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Table 2 Isotherm models used to describe the sorption behaviour of babool gum

From: Moisture sorption characteristics and modelling of babool (Acacia nilotica) gum

Isotherm model Mathematical expression References
GAB (Guggenheim–Anderson–de Boer) \(M = \frac{{M_{o} CKa_{{\text{w}}} }}{{\left( {1 - Ka_{{\text{w}}} } \right)\left( {1 - Ka_{{\text{w}}} + CKa_{{\text{w}}} } \right)}}\) Quirijns et al. (2005)
Hasley \(a_{{\text{w}}} = \exp \left( {\frac{ - a}{{M^{b} }}} \right)\) Hasley (1948)
Iglesias and Chirife \(M = a + b\left( {\frac{{a_{{\text{w}}} }}{{1 - a_{{\text{w}}} }}} \right)\) Iglesias and Chirife (1982)
Caurie \(M = \exp \left( {a + ba_{{\text{w}}} } \right)\) Caurie (1970)
BET (Brunauer–Emmett–Teller) \(M = \frac{{CM_{{oa_{{\text{w}}} }} }}{{\left[ {\left( {1 - a_{{\text{w}}} } \right) + \left( {C - 1} \right)\left( {1 - a_{{\text{w}}} } \right)a_{{\text{w}}} } \right]}}\) Brunauer et al. (1938)
  1. M-EMC, % db, aw water activity, a and b constants, Mo monolayer moisture, % db, C Guggenheim constant, and k constant related to total heat of sorption of multilayer