Collaborative processing of steelmaking slag and red mud for efficient phosphorus recovery and resource utilization

Area of Science:

• Metallurgical Engineering
• Materials Science
• Environmental Science

Background:

• Steelmaking slag (SS) presents a challenge for phosphorus (P) recovery due to its complex mineralogy.
• Efficient P extraction from SS is vital for resource sustainability and waste reduction in metallurgy.

Purpose of the Study:

• To investigate the use of red mud (RM) as a modifier to reconstruct SS mineral phases and improve P availability.
• To evaluate the P recovery efficiency from modified SS.

Main Methods:

• SS was melted with varying amounts of RM to alter mineral composition.
• Modified slags underwent acidic leaching (pH 3.0-5.0) to assess element dissolution.
• Leachate pH was adjusted to precipitate P.

Main Results:

• Increased RM addition led to P2O5 enrichment in dicalcium silicate, forming Na2Ca2P2O8.
• Selective P leaching was achieved at pH 4.0 (75% extraction), with low Fe and Al solubility.
• P precipitation at pH 8.0 yielded 99% recovery, resulting in 74% overall P recovery as hydroxyapatite.

Conclusions:

• Modifying SS with RM is an effective strategy for enhancing P recovery.
• This approach offers a sustainable pathway for the high-value utilization of steelmaking slag.