Conditions and mechanism for extracting potassium from muscovite in potassium-bearing shale by the barium ion-exchange method

• A new feasible method named barium ion-exchange was proposed to exchange potassium ion directly in muscovite.
• The initial barium concentration is more sensitive than reaction time to potassium extraction rate.
• The higher initial barium concentration used, the greater K+ extraction rate acquired.
• ‘Vacancy effect’ and ‘radius effect’ interpreted the mechanism of barium exchanging potassium.

By a cation-exchange method, potassium was extracted from muscovite using hydrochloric acid as a motivator and barium ion as a potassium-exchange agent. The influences of various extracting conditions, such as initial barium concentration, reaction temperature, and reaction time, on cationic exchange were investigated at a constant pH value. Mineral phases of the treated samples were also investigated by X-ray diffraction and a significant inflective change of the interlayer spacing was detected. In addition, the significant inflective changes of stretching bonds of hydroxyl and silicon–oxygen were also discovered by Fourier transform infrared spectroscopy analysis. ‘Vacancy effect’ and ‘Radius effect’ were proposed as two representative extraction mechanisms to interpret the synchronous inflective changes of the interlayer spacing and the stretching bonds of hydroxyl and silicon–oxygen.