Question

how to distinguish between adsorption and degradation of dyes

Answer 1

Adsorption and degradation of dyes are an important factors (synergetic mostly) in the removal of dye molecules. Adsorption of a dye mainly involves attachment of dye molecules to your catalyst through electrostatic forces, hydrophobic hydrophilic interactions, Vander walls interactions. However, degradation refers to mineralization of dye molecules, the ideal products being water and CO2. You must do the adsorption process in the dark until you observe no change in the concentration of the dye (check the UV-Vis absorbance of the dye’s characteristic peak.). After the adsorption-desorption equilibrium is achieved, you can perform the light reaction.You need to set up a control experiment in the dark too. I suggest you can look on previous works. Extensive work has been done in this area.