Abstract
Calorimetric measurements have been carried out on specimens of natrolite, mesolite, and scolecite in order to assess the thermodynamic properties of a zeolite series having the same alumino-silicate framework. Low-temperature heat capacity and high-temperature enthalpy increments of natrolite and scolecite were measured by adiabatic and drop-calorimetric techniques. Standard enthalpies of formation at 298.15 K of all three zeolites were determined by solution calorimetry. Thermodynamic functions have been calculated for natrolite to 660 K and for scolecite to 470 K. The heat capacity and standard entropy at 298.15 K have been estimated for mesolite. The following values at T = 298.15 K and a pressure of 1 bar have been obtained:
| . | ΔH°f(T) . | C°p(T) . | S°(T)-S°(0) . | ΔG°f(T) . |
|---|---|---|---|---|
| . | kJ/mol . | J/(mol · K) . | J/(mol · K) . | kJ/mol . |
| natrolite | −5718.6±5.0 | 359.23±0.72 | 359.23±0.72 | −5316.6+5.0 |
| mesolite | −5947.1±5.4 | 371 ±2 | 363 ±2 | −5513.2±5.4 |
| scolecite | −6049.0±5.0 | 382.81 ±0.77 | 367.42±0.73 | −5597.9±5.0 |
| . | ΔH°f(T) . | C°p(T) . | S°(T)-S°(0) . | ΔG°f(T) . |
|---|---|---|---|---|
| . | kJ/mol . | J/(mol · K) . | J/(mol · K) . | kJ/mol . |
| natrolite | −5718.6±5.0 | 359.23±0.72 | 359.23±0.72 | −5316.6+5.0 |
| mesolite | −5947.1±5.4 | 371 ±2 | 363 ±2 | −5513.2±5.4 |
| scolecite | −6049.0±5.0 | 382.81 ±0.77 | 367.42±0.73 | −5597.9±5.0 |
Results are consistent with observed parageneses in natural occurrences.
