Crystal Structure And Surface Property Of Diaspore And Phyllosilicate Minerals

In this work, the studies relating to the crystal structure, chemical composition wettability, electrokinetics and floatability of diaspore and dioctahedral phyllosilicates as well as the mechanisms of their interactions with flotation reagents were carried out. It was based on mineralogy, crystal chemistry, surface chemistry and flotation theory, with the help of the zeta potential measurement, contact angle measurement, flotation test, polar microscope, scanning electron microscope, X-ray diffraction, infrared spectroscopy and atomic force microscope.The number of the broken bonds per unit area for different crystal planes of kaolinite, pyrophyllite and illite, which was calculated by crystal chemistry of the minerals, is in the order of Nsi-O(110)= illite > pyrophyllite, the same with the order of hydrophilicity. The results were approximately consistent with the measured value of contact angles.The wettability of minerals is interpreted in the absence and presence of collectors.Among the three crystal planes in diaspore, the number of Al-O broken bond per unit area in the crystal plane subject to the following order: NAMXOOI) > NAI-OOOO) > NAI-O(OIO)- The molecule kinetics method was employed to simulate the adsorption of the collectors on diaspore. Adsorptive energy and adsorptive capacity of the collectors on the various surfaces of diaspore were in the order of (010)>(100)>(001). The atomic force microscope (AFM) was used to measure the adhesional energy per area and surface force on the diaspore interface in the absence and presence of collector (sodium oleate). The results were approximately consistent with the measured value of contact angles. It showed that diaspore was turned from high energy surface to low energy surface after interacting with collectors.With the help of infrared spectroscopy, it is known that the linkage between dodecylamine (cationic collector) and sodium oleate (anionic collector) and diaspore, kaolinite, illite and pyrophyllite is fundamentally electrostatic forces, which contributes to physical adsorption. The adsorption is related with surface electric property of minerals.The effect of chemical composition of diaspores on their electrokinetics was investigated. Increasing Si2 content in a diaspore sample was found to decrease its iso-electric point (iep). A linearcorrelation appeared to exist between the measured iso-electric point and alumina to silica mass ratio in diaspore samples. A empirical equation of iep for diaspore was conducted below: zep(cal),- = -20.3xSiO2(wt%) + 7.74xAl2O3(wt%)+18.8xTiO2(wt%). The structure layer turns from TOa type to TOaT type ( balanced by interlamellar cations ) , then to TOaT type for kaolinite , illite and pyrophyllite, respectively; alumina to silica mass ratio turns from 0.86 to 0.42; the surface zeta potentials turn small, but they show little relation with their surface charge density. The decreasing order of the measured iep or calculated pzc from kaolinite to illite, and then to pyrophyllite correlated well with that of the number of broken Al-O bonds and the ratio of broken Al-O to Si-O bonds. The calculated point of zero charge (pzc} of edge plane is in the order of kaolinite (7.76) > illite (6.84) > pyrophyllite (6.26).The surface zeta potential variation of hard kaolin as a function of pH was almost the same as that of soft kaolin. The iep of hard kaolin varied from 2.5 to 3.8. SiO2(wt%) of the severa...