Evaluation of the adsorption and rate constants of a photocatalytic degradation by means of HS-MCR-ALS. Study of process variables using experimental design

The effect of the catalyst type, the catalyst concentration and the pH on the global rate of the photocatalytic degradation of C.I. Acid Yellow 9 was studied. Adsorption and rate constants related to the physical adsorption on the catalyst surface and the degradation of the dye upon illumination were calculated by applying hybrid hard- and soft-multivariate curve resolution alternating least squares (HS-MCR-ALS), including the Langmuir–Hinshelwood kinetic model as hard restriction, to the UV–visible spectra recorded during the photocatalytic degradation process. The influence of the variables on the degradation rate was assessed using the experimental results obtained from a full factorial 23 experimental design. Physical adsorption was more relevant when TiO2 was employed as a catalyst. The global rate of the photocatalytic degradation of the dye was found to be closely related to the catalyst type, its concentration level and the interaction between both factors. pH was only found to be relevant when TiO2 was used. The photodegradation of C.I. Acid Yellow 9 was optimal when using high concentrations of ZnO as catalyst.

► Study of the heterogeneous photocatalytic degradation of Acid Yellow 9.
► Simultaneous evaluation of the adsorption and rate constants.
► Analysis by HS-MCR-ALS of the obtained UV–visible data.
► Langmuir–Hinshelwood model is included in HS-MCR-ALS as a hard restriction.
► Influence of pH, catalyst type and concentration is assessed by experimental design.