Abstract
The demand for lithium, tantalum, and niobium has soared in the past two decades, leading to their classification as ‘critical metals’ in many jurisdictions. Lithium-Cesium-Tantalum (LCT) pegmatite deposits are an important source of these metals. Among the main challenges in the beneficiation of pegmatite deposits are hard rock properties and a finer liberation, which require fine grinding, increasing comminution costs. It is thus necessary to develop an energy-efficient separation process to recover Li-, Ta-, and Nb-bearing minerals from these deposits. This project aims to apply the SelFrag (Selective Fragmentation) technology to improve the processing of an LCT pegmatite. The ore was prepared using two methods: (1) direct mechanical fragmentation (jaw crusher, roll crusher, rod mill); and (2) pre-weakening by high voltage pulses (SelFrag), followed by mechanical fragmentation. For the conventionally ground ore, 15 % of the Li, Ta, and Nb reported to the -20 µm fraction, after SelFrag this was reduced to only 5 %. Heavy liquid separation revealed that gravity concentration was promising as a means of pre-concentration only, and further processing was required to produce a salable concentrate. In the case of the SelFrag pretreated ore, shaking table tests resulted in Ta/Nb recovery of ~50 % and Li2O recovery of 33 %, compared with only 30 % Ta/Nb recovery and 12 % Li2O recovery when using directly ground ore, respectively. Thus, a pretreatment by SelFrag reduced grinding energy, decreased the generation of fine particles during grinding, and improved mineral liberation, thereby increasing the separation performance.