Journal of Hazardous Materials 175 (2010) 382–392 Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Characterization of acid tars Sunday A. Leonard a,∗ , Julia A. Stegemann a , Amitava Roy b a Department of Civil Environmental and Geomatic Engineering, University College London, Chadwick Building, Gower Street, London, WC1E 6BT, United Kingdom b J. Bennett Johnston, Sr., Centre for Advance Microstructures and Devices (CAMD), 6980 Jefferson Highway, Louisiana State University, Baton Rouge, LA, 70806, USA article info Article history: Received 30 July 2009 Received in revised form 4 October 2009 Accepted 5 October 2009 Available online 12 October 2009 Keywords: Acid tars Leaching PAH Aliphatic hydrocarbons Heavy metals Analytical techniques abstract Acid tars from the processing of petroleum and petrochemicals using sulfuric acid were character- ized by gas chromatography/mass spectrometry (GC/MS), inductively coupled plasma/optical emission spectrometry (ICP/OES), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectrometry, and scanning electron microscopy/energy dispersive X-ray (SEM/EDX) micro-analysis. Leaching of contaminants from the acid tars in 48 h batch tests with distilled water at a liquid-to-solid ratio 10:1 was also studied. GC/MS results show that the samples contained aliphatic hydrocarbons, cyclic hydrocarbons, up to 12 of the 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs), and numer- ous other organic groups, including organic acids (sulfonic acids, carboxylic acids and aromatic acids), phenyl, nitrile, amide, furans, thiophenes, pyrroles, and phthalates, many of which are toxic. Metals anal- ysis shows that Pb was present in significant concentration. DSC results show different transition peaks in the studied samples, demonstrating their complexity and variability. FTIR analysis further confirmed the presence of the organic groups detected by GC/MS. The SEM/EDX micro-analysis results provided insight on the surface characteristics of the samples and show that contaminants distribution was het- erogeneous. The results provide useful data on the composition, complexity, and variability of acid tars; information which hitherto have been scarce in public domain. © 2009 Elsevier B.V. All rights reserved. 1. Introduction 1.1. Acid tars Acid tars are wastes generated during the processing of coal, petroleum, and petrochemicals, which are considered hazardous in most jurisdictions (e.g. [1]). Kolmakov et al. [2] described acid tars as a non-utilizable solid waste with resinous and viscous char- acteristics and varying flowability. Three processes lead to the generation of acid tars: (i) oil re-refining—the removal of metal impurities from spent lubrication oils using concentrated sulfuric acid; (ii) benzole refining—production of purified fractions of ben- zene, toluene and xylene (BTX) from crude benzole, a by-product of coal carbonization; and (iii) petroleum fractions refining—the use of concentrated sulfuric acid to remove unsaturated hydrocarbons and sulfur compounds from heavy lubricant fractions to produce white oil used for medicinal, cosmetic and specialized lubrication purposes [3–5]. The initial materials and treatment processes lead- ing to the generation of acid tars are not exactly alike; hence the nature and composition of acid tars differ from process to pro- cess. However, the common denominator among these processes ∗ Corresponding author. Tel.: +44 207 735 7667; fax: +44 207 380 0986. E-mail address: sunday.leonard@ucl.ac.uk (S.A. Leonard). is the use of concentrated sulfuric acid in the cleansing of organic substances [3,6]. Historically, acid tars have been disposed with or without prior treatment in worked out quarries, clay or gravel pits, or landfills, normally referred to as acid tar lagoons [3,7–9]. There are many such disposal sites in the UK and others have been reported in the United States, Canada, Australia, and other European countries including The Netherlands and Russia [10]. This dumping is not environmentally sustainable because of the potential risk posed by the components of acid tars to human and ecological receptors. Although the quantity of acid tars generated has been greatly reduced due to the development of efficient catalytic processes by the petroleum industry [2,3,11], an effective treatment method is needed for existing acid tar lagoons and for the quantities that are still being generated. Kolmakov et al. [12] reviewed var- ious methods for the processing of acid tars into other products but concluded that none of the approaches are satisfactory; thus the fundamental need for an effective remediation method still remains. Attempted remediation technologies include monitored natural attenuation and excavation and disposal into landfills [13], cement-based stabilization/solidification (S/S) [14], containment using construction materials such as clay/cement/plastic mem- brane materials [15], incineration in a cement plant/utilization as a fuel substitute [3,12,13], and fluidized bed incineration [16]. How- ever, these technologies have not been well researched and their feasibility and effectiveness remains questionable due to poor tech- 0304-3894/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2009.10.015