Purification And Modification Of Hectorite

In this dissertation, the natural hectorite minerals from certain orebody in Yusugou, Tuokexun county of Xinjiang province, China, was purified by wet-chemistry process of purification and modified by combined acid-sodium treatment. The yield, purity and viscosity of hectorite concentrate as evaluated index, the optimum process conditions were obtained by means of systematical single-factor experiments and orthogonal experiments, and the end product possessing favourable application performances was prepared.In the first place, the mineralogical and physicochemical properties of natural hectorite were tested and characterized. The results show that this sample belongs to the low grade calcium-type hectorite which could be developed and used widely thanks to several excellent physicochemical properties. And then, the sample was studied by wet-chemistry process of purification using dispersants, and the effects of the particle size, the concentration of slurry, the speed and time of mixing, the type and dosage of dispersant, as well as the time and speed of centrifugation, on purification of natural hectorite were well researched, and on this basis, the optimum purification condition was determined by using orthogonal experiments.Secondly, the structural change of hectorite during acid treatment was characterized by X-ray diffraction and Fourier transform infrared spectroscopy, and the effects of H+ on the structure of hectorite, the swelling property and the layer charge were studied. The results indicate that the layer structure of hectorite is vulnerable to acid treatment, and the hectorite modified by hydrogen ion has lower layer charge when the concentration of acid increases, and the inclusion of H+ to occupy cation vacancies within the trioctahedral sheet caused by the emigration of Mg and Fe can reduce the layer charge. The decrease of layer charge per half an unit cell in the range of 0.25~0.36 can enhance the swelling of hectorite in water. The decrease of layer charge would hamper the swelling at the layer charge of half an unit cell of <0.25.Finally, the effects of the dosage of H+ and sodium modifier, drying temperature, and the time of sodium treatment on the swelling property of hectorite were investigated, and the optimum process condition of modification was established by analyzing the data. The swelling property of the end product satisfies the commercial and practical requirement, resulting in extremely extensive application prospect.