A clean process for phosphorus recovery and gallium enrichment from phosphorus flue dust by sodium carbonate roasting

Phosphorus flue dust (PFD) is a solid waste product from phosphorus (P) production that contains P and is enriched with gallium (Ga). The recovery of these valuable components not only protects the environment, but also reduces resource waste. This study aimed to develop a green and efficient method to recover P and enriched Ga from PFD. The effects of different parameters on the P leaching rate and Ga loss rate during Na₂CO₃ roasting and water leaching were investigated and optimized. The reaction mechanisms during the experiment were characterized, revealing that the P-containing compounds in PFD mainly transformed into water-soluble Na₃PO₄. Furthermore, the leaching rate of P reached 85.38%, while Ga was mainly concentrated in the residue and its loss rate was only about 1%. Ga content in the residue reached about 0.1%. An attempt was made to recover Na⁺ and PO₄^3- from the aqueous solution by evaporative crystallization and XRD analysis showed that the main phase of the crystallization product was Na₂HPO₄. The proposed process is technically simple, only Na₂CO₃ is added and no hazardous substances are generated, and represents a new method for recovering P and enriching Ga from PFD.