Enhanced rare earth alkali cake washing and alkaline wastewater disposal via mineral phase transformation and ultrasound.

[Display omitted] • Proposed mineral phase reconstruction for enhanced rare earth alkali cake washing. • Introduced ultrasonic cleaning to reduce alkaline wastewater in rare earth process. • Used CaF 2 , Ca 3 (PO 4) 2 , CaCO 3 for glass prep, realizing wastewater high-value use. • NaOH from causticization returned for resource recycling. The liquid alkali decomposition method represents a relatively clean smelting process for the treatment of the mixed rare earth concentrate derived from Bayan Obo. However, the production process generates a considerable quantity of alkaline wastewater, which presents a significant obstacle to the large-scale application of this process. Accordingly, the reduction and high-value treatment of rare earth alkaline wastewater represents a pressing need and challenge. This paper presents a novel approach to the treatment of rare earth alkaline wastewater, which has the potential to revolutionize the way such wastewater is handled. The proposed method involves a series of processes, including mineral phase transformation, ultrasonic enhanced water washing, causticization treatment, and glass preparation. These processes not only reduced the volume of alkaline wastewater by over 50% compared to traditional treatment methods, but challenged the conventional wisdom surrounding the treatment of alkaline wastewater, resulted in the conversion of NaF, Na 3 PO 4 , and Na 2 CO 3 into a mixed calcium salt, which contains CaF 2 , Ca 3 (PO 4) 2 , and CaCO 3. And the mixed calcium salt can then employed in the preparation of high-performance glass. This process not only circumvents the deficiencies associated with the low purity and value of the final product when NaF, Na 3 PO 4 , and Na 2 CO 3 are separated individually, but it also allows for the reuse of the generated NaOH, thereby achieving high-value utilization of the alkaline wastewater. This paper offers valuable insights into the treatment of alkaline wastewater from various rare earth minerals treated by the liquid alkali decomposition method. [ABSTRACT FROM AUTHOR]