Floatation Behavior Study Of Rare Earth-containing Phosphorite From Canada

Mineral separation of complicated rare earth ore is a difficult work for the area of mineral processing. Although some rare earth collectors such as hydroximic acid have strong selectivity and they are effective for the rare earth floatation, the much more complicated practical minerals make the study of process mineralogy, processing conditions and mechanism of mineral separation very necessary for a suitable method for a practical ore. In this paper, based on the process mineralogy property of rare earth-containing phosphorite from Canada, the floatation method is confirmed and the condition floatation and closed-circuit floatation is made; then floatation behavior, mineral surface property, solution chemistry of floatation agents and infra-red spectra of medicament-absorbing mineral of mono- mineral, bastnaesite and apatite, is studied and analyzed; what's more, the mechanism of action of mineral and medicament is studied.First of all, through process mineralogy research of practical mineral, the composition and content of each element and mineral are confirmed. The research shows:light rare earth such as cerium (CeO2), lanthanum (La2O3) and neodymium (Nd2O3) is the main rare earth components which account for 77.74% and cerium (CeO2) accounts for 40.38%. Valuable minerals in the ore include apatite and rare-earth minerals (orthite, bastnaesite and urdite), gangue minerals primarily include pyroxene, hornblende, chlorite, feldspar, calcite and so on. Dissemination character and dissemination granularity of each valuable minerals in the ore are also studied.Secondly, based on the process mineralogy characteristics, floatation circuit by which that phosphorus and rare-earth mineral are reclaimed together, is adopted. Through the research of grinding test, regulators' dosage and combination test, and collectors' dosage and combination test, floatation conditions are confirmed that fineness of grinding-0.074 mm 85%,using sodium fluosilicate and fulvic acid as combination depressor for gangue mineral, and using 731# and Maoniuping collector as combination collector for phosphorus and rare earth, to process the practical mineral with two roughing, two cleaning and one scavenging, so as to get phosphorus and rare earth by bulk flotation. Finally, mixed concentrate is gotten, containing REO 4.39%, P2O5 26.80%, recovery of rare earth and phosphorus 86.85% and 97.63% respectively.Mono-mineral condition tests show:under each conditions, the floatation effect of sodium oleate and Maoniuping collector is better than Salicylhydroxamic acid. Selectivity of sodium oleate is comparatively weak, while selectivity of hydroximic acid towards bastnaesite is better. Maoniuping collector has the best floatation effect and sodium oleate takes second place. Under each condition, Salicylhydroxamic acid does not have catching ability towards apatite. Maoniuping has the best collecting ability towards the two kinds of minerals, while it's selectivity is poor. Collecting ability of sodium oleate is placed in the middle. Salicyl-hydroxamic acid has the worst collecting ability, while it's selectivity is the best. Floatation result of man-made mixed mineral is as following:concentrate recovery by sodium oleate is 34.75%,concentrate recovery by Salicylhydroxamic acid is 8.46%, however, bastnaesite accounts for 80.57% in concentrate by Salicylhydroxamic acid, whereas 54.02% in concentrate by sodium oleate.Based on the property analysis of minerals and medicaments in solution, following conclusions are drawn:Ce(OH)2+ concentration in the solution is uppermost at pH=8～9, at the same time, Ce(OH)2+ is the key of chelate reaction of hydroximic acid and mineral; that is the reason why floatation effect is the best at pH=8～9; the floatation effect of sodium oleate towards bastnaesite is worse and worse with the rising of pH in the range of 7～11 and this change is almost the same with the concentration change of RCOOH·RCOO-, so maybe acid-soap dimer has decisive effect for floatation. Substantive Ca2+ ions of apatite dissolve out in the solution, what's more, calcium ion and sodium oleate can react to deposit. At the same time, sodium carbonate, as pH regulator, can also make precipitation reaction with calcium ions. With the rising of pH, calcium ions should act with sodium carbonate at first, because of which the consumption of collector is lower and more collector can react effectively with mineral. As a result, the floatation effect is better. The stability of chelate formed by hydroximic acid and Ca2+ is worse than that formed by hydroximic acid and Ce3+, so the collecting mechanism of hydroximic acid towards apatite isn't the chelation of medicament and mineral.Infra-red spectra study of medicament-absorbing mineral shows:the action of bastnaesite and hydroximic acid results in the decreasement or even disappearance of associated (OH)", furthermore, new chemical bonds are formed, which prove the presence of chemisorption and the chemisorption production is mainly the five- membered ring chelate formed by reaction of hydroximic acid and bastnaesite surface; the action of bastnaesite and sodium oleate results in the decreasement or disappearance of associated (OH)-, which show that no obvious surface chemical reaction of sodium oleate and bastnaesite have taken place and the adsorptive action is primarily electrostatic adsorption and molecular adsorption. No obvious change exists in the infra-red spectra of three kind of medicament-absorbing apatite.