Treatment of water-polluting contaminants needs significant improvement to enable the designing of a photocatalytic reactor. This work involves a TiO₂ coated catalyst film in a batch reactor, formed by dip coating on a quartz tube’s external surface, highlighting the synthesis and performance of the TiO₂ nanoparticle film. Film optimization was achieved by carrying out one to three coatings on the substrate, using different titanium isopropoxide (TTIP) (TiO₂ precursor) concentrations in isopropanol solvent (volume-by-volume ratio). Photocatalytic degradation of rhodamine B (an indicator dye) was maximum for the sample 5:100 (v/v) (having 460 nm thickness with one dip-coat), giving the highest turnover frequency of 0.342 mol/mol h^–1 among all samples. Simultaneously, diffusivity and intrinsic rate constant of the dye through the film were calculated by developing a mathematical model of diffusion and reaction. Such an experimentally validated model can provide insight into the role of composition, film thickness, and other parameters for the most effective degradation of other contaminants too.