The non-linear Temkin isotherm model accounts for indirect adsorbate–adsorbate interactions on heterogeneous surfaces.
It assumes that the heat of adsorption decreases linearly with increasing coverage.
The model is given by:
$$Q = \frac{RT}{b_T} \cdot \ln(A_T \cdot C_e)$$
where \(Q\) is the amount adsorbed, \(C_e\) is the equilibrium concentration,
\(R\) is the universal gas constant, \(T\) is the temperature in Kelvin,
\(b_T\) is the Temkin constant related to adsorption heat, and \(A_T\) is the Temkin equilibrium binding constant.
This function fits the Temkin isotherm using non-linear least squares regression.