Low-temperature thermodynamic properties of disordered zeolites of the natrolite group

Pressure-induced stabilization of ordered paranatrolite: A new insight into the paranatrolite controversy

“…They speculated that natrolite II is an "overhydrated" analog of natrolite with a structure similar to that of paranatrolite (Belitsky et al 1992). Subsequently, Paukov et al (2002) * E-mail: yollee@bnl.gov proposed that Al/Si disordering has little effect on the thermodynamic properties of natrolite group zeolites.…”

Quasi-ice-like CP behavior of molecular H2O in hemimorphite Zn4Si2O7(OH)2{middle dot}H2O: CP and entropy of confined H2O in microporous silicates

“…Comprehensive understanding of the thermodynamic behavior of confined H 2 O in micro/nanoporous minerals is lacking, whereas data exist for specific zeolites (e.g., Johnson et al 1982Johnson et al , 1983Johnson et al , 1985Johnson et al , 1992Paukov et al 2002). Several attempts have been made to estimate or calculate S values for H 2 O in microporous silicates.…”

“…Because hydrogen bonding associated with confined H 2 O is a relatively weak force in most silicates, it will express itself in C P at low temperatures. Calorimetric work has been undertaken for several natural zeolites (e.g., Johnson et al 1982Johnson et al , 1983Johnson et al , 1985Johnson et al , 1992Paukov et al 2002) and these studies show that the C P contribution and the entropy, S, at 298 K of H 2 O in zeolites are variable. In spite of this reported variability, thermodynamic studies (e.g., Helgeson et al 1978;Robinson and Haas 1983;Van Hinsberg et al 2005) have proposed "standard values" of S for confined H 2 O in a variety of microporous silicates for use in calculations and databases.…”

Molecular H2O in armenite, BaCa2Al6Si9O30·2H2O, and epididymite, Na2Be2Si6O15·H2O: Heat capacity, entropy and local-bonding behavior of confined H2O in microporous silicates

“…Much and varied types of research have been done on them (Breck, 1974;Bish and Ming, 2001). In terms of thermodynamic behavior, because hydrogen-bonding associated with confined H 2 O is generally a relatively weak force, it expresses itself predominantly in C p behavior at low temperatures -at T < 300 K. There has been calorimetric C p work done in this direction on a number of natural zeolites (e.g., Johnson et al, 1982Johnson et al, , 1983Johnson et al, , 1985Johnson et al, , 1992Paukov et al, 2002). However, C p investigations at T < 300 K on the behavior of H 2 O in other types of silicates have only recently started (Paukov et al, 2007;Geiger and Dachs, 2009).…”