The　issue　that　eliminating　the　negative　effects　of　inevitable　ions　in　the　pulp　on　mineral　flotation　separation　has　attracted　widespread　attention.　To　achieve　the　efficient　flotation　separation　of　limonite　from　quartz,　citric　acid　was　utilized　as　a　depressant　for　quartz　in　this　paper.　The　solubility　of　limonite　was　studied　using　inductively　coupled　plasma　tests　(ICP),　and　the　effect　of　Fe3+　and　citric　acid　on　the　separation　of　limonite　from　quartz　under　sodium　oleate　(NaOL)　system　was　investigated　using　batch　flotation　tests.　The　underlying　mechanisms　were　probed　through　zeta　potential　measurements,　infrared　spectroscopy　(IR),　X-ray　photoelectron　spectroscopy　(XPS),　and　contact　angle　detection.　It　was　found　that　limonite　could　dissolve　a　certain　number　of　Fe3+　in　the　pulp.　These　Fe3+　adsorbed　onto　quartz　and　acted　as　the　active　sites　to　promote　the　adsorption　of　NaOL,　thereby　enhancing　quartz　flotation　evidently　and　deteriorating　the　separation　of　limonite　from　quartz.　Fortunately,　citric　acid　could　depress　the　flotation　of　iron-activated　quartz　quite　well　by　covering　and　desorbing　the　active　sites　of　Fe3+　and　causing　the　steric　hindrance　to　prohibit　the　adsorption　of　NaOL.　Meanwhile,　the　hydrophilic　groups　in　citric　acid　could　also　increase　the　surface　hydrophilicity　of　quartz　and　enhance　the　inhibitory　effect.　In　comparison,　Fe3+　and　citric　acid　had　little　effect　on　the　adsorption　of　NaOL　onto　limonite　since　its　surface　exposed　enough　Fe-active　sites　for　the　adsorption　of　NaOL.　Thus,　the　difference　in　the　floatability　of　limonite　and　quartz　was　enlarged,　eventually　achieving　a　better　separation　of　them.　This　research　sheds　new　light　on　the　role　of　citric　acid　in　the　selective　separation　of　quartz　from　soluble　iron　minerals.　©　2024　Elsevier　B.V.