Improving the grade of a siliceous-calcareous phosphate ore with fine size by reverse flotation method

Reverse flotation was employed to separate quartz from a phosphate ore with fine particle size which contained siliceous and carbonates gangues.The P₂O₅ grade and recovery were higher than those by direct flotation,especially the P₂O₅ recovery increased by about 40%.Compared with ether amine salts and quaternary ammonium salts,alkyl amine salts exhibited better flotation results,the P₂O₅ grade of concentrates and the quartz removal ratio were higher than 30% and 60%,respectively.Acid reagents were more propitious to improve the grade of the siliceous-calcareous phosphate ore than alkaline reagents.Because of the existence of carbonate minerals,a strong acidity condition was more beneficial to separate quartz by reverse flotation.The application of phosphoric acid as a phosphate depressant and pH modifier gave a better usability in comparison with sulfuric acid,and the dosage of phosphoric acid was less than that of sulfuric acid.The optimum collector dosage was 0.5 to 1kg·t^-1.The three cationic collectors adsorbed on ore surfaces in physical adsorption,and the adsorption of alkyl amine salts was the strongest,which is likely to explain their preferable flotation performance.