Dewatering of Chromite Ore Plant Tailings Using Carboxymethyl Cellulose and Chitosan as Flocculants

Abstract

Fine particle size mine tailings are turned into large particles by flocculation as a method of separating solids from liquids. Without solid-liquid separation, water required for plant operations cannot be recovered, which would necessitate the construction of a larger tailings dam. In this study, flocculation experiments were performed using carboxymethyl cellulose (CMC) and chitosan to find the optimum sedimentation conditions of tailings. Therefore, flocculation was optimized by applying response surface methodology (RSM). A 34 full factorial central composite design (CCD) was selected to describe the effect and interaction of four variables: flocculant dosage, stirring speed, pulp density, and pH. The performance of the flocculants was evaluated by measuring the turbidity of the suspension, water recovery, and sludge compactness. The optimum turbidity values obtained with CMC and chitosan were 6.80 nephelometric turbidity units (NTU) and 8.20 NTU, respectively. CMC and chitosan both contributed significantly to the flocculation of tailing, and flocculation was highly dependent on the pH and pulp density. The positively charged particles in the sample flocculated because of electrostatic interactions when CMC was added, whereas flocculation occurred via a bridging mechanism with chitosan. The important results highlighted that both CMC and chitosan rapidly flocculated the tailings and significantly reduced the turbidity.