Stabilization of arsenic-bearing solid residuals in polymeric matrices

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Arsenic contamination in drinking water poses a significant global health risk.
• Effective removal of arsenic from water requires stable and efficient sorbent materials.
• Encapsulation technologies are crucial for immobilizing hazardous waste, including arsenic-laden sorbents.

Purpose of the Study:

• To investigate the efficacy of polymeric matrices for encapsulating solid sorbents used in arsenic removal from drinking water.
• To develop and evaluate a novel aqueous-based manufacturing process for creating these polymeric waste forms.
• To compare the arsenic leaching performance of polymer-encapsulated sorbents against unencapsulated sorbents and conventional cement matrices.

Main Methods:

• Granular ferric oxy/hydroxide and ferric hydroxide amended alumina residuals were encapsulated in a polymer blend (poly(styrene butadiene) and epoxy resin).
• A novel aqueous-based manufacturing process was employed for encapsulation.
• Arsenic leaching was assessed using the Toxicity Characteristic Leaching Procedure (TCLP) and the California Waste Extraction Test (CA-WET).

Main Results:

• Polymeric waste forms successfully contained over 60 wt% sorbent while maintaining good mechanical properties.
• Polymer-encapsulated residuals demonstrated significant leaching resistance, with arsenic concentrations below the toxicity characteristic standard (5 mg/L) even under aggressive testing (CA-WET).
• When preprocessed and encapsulated to avoid size reduction, arsenic leaching was reduced up to 700 times compared to unencapsulated residuals, and was an order of magnitude lower than cement matrices.

Conclusions:

• Polymeric matrices offer a superior alternative to cement for encapsulating arsenic sorbents, enabling higher sorbent loading and substantially lower arsenic leaching.
• The developed aqueous-based process is effective in creating robust waste forms with excellent arsenic immobilization capabilities.
• This technology holds promise for safer and more effective management of arsenic-contaminated water treatment residuals.