## 3 Results and Discussion  
### Electrochemical Behavior of CFTX in the Presence of Different Ions  
3.1.1. Study by Cyclic voltammetry (CV)  
The CFTX electrochemical behavior depends on the specific interactions of the antibiotic molecules with halides as well as with the electrogenerated species during anodic potential scanning. The electrocatalytic effect of platinum electrode (Pt) on the CFTX electrochemical degradation was also identified. Figure 1 displays the cyclic voltammograms obtained on Pt electrode in the support electrolyte solution containing 0.1 mol\(\cdot\)L\({}^{-1}\) NaX (X = F\({}^{-}\), Cl\({}^{-}\), Br\({}^{-}\), I\({}^{-}\)), in the absence and in the presence of 0.025 g\(\cdot\)L\({}^{-1}\) CFTX. For the supporting electrolyte solution containing F\({}^{-}\) (Figure 1a), on the anodic scan a small peak at \(-\)0.8 V can be observed which corresponds to platinum hydroxide/oxyhydroxoxide formation and their adsorption on electrode surface [33; 34; 35], reactions (1), (2) and (3). \[\mathrm{Pt+H_{2}O\leftrightarrow Pt(OH)+H^{+}+e^{-}} \tag{1}\]  
\[\mathrm{Pt+2H_{2}O\leftrightarrow Pt(OH)_{2}+2H^{+}+2e^{-}} \tag{2}\]  
\[\mathrm{Pt+3H_{2}O\leftrightarrow PtO(OH)_{2}+4H^{+}+4e^{-}} \tag{3}\]At higher potential values, between 1.0 and 1.8 V, the platinum oxides are formed and adsorbed on the platinum electrode surface (reactions (4)-(9)) followed by oxygen evolution (10) [35; 36; 37; 38; 39]. \[\text{Pt(OH)}\leftrightarrow\text{PO}+\text{H}^{+}+\text{e}^{-} \tag{4}\]  
\[\text{Pt}+\text{H}_{2}\text{O}\leftrightarrow\text{PO}+2\text{H}^{+}+2\text{e}^ {-} \tag{5}\]  
\[\text{Pt}+2\text{H}_{2}\text{O}\leftrightarrow\text{PtO}_{2}+4\text{H}^{+}+4 \text{e}^{-} \tag{6}\]  
\[\text{Pt}+\text{O}_{2}+\text{H}^{+}+\text{e}\leftrightarrow\text{PtO}(\text{ OH})\leftrightarrow\text{PtO}+\text{H}^{+}+\text{e}^{-} \tag{7}\]  
\[\text{Pt}+\text{H}_{2}\text{O}\leftrightarrow\text{Pt}(\text{OH})+\text{H}^{+}+ \text{e}^{-} \tag{8}\]  
\[\text{Pt}(\text{OH})\leftrightarrow\text{PtO}+\text{H}^{+}+\text{e}^{-} \tag{9}\]  
\[2\text{PtO}\leftrightarrow 2\text{Pt}+\text{O}_{2} \tag{10}\]  
Fluoride ions are electrochemically inert, and consequently the cathodic peaks correspond to platinum oxide reduction, oxygen reduction and hydrogen evolution (reactions (11), (12) and (13)) [35; 36; 37; 38; 39]. \[\mathrm{Pt+2H_{2}O\leftrightarrow Pt(OH)_{2}+2H^{+}+2e^{-}} \tag{2}\]0  
\[\mathrm{Pt+2H_{2}O\leftrightarrow Pt(OH)_{2}+2H^{+}+2e^{-}} \tag{2}\]1  
\[\mathrm{Pt+2H_{2}O\leftrightarrow Pt(OH)_{2}+2H^{+}+2e^{-}} \tag{2}\]2  
In the presence of CFTX, the two anodic peaks were suppressed; the oxygen evolution reaction is reduced while that of hydrogen is accelerated and, consequently, the current density following the same trend. On the other hand, the addition of CFTX in the NaF solution leads to a narrower hysteresis and located in lower current areas compared to that  
\[\mathrm{Pt+2H_{2}O\leftrightarrow Pt(OH)_{2}+2H^{+}+2e^{-}} \tag{2}\]3 Cyclic voltammograms recorded on platinum electrode in blank support electrolytes and support electrolytes containing 0.025 g\(\cdot\)L\({}^{-1}\) CFTX with a potential scan rate of 100 mV\(\cdot\)s\({}^{-1}\): (**a**) 0.1 mol\(\cdot\)L\({}^{-1}\) NaF solution without and with CFTX; (**b**) 0.1 mol\(\cdot\)L\({}^{-1}\) NaCl solution without and with CFTX; (**c**) 0.1 mol\(\cdot\)L\({}^{-1}\) NaBr solution without and with CFTX; (**d**) 0.1 mol\(\cdot\)L\({}^{-1}\) NaI solution without and with CFTX. obtained in its absence. Also, the anodic path overlaps the cathode one, in the potential range between \(-\)1.0 V and 1.0 V, suggesting that the oxidation/reduction processes at the electrode/electrolyte interface are much restricted due to CFTX adsorption on the platinum surface. Figure 1b shows cyclic voltammograms of the platinum electrode in 0.1 mol-L\({}^{-1}\) NaCl solution without and with 0.025 g:L\({}^{-1}\) CFTX.