Optimization of Multi-gravity Separator (MGS) Parameters for Specularite Ore Beneficiation: Evaluating Box–Behnken and Central Composite Designs

This study investigates the optimization of multigravity separator (MGS) parameters for the beneficiation of specularite ore, using both Box–Behnken design (BBD) and central composite design (CCD) as response surface methodologies. The effects of the drum speed, wash water amount, and drum slope on the grade and recovery of specularite were evaluated. Results indicated that increased wash water and drum slope generally enhanced the Fe grade, while higher drum speeds had adverse effects. Conversely, recovery was maximized with lower wash water amounts, lower drum slopes, and higher drum speeds. The comparison between BBD and CCD designs revealed that both methods provided similar optimal grade and recovery values, though with different parameter settings. CCD demonstrated superior predictive performance with higher F-values and closer agreement between adjusted and predicted R2. Multiresponse desirability optimization identified optimum conditions of approximately a 143 rpm drum speed, a 6.2 L/min wash water, and a 4.5° drum slope for CCD, achieving a composite desirability of 0.891. Confirmation tests closely matched predicted values with <1% deviation, validating model accuracy. The optimized conditions yielded a specularite concentrate assaying 63.97% Fe with 72.05% recovery. The findings demonstrate that MGS, when appropriately optimized, can effectively upgrade specularite ores to meet the quality requirements of micaceous iron oxide (MIO) pigment production. This work provides the first comparative assessment of BBD and CCD for MGS-based specularite beneficiation and establishes a validated optimization framework that integrates mineralogical, statistical, and operational insights.