Effects of orbital shaking on settling velocity of mineral particles in aqueous solutions using split‐plot designs

Abstract

AbstractThis study aimed to experimentally investigate and statistically test changes in the settling velocity of particles falling in an aqueous solution due to an orbital shaking of the container. A series of settling experiments were conducted on coal samples under different combinations of shaking speed and initial concentration of the particles. First, a generalized version of the factorial design (a split‐plot design) was utilized to obtain the acquired data. Then, an appropriate statistical model was fitted to experimental data using settling velocity as a response while shaking speed and initial coal concentration were defined as factors. Graphic patterns confirmed our hypotheses that settling velocity is affected by the shaking speed, initial coal concentration and the interaction of these two factors. Results of the analysis indicated that the main effects of both initial coal concentration (F‐statistic = 775.75) and shaking speed (F‐statistic = 11.96) on the settling velocity are strongly significant (both with a P‐value near zero). Moreover, a strong interaction of the effects of these factors on the response variable was also observed (F‐statistic is 10.57 with a P‐value of near zero). Based on the results, combination of 4% coal concentration and 50 rpm shaking speed resulted in the highest settling velocity of 1.21 cm/s. In contract, a combination of 10% coal concentration and 100 rpm shaking speed led to a settling velocity of only 0.55 cm/s. Findings of this study may have invaluable benefits to the mineral and water treatment industries where design and construction of thickeners and sedimentation tanks equipped with orbital shakers can significantly accelerate the sedimentation of mineral particles as well as water contaminants.