## 4 Conclusions  
The study investigated the possibility of removing TY dye from an aqueous solution using the EC process with aluminium electrodes. Response surface methodology was applied to evaluate the effects of the three main independent parameters--current density (0.008-0.024 A cm\({}^{-2}\)), initial solution pH (3.0-7.0), and treatment time (10-50 min)--on the process parameters, including pH, temperature, TY dye concentration, and removal efficiency, and to optimise the operating conditions of the treatment process.  
As the EC process progresses, the removal efficiency of the TY dye increases, while the growth dynamics and final value (between approx. 28% and 99%) depend on the experimental conditions (current density, initial pH, and treatment time). High removal efficiency is achieved more quickly when current density increases and initial pH decreases. Contrary, sludge settles more rapidly at higher pH values due to the formation of denser flocs. Despite containing organic residues, EC-generated sludge has potential for reuse in environmental applications, such as adsorbents or construction materials, provided it undergoes thorough ecotoxicological assessment in accordance with EU regulations.  
During the EC process, aluminium anodes undergo general corrosion, with consumption increasing as current density rises and initial pH decreases. At the end of the EC process, the sludge was found to contain Al and O (from Al(OH)\({}_{3}\)) as well as C and S (from the removed dye), their content depending on the EC process conditions. EC not only removes TY from the solution but also alters its chemical structure through adsorption (on Al(OH)\({}_{3}\)) and possible degradation.  
Furthermore, the experimental data were statistically analysed, and mathematical models were developed for each response (pH, temperature, and dye concentration). The optimal conditions to treat TY using EC were derived and validated. The optimum current density, EC duration, and initial pH of the dye solution were found to be 0.016 A cm\({}^{-2}\), 18.741 min, and 3.3696, respectively. Under these optimal values of process parameters, the removal efficiency of TY should be 70% (or 0.016 mmol L\({}^{-1}\)).  
The results confirm that EC is a cost-effective treatment method for TY, with operating costs ranging from 0.245 to 7.486 EUR/m\({}^{3}\) depending on process conditions. Key contributors to cost are energy and electrode consumption, both of which can be optimised through operational adjustments. Furthermore, integrating renewable energy and alternative electrode materials can enhance the economic and environmental sustainability of the EC process, making it a promising solution for wastewater treatment.  
Conceptualization, S.G. and N.C.; methodology, S.G., N.C. and L.V.; software, N.C., S.G. and S.S.; validation, S.G. and N.C.; formal analysis, S.G., N.C. and S.S.; investigation, M.B., S.G., N.V.M., L.V. and S.S.; resources, A.R., L.V., S.G. and N.V.M.; data curation, S.G., N.C., S.S. and N.V.M.; writing--original draft preparation, S.G., L.V. and N.C.; writing--review and editing, S.G., L.V., N.C., N.V.M., A.R. and S.S.; visualisation, S.G. and N.C.; supervision, S.G., N.C. and L.V.; project administration, S.G., A.R. and L.V.; funding acquisition, L.V., S.G. and A.R. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
**Acknowledgments:** The authors would like to express their sincere gratitude to [PERSON] from the Faculty of Chemistry and Technology, University of Split, for conducting the FTIR measurements of the samples.  
**Conflicts of Interest:** The authors declare no conflict of interest.