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.

Cyanide and copper often co-exist in process water with complicated speciation. The deposition of copper on pyrite from cyanide bearing solutions is unknown and is the objective of this study. The electrochemical behaviour of pyrite in a solution with CN/Cu mole ratio of 3/1 has been investigated in different solution pH values. It was found that, at pH 7, cuprous cyanide can be oxidized to Cu(II) oxide/hydroxide which deposit on the pyrite surface and transform to Cu(I)-sulfide during the subsequent cathodic sweeping. However, this anodic deposition process is inhibited either at pH 10 due to the dissolution of solid Cu(II)/Cu(I)-species by Cu(CN)₃ ²⁻, or at pH 5 due to the high solubility of Cu(II) oxide/hydroxide. On the other hand, Cu(CN)₂ ⁻ can be deposited onto pyrite, forming a Cu(I)-sulfide layer at more reducing potentials. The understanding of the electrodeposition mechanisms provides opportunities for the recovery of copper from cyanide-bearing waste water, as well as the separation of pyrite from other raw materials by altering its surface properties.