A comparative life cycle assessment of Fe3+-polyaminocarboxylic acid-based catalysts for the degradation of phenol by photo-Fenton like process

Among the plethora of wastewater treatment processes, one of the most relevant Advanced Oxidation Processes (AOP) is the (photo) Fenton-like process in which Fe-complexes are employed as catalysts. Among the most investigated ligands belonging to the polyaminocarboxylic acids (APCAs) class are ethylenediaminetetraacetate (EDTA), ethylenediaminedisuccinate (EDDS) and iminodisuccinate (IDS). However, the environmental impacts associated with both the synthesis and application of Fe-APCAs is currently unknown thus limiting comparisons solely to catalytic performance. This study presents the first systematic comparison of the synthesis and application of these complexes, namely Fe-EDTA, Fe-EDDS and Fe-IDS, in (photo) Fenton-like catalytic processes for phenol degradation. The study integrates environmental sustainability assessment via life cycle assessment (LCA) with catalytic activities through the calculation of Turnover Frequencies (TOFs) to determine the optimum catalytic conditions. The study adopted a cradle to gate and cradle to grave approaches to evaluate the synthesis and application of the tested catalysts. Results show that Fe-IDS is the most environmentally sustainable option with respect to Fe-EDTA, achieving reductions of 4%–97% across twelve of the eighteen assessed impact categories during synthesis, including global warming potential, and reductions of 40%–50% across all impact categories for application although with a slightly lower TOF value than the highest value achieved with Fe- EDDS. Overall, these findings highlight the need to balance catalytic performance with environmental burdens when sustainability evaluations are carried out.