Acyl Thioamide Collectors: Flotation Performance And Mechanism On Sulfide Minerals

Flotation collector is an essential agent in the process of mineral flotation.The design and synthesis of the collector with superior collecting ability has become a hot spot in the field of mineral flotation.A series of acyl thioamide collectors were synthesized in this paper.The S and O coordination atoms in its molecular structure are easy to chelate with metal atoms,which can significantly improve the flotation performance of sulfide minerals.At the same time,the flotation performance and mechanism of acyl thioamide collectors on sulfide minerals surface were investigated by a series of detection methods.The molecular geometry parameters and quantitative properties of the acyl thioamide collectors were carried out by quantum chemical calculation,including acetyl thiobenzamide(ATBA),butyryl thiobenzamide(BTBA),and trimethylacetyl thiobenzamide(TTBA),and compared with traditional collector O-isopropyl-N-ethyl-thionocarbamate(IPETC).The relationship between flotation performance and acting sites of acyl thioamides were predicted.The hydrophobic order of IPETC and acyl thioamide collectors followed as : TTBA > BTBA >IPETC > ATBA,which indicated that the hydrophobicity of TTBA and BTBA were stronger than IPETC,and the hydrophobicity of ATBA was weaker than IPETC.The electrostatic potential diagram showed that the positive charge of acyl thioamides mainly concentrated on the H atoms connected with N atoms,while the negative charge mainly concentrated on the O atoms of carbonyl groups and the S atoms of sulfur carbonyl groups.Then the main interaction sites of moleculars with minerals were C=S and C=O groups.The order of HOMO energy values of the four collectors was TTBA > BTBA > ATBA > IPETC,which indicated that acyl thioamides possessed stronger electron donating ability than IPETC.Three acyl thioamides were synthesized by using benzamide and chloride as reactants,and pyridine as catalyst in acetone solvant.The influence of raw material mole ratio,dosage of solvent,reaction time and temperature on the yield of products were investigated.Under the optimal reaction conditions,the yields of ATBA,BTBA and TTBA were 87.2%,86.2% and 82.3%,respectively.The products were characterized by UV,FTIR,NMR and GC-MS,and the target products were confirmed.The flotation and separation performance of these three acyl thioamide collectors ATBA,BTBA,TTBA and traditional collector IPETC on chalcopyrite and pyrite were investigated.The results of single mineral flotation experiments showed that,compared with IPETC,acyl thioamide collectors possessed stronger collecting ability for chalcopyrite and better selectivity for pyrite.Contact angle tests showed that acyl thioamide collectors could significantly improve the surface hydrophobicity of chalcopyrite,rather than pyrite.Zeta potential tests showed that TTBA could selectively adsorb on the surface of chalcopyrite and make the isoelectric points shift negatively.However,after the interaction between TTBA and pyrite,the isoelectric points of pyrite changed little,indicating that TTBA was easier to adsorb on the surface of chalcopyrite.The results of adsorption thermodynamics and kinetics showed that the adsorption of TTBA on chalcopyrite surface was an endothermic-spontaneous chemisorption process with entropy increased.Based on the DFT calculation and XPS detection analysis,it could be seen that the active centers of TTBA were located on C=S and C=O groups,and the S and O atoms in the molecule interacted with the Cu atoms on chalcopyrite surface by the formation of Cu-S and Cu-O bonds.