Effects of leachant temperature and pH on leachability of metals from fly ash. A case study: Can thermal power plant, province of Canakkale, Turkey

Abstract

Lignite powered electric generation plants result in increasing environmental problems associated with gaseous emissions and the disposal of ash residues. Especially, low quality coals with high ash content cause enormous quantities of both gaseous and solid fly ash emissions. The main problem is related to the disposal of fly ash, which, in many cases, contains heavy metals. It is known that toxic trace metals may leach when fly ash is in contact with water. In this study, fly ash samples obtained from the thermal power plant in the town of Can in Turkey were investigated for leachability of metals under different acidic and temperature conditions. The experimental results show that a decrease in pH of the leachant favors the extraction of metal ions from fly ash. A significant increase in the extraction of arsenic, cadmium, chromium, zinc, lead, mercury, and selenium ions from the ash is attributed to the instability of the mineral phases. These heavy metals concentrations increase with respect to increasing acidic conditions and temperature. Peak concentrations, in general, were found at around 30 degrees C.

Leaching characteristics of fly ash from fluidized bed combustion thermal power plant: Case study: Çan (Çanakkale-Turkey)

“…In addition, the concentration of some heavy metals has also changed in the fly ash samples. For example, concentration of arsenic in the fly ash was about 70 ppm in 2006 [1] (Fig. 4).…”

“…2). Based on the results of these analyses, the fly ashes were classified as type F, which have low calcareous and pozzolanic (bonding) characteristics [1]. After flue gas desulphurization unit was taken online and limestone was started to be added, the composition of ash was completely changed.…”

“…As lignite burns, toxic pollutants such as arsenic (As), lead (Pb), zinc (Zn), selenium (Se), cadmium (Cd), cobalt (Co), nickel (Ni), copper (Cu) and chromium (Cr) are transferred into the wastes. Of these wastes, especially the fly ashes, cling to the surface of the elements [1][2][3]. These toxic pollutants can leach out and contaminate soils, as well as surface water and groundwater [2,[4][5][6][7][8][9][10][11][12].…”

Combustion and Leaching Behavior of Trace Elements in Lignite and Combustion by-Products From the Muğla Basin, Sw Turkey

“…There are two major types of leaching tests concerning their set up: Column tests, which better simulate field conditions, and batch tests, which provide evidence for the maximum potential mobility of an element. Batch tests are more widely applied due to their relatively rapid and reliable results but can easily misinterpreted if only absolute values are to be considered (Siavalas et al, 2007;Baba et al, 2008;Hesbach et al, 2009). The lignite mining activities in Turkey appear to have serious repercussions in underground waters.…”

Geochemical investigations of metals release from submerged coal fly ash using extended elutriate tests

“…Furthermore, the pH dependent leaching of metal ions (e.g., arsenic, cadmium, chromium, zinc, lead, mercury, selenium) (Baba et al, 2008) raises concern regarding potential for toxic effects if contacted by aquatic receptors (Roy et al, 1981;Carlson and Adriano, 1993;Rowe et al, 2002;Kuzmick et al, 2007). The physical effect of siltation, followed by reductions in pH (and associated metal increased leaching) have been reported to retard the recovery of indigenous benthic macroinvertebrates in basins silted by fly ash due to chronic impairment (Cherry et al, 1979(Cherry et al, , 1984, and although the Kingston event was a single large release, residual fly ash will remain in the river system for an extended period of time.…”