Properties of low-modulus sodium silicate solution in alkali system
(School of Metallurgy and Environment, Central South University, Changsha 410083, China)
Abstract: The properties of low-modulus (m≤1) sodium silicate and pre-desilication solutions in alkali systems were studied by measuring their electrical conductivity, viscosity, and surface tension. The results show that the property of high concentration pre-desilication solution is similar to that of sodium silicate solution. The electrical conductivity of sodium silicate solution increases with increasing the temperature and silica concentration but decreases with increasing the modulus. Further, the viscosity of the solution increases with increasing the silica concentration and linearly decreases with increasing the temperature, whereas its surface tension gradually decreases with increasing silica concentration and temperature, indicating that the sodium silicate solution is an oligomer with strong surface activity. At room temperature, the electrical conductivity and surface tension of sodium silicate solution are higher than those of pre-desilication solution, whereas its viscosity is smaller than that of pre-desilication solution. A turning point exists at a silica concentration of 44.7 g/L. When the silica concentration is less than 44.7 g/L, the ionic structure of the solution is dominated by monomeric silicate ions. In contrast, when the silica concentration changes from 44.7 to 50 g/L, the migration number of silicate anions significantly decreases.
Key words: sodium silicate solution; electrical conductivity; viscosity; surface tension