Flotation Chemistry Of Molybdenite-Kaolinite Based On Calcium Ions Effect

Molybdenum is considered as non-renewable strategic mineral resources,which got an extensive application in industry as its excellent function.Molybdenite is considered as the main mineral source of molybdenum and has natural floatability.Kaolinite,as a typical clay mineral,is often associated with molybdenite.Besides kaolinite,there is also a lot of calcium ions in molybdenite flotation system.These calcium ions will have an effect on the dispersion and aggregation of molybdenite and kaolinite.Thus,in this dissertation,flotation chemistry of molybdenite-kaolinite based on calcium ions effect was researched.The influence rule of calcium ions on molybdenite and kaolinite separation was studied.Moreover,the calcium ions effect on the flotation chemistry of molybdenum-kaolinite was explained from a microscopic perspective by solution chemical analysis,colloid interface force calculation and measurement,ion adsorption analysis,which can provide a micro point on the interaction between solid-liquid interface and solid-solid interface,and provide theoretical basis for molybdenite efficient utilization.First,the surface phsico-chemical properties of molybdenite and kaolinite were characterized by Zeta potential tests,surface contact angle tests and surface free energy calculation.The results showed that molybdenite has a bigger point of zero charge than kaolinite.The molybdenite face surface was more hydrophobic than its edge surface.Results of surface free energy component presented that:for the face surface,the dispersion component occupied almost 100%.The polar polar component for the edge surface of molybdenite was about 7%of the total.The kaolinite surface has a higher dispersion component and lower polarity component.The calcium ion effect on flotation performance and surface chemistry of molybdenite and kaolinite were studied in weak acidity solutions with kerosene used as collector.The results showed that the molybdenite recovery decreased while the kaolinite increased with the increase of calcium ion concentration.Calcium ions can adsorbed on mineral surface as the form of Ca²⁺and its hydroxyl complex CaOH⁺.The contact angle of molybdenite edge surface reduced more than the face surface since calcium ions adsorption.The adsorption kinetics of calcium ions on the surface of molybdenite and kaolinite followed the quasi-first-order kinetic model well,and the adsorption isotherm followed the Freundlich adsorption isotherm model well.The effects of calcium ion on the flotation separation of molybdenite and kaolinite were studied,and the essence was revealed by dispersion tests,Zeta potential distribution tests and SEM-EDS analysis.The results showed that the recovery and grade of molybdenite decreased with kaolinite content and calcium ion concentration.The molybdenite and kaolinite dispered in the deionized water,while they can coaggregation through calcium bridge in calcium ions solution.The mechanism of calcium ion effect on flotation separation of molybdenite and kaolinite was revealed by the AFM tests and EDLVO theoretical calculation on a micro level.The molybdenite edge surface potential reduced larger than that of the face surface as the calcium ion concentration increased.The measured force curve was in good agreement with the EDLVO calculation.The EDLVO theoretical calculation showed that the attraction force between molybdenite and kaolinite particles was mainly contributed by hydrophobic force.The attraction force between particles increased with the calcium ion concentration.Kaolinite particles were preferentially adhered to the molybdenite face surface.The adsorption mechanism of calcium ion on mineral surface was studied based on quantum chemical calculation.Ca²⁺was more tend to adsorb on Mo atoms on the molybdenite S-?100?surface by forming 3d-2p hybrid orbital between Ca atom and S atom.CaOH⁺hardly adsorbed on molybdenite?001?surface,while it can adsorbed on top of S atom at the surface of mo-?100?.For kaolinite,Ca²⁺and CaOH⁺prefer to adsorb on its Si?001?surface as it had more negative charge,moreover the adsorption structure is the most stable in hollow site.Where,Ca²⁺mainly adsorbed on the Si?001?surface through 3d-2p and 3p-2s hybrid orbitals formed between Ca atom and O atom,while CaOH⁺adsorbed on the Si?001?surface through 3p-2s hybrid orbital.The regulation of calcium ions effect on molybdenum-kaolinite flotation was studied by flotation experiments,and the mechanism was revealed by dispersion tests,Zeta potential tests and solution chemical calculation.Better flotation performance of molybdenite was obtained using the sodium hexametaphosphate and sodium polyphosphate as modifier than that of sodium carbonate and sodium silicate.With the increase of modifier dosage,the coaggregation performance between molybdenite and kaolinite were weakened.The stronger adsorption of modifier on kaolinite lead to more reduced surface potential results than that of molybdenite,and the order of decreased magnitude was sodium hexametaphosphate>sodium polyphosphate>sodium silicate>sodium carbonate.When sodium silicate was used as modifier,there was no calcium carbonate precipitation form,while sodium carbonate,and sodium hexametaphosphate could form precipitation which affected the hydrophilicity of minerals.This paper contains 108 figures,26 tables and 168 pieces of references.