# A Sustainable Electrochemical-Based Solution for Removing Acetamiprid from Water
## 3 Results
### COD Decay  
To carry out a more evident comparative analysis, Figure 7a depicts the normalized COD decay as a function of time at 90 mA cm\({}^{-2}\) in 0.5 M Na\({}_{2}\)SO\({}_{4}\). It was observed that until the period of 60 min of electrolysis, COD decay using the DSA anode was only 47.5%. Meanwhile, at the BDD anode, a more efficient removal was achieved (71.4%). It is important to note that the COD value may be also associated with the generation and \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Parameters**} & \multirow{2}{*}{**Synthetic Effluent**} & \multicolumn{2}{c}{**After Treatment**} \\ \cline{3-5}  & & **DSA** & **BDD** \\ \hline  & 436 nm & 98.4 & 32.6 & 6.1 \\ Color (DFZ units, m\({}^{-1}\)) & 525 nm & 89.2 & 28.1 & 3.4 \\  & 620 nm & 64.1 & 15.7 & 3.7 \\ Conductivity (mS cm\({}^{-1}\)) & 20.8 & 19.4 & 11.5 \\ Salinity (psu) & 18.5 & 17.54 & 13.85 \\ pH & 7.74 & 6.5 & 5.9 \\ Turbidity (NTU) & 23 & 43 & 21 \\ COD\({}_{30\text{ mA cm}^{-2}}\)(mg L\({}^{-1}\)) & & 25.6 & 15.7 \\ COD\({}_{60\text{ mA cm}^{-2}}\)(mg L\({}^{-1}\)) & 32.5 & 18.5 & 10.2 \\ COD\({}_{90\text{ mA cm}^{-2}}\)(mg L\({}^{-1}\)) & & 16.8 & 7.4 \\ COD\({}_{120\text{ mA cm}^{-2}}\)(mg L\({}^{-1}\)) & & 15.8 & 6.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Physicochemical characterization of effluent, before and after different treatment. increase of intermediates in the treated solution [42]; then, more treatment time is needed to eliminate ACT and all the by-products generated during the EO process. For this reason, the comparison between electrocatalytic materials was performed to determine the best operating conditions for the ACT treatment, allying removal of the contaminants and the best energy efficiency (Figure 7b). Figure 5: Absorption spectra of ACT during the EO of 300 mg L\({}^{-1}\) of ACT at **(a)** DSA and **(b)** BDD electrodes, as a function of electrolysis time. Operating conditions: 90 mA cm\({}^{-2}\), 0.5 M Na\({}_{2}\)SO\({}_{4}\) and 25 \({}^{\circ}\)C. Red and black arrows in the UV-vis spectra (a-d) indicate the bands related to ACT (245 nm) and to a by-product (275 nm), respectively. After analyzing the performance of the EO of synthetic ACT effluent by applying 90 mA cm\({}^{-2}\), the effect on the increase of the ACT concentration demonstrated that the cost of the treatment increases as a function of \(j\) (Figure 7b), being more significative when BDD was used as an anode [8; 20; 21; 43]. Another feature is that it is clear that even when the BDD anode promotes better results, achieving higher COD removal efficiencies, the DSA electrode requires lower energy consumption (inset in Figure 7b). However, 60% COD removal could be achieved under the described operating conditions at the BDD anode with modest energy requirements, and a post-treatment could be applied [9]. Based on the existing literature, hypothetical degradation pathways of ACT during the EO process were proposed from the 19 degradation intermediates identified by [PERSON] and co-workers [44] when a Yb-doped PbO\({}_{2}\) electrode was used in 0.05 mol L\({}^{-1}\) Na\({}_{2}\)SO\({}_{4}\) solution. The three degradation pathways proposed (demethylation, decyanation, and hydroxylation) were identified as I, II, and III sub-routes according to the different initial attacking ACT positions on three active functional groups by hydroxyl radicals (Figure 8) [44]. Sub-route I was divided into I-1 and I-2 degradation pathways that correspond to dechlorination and demethylation starting reactions, respectively, with successive steps (Figure 8). However, [PERSON] and co-workers [44] have considered in two routes (I-1 and III) the attack of the hydroxyl radicals (in sub-route I-1, only after a decyanation, but it could be simultaneously attained with hydroxyl radical reaction) as a starting degradation step (a radical reaction).