Selenium speciation in flue desulfurization residues.

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Geochemistry

Background:

• Coal combustion releases volatile selenium (Se) into the atmosphere.
• Selenium capture in flue gas desulfurization (FGD) processes generates metal-laden residues.
• Understanding selenium speciation in FGD residues is crucial for assessing environmental risks.

Purpose of the Study:

• To develop a simple and selective method for determining inorganic selenium(IV) (Se(IV)), selenium(VI) (Se(VI)), and organic selenium in liquid-phase FGD residues.
• To quantify selenium species concentrations in FGD residues.
• To evaluate the environmental risks associated with FGD residue disposal.

Main Methods:

• Hydride generation atomic fluorescence spectrometry (HG-AFS) was employed for selective selenium speciation.
• Method validation involved analyzing certified reference material (NIST CRM 1632c) and spiked tap-water samples.
• Detection limits for Se(IV), Se(VI), and organic Se were determined to be 0.05, 0.06, and 0.06 microg/L, respectively.

Main Results:

• The developed method accurately determined Se(IV), Se(VI), and organic selenium in FGD residues.
• Analysis revealed high concentrations of selenium in FGD liquid residues.
• Selenium in FGD residues predominantly exists as selenite (Se(IV)), the most toxic species.

Conclusions:

• Flue gas desulfurization residues contain significant amounts of toxic selenium, primarily as Se(IV).
• The developed HG-AFS method provides accurate speciation analysis for environmental monitoring.
• FGD residues pose a substantial environmental risk due to their high selenium content and toxicity.