potential ofcogon grassasanoilsorbent

ISSN 0853 - 2788Akreditasi No: 345/Akred-LIPIJP2MBII07l2011

POTENTIAL OF COGON GRASS ASAN OIL SORBENT

Edi Iswanto WHoso·,Vera Barlianti, Irni FitrlaAnggraini, and Hendris Hendarsyah

Research Center for Chemistry - Indonesian Institute of Sciences,Puspiptek; Cisauk, Tangerang 15314, Banten; IndonesiaTelp: + 6221 756-0929, E-mail:[email protected]

Diterima: 30 April 2012; Disetujui: 25 Mei 2012

ABSTRACT

Experiments on the potential of Cogon grass(lmperata cylindrica), a weed harmful to otherplants, for use as a low-cost and biodegradable oilsorbent were carried out under various spillconditions. Flowers of Cogon grass adsorbedmuch larger amount of high-viscosity lubricatingoil (57.9 g-oil/g-sorbent) than that adsorbed byPeat Sorb (7.7 g-oil/g-sorbent), a commercial oil-sorbent based on peat. However, the flowersadsorbed only 27.9 g of low-viscosity crude oillg-sorbent. In an oil-water system, the amount of oiladsorbed was influenced by the level with which thetwo were mixed: vigorous stirring reduced thesorption capacity by 36%. The high sorptivecapacity of the flowers can be attributed to theirhydrophobic nature and good oil-wettability. Theflowers showed good buoyancy even after 24 hoursof shaking under conditions that simulated waterripple (gentle wary motion) in sea, which suggeststheir potential in combating oil spills both on landand in water.Keywords: Sorbent; Oil spill,' Oil sorption; Cogon grass;

Imperata cylindrica

ABSTRAK

Telah dilakukan pengujian terhadap potensibunga rumput Alang-alang (Imperata cilindrica)sebagai sorben penyerap-minyak pada berbagaikondisi tumpahanminyak di lahankering dan di air.Padapermukaan yang kering, bungarumputAlang-alang dapat menyerap jauh lebih banyak minyakpelumas (57,9 g-minyaklg-sorben) dibanding PeatSorb (7,7 g-minyaklg-sorben), contoh sorben

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komersial berbasis gambut. Sedangkan terhadapminyak mentah dengan viskositas rendah, bungarumput hanya menyerap sebanyak 27,7 g-minyaklg-sorben. Pada penanganan tumpahanminyak di air, jumlah minyak yang dapat diserapdipengaruhi oleh tingkat pengadukan minyak danair. Pengadukan yang kuat dapat menurunkankapasitas penyerapan minyak hingga 36%dibanding tanpa pengadukan. Kapasitaspenyerapan bunga Alang-alang yang tinggi inidipengaruhi oleh sifat hidrofobisitasnya yang baik.Bunga Alang-alang juga menunjukkan sifatmengambang yang baik pada permukaan air yangdiguncang menyerupai riak air di laut. Hasil diatasmenunjukkan bahwa bunga alang-alangberpotensibaik sebagai bahan sorben penyerap-minyak untukpenanganan tumpahan minyak di lahan kering dandiair.KataKunci: Sorben, Tumpabanminyak, Penyerapanminyak,

RumputAlang-alang, Imperata cyltndrica.

INTRODUCTION

Oil spills are one of the major sources ofenvironmental pollution in land and marineenvironments. Improving the techniques forcontrolling and removing oil spills is an active areaof research. One of the approaches to control is todevelop oil sorbents that can remove oil from a spillsite completely. Based on the nature of rawmaterials, oil sorbents can be grouped into threemajor classes, namely inorganic minerals,synthetic organics, and natural organics. Acomprehensive review of this subject can be foundin Adebajo et alY>. Commercial oil sorbents

JKTI, Vol. 14, No.1, Juni 2012

mailto:E-mail:[email protected]

commonly used by many petroleum companies aresynthetic sorbents made of polypropylene andpolyurethane. They have good hydrophobic andoleophilic properties, but their non-bio~egradabi1ity is a major disadvantage,particularly because they need to be disposed ofproperly afteruse. This limitationhas led the searchfor alternative methods using biodegradablematerial such as lignocellulosic fibers ofagricultural residues or weeds. In many cases, thematerial is locally cheaply available, the maincosts being mainly those of collections andpreparation. It is much easier to compostlignocellulosic fibers than synthetic polymers afteruse'", which reduces the hazard and cost associatedwith incineration or other means of disposal.Moreover, cellulosic products exist in fibrous formand can be easily made into mats, pads, ornonwoven sheets?', A number of natural sorbentshave been studied for use in cleaning up oil spills.Some of them have good oil sorption capacity, butthey also adsorb water at the same time, which is adisadvantage when they are used in aqueousenvironment.

Several studies to find sorbentmaterials fromnatural organics with high oil sorption capacity,high hydrophobicity, and good buoyancy aredescribed below. Basically they can be groupedinto (1) explorations of new plant material and (2)chemical treatment of known plant material. Choiand Cloud'" found that milkweed floss (Asclepias)fiber adsorbed significantly larger amount of crudeoil (approximately 40 g oil/g fiber) than suchartificial fibers as nylon, polyester, acetate, viscoserayon, or polypropylene (typically below 25 glg)(5).Nonliving biomass of Salvinia sp.was identified toadsorb only 4.8 g crude oil/g biomass" and Suni et

(J) ,al. reported that cotton grass (Eriophorumvaginatum) removed up to 20 times its ownweightof diesel oil. Recently, Annunciado et al.(8) foundsilk floss (Chorisia speciosa) fibers to have a veryhigh oil sorption capacity (approximately 85 gig).Meanwhile, other research groups have been tryingto make some plant material more hydrophobic bychemical treatment: wood bark saturated withtransition metal ions(9-11>,acetylation of cottonfib (12,13)· (14)er ,nce straw ,and sugarcane bagasse(I5).~though these. chemical treatments significantlyunproved sorption capacity, the result was a moreexpensive sorbent product. Other important factorsthat need to be considered are local availability and


abundance of the ".,..._ ...•.==rii~spills, particularly in remotetransport bulky material to the site are liI::::::!i:C.Therefore, identifying such material for use as aclean-up tool for oil spills is of significantcommercial interest.

Cogon grass (Imperata cylindrica) wasranked as one of the ten worst weeds of the worldparticularly because it can spread, colonize, andsubsequently displace other desirable vegetation''",Cogon grass regenerates very rapidly from itsunderground rhizomes and responds withflowering to such control measures or forms ofstress as burning, overgrazing, drought, andrepeated slashing?", It grows in various ecosystemsfromthe dryto themoist natural areas, andhas beenreported as aweed in 73 countries,mostly inAfrica,Australia, southern Asia, and the Pacific'i", Thispaper discusses the potential use of Cogon grass asoil sorbent in cleaning up oil spills on land and inwater.

MATERIALAND METHODS

Sorbent materialThe grass was obtained from a plot of

marginal land in Serpong (Banten, Indonesia). Acommercial natural oil sorbent (peat Sorb), aprocessed peat, providedby a sales agent in Jakarta,was used for comparison. The grass was air-dried,its flowers (spikelets) were separated from thestem, and the stem was cut into pieces 2-4 mmlot;'-g.Peat Sorbwas ground in amill (Quacker CityMillmode14-G, Philadelphia,USA) and sieved in alaboratory test sieve (Retsch, Germany) to obtainparticles of 500--600 J.UD.. All such material wasstored in a dessicator; it was removed from thedesiccator and aired overnight at room temperaturebefore use. Moisture content of the grass flowersafter suchpretreatmentwas typically 60/0-8%.

Toquantifybuoyancy,25mg of grass flowerswas placed in a 1000 mL glass beaker containing500 mL water or a mixture of 450 mL water and50 mL oil and the contents stirred for 60 min at 72rpm. At the end of the test, the part that remainedafloat was removed, dried, and weighed tocalculate thebuoyancypercentage.

Specific gravity of the grass flowers wasmeasured using a picnometer with hexane (SG =

39

specific gravity was measured using a picnometer(Duran, 25 mL and 10 mL). In order to know thetendency of oil to evaporate, oil samples wereplaced in a glass dish 9 em in diameter and 1.5 emdeep, and the loss in weight after 24 hours ofstorage at room temperature and pressure wasrecorded.

Sorbents are generally not effective incleaning up highly viscous or heavy oils. These oilsdo not adhere to the sorbent readily owing to theirpoor wettability; on contact with water, highlyviscous oils tend to sink partly and heavy oils tendto sink completely. The oil should not be highlyvolatile either lest it should evaporate quickly. Thephysical characteristics of the oils used in theexperiment are shown in Table 1.

0.66) as the test fluid. This non-polar solvent wasused because ofits low specific gravity and becauseit apparently did not react with the flowers.

The BET (Brunauer, Emmett, Teller) valuefor the surface area for nitrogen sorption wasdetermined using aNova 1000 Quantachrome. Thismethod is often used as an indicator of the degree ofmicroporosity of sorbents. The measurements weretaken after the grass flowers had been immersed inliquid nitrogen and ground to powder in amortar, asBET suface area cannot be detemined directly forlarge particles.

Wettability of the grass flower by both oil andwater was estimated by the speed and extent towhich each liquid rises in a packed column of thematerial, known as the Washburn tesr'", Hexanerepresented a non-polar solution and water, a polarsolution. The method described by Ribeiro et al.(6)was followed with minor modifications. The grassflowers were packed manually in a glass tube (50em long with an inner diameter of 8 mm) closed atone end with a l-cm-thick plug of cotton.Approximately 1.5 g of the grass flower wasneeded to fill 44 em of the tube. This column wasthen dipped in a 1OOO-mLbeaker containing 300 mlofhexane or water, and the level of liquid rise insidethe tube was recorded as a function of time. Thezero time was started when the level of the liquid inthe tube reaching the level of the liquid inside thebeaker.

To measure the area of a cross section of abroken fiber of the grass flower, a scanning electronmicroscope (philips 515) was used. The specimenwas prepared by immersing the material into liquidnitrogen and grinding it to powder in a mortar.Gold-coated samples were then mounted on auniversal base and placed in a vacuum chamber at ahighpressure(1.3331O-2Paor 10-4Torr).

Test oilsThe following oils were used for the sorption

tests: light crude oil (Cemara crude oil), automotivediesel oil (Solar), lubricating oil (Mesran Super20W-50) obtained from Pertamina (a majorIndonesian petroleum company), and heavy crudeoil (petani crude oil) obtained from PT CPI(Chevron Pacific Indonesia). Kinematic viscositywas determined at 40°C by a viscometer (KoehlerInstruments, model K-23429, Germany) and

40

Table 1. Oil types and their properties

Oil types Specific Kinematic Weight loss

gravity viscosity (cSt)a (%)b

Petani crude oil 0.865 35.43 2

Cemara crude oil 0.824 1.90 20

Diesel oil 0.840 4.15 2

Lubricating oil 0.884 175.60 0

'viscosity at 40 "Cb after 24 hours at room temperature

All the oils had a specific gravity lower thanunity, and therefore they would not sink in water. At30°C, their viscosity was low enough so for them toadhere to the sorbents easily, with the exception ofPetani crude oil, which had to be warmed to 35°Cfor it to be fluid enough to be adsorbed. Data on oilvolatility show that during 20 minutes of thesorption experiment, the weight loss due toevaporation of oil was less than 0.3% of the originalweight. The above properties indicate that theseoils are suitable to be removed using sorbent as aclean-up tool.

SorptionexperbnenuTo assess the capacity of the biomass to

adsorb oil in absence of water (dry system), aprocedure specifically set for loose particulatesorbents was used?", The sorbent (0.25 g for grassand 1 g for Peat Sorb) was placed inside a wirebasket (pore size 150 J.IlD.), made of steel wire, 6.2cm in height and 4.5 em in diameter. The basket was


then dipped in a l-liter beaker containing 500 m1ofoil. Because it is bulky, smaller amount of grassflower was used in this experiment. The beaker wasin turn placed in an agitator (flocculation tester,SBS Instruments) and the liquid stirred at 100 rpmfor 20 minutes, considered long enough for thesorbent to be saturated with oil. The basketcontaining the sorbent was then raised, the oilallowed to drain by gravitation for 1minute, and thebasket weighed. An empty basket, subjected to thesame process to account for oil deposited ontometal surfaces, functioned as a blank. The amountof oil adsorbed was measured as the weight gainedafter sorption, expressed in grams per gram of drysorbent. All sorption tests were run at 30 DC±0.5 DC,except those for Petani crude oil, which were run at35DC± O.5DCbecause the oil is highly viscous.These temperatures were chosen to representambient temperature in the tropics.

In oil-water systems, only two types of oils(lubricating oil and Cemara crude oil) were furthertested to represent high- and low-viscosity oilsrespectively. The experiments were carried out atthree levels of mixing (static, gentle, and vigorous)in a 1000 mL glass beaker containing 450 mL tapwater and 50 mL oil. For static condition and gentlemixing, the grass flowers were poured onto thesurface of the oil and, after saturation, collected inthe metal basket described above. For staticcondition, the contents were not mixed at all; for. gentle mixing, intended to simulate waves in themarine environment, the beaker was shaken in anorbital shaker (Cole Parmer 51300-05) at 72 rpm.Vigorous mixing, to simulate the environment inwhich the oil is completely dispersed in water, wascarried out in a Dynamic Heidolph MR 2002 mixerand a stirring bar operating at 1000 rpm; the sorbentremained in the basket, the same as in dry oilsystem. The apparatus was observed every 20minutes over an hour to see the effect of contacttime on the amount of oil adsorbed. The sorbentsaturated with oil was then raised to allow theexcess oil to drain by gravitation for 4 minutes, andweighed. Longer time was provided for draining inthe oil-water system than the dry system to makesure that the sorbent was free of any drops of liquidadhering to it. Water was extracted from saturatedsorbent with fluids as described inAS'rM20

), using aDean-Stark glass still, with a mixture of xylene andtoluene (80:20, v/v) as a solvent. The results of allmeasurements were presented as average of threereplicates. The bars denote standard deviation ofthe replicates.


RESULTS AND DISCUSSION

Characteristics of the Cogon grass flower

The grass was identified at HerbariumBogoriense, Indonesian Institute of Sciences, asImperata cylindrica (L.) Beauv, known as Alang-alang or llalang (Indonesian) or Cogon grass(English).

(a) (b)

( c )

Figure 1. Cogon grass and its hairy flower: (a) Cogon grassgrowing on marginal land, (b) grass flower at x40magnification, (c) cross-section of the rod-likegrass flower fiber at xl 000 magnification showingthe fiber's hollow structure.

Figure 1 shows the morphology of the grassand a magnified image of flower parts. Figure lashows Cogon grass growing on a piece of marginalland. The plant is a slender, flat, linear-lanceolatestemless grass, less than a meter taIl, arising from athick underground mat of rhizomes. A completemorphological description of this grass can befound in Aguilar?", Figure lb shows thecharacteristics of a single hairy flower (spikelet)about 8-10 mm. long. Its snowy white colorsuggested a waxy coating. The importance of the

41

only in the internal lumen of a hollow fiber but alsowithin the voids (capillary bridges) between fibers.In our experiment, both mechanisms can beexpected to operate because of the presence of thehollow structure of the grass flower fiber shown inFigure le. Hexane, as a non-polar organic solvent,was used to represent various oils tested, whilewater represented the polar fluid.

waxy surface to the hydrophobic and oleophilicproperties of cotton and milkweed was reported byChoi and Cloud'"; it is believed to confer similarproperties on Cogon grass. Figure Ie shows thehollow structure (lumen) of the hairy parts of theCogon grass flower. The same kind of rod-like fiberfound in kapok, milkweed, and cotton has beendemonstrated to contribute to the high oil-sorptioncapacity owing to increased surface area andenhanced capillary action",

The grass flower was very bulky and itsdensity was estimated to be 0.66 glcm\approximately the same as that of hexane in whichthe grass flower dispersed evenly in the liquidphase. After saturation with oil, the volume of thegrass flower is usually smaller. Therefore, in itsapplication as oil sorbent, this material can becompacted to some extent, but not so much thatlittle space is left for the oil. After saturated with oil,the sorbent needs to remain buoyant in water forsome time to facilitate its collection. Observationsindicated that in the beaker containing only water,the grass flower remained above the surface of thewater but in the presence of oil, it wouldconcentrate in the oil phase above the water phase.The grass flowers remained in these positions evenafter 24 hours of gentle shaking that simulatedwaves, suggesting that the buoyancy was 100% forboth the grass flower in water and the grass flowersaturated with oil in the oil-water mixture.Buoyancy over such a long period is an importantfeature of the Cogon grass flower, making it easierto collect the grass and remove it from waterbodies. The value of BET surface area for nitrogensorption of the grass flower was estimated to be1.84 m2/g. This value was obtained for the grassflower in a powder form, as BET suface area forlarge particle cannot be detemined directly.

Wettability of the grass flower in oil or inwater is an important parameter when the sorbent isto be used in aquatic environment. A good oil-sorbent should adsorb a great deal of oil but only asmall amount of water. Wettability can be measuredin terms of the level offluid penetration in a columnfilled with powder or fiber. According to Perry andGreen'", the capillary action in such a system iscontrolled by the viscosity of the fluid, capillaryradius, surface tension between the liquid and air,contact angle between the liquid and solid surfaces,and time. In addition, Choi and Moreau'"demonstrated that capillary action took place not

42

~~--------------------------~o o He","""

C Wiler

100 8 .. ····--8··· .. ·.. ..£1D~_.IY--.•-tt ....{}..•...0-...•.g _..-9-.--.o~----~------~------~----~

o 101mTme(s)

150))

Figure 2. Hexane and water capillary rise in a tubepacked with Cogon grass flower.

70·------------------------------~~ 60~ 50 '-lJIg. 40

~ 30

"-g 20 -

'"o 10

o

• Water~ Diesel oilD Lubricating oila Petani crude oilo Cemara crude oil

Grass flower Grass stem Peat Sorb

Sorben! types

Figure 3. Sorption of water and oil by Cogon grass flower,flower stem, and Peat Sorb in water-only and oilonly systems.

A large difference in the level of penetrationof the fluids in the column between hexane (h2=400 em') and water (h2= 90 em') showed that thegrass flower is wetted far more easily by hexanethan by water (Figure 2), indicating that the grassflower has good wettability in oil and ishydrophobic and supporting the results shown inFigure 3, namely that the grass flower adsorbed asmuch as 57.9 g oillg but only a small quantity ofwater (1.5 gig). This oil sorption capacity is muchhigher than that of milkweed floss (40 gig) reportedby Choi and Cloud'",

Effect ofsorbent materials

Results of the experiment with the dry oilsystem, i.e. sorption characteristics of differentsorbents in an oil bath without the presence ofwater, are given in Figure 3. The experiment was


meant to simulate the cleaning up of an oil spill ondry land. The flower parts of the grass adsorbedmore lubricating oil (57.9 gig) than that adsorbedby the stem (5.9 gig) or by Peat Sorb (7.7 gig), acommercial natural oil sorbent based on peat. Otheroils (diesel and crude oils) were adsorbed in smaller2IDI:xmlts. In another part of this paper, it will be

preferences of some oils forsomeoow related to viscosity.

The greater '. capacity of the grass flowerthan the stem or Peat Sorb suggested 1hat thesurface area of the flowers was much larger thanthat of the other two. Also, the grass flower wasmore hydrophobic, retaining the least amount ofwater (1.5 gig), compared to the stem (9.2 gig) orPeat Sorb (5.9 gig). Hydrophobicity is an importantquality required of an effective sorbent for itsapplication in aquatic environment. Ribeiro et al. (6)and Annunciado et al.(8)used the same commercialproduct, Peat Sorb, for comparison. They found arather wide range of oil sorption capacity, from 2.7to 9.8 gig, and our result falls within this range.These differences occured possibly due tovariations in particle sizes of the pretreated PeatSorb and the types of oil tested.

Effect ofmixing in oil-water systemsExperimental results in the dry oil system and

in the oil-in-water system for high-viscosity oil(lubricating oil) and low-viscosity oil (Cemaracrude oil) are summarized in Figures 4 and Srespectively.

70

60 120min

tl 50~ 40min

<,tIi

"0 40 c~a 30~6 20

10

Dry Static Waved Stirred

Spill conditions

Figure 4. Sorption of high viscosity lubricating oil by Cogongrass flower under various spill conditions. Dry =oil only, stirred at 100 rpm; Static = oil in water, nomixing; Gentle Mixing = oil in water, shaken at 72rpm; Vigorous Mixing = oil in water, stirred at 1000rpm. 20, 40, 60 mins denote sorption period.


50Umin

~ 40- 140min-,tIi

~ 30 ~ DOmin~5~ 20'"6 10 -

Waled Stirred

Figure 5. Sorption of low viscosity crude oil by Cogon grassflower under various spill conditions. Dry = oil only,stirred at 100 rpm; Static = oil in water, no mixing;Gentle Mixing = oil in water, shaken at 72 rpm;Vigorous Mixing = oil in water, stirred at 1000 rpm.20, 40, 60 mins denote sorption period.

The highest amount of lubricating oil wasadsorbed in the dry oil system; in the presence ofwater, the amount of oil adsorbed decreasedslightly with static condition and gentle stirring, butsignificantly (up to 36%) with vigorous stirring.Similar trends were observed for Cemara crude oil.The dry-oil system adsorbed more oil because inthis case, most of the surface area of the grassflower was available for the oil whereas in theoil-water system, there was competition betweenwater and oil for the same surface areas, and parts ofthem would be occupied by water. Thesedifferences, however, were not significant, becausethe grass flower, being highly hydrophobic,adsorbed very small amount of water (Figure 3).

The different mixing regimes in theoil-water system affected the amount of oiladsorbed. The static system was a two-phasesystem where no mixing was involved; gentlemixing involved shaking at 72 rpm; and vigorousmixing involved stirring at 1000 rpm. As indicatedabove, only vigorous stirring significantly reducedthe amount of oil adsorbed (by 36%). This can beexplained as follows. The mixing enhanced masstransfer of air into the liquid phase and increaseddispersion of air bubbles. However, more vigorousstirring lead to more air bubbles, resulting inincreased resistance on part of the oil to attach to thesurface of the sorbent. In the static system or gentlystirred system, there were no air bubbles, and oilwas directly in contact with the sorbent all the time.

3

In the vigorous stirred system, a film of oil wouldform at the gas-water interface of the air bubbles,constituting a discrete phase. Consequently,contact between oil and the sorbent would occuronly when turbulence (the result of vigorousstirring) brought the sorbent and air bubbles inclose proximity. In addition, the diameter of the airbubbles was likely to be much larger than the poreopenings of the sorbent, preventing the air bubblesfrom penetrating and reaching the internal surfacesof the pores. The above factors influenced not onlythe amount of adsorbed oil but also the kinetics ofoil uptake at 20, 40, and 60 minutes. Figures 4 and 5show, beyond 20 minutes, the amount of adsorbedoil increased only slightly. Studies by Annunciadoet al.(8) also confirm that further observation up to 24hours did not result in any significant increase in oiluptake because the sorbent had almost reached itssaturation equilibrium by 20 minutes.

Effect of oil viscocityWhereas adsorption of oil onto sorbent

surfaces is dominated by hydrophobic interactionand van der Waals force, absorption takes placewithin the porous matrices by diffusion'", Besides,as previously mentioned, capillary movementswould also take place whenever the sorbentmaterial is in the form of fibers. All of the abovesorption mechanisms (wettability, diffusion inporous matrices, and capillary action) are known tobe affected by oil viscosity. In this study, within therange of viscosity tested, the amount of oiladsorbed by the grass flower suggests a directrelation to oil viscosity at the temperature ofcontact. Cemara crude oil, the least viscous (1.9cSt), was adsorbed the least (27.9 gig) whereaslubricating oil, the most viscous (175.6 cSt), wasadsorbed the most (57.9 gig).

CONCLUSIONS

It is concluded that the characteristics of thesorbent material, nature of oils, and spill conditionsinfluence the effectiveness of oil sorbent. Cogongrass (Imperata cylindrica) proved to be anexcellent oil-sorbent under different spillconditions. In addition to low cost, the grass is moreenvironment-friendly because it is relatively

44

biodegradable whereas synthetic polymers, thecommonly used alternative, are not. Grass flowersshowed high sorption capacity for various crudeoils and oil products because the flowers werehighly hydrophobic and easily wetted by oil. Thegrass material also showed good buoyancy evenafter 24 hours of shaking that simulated sea waves,suggesting the material's potential in combating oilspills not only on land but also in water.

ACKNOWLEDGEMENTS

The experiment was carried out at theResearch Center for Chemistry, LIPI, Puspiptek,Serpong. The authors would like to thank BPHMIOAS, PERTAMINA Jawa Barat and PT CPIJakarta for providing oil samples; also, Dian andRocky for laboratory assistance.

REFRENCES

1. M.O. Adebajo, RL. Frost, J.T. Kloprogge, o.Carmody, S. Kokot. Porous materials for oilspill cleanup: a review of synthesis andabsorbing properties. J. Porous Mat. 10: 159-170(2003).

2. K.S. Ro, O.A. Breitenbeck, A. Ohalambor.Composting Technology for Practical andSafe Remediation of Oil Spill Residuals,Louisiana Oil Spill Coordinator'sOffice/Office of the Governor, LouisianaApplied Oil Spill Research and DevelopmentProgram, Baton Rouge, Louisiana, TechnicalReport Series 97-009, 1998,44 p.

3. B.O. Lee, J.S. Han, RM. Rowell. Oil sorptionby lignocellulosic fibers, in: T. Sellers, N.A.Reichert (Eds.), Kenaf Properttes, Processingand Products, Mississippi State University,1999, pp. 423-433.

4. H. Choi, RM. Cloud. Natural sorbents in oilspill cleanup. Environ. Sci. Technol. 26(4):772-776 (1992).

5. H. Choi, J.P. Moreau. Oil sorption behavior ofvarious sorbents studied by sorption capacitymeasurement and environmental scanningelectron microscopy. Microsc. Res. Techniq.25: 447-455 (1993).


6. T.H. Ribeiro, RW. Smith, J. Rubio. Sorptionof oils by the nonliving biomass of a Salviniasp. Environ. Sci. Technol. 34: 5201-5205(2000).

7. S. Suni, A.L. Kosunen, M. Hautala, A. Pasila,M. Romantschuk. Use ofa by-product of peatexcavation, cotton grass fibre, as a sorbent foroil-spills. Mar. Pollut. Bull. 49: 916-921(2004).

8. T.R. Anmmciado, T.H.D. Sydenstricker, S.C.Amico. Experimental investigation of variousvegetable fibers as sorbent materials for oilspills. Mar. Pollut. Bull. 50(11): 1340-1346(2005).

9. M. Haussard, I. Gaballah, P.D. Donato, O.Barres. Removal of hydrocarbons fromwastewater using treated bark. J. Air WasteManage. 51: 1351-1358(2001).

10. M. Haussard, I. Gaballah, P.D. Donato, O.Barres. Use of treated bark for the removal oflipids from water. J. Air WasteManage. 52:76-83 (2002).

11. M. Haussard, I. Gaballah, N. Kanari, P.D.Donato, O. Barres, F. Villieras. Separation ofhydrocarbons and lipid from water usingtreated bark. Water Res. 37: 362-374(2003).

12. G. Deschamps, H. Camel, M.E. Borredon, C.Bonnin, C. Vignoles. Oil removal from waterby selective sorption on hydrophobic cottonfibers. 1. Study of sorption properties andcomparison with other cotton fiber-basedsorbents. Environ. Sci. Technol. 37: 1013-1015 (2003).

13. M.O. Adebajo, RL. Frost. Acetylation of rawcotton for oil spill cleanup application: anFTIR and 13C MAS NMR spectroscopicinvestigation. Spectrochim. Acta A 60(10):2315-2321 (2004).

14. X.F. Sun, RC. Sun, J.X. Sun. Acetylation ofrice straw with or without catalysts and itscharacterization as a natural sorbent in oil spillcleanup. J. Agr. Food Chem. 50(22): 6428-6433 (2002).

15. X.F. Sun, RC. Sun, J.X. Sun. A convenientacetylation of sugarcane bagasse using NBSas a catalyst for the preparation of oil sorption-active materials. J. Mater. Sci. 38(19): 3915-


3923 (2003).

16. A.N. Van Loan, J.R Meeker, M.C. Minno.Cogon grass, in: R Van Driesche, S. Lyon, B.Blossey, M. Hoddle, R Reardon (Eds.),Biological Control of Invasive Plants in theEastern United States, USDA Forest ServicePublication FHTET-2002-04, Morgantown,West VIrginia, 2002, pp. 353-364.

17. D. Chikoye. Characteristics and managementof Imperata cylindrica (L.) Raeuschel insmallholder farms in developing countries, in:R Labrada (Ed.), Weed Management forDeveloping Countries (Addendum 1), FAOPlant Production and Protection Papers,Rome, 2003, 290 p.

18. RH. Perry, D.W. Green. Perry's ChemicalEngineers' Handbook, seventh ed., McGraw-Hill, New York, 1997.

19. ASTM F726-82. StandardMethod of TestingSorbent Performance of Adsorbents,American Society of Testing and Materials,Philadelphia,PA, 1994.

20. ASTM D95-83. Standard Test Method forWaterin Petroleum Products and BituminousMaterials by Distillation, American Societyof Testing and Materials, Philadelphia, PA,1990.

21. N.O. Aguilar. Imperata cylindrica (L.)Raeuschel in: L. 'tMannetje, R.M. Jones(Eds.), Plant Resources of South-EastAsia No4: Forages, PROSEA Foundation, Bogor,Indonesia, 1992, pp 140-142.Jatamason inPoly herbal Formulation, International JournalofChemTech Research CODEN (USA), 1 (4),1079-1086.

19. M.D. Phale, P.D. Hamrapurkar, M.A.Chachad, 2010, Precise and Sensitive HPTLCMethod for Quantitative Estimation ofWedelolactone in Eclipta Alba Hassk,Pharmacophore, 1 (2), 103-111.

20. N.S. Wani, T.A. Desmukh, vn, Patil, 2010, ARapid Densitometric Method forQuantification of Wedelolactone in HerbalFormulation using HPTLC, J. Chem. Metro!'4(1),28-33.

21. K. Savita, K. Prakashchandra, 2011,Optimization of Extraction Conditions and

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24. K. Danzer 2010, Analytical Chemistry,Theoretical and Metrological Fundamentals,Springer-Verlag,BerlinHeidelberg.

25. AOAC, 2000, OfficialMethods ofAnalysis ofAOAC International, 17 th ed, AOACInternational, Gaithersburg,Maryland,USA.

26. ICH-Q2B, 1996, Validation of AnalyticalProcedures: Methodology, Guidance forIndustry, International Conference ofHarmonization,Geneva.

27. T. Farrant, 1997, Practical Statistic for theAnalytical Scientist, The Royal Society ofChemistry,LGCTeddington,Cambridge.

Development of Sensitive HPTLC Methodfor Estimation of Wedelolactone in differentextracts of Eclipta alba, International Journalof Pharmaceutical Sciences and DrugResearch, 3(1): 56-61.

22. M.N. Prajapati, T.A. Deshmnkh, va, Patil,B.K. Shrikhande, 2011, Development andValidation of HPTLC Method forSimultaneous Determination ofWedelolactoneandPhyllanthin inHepasuportTablet,DerPharmacia Sinica,2(4):140-147.

23. H. Yuan,Yunli, Zhao, Xiaoying, Wang, QianTang, Xiaoxia Gao, Zhiguo Yu, 2007,Simultaneousdetermination ofwedelolactoneand isodemetil-wedelolactone in herba ecliptaby reverse-phase high performance liquidchromatography,SePu, 25(3), 371-373.

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potential ofcogon grassasanoilsorbent

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