## 3 Results and Discussion
### Kinetic Study of CFTX Degradation Reaction  
The quantification of electrochemical degradation processes was highlighted approaching different kinetic models. The experimental data obtained by spectrophotometric analysis were fitted according to kinetics of zero and first order reactions using the specific equations resulting from the linear diagrams obtained as A = f(t) and ln(A\({}_{0}\)/A) = f(t), respectively, where A\({}_{0}\) and A represent the absorbance values at initial time and at the well-determined moment \"t\". Practically, the slopes of the straight lines represent the rate constants (k) of reactions. To better explain the application of kinetics, it is necessary to show the equations that express the variation of the CFTX concentration, noted further as [CFTX], over time, for each of the kinetics. The Equations (14) and (15) reveal the variation of CFTX concentration in time, for the kinetics of zero and first-order reactions. \[-\frac{\mathrm{d}[\mathrm{CFTX}]}{\mathrm{dt}}=\mathrm{k} \tag{14}\]  
\[-\frac{\mathrm{d}[\mathrm{CFTX}]}{\mathrm{dt}}=\mathrm{k}[\mathrm{CFTX}] \tag{15}\]  
Since the absorbance is directly proportional to the CFTX concentration, Equations (14) and (15) can be written as follows (Equations (16) and (17)):  
\[-\frac{\mathrm{d}\mathrm{A}}{\mathrm{dt}}=\mathrm{k} \tag{16}\]  
\[-\frac{\mathrm{d}\mathrm{A}}{\mathrm{dt}}=\mathrm{k}\mathrm{A} \tag{17}\]  
Consequently, by integrating the last two expressions, the rate equations corresponding to the kinetics of zero and first order reactions are obtained (Equations (18) and (19)). \[\mathrm{A}=\mathrm{A}_{0}-\mathrm{kt} \tag{18}\]  
\[\mathrm{ln}\,\frac{\mathrm{A}_{0}}{\mathrm{A}}=\mathrm{kt} \tag{19}\]  
where t represents the time (minutes) and k is the reaction rate constant. Thus, for zero-order reactions the absorbance varies in the same way, according to the Equation (18). Contrary, for the first-order reactions the absorbance presents an exponential drop (Equation (20)). \[\mathrm{A}=\mathrm{A}_{0}\mathrm{e}^{-\mathrm{kt}} \tag{20}\]  
Consequently, (i) for the reactions respecting a zero-order kinetics, by plotting A = f(t), a straight line will be obtained whose slope (dA/dt) is equal to the rate constant (k), and the intersection with the ordinate represents the initial absorbance (A\({}_{0}\)); (ii) for first order kinetics, the graph ln(A\({}_{0}\)/A) = f(t) represents a straight line with a slope equal to k, and the graph A = f(t) shows the exponential tendency of the absorbance (Equation (20)). In order to approach the kinetic model related to the CFTX decomposition reaction, the experimental data obtained in the presence of F\({}^{-}\), Cl\({}^{-}\) and Br\({}^{-}\) ions were collected. As observed from Figure 4a, in the presence of I\({}^{-}\) ions, the spontaneous interferences and/or interactions between CFTX and I\({}^{-}\) species with spectrophotometric response at 290 nm occur (Figure 4a), being clearly visible for the 0.1 mol L\({}^{-1}\) NaI solution. For dilute NaI solutions (0.01 mol L\({}^{-1}\) and 0.001 mol L\({}^{-1}\)), a much-attenuated response is highlighted,that alters the wavelength of absorbance maximum (detail from Figure 4b), but which does not exclude the appearance of interferences that affect the spectral characteristics of CFTX. As can be seen from Figure 4a, in the presence of dilute NaI solutions the interferences are slightly weaker, registering a maximum absorption like a shoulder, which follows a descending trend, affecting the baseline to the same extent as in the case of 0.1 mol L\({}^{-1}\) NaI solution. Thus, the extension of the experiments for dilute NaI solutions would lead to similar results to those were presented in the previous paragraphs, for the 0.1 mol L\({}^{-1}\) NaI solution. Thus, in this case the approach of a kinetic model is improper. Kinetic data are comparatively presented to those obtained for CFTX degradation in an inert supporting electrolyte, such as sodium sulfate.