Synthesis Of A New Cationic Organosilicon Collector And Its Flotation Characteristics And Mechanism On Aluminosilicate Minerals

To the significant demand of desilication of bauxite ores by reverse flotation in China, a kind of new cationic organosilicon surfactant was developed as collector of aluminosilicate minerals. The synthesis of this collector was studied on, as well as its flotation performance and mechanism on diaspore and aluminosilicate minerals.Firstly, the organosilicon cationic collectors were synthesized and characterized systematically. The organosilicon quaternary ammonium collectors were obtained by one-step reaction which conducted at 80?for 37 hours, with halogenated siloxane coupling agent:tertiary aliphatic amine:KI=1.1:1:0.01 by the mole ratio, using anhydrous ethanol as solvent, protected the reaction system with N2. The percent conversion of tertiary aliphatic amine was more than 90%. The organosilicon CH3Si(OSi(CH3)3)2(CH2)3NH(CH2)2NH2(TAS101) collector was synthesized when reaction was conducted at 90?for 8 hours, with CH3Si(OCH3)2(CH2)3NH(CH2)2NH2(TAS 100):hexamethyldisiloxane (MM)= 1:5 by the mole ratio, using anhydrous ethanol as solvent and 10%(CH3)4NOH solution as activator, protected the reaction system with N2. The percent conversion of TAS100 was about 90%. The CH3Si(OCH3)2(CH2)3NH(CH2)2NHCH2(C6H5)(TAS550) collector was synthesized when reaction was conducted at 80?for 8 hours, with TAS100:benzyl chloride=1:1.5 by the mole ratio, using anhydrous ethanol as solvent, protected the reaction system with N2. The collector CH3Si[OSi(CH3)3]2(CH2)3NH(CH2)2NHCH2(C6H5)(QAS550) was obtained with TAS101 took the place of TAS100 in the reaction mentioned above. Structures and properties of final products were characterized by FT-IR spectrum,1HNMR and 13CNMR et al. The purity of every new organosilicon collector was more than 90%.The relationship of molecular structures and flotation performance of collectors were investigated. The results indicated that organosilicon quaternary ammonium was an effective collector of kaolinite, pyrophyllite and illite minerals in a wide pH range, and their collecting ability for diaspore increased firstly and then decreased drastically with the increase of pulp pH, and the optimum pulp pH for the separation of diaspore from kaolinite was around 11. The collecting ability of organosilicon quaternary ammoniums for aluminosilicate minerals receded with the lengthening of backbone in tertiary aliphatic amine. In pH=11 the diaspore was been effectively separated from kaolinite with 4×10-4 M [(C2H5O)3Si(CH2)3N(CH3)2C12H25]Cl(QAS222) as collector. In the wide range of pH=4-10, the collectors of organosilicon primary amine and secondary amine could improve the minerals'floatability remarkably. The collecting ability of primary amine TAS101 was better than that of the secondary amine TAS550 and QAS550 for aluminosilicate minerals. The diaspore and kaolinite were separated successfully in the reverse flotation with 1.0×10-3 M TAS101 collectors and 500mg/L soluble starch depressors in pulp pH=8.In order to de-silicate from some diasporic bauxite of Henan Province, of which the Al2O3 grade and A/S were 63.92%,6.07 respectively, the closed circuit flotation experiments were conducted with the [(C2H5O)3Si(CH2)3N(CH3)2C,2H25/C14H29]C1(QAS224) and TAS101 as collectors. When the diasporic bauxite ore was processed by single-stage rougher, two-stage cleaner and two-stage scavenger with 700g/t QAS224 in pulp pH=11, A12O3 grade, A12O3 recovery and the A/S of concentrate were 67.79%,81.72%and 9.67 respectively. When the diasporic bauxite ore was processed by single-stage rougher, two-stage cleaner and two-stage scavenger with 720g/t TAS101 and 1320g/t soluble starch in pulp pH=11, A12O3 grade, Al2O3 recovery and the A/S of floating concentrate were 68.52%,83.34%and 9.58 respectively. The collecting ability of combination of QAS224 and TAS101 was stronger than each one of them. At 540g/t QAS101,180g/t TAS101 and 1320g/t soluble starch in pulp pH=11, A12O3 grade, Al2O3 recovery and the A/S of concentrate were 68.98%,85.42%and 10.34 respectively with same flowsheet. The quality of concentrates reached the feeding requirement of Bayer process.The study on acting mechanism of the collector QAS222 with the minerals showed that there were electrostatic adsorptions, hydrogen binding and chemical adsorptions between QAS222 and the three aluminosilicate minerals in pulp pH=11, produced more Si-O, Si-O-Si and Si-O-A1 bonds and made the QAS222 adsorbed steadily in these minerals'surfaces. So the Zeta potentials increased and contact angle turned bigger and the floatability became better. Under the same conditions it was difficult to QAS222 to be adsorbed in the diaspore mineral surface. So the diaspore may be effectively separated from aluminosilicate minerals by collector QAS222 in pulp pH=11.In pulp pH=11 TAS101 may adsorbed in the four minerals surfaces and improved their floatability. Soluble starch was effective depressor for diaspore. The diaspore mineral can not act with TAS101 if it had been depressed by soluble starch in pulp pH=11 and its floatability always was bad. The soluble starch can not change the floatability of aluminosilicate minerals. The diaspore could be effectively separated from aluminosilicate minerals with TAS101 as collector and the soluble starch as depressor in pulp pH=11. The study on acting mechanism of the TAS101 with the minerals indicated that silicon groups of TAS101 had hydrophobic interaction, and there were electrostatic adsorptions in the diaspore surface and hydrogen bond interactions as well as electrostatic adsorptions in the other three aluminosilicate minerals'surfaces.