Efficacy of sustainable polymers to mitigate the negative effects of anisotropic clay minerals in flotation and dewatering operations

Abstract

The depletion of high-grade ore resources and ongoing demand for mineral products has led to an increase in the exploitation of low-grade and complex ores, which often contain colloid clay particles (e.g., kaolinite) that are detrimental to flotation and dewatering unit operations in mineral processing. During flotation, clay particles increase the pulp viscosity and produce a slime coating by adsorption on the surface of valuable minerals resulting in the reduction of the flotation grade and recovery. Clay particles are also suspended in mine tailings that can cause dewatering challenges in flocculation operations. The clay mitigation strategies employed during flotation (dilution and use of dispersants) and dewatering (addition of flocculants) involve reagents from non-renewable sources that can have deleterious consequences on the environment and aquatic biota. As part of an effort to find environmentally benign reagents, we evaluated the performance of six sustainable polymers (protein- and polysaccharide-based biopolymers) for their potential as dispersants and flocculants of kaolinite clay particles. Their effectiveness was assessed via chalcopyrite froth flotation, settling, and turbidity tests. Zeta potential, adsorption isotherm by total organic carbon, and X-ray scattering tests were also conducted to understand the interactions between biopolymers and kaolinite mineral surfaces. At pH 7 and 10, the anionic polysaccharide pectin showed promising dispersant efficiency in flotation and the cationic protein protamine significantly improved kaolinite flocculation in dewatering operation. Outcomes of this investigation demonstrate that commercially available sustainable polymers or “biopolymers” have a significant potential to use to mitigate the negative effects of clay particles in minerals processing to reduce environmental issues arising from inorganic and synthetic organic reagents from non-renewable sources.