## 1 Introduction  
The continuous growth of industry-related activities has led to the discharge of persistent and potentially toxic organic compounds into the environment. Organic compounds with aromatic structures, such as most dyes used in the textile and food industry, phenolic compounds, and pesticides, are relatively challenging to remove through conventional adsorption, precipitation, and chemical/biochemical oxidation processes. Most of these \"conventional\" processes have several drawbacks, such as poor cost efficiencies or mineralization efficiencies [1, 2]. They often fail to completely remove organic pollutants, leaving trace amounts that still pose environmental and/or aesthetic concerns. Advanced oxidation processes (AOPs) such as the Fenton process have been known to have a much more economically efficient upscaling potential and a relatively low environmental impact compared with heterogeneous semiconductor photocatalysis-based AOPs [3, 4]. The Fenton process involves the formation of highly reactive nonspecific oxidant radicals, such as hydroxyl, perhydroxyl, superoxide, or sulfate, based on electron transfer between iron ions and a chemical species capable of generating such radicals, among which hydrogen peroxide, peroxide ion-generating substances (percarbonates, perborates), and persulfates are the most widely used. Traditionally, Fe\({}^{2+}\) ions catalyze AOPs more efficiently, but Fe\({}^{3+}\) ions can be used as well in combination with a chelating agent [5]. Usually, the electron transfer process works better in relatively acidic conditions (pH values between 2 and 4) due to the complex electrochemistry of iron, which can precipitate from solution as hydroxides with a low solubility, thus limiting the ability of iron ion to react with the oxidant [6]. The generation of oxidant radicals in the Fenton process could be efficiently conducted through chemical means alone, by light from the UV and visible domain (the so-called photo-Fenton process variant) [7], by ultrasonic longitudinal waves [8], or through electrochemical means [6]. The formation of the free hydroxyl radical in the homogeneous Fenton variant occurs in a one-step mechanism variant with a water-soluble Fe\({}^{2+}\) source and a two-step mechanism with the addition of Fe\({}^{3+}\) ions. Heterogeneous Fenton processes, which use zero-valent iron (ZVI) in the metallic form, are very promising due to the iron source's high accessibility and low cost, the high organic pollutant mineralization rates, and facile separation of the iron source from the treated wastewater. Zero-valent iron is a strong reducing agent and has been used in particulate form for the removal of different organic (aromatic compounds) for groundwater remediation in the form of permeable reaction barriers [9] or as a slurry [10]. ZVI in the form of micropowders with diameters in the range of 50 to 200 \(\upmu\)m [11] or in the form of nanopowders [12] shows a good reactivity in the presence of H\({}_{2}\)O\({}_{2}\), meaning it could react with the surface iron to produce Fe\({}^{2+}\) and Fe\({}^{3+}\) and initiate the Fenton process [13; 14; 15]. Several studies have demonstrated that the optimal pH in the case of ZVI shifts to higher values (4 to 6), allowing outstanding degradation efficiencies for organic aromatic compounds [16; 17]. However, zero-valent iron in particulate form has a strong tendency to aggregate, limiting its efficiency over time [12]. Additionally, uncontrolled iron leaching can occur, and the recovery and reusability of ZVI particles lead to the overall process having a higher cost [18]. Several supports for ZVI in particulate form, such as activated carbon cloths or zeolites. have been employed [19; 20]. Comparatively, considerably fewer approaches have used metallic iron in pure form (i.e., higher than 99.5%) in sheets or meshes as catalyst supports for photo-Fenton processes. Solid iron supports generate iron ions in the presence of hydrogen peroxide without the usual drawbacks of particle aggregation [21].