Physicochemical studies on precipitated magnesium silicates

In this study, an attempt was made to obtain highly dispersed magnesium silicates which could be employed as polymer fillers or active adsorbents. Due to numerous applications of magnesium silicates and silicates of other metals, three procedures were suggested for production of their synthetic equivalents. The precipitation processes were optimized in respect to temperature, reagent dosing rate, rate of mixing them, substrate concentration, etc. In the process of magnesium silicate precipitation 5% solutions of sodium metasilicate (water glass) and magnesium sulphate(VI) were used. In order to broaden application range of synthetic magnesium silicates they were subjected to surface hydrophobization (for the purpose non-ionic surfactants were used) and surface modification (using silane pro-adhesive compounds). All the unmodified and modified samples were subjected to a broad physicochemical analysis. Chemical composition of unmodified magnesium silicates was determined using atomic adsorption spectrometry. In addition particle diameters were estimated in all the samples. Effective particle diameter, polydispersity were defined, particle size distributions were estimated using dynamic light scattering (DLS technique). Principal adsorptive properties were established to check up whether the obtained in laboratory synthetic magnesium silicates can be applied as adsorbents. This was executed by determination of nitrogen adsorption/desorption isotherms on the surface of magnesium silicates. Moreover, taking advantage of the isotherms, specific surface area, diameter and volume of pores were estimated.