Journal of Hazardous Materials 148 (2007) 122–135 Cement-based stabilization/solidification of oil refinery sludge: Leaching behavior of alkanes and PAHs Athanasios K. Karamalidis 1 , Evangelos A. Voudrias ∗ Department of Environmental Engineering, Democritus University of Thrace, GR 671 00 Xanthi, Greece Received 7 July 2006; received in revised form 2 February 2007; accepted 7 February 2007 Available online 15 February 2007 Abstract Stabilization/solidification is a process widely applied for the immobilization of inorganic constituents of hazardous wastes, especially for metals. Cement is usually one of the most common binders for that purpose. However, limited results have been presented on immobilization of hydrocarbons in cement-based stabilized/solidified petroleum solid waste. In this study, real oil refinery sludge samples were stabilized and solidified with various additions of I42.5 and II42.5 cement (Portland and blended cement, respectively) and subject to leaching. The target analytes were total petroleum hydrocarbons, alkanes and 16 polycyclic aromatic hydrocarbons of the EPA priority pollutant list. The experiments showed that the waste was confined in the cement matrix by macroencapsulation. The rapture of the cement structure led to the increase of leachability for most of the hydrocarbons. Leaching of n-alkanes from II42.5 cement-solidified samples was lower than that from I42.5 solidified samples. Leaching of alkanes in the range of n-C 10 to n-C 27 was lower than that of long chain alkanes (>n-C 27 ), regardless the amount of cement addition. Generally, increasing the cement content in the solidified waste samples, increased individual alkane leachability. This indicated that cement addition resulted in destabilization of the waste. Addition of I42.5 cement favored immobilization of anthracene, benzo[a]anthracene, benzo[b]fluoroanthene, benzo[k]fluoroanthene, benzo[a]pyrene and dibenzo[a,h]anthracene. However, addition of II42.5 favored 5 out of 16, i.e., naphthalene, anthracene, benzo[b]fluoroanthene, benzo[k]fluoroanthene and dibenzo[a,h]anthracene. © 2007 Elsevier B.V. All rights reserved. Keywords: Stabilization; Solidification; Cement; Alkanes; PAHs; Leaching; Refinery oily sludge; Alkane quantification 1. Introduction Cement-based stabilization/solidification (S/S) is a widely applied and well-established technique for the immobilization of inorganic hazardous constituents. Many industrial wastes are well treated with this cost-effective technology. However, solidification technology has run into difficulties when trying to solidify organic wastes [1,2]. In a well solidified prod- uct, hazardous contaminants are chemically immobilized in the cement hydration products or physically entrapped by encapsu- lation. The resulting solidified specimen has improved structural integrity and physical characteristics. Oily materials are the primary source of waste for most refineries and are generated when oil coalesces on solids. ∗ Corresponding author. Tel.: +30 25410 79377; fax: +30 25410 79376. E-mail addresses: akaramal@env.duth.gr (A.K. Karamalidis), voudrias@env.duth.gr (E.A. Voudrias). 1 Tel.: +30 25410 79395; fax: +30 25410 79376. Because the oil acts as an adhesive, 1 kg of crude oil can generate 10–20 g of residue. Oily residues are collected at several points within the refinery, such as oil/water separators, dissolved air flotation units, heat exchanger cleanings, and tank bottom clean- ings [3]. The use of cement-based stabilization/solidification as a treatment process can restrain the inorganic species mobil- ity. However, the leaching behavior of organic compounds from treated industrial wastes is still under investigation. It has been reported that the solidification of organic loaded wastes often produces materials with poor strength character- istics [1]. If organics are admixed with cement (e.g. phenols [4]), they would affect the cement hydration kinetics by retard- ing the reactions via formation of a protective film around the cement grain, hindering the formation of calcium hydroxide, and accelerating the reaction of modification of the colloidal C–S–H (C: CaO, S: SiO 2 , H: H 2 O) gel precipitated at very early stages around the cement grains [5,6]. Some examples have been reported, 3-chlorophenol retards the hydration of cement paste and stabilizes the ettringite phase, slowing its 0304-3894/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2007.02.032