IC Determination of CaSO₃·1/2H₂O in Flue Gas Desulfurization Gypsum

IC was applied to the determination of SO32-in flue gas desulfurization gypsum, and content of CaSO3·1/2H2O (in w%) was caculated from the amount of SO32-found. CaSO3·1/2H2O was converted to sulfur dioxide in the presence of HCl and SnCl2, and the sulfur dioxide produced was absorbed into solution. The solution was filtered with 0.22 μm filtering membrane. 25 μL of the filtrate were separated on AS9-HC separation column and AG9-HC protective column using buffer solution of 8 mmol·L-1 Na2CO3-2 mmol·L-1 NaHCO3 solution as mobile phase. Conductivity detection was adopted in the determination. Linear relationship between values of peak area and mass concentration of SO32-was kept in the range of 1.00-100 mg·L-1 with detection limit (3S/N) of 0.05 mg·L-1. On the base of sample of flue gas desulfurization gypsum, test for recovery was made by standard addition method; values of recovery found were 97.4% and 101%, and RSD′s (n=6) were in the range of 0.35%-1.4%.