Enhancing flotation separation of fine copper oxide from silica by microbubble assisted hydrophobic aggregation

Abstract

One of the main challenges facing the flotation of base metal oxide minerals is their fine sizes of particles as a result of fine grinding to achieve a desired degree of liberation for low-grade and finely disseminated complex ores. This study aims at studying hydrophobic aggregation and in situ gas nucleation of fine copper oxides with sodium dodecyl sulfate (SDS) as a selective collector to enhance CuO recovery. Experimental results by in situ and real time particle size measurement using focused beam reflectance measurement (FBRM) coupled with particle vision measurement (PVM) showed an enhanced aggregation of fine CuO by SDS adsorption. Particle aggregation assisted by gas nuclei which were generated in situ on CuO by high intensity agitation (HIA) was visualized by total internal reflection fluorescence microscopy (TIRFM). It is the enhanced aggregation with nanobubbles as bridges that improved its recovery from fine silica. Coupled with the calculation using the extended DLVO theory, contact angle and zeta potential of fine particles were measured to understand the critical role of hydrophobic forces in aggregation of fine CuO particles. The copper ions dissolved from the fine copper oxide were found to inadvertently activate fine silica flotation which could be effectively depressed by ethylene diamine tetraacetic acid (EDTA). A combination of SDS with EDTA was proposed and demonstrated to achieve selective recovery of fine copper oxide from fine silica gangue. The results from this study provide directions for enhancing copper recovery from low grade and finely disseminated copper oxidize ores, in particular from tenorite ores.