The Interaction Mechanism of Metal Ions with Mineral Surfaces in Bastnaesite Flotation

Author:Cao Shi Ming

Supervisor:cao yi jun


Degree Year:2019





The rapid consumption of rare earth sources in China worsens its current situation of strategic advantage and sustainable utilization due to the various issues in the exploitation of rare earth sources.Therefore,the efficient flotation of bastnaesite is of great significance.However,the physicochemical properties of bastnaesite solid-liquid interface,complicated ironic environment of bastnaesite flotation,the interaction mechanism of metal ions with mineral surface and the influence of metal ions on flotation are still insufficiently studied,consequently leading to limitations to the developments of flotation theories and applications.In this thesis,the determination of metal ions in practical bastnaesite flotation environment and the metal ion release of primary minerals in bastnaesite flotation were first conducted to investigate the varieties of metal ions in practical flotation pulp.The influence of primary metal ions on the flotation of bastnaesite,celestite and fluorite were studied by microflotation experiments.On the basis of crystal chemistry and cleavage study of bastnaesite,celestite and fluorite,common cleavage planes of the minerals were confirmed,and further studies about the propertities of cleavage planes,especially the liquid-solid interfaces like surface groups were conducted.Then the adsorption of metal ions on liquid-solid interfaces of minerals were investigated by advanced analysis methods and fitting of adsorption results.Referring to the conclusions of aforementioned studies,the author explored the influence mechanism of metal ions on the flotation of bastnaesite system in the absence and presence of regulator.Finally,the flotation of prctical ore was conducted and satisfactory results were obtained.In bastnaesite flotation system,calcite,dolomite and fluorite,which are common gangue minerals,had strong ability of releasing Ca2+to flotation pulp.The dolomite can release Mg2+to the flotation pulp.Celestite,which is characterized by strong solubility,was capable of releasing a large amount of Sr2+to the environment.When bastnaesite occurred with iron minerals,Fe3+can also be released to the pulp.However,the bastnaesite can hardly release inherent rare earth metal ions.The additional fresh water also imported metal ions to flotation environment.All of the above mentioned metal ions can depress the flotation of bastnaesite,celestite and fluorite when salicylhydroxamic acid(SHA)was used as collector.Fe3+exerted the strongest depression,followed by Al3+,the implications of divalent alkali metal ion on flotation were relatively much lower.The main deterioration of celestite on bastnaesite flotation was attributed to the release of Sr2+from celestite to the flotation environment;while fluorite was characterized by not only strong ability of releasing Ca2+to the flotation environment but also strong floatability,therefore deteriorated the flotation separation of bastnaesite from gangue minerals.The celestite and fluorite was remarkably depressed in the presence of metal ions and sodium fluorosilicate,while bastnaesite flotation was slightly depressed.Based on crystal chemistry of minerals,the broken bonds density and interlayer spacing were used as primary factors,together with XRD measurements were applied to analyze the cleavage propertities of minerals.Under external forces,the bastnaesite mostly preferred to to aleavage along{110}plane,followed by{100}and{103}planes.The{001}surface were significantly exposed under sufficient grinding despite its high surface energy.The broken bonds on bastnaesite cleavage surface were mainly composed of≡Ce3+and≡CO32-,as well as a small amount of≡F-.In aqueous environment,these broken bonds transformed to≡CeOH0,≡CO3H0 and≡FH0surface groups,respectively.The primiary cleavage plane of celestite is{001}plane,followed by{210}plane.The≡Sr2+and≡SO42-broken bonds of celestite cleavage surface transformed to≡SrOH0 and≡SO4H0 surface groups in aqueous environment.The primiary cleavage plane of fluorite is{111}plane,followed by{110}plane.The≡Ca2+and≡F-broken bonds of fluorite cleavage surface transformed to≡CaOH0 and≡FH0 surface groups in aqueous environment.Multiplied aspects such as cleavage plane structures,element components and broken bond properties,determined the properties of cleavage planes.Due to surface analysis and the fitting of adsorption results,the interaction mechanism of metal ions with mineral surfaces were investigated.The≡CeOH0surface group is the adsorption site for metal ions on the solid-liquid interface of bastnaesite.Ca2+and Mg2+were hardly adsorbed on bastnaesite surface;Sr2+was adsorbed mainly by the formation of≡Ce-O-Sr+surface complexes;and Al3+and Fe3+were obviously adsorbed.Al3+and Fe3+species complexed by poly-coordination with O atoms of surface≡CeOH0 groups on bastnaesite surface,indicating they were mainly adsorbed by hydroxide precipitation.Ca2+and Mg2+were hardly adsorbed on celestite surface,Al3+might be slightly adsorbed on celestite surface by hydroxide precipitation and obvious hydroxide precipitation occurred during Fe3+adsorption.Mg2+and Sr2+were hardly adsorbed on fluorite surface,Al3+and Fe3+were mainly adsorbed by physical adsorption.The bivalent alkali metal ions exerted depression mainly by the consumption of collector,among which Sr2+can also be adsorbed on bastnaesite surface and hindered collector adsorption.The depression of Al3+and Fe3+can be attributed two reasons:on the one hand,the adsorbed metal ions bindered the adsorption site for collector;on the other hand,the residual metal ions in flotation pulp consumed collector by complexing with collector molecules.The interaction of metal ions with sodium fluorosilicate leading to the transformation of solution compositions and changed corresponding adsorption on mineral surface,and therefore exerted implications on mineral flotation.This paper contains 81 figures,27 tables and 239 pieces of references.