Design of Experiments Approach for Efficient Heavy Metals Stabilization Using Metakaolin-Based Geopolymers

Area of Science:

• Materials Science
• Environmental Engineering
• Inorganic Chemistry

Background:

• Alkali-activated aluminosilicate matrices show potential for immobilizing hazardous metal contaminants at room temperature.
• Metakaolin-based geopolymers are a key material in this field, but their performance with specific contaminants requires further study.

Purpose of the Study:

• To immobilize chromium and nickel salts using metakaolin-based geopolymers.
• To systematically investigate the impact of synthesis parameters (Na/Al ratio, metal concentration, anion type, aging time) on metal leaching.
• To understand the geopolymerization and immobilization mechanisms.

Main Methods:

• A Design of Experiments (DOE) approach was utilized to optimize synthesis parameters.
• Fourier Transform Infrared (FTIR) spectroscopy was employed to analyze geopolymerization.
• Metal leaching tests were conducted to evaluate immobilization efficiency.

Main Results:

• All formulations achieved high immobilization rates (≥98.8%) for both chromium and nickel.
• Increased Na/Al molar ratios significantly enhanced geopolymerization and reduced metal leaching.
• Aging time influenced chromium immobilization by affecting early silicate network formation.

Conclusions:

• Metakaolin-based geopolymers are highly effective for immobilizing chromium and nickel.
• Optimizing the Na/Al ratio is crucial for enhancing geopolymerization and minimizing metal release.
• This research provides valuable insights into geopolymer-based heavy metal stabilization.