Investigation of Oleophilic Nature of Straw Sorbent Conditioned in Water EDYTA WITKA-JE _ ZEWSKA, JAN HUPKA* ,1 & PIOTR PIENIA z _ ZEK 2 Department of Chemical Technology, Technical University of Gda nsk, 80-952 Gda nsk, Poland Absorptive potential of barley straw conditioned in water with respect to the properties of interior and exterior surface of the stalk and leaf is discussed. The contact angle for water and decane, both on dry and wet straw was measured. The internal and external surface of the stalk as well as of the leaf remained preferentially oleophilic when dry, regardless of the straw decomposition time. In the case of straw con- ditioned in water the external stalk surface exhibited oleophilic properties for 10 days whereas that of the leaf for seven days. During decomposition a wax layer on epidermis was removed. Decreasing accuracy of contact angle determination after 14 days of decomposition was caused by growth of microorganisms on the straw surface. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Barley straw, contact angle, oil spill containment, sorbents Introduction Straw is a renewable substrate for production of cellulose, glucose alcohol and other chemical com- pounds. Straw was also successfully employed in compost prism construction and as a renewable fuel (Iwulski & Piechocki, 1998). Straw, being easily available, is often used during containment and clean up of oil spills (Hupka, 1979; Hupka & Paczkowski, 1981). A thin wax layer covering stalks and leaves of cereals is composed of esters, long chain fatty acids and monohydroxy alcohols (Warth, 1960), therefore straw should favorably sorb hydrophobic liquids. Waxes are insoluble in water, thus the coating on ex- ternal surfaces of stems, leaves, flowers, fruits and seeds protects them from excessive water evaporation or outer moisture. Waxes also protect plants from microorganisms and mechanical damage. Wax coating aids the process of crop ripening by preventing stalks from becoming moist again. Straw behavior in water and its sorption properties are directly related to our research on inhibition of algae growth by barley straw. Straw decomposing in aerobic conditions restricts algae and cyanobacteria bloom (Barrett et al., 1994; Barrett & Newman, 1993; Ridge & Barrett, 1992; Welch et al., 1990). Our findings also indicate that straw decomposing in fishing nets is rapidly inhabited by organisms feeding on suspended matter (Witka-Je _ zewska & Hupka, 1998; Witka-Je _ zewska, 2002). Boom made of straw placed on current water managed to stop foam and suspended particles (increase of transparency and reduced COD below the boom was noticed). Boom made of straw can be considered in emergency oil clean up. Earlier studies (Witka-Je _ zewska, 2000) showed that after 10–20 days, depending on sample preparation, water displaced the gas phase from straw, which resulted in a loss of buoyancy. The aim of this work was to investigate oleophilic properties of straw conditioned in water by measurement of contact angles. 561 Spill Science & Technology Bulletin, Vol. 8, Nos. 5–6, pp.561–564, 2003 Ó 2003 Elsevier Ltd. All rights reserved Printed in Great Britain 1353-2561/$ - see front matter doi:10.1016/S1353-2561(03)00069-0 *Corresponding author. Chemical Faculty, Gda nsk University of Technology, 80-952 Gda nsk, Poland. Tel.: +48-58-3471792; fax: +48-58-3472065. E-mail address: jhupka@chem.pg.gda.pl (J. Hupka). URL: http://techno4.chem.pg.gda.pl/. 1 On leave from Technical University of Gda nsk. 2 Student of ChemistÕs Scientific Society.