ROOM-TEMPERATURE DISSOLUTION OF COAL FLY-ASH FOR TRACE-METAL ANALYSIS BY ATOMIC-ABSORPTION SPECTROMETRY

A room-temperature digestion technique with hydrofluoric acid, followed by addition of boric acid, is described for coal fly ash; 19 elements (Si, Al, Fe, Ca, Mg, K, Na, Ti, Cu, Mn, Zn, Be, Ba, Co, Cd, Cr, Ni, Pb, and Sr) can then be determined by flame and flameless atomic absorption spectrometry (a.a.s.). The technique has been applied to hopper fly ash collected from an electrostatic precipitator, aerodynamically size-fractionated stack fly ashes and National Bureau of Standards fly ash (SRM 1633). Results for ten elements (Mn, Zn, Cr, Sr, Pb, Cu, Ni. K, Co and Be) by a.a.s. were within the certified range or in good agreement with the information values for the NBS fly ash. Cadmium was 7% higher than the certified value. If the major and minor elements are present as common oxides, mass recoveries for six fly ash fractions samples were quantitative, ranging from 99.1% to 101.4%. Instrumental neutron activation analysis of the undissolved residue from SRM 1633 indicates that the dissolution technique should also be useful for a.a.s. of Sn, Mo, Sb, V, and As, but not for Se, 75% of which remains in the residue. © 1979.