The photodegradation experiments of a dye, reactive black 5 (C.I. 20505), were performed in batch- and continuous-flow-type reactors using TiO₂-immobilized glass tubes to investigate the effects of the TiO₂ film thickness, pH, feed rate, and aeration on the removal efficiency in the presence of both ferric ion and H₂O₂. The photocatalytic reaction with respect to the initial concentration can be explained by a reaction rate having an apparent first-order equation. The rate constant (K) increased with increasing TiO₂ film thickness up to 5.29 μm, which we obtained by dip coating three times. The rate constants at pH 3.5 were 0.19, 0.27, 0.50, and 0.32 /h, for films that had seen coated once, twice, three times, and four times, respectively. The photodegradation rate of reactive black 5 dye was 0.33 /h higher at pH 3 (0.33 /h) than at pH 9 (0.20 /h). The rate constants were 0.27, 032, 0.28, and 0.28 at feed rates of 60, 120, 180, and 240 mL/min, respectively. The rate at 120 mL/min was higher than those at the other feed rates, because the photodegradation capability decreased as a result of a wash-out effect overriding an optimal feed rate. Rate constants increased from 0.26 to 0.27, 0.29, and 0.31 /h as the air flow rate increased from 1, to 3, 5, and 10 mL/min, respectively.