Study On Synergistic Flotation Of High-iron Phosphate With Surfactant And Modified Fatty Acid

As global phosphate rock grade keeps falling continuously, the middle and low graderefractory phosphate ore has became the main research object. Flotation is animportant method for the mid and low grade phosphate ore beneficiation. Themodification of fatty acids and the compounding of fatty acids and surfactantsbecome two potential study directions for phosphate flotation reagents. The recoveryof apatite is difficult to enhance in industrial flotation process of a foreign high-ironphosphate ore. In this paper, a kind of modified fatty acid sodium called MG-2(α-peroxide hydroxyl fatty acid sodium) and a new homemade anionic surfactantcalled SS (fatty acid sulfonate) were investigated as a mixed collector for thishigh-iron phosphate ore flotation to solve the problem. Consequently, the effectiveseparation of apatite and gangue minerals dominated by limonite was realized.Flotation tests of pure mineral for apatite showed that MG-2had a strongercollecting capability than NaOL. With reagent concentrations of120mg/L or less,obviously, a higher recovery than using NaOL was obtained by using MG-2, whichindicated that MG-2had the property of low temperature resistance. Limonite puremineral experiments demonstrated that its floatability was depressed when starch wasadded into flotation system. Especially, the depressant performance was greatlyeffective when pH values varied from9to12. Limonite was depressed completelywhile the dosage of starch reached to a certain value.The synergistic test between surfactants and fatty acids showed that the additionof3surfactants (SS, SDBS and Tween-80) could contribute to the improvement offlotation effect both in MG-2and NaOL flotation systems. In particularly, SS had themost obvious synergistic effect toward them. It was clearly that the synergistic actionof surfactants on MG-2was better than on NaOL in this research. After that, the bestreagent ratio of MG-2and SS in the mixed collector was determined throughmatching test. The result indicated that the best ratio was m(MG-2):m(SS)=9:1. It wasinterested that collecting strength of mixed collector would decrease due to increasingthe dosage proportion of SS.A direct flotation process experiment was carried out on this high-iron phosphateore by using MG-2and SS as a mixed collector. When flotation temperature was 35℃, the flotation conditions for rough separation were determined. NaOH was a more effective pH regulator compared to NaCO3for this phosphate separation. The optimal pulp pH value was10.1while the dosage of NaOH was500g/t. In addition, the most suitable dose of mixed collector was800g/t. The depressants orthogonal test showed that the dosage of either starch or water glass was800g/t. The feed ore with P2O5grade of14.30%, Fe2O3content of29.30%and SiO2content of14.93%was operated by adopting the closed circuit flotation flow sheet of single-stage roughing, two-stage cleaning and the middlings returning in order. Finally, the concentrate with P2O5grade of32.22%and recovery of77.42%was obtained. The content of Fe2O3and SiO2which were harmful elements dropped to7.47%and5.16%respectively in the concentrate. In conclusion, the flotation experiment achieved the desired effect of separation. Its index was superior to that in industrial process. The recovery of apatite had raised by approximately10%.The adsorption of MG-2on the apatite surface made its Zeta potential decline rapidly. When MG-2was added together with SS, Zeta potential of apatite continued drifting toward negative. The study on limonite Zeta potential revealed that anion starch absorbed onto the surface of limonite. It was supposed that complexation reaction of iron with starch led to the formulation of hydrophilic film, resulting in depressing limonite. Interaction parameter (βm) and activity coefficient (f1m) of mixed reagent were calculated by theory model of mixed solution. βm<0and f1m<1indicated that the interaction between MG-2and SS was attraction. Compared to using MG-2only, the addition of SS made the relative wetting contact angle of apatite surface increase by about10°, which showed that apatite was more hydrophobic. Furthermore, infrared spectrum analysis revealed that MG-2absorbed on the surface of apatite by chemisorption, while the action between SS and apatite was physical adsorption. When combined collector acted on apatite, coadsorption occurred. Van deer Waals force and Hydrogen bond strengthened the interaction.