The Elovich isotherm equation: Back to the roots and new developments

•The history of the Elovich adsorption isotherm is retrieved•Elovich compares to Langmuir or Freundlich in data fitting, despite previous results.•Although nonlinear regression is recommended, linear regression can fit q vs. C data.•The nonlinear Elovich equation can be expressed in terms of the Lambert W function.•An extended form (Langmuir-Elovich) is proposed for computing energy distributions.