Effect Of Calcination On Purification Of Quartz Flotation

Thermal comminution has been applied in quartz purification more and more widely in recent years with its lower energy consumption, not easy to mix impurities and product size well-distributed. After high temperature calcination and water quenching, the structure of quartz becomes loose and can be grinded to the required fineness easily, which is ready for the further purification. As the conventional mechanical grinding, two methods, which are acid leaching and flotation, are used to purify quartz for the high temperature calcination grinding product. The effects of calcination on acid leaching have been studied by some domestic scholars, while the influences on flotation purification have been investigated seldom in the past years. Particularly, the research of the impact on the separation of calcined quartz and feldspar which is the main impurity mineral is also a blank.Therefore, the flotation tests for pure quartz?pure feldspar and its artificial mixed minerals with different types of collectors and regulators were carried out in this paper in order to explore the effects of calcination on quartz and feldspar separation. The mechanism of the effects of calcination on separation of quartz and feldspar were studied by means of Zeta potential, differential thermal analysis and other detection methods. Finally, flotation tests for the actual ore taken from two different habitats were conducted to purify the quartzThe results of flotation experiments for pure minerals with three different types of collectors showed that the index of flotation were perfect using the collector mixed with cationic collector and Anionic collector to separate the quartz and feldspar both before and after calcination. The floatability of quartz and feldspar after calcination were changed, also the changes of floatability existed differences in the different collector systems.The floatation tests for regulators indicated that feldspar could be activated by sodium fluorosilicate which had little impact on quartz before calcination when dosage of sodium fluorosilicate was lower, so as to enlarge the flotation differences between quartz and feldspar. After calcination, quartz can be inhibited by smaller dosage of sodium hexametaphosphate which had an unapparent effect on feldspar, which could also expand the flotation differences between quartz and feldspar.Artificial mixed mineral flotation tests showed that the quartz and feldspar after calcination could be separated effectively when sodium dodecyl sulfate and dodecylamine used as the collector, sodium hexametaphosphate used as the regulator. The feldspar which was impurity could be separated from calcined feldspathic quartz ore using flotation methods at appropriate conditions. However, in order to obtain a better flotation index, it was necessary for a specific ore to control the reasonable dosage of regulator according to the ore properties.The macro and micro morphology analysis of quartz before and after calcination evinced that the internal micro cracks of quartz ore increased after calcination. From the perspective of bond energy, the fracture probability of Al-O bond was increased, leading more Al atom exposed to the cleavage surface and the chance of impurity exposed was also increased, finally resulting in the increase of active sites on feldspar surface. Zeta potential measurements showed that the point of zero charge of quartz and feldspar after calcination decreased, and the feldspar reduced sharper.Flotation tests for two kinds of quartz minerals taken from Inner Mongolia Ulanhot and West Ujimqin demonstrated that, with the aluminosilicate minerals as the main impurities, the quartz ore could be purified effectively by flotation whether before and after calcination. Ulanhot quartz ore was a kind of easy processing ore. For the run-of mine ore with SiO2 97.45%, using the process of grinding, desliming, high intensity magnetic separation, and reverse flotation, the concentrate with SiO2 99.93% and concentrate yield 62% was obtained for original ore and the concentrate with SiO2 grade 99.80%, concentrate yield 53.48% was obtained for calcined ore. The Al2O3 removal rate reached 99.03% and 95.72% before and after calcination respectively. For the West Ujimqin quartz ore, it was a refractory quartz ore, after the process of grinding, high intensity magnetic separation, and flotation, for the run-of mine ore with SiO2 98.80%, the concentrate with SiO2 99.60% and concentrate yield 54.55% was obtained for original ore and the concentrate with SiO2 grade 99.44%, concentrate yield 45.25% was obtained for calcined ore. The Al2O3 removal rate reached 99.03% and 95.72% before and after calcination respectively. Therefore, it was elucidated that the impurity aluminum in West Ujimqin quartz ore belonged to structural impurity and was encased in the quartz crystal, which resulting in its difficulty removal with conventional beneficiation methods.