Basic Researches On Flotation Of Copper Minerals Of Tonglushan Mine And Application

Copper ore in Tonglushan is a mixtured type containing sulphide minerals like chalcopyrite and oxide minerals like malachite.In this thesis,flotation behavior and mechanism of chalcopyrite,malachite and pyrite in the presence of different collectors and modifiers have been studied based on flotation tests,adsorption measurements,FTIR analysis, electrochemical measurements,solution chemistry calculation and molecular dynamic simulation.Flotation results showed that chalcopyrite exhibited very good flotation response in wider pH range by using butyl xanthate, dithiothiourea and dithiosonite as collectors and remained good floatable even in high pH medium modified by sodium hydroxide or lime.Pyrite exhibited certain floatability in acidic and neutral pH region using butyl xanthate as a collector with descending sharply in alkaline medium.The floatabiltiy of pyrite is very poor when dithiothiourea and dithiosonite used as collectors,indicated that the selectivity of these two collectors is better than butyl xanthate.In the presence of copper ion,the flotation of pyrite can be activated by using butyl xanthate,dithiothiourea and dithiosonite as collectors,which is the main reason that it is very difficult for flotation separation of chalcopyrite from pyrite in copper-sulphur ore due to the activation of copper ion from the dissolution of copper minerals.However,the activation flotation of pyrite by copper ion can be sharply depressed by addition of high dosage lime,which is the case in Tonglushan mine.And the flotation behavior of chalcopyrite and pyrite is also related the pulp potential.The best flotation potential range is -0.1～0.6 V for chalcopyrite and 0.1～0.3V for pyrite by using butyl xanthate as a collector.The adsorption of butyl xanthate,dithiothiourea and dithiosonite on chalcopyrite can take place in wider pH region corresponding to their flotation pH range.With the increase of collector concentration,the adsorption and hence flotation recovery of chalcopyrite increased.The adsorptoion of butyl xanthate on chalcopyrite may be mainly of physical adsorption of dixanthogen.Zeat potential measurements showed that the addition of xanthate and dithiosonite make the zeta potential of chalcopyrite and pyrite more negative indicated the adsorption of the collector on those two minerals.The formation of collector salts for dithiothiourea and dithiosonite have been observed on chalcopyrite by FTIR.The adsorption of butyl xanthate,dithiothiourea and dithiosonite on pyrite has reached to some values but lower than that on chalcopyrite in the wider pH range and tested concentration.The physical adsorption has been revealed by FTIR to show the formation of dixanthogen for xanthate and molecular adsorption for dithiothiourea or dithiosonite on pyrite accounting for their weak collecting ability for pyrite.Cyclic voltamnogram measurements for collector-chalcopyrite system showed that the disulfide may be the main products of xanthate and dithiocarbamate on chalcopyrite.The interaction of chalcopyrite with dithiourea or dithiosonite may be due to the formation of collector salts.Corrosive electrochemistry study demonstrated that with the increase of xanthate concentration,corrosive potential and corrosive current of pyrite electrode decreased gradually while polarization resistance increased.This indicated the formation of surface oxidation products.The capacitive reactance loop radius increased with the increase of xanthate concentration from the EIS of pyrite under different xanthate concentration,indicating that collector film on pyrite surface become thickening,increasing conduction resistance and weakening dissolution of pyrite.It suggested that the adsorption of xanthate on pyrite surface may undergo several steps such as the adsorption of xanthate ion,the formation of dixanthogen due to the oxidation of the adsorbed ion and the increase of dixanthogen film with the increase of xanthate concentration, which is dependent on polarization potential.In initial stage of polarization of pyrite electrode in xanthate solution at about 120 mV,the oxidation of xanthate was gradually increased and collector film on pyrite surface become thickening.It increased the conduction resistance and the growth of collector film is the controlled step resulting in pyrite surface hydrophobic.When the polarization potential increased above 320 mV, capacitive reactance loop radius decreased obviously,at where the collector film fell off and the anodic dissolution of pyrite occurred.It accounted for the flotation potential range of pyrite.The polarization curves and EIS of pyrite under different concentration of NaOH and lime media showed that its corrosive potentials moved towards negatively and corrosive current density decreased with the increase of NaOH and lime concentration.The capacitance loop radius increased with the increase of NaOH and lime concentration.This indicated the formation of hydroxyl iron precipitate on the pyrite surface accounting for the depression of pyrite in high pH media.The electrode surface resistance about 11800Ωin lime medium is much higher than that about 8500Ωin NaOH solution,demonstrated that pyrite surface is strongly oxidized in lime medium.The formation of hydroxyl iron and calcium sulphate precipitates made pyrite surface very hydrophilic and inhibited other electrochemistry reaction on pyrite like collector giving rise to depression of pyrite.The depression effect of lime on pyrite may be stronger than that of NaOH.In the presence of xanthate,corrosive current decreased slightly. Xanthate showed certain inhibiting corrosive function,i.e.adsorption on pyrite even at high pH media.Hence,xanthate still showed some collecting ability on FeS₂ at pH 12 modified by NaOH.However,the corrosive electrochemistry parameters do not change whether adding collector or not at pH12 modified by lime,the radius of capacitive reactance loops changed little in the presence xanthate,indicated that at pH 12 modified by lime,the oxidation products on pyrite surface may be almost same whether absence or presence of collectors.It demonstrated that xanthate exhibited very weak inhibiting corrosion action and hence very weak collecting ability on pyrite at high pH modified by lime.The quantum methods were employed to investigate the mechanism of reaction between mineral surfaces and collectors.Molecular dynamic simulation calculation showed that the HOMO orbitals of butyl xanthate mainly spread over three atoms of the C-S-S group.It indicates that the functionalization group of the C-S-S strongly affects the reduction potential and oxidation potential of molecule.The energy level of xanthate HOMO is -3.4eV.The bottom of conduction band(unoccupied band) of pyrite has a lower value(-3.5eV),which is lower than the HOMO of butyl xanthate(-3.4eV).It is therefore thermodynamically favorable for an electron to jump from the xanthate molecule to pyrite electrode.Xanthate molecule lost one electron become dixanthogen, which render pyrite hydrophobic.For malachite flotation,the collecting ability of fatty type collectors is stronger than that of hydroxamic acid.Without sulphurization,the flotation recovery of malachite can be above 90%by using sodium oleate. When thio-collector was used,sodium sulphide is required for malachite flotation.The concentration of sodium suphide and sulphurization time has some effects on thio-collector flotation of malachite.The best sulphuirzation pH range is 7～9 corresponding to the pH region with HS-as dominant species in solution.When mixed hydroxamic acid and thio-collector was used,the flotation recovery of malachite increased. FTIR spectra revealed that butyl xanthate,oleate and new type fatty acid are adsorbed on malachite.Finally,batch flotation tests for Tonglushan copper ore have been conducted.The best reagent schemes are lime as pH modifier and two or three thio-compounds as mixtured collectors.The grade and recovery of copper concentrate can be increased.