Flotation Characteristics And Adsorption Mechanism Of The Aluminosilicate Minerals By A Class Of Bis-Quaternary Ammonium Salt Gemini Collector

Due to the character in most of the diasporic bauxite in China, a class of novel bis-quaternary ammionium salt cationic surfactants was used as revers flotation collector for the de-silication of bauxite ores, based on the invesgations of structure-activity relationship between the amine cationic collectors and their collecting ability. The results in this work have an important theory meaning and an actual application value.Differences of structure, crystal and solution properties between diaspore and the layered aluminosilicates are studied in this work by using quantum mechanical calculations and solution chemistry method. The electronic bands near Fermi level of diaspore are almost from the O 2p orbit and the Al 3s, 3p orbit, whereas the conduction bands of kaolinite are only associated with O atom, the contribution of Al atoms in kaolinite is little. This indicates that the reactive sites in diaspore and in kaolinite are different. Adding a functional group which can be selectively chemical bonding with Al atoms in diaspore may be beneficial to the separation of diaspore from the layered aluminosilicates.The mechanisms of cationic collectors adsorbed on kaolinite and the relationship between the surfactants structures and their flotation ability are discussed by quantum chemistry, molecular dynamics simulation and the atom in molecular theory. It is showed that flotation of kaolinite using dodecylamine as collector is mainly attributed to the physical electrostatic effect and the hydrogen bonds. Increasing N atoms in collector molecule can change the charge character of its cationic group, can enlarge the electrostatic effect, and thus can improve the collecting ability for the negative charged minerals.A class of bis-quaternary ammonium salt Gemini surfactants was synthesized aiming to be used as the reverse flotation collectors for kaolinite, illite and pyrophyllite. Firstly, by using density functional method, it is proved that the novel collector is superior to the corresponding conventional quaternary ammonium salt at the electrostatic attraction. Secondly, flotation tests of the single minerals show that, in the same condition, the floatability of the three silicate minerals with Gemini as a collector reveals far better than with the corresponding traditional cationic surfactant. Due to the optimization of flotation separation process, the bauxite concentrate with Al₂O₃ of 69.07%, the Al to Si mass ratio of 9.66 was obtained. This flotation results totally fulfill the requirements of bauxite Bayer processing. At last, the adsorption character and its mechanism of the Gemini adsorbed on kaolinite are studied. A detailed understanding for the merit collecting power of the Gemini is revealed. Although the physical effect accounts for its adsorption, the special dimeric structure of the bis-quanterany ammonium salt exhibits the lower CMC, the better surface activity, and thus the stronger hydrophobic aggregation ability.