Abstract: The flotation reagents from acidic olive oil are made by transesterification of acidic olive oil. Acidic olive oil is olive oil having an acid value high enough to render it unsuitable for consumption, typically greater than 3.3% and/or between 3.3-7%. Transesterification of the olive oil with methanol converts fatty acids in the olive oil to an ester fraction and a glycerol fraction. The ester fraction may be sulfonated and used as the collector in a reverse flotation process, selectively removing the carbonate gangue from phosphate-carbonate rock in the froth, leaving phosphates in the sink. The glycerol fraction may be used without modification as the collector in the reverse flotation process. Both fractions are highly selective for carbonates, substantially reducing loss of phosphates in the froth.