Synthesis Of Novel Collectors For Sulfide Ores And Research On Their Flotation Properties

Sulfide ores are main mineral resource of non-ferrous metals, collectors are the technical core. N-ethoxycarbonyl thiocarbamates, N-ethoxycarbonyl thioureas and N-ethoxycarbonyl dithiocarbamate with new structures were synthesized using N-ethoxycarbonyl isothiocyanate as intermediate based on the past research, diethoxycarbonyl dithionocarbamates and diethoxycarbonyl dithioureas were developed, either."One-pot" synthesis of N-ethoxycarbonyl isothiocyanate and its derivatives in organic phase was achieved via the preparation of schiff base phase transfer catalysts. The flotation performance of the novel collectors to monominerals and sulfide ores were investigated, the interactions between collectors and ores were studied.Three types of novel collectors were prepared using isothiocyanate as intermediate and react with alchhol, amine or mercaptan. Isothiocyanate was synthesized with chloroformic ester and thiocyanate as raw materials, catalyzed by bis(4-N,N-dimethyl amino phenyl) methane in water in3～8℃for4h, and the yield was96.2%. O-ethyl-N-ethoxycarbonyl thiocarbamate was synthesized with N-ethoxycarbonyl isothiocyanate and ethanol in45℃for3h, the yield was95.3%. N-propyl-N-ethoxycarbonyl thiourea was synthesized with N-ethoxycarbonyl isothiocyanate and propylamine in0～5℃for1h, the yield was98.2%. S-benzyl-N-ethoxycarbonyl thiocarbamate was synthesized with N-ethoxycarbonyl isothiocyanate and benzyl mercaptan in20℃for4h, the yield was92.53%. With the same condition, several N-ethoxycarbonyl thiocarbamates and N-ethoxycarbonyl thioureas were prepared. Meltingtest, elemental analysis, UV spectrum, infrared spectrum,1H NMR,13C NMR and mass spectrum were adopted to characterize their structures and properties.Addition reaction of isothiocyanate with dihydric alcohol or diamine as raw materials were employed to design the synthesis route of flotation collectors, two novel types of flotation collectors dithiocarbamate(DTC) and dithiourea(DTU) were invented. Synthetic processes were studied systematically by experimental research, and optimal conditions were as follows:reaction temperature50℃and reaction time4h for preparation of DTC; reaction temperature20℃and reaction time1h for preparation of DTU. Two series and six kinds of collectors N,N'-diethoxycarbonyl-0,0'-(1,2-ethylidene) dithionocarbamate(DTC-2), N,N'-diethoxycarbon-yl-O,O'-(1,4-butylidene) dithionocarbamate(DTC-4), N,N'-diethoxycar-bonyl-O,O'-(1,6-hexylidene) dithionocarbamate(DTC-6), N,N'-diethoxy-carbonyl-N",N'"-(1,2-ethylidene) dithiourea(DTU-2), N,N'-diethoxycar-bonyl-N",N"'-(1,2-isopropyl) dithiourea(DTU-3), N,N'-diethoxycarbon-yl-N",N'"-(1,6-hexylidene) dithiourea (DTU-6) were prepared. Yields of DTC are all above95%, yields of DTU are all above83%. Elemental analysis, UV spectrum, infrared spectrum,1H NMR,13C NMR and mass spectrum were adopted to characterize their structures and properties, physical properties such as melting point were also assayed."One-pot" synthesis route of isothiocyanate and its derivatives in organic phase catalyzed by schiff base phasetransfer catalyst with thiocyanate and chloroformic ester as raw materials was designed. Condensation polymerization with ketone (aldehyde) and amine was used to design the synthesis route of schiff base catalyst, and three new schiff based phasetransfer catalysts were developed, they are N-(N',N'-dimethyl amino propyl) methyl isobutyl imine (PMIA), N-phenyl methyl isobutyl imine (BMIA) and N-(N',N'-dimethyl amino propyl) phenyl methyl imine (APPA). N-ethoxylcarbonyl isothiocyanate was prepared with schiff base as catalyst, sodium thiocyanate and ethyl chloroformate as raw materials in organic solvent. Synthetic processes were studied systematically by experimental research, and optimal conditions were as follows:molar ratio of amine to methyl ketone(aldehyde)1:1.10, molar ratio of p-toluenesulfonic acid to amine2.5%:1, reaction temperature110～120℃, and reaction time2h for preparation of schiff base; use PMIA as catalyst, molar ratio of sodium thiocyanate to ethyl chloroformate1.10:1, molar ratio of PMIA to sodium thiocyanate1.5%:1, in diethyl phthaltate, reaction temperature35℃and reaction time2h for preparation of N-ethoxylcarbonyl isothiocyanate. Associative collector DT was prepared, too. Flotation properties of new collectors for monominerals and actual ores of sulfide ore were investigated systematically. Flotation properties of some thiocarbamate collectors for chalcopyrite and pyrite were discussed first, the optimal pH value to efficiently separate them was9.5～10, the optimal dosage of collectors was60.24mg/L. In those collectors, the best one was O-isooctyl-N-ethoxycarbonyl thiocarbamate (IOECTC). Mix IOECTC with BITCM, DTC-4and DTU-3separately in different ratios, the flotation performances of chalcopyrite and pyrite were studied. The results showed that the thicker the collector was, the better the collecting ability was. And among those mixed collectors, BITCM-IOECTC performed best. Chalcopyrite and pyrite before and after complexed with IOECTC or (DTC-4)-IOECTC or (DTU-3)-IOECTC or BITCM-IOECTC were characterized by infrared spectrum, the result indicated that adsorption of collectors on chalcopyrite surface was chemical adsorption and on pyrite surface was physical adsorption. For copper sulfide ore from Dexing copper mine, those novel collectors showed superior flotation properties and selectivity for pyrite with less dosage compared with butyl xanthate. They displayed good collecting ability for copper, and their collecting ability for molybdenum were better than Mac-12. For polymetallic sulfide ore from Gacun, those collectors all performed strong collecting ability for copper sulfide ore, the recoveries were high than BK905in first section to select copper from ores, and the best one was DTC-6. DTC-6and BITCM showed excellent collecting ability for lead sulfide ore compared with BK906, the optimal was BITCM. Flotation performance of copper ores form Peru indicated that, DT showed excellent collecting ability for copper and selectivity for arsenic, and are better than Mac-12and Z-200.The interaction mechanism of new collectors with sulfide ores was discussed. The intensity of interactions between BITCM, DTC, DTU and Cu2+, Fe3+, Ni2+, Pb2+, Zn2+, Ag+, Co2+were examined by ultraviolet spectrum. The results showed that, these collectors could complex with Cu2+easily, could complex with Ni2,Pb2+,Zn2+,Ag+,Co2+, and could hardly complex with Fe3+. The complexing abilities of DTC to Cu2+were weakened with the increase of the chain length, the condition of DTU was opposite. The complexes of DTC-4or DTU-6or BITCM with Cu2+was prepared, they were characterized by infrared spectrum and it was indicated that sulfur atom in C=S may bond with copper. The quantum chemistry calculation results demonstrated that BITCM, DTC-4and DTU-6have better flotation properties compared with now available collectors for sulfide ore such as butyl xanthate, and are hopeful to be put into practice.