was
determined by the CH3 chemical shift intensity at 0.8 ppm.
Figure 1. 1H NMR spectrum of an OS-DVB terpolymer (run A-5).
Figure 2 shows thermal properties of the OS-DVB terpolymers in Table 1, including
differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements.
In Figure 2 (left), all DSC curves exhibit only one sharp Tg transition in the flat baselines. There
was no any detectable melting point up to 200o C. The Tg (-80o C) of poly(1-octene) linearly
increases with its aromatic comonomer content. All OS-DVB terpolymers (Table 1) exhibit low
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Tg’s (< -50 oC), even with 25 mol% of aromatic (styrene and DVB) content. The combination
implies a homogeneous terpolymer microstructure with a completely amorphous morphology
and high free volume. Figure 2 (right) shows TGA curve of an OS-DVB sample (run A-1).
Under an inert atmosphere, the OS-DVB terpolymer starts its thermal decomposition at 300o C
and rapidly decreases its weight around 400o C. At 450o C, the OS-DVB terpolymer was
completely decomposed without any residue, indicating the formation of volatile small
hydrocarbon molecules. Based on the mass spectrum, the main volatile components are the 1-
octene and styrene monomers, with their derivatives having the molecular size below C20.
Overall, the thermal decomposition profile resembles those of poly(1-octene) and polystyrene
hompolymers. The bulky side chains in 1-octene and styrenic monomer units weaken the C-C
bonds along the backbone, which may result in chain scission and the subsequent free radical
mediated depolymerization [33, 34] at a relatively low pyrolysis temperature. It is interesting to
note that the OS-DVB terpolymer (I) shall engage in rapid cross-linking activities during the
thermal process (>200o C). However, the resulting cross-linking structure appears to have little
effect to the overall thermal degradation.
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Figure 2. (left) DSC curves of four OS-DVB terpolymers (runs A-1, A-2, A-3, and A-4), (right)
TGA thermographs of an OS-DVB terpolymer (run A-1) under nitrogen atmosphere.
Before oil absorption evaluation, the OS-DVB terpolymer (I) solids were divided into
1/4" sized particles and then heated at 240o C under N2 for 2 hours to complete the cross-linking
reaction. The resulting x-OS-DVB samples (III) were subjected to a vigorous solvent extraction
by refluxing toluene for 36 hours to examine any soluble fraction that was not fully cross-linked
into the network structure. Evidently, all x-OS-DVB samples in Table 1 show no detectable
soluble fraction, even in the terpolymer (run A-1) with only 0.3 mol% DVB units (about 5 DVB
units per polymer chain), indicating a very efficient thermal cross-linking reaction under a
polymer melt state condition. The extensive chain entanglement among many polymer chains
significantly enhances the inter-chain Diels-Alder [2+4] cycloaddition reaction between two
pendent styrene units from adjacent polymer chains. The high molecular weight terpolymer with
narrow molecular weight and composition distributions certainly also helps in achieving the
complete network structure.
The resulting x-OS-DVB terpolymers (runs A-1 to A-5) were subjected to contact with
various oils and pure hydrocarbons in order to understand their oil absorption capability and
kinetics. Since crude oil is predominantly a mixture of aliphatic and aromatic hydrocarbons with
various molecular weights, and the exact molecular composition varies widely from formation to
formation. Thus, we decided to examine a broad range of petroleum products, including some
representative of pure aliphatic and aromatic compounds. Table 1 summarizes the experimental
results with several individual aliphatic and aromatic hydrocarbons (i.e. hexane, cyclohexane,
benzene, and toluene) and some common petroleum products (i.e. gasoline, petroleum, and
diesel). Figure 3 compares the oil uptake vs. time for five x-OS-DVB samples (runs A-1 to A-5)
with a crude containing approximately 70% volatile light oils and 30% non-volatile heavy oils.
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Figure 3. Oil uptake vs. time for a comparative set of x-OS-DVB samples (runs A-1 to A-5) with
a crude containing approximately 70% volatile light oils and 30% non-volatile heavy oils.
Seemingly, the oil absorbency and swelling capacity in x-OS-DVB is largely controlled
by cross-linking density, reversely proportional to the cross-linking density. There is a very
minor dependence on the absorbates—either the aliphatic or aromatic hydrocarbons, or even the
mixed oil products. All of the x-OS-DVB samples contain both aliphatic and aromatic side
chains with similar mole ratios, but with different cross-linking densities. The lowest cross-
linking density of x-OS-DVB (run A-1), with 82.3/17.4/0.3 1-octene/styrene/DVB mol%,
exhibits a high absorbent capacity and the largest degree of swelling, forming a softer and more
cohesive gel formation. Conversely, the x-OS-DVB sample with high cross-link density (run A-
5) shows lower absorbent capacity and swell. The gel strength is firmer and can maintain particle
shape, even under modest pressure.
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Figure 4. Oil up-take for (a) x-OS-DVB (run A-1) and (b) commercial meltblown PP pad.
Figure 4 compares the oil absorption performance of the x-OS-DVB sample (run A-1)
with a state-of-the-art meltblown PP pad that is fabricated from a nonwoven fibrous PP textile
with a highly crystalline polymer structure and porous morphology (high surface area). They
were examined side-by-side for comparison. The meltblown PP pads (adsorption mechanism)
show rapid oil adsorption in their interstices by capillary action, saturating at 10 times the weight
of uptake without any visible volume enlargement. The adsorption mechanism happens only on
the PP fiber surfaces (not inside the crystalline matrix), which is advantageous with fast kinetics
but with limited capacity, and the weak oil-PP interaction results in some adsorbed oil re-
bleeding under a slight external force. On the other hand, the lightly cross-linked oil-SAP sample
(run A-1), with amorphous morphology, gradually absorbs oil in its matrix, increasing its weight
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by more than 10 times within 10 minutes, and reaching 40 times its weight after 12 hours. Its oil
sorption capacity is superior (>4 times) to that of the state-of-the-art meltblown PP pad.
Figure 5. (a) The starting x-OS-DVB oil-SAP sample (run A-1), (b) after soaking with crude oil,
this swelled oil-SAP is floating on the surface of water, and (c) is picked up by a tweezer. The
background grid is used for the scale reference.
Figure 5 shows the action of this x-OS-DVB sample (run A-1) during the oil absorption.
The starting 1/4" sized oil-SAP sample (Figure 5 (a)) can effectively absorb crude oil from the
water surface with a large expansion of its volume (>40 times). Subsequently, the resulting
oil/oil-SAP mixture floating on water surface (Figure 5 (b)) is ready for collection and can be
picked up with a tweezer without leaking oil (Figure 5(c)). The combination of good mechanical
strength (cross-linked elastic structure) and a strong affinity between the oil and polymer matrix
assure its structure integrity and oil absorption stability. In a real-world context, it shall also be
stable under ocean environments (waves, wind, sunlight, etc.) and be easily removed from the
water surface. Had this material been applied to the top of the leaking well head in the Gulf of
Mexico during the 2010 spill, this oil-SAP could have effectively transformed the gushing brown
oil into a floating gel for easy collection, and minimized the pollution consequences to our air
and water.
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In addition to effective oil recovery, the resulting oil-swelled gel mixture can be treated
as crude oil, suitable for regular refining processes (distillation and cracking). The mixtures
contain no water and have nearly the same composition as original crude oil. During refinery, the
minor component (2-3%) of x-OS-DVB polymer will be thermally decomposed back to <C20
hydrocarbon molecules (typically existing in crude oil) without residue (Figure 2), well below
the typical crude oil refining temperature (>600o C). This process has multifarious benefits: it
eliminates the concern surrounding solid waste disposal, recyclability, and biodegradability, and
maintains our reservations of natural resources. Furthermore, polyolefin products are the most
inexpensive of polymeric materials, and are capable of large-scale production around the globe.
With conservative estimates, the production cost of new oil-SAP material comes below $2 per
pound in large-scale industrial production. One pound of oil-SAP, with a 40 times absorption
capacity, can recover more than five gallons of spilled oil (currently treated as a pollutant instead
of a useable resource) to regular crude oil that is worth more than $12 (based on $80/barrel).
In this study, we have developed a new oil-SAP technology based on polyolefin based x-
OS-DVB terpolymers that can be effectively prepared by a conventional Ziegler-Natta catalyst
and then thermally cross-linked into the oil-SAP materials. The combination of oleophilic and
hydrophobic properties with amorphous morphology, high free volume, and a cross-linked
network offers a desirable matrix for oil absorption and swelling. The oil uptake is inversely
proportional to the cross-linking density. Oil uptake with up to 45 times that of the polymer
weight and fast kinetics has been observed in a lightly cross-linked x-OS-DVB terpolymer.
Overall, this new oil-SAP technology exhibits a combination of benefits in oil recovery and
cleanup, including (i) high oil absorption capability, (ii) fast kinetics, (iii) easy recovery from the
water surface, (iv) no water absorption, (v) no waste in natural resources, and (vi) is cost-
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effective and economically feasible. This new oil-SAP technology shall fundamentally address
the multiple issues created by mega oil spills, whether seen from an environmental or economic
standpoint.
Acknowledgement
The authors gratefully acknowledge the financial support of this work by an NSF
Research Grant (CBET-1067554) and commercial feasibility study by Ben Franklin Foundation
under its Translational Research in Energy Support Program.
Supporting Information Available: Major oil spills and polymer structure characterization
(GPC and TGA curves) of OS-DVB terpolymers. This material is available free of charge via the
Internet at http://pubs.acs.org.
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Reference:
1. Karan, C. P.; Rengasamy, R. S.; Das, D. Indian J. Fibre & Textile Res. 2011, 36, 190-200.
2. Arbatan, T.; Fang, X.; Shen, W. Chem. Eng. J. 2011, 166, 787-791.
3. Karakasi, O. K.; Moutsatsou, A. Fuel 2010, 89, 3963-3970.
4. Chol. H. M.; Cloud, R. M. Environ Sci. Technol. 1992, 26, 772-776.
5. Teas, C.; Kalligeros, S.; Zanikos, F.; Stournas, S.; Lois, E.; Anastopoulos, G. Desalination
2001, 140, 259-264.
6. Inagaki, M.; Kawahara, A.; Konno, H. Carbon 2002, 40, 105-111.
7. Adebajo, M. O.; Frost, R. L.; Kloprogge, J. T.; Carmody, O.; Kokot, S. J. Porous Materials
2003, 10, 159-170.
8. Deschamps, G.; Caruel, H.; Borredon, M. E.; Bonnin, C.; Vignoles, C. Environ Sci. Technol.
2003, 37, 1013-1015.
9. Suni, S.; Kosunen, A. L.; Hautala, M.; Pasila, A.; Romantschuk, M. Marine Pollution Bull.
2004, 49, 916-921.
10. Sun, X. F.; Sun R.C.; Sun J. X. J. Mater. Sci. 2003, 38, 3915-3923.
11. Bayat, A.; Aghamiri, S. F.; Moheb, A.; Vakili-Nezhaad, G. R. Chem. Eng. Technol. 2005, 28,
1525-1528.
12. Wei, Q. F.; Mather, R. R.; Fotheringham, A. F.; Yang, R. D. Marine Pollution Bull. 2003, 46,
780-783.
13. Jang, J.; Kim B. S. J. Appl. Polym. Sci. 2000, 77, 903-913.
14. Atta, A. M.; Arndt, K. F. J. Appl. Polym. Sci. 2005, 97, 80-91.
15. Atta, A. M.; El-Hamouly, S. H.; AlSabagh, A. M.; Gabr, M. M. J. Appl. Polym. Sci. 2007,
105, 2113-2120.
Page 19 of 21
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20
16. Farag, R .K.; EI-Saeed, S. M. J. Appl. Polym. Sci. 2008, 109, 3704-3713.
17. Shan, G. R.; Xu, P. X.; Weng, Z. X.; Huang, Z. M. J. Appl. Polym. Sci. 2003, 90, 3945-3950.
18. Ceylan, D.; Dogu, S.; Karacik, B.; Yakan, S.; Okay, O. S.; Okay, O. Environ Sci. Technol.
2009, 43, 3846-3852.
19. Essawy, H. A.; Essa, M. M.; Abdeen, Z. J. Appl. Polym. Sci. 2010, 115, 385-392.
20. Zhou, M. H.; Cho, W. J. J. Appl. Polym. Sci. 2002, 85, 2119-2129.
21. Zhou X. M.; Chuai, C. Z. J. Appl. Polym. Sci. 2010, 115, 3321-3325.
22. Fouchet, B. J. Appl. Polym. Sci. 2009, 111, 2886-2891.
23. Lin, C.; Huang, C. L.; Shern, C. C. Resource Conservation and Recycling 2008, 52, 1162-
1166.
24. Zhu, H.; Qiu, S.; Jiang, W.; Wu, D.; Zhang, C. Environ Sci. Technol. 2011, 45, 4527-4531.
25. Tanobe, V. O. A.; Sydenstricker, T. H. D.; Amico, S. C.; Vargas, J. V. C.; Zawadzki, S. F. J.
Appl. Polym. Sci. 2008, 111, 1842-1849.
26. Yuan, J. ; Liu, X. ; Akbulut, O. ; Hu, J. ; Suib, S. L. ; Kong, J. ; Stellacci, F. Nature Nanotech.
2008, 3, 332-336.
27. Korhonen, J. ; Kettunen, M. ; Ras, R. ; Ikkala, O. ACS Appl. Mater. Interfaces 2011, 3, 1813-
1816.
28. Gui, X. C.; Wei, J. Q.; Wang, K. L.; Cao, A. Y.; Zhu, H. W.; Jia, Y.; Shu, Q. K.; Wu, D. H.
Adv. Mater. 2010, 22, 617–621.
29. Chung, T. C. Functionalization of Polyolefins; Academic Press: London, 2002.
30. Lin, W. T. ; Shao, Z. ; Dong, J. Y. ; Chung, T. C. Macromolecules 2009, 42, 3750-3754.
31. Chung, T. C.; Lu, H. L.; Hong, S, Rubber Chem. and Technology 1999, 72. 283-298.
32. Fu, Z.; Zhu, L.; Deng, J.; Xu, J.; Wang, Q.; Fan, Z. J. Appl. Polym. Sci. 2011, 119, 677-684.
Page 20 of 21
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33. Faravelli, T. ; Pinciroli, M. ; Pisano, F. ; Bozzano, G. ; Dente, M. ; Ranzi, E. J. Anal. Appl.
Pyrol. 2001, 60, 103-121.
34. Guaita, M. British Polym. J. 2007, 18, 226-230.
35. Yuan, X. P. ; Chung, T. C. Appl. Phys. Lett. 2011, 98, 62901-62903.
Table of Contents Graphic
A Novel Solution to Oil Spill Recovery; Using Thermo-degradable Polyolefin Oil Super-
absorbent (oil-SAP)
Xuepei Yuan and T. C. Mike Chung*
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