The samples (approximately 0.5g accurately weighed) of
flyash were digested in a 5:1 ratio of hydrofluoric acid (HF)
and nitric acid (HNO 3 ) and evaporated to near dryness. Fur-
ther nitric acid was added and digested for 8h. The solution
was then filtered and quantitatively diluted to 50ml prior
to introduction to iductively coupled plasma coupled with
atomic emission spectrophotometer (ICP–AES) system [3].
The main species of the heavy metals are element heavy
metal, metal oxide and metal chloride.