« Back

An Investigation of Flotation Reagents


(Revised Edition July 2018)

NOTE: The July 2018 Revised Edition corrected the erroneous text “150 million tons a year” on┬áPage iii to “150 million pounds a year” on this and other digital copies of this publication.



This multi-year research program investigated many aspects of phosphate flotation reagents, both in terms of improving current practice and developing new flotation processes. A dozen of petroleum additives were first screened as froth modifier/fatty acid extender. The partial substitution of rosin oil for fuel oil was found to be beneficial. Preliminary optimization tests indicated that fuel oil use could be reduced by about 25% using rosin oil, with higher cost for rosin oil being compensated by improved P2O5 recovery.

Eleven pure fatty acid compounds (C12-C22 fatty acids, 6 unsaturated and 5 saturated) were compared as Florida phosphate collectors. The saturated fatty acids were found to be very poor collectors when using the standard conditioning procedure, whereas the unsaturated C16-C22 fatty acids showed fair to good phosphate collecting ability. The C18 fatty acids oleic, impure oleic, linoleic and the C20 eicosenoic acid were shown to be the best phosphate collectors.

Five commonly used fatty acid based collectors were tested on a composite, lowgrade feed. These collectors included an oleic acid, a tall oil, a Petronate CR sulfonate, a cottonseed soapstock, and a mixture of tall oil/pitch soap. The relatively inexpensive cottonseed soapstock and tall oil pitch soap did not perform well, while the oleic acid, tall oil fatty acid, and the mixture of petroleum sulfonate and tall oil fatty acid met the industry requirement in terms of recovery and selectivity.

Four isostearic/iso-oleic acid type fatty acid collectors, supplied by divisions of International Paper, were compared with a commercial grade oleic acid and a tall oil as phosphate collectors using standard laboratory conditioning and flotation procedures. The most selective collector evaluated appeared to be Century 1108, a high isostearic acid type reagent. However, this excellent performing reagent was concluded to be too expensive. The overall most promising reagent was Century MO-5. This collector was essentially an iso-oleic acid/stearic acid mixture.

Four all-anionic flotation flowsheets were developed. These flowsheets simplify the current practice by eliminating the acid scrubbing and amine flotation steps. These flowsheets achieved higher recovery with an overall lower cost, but produced higher Insol (9-11%) products.

This research investigated the performance of six types of amines (primary, secondary, tertiary, quaternary, ether, and condensate) on the cleaning step of the rougher concentrates for the Crago process, and the effect of particle size on the performance of each type of amine. The research also studied the effect of slimes (tolerance) of these six types of amines and Perco 90L polymer addition on the amine flotation step of the Reverse Crago process.

To improve the all anionic flotation processes, several selectivity enhancement methods were evaluated, with addition of lignosulfonates showing promising results.