Extraction of beryllium from Indian beryl by ammonium hydrofluoride

A new technique of decomposing beryl ore at low temperature with ammonium hydrofluoride (NH4HF2) is proposed. Removing the fluorides of silicon and aluminium from the reaction product as volatile and insoluble compounds, respectively, have been investigated experimentally and the feasibility of the process has been established to extract beryllium fluoride (BeF2) as a soluble compound. The sequence of reaction of beryl ore with the strong fluorinating agent NH4HF2 has been studied by TG/DSC, intermediates and final products were identified by XRD. The product yield was found to be up to 93%. A process flow sheet to produce beryllia (BeO) and BeF2 for subsequent magnesiothermic reduction to produce beryllium metal is proposed based on the experiments conducted at bench scale. Methods of recycling NH4HF2 have been suggested, thereby making the proposed route superior to the conventional methods in terms of recovery, low temperature of operation, fluoride recycling, and significant reduction in effluent as well as improved safety in handling of beryllium.

Research highlights
► Intermediate products of the reaction between beryl and NH4HF2 were identified.
► Sequences of transformations of intermediates into final products were discussed.
► Optimum range of temperature was established for extracting Be from beryl.
► Process flow sheet for extracting Be from beryl using NH4HF2 was proposed.
► Up to 1000 g of beryl ore was processed and Be recovery was found close to 90%.