Desulfurization: Critical step towards enhanced selenium removal from industrial effluents

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies
• Anion Exchange Resins

Background:

• Coal-fired power plants generate Flue Gas Desulfurization (FGD) wastewater containing selenium and other contaminants.
• Selenium removal from industrial wastewater is critical due to its toxicity.
• Existing treatment methods face challenges with complex wastewater matrices.

Purpose of the Study:

• To evaluate the efficacy of a commercial iron oxide-impregnated anion exchange resin (Purolite® FerrIX A33E) for selenium removal from synthetic and real FGD wastewater.
• To investigate the impact of competing anions, particularly sulfate, on selenium removal.
• To assess the resin's performance in removing co-occurring toxic trace metals.

Main Methods:

• Adsorption studies using synthetic solutions and actual FGD wastewater.
• Characterization of FGD wastewater composition (Se, SO42-, Cl-, Ca2+, trace metals).
• Ion exchange treatment with Purolite® FerrIX A33E, with and without prior sulfate removal (desulfurization).

Main Results:

• The resin showed high affinity for selenate and selenite in synthetic solutions, but sulfate competed strongly.
• In raw FGD wastewater, selenium removal was poor (3%) due to high sulfate and chloride concentrations.
• Desulfurization of FGD wastewater prior to ion exchange significantly increased selenium removal to 80% and effectively removed toxic metals (Cd, Cr, Zn).

Conclusions:

• Sulfate is a major competing anion for selenium removal using the tested anion exchange resin.
• Pre-treatment for sulfate removal is essential for efficient selenium remediation from FGD wastewater.
• The combined desulfurization and ion exchange process shows promise for treating complex industrial effluents, removing selenium and toxic metals.