Flocculation Behavior of Ultrafine Silica Particles in Acid Leaching Pulp by Nonionic Polymeric Flocculants

Sedimentation of ultrafine silica particles that exist in acid leaching pulp and their separation from Pregnant Leach Solution largely determines the efficiency of a hydrometallurgical process utilizing copper oxide ore. Thickener on a larger scale can allow longer sedimentation, generating low overflow turbidity but high economic input. In this paper, the flocculation behavior of quartz particles in sulfuric acid solution using nonionic flocculants polyethylene oxide (PEO) and polyacrylamide (PAM), as well as ionic cofactor montmorillonite (MMT) and nonionic cofactor tannic acid (TA), were investigated, with the dynamic size of flocs and counts of fines being monitored using an in situ particle size measurement technique, namely the focused beam reflectance measurement (FBRM), under turbulent conditions. Attention was paid to variables affecting quartz flocculation properties from both physicochemical and hydrodynamic aspects such as shear intensity. The flocculation mechanism was investigated using zeta potential and dynamic light scattering measurements. It was found that the TA promotes the bridging flocculation of PEO-quartz by forming associative complexes with larger clusters in solution, while MMT electrostatically adsorbs on the quartz surface, enhancing its bridging with PAM. Low turbidity benefited from the higher shear resistance of the compact flocs structure provided by PEO/PEO + TA/PAM + MMT. Efficient solid-liquid separation was achieved by using the synergistic flocculation of small molecule cofactors and polymer flocculants.