Electrolytic manganese residue disposal based on basic burning raw material: Heavy metals...

Area of Science:

• Environmental Science and Engineering
• Geochemistry
• Materials Science

Background:

• Electrolytic manganese residue (EMR) poses environmental challenges due to heavy metal content.
• Solidification/stabilization (S/S) is a potential treatment for EMR, but mechanisms and long-term stability require clarification.
• Basic burning raw material (BRM) has shown promise for EMR treatment.

Purpose of the Study:

• To elucidate the solidification/stabilization (S/S) mechanisms of Mn²⁺ and NH₄⁺ in EMR using BRM.
• To evaluate the long-term stability and leaching behavior of heavy metals in S/S EMR.
• To characterize the hydrated BRM and S/S EMR to understand the stabilization processes.

Main Methods:

• Treatment of EMR with BRM for solidification/stabilization.
• Characterization of hydrated BRM and S/S EMR using various analytical techniques.
• Long-term leaching tests to assess Mn²⁺ migration, release, and diffusion.
• Analysis of phase and morphology changes during long-term leaching.

Main Results:

• S/S EMR met Chinese standard GB 8978-1996 for Mn²⁺ (0.02 mg/L) and NH₄⁺ (0.68 mg/L) leaching, with a pH of 8.75.
• Long-term stability was significantly enhanced, with reduced Mn²⁺ leaching concentration (0.05 mg/L), migration, and diffusion.
• Mechanism studies revealed Mn²⁺ stabilization in minerals like tephroite and johannsenite, and encapsulation of other heavy metals by C-S-H gels and ettringite.

Conclusions:

• BRM effectively solidifies and stabilizes EMR, significantly improving its long-term storage viability.
• The hydration of BRM generates phases (C-S-H, ettringite) crucial for immobilizing heavy metals.
• This S/S method provides a promising solution for the environmentally sound management of EMR.