# A Sustainable Electrochemical-Based Solution for Removing Acetamiprid from Water
## 3 Results
### Influence of Different \(j\) on the EO of ACT  
The study of the effect of \(j\) on ACT removal at the TiO\({}_{2}\)-RuO\({}_{2}\)-IrO\({}_{2}\) electrode as a function of electrolysis time was accompanied by the decay of the absorption bands (Figure 2a 30, Figure 2b 60, Figure 2c 90, and Figure 2d 120 mA cm\({}^{-2}\)). The results indicated that the characteristic ACT absorption band at 245 nm decayed, until it disappeared, as a function of electrolysis time and \(j\). This decay is associated with the increase in the \(j\)[28]. When 30 and 60 mA cm\({}^{-2}\) were applied (Figure 2a,b), intense absorption bands were still observed up to 120 min of electrolysis, indicating that a low \(j\) did not significantly influence the insecticide degradation at the beginning of the process. However, when an increase in \(j\) (Figure 2c,d) is applied, intense absorption bands were observed only up to 60 and 30 min of electrolysis, when 90 and 120 mA cm\({}^{-2}\) were applied, respectively. This behavior confirms that an increase in the \(j\) increased the ACT removal rate [8; 21; 28], as is also observed in Figure 3, which shows a comparison of the influence of \(j\) on the EO of ACT using normalized maximum absorption as a function of electrolysis time. At 90 and 120 mA cm\({}^{-2}\), more significant removal rates were reached with short electrolysis times, while at lower j (30 and 60 mA cm\({}^{-2}\)), the decline in absorbance associated with the ACT characteristic band exhibited a slower rate of removal. Another feature that should be commented on is that at higher \(j\) (90 and 120 mA cm\({}^{-2}\)), the formation of a new absorption band at 275 nm is observed as a consequence of the formation of by-products during ACT degradation [9; 29]. Figure 2: Absorption spectra as a function of electrolysis time during the EO of 30 mg L\({}^{-1}\) of ACT at DSA by applying different \(j\): (**a**) 30, (**b**) 60, (**c**) 90, and (**d**) 120 mA cm\({}^{-2}\). Operating conditions: 0.5 M Na\({}_{2}\)SO\({}_{4}\) and 25 \({}^{\circ}\)C. Black and red arrows in the UV-vis spectra (a-d) indicate the bands related to ACT (245 nm) and to a by-product (275 nm), respectively. Considered an active anode, the degradation of ACT with Ti/TiO\({}_{2}\)-RuO\({}_{2}\)-ZrO\({}_{2}\) occurs mainly via higher oxides generated on its surface [28], especially at higher \(j\) (Equations (2) and (3)). This anode also promotes o.e.r. (Equation (4)), which occurs in parallel with the degradation of ACT, becoming an undesired reaction at higher \(j\) and consequently making the degradation process more difficult [30; 31; 32]. This behavior explains the lack of complete removal of ACT at different \(j\), proving that at a determined point, the o.e.r. takes place over the hydroxyl radicals' performance. These assertions are in agreement with the behaviors observed at the polarization curves in Figure 2, where a direct oxidation mechanism was suggested at the DSA electrode, which was influenced by the o.e.r. [32; 33; 34; 35]. \[\mathrm{MO_{x}(\,^{\bullet}OH)}\ \rightarrow\mathrm{MO_{x+1}+H^{+}+\,e^{-}} \tag{2}\]  
\[\mathrm{MO_{x+1}+R}\ \rightarrow\ \mathrm{RO+MO_{x}} \tag{3}\]  
\[\mathrm{MO_{x+1}\rightarrow\mathrm{MO_{x}+\,^{1}\!/\!2}\,O_{2}} \tag{4}\]  
The influence of the \(j\) on the degradation of ACT with the BDD anode is shown in Figure 4. These results indicate that the degradation of ACT occurred in 30 min of electrolysis. Comparing the absorption spectra obtained with DSA electrolysis with those achieved with BDD, it is possible to observe that, with the former, the characteristic ACT absorption band was gradually reduced, whereas it quickly disappears at all \(j\) values after 5 min of electrolysis with the latter. Unlike DSA, the BDD anode is considered a non-active electrode, therefore, organic compounds are quickly oxidized by free hydroxyl radicals produced at the diamond surface [15; 16; 17; 23; 35].