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.　©　2023　by　the　authors.