A closed-loop strategy for red mud acidic dealkalization: Comparison, reaction behaviors and potential applications

Area of Science:

• Environmental Chemistry
• Materials Science
• Industrial Chemistry

Background:

• Red mud, a byproduct of alumina production, poses environmental challenges due to high alkalinity.
• Sustainable disposal and utilization of red mud are critical for the alumina industry.
• Current methods for red mud treatment are often inefficient and generate secondary waste.

Purpose of the Study:

• To develop an innovative closed-loop dealkalization strategy for red mud using organic acids.
• To enhance sodium extraction efficiency from red mud.
• To repurpose the sodium-rich byproduct as a potential composite carbon source.

Main Methods:

• Red mud leaching with four standard organic acids under controlled stoichiometry.
• Liquid and solid separation, followed by CaO causticization.
• Chemical oxygen demand assessment of clarified liquors and mechanistic analysis of solids and liquors.

Main Results:

• Acetic acid achieved 75.34% dealkalization efficiency, reducing Na2O content from 8.92% to 2.20%.
• The processed solution showed a chemical oxygen demand of 6126.67 mg/L, indicating its viability as a carbon source.
• Oxalic acid led to calcium-oxalate crystallization and low chemical oxygen demand liquors; pH alone was not a reliable indicator of sodium removal.

Conclusions:

• Acetic acid is optimal for selective sodium leaching and synthesis of composite carbon sources from red mud.
• The closed-loop approach enables efficient dealkalization, alkali recovery, and generation of a usable carbon stream.
• This strategy offers a scalable solution for safer, lower-waste red mud management in the alumina industry.