Patricia García-Muñoz
email: patricia.gmunoz@upm.es

Fernando Fresno

Christophe Lefevre

Didier Robert

Nicolas Keller
email: nkeller@unistra.fr

Ti-modified LaFeO 3 /β-SiC alveolar foams as immobilized dual catalyst with combined photo-Fenton and photocatalytic activity

Keywords: alveolar β-SiC foam, dual Ti-modified LaFeO3 catalyst, photoassisted CWPO, photocatalysis, water treatment, photonic efficiencies

Ti-modified LaFeO3/β-SiC alveolar foams were used as immobilized, highly robust dual catalyst with combined photo-Catalytic Wet Peroxide Oxidation (CWPO) and photocatalytic activity under UV-A light. They were prepared by incipient wetness impregnation of a β-SiC foam support, by implementing a sol-gel Pechini synthesis at the foam surface in the presence of dried amorphous sol-gel titania as titanium source.

Physico-chemical and catalytic features suggest the stabilization at the foam surface of a substituted La1-xTixFeO3 catalyst analogous to its powdery counterpart. Taking 4chlorophenol removal in water as a model reaction, its dual nature enables both high reaction rates and full TOC conversion, due to a synergy effect, while its macroscopic structure overcomes the drawback of working with powdery catalysts. Further, it yields photonic efficiencies for degradation and mineralization of ca. 9.4% and 38%, respectively, that strongly outperform those obtained with a reference TiO2 P25/β-SiC foam photocatalyst. The enhancement of the catalyst robustness upon Ti modification prevents any Fe leaching to the solution, and therefore the optimized macroscopic foam catalyst with 10wt.% catalyst loading operates through pure heterogeneous surface reactions, without any activity loss during reusability test cycles.

INTRODUCTION

The emergence of biorecalcitrant hazardous organic pollutants that are refractory to the conventional biological water treatments based on activated sludge or even membrane bioreactors, combined with increasingly stringent environmental govern regulations, has created strong incentive for the development of new sustainable and efficient water treatment technologies [START_REF] Malato | Decontamination and Disinfection of Water by Solar Photocatalysis: Recent Overview and Trends[END_REF] .

The lack of efficient processes for water treatment is the driving force for the development of Advanced Oxidation Processes (AOPs), based on the generation at room temperature of highly oxidative HOx° radicals that react non-selectively with the refractory organic pollutants provoking their depletion [START_REF] Coronado | Design of Advanced Photocatalytic Materials for Energy and Environmental Applications[END_REF] . Special attention has been given to the H2O2-mediated Fe-based Fenton process, or its heterogenized counterpart known as catalytic wet peroxide oxidation (CWPO), and to semiconductor photocatalysis, since they both operate with a high efficiency and relatively low investment/running costs.

While Fenton-like processes benefit from high degradation rates, they suffer from incomplete mineralization of the refractory targets that result from the well-known complexation of Fe by refractory carboxylic compounds. By contrast, heterogeneous photocatalysis can reach total mineralization of a large range of refractory organic compounds, but with far lower reaction rates. Combining both AOPs, heterogenized photo-CWPO and photocatalysis, within a single-phase catalyst is consequently a promising strategy investigated only recently for intensifying the mineralization process by a synergy effect [START_REF] García-Muñoz | Sulfonamides Photoassisted Oxidation Treatments Catalyzed by Ilmenite[END_REF][START_REF] García-Muñoz | Modified Ilmenite as Catalyst for CWPO-Photoassisted Process under LED Light[END_REF] .

Only a few works have reported on the use of Fe-containing single-phase catalysts for the light-and H2O2-mediated catalytic degradation of organic pollutants in water, using notably natural iron oxide (α-Fe2O3) [START_REF] Mechakra | Use of Natural Iron Oxide as Heterogeneous Catalyst in Photo-Fenton-like Oxidation of Chlorophenylurea Herbicide in Aqueous Solution: Reaction Monitoring and Degradation Pathways[END_REF] , natural FeTiO3 ilmenite [START_REF] García-Muñoz | Sulfonamides Photoassisted Oxidation Treatments Catalyzed by Ilmenite[END_REF][START_REF] García-Muñoz | Modified Ilmenite as Catalyst for CWPO-Photoassisted Process under LED Light[END_REF] , spinel ZnFe2O4 [START_REF] Cai | Visible Light-assisted Heterogeneous Fenton with ZnFe2O4 for the Degradation of Orange II in Water[END_REF] and Ba-doped BiFeO3 [START_REF] Soltani | Improving Heterogeneous Photo-Fenton Catalytic Degradation of Toluene under Visible Light Irradiation through Ba-doping in BiFeO3 Nanoparticles[END_REF] . However, the catalysts suffer from incomplete TOC conversion or from too low reaction rates. Recently, we have demonstrated that the synergy effect between photocatalysis and photo-CWPO operates very efficiently on a narrow band gap La1-xTixFeO3 orthoferrite powdery catalyst with 11% Ti ® La substitution degree and a 4 at.% Ti content. This catalyst gives rise to full mineralization of 4-chlorophenol (4-CP) in water at high reaction rates under UV-A or visible light [START_REF] Garcia-Muñoz | Highly Robust La1-xTixFeO3 Dual Catalyst with combined Photocatalytic and Photo-CWPO Activity under Visible Light for 4-chlorophenol Removal in Water[END_REF][START_REF] Garcia-Muñoz | Ti-substituted LaFeO3 Perovskite as Photoassisted CWPO Catalyst for Water Treatment[END_REF][START_REF] García-Muñoz | Synergy Effect Between Photocatalysis and Heterogeneous PhotoFenton Catalysis on Ti-Doped LaFeO3 Perovskite for High Efficiency Light-Assisted Water Treatment[END_REF] . This dual catalyst was prepared as a powder by modifying a Pechini sol-gel synthesis using a dried amorphous titania as titanium source, while the cationic substitution extent was controlled by both the amount and the nature of the titanium source introduced, as well as by the final calcination temperature. The key feature was driven by the partial cationic substitution within the orthoferrite network, that strongly enhanced the reaction rates and increased the catalyst robustness by more than two orders of magnitude compared to its unsubstituted counterpart, with a complete inhibition of Fe release and the absence of any loss of catalytic activity along several test cycles.

However, water treatment using powdery nanoparticulate catalysts requires the frequent implementation of time-consuming and costly filtration recovery steps, that drastically reduce the process viability. In the search for more efficient water treatment processes operating in a continuous mode, open-cell alveolar solid foams have attracted significant interest as structured supports for immobilizing photocatalysts, due to their ability of acting as active static mixer while working at an ultra-low pressure drop, and maintaining a better light transmission to the reactor core than packed-bed supports [START_REF] Masson | β-SiC Alveolar Foams as a structured Photocatalytic Support for the Gas Phase Photocatalytic Degradation of Methylethylketone[END_REF][START_REF] Zhu | Application of Porous Nickel-Coated TiO2 for the Photocatalytic Degradation of Aqueous Quinoline in an Internal Airlift Loop Reactor[END_REF][START_REF] Ishiguro | Photocatalytic Activity of Cu 2+ /TiO2-coated Cordierite Foam inactivates Bacteriophages and Legionella Pneumophila[END_REF][START_REF] Martín-Sómer | Novel Macroporous 3D Photocatalytic Foams for simultaneous Wastewater Disinfection and Removal of Contaminants of Emerging Concern[END_REF][START_REF] Robert | Immobilization of a Semiconductor Photocatalyst on Solid Supports: Methods, Materials, and Applications[END_REF] .

Self-bonded (binder-free) β-SiC foams prepared via the Shape Memory Synthesis replica method stand out in comparison to polymer, metallic and other ceramic foams such as eg. cordierite, alumina or zirconia [START_REF] Martín-Sómer | Novel Macroporous 3D Photocatalytic Foams for simultaneous Wastewater Disinfection and Removal of Contaminants of Emerging Concern[END_REF][START_REF] Švagelj | Titania-Coated Alumina Foam Photocatalyst for Memantine Degradation Derived by Replica Method and Sol-Gel Reaction[END_REF] , thanks to good characteristics like high thermal/chemical stability which allows them to withstand severe conditions, and high density of oxygenated surface groups, thereby favouring the anchorage of catalysts [START_REF] Kouamé | Preliminary Study of the Use of β-SiC foam as a Photocatalytic Support for Water Treatment[END_REF][START_REF] Kouamé | β-SiC Foams as a Promising Structured Photocatalytic Support for Water and Air Detoxification[END_REF] .

While β-SiC foams have received strong interest for immobilizing titania photocatalysts 17-23 , to date only scarce works have reported on their use -and more globally on the use of alveolar foams -as support for Fenton-like catalysts. For example, magnetite powder onto Ni and FeCrAl [START_REF] Do | Magnetite-coated Metal Foams as one-body Catalysts for Fenton-like Reactions[END_REF] , BiFeO3/Ni [START_REF] Li | Application of BiFeO3-based onNnickel Foam Composites with a Highly Efficient Catalytic Activity and easily Recyclable in Fenton-like Process under Microwave Irradiation[END_REF] , sludge carbon/SiC [START_REF] Yang | Three-dimensional Hierarchical Porous Sludge-derived Carbon supported on Silicon Carbide Foams as effective and stable Fenton-like Catalyst for odorous Methyl mercaptan elimination[END_REF] , ferrisilicate/SiC [START_REF] Ou | On developing Ferrisilicate Catalysts supported on Silicon Carbide (SiC) Foam Catalysts for continuous Catalytic Wet Peroxide Oxidation (CWPO) Reactions[END_REF] or Fe-ZSM-5/SiC [START_REF] Ou | Hierarchical Fe-ZSM-5/SiC Foam Catalyst as the Foam Bed Catalytic Reactor (FBCR) for Catalytic Wet Peroxide Oxidation (CWPO)[END_REF] have been reported as dark-Fenton foam catalysts for CWPO. However, these foam-based catalysts usually suffer from a low stability of the Fe-containing supported active phase, and from uncomplete mineralization of the effluent. It is worth noting that photo-Fenton-like degradation was recently achieved on perovskite-type catalysts supported on cordierite honeycomb monoliths , [START_REF] Orak | Photocatalytic and Photo-Fenton-like Degradation of Methylparaben on Monolith-supported Perovskite-type Catalysts[END_REF] and on TiO2-FeSO4 immobilized on metallic foams [START_REF] Abdi | Application of a Hybrid Enzymatic and Photo-Fenton Process for investigation of Azo Dye Decolorization on TiO2/metal-foam Catalyst[END_REF] .

Here, we report a reusable and robust immobilized catalyst for water treatment based on Ti-modified LaFeO3 supported on an alveolar β-SiC foam, prepared by synthesizing the Ti-doped ferrite in situ at the foam surface. The removal of the 4-CP has been chosen as test reaction under UV-A light, as a representative of industrial wastewater refractory pollutants in AOP studies [START_REF] Munoz | Combining efficiently Catalytic Hydrodechlorination and Wet Peroxide Oxidation (HDC-CWPO) for the Abatement of Organochlorinated Water Pollutants[END_REF] . We demonstrate that this macroscopic Ti-substituted LaFeO3/β-SiC foam dual catalyst combines the advantages of both photocatalysis and photo-CWPO AOPs. This catalyst leads to high mineralization rates and complete TOC conversions at circumneutral pH conditions, without any Fe release to the solution, and overcomes the drawbacks of working with powdery catalysts.

EXPERIMENTAL

Materials

4-CP (>99%) and H2O2 (>30%) were purchased from Sigma Aldrich. Fe(NO3)3 nonahydrate, La(NO3)3 hexahydrate, citric acid hydrate (C6H8O7•xH2O, 99.5%) and titanium tetraisopropoxide (TTIP, 97%) were purchased from Sigma Aldrich.

Commercially available Aeroxide© TiO2 P25 (hydrophilic fumed titanium oxide, >99.5%) was obtained from Evonik (Germany). Self-bonded β-SiC alveolar foams with medium specific surface area were synthesized by the SICAT-ACM GmbH Company (Willstätt, Germany) according to the shape memory synthesis (SMS) replica method, in which a pre-shaped polyurethane foam is transformed into the corresponding β-SiC carbide [START_REF] Nguyen | Innovative porous SiC-based materials: From Nanoscopic understandings to Tunable Carriers serving Catalytic Needs[END_REF] . The method relies on the fact that the original macrostructural features of a solid, i.e. its macroscopic shape, are retained after synthesis. β-SiC foams can thus be manufactured with adjustable shapes suitable for adaption to the reactor geometry. In this work, 8 pore per inch (PPI) β-SiC alveolar foams with a mean cell size of 5400 ± 700 µm, a mean window size of 2300 ± 600 µm and a mean bridge diameter of 575 ± 80 µm have been used. They have an open porosity of 0.91 ± 0.05, and a geometrical specific surface area, derived from the open porosity and the mean strut diameter according to the model developed by Edouard and co-workers [START_REF] Edouard | Experimental Measurements and Multiphase Flow Models in Solid SiC Foam Beds[END_REF][START_REF] Huu | Towards a more Realistic Modeling of Solid Foam: Use of the Pentagonal Dodecahedron Geometry[END_REF][START_REF] Lacroix | Pressure Drop Measurements and Modeling on SiC foams[END_REF][START_REF] Ledoux | Silicon Carbide: A Novel Catalyst Support for Heterogeneous Catalysis[END_REF] , of 626 ± 200 m -1 .

In situ synthesis of the β-SiC foam supported Ti-modified LaFeO3 catalysts

The β-SiC alveolar foams were used as 5 cm (d) x 2 cm (h) disks. Prior to the ferrite synthesis onto the foam, the alveolar foams were calcined at 1000 °C to remove by combustion residual unreacted carbon species that might be released to the aqueous solution during the reaction, as well as to form a natural washcoat made of amorphous oxygenated phases at the surface of the foams, thus favouring the in-situ aqueous phase synthesis of the supported ferrite.

The β-SiC foam supported Ti-modified LaFeO3 catalysts were prepared by incipient wetness impregnation of the β-SiC foam support disks, that allows the modified sol-gel Pechini synthesis to be performed in-situ at the foam surface. The impregnation suspension was similar to that used for synthesizing the LaFeO3-based catalysts as powder [START_REF] Garcia-Muñoz | Ti-substituted LaFeO3 Perovskite as Photoassisted CWPO Catalyst for Water Treatment[END_REF] . First, stoichiometric amounts of La(NO3)3•6H2O and Fe(NO3)3•9H2O were dissolved in distilled water (15 mL), together with C6H8O7•xH2O used as complexation agent in a stoichiometric molar ratio with respect to the metallic ions. The titanium source, either commercial TiO2 Aeroxide© P25 or a dried amorphous titania was then dispersed in this solution. The amorphous titania was obtained by a sol-gel synthesis under basic conditions using TTIP as a precursor, as detailed in Supporting Information SI1 and in Garcia-Munoz et al. [START_REF] García-Muñoz | Synergy Effect Between Photocatalysis and Heterogeneous PhotoFenton Catalysis on Ti-Doped LaFeO3 Perovskite for High Efficiency Light-Assisted Water Treatment[END_REF] , with a final drying step at 110 °C for 12 h. The concentrations of the precursors in the impregnation suspension were adjusted for preparing the LaFeO3 phase with contents of 5 wt.%, 10 wt.% and 20 wt.% relative to the β-SiC foam support, and the titanium added corresponded to a nominal amount of 10 wt.% in terms of TiO2 with respect to the theoretical amount of LaFeO3 phase synthesized (details in Table S1).

The precursor suspension was kept under stirring during the full impregnation process. Due to the low total pore volume of the β-SiC foam support, the dropwise impregnation of the foam was sequentially implemented, with an intermediate drying step at 80 ºC for 30 min between two consecutive impregnation steps. The process was repeated several times until the full impregnation of the suspension. The foam was dried overnight at 80 ºC and calcined following a heating cycle as reported by Gosovi et al. [START_REF] Gosavi | Pure Phase LaFeO3 Perovskite with improved Surface Area Synthesized using Different Routes and its Characterization[END_REF] and similar to that used for synthesising LaFeO3 and Ti-modified LaFeO3 powders [START_REF] Garcia-Muñoz | Highly Robust La1-xTixFeO3 Dual Catalyst with combined Photocatalytic and Photo-CWPO Activity under Visible Light for 4-chlorophenol Removal in Water[END_REF][START_REF] García-Muñoz | Synergy Effect Between Photocatalysis and Heterogeneous PhotoFenton Catalysis on Ti-Doped LaFeO3 Perovskite for High Efficiency Light-Assisted Water Treatment[END_REF] , with a heating rate of 5 °C/min, holding the temperature at 600 °C for 2 h, before further maintaining a temperature plateau for 2 h at 800 °C.

The obtained catalysts were labelled as P25-LFO/β-SiC foam and SG-LFO/β-SiC foam, whether the commercial TiO2 Aeroxide© P25 or the dried amorphous titania, respectively, was used as titanium source. A reference titanium-free β-SiC foam based catalyst, labelled as LFO/β-SiC foam, was synthesized following the same protocol without any addition of titanium source.

The weight load of the β-SiC foam supported catalyst was calculated relative to the weight of the β-SiC foam support by weight difference. With a weight of 5 g ± 0.05 g for the β-SiC foam disks, contents of 5 wt.%, 10 wt.% and 20 wt.% of LFO correspond to 25 mg, 50 mg and 100 mg of immobilized LFO phase, respectively.

Characterisation techniques

X-ray diffraction (XRD) patterns were recorded at room temperature in a θ/θ mode on a Brucker D8 Advance diffractometer equipped with a monochromatic copper radiation source (Kα = 1.54056 Å), with a scan step of 0.02°. Advanced XRD recording was carried out on a Bruker D8 Discover diffractometer. Details are explained in Supporting Information SI2.

The Brunauer-Emmett-Teller (BET) specific surface area has been calculated from the N2 adsorption isotherm recorded on a Micrometrics Tristar 3000 using N2 as adsorbate at -196 °C, with a prior outgassing at 250°C overnight to desorb the impurities and moisture.

Scanning Electron Microscopy (SEM) has been performed in a secondary mode on a Zeiss GeminiSEM 500 microscope equipped with a FEG Schottky source.

The transmittance of the β-SiC foam based catalysts was defined as the fraction of the incident light, in terms of UV-A irradiance, being transmitted through the materials.

It was measured by varying the foam thickness, using a wideband RPS900-W rapid portable spectroradiometer from International Light Technology.

Typical reaction procedure

The 4-CP oxidation tests were carried out in a batch beaker-type glass reactor (55 mm internal diameter) at atmospheric pressure, at room temperature (using a cooling bath) and with H2O2 as main oxidant. In a typical reaction procedure, the supported photocatalyst was placed in 100 mL of a 25 mg/L aqueous solution of 4-CP (initial organic carbon concentration of 14.8 ppm). Prior to irradiation, the 4-CP solution was stirred for 1 h in the dark in the presence of the immersed foam photocatalyst to ensure the establishment of the adsorption/desorption equilibrium. After adding hydrogen peroxide at the stoichiometric concentration corresponding to a complete mineralization of the initial pollutant (i.e. 125 mg/L), the experiments were carried out under stirring (350 rpm) and UV-A irradiation (Philips 24W/10/4P lamps, 60 W/m 2 ; λmax= 365 nm, ).

At each time interval, 8 mL of solution was sampled and then filtered through 0.20 µm membrane filters to remove the photocatalyst powder, and then the concentration of 4-CP was determined by UV-visible spectrophotometry by monitoring the disappearance of the main absorption peak at λ= 224 nm [START_REF] Pera-Titus | Degradation of Chlorophenols by means of Advanced Oxidation Processes: a General Review[END_REF] . Total Organic Carbon (TOC) measurements were performed using a Shimadzu TOC-L analyzer. The hydrogen peroxide concentration was measured by colorimetric titration using the TiOSO4 method [START_REF] Eisenberg | Colorimetric Determination of Hydrogen Peroxide[END_REF] and the Fe leached during the time-course of the reaction was quantified by the orthophenanthroline method [START_REF] Sandell | Colorimetric Determination of Traces of Metals[END_REF] . Photonic efficiencies, as defined by the IUPAC recommendations [START_REF] Pera-Titus | Degradation of Chlorophenols by means of Advanced Oxidation Processes: a General Review[END_REF] , were calculated both for 4-CP oxidation and for mineralization, as described in Supporting Information SI3 and Figure S1.

RESULTS AND DISCUSSION

Characterization

Optical images of the bare β-SiC foam and the supported LFO-based catalysts, shown in Fig. 1A-D, evidence the macroscopic homogeneity of the coating on the foam support.

The coating homogeneity is favoured by the presence at the β-SiC surface of a SiOxCy/SiO2 oxygenated layer with nanometric thickness [START_REF] Keller | Towards the Oxygenated Phase Coverage Rate of β-SiC Surface[END_REF][START_REF] Keller | Influence of the Preparation Conditions on the Synthesis of High Surface Area SiC for Use as a Heterogeneous Catalyst Support[END_REF] . This amorphous layer improves the hydrophilic character of the support surface. By acting as as a natural washcoat that interacts with the aqueous precursors during the Pechini sol-gel synthesis 43-46 , this oxygenated surface layer favours the formation of covalent oxygen-mediated bonds at the LFO/β-SiC interface during the final calcination/crystallization step at 800°C. They are responsible for the strong anchorage of the supported phase and prevent from any loss of materials to the solution, similarly to what is observed for ceramic foam supported TiO2 systems [START_REF] Robert | Immobilization of a Semiconductor Photocatalyst on Solid Supports: Methods, Materials, and Applications[END_REF][START_REF] Kouamé | Preliminary Study of the Use of β-SiC foam as a Photocatalytic Support for Water Treatment[END_REF] . It must be said, that we cannot rule out the existence of a thin interfacial phase -that would slightly structurally differs from the supported LFO -, and that would facilitate a very firm attachment between two phases with totally different structures to be effective, by acting as a glue or allowing a progressive structural change to take place from the support surface to the supported LFO crystals. content of 10 wt.%, with a concomitant decrease in porosity (Table 1, Figure S2), a slight increase in both surface area (to ca. 13.2-14.6 m 2 /g) and pore volume was observed for the Ti-LFO/β-SiC foams. However, even with this setup, the determination of the cationic distribution proved unsuccessful, in contrary to the analogous study performed on LFO powders, that proved the partial La ® Ti substitution with a 11% rate [START_REF] García-Muñoz | Synergy Effect Between Photocatalysis and Heterogeneous PhotoFenton Catalysis on Ti-Doped LaFeO3 Perovskite for High Efficiency Light-Assisted Water Treatment[END_REF] . Therefore, the theoretical variation of the peak intensities was computed for characterizing the detectability and the sensitivity to structural Ti of some selected characteristic (hkl) Bragg peaks of the LFO phase, as shown in Figures S4A andS4B. The results clearly show that the most sensitive peak to the insertion of titanium is the (110), while the other peaks have either a too low intensity (e.g. 111) or a too low relative variation (i.e.,sensitivity, e.g. 220). In the case of a bulk LFO sample, the relative strength of the (110) peak is ca. 15% with a computed sensitivity of ca. 35% when 20% of Ti is inserted. Taking this into account, the normalized intensity variation of the (110) peak of LFO expressed here relative to the (111) peak of β-SiC (i.e.

the most intense peak) has been computed for a sample consisting in a SiC matrix with 12% of LFO (Figure S4C). It demonstrates that, for the expected Ti ® La substitution degree of 11% (by analogy with the study with powders) -and even for a substitution degree computed at 25% -, the insertion of Ti into the LFO structure results in a variation of a few thousandths of the measured intensity. Such tiny variations cannot be detected with a conventional diffractometer and would require the use of a synchrotron facility.

The structural analogy between both powdery SG-LFO and β-SiC foam supported SG-LFO catalysts was supported by the XPS investigations. Indeed, although much lower signal intensities were recorded due to the presence of the β-SiC matrix, the core orbital XPS spectra demonstrate the presence of La 3+ , Fe 3+ and Ti 3+ cations at the surface of the supported SG-LFO catalyst, like its bulk SG-LFO counterpart (Figure S5) [START_REF] García-Muñoz | Synergy Effect Between Photocatalysis and Heterogeneous PhotoFenton Catalysis on Ti-Doped LaFeO3 Perovskite for High Efficiency Light-Assisted Water Treatment[END_REF] .

Independently of the catalyst form, similar binding energies were recorded for the different orbital doublet contributions, in agreement with a formal +3 oxidation state within a ABO3 structure [START_REF] Thirumalairajan | Novel Synthesis of LaFeO3 Nanostructure Dendrites: A Systematic Investigation of Growth Mechanism, Properties, and Biosensing for Highly Selective Determination of Neurotransmitter Compounds[END_REF][START_REF] Humayun | Synthesis of ZnO/Bi-doped porous LaFeO3 Nanocomposites as Highly Efficient Nano-Photocatalysts dependent on the Enhanced Utilization of Visible-light-excited Electrons[END_REF][START_REF] Petrović | 3 (M=Mg, Ti, Fe) Perovskite Type Oxides: Preparation, Characterization and Catalytic Properties in Methane Deep Oxidation[END_REF][START_REF] Faye | Influence of Lanthanum Stoichiometry in La1-xFeO3-δ Perovskites on their Structure and Catalytic Performance in CH4 Total Oxidation[END_REF][START_REF] Yamashita | Analysis of XPS spectra of Fe 2+ and Fe 3+ Ions in Oxide Materials[END_REF] . b bulk powder LFO prepared following the Pechini sol-gel synthesis described in Supporting Information (Figure S7) and in [START_REF] Garcia-Muñoz | Ti-substituted LaFeO3 Perovskite as Photoassisted CWPO Catalyst for Water Treatment[END_REF] .

Table 2. Kinetic rate constants of H2O2 decomposition, 4-CP oxidation and mineralization, through the combined photo-CWPO and photocatalysis AOPs. a apparent kinetic rate constant attributed to the initial photo-CWPO/photocatalytic combined process b apparent kinetic rate constant attributed to the pure photocatalytic reaction after complete H2O2 depletion c it must be said that the progressive increase in the active Fe ion concentration in the solution made a pseudo first order kinetic law for the H2O2 decomposition inapplicable, as the first order apparent kinetic rate constant is linearly depending on the homogeneous (released) Fe ion concentration, that cannot be considered as constant during the test. Whatever the LFO content, the LFO/β-SiC foam catalysts suffered from a strong release of iron to the solution, within the 0.8-2.5 mg/L range depending on the content of active phase. The low stability of the supported LFO catalyst is in agreement with the behaviour of LFO powders previously used as suspensions in batch reactors in the combined photo-CWPO/photocatalysis process [START_REF] García-Muñoz | Synergy Effect Between Photocatalysis and Heterogeneous PhotoFenton Catalysis on Ti-Doped LaFeO3 Perovskite for High Efficiency Light-Assisted Water Treatment[END_REF] . As a result of the low stability of the LFO catalyst, the leached iron can contribute significantly to the process activity through a typical homogeneous photo-Fenton mechanism. Consequently, the concentration profiles and the apparent kinetic rate constants reported in Figure 4 and in Table 2, respectively, can not only be attributed to pure heterogeneous reactions. The iron released to the solution is proposed to be responsible for the incomplete mineralization of the 4-CP substrate, as often reported for CWPO reactions [START_REF] Pliego | Fate of Iron Oxalates in Aqueous Solution: The Role of Temperature, Iron Species and Dissolved Oxygen[END_REF][START_REF] Zazo | UV-LED assisted Catalytic Wet Peroxide Oxidation with a Fe(II)-Fe(III)/activated Carbon Catalyst[END_REF] . Indeed, iron in solution is prone to form highly stable Fe complexes by reaction with the latest intermediates like short-chain carboxylic acids (oxalic, formic or acetic acids). The very slow photodegradation ability of those complexes inhibits the conversion of the late intermediates by stopping the iron redox cycle, and consequently does not allow complete mineralization of the substrate to be achieved despite total H2O2 depletion (Eq. ( 1)) [START_REF] Zazo | UV-LED assisted Catalytic Wet Peroxide Oxidation with a Fe(II)-Fe(III)/activated Carbon Catalyst[END_REF][START_REF] Pliego | Trends in the Intensification of the Fenton Process for Wastewater Treatment: An Overview[END_REF][START_REF] García-Muñoz | Evaluation of Photoassisted Treatments for Norfloxacin Removal in water using Mesoporous Fe2O3-TiO2 Materials[END_REF] .

["# $% ('()) * )] -% ./ 0 1 "# -% + () -+ '

[Eq.1]
The influence of the LFO content on the characteristic apparent kinetic rate constants is summarized in Figure 5, considering a pseudo first order reaction for the 4-CP degradation and a zero order reaction for the TOC conversion as usual in photoassisted processes. The evolution of both rate constants follows a similar behavior, with a first linear increase with increasing the LFO loading on the β-SiC foam before achieving a simili plateau. This behavior is similar to that observed in pure photocatalysis using alveolar foams as support for TiO2 in gas-and liquid-phase applications, independently of the TiO2 nature, of the immobilization process and of the photonic flux, [START_REF] Masson | β-SiC Alveolar Foams as a structured Photocatalytic Support for the Gas Phase Photocatalytic Degradation of Methylethylketone[END_REF][START_REF] Martín-Sómer | Novel Macroporous 3D Photocatalytic Foams for simultaneous Wastewater Disinfection and Removal of Contaminants of Emerging Concern[END_REF][START_REF] Kouamé | β-SiC Foams as a Promising Structured Photocatalytic Support for Water and Air Detoxification[END_REF][START_REF] Kouamé | TiO2/β-SiC Foamstructured Photoreactor for Continuous Wastewater Treatment[END_REF] i.e., a first increase in the amount of illuminated particles and subsequently a screening effect of excess particles. Although less studied, the rate profiles observed in heterogeneous Fenton-like processes usually evidence a first increase with the Fe content, while too high contents are counterproductive, due usually to the suspension turbidity that reduces the light penetration to the reactor core, and/or to the scavenging of excess Fe by OH° [START_REF] Ayodele | Degradation of Phenol in Photo-Fenton Process by Phosphoric acid modified Kaolin supported Ferric-oxalate Catalyst: Optimization and kinetic Modeling[END_REF][START_REF] García-Muñoz | Treatment of Hospital Wastewater through the CWPO-Photoassisted Process catalyzed by ilmenite[END_REF] .

Obviously, it must be said that the rate constants cannot be entirely related to the activity of the β-SiC foam-based catalysts, as those constants contain an homogeneous contribution due to the presence of iron in solution. However, the 10-LFO/β-SiC foam catalyst can be considered as optimized in terms of amount of active phase immobilized on the structured support, i.e. 10 wt.%, with apparent rate constants of 0.039 min -1 and 0.182 mgL -1 min -1 for 4-CP degradation and TOC conversion, respectively. This agrees with the optimal wt.% contents of 10-15% reported for TiO2/β-SiC foam photocatalysts, that slightly varied depending on the application and the kind of TiO2 [START_REF] Masson | β-SiC Alveolar Foams as a structured Photocatalytic Support for the Gas Phase Photocatalytic Degradation of Methylethylketone[END_REF][START_REF] Kouamé | β-SiC Foams as a Promising Structured Photocatalytic Support for Water and Air Detoxification[END_REF][START_REF] Kouamé | TiO2/β-SiC Foamstructured Photoreactor for Continuous Wastewater Treatment[END_REF] . It must be said that the progressive increase in the Fe concentration in the solution made a pseudo first order kinetic model for H2O2 decomposition inapplicable, as the first order apparent kinetic rate constant depends linearly on the homogeneous (released) Fe concentration, that cannot be considered here as constant during the test. [START_REF] De Laat | Catalytic Decomposition of Hydrogen Peroxide by Fe(III) in Homogeneous Aqueous Solution: Mechanism and Kinetic Modeling[END_REF] Unlike the powdery catalysts in batch mode, for which this effect can be most of the time neglected, this deviation from the pseudo first order kinetic law is particularly marked when using immobilized catalysts that have reduced activity in comparison to their powdery counterparts. UV-A irradiance of 60 W m -2 .

Pure photocatalysis on LaFeO3/β-SiC foams

Once the optimal load of the catalyst on the β-SiC foam was determined, the activity of the unmodified and Ti-modified LFO/β-SiC foam catalysts in pure photocatalysis is reported in Figure 6. As expected because of the lower irradiated surfaces exposed by the alveolar foam, the immobilized catalysts display a reduced photoactivity in comparison to their powdery counterparts in slurry mode [START_REF] García-Muñoz | Synergy Effect Between Photocatalysis and Heterogeneous PhotoFenton Catalysis on Ti-Doped LaFeO3 Perovskite for High Efficiency Light-Assisted Water Treatment[END_REF] , with 4-CP conversions remaining lower than 15% after 180 min of test. However, the incorporation of titanium within the LFO network leads to a faster 4-CP degradation, as evidenced by the increase in the apparent kinetic rate constants from 5 x 10 -4 min -1 for the non-modified LFO/β-SiC foam up to 7

x 10 -4 min -1 and 8 x 10 -4 min -1 for the P25-LFO/β-SiC and the SG-LFO/β-SiC foam catalysts, respectively. Accordingly, the 4-CP conversion after 180 min increases from 6% to 11% and 14%, respectively. This is accompanied by a slight improvement of the rate constant of 4-CP mineralization from 8 x 10 -4 to 3.1-4.1 x 10 -3 mgL -1 min -1 for the Tisubstituted foam catalysts, although low TOC conversions of 5% were achieved after 180 min of reaction in the best case. The enhancement of the reaction rates upon Ti substitution is similar to that observed on Ti-substituted LFO powders in the slurry mode.

In the case of the powders, the superiority of La1-xTixFeO3 in pure photocatalysis was associated to the enhanced availability of the photogenerated charge carriers, as evidenced by fluorescence analysis [START_REF] García-Muñoz | Synergy Effect Between Photocatalysis and Heterogeneous PhotoFenton Catalysis on Ti-Doped LaFeO3 Perovskite for High Efficiency Light-Assisted Water Treatment[END_REF] . It must be stressed that the low reaction rates and the low TOC conversions confirm that pure photocatalytic reaction as single mineralization process does not contribute significantly to the high initial reaction rates observed in the combined AOPs process. by more than three orders of magnitude (Figure 7D). The concentration of the released iron in solution drastically decreases from 2.5 mgL -1 in the case of the LFO/β-SiC foam catalyst down to the negligible level of 0.05 mgL -1 and further down to a non-detectable level (below 0.001 mgL -1 , i.e. corresponding to 0.00008% relative to the iron inside the LFO structure) for the P25-LFO/β-SiC and SG-LFO/β-SiC foam catalysts, respectively.

This stability increase of the immobilized β-SiC foam catalysts is similar to that observed with the powdery LFO catalysts upon Ti ® La cationic substitution, in both cases the stability enhancement being greater with amorphous dried titania as titanium source than with crystallized Aeroxide P25 [START_REF] García-Muñoz | Synergy Effect Between Photocatalysis and Heterogeneous PhotoFenton Catalysis on Ti-Doped LaFeO3 Perovskite for High Efficiency Light-Assisted Water Treatment[END_REF] . In contrary to the un-modified LFO/β-SiC foam, the drastic enhancement of the catalyst robustness observed for the SG-LFO/β-SiC foam, and the absence of any detectable Fe in solution, demonstrate that the SG-LFO/β-SiC foam catalyst operates through pure heterogeneous surface reactions without any homogeneous contribution.

Consequently, here the apparent kinetic rate constants for H2O2 decomposition and for 4-CP and TOC conversion are ascribed to purely heterogeneous surface mechanisms. The times required for the complete abatement are 150 min with P25-LFO/β-SiC and 120 min with SG-LFO/β-SiC, with 4-CP oxidation rates of 0.019 min -1 and 0.036 min -1 , respectively. Figure 7B reveals the existence of two consecutive mineralization rates, no matter the supported LFO phase was modified or not with titanium; the first one is attributed to the initial combined photo-CWPO/photocatalytic reaction with fast apparent kinetic rate constants, while the second contribution, slower, is ascribed to pure photocatalysis after almost complete H2O2 depletion. The initial apparent kinetic constants with Ti-modified LFO/β-SiC foams are lower than that obtained with the LFO/β-SiC foam, probably because they do not contain any homogeneous contribution.

Independently of the titanium incorporation, the β-SiC foam supported catalysts display a similar apparent kinetic constant in the second part of the process, at about 0.021 ± 0.002 mgL -1 min -1 , with no significant differences in terms of activity. As a result, the SG-LFO/β-SiC foam catalyst reaches complete 4-CP mineralization within 180 min with no release of Fe to the solution operating through a fully heterogeneous process.

The enhancement of both performance and robustness of the catalyst upon the modification by titanium of the immobilized LFO catalyst, together with the Ti-modified LaFeO3 catalyst characterization results, support the hypothesis that implementing the titanium-modified Pechini sol-gel synthesis in-situ at the surface of the β-SiC foam allows to preparing highly efficient La1-xTixFeO3 dual catalysts with combined heterogeneous photo-Fenton and photocatalytic activity, as in the case of the bulk powder catalyst counterparts. It can in consequence be hypothesized that the optimized SG-LFO catalyst immobilized on the β-SiC foams possesses a Ti content of ca. 4 at.% by analogy with its powdery counterpart. Therefore, the performance improvement upon titanium modification of the immobilized LaFeO3 catalyst is proposed here to find its origin in the same phenomena than for powdery catalysts. It is consequently attributed to both the enhanced availability of the photogenerated charge carriers at the surface and the electronic enrichment of the surface Fe upon the partial Ti ® La substitution, as evidenced by both fluorescence and surface analysis [START_REF] García-Muñoz | Synergy Effect Between Photocatalysis and Heterogeneous PhotoFenton Catalysis on Ti-Doped LaFeO3 Perovskite for High Efficiency Light-Assisted Water Treatment[END_REF] . The enhanced availability of the photogenerated charge carriers is proposed to allow a faster decomposition of H2O2 to HO°x radicals (Eqs. 2-4), and a more efficient generation of OH° radicals from adsorbed water (Eq. 5). # * + ; -) -→ ;)°+ ); * [Eq.3]

ℎ % + ; -) -→ ;))°+ ; % [Eq.4] ℎ % + ; -) → ;)°+ ; % [Eq.5]
The combined AOPs-induced synergy enables the immobilized La1-xTixFeO3 dual catalyst (i) to operate mainly as photo-CWPO catalyst at the beginning of the process, so that high reaction rates can be obtained, and (ii) to act as photocatalyst for mineralizing the short chain carboxylic acids and in consequence for hindering the formation of stable Fe complexes responsible for the slower kinetics and the catalyst deactivation observed in pure Fenton-like processes. a extrapolated from Figure 6 and from the associated apparent kinetic rate constant b extrapolated from Figure 7 and from the associated apparent kinetic rate constants shown in Table 2 c TOC evolution curve for the P25/β-SiC foam shown in Figure S6 Table 3 collects the ξ photonic efficiencies obtained for both 4-CP degradation and mineralization for the different catalysts and the two types of reaction (dual photo-CWPO/photocatalysis and pure photocatalysis). Given the impossibility of determining all the reaction intermediates and, hence, of knowing the number of holes consumed in the oxidation reactions at any reaction time, the time needed for total mineralization was extrapolated in the cases where total mineralization ([TOC]= 0) was not achieved within the test duration, considering that the TOC disappearance rate follows zero-order kinetics and should therefore be independent of [TOC] throughout the reaction. The obtained efficiencies for pure photocatalytic reactions using Ti-LFO/β-SiC foams are in the range of previously reported values for 4-CP mineralization, [START_REF] Lee | The P25 TiO2/4-Chlorophenol Photocatalytic System: Spectral Sensitivity or Lamp Artefact?[END_REF][START_REF] Theurich | Photocatalytic Degradation of 4-Chlorophenol in Aerated Aqueous Titanium Dioxide Suspensions: A Kinetic and Mechanistic Study[END_REF] with photonic efficiencies for degradation and mineralization of 4-CP of about 0.2% and 1%, respectively. [START_REF] Eisenberg | Colorimetric Determination of Hydrogen Peroxide[END_REF][START_REF] García-Muñoz | Evaluation of Photoassisted Treatments for Norfloxacin Removal in water using Mesoporous Fe2O3-TiO2 Materials[END_REF] By contrast, the photonic efficiency for 4-CP degradation strongly increases with the dual photo-CWPO/photocatalysis process, up to 9.38% and for the SG-LFO/β-SiC and the P25-LFO/β-SiC foam catalysts, respectively. Further, far higher photonic efficiencies for 4-CP mineralization are achieved using the dual catalysts, namely 37.6% and 22.6%

for the SG-LFO/β-SiC and the P25-LFO/β-SiC foam catalysts, respectively, that in both cases strongly outperform the P25/β-SiC foam reference value, i.e. 14.6%.

The substitution of the suspended powdery catalyst in slurry mode by its β-SiC foam immobilized counterpart obviously results in a loss in efficiency of the combined photo-CWPO/photocatalytic process for treating water. This can be quantified by defining an immobilization parameter, that normalizes the initial 4-CP mineralization rate obtained with the β-SiC foam supported catalyst relatively to that achieved using the suspended powdery counterpart. It must be said that this parameter is only relevant for rates associated to pure or quasi-pure heterogeneous surface reactions. Considering the water treatment efficiency in the slurry mode detailed in Garcia-Muñoz et al. [START_REF] García-Muñoz | Synergy Effect Between Photocatalysis and Heterogeneous PhotoFenton Catalysis on Ti-Doped LaFeO3 Perovskite for High Efficiency Light-Assisted Water Treatment[END_REF] and recalled in Supporting Information (Figure S7, Table S2), immobilization parameters of 0.49 and 0.43 were observed with P25-LFO/β-SiC and SG-LFO/β-SiC catalysts, respectively. In the case of the SG-LFO/β-SiC catalyst, the immobilization parameter can also refer to the extension of the treatment duration necessary to achieve full 4-CP mineralization, from 90 min to 180 min upon immobilization, giving an immobilization parameter of 2. Both parameters highlight that ca. 50% of the water treatment efficiency is maintained when operating in this up-scalable foam-based immobilized configuration in comparison to the slurry mode, using the same amount of H2O2, what is very encouraging for improving the viability of the photoassisted process. Obviously, it must be said that 0.564 g and 0.552 g of SG-LFO and P25-LFO active phase were respectively used on the β-SiC foams, compared to 0.05 g in the case of the powder suspensions that operate in optimal conditions at a 0.5 g/L concentration, so that 4.4% and 3.8% of the intrinsic activity of the catalysts is preserved upon immobilization (averaged over the entire volume of the foam/reactor).

Influence of the irradiance on the activity of the SG-LFO/β-SiC foam in the combined process

Taking into account the light transmission profile across the alveolar β-SiC foam (Figure 1B), the number of photons received by the catalyst is lower as we move towards the core of the foam volume [START_REF] Masson | β-SiC Alveolar Foams as a structured Photocatalytic Support for the Gas Phase Photocatalytic Degradation of Methylethylketone[END_REF] . Consequently, while the external surface of the foam catalyst operates in optimum lighting conditions with an incident irradiance of 60 W m -2 , the catalyst clearly deviates from those conditions as it localizes closer to the foam core, and gradually operates via a dark-CWPO process. Figure 8 shows the influence of the incident UV-A irradiance, within the 60-240 W m -2 range, on the evolution with time of the main reaction parameters, as well as on the different apparent kinetic rate constants for the combined photo-CWPO and photocatalytic degradation of 4-CP over the SG-LFO/β-SiC foam catalyst. Increasing the irradiance from 60 Wm -2 to 90-120 Wm -2 strongly increases the different apparent kinetic rate constants till reaching a plateau for higher irradiances, with a consequent reduction of the time needed to achieve full 4-CP and TOC conversion, down to 75 min and 90 min, respectively. This correlates with the maximum rate of H2O2 decomposition obtained for irradiances higher than 120 Wm -2 . The profile with increasing irradiance is suggested to result from the direct influence of the irradiance on the H2O2 decomposition rate, that was reported by Carra et al. to be irradiance-limited at low irradiance and iron-limited at higher irradiance [START_REF] Carra | Phenomenological Study and Application of the combined Influence of Iron Concentration and Irradiance on the Photo-Fenton process to Remove Micropollutants[END_REF] . In their study, the authors observed UV-light saturation within the 5-15 Wm -2 range depending on the light path length (5-10 cm), while several works report that increasing the UV light irradiance linearly increase both the H2O2 and the pollutant decomposition rates when a photo-Fenton catalyst operates in irradiance-limited conditions [START_REF] Lee | Influence of various Reaction Parameters on 2,4-D Removal in Photo/ferrioxalate/H2O2 Process[END_REF][START_REF] Tokumura | UV Light assisted Decolorization of Dark Brown colored Coffee Effluent by Photo-Fenton Reaction[END_REF] . In consequence, here the catalyst performance benefits from the possibility to increase the kinetic rate constants in the under-irradiated core areas of the foam catalyst, which are considered to operate in irradiance-limited conditions, while the reaction rates are iron-limited on the external surface of the foam independently of the irradiance level.

Stability and reusability of the SG-LFO/β-SiC foam catalyst

The stability and reusability of catalysts are necessary key-properties for water treatment, so that reusability tests with sequential runs were performed with the most active SG-LFO/β-SiC foam catalyst. Fig. 9 and Table 2 demonstrate the ability of the foam catalyst to be reused, complete 4-CP elimination being achieved after 120 min over at least 4 reaction cycles with no significant change in the pseudo kinetic rate constants, at 0.036 ± 0.001 min -1 . Similar initial 4-CP mineralization rates of 0.138 ± 0.004 min -1 are also maintained, while the mineralization rate assigned to pure UV-A photocatalysis at the end of the test is also not altered, at 0.023 ± 0.001 mgL -1 min -1 . Only a slight decrease in the mineralization degree obtained after 180 min of reaction is observed from 100% to 96.5% after the 4 th cycle. What is more, the leached iron to the solution was followed during the time-course of the reaction, and remained below the detection threshold (i.e. lower than 0.00008% relative to the catalyst Fe content). This demonstrates the robustness of the immobilized SG-LFO/β-SiC foam catalyst, that can be reused in a plug-and-play mode while continuously operating through pure heterogeneous surface reactions without any homogeneous contribution. Table S2: Apparent kinetic rate constants Synthesis protocols for pristine LFO and both Ti-substituted P25-LFO and SG-LFO catalysts as powders

The European Fund for regional development (EFRE/FEDER) is thanked for funding the project PHOTOPUR which is performed in the frame of the Interreg V program and the Offensive Sciences call. T. Dintzer (ICPEES) is thanked for performing SEM characterization.

The following graphic will be used for the TOC (images are original and were created by the authors of the article

Table S2: Apparent kinetic rate constants

Photonic efficiencies

In the first case, only the first electron (or hole) transfer was considered, so that the photonic efficiency was calculated as:

𝜉 "#$% (%) = + ,-./ 0 × 100 [Eq. S1]
where: ξ4-CP: photonic efficiency for 4-CP oxidation r4-CP: reaction rate for 4-CP oxidation ([molecules] s -1 )

F : photon flux ([photons] s -1 )
Although the degradation of 4-CP follows a complex mechanism, [1] it can be assumed that every electron withdrawn in the oxidation path down to CO2 arises from an effectively utilized electron-hole pair upon photon absorption by the photocatalyst. [2] This can happen by direct reaction with a photo-hole, by mediation of a hydroxyl radical, For each of the two lamps used, assuming that the irradiance is constant along the lamp length, the photon flux F was calculated (i) from the irradiance measurements recorded at the external wall and the center of the reactor, considering that the irradiance decreases with the square of the distance from the light source, and (ii) taking into account that the foam support transmits light as determined experimentally in Figure 1 and expressed following a first order decreasing exponential model as a function of the foam radius L (Eq.S3).

𝐼 = 𝐼 B × 𝑒 #D/B."G [Eq. S3]
where I and I0 are the transmitted and incident light, respectively, and L is the radial distance in cm from the external surface of the foam (i.e. L= 0 and L= 2.5 corresponding to the external surface and the center of the foam, respectively).

Considering this, the foam is virtually discretized as the sum of 100 concentric cylinders of increasing radius, and the photon flux F is obtained by numerically integrating (Figure S1) the irradiance at the external surface of those cylinders, giving a value of 7.491 × 10 16 (photons) s -1 .

[1] Theurich, J.; Lindner, M.; Bahnemann, D. W. Photocatalytic Degradation

Figure S4

The theoretical variation of the peak intensities was computed for characterizing the

Figure 1 :

 1 Figure 1: (left) Optical images of (A) the bare β-SiC foam support, (B) the LFO/β-SiC

Figure 2 :

 2 Figure 2: SEM images of (A-B) the bare β-SiC foam, (C-D) the LFO/β-SiC foam with

Fig. 3

 3 Fig. 3 shows the XRD patterns of the bare β-SiC foam support and of the different

Figure 3 :

 3 Figure 3: XRD patterns of the bare β-SiC foam support and of the different β-SiC foam

  a determined from the XRD analysis by applying the Scherrer equation to the three main diffraction peaks of the LaFeO3 structure (JCPDS Card 070-7777), with the classical assumption of spherical crystallites, taking into account the intrinsic broadening of the peaks due to the instrumentation.

Fe

  leached at 180 min and TOC conversion at 180 min. Conditions: [4-CP]0 = 25 mg/L; [H2O2]0 = 125 mg/L; T=25°C; UV-A irradiance of 60 W m -2 . Catalyst k'4-CP (min -1 ) k1'TOC (mg/Lmin) a k2'TOC (mg/Lmin) b k'H2O2 (min -1 ) XTOC (%) Fe leached (mg/L)

4 3. 2 . Catalytic activity 3 . 2 . 1 .

 42321 d[Fe] after 360 min of test e XTOC after 180 min was 96% for the test#Optimization of the catalyst concentration on the β-SiC foam In a first step, the non-modified LaFeO3 material was used as reference catalyst for optimizing the amount of catalyst immobilized on the foam surface in terms of activity in the combined photo-CWPO/photocatalysis process and the evolution with time under irradiation of the main features followed during the reaction is depicted in Fig.4. First, uncoated β-SiC foams does not reveal any catalytic activity under UV-A light, neither in the presence or absence of H2O2 as oxidant. Independently of the LFO content, the β-SiC supported LFO catalysts displayed the ability to decompose H2O2 in a typical photo-Fenton reaction. The low-loaded 5-LFO/β-SiC catalyst led to a total depletion of H2O2 in 240 min, with a quasi-complete 4-CP degradation and a mineralization degree of 68% after 360 min of reaction. Both the 10-LFO/β-SiC and 20-LFO/β-SiC catalysts decomposed H2O2 faster than their 5-LFO/β-SiC counterpart, so that complete H2O2 decomposition was achieved after 120 min of test in both cases. This faster decomposition correlated with both faster degradation and mineralization of 4-CP observed for both catalysts, and complete 4-CP degradation was obtained after about 150 min, while a TOC conversion of about 90% was achieved after 180 min.

Figure 4 :

 4 Figure 4: Evolution with time under irradiation of (A) the relative 4-CP concentration,

Figure 5 :

 5 Figure 5: Influence of the LFO content in the LFO/β-SiC foam catalyst on the kinetic

Figure 6 : 3 . 3 . 3 .Figure 7

 63337 Figure 6: Time-evolution of both the C/C0 and TOC/TOC0 relative concentrations during

Figure 7 :

 7 Figure 7: Evolution with irradiation time of (A) the relative 4-CP concentration, (B) the

Figure 8 :

 8 Figure 8: Influence of the UV-A irradiance on the evolution with time under irradiation

Figure 9 :

 9 Figure 9: Catalyst recycling efficiency expressed in terms of time-evolution of both (A)

  Figure S1: Discretization of the foam surface into cylinders of increasing radius from the

Figure S2 :

 S2 Figure S2: (A) N2 adsorption-desorption isotherms and (B) pore size distribution of the

Figure S3 :

 S3 Figure S3: Observed (black), calculated (orange full line), and difference (black full line)

Figure S4 :

 S4 Figure S4: (A) Simulated normalized intensity Ihkl(LFO)/I112(LFO) and (B) its relative

Figure S5 :

 S5 Figure S5: XPS profiles recorded on both the SG-LFO/β-SiC foam and the SG-LFO

Figure S6 :

 S6 Figure S6: Time-evolution of both the C/C0 and TOC/TOC0 relative concentrations

Figure S1 :

 S1 Figure S1: Discretization of the foam surface into cylinders of increasing radius from the

Figure S2 :

 S2 Figure S2: (A) N2 adsorption-desorption isotherms and (B) pore size distribution of the

Figure S3 :

 S3 Figure S3: Observed (black), calculated (orange full line), and difference (black full line)

Figure S4 :

 S4 Figure S4: (A) Simulated normalized intensity Ihkl(LFO)/I112(LFO) and (B) its relative

Figure S5 :

 S5 Figure S5: XPS profiles recorded on both the SG-LFO/β-SiC foam and the SG-LFO

Figure S6 :Figure S7 :

 S6S7 Figure S6: Time-evolution of both the C/C0 and TOC/TOC0 relative concentrations

  or by reaction with a superoxide radical resulting from the extraction of a conduction band electron by oxygen. From a formal point of view, every 4-CP molecule converted to 6 molecules of CO2 has lost 26 electrons, which can therefore be translated into 26 effectively used photons. The photonic efficiency for mineralization, derived from TOC disappearance can thus be defined as: efficiency for 4-CP mineralization Ci : initial 4-CP concentration (mol L -1 ) V : reactor volume (L) NA : Avogadro number (mol -1 ) tminer : time for total mineralization, ie. to achieve [TOC]= 0 (s) F : photon flux (s -1 )

of 4 -

 4 Chlorophenol in Aerated Aqueous Titanium Dioxide Suspensions: A Kinetic and Mechanistic Study, Langmuir 1996, 12, 6368-6376. [2] Muñoz-Batista, M. J.; Kubacka, A.; Hungría, A. B.; Fernández-García, M. Heterogeneous Photocatalysis: Light-Matter Interaction and Chemical Efects in Quantum Efficiency Calculations. J. Catal. 2015, 330, 154-166.

Figure S3 Figure S3 .

 S3S3 Figure S3

  detectability and the sensitivity to structural Ti of some selected characteristic Bragg peaks of the LFO phase. Both features were assessed by representing the normalized intensities (Ihkl/I112) and their relative variations as a function of the Ti amount inserted within the structure, respectively, as shown in Figures S4A and S4B.

Figure S5 .

 S5 Figure S5. XPS profiles recorded on both the SG-LFO/β-SiC foam and the SG-LFO

Figure S6 . 2 .

 S62 Figure S6. Time-evolution of both the C/C0 and TOC/TOC0 relative concentrations

Figure S7 .

 S7 Figure S7. Evolution with time under irradiation of (a) the relative 4-CP concentration, (b) the relative TOC concentration and (c) the concentration of leached Fe in the solution during the combined photo-Fenton and photocatalytic degradation of 4-CP over the pristine LFO and both Ti-substituted P25-LFO and SG-LFO catalysts as powders. Conditions: [4-CP]0 = 25 mg/L; [H2O2]0 = 125 mg/L; T=25°C; [cat] = 0.5 g/L; UV-A

Table 1 .

 1 Some physico-chemical properties of the bare β-SiC foam support and of the different β-SiC foam supported LFO-based catalysts.

		β-SiC 5-LFO/β-SiC	10-LFO/β SiC	20-LFO/β-SiC P25-LFO/β-SiC SG-LFO/β-SiC	LFO b
	wt.% content of LFO	-	5	10	20	10	10	-
	BET specific surface	16.2	-	11.3	-	13.2	14.6	8
	area (m 2 /g)
	LFO mean crystallite	-	25	24	25	21	23	46
	size (nm) a
	Pore volume (mL/g)	0.107 -	0.081	-	0.090	0.096	0.014

Table 3 .

 3 Photonic efficiencies for mineralization and degradation of 4-CP obtained with the different catalysts and processes.

	Catalyst	Process	tminer (min)	ξ4-CP (%)	ξTOC (%)
	SG-LFO/β-SiC	Dual	180	9.38	37.6
		Photocatalysis	6097 a	0.21	1.11
	P25-LFO/β-SiC	Dual	300 b	4.95	22.6
		Photocatalysis	8064 b	0.18	0.84
	P25/β-SiC	Photocatalysis	463 c	5.13	14.6

Table S1 :

 S1 Concentrations of the precursors in the aqueous impregnation solution or suspension used for the incipient wetness impregnation of the β-SiC foams. Synthesis of the amorphous titania precursor.

	Supporting Information SI2: Advanced X-ray diffraction (XRD) recording
	Supporting Information SI3: Photonic efficiencies
	Supporting Information SI4: Synthesis protocols for pristine LFO and both Ti-
	substituted P25-LFO and SG-LFO catalysts as powders.

Table S2 .

 S2 Apparent kinetic rate constants of 4-CP oxidation and mineralization derived from the time-evolution of the 4-CP and TOC concentrations, and concentration of Fe leached at the end of the test. Data taken from Garcia-Munoz et al. and Tableadaptedwith permission from RSC[1].

	Catalyst	k(4-CP), min -1	r0(TOC), mg L -1 min -1	[Fe] leached, mg L -1
	LFO	0.020	0.12	0.5
	P25-LFO	0.017	0.18	0.05
	SG-LFO	0.033	0.28	<0.001

[1] García-Muñoz, P.; Fresno, F.; Lefevre, C.; Robert, D.; Keller, N. Synergy Effect Between Photocatalysis and Heterogeneous PhotoFenton Catalysis on Ti-Doped LaFeO3 Perovskite for High Efficiency Light-Assisted Water Treatment, Catal. Sci. Technol. 2020, 10, 1299-1310.

Funding Sources

Funding from European Fund Interreg V program. ACKNOWLEDGMENT

AUTHOR INFORMATION

Corresponding Authors * patricia.gmunoz@upm.es ; nkeller@unistra.fr

Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Patricia García-Muñoz performed all experimental work.

Supporting Information

Ti

Synthesis of the amorphous titania precursor:

The amorphous titania material was synthesized according to a sol-gel method under basic conditions using TTIP as precursor. In a typical synthesis, 17.8 g of TTIP was first added to a 40 mL ethanolic solution at room temperature, before a similar volume of water was added dropwise to the solution. After rectification of the pH to 9 by adding ammonia (Carlo Erba, 30% aqueous solution), the solution was left under agitation at room temperature until a dry paste was obtained. The resulting powder was further dried at 100°C for 12 h.

Supporting Information SI2 Advanced X-ray diffraction (XRD) recording

Advanced XRD recording was carried out on a Bruker D8 Discover diffractometer using a monochromatic copper radiation source with a scan step of 0.02°, and equipped with a LynxEye XE-T detector, a motorized anti-scatter screen and a Si low background sample holder for minimizing as much as possible the background noise. The Rietveld structural refinement of the SG-LFO/β-SiC foam pattern was performed with the Fullprof

Supporting Information SI4

Synthesis protocol

Powdery La1-xTixFeO3 catalysts were obtained by modifying a sol-gel Pechini synthesis.

The synthesis method has been described in Garcia-Munoz et al. [1] by using two titania with distinguished crystal size and properties as titanium precursors.

The reference titanium-free LaFeO3 was labelled as LFO, while the Ti-modified LaFeO3 catalysts were labelled as P25-LFO and SG-LFO when using Aeroxide© TiO2

P25 and dried amorphous titania as titanium sources, respectively. Regardless of the titanium source, the titanium added during the Pechini synthesis corresponded to a nominal amount of 10 wt% in terms of TiO2 with respect to the theoretical amount of LaFeO3 orthoferrite obtained.