Fundamental Research On The Efficient Separation Of Complex Copper-Zinc Sulfide Ore By Floatation

The complex polymetallic copper-zinc sulfide ore in Dachang, Tongkeng ore district, belongs to primary sulfide ore, the gross ore is5152.33wt and the amounts of Zn metal, Cu meltal are212.72wt and8.46wt, respectively. The ore is characterized by complex mineral composition and fine dissemination particle size. In order to improve the separation and comprehensive recovery of copper and zinc, the main sulfide minerals in the ore including chalcopyrite, sphalerite, marmatite and pyrite are chosen as the objects investigated.The results show that, the collectors named Mercapto Benzothiazole (MBT) and tert-dodecyl mercaptan (TDM) are more effective in collecting and selectiving for copper and zinc sulfide minerals, respectively. Meanwhile, N, N-Dimethyldi-Thiocarbamate (DMDC) is a promising depressant for the activated sphalerite and marmatite. The characteristics of interactions of Mercapto Benzothiazole, tert-dodecyl mercaptan and sodium salt of N, N-Dimethyldi-Thiocarbamate with chalcopyrite, sphalerite/marmatite and pyrite are tested, respectively. Additional analytical techniques (FTIR, UV spectrum, XPS and electrochemistry analysis) are employed in the current study to point out the mechanisms which are involved in the interaction of reagents with sulfide minerals. Meanwhile, the density functional theory is employed. Main conclusions and innovations of this dissertation are listed as follows:The results shown in FTIR spectra indicate that, MBT can adsorb on chalcopyrite surface chemically, while there are no characteristic peaks apperaed on the sphalerite and marmatite surfaces. The results of frontier obital energy show that, the reactions between MBT and sulfide minereals are, from high to low, chalcopyrte> marmatite> sphalerite, which further demonstrates MBT has a good selective floatation for Cu/Zn sulfide ores. The adsorption of MBT on chalcopyrite (112) surface is spontaneously, the3p orbits of S atom and N atom provide electrons to Cu atom to form positive coordinate bond, while MBT is hardly to adsorb on the sphalerite (110) surface. The electrochemistry results show that, after chalcopyrite electrode conditioned with MBT, the hydrophobic product of Cu(MBT)2formed on its surface, the self-oxidation of chalcopyrite is blocked, which result in the reduction of formation of Cu(OH)2and Fe(OH)3, thus the electrochemical electron transfer rate is accelerated.The interactions between DMDC and minerals/metal ions have been investigated by FTIR and UV spectrum, the reason for the effectively depress for sphalerite lies two aspects:①DMDC can adsorb on the mineral surfaces chemically. Butyl xanthate and DMDC can co-adsorb on the chalcopyrite surface, however, less butyl xanthate species adsorb on sphalerite and marmatite surfaces.②Compared with Zn2+, Fe2+, DMDC has a stronger capacity of complexing with Cu+and the product is Cu(DMDC)2, which indicates that DMDC, in flotation, is effective in preventing copper activation of sphalerite and marmatite, which in turn results in depression. After being conditioned with DMDC, shown in XPS, the displacements of binding energies of metal orbits on the three minerals are negative, which indicates that the electron clound density in electron shell increases, which means that the free valence orbitals obtain or share electrons with other atoms. There are lone electron pairs in S and N atoms of DMDC, which can react with metals probably. The frontier orbital analysis indicates that S aotm on double bond in DMDC is the active site for adsorption. The calculated results of electronic structure show that the3p orbit of S atom provides electrons to metal atoms to form positive coordinate bonds. When DMDC is putted into the electrochemical system, there is a new peak of (DMDC)2appeared on chalcopyrite electrode and sphalerite electrode respectively, while there is no change on marmatite electrode, which is attribute to the formation of hydroxy compounds. The results shown in electrochemical corrosion indicate that DMDC and butyl xanthate will be oxidized more easilier when they coexist in the electrochemical system.Compared with butyl xanthate, the tert-dodecyl mercaptan has a better collecting efficiency for sphalerite and marmatite, which can chemi-adsorb on the mineral surfaces. The results of density functional theory further show that the collecting capability is optimal for sphalerite and marmatite, comparing with diethyldithiocarbamate and butyl xanthate. When the pH of slurry is adjusted by saturated lime water, the adsorbance of tert-dodecyl mercaptan on pyrite sharply decreases in alkaline condition. The adsorptions of tert-dodecyl mercaptan on sphalerite (110) surface and pyrite (100) surface are spontaneously. The results of electrochemistry show that the lime can lead to the preoxidation of pyrite electrode, which prevents the oxido-reduction of tert-dodecyl mercaptan on pyrite surface. Lime can not affect the electrochemical reactions of tert-dodecyl mercaptan on sphalerite and marmatite surfaces.The grade of Cu and Zn is0.18%,3.53%respectively in Tongkeng. In priority procedure, when butyl xanthate is used as copper collector, the lime and DMDC are putted into the mill directely, or the MBT is chosen as the copper collector, ZnSO4and Na2SO3are as the depressants; for the collecting of zinc sulfide, the tert-dodecyl mercaptan is chosen as collector, the closed circuit results indicate that the flotation separation and collecting of copper and zinc are satisfied. Copper and zinc concentrate reach the "copper concentrate quality standards" and "zinc concerntrate quality standard", respectively. Compared with priority procedure, the iso-floatability process has obvious superiority in the separation of zinc sulfide from copper sulfide.