Solar Energy Vol. 66, No. 6, pp. 395–399, 1999 1999 Elsevier Science Ltd  Pergamon PII: S0038–092X(99)00038–9 All rights reserved. Printed in Great Britain 0038-092X / 99 / $ - see front matter www.elsevier.com / locate / solener PHOTOCATALYTIC PURIFICATION OF SOIL CONTAMINATED WITH OIL USING MODIFIED TiO POWDERS 2 ² MACIEJ HAMERSKI, JOANNA GRZECHULSKA and ANTONI WALDEMAR MORAWSKI Department of Water Technology and Environmental Protection, Institute of Inorganic Chemical Technology, Technical University of Szczecin, ul. Pul «askiego 10, 70-322 Szczecin, Poland Received 1 December 1998; revised version accepted 24 March 1999 Communicated by GION CALZAFERRI Abstract—Photocatalysts based on titanium dioxide were used for the purification of contaminated soil polluted by oil. Commercially produced slurry of titanium dioxide was modified with barium, potassium and calcium. The experiments were performed under natural conditions in summer months (July and August), applying direct solar light, which occurs in Poland. The preparation of photocatalyst samples and the experimental results obtained from the photocatalytic oil decomposition in the soil are presented. The most active photocatalyst for soil purification was titanium dioxide modified with calcium.  1999 Elsevier Science Ltd. All rights reserved. 1. INTRODUCTION vironment and high costs. Hence, it is necessity to search for alternative or complementary methods In recent years, increasing ecological problems, for removing oil derivatives from the environ- connected with the presence of oil derivatives in ment. the natural environment are observed. A serious In recent years, there have been many publi- problem connected with purification of soil con- cations connected with the application of semi- taminated with oil derivatives, especially in conductors as photocatalysts, and solar energy as former military bases is currently faced in Poland. an activator of the process of organic pollutants Oil derivatives are classified into the group of the degradation (Bahnemann et al., 1993; Blake, most dangerous compounds for the environment. 1994; Bolton, 1996; Chen et al. 1995; Goswami As a consequence of the large migrational and Blake, 1996; Matthews, 1985; Nogueira and abilities of these compounds, both in aquatic and Jardim, 1996; Ollis and Al-Ekabi, 1993; Pacheco land environments, the prevention of uncontrolled et al., 1993; Parent et al., 1996; Schiavello, spreading and the removal of the results of leaks 1988). is difficult. Most publications are addressed to the Titanium dioxide can be used pure or with problem of removing oil pollutants from the various additives (Choi et al., 1994; Martin et al., aquatic environment (Rosenberg et al., 1992; 1994). Choi et al. (1994) stated that the activity of Turchi et al., 1993; Turchi and Mehos, 1992; the photocatalyst is related to the dopant ion Berry and Mueller, 1994). The removal of oil electron configuration and the dopant ions with from soil is still a new and rarely discussed closed electron shells have little or no effect on problem. the activity. The conventional methods currently used for In our studies we modified titanium dioxide the removal of oil derivatives (such as: combus- with metals of AI and AII family of the periodic tion, extraction, biological methods) are not per- table. As published earlier, these photocatalysts fect. Their disadvantages are: low efficiency, long were active (more active than pure titanium time of the process, secondary pollution of en- dioxide) in the reaction of degradation of organic pollutants such as oil (Karakulski et al., 1998) and phenol in water. The objective of this work was to study the ² Author to whom correspondence should be addressed. Tel.: utilisation of the photocatalytic process activated 1 48-914-494-474; fax: 1 48-914-330-352; e-mail: amor@mailbox.tuniv.szczecin.pl with sunlight for purification of soil contaminated 395