Critical review of Fenton and photo-Fenton wastewater treatment processes over the last two decades

Water pollution is currently one of the major problems that the scientific community must solve in the twenty-first century. This issue is made even more challenging by the fact that conventional effluent treatment processes usually show poor degradation performance for a variety of recalcitrant chemical components, remaining present after simple treatments. In this scenario, advanced oxidative processes emerge as a possible solution. Due to their simplicity, the Fenton and photo-Fenton processes have attracted the attention of the scientific community for decades. This review presents a critical analysis of the feasibility of these processes for full-scale diffusion. Seeking to elucidate this point, a broad review of the literature on Fenton and photo-Fenton processes is carried out, focusing on homogeneous processes, in the last two decades (2000–2021). With this review, the authors intend to fill part of the gap of studies in the literature about the potential applicability of scaling up the Fenton and photo-Fenton processes. Fundamentals, characteristics, process parameters, chemical and photochemical reactor designs, and scale-up challenges are examined in detail. Examples of applications of these oxidative processes in pilot and full-scale conditions are presented. Finally, this review concludes with current trends and future perspectives with the aim of helping researchers in the field to direct their topics and contribute to further development of scale-up studies in advanced oxidative processes, especially with Fenton reactions. Graphical abstract