The Synthesis Of Saponite And Its Rheological Research

Saponite has largely been studied due to its excellent dispersibility,surface acidity,thermal stability,adsorption property,high specific surface area and other physico-chemical properties.It has been widely used in catalysis,textile,pharmaceutical and other industries.Its application is often limited due to the presence of impurities and it is difficult for purification.The synthesis of saponite has been attracted great interest of researchers at home and abroad.In this paper,saponites with stoichiometric mixture of silica,aluminum chloride and magnesium chloride were synthesized using hydrothermal method.The influence of Mg/Al ratios,reaction time,temperature and the initial slurry pH on the structure and crystallization of saponite was investigated.The synthetic saponites were characterized by power X-ray diffraction(XRD),thermogravimetry derivative-thermogravimetry(TG-DTG),Fourier transformed infrared spectroscopy(FT-IR).It was found that the increase of Mg/Al ratios caused the more by-products.Saponite was formed rapidly within 6 h and higher temperature(200℃)facilitated the crystallization of saponite.The initial slurry pH was one of the great factors influencing the crystallization and structure.The pH at 9 and 10 favoured the ordering in the stacking direction.A series of saponites with different layer charges were synthesized by adjusting Si/Al ratios and their rheological properties were studied.Based on the different layer charge,here we investigate the structure,hydration swelling,morphology,thermal behavior and the rheological properties of saponite in aqueous solution.It was shown that the higher layer charge led to the lower layer space of synthetic saponites and the lower hydration capacity according to the XRD and TG analysis.FT-IR spectroscopy suggested that the element Al substituted tetrahedral Si forming Si–O–Al linkages.As for the particle size distribution,the high layer charge of saponite had higher average particle size in aqueous solution.The SEM images revealed that with decreasing the layer charge,the aggregation converted from an edge-to-face to a face-to-face orientation.For the rhetorical research,it was found that the viscosity of saponite suspension decreased rapidly with increasing of shear rate.The saponite suspensions are excellent shear-thinning fluids.In addition,the lower layer charge had the higher viscosity.Sodium polyacrylates influences the dispersion and rheological properties of saponite suspensions.Zeta potential decreased with the addition of sodium polyacrylates and a significant decrease of viscosity value was observed at the same time.