Selenate removal from sulfate containing aqueous solutions.

Area of Science:

• Environmental Science
• Water Treatment Technologies
• Inorganic Chemistry

Background:

• Selenium contamination in agricultural drainage water poses environmental risks.
• High sulfate concentrations significantly hinder conventional selenium remediation agents like gamma alumina and zerovalent metals.
• Effective sulfate removal is crucial for successful selenium remediation.

Purpose of the Study:

• To investigate a two-stage water treatment process for enhanced selenium removal.
• To evaluate the efficacy of barium chloride in sulfate precipitation and simultaneous selenate immobilization.
• To assess the performance of subsequent selenium remediation agents after sulfate pre-treatment.

Main Methods:

• A two-stage treatment process was developed, starting with barium chloride (BaCl2) precipitation.
• Barium chloride was used to remove sulfates and immobilize selenate from contaminated water.
• Subsequent treatment stages employed remediation agents such as bimetallic NiFe particles, gamma alumina, and activated carbon.

Main Results:

• Barium chloride effectively precipitated sulfates and immobilized significant amounts of selenate.
• 100% selenate removal was achieved using 15 g/L BaCl2 alone in a solution with 1 mg/L selenate and 4 g/L sulfate.
• A sequential treatment of 10 g/L BaCl2 followed by NiFe powder resulted in 100% selenium removal from a similar solution.

Conclusions:

• The proposed two-stage process significantly enhances selenium removal efficiency from sulfate-rich waters.
• Barium chloride pre-treatment is a viable method for sulfate reduction and selenate co-precipitation.
• Combining barium chloride precipitation with established selenium remediation agents offers a robust solution for contaminated water treatment.