Agriculture Reference
In-Depth Information
remote sensing application to analyze red mud soil contamination near urban areas.
Significant research activities are being carried out and the aim of this chapter is to show the
latest studies underlining the importance of multi-technique application in laboratory and
plant scale studies.
2. Fly ash and red mud characterization
2.1 Fly ash
Fly ash is the main combustion by-product from coal-fired power plants and it is partly
used in cement manufacturing due to its well-known pozzalonic reactivity (Larosa, 1992).
Unfortunately, more than half of fly ash is disposed of in landfills because it finds no other
application. The huge production of fly ash is extremely worrying because of this kind of
disposal and several investigations have been carried out in order to try to exploit this waste
material.
Over the last few years fly ash has been gaining ground in finding solutions to
environmental problems and in particular it has being used to the synthesis of zeolites,
hydrated aluminosilicate minerals with a three-dimensional open structure making them
very useful for solving the mobility of toxic elements in a number of environmental
applications. This is due to the mineralogical composition of this waste material.
Fly ash is characterized by quartz, mullite, subordinately hematite and magnetite,
carbon, and a prevalent phase of amorphous aluminosilicate (Bayat, 1998; Hall
&Livingston, 2002; Hower et al., 1999; Koukouzas et al., 2006; Kukier et al., 2003; Mishra
et al., 2003; Sokol et al., 2000). The abundance of amorphous aluminosilicate glass,
which is the prevalent reactive phase, is what makes fly ash an important source
material in zeolite synthesis.
Fly ash cannot be properly used, both in cement manufacturing and in environmental
application, without an in-depth knowledge of its mineralogical and chemical
characteristics. So far there have been lots of publications dealing with the morphological
characterization of this material using scanning electron microscopy technique equipped
with backscattered and secondary electron detectors and coupled with energy dispersive X-
ray spectrometer (SEM-EDS) (Katrinak & Zygarlicke 1995; Kutchko & Kim, 2006; Sokol et
al., 2000; Vassilev et al., 2004). Many studies have been carried out by using the thermal
analysis (TG/DTA) (Hill et al., 1998; Li et al., 1997; Majchrzak-Kuceba & Nowak, 2004; Paya
et al. 1998; Sarbak & Kramer-Wachowiak, 2001; Szécsényi et al. 1995; Vempati et al. 1994)
and the X-ray powder diffraction (XRD) (McCarthy & Solem,1991; van Roode et al., 1987;
Ward & French, 2006) in order to gather compositional information, too. Many works report
the use of XRD and Fast Fourier spectroscopy (FTIR) (Vempati et al.1994) in order to
identify and quantify glassy materials contained in fly ashes.
Fly ash application is also closely related to its chemical composition. In fact, a large amount
of potentially hazardous leachable elements (Brindle & McCarthy; 2006; Jegadeesan et al.,
2008; Nakurawa et al., 2007) restricts the application of this material.
2.1.1 Characterization of italian fly ash samples: a case study
The authors characterized four Italian fly ash samples through a multi-method approach. In
order to determine the possible utilization of these materials for concrete and cement
manufacturing or for environmental application, also synthesizing zeolite and several
morphological, chemical and compositional parameters were thoroughly investigated and
compared.
