The influence of hydrothermal synthesis conditions on gyrolite texture and specific surface area

Abstract

Influence of hydrothermal synthesis conditions on the gyrolite specific surface area, dominant pore size and their differential distribution by the radius were determined. The synthesis of gyrolite has been carried out in unstirred suspensions within 32, 48, 72, 120, 168 h at 200°C temperature from a stoichiometric composition (the molar ratio of CaO/SiO2 was equal to 0.66 where water/solid ratio of the suspension was equal to 10.0) of the initial CaO and SiO2·nH2O mixture. It was found that the structure of gyrolite and the shape of dominated pores (from pores between parallel plates to cylindrical pores) changes prolonging the duration of hydrothermal synthesis. The stable gyrolite crystal lattice was formed only after 120 h of isothermal curing. Its specific surface area S BET = 38.28 m2/g, the radius of dominant plate pores r p = 30–40 A, the cumulative pore volume ΣV p = 0.08 cm3/g. It was determined that the pores with 4.0–5.0 nm radius were dominated in gyrolite structure after 168 h of synthesis. It was estimated that the ion exchange between gyrolite with less orderly structure in Zn(NO3)2 + NH4OH alkaline solution (\({c_{{{\text{Zn}}^{2+}}}}\)—0.3 g/dm3) proceeds more faster and effectively.