A thermogravimetric study of thermal dehydration of copper hexacyanoferrate by means of model-free kinetic analysis

• The kinetics of thermal dehydration of K2x/3Cu[Fe(CN)6]2/3·nH2O was studied using thermogravimetry for x = 0.0 and 1.0. Data from both non-isothermal and isothermal measurements was used for model-free kinetic analysis by the Friedman and KAS methods. The water content was determined to be n = 2.9 – 3.9, with an additional ~10% of water, likely surface adsorbed, that leaves very fast when samples are exposed to a dry atmosphere. The determined activation energies are 19 kJ (mol H2O)-1 for x = 0.0 and 16 kJ (mol H2O)-1 for x = 1.0. The dehydration is adequately described as a diffusion controlled single step reaction following the D3 Jander model. The determined dehydration enthalpy is, 11 kJ (mol H2O)-1 for x = 0.0 and 27 kJ (mol H2O)-1 for x = 1.0, relative to that of water. The increase with increasing x is evidence for that the H2O molecules form bonds to the incorporated K+ ions.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

Copper hexacyanoferrate

Thermal dehydration

Thermogravimetry

Kinetic analysis

Activation energy

Dehydration enthalpy

Inorganic Chemistry

oorganisk kemi

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