# Electrodegradation of Selected Water Contaminants: Efficacy and Transformation Products
## 3 Results and Discussion
### Removal Efficiency, Kinetic Analysis, and Energy Consumption of Electrooxidative Treatment
#### 3.2.1 Removal Efficiency and Energy Consumption of EO Treatment  
The electrochemical treatment of t-OPPE was performed at current densities of 5 and 10 mA/cm\({}^{2}\) with sodium sulphate (2 g/L Na\({}_{2}\)SO\({}_{4}\)) as a supporting electrolyte. Both current densities demonstrated a high efficiency in the removal of t-OPPE from the synthetic wastewater solution. However, for further analysis, data obtained at a current density of 5 mA/cm\({}^{2}\) were considered, given its positive impact on the energy efficiency of the process. At a current density of 5 mA/cm\({}^{2}\), the maximum removal efficiency was achieved within  
Figure 2: Mass spectrum of Triton X-100 (t-OPPE; 450–750 \(m/z\) range), LC-MS, ESI+. The difference between the peaks at \(m/z\) 488.39, 532.42, 576.46, 620.49, 664.53, and 708.55 is 44 \(m/z\), corresponding to one ethoxylate unit. 45 min of treatment, resulting in a t-OPPE concentration of 0.365 mg/L, corresponding to a removal efficiency of 96.5%. These findings confirm the high efficiency of the EO process, as shown in Figure 3a. The specific energy consumption for the treatment of t-OPPE over a period of 45 min was 114.1 kWh/kg-OPPE, or 2.91 kWh/m3 of wastewater. In comparison with advanced oxidation processes as studied by [PERSON] et al. [42], who investigated the degradation of t-OPPE using ultraviolet light (UV)/TiO\({}_{2}\), UV/H\({}_{2}\)O\({}_{2}\), and UV/S\({}_{2}\)O\({}_{8}\)\({}^{2-}\) systems, EO shows several key advantages. While the method using UV/S\({}_{2}\)O\({}_{8}\)\({}^{2-}\) achieves a higher removal efficiency (98.5%) in a shorter time (30 min), the energy demands are significantly higher compared to the electrochemical method. Specifically, the energy consumption reported by [PERSON] et al. [42] ranges from 606.3 kWh/m\({}^{3}\) at 15 \({}^{\circ}\)C to 76.9 kWh/m\({}^{3}\) at 45 \({}^{\circ}\)C, which is considerably higher than the energy requirement of the electrochemical t-OPPE treatment. Advanced oxidation treatments, particularly those involving UV radiation and chemical reagents, have high energy costs and require additional infrastructure, whereas EO relies on direct electrical energy, making it more economical and sustainable for continuous industrial applications. During the degradation of t-OPPE, _t_-octylphenol (t-OP) was identified as the primary degradation product and its degradation was also monitored at a current density of 5 mA/cm\({}^{2}\). The initial concentration of t-OP (present in untreated t-OPPE solution) was 16.2 \(\upmu\)g/L, which decreased to 0.77 \(\upmu\)g/L after 45 min of treatment, clearly indicating the high efficiency of the process in removing the degradation product, as also depicted in Figure 3a. The electrochemical oxidation of DBP was conducted using three different supporting electrolytes (2 g/L): sodium chloride (NaCl), sodium sulphate (Na\({}_{2}\)SO\({}_{4}\)), and sulphuric acid (H\({}_{2}\)SO\({}_{4}\)). The electrolysis was performed using the same electrochemical reactor as for t-OPPE at current density \(j\) = 10 mA/cm\({}^{2}\). The initial concentration of DBP in the synthetic wastewater was approximately 5 mg/L, and the treatment duration was 120 min. The removal efficiency of DBP varied significantly with the choice of supporting electrolyte: using Na\({}_{2}\)SO\({}_{4}\) as the supporting electrolyte, the removal efficiency reached 90.7%, which was notably higher compared to the efficiency observed with NaCl (_E_ = 75.5%). The highest removal efficiency of 93.4% was achieved when using H\({}_{2}\)SO\({}_{4}\) as the supporting electrolyte. The good performance observed with H\({}_{2}\)SO\({}_{4}\) can be attributed to the generation of highly reactive persulphate radicals (S\({}_{2}\)O\({}_{8}\)\({}^{2-\bullet}\)) in acidic conditions, which enhance the degradation of DBP.