Improved 4-nitrophenol removal at Ti/RuO₂-Sb₂O₄-TiO₂ laser-made anodes

In this study, binary and ternary mixed metal oxide anodes of Ti/RuO₂-Sb₂O₄ and Ti/RuO₂-Sb₂O₄-TiO₂ were prepared using two different heating methods: conventional furnace and alternative CO₂ laser heating. The produced anodes were physically and electrochemically characterized by using different techniques. The main difference found in the laser-made anodes was their more compact morphology, without the common deep cracks found in anodes made by typical thermal decomposition, which showed an important correlation with the prolonged accelerated service life. The correlation between the physicochemical properties of the anodes with their performance towards the 4-nitrophenol oxidations is discussed. The results demonstrated that the ternary anode (Ti/RuO₂-Sb₂O₄-TiO₂) is very promising, presenting a kinetic 5.7 times faster than the respective binary anode and the highest removal efficiency when compared with conventionally made anodes. Also, the lowest energy consumption per unit of mass of contaminant removed is seen for the laser-made Ti/RuO₂-Sb₂O₄-TiO₂ anode, which evidences the excellent cost-benefit of this anode material. Finally, some by-products were identified, and a degradation route is proposed. Graphical abstract.