Abstract
It has been discovered that water insoluble alcoholic solutions of alkyl hydroxamic acids serve as selective collectors for the flotation of phosphate mineral resources (Miller and others 2000). Critical aspects of the composition and structure of these new collectors have been considered with respect to their effectiveness in phosphate flotation using microflotation techniques. The wetting characteristics of the new collector at fluorapatite, francolite, dolomite and quartz surfaces have been examined by contact angle measurements and high speed video experiments. The new collector is commercially available from Cytec as AERO 6493.
The effectiveness of the new collector chemistry is demonstrated by the results from single-stage bench-scale flotation experiments with AERO 6493 for feed material from plants in Florida, North Carolina, and Utah. In the best case, from experiments with low grade (5% P2O5) coarse feed (16×35 mesh) from central Florida, a single-stage phosphate recovery of 95% was achieved with a concentrate grade of 31% P2O5. Such a separation efficiency could not be achieved using the traditional fatty acid/fuel oil collectors as is evident from comparison of the respective grade/recovery curves. AERO 6493 has been evaluated for use by the Florida phosphate industry in pilot-plant studies at Jacobs Engineering and the experimental results, which confirm results from laboratory experiments, show improved separation efficiency especially for coarse phosphate flotation feed from the Cargill SFM plant.
As expected, economic analysis of the new flotation chemistry with AERO 6493 shows a strong dependence on the reagent price. If the cost of AERO 6493 could be reduced to $1.80/lb, the single-stage flotation of coarse phosphate with the alkyl hydroxamic acid/alcohol collector would be competitive with the traditional double float process using fatty acid and fuel oil.
The environmental impact regarding use of the hydroxamic acid collector in phosphate flotation was considered with respect to water quality. Literature review and experimental results indicate that there is no significant environmental impact from the utilization of the new collector.
Jan D. Miller, Xuming Wang, and Minhua Li - University of Utah