Utilization of Recycled Rayon Waste-Kapok Mixture (RRWK) as a sorbent for oil removal

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1 Utilization of Recycled Rayon Waste-Kapok Mixture (RRWK) as a sorbent for oil removal Chaowalit Senanurakwarkul, Panadda Kongsricharoen, Darathip Pejprom, Sutha Khaodhiar, Supawan Tantayanon Abstract The aim of this study was to investigate the utilization of a recycled rayon waste-kapok mixture as an oil sorbent for the removal of diesel and motor oil. The oil-sorption capacity of the materials under static conditions was evaluated. The results show the high sorption capacity of the recycled rayon waste-kapok mixture for both diesel and motor oil after 15 minutes (14.30 g of oil/g of sorbent for diesel oil and g of oil/g of sorbent for motor oil) and after 24 hours (15.30 g of oil/g of sorbent for diesel oil and g of oil/g of sorbent for motor oil). It can be concluded that RRWK, which can be produced by utilizing industrial waste, is an effective low cost, environmentally friendly oil sorbent with comparable performance to commercial products. Keywords Recycled rayon waste-kapok mixture, oil sorbent. I. INTRODUCTION A. Oil in the environment and oil spill cleanup method IL is an important energy source and a raw material for Othe synthesis of various products. Whenever oil is extracted, transported, and stored, and its derivatives are used, there is a risk of spillage with the potential to cause a significant environmental impact. Oils that are found in contaminated water and land can be heavy hydrocarbons such as crude oils, and bunker C, and/or light hydrocarbons such as diesel, jet fuel, and gasoline. The major sources of oily waste come from industries such as petroleum refineries and manufacturing [7]. The basic methods for oil spill collection and cleanup are chemical treatment, mechanical treatment and biological treatment. Chaowalit Senanurakwarkul, Technopreneurship and Innovation Management program, Graduate School, Chulalongkorn University, Bangkok 10330, Thailand Thailand (corresponding author to provide phone: (662) ; fax: (662) ; ( Sutha.k@chula.ac.th). Panadda Kongsricharoen, Department of Environmental Engineering, Chulalongkorn University, Bangkok 10330, ( Panadda.k.p@Student.chula.ac.th). Darathip Pejprom, Department of Environmental Engineering, Chulalongkorn University, Bangkok 10330, Thailand ( Darathip.p@Student.chula.ac.th). Sutha Khaodhiar, Department of Environmental Engineering, Chulalongkorn University, Bangkok 10330, Thailand ( Sutha.k@chula.ac.th). Supawan Tantayanon, Department of Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand, Center of Petroleum and Advanced Material, Chulalongkorn University, Bangkok 10330, Thailand, Technopreneurship and Innovation Management, Graduate School, Chulalongkorn University, Bangkok 10330, Thailand. ( Supawan.t@chula.ac.th). The mechanical method involves the transfer of oil from spill site to temporary storage using oil sorbents or skimmers. Oil sorbents can be classified into organic, inorganic, and synthetic organic products [10]. Good oil sorbents are characterized by high sorption capacity, good buoyancy, adequate oil retention, and reusability [5]. The most common materials used for oil sorbents are synthetic materials such as polypropylene or polyurethane [2]. They have high oleophilic and hydrophobic properties, but they are considered nonbiodegradable and are relatively expensive [3]. Thus, many researchers have become interested in studying natural inorganic and organic materials to find substitution materials for oil spill cleanup. B. Rationale for using industrial waste and kapok as an oil sorbent in the study The rayon industry generates many kinds of wastes including viscose liquid, rayon fibers, and sodium sulfate. Most of these wastes are classified as hazardous waste and must be disposed of in secure landfills. Rejected viscose liquid is one of the waste products from the viscose preparation process and maintenance activities such as filtering, sample collecting, process shutdown, and overflow. The viscose liquid contains NaOH, water, and pulp, which are mixed homogeneously by the viscose process. Rayon fiber is produced from wood pulp. The rayon fiber waste is generated by the drying machine. The rayon fiber is a modified cellulose fiber that is capable of absorbing crude oil [8]. Sodium sulfate, a by-product of the rayon industry, is usually used for the production of hygiene products such toothpaste and detergent powder. The sodium sulfate waste comes from leakages from packages during transportation and handling. It can be dissolved in water and can be used to increase the porosity of material. [9] found that sodium sulfate increased the porosity of the cellulose sponge oil sorbent that was made from viscose mixed with cotton and used for testing oil adsorption. Kapok fiber is an agricultural product which has been used as an oil sorbent material. The kapok fibers are fluffy, yellowishbrown, lightweight, inelastic, and brittle. It has a rich oiliness and is inelastic so it cannot be spun. The sorption capacity of loose kapok was reported to be as high as 45 g of oil/g of sorbent for diesel and 115 g of oil/g of sorbent for motor oil (HD -30) [13]. In this study, the waste generated from the manufacture of rayon, including viscose liquid, waste rayon fiber, and sodium sulfate, were blended with kapok to develop the materials that 9

2 were qualified as an oil sorbents. These were then tested for oil sorption efficiency and compared with synthetic oil sorbents following the ASTM F Standard Test Method for Sorbent Performance of Adsorbent. II. MATERIALS AND METHOD A. Oil adsorbent material made of recycled rayon wastekapok mixture ( RRWK) In this study, a viscose solution was prepared by mixing rejected viscose liquid with water in the ratio 1:6 (wt). The fiber material was prepared by mixing kapok fibers and rayon fibers in a 1:1 weight ratio. The viscose solution and the prepared fiber were mixed, and 25 grams of sodium sulfate salt (size 150 microns) were added to the mixture. The mixed material was placed in a mixing machine and blended thoroughly for 1 minute. After that, the mixed material was put into a container and washed with 10 % sulfuric acid for 30 minutes. Next, the prepared material was rinsed with water for 1 minute, and then dried in a drying machine at 60 C for 24 hours. The prepared sorbent material was a lightweight fiber with a brown and white color as shown in Figure 2. Fig. 2 Recycled Rayon Waste-Kapok Mixture(RRWK) sorbent B. RRWK sorbent characterization The kapok fiber, rayon fiber, and RRWK physical characteristics and diameter were analyzed using a Scanning Electron Microscope (SEM, JEOL type JSM-5410LV). The surface areas of the materials were measured using a Surface Area Analyzer (Quantachrome, Autosorb-1) (a) (b) C. Properties of oil Two types of oil, diesel oil and motor oil SAE 20W 50, were used to evaluate oil sorption in this study. The diesel oil and motor oil were purchased from PTT (Thailand) Co., Ltd. Diesel oil is representative of low-viscosity oils such as gasoline and kerosene. Motor oil is representative of mediumviscosity oils such as crude oil. Viscosities were measured using a Viscometer (Brookfield / LVDV III). The characteristics of the investigated oils are summarized in Table I TABLE I PHYSICAL PROPERTIES OF THE INVESTIGATED OILS AT 25 C Type of oil Density ( kg/m 3 ) Viscosity (cp) Diesel oil Motor oil *Oil densities were obtained from the product specifications provided by the manufacturer. (c) Fig.1. The materials used for oil sorbent. (a) Rejected viscose, (b) Rayon fibers, (c) Kapok fibers, (d) Sodium sulfate (d) D. Oil sorption study The procedure for determining oil sorption capacity generally followed the ASTM F method. Loose-form RRWK was placed inside a wire-mesh basket and immersed inside an oil bath until it reached the test time limit as detailed below. Short test (15 minutes) under static conditions: 50 grams of motor oil and diesel oil were poured into a beaker. Thereafter, 5 grams of RRWK were put in a screen and placed on the oil surface. After 15 minutes, the material was removed using forceps and drained for 30 seconds. Long test ( 24 hours) under static condition: 50 g of motor oil and diesel oil were poured into a beaker. Thereafter, 5 grams of RRWK were put in a screen and placed on the oil surface. After 24 hours, the material was removed using 10

3 forceps and drained for 30 seconds. The oil-sorbed material was weighed. The oil sorption capacity was determined using the following equation as in (1). q = S t S 0 (1) S 0 Where, q is the sorption capacity (g of oil/g of sorbent), S t is the total mass of the sorbed samples (g), and S 0 is the initial mass of the sorbed materials. III. RESULTS AND DISCUSSION A. Characteristics of the materials Kapok fiber Raw kapok had a hollow microstructure (or lumen) as shown in the SEM image in Figure 3, with an average external diameter of 21.5 micrometers and an internal diameter of 19.5 micrometers. These results are similar to those previously reported by Lim and Huang [11]. Raw kapok fiber has a smooth surface and contains waxy cutin which makes it water repellence [12]. Kapok is hydrophobic as water cannot easily penetrate into the lumen because of the negative capillary between the water and the kapok fiber wall, and the large surface tension against air in lumen [10]. Fig. 4 A SEM image of rayon fiber Recycled Rayon Waste-Kapok Mixture (RRWK) RRWK (50 % rayon fiber / 50 % kapok fiber) sorbent material was produced from rayon industrial wastes and natural kapok fiber. Scanning Electron Microscope (SEM) images (Figure 5) of RRWK show that the sorbent consists of kapok fibers and rayon fibers, which are arranged in rows with spaces between the fibers. The BET surface area of RRWK was 5.54 m 2 /g. (a) Fig. 3 A SEM image of kapok fiber Rayon fiber Figure 2 shows a SEM image of rayon fiber. The fiber structure consists of a combination of small fibers that lack a hollow internal structure. The average external diameter was 9.37 micrometers. Rayon's cellulosic base results in many properties similar to those of cotton or other natural cellulosic fibers [8]. (b) Fig. 5 SEM images of RRWK (a) Side view, (b) Top view 11

4 B. Oil sorption capacity The sorption capacities of RRWK for diesel oil and motor oil under static conditions after 15 minutes and 24 hours are presented in the Table II. The oil sorption measurements after 15 minutes for RRWK were g of oil/g of sorbent for diesel oil and g of oil/g of sorbent for motor oil. The oil sorption measurements after 24 hours for RRWK were g of oil/g of sorbent for diesel oil and g of oil/g of sorbent for motor oil. The sorption results the tested oil after 15 minutes and 24 hours were not significantly different because of its ability to absorb oil up until its maximum limits in a very short time. The sorption of diesel oil and motor oil were different probably because of the differences in oil viscosity. [6] reported that oil with higher viscosity tends to have a higher initial sorption ratio. As predicted therefore, motor oil, which is more viscose than diesel oil, showed much greater sorption by RRWK. TABLE II CAPACITY FOR OIL SORPTION Type of oil Viscosity Oil sorption (15 min.) Oil sorption (24 hrs.) ( cp) g of oil / g of sorbent g of oil / g of sorbent Diesel oil Motor oil C. Comparison with other oil sorbents Oil sorption capacity values of different oil sorbents for motor oil are listed in Table III. * Static conditions TABLE III OIL-SORPTION CAPACITY OF VARIOUS SORBENTS Sorbent Oil Sorption capacity Reference ( g of oil / g of sorbent ) RRWK Motor oil This study Polypropylene Motor oil This study Natural wool fibers Recycled wood-based nonwoven material Silkworm cocoon waste Motor oil 20 [4] Motor oil [5] Motor oil [4] In this study, RRWK showed a higher sorption capacity than polypropylene. When compare with other studies, RRWK has a greater sorption capacity than natural wool fibers and recycled wood-based nonwoven material, but a lower sorption capacity than silkworm cocoon waste. This indicates that RRWK has a higher oil sorption capacity. However, for any valid and accurate comparison, other factors should be taken into account such as the type of oil, the experimental method, and the shape of the material IV. CONCLUSION A recycled rayon waste-kapok mixture (RRWK) can be used for the sorption of different types of oil (diesel oil and motor oil) under static condition. Oil with a higher viscosity tends to have a higher initial sorption ratio. The SEM images of RRWK showed that fiber structure affects oil sorption due to the hollow lumen and the gap between the fibers. RRWK displayed a capacity for oil sorption that was higher than polypropylene. It can be concluded that utilizing industrial waste to produce RRWK is an effective way to create low cost, environmentally friendly oil sorbents. ACKNOWLEDGMENT This research was supported by research scholarship " 90th Year Chulalongkorn Scholarship" from the Ratchadapiseksomphote Fund, Chulalongkron University. The authors wish to thank Thairayon Public Company (Thailand) for supporting these rayon industrial wastes. REFERENCES [1] American Society for Testing and Materials, Standard Test Method for Sorbent Performanceof Adsorbent, ASTM Philadelphia, USA. [2] CH. Teas, S. Kalligeros, F. Zanikos, S. Stournas, E. Lois, G. Anastopulos, Investigation of the effectiveness of absorbent material in oil spill clean up, Desalination 140 (2001) [3] H.-M. Choi, R.M. Cloud, Natural sorbents in oil spill cleanup, Environmental Science & Technology, 26 (1992) [4] Hiroshi Moriwaki, Shiori Kitajima, Masahiro Kurashima, Ayaka Hagiwara,Kazuma Haraguchi, Koji Shirai, Rensuke Kanekatsu, Kenji Kiguchi, Utilization of silkworm cocoon waste as a sorbent for the removal of oil from water, Journal of Hazardous Material, (2008). [5] M. Radetic, V. Ilic, D. Radojevic, R. Miladinovic, D. Jocic, R. Jovancic, Efficiency of recycled wool-based nonwoven material for the removal of oils from water, Chemosphere 70 (2008) [6] Q.F. Wei, R.R. Mather, A.F. Fotheringham, R.D. Yang, Evaluation of nonwoven polypropylene oil sorbents in marine oil-spill recovery, Marine Pollution Bulletin. 46 (2003) [7] Quemeneur, M., Marty, Y., Fatty acids and sterols in domestic wastewater, Water Research 28 (5), [8] R.F. Johnson, T.G. Manjrekar, Removal of oil from water surfaces by sorption on unstructured fibers, Environmental Science & Technology. 7 (1973) [9] Sanderson Alan, Dove Rod., Ming Fang, Howell John, 1997, Crosslinked cellulose sponge, United State Patent [10] T.T. Lim, X. Huang, Evaluation of kapok (Ceiba pentandra (L.) Gaertn.) as a natural hollow hydrophobic-oleophilic fibrous sorbent for oil spill cleanup, Chemosphere 66 (5) (2007) [11] T.T. Lim, X. 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5 Chaowalit Senanurakwarkul received his B.Sc. in occupational health and safety from Faculty of Public Health, Mahidol University,Thailand, his M.Sc. industrial hygiene and safety from Faculty of Public Health, Mahidol University, Thailand. He is currently Ph.D. student in Technopreneurship and Innovation Management program, Chulalongkorn University, Thailand. His research interest focuses on innovative oil sorbent for oil removal. Panadda Kongsricharoen received her B.Sc. in chemistry from faculty of science, Prince of Songkla University, Thailand, She is currently M.Sc. student in environmental engineering program, Chulalongkorn University, Thailand. Her research interest focuses on the development of oil sorbent from kapok fiber and rayon industrial waste. Darathip Pejprom received her B.Sc. in environmental science from faculty of science and technology, Thamasat University, Thailand, She is currently M.Sc. student in environmental engineering program, Chulalongkorn University, Thailand. Her research interest focuses on the adsorption of BTEX by kapok fiber and rayon industrial waste. Sutha Khaodhiar received his B.E. in environmental engineering from Chulalongkorn University, Thailand, and his M.Sc. and Ph.D. in environmental engineering from Oregon State University. He is currently an associate professor in the Department of Environmental Engineering, Chulalongkorn University. His research interest focuses on complex reactions of contaminants in aqueous environments. Supawan Tatayanon received her B.Sc. honour (Chemistry) from Chulalongkorn University, Thailand, and her M.Sc. (Organic Chemistry), Mahidol University,Thailand and Ph.D. in (Organic Chemistry), Worcester Polytechnic Institute,U.S.A.. She is currently an associate professor in the Department of Chemistry, Faculty of Science, Chulalongkorn University. Her research interest focuses on Enhanced Toughening Polypropylene with Reclaimed Tire-Rubber 13