Question

Which model does not approve the existence of the stagnant layer in the solid-liquid interface?

(a) Interfacial barrier model

(b) Diffusion layer model

(c) Penetration or surface renewal theory

(d) Danckwert’s model

I have been asked this question during an online exam.

My doubt stems from Physicochemical Factors Affecting Drug Absorption in division Absorption of Drugs of Drug Biotechnology

Answer 1

Correct choice is (d) Danckwert’s model

For explanation: Danckwert did not approve the existence of the stagnant layer and suggested that turbulence in the dissolution medium exists at the solid/liquid interface. Due to which the agitated fluid consists of a macroscopic mass of eddies or packets reach the solid-liquid interface due to the eddy currents, absorb the solute by diffusion and carry it to the bulk of the solution.