Comparison of the environmental impact of Fenton and Fenton-like reactions in heterogeneous and homogeneous phase applied to organic pollutant degradation through life cycle assessment.

Advanced oxidation processes (AOPs) are among the most effective wastewater treatment processes (WWTPs). However, it is important to consider the energy requirement, resource consumption, and emissions associated with implementing these technologies, as well as their effect on the sustainability of AOPs. In this sense, Life Cycle Assessment (LCA) is an excellent tool to determine the environmental impacts (EIs) implicit in WWTPs. In the present work, a comparison of the EI of Fenton and Fenton-like reactions in homogeneous and heterogeneous phases is presented. In the first stage, carbon materials impregnated with iron were synthesized and characterized as catalysts in heterogeneous reactions. Then, the kinetic study of phenol (model molecule) degradation through the four processes was performed. Later, an LCA was executed for each AOP and material synthesis using OpenLCA software. Finally, cost estimation and a comparison analysis were carried out. As relevant results, phenol was degraded with varying efficiencies, being the Fenton-like reaction in a homogeneous phase in the process that achieved the highest removal. After each reaction, the catalyst was recovered and reused in the same processes, finding that it could be used multiple times, thus reducing the EIs and costs associated with the synthesis processes. LCA also revealed that heterogeneous reactions have a lower EI in terms of CO generation, but a higher impact on fossil fuel consumption compared with homogeneous reactions. On the other hand, homogeneous reactions presented higher CO emissions and lower fuel consumption while reaching the total mineralization of the phenol molecule.