This equation is known as Freundlich adsorption isotherm or Freundlich adsorption equation. As this relationship is entirely empirical, in the case where adsorption behavior can be properly fit by isotherms with a theoretical basis, it is usually appropriate to use such isotherms instead (see for example the Langmuir and BET adsorption theories).
This equation, known as the Freundlich adsorption isotherm or equation, is based on empirical observations. When an adsorption model can be adequately represented by a theoretical isotherm, it's generally more appropriate to use that model instead of the Freundlich isotherm (see examples like the Langmuir and BET models).