## 2 Materials and Methods
### Dark Adsorption Experiments  
Dark adsorption experiments were performed under same conditions with photocatalytic degradation experiments but without putting into operation the UV lamp of the photocatalytic reactor (without UV radiation) and without addition of hydrogen peroxide. In this respect, a UV photocatalytic reactor with photocatalytic membrane was used in which the working solution was continually recirculated through a recirculation vessel by means of an external centrifugal pump. The photocatalytic reactor is designed so that the UV lamp, the photocatalytic membrane, and the water-cooling jacket are coaxially positioned inside it. The characteristics and operating parameters of the photocatalytic reactor are presented in Table 1.  
In the case of experiments on adsorption isotherms, working solutions were prepared with the initial COD equivalent concentration of 2,4-DCF ranging from 50 to 300 mg O2/L. It should be mentioned that because in photocatalytic experiments it is more useful to report the content in organic substrate in terms of organic carbon (OC), throughout this work the content in organic substrate is expressed exclusively in terms of organic carbon. Thus, for adsorption isotherms experiments the organic carbon equivalent initial concentrations of 2,4-DCF solutions ranged from 18.75 to 112.50 mg OC/L. After the solutions were prepared, their pH was adjusted to the default values (pH of 2, 3, 5, and 7). Next, each working solution was introduced in the photocatalytic reactor, and by means of the external centrifugal pump these were recirculated at room temperature until the equilibrium concentration was reached. The samples by which the adsorption equilibrium was checked were taken from the photocatalytic reactor by means of its special sampling holes without the need to turn it off. Next, the samples were prepared and measured for their organic content by COD analysis following the APHA 5220 D standard method [26]. Both LT 200 thermostat and DR 3800 spectrophotometer (Hach Lange GmbH, Weinheim, Germany) were used to carry out the analysis. Regeneration of the photocatalytic membrane was accomplished by operating the reactor charged with distilled water to which oxygen peroxide was added for two hours in the presence of UV radiation. The regeneration procedure was applied \begin{table}
\begin{tabular}{l c} Reactor Volume, L & 1.5 \\
2,4-DCF working solution volume, L & 2 \\ Recirculation flow rate, L/min & 1 \\ UV lamp & High-pressure mercury lamp; power: 120 W; wavelength peak: 365 nm; peak irradiance (intensity): 1.5 mW/cm\({}^{2}\); energy density (dose for 2 h of irradiance): 10.8 J/cm\({}^{2}\) \\
2,4-DCF working solution pH & 2, 3, 5, and 7 \\ Hydrogen peroxide/2,4-DCF molar ratio & 0.5, 1, and 2 \\ Membrane & TiO2/stainless steel \\ \end{tabular}
\end{table} 
Table 1: Photocatalytic experimental conditions. after each experiment. The amount of 2,4-DCF adsorbed on the photocatalytic membrane was established based on Equation (1). \[\mathrm{q_{eq}}=\frac{\left(\mathrm{C_{0}-C_{eq}}\right)\mathrm{V}}{\mathrm{m}} \tag{1}\]  
where \(\mathrm{q_{eq}}\) is the amount of 2,4-DCF adsorbed on the photocatalytic membrane at equilibrium (mg/g), V is the volume of the working solution (L), C0 and Ceq are the initial and equilibrium concentration of 2,4-DCF (mg/L), and m is the mass of the photocatalytic membrane (g). The adsorption isotherms were plotted in terms of the amount of 2,4-DCF adsorbed (expressed as organic carbon) on the photocatalytic membrane \(\mathrm{q_{eq}}\) (mg/g) against of equilibrium concentration of 2,4-DCF \(\mathrm{C_{eq}}\) (mg/L). The experiments on adsorption kinetics were performed in the same way as those on adsorption isotherms. For these experiments, working solutions were prepared with initial COD equivalent concentration of 2,4-DCF of 100, 200, and 300 mg O2/L. Thus, the organic carbon equivalent initial concentrations of 2,4-DCF solutions were 37.50, 75.00, and 112.50 mg OC/L.