Chemical partitioning in lightweight aggregates manufactured from washing aggregate sludge, fly ash and used motor oil B. González-Corrochano a , J. Alonso-Azcárate a, * , M. Rodas b a Department of Physical Chemistry, Faculty of Environmental Sciences, University of Castilla-La Mancha, Avenida Carlos III, s/n, 45071 Toledo, Spain b Department of Crystallography and Mineralogy, Faculty of Geological Sciences, Complutense University of Madrid, Ciudad Universitaria, 28040 Madrid, Spain article info Article history: Received 19 May 2011 Received in revised form 17 April 2012 Accepted 9 May 2012 Available online xxx Keywords: Washing aggregate sludge Fly ash Used motor oil Lightweight aggregate BCR sequential extraction procedure Heavy metal abstract The optimized BCR sequential extraction procedure was applied to washing aggregate sludge and fly ash, the raw materials used to produce artificial lightweight aggregates (LWAs) in a previous study. The mixtures of the raw materials and the two types of LWAs obtained have also undergone this procedure. As a result, it has been possible to evaluate the effects of the heating process on the extraction behaviour of twenty-eight elements. The thermal process reduces the availability of all the studied heavy metals, with the exception of Mo. The availability of the other elements is also reduced, with the exceptions of As and Sb, which increase in the non-residual fractions. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Metal ions, when present in excess or under the wrong condi- tions, can produce multiple toxic effects. Human intervention can alter the concentrations of metals in soils, ground and surface water, air and living organisms and facilitate their distribution from the mineral reserves in which they are naturally confined (Moreno Grau, 2003). In order to understand the environmental chemistry of an element, it is necessary to determine its physicochemical form. Sequential extraction procedures (SEPs) are widely applied to assess the partitioning and mobility of elements in sediments, soils and waste materials (Guevara-Riba et al., 2004). Among all the SEPs, the BCR method is the most widely used (Cuong and Obbard, 2006; Kartal et al., 2006; Zemberyova et al., 2006). This is an operationally defined sequential extraction procedure proposed by the European Community Bureau of References (BCR), now the Standards, Measurements and Testing Programme. This method appears to be more effective than others proposed previously (Fernández et al., 2004), such as that of Tessier (Tessier et al., 1979) and is the only one which allows validation based on two certified reference mate- rials (Davidson et al., 2006; Gómez-Ariza et al., 2000; Rauret, 1998). Nevertheless, the dissolution or selective destruction of the components seems to be implicit in any sequential extraction tech- nique, as does the non-specificity of the reagent or the possibility of the redistribution of metals during the extraction (Fernández et al., 2004) but this is the best approximation to correlate the concentration of elements with the different geochemical fractions. Previous studies (Hjelmar, 1996) have proven that high temper- ature treatment can stabilize most toxic substances of manufactured materials, which can be safely recycled as construction materials (such as lightweight aggregates, LWAs). However, other studies show that there are few differences in metal leaching between raw materials and sintered products (Cheeseman et al., 2005). This paper is a continuation of a previous work (González- Corrochano et al., 2009) in which artificial LWAs were manufac- tured using washing aggregate sludge (WS), fly ash (FA) and used motor oil (UMO) and mixing, milling, pelletizing and sintering them in a rotary kiln. Their possible applications include geotechnical uses, insulation, horticultural uses, and/or use in prefabricated lightweight structures and insulating lightweight concretes. The objectives of this research are: i) to determine the parti- tioning of different elements in the waste materials used to manufacture LWAs; ii) to evaluate the effect of the heating process on the extraction of the elements; and iii) to determine the concentration of different elements in the eluates obtained by a single leaching procedure. * Corresponding author. Tel.: þ34 625168760; fax: þ34 925268840. E-mail address: jacinto.alonso@uclm.es (J. Alonso-Azcárate). Contents lists available at SciVerse ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman 0301-4797/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvman.2012.05.007 Journal of Environmental Management 109 (2012) 43e53