Comparison of AAS, EDXRF, ICP-MS and INAA performance for determination of selected heavy metals in HFO ashes

Abstract

A large amount of oil ash is generated in Egypt and Saudi Arabia each year as industrial waste. Most of these ashes are landfill and often lead to a dispersion of heavy metals in the surrounding groundwater and soil. In many countries, such as Egypt, little attention has been paid to the environmental effect of fly ash. In this study, the concentration of vanadium, nickel, iron, lead and zinc in oil fly and boiler ashes collected from six thermal power plants has been assessed with inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry, instrumental neutron activation analysis and energy dispersive X-ray fluorescence (EDXRF). Samples were digested using different acid and alkali fusion methods. EDXRF and ICP-MS were confirmed to be the analytical technique of choice for the precise and accurate determination of the major metals in oil ashes. Three internal reference materials from oil ashes were prepared and used to examine the capabilities and validations of the method. Vanadium (2.8–7.7wt.%), nickel (1.9–5.9wt.%) and iron (5.3–7.3wt.%) content were found to be within the average worldwide value, while lead (0.1–0.9wt.%) and zinc (0.6–4.2wt.%) were significantly high in Egyptian oil ash. Therefore, it was the first study which confirms the presence of high levels of lead and zinc in Egyptian oil fly and boiler ash. Saudi Arabian electrostatic precipitators (ESP) fly ash had lower V, Ni and Fe content (0.3–2.5wt.%). In addition, the concentration of Zn and Pb in ESP fly ash was significantly low (0.001–0.03wt.%) compared to Egyptian oil ashes.