Thermal Study of Types of Water Associated with Clinoptilolite

Abstract

Abstract--The identification and quantification of the water associated with powdered clinoptilolite and clinoptilolite-bearing tufts were made using thermogravimetric, vacuum gravimetric, and differential scanning calorimetric techniques. Inflection points on thermogravimetric curves at approximately 80 ~ and 170~ correspond to changes in the proportions of externally adsorbed water to loosely bound zeolitic water and loosely bound zeolitic water to tightly bound zeolitic water, respectively. These three types of water can be differentiated by temperatures and heats of dehydration obtained from differential scanning calorimetry. These temperatures and heats of hydration are 75 _+ 10~ and 59.2 _ 5.9 kJ/mole H20, 171 _+ 2~ and 58.7 _+ 6.1 kJ/mole H20, and 271 +_ 4~ and 78.7 _+ 7.0 kJ/mole HzO for external water, loosely bound water, and tightly bound water, respectively. The ratio of loosely bound zeolitic water to tightly bound zeolitic water determined in this study is similar to that reported in the literature from structural determinations, indicating that the desorption properties of clinoptilolite are determined by the specific positions of the water molecules in the structure.

Adsorption of dimethyl ether (DME) on zeolite molecular sieves

“…In the temperature range of >200 °C, both adsorbents show negligible mass losses, thus indicating reasonable thermal stability at elevated temperature. This is in agreement with the results of Knowlton and White [28] where it was reported that there are at least three types of water present in zeolites: crystal water, loosely bound water and tightly held water. The first two were reported to be easily removed within the temperature range of 50-200 °C.…”

Untitled

“…4 were integrated to find the energy required for this process. 158-336 J/g energy was absorbed as reported in Table 1, due to mainly evaporation of free water and slightly bound water [15] or water in the mesopores of the fibers [16].…”

Characterization and Dehydration Behavior of a Natural, Ammonium Hydroxide, and Thermally Treated Zeolitic Tuff

“…In order to distinguish the different types of water present in the zeolites, the TG curves were analyzed according to the procedure outlined in the literature. [2] The low-temperature inflection point was observed at around 100 C for NZ. The rapid weight loss up to this temperature (4.4% w=w) was due to desorption of the externally adsorbed water.…”

“…Dehydration behaviors of clinoptilolite have been investigated by various analytical techniques including thermogravimetry (TG), differential thermogravimetry (DTG), differential thermal analysis (DTA), differential scanning calorimetry (DSC), [1][2][3][4][5][6][7][8] infrared spectroscopy, [9] and single-crystal X-ray diffraction, [10] and different types of water were identified in clinoptilolite.…”

“…[8] Thermal and vacuum dehydration analysis of clinoptilolite-rich tuffs by DSC revealed the presence of three types of water as externally adsorbed, loosely bound zeolite, and tightly bound zeolite water and the heats of dehydration of each type of water were calculated as 54.4-65.8, 52.3-64.5, and 76.2-160 kJ=mol H 2 O, respectively. [2] Adsorption and desorption of water vapor on zeolites are reversible, i.e., the amount of heat required for desorption is equal to that released during adsorption. The application of zeolite for water adsorption is widely investigated for many purposes.…”