A Thermodynamic Study of the Zeolite Stilbite

Author

David Adams Howell

Date of Award

8-1987

Degree Name

Master of Science

Department

Geological and Environmental Sciences

First Advisor

Dr. John D. Grace

Second Advisor

Dr. Robert Hunt Anderson

Access Setting

Masters Thesis-Open Access

Abstract

Stilbite is a calcium-rich zeolite found in low-grade metamorphic and hydrothermally altered environments. In this study, measurements of the enthalpy of formation at 298.15 K, heat capacity from 5 to 350 K, and enthalpy increments horn 350 to 500 K were performed on a specimen of stilbite characterized by electron microprobe analysis. The actual formula of the stilbite is: Ca_1.019Na_0.136K_0.006Al_2.180Si_6.820O₁₆ . 7.33H₂O. Evaluation of the thermodynamic properties for stilbite at T = 298.15 K produced the following values: Δ_rH^Om(T)= -11034.6+6.6 kJ . mol^-1, C^Op,m(T)=808.73+1.62 J.K^-1, S^Om(T)-S^Om(0)=805.54+1.61 J.K^-1.mol^-1,Δ_fS^om(T)= -2990.44+1.86 J.K^-1, mol^-1, and ΔfG^om(T)= -10143.0+6.6 kJ.mol-1. Comparison of the calorimetrically derived value for the Gibbs free energy of formation, ΔfG^om, of stilbite with that calculated from an estimation method (La Iglesia and Anzar, 1986) shows a difference of 49 kJ.mol^-1. An attem pt was made to retrieve a consistent Gibbs free energy value for laumontite using available phase equilbria and calorimetric data for heulandite and stilbite.

Recommended Citation

Howell, David Adams, "A Thermodynamic Study of the Zeolite Stilbite" (1987). Masters Theses. 1263.
https://scholarworks.wmich.edu/masters_theses/1263