(a)
(b)
Figure 8: (a) Photodegradation of different carboxylic acids in the presence of TiO2-0.02CdS composite under visible light irradiation. Curves correspond to the best nonlinear least square fitting of monoexponential functions to experimental data. Error bars are associated with the fitted curves and do not exceed ±8%; (b) characteristic times (τ) that best describe the photodegradation kinetics.