# Synergistic pharmaceutical interactions with nanoscale iron nitrides and natural organic matter

Veronika Veselská, Josef Kašlík, Diego Baragaño, Anaëlle Simonneau, Thomas Thiebault, Martin Petr, Jan Filip, Jean-Sébastien Moquet, Gildas Ratié

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Veronika Veselská, Josef Kašlík, Diego Baragaño, Anaëlle Simonneau, Thomas Thiebault, et al.. Synergistic pharmaceutical interactions with nanoscale iron nitrides and natural organic matter. The Chemical Engineering Journal, 2025, 523, pp.168285. 10.1016/j.cej.2025.168285. insu-05246516v2

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# Synergistic pharmaceutical interactions with nanoscale iron nitrides and natural organic matter

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Veronika Veselská<sup>a,*</sup>, Josef Kašlík<sup>a</sup>, Diego Baragaño<sup>b</sup>, Anaëlle Simonneau<sup>c</sup>, Thomas Thiebault<sup>d</sup>, Martin Petr<sup>a</sup>, Jan Filip<sup>a</sup>, Jean-Sébastien Moquet<sup>c</sup>, Gildas Ratié<sup>c,e,**</sup>

## ARTICLE INFO

### Keywords:

- Fe-based nanoparticles
- Dissolved organic carbon
- Environmental nanotechnology
- Water remediation
- Colloidal interactions
- Pharmaceutical's removal

## ABSTRACT

Understanding how natural organic matter (NOM) shapes the environmental fate of reactive iron nitride nanoparticles (nFeN) is key to advancing sustainable remediation technologies. This study investigates the behavior and interactions of novel nFeN, and conventional nanoscale zero-valent iron (nZVI), in complex and contrasting real-world aquatic environments: the pristine, organic-rich La Guette peatland and the wastewater-impacted Egoutier urban watershed in France. The study mainly focuses on their interplay with NOM and emerging pharmaceuticals (PPs). Field aging of nFeN produced mainly magnetite, akaganeite, and chukanovite (up to 31, 21, and 47 wt%, respectively), with site-specific mineral profiles shaped by DOC type, hydrodynamics, and microbial activity. Regarding PPs, under higher-flow conditions, nFeN outperformed nZVI, combined with DOC, retaining up to 96 ng g⁻¹ venlafaxine, 83 ng g⁻¹ oxazepam, 51 ng g⁻¹ carbamazepine, 44 ng g⁻¹ diazepam, 17 ng g⁻¹ metoprolol and paracetamol, and 13 ng g⁻¹ tramadol. Elevated log Kd (solid-liquid partition coefficient) values relative to log Koc (organic carbon to water partition coefficient) and log Kow (octanol-water partition coefficient) indicated that (i) interaction with NOM need to be considered for evaluating the PPs association with both Fe-based nanoparticles (NPs) and (ii) electrostatic interactions and ion exchange, rather than hydrophobicity, dominate cationic PPs binding by NPs. These findings highlight nFeN as a structurally robust yet environmentally responsive material for PP retention. The dataset also provides a valuable benchmark for designing nanocomposites incorporating nFeN, enabling evaluation of how porous supports alter its intrinsic performance under field conditions.

## 1. Introduction

The growing use of pharmaceutical products (PPs) and other synthetic organics poses rising environmental and health concerns. These persistent compounds often undergo transformation and are not fully removed by conventional wastewater treatment, leading to their release

into surface waters or accumulation in sludge. Environmental contamination can promote antibiotic resistance, disrupt aquatic ecosystems, and complicate water reuse and sludge valorization. Given their longevity and mobility, PPs are increasingly recognized as emerging pollutants, prompting European environmental policy to prioritize stricter regulation, enhanced monitoring, and the development of

**Abbreviations:** DOM, dissolved organic matter; DOC, dissolved organic carbon; EDS, energy-dispersive X-ray spectroscopy; GEACOS, granulometric passive capture of dissolved organic matter & sediment; nFeN, nZVI-based nitrides; NOM, natural organic matter; NPs, Fe-based nanoparticles; nZVI, nanoscale zero-valent iron; PPs, pharmaceutical products; SEM, scanning electron microscopy; XPS, X-ray photoelectron spectroscopy; XRD, X-ray Powder Diffraction.

* Corresponding author.

** Correspondence to: G. Ratié, Czech Advanced Technology and Research Institute, Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc, Šlechtitelů 27, 783 71, Olomouc, Czech Republic and Nantes Université, Univ. Angers, Le Mans Université, CNRS, Laboratoire de Planétologie et Géosciences LPG UMR 6112, F-44000, Nantes, France.

E-mail addresses: veronika.veselska@upol.cz (V. Veselská), gildas.ratie@univ-nantes.fr (G. Ratié).

<footnote><sup>a</sup> Czech Advanced Technology and Research Institute, Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc, Šlechtitelů 27, 783 71, Olomouc, Czech Republic</footnote>

<footnote><sup>b</sup> Instituto Geológico y Minero de España (IGME-CSIC), Matemático Pedrayes 25, 33005, Oviedo, Spain</footnote>

<footnote><sup>c</sup> ISTO, UMR 7327, Univ Orleans, CNRS, BRGM, OSUC, F-45071, Orléans, France</footnote>

<footnote><sup>d</sup> METIS, Sorbonne Université, EPHE, Université PSL, CNRS, UMR 7619, 75005, Paris, France</footnote>

<footnote><sup>e</sup> Nantes Université, Univ. Angers, Le Mans Université, CNRS, Laboratoire de Planétologie et Géosciences LPG UMR 6112, F-44000, Nantes, France</footnote>
advanced treatment technologies [1–4].

In this context, rapidly advancing nanotechnology is a game-changer and proactive measure that aligns perfectly with anticipated regulatory changes. Innovative nanomaterials including metal-organic frameworks, carbon-based hybrids, metal(oxide) nanocomposites and 2D layered structures demonstrate high efficiency in PPs adsorption and photocatalytic degradation [5,6]. Among them, nanoscale zero-valent iron (nZVI) and its modified derivatives stand out for their dual adsorption and catalytic capabilities, including reductive degradation of PPs [7,8]. Surface-engineered and composite-supported nZVI systems significantly outperform pristine forms in removing a wide range of drugs and micro-pollutants, representing a promising direction in sustainable water remediation aligned with future EU standards [9–11].

Furthermore, innovative research within this domain has led to the development of nZVI-based nitrides (nFeN), showcasing their effectiveness in the removal of chlorinated contaminants [12–14]. Although laboratory studies have investigated their mobility in porous media, and reactivity and aging in simulated groundwater [15,16], nFeN remains largely unexplored for PPs removal, despite its promising properties such as high stability, magnetism, and reactivity. However, when embedded in biochar, nFeN has demonstrated catalytic effectiveness for PPs removal in water [17].

Environmental complexity underscores the critical role of natural organic matter (NOM) in shaping the reactivity, efficiency, and toxicity of nFeN and nZVI. NOM, often in the form of dissolved organic matter (DOM), can enhance or hinder pollutant adsorption, promote microbial degradation, or stabilize contaminants via complexation [18,19]. Interactions between nZVI and humic substances affect colloidal stability through mechanisms like charge repulsion or bridging [20,21]. These effects are influenced by NOM's type, charge, concentration, and hydrophobicity, which alter nZVI aggregation and DOM behavior [22–24]. Although NOM can both support and inhibit contaminant removal, its synergy with nZVI or nFeN offers potential for improved PPs remediation.

The primary aim of this study was to investigate and gain a deeper understanding of the behavior and interactions of novel nFeN in complex, real-world aquatic environments, with a focus on their interaction with emerging PPs and NOM. Iron nitrides were compared to nZVI, a well-established material in groundwater remediation. A dual approach was used, combining laboratory experiments with DOC and on-site applications, to examine how NOM influences the properties, aging, and performance of nFeN, revealing significant advantages over nZVI. Our findings underscore the critical role of NOM in modulating the reactivity of nFeN, highlighting its enhanced potential for the rational design of advanced nanocomposites, thereby paving the way for more efficient and targeted environmental remediation technologies aimed at removing emerging contaminants.

## 2. Material and methods

### 2.1. nFeN preparation and characterization

The nFeN was synthesized by incorporating atomic nitrogen throughout the entire volume of nZVI precursor (NANOFER 25P, purchased from NANO IRON s.r.o, Czech Republic), resulting in the formation of crystalline γ'-FeN nitride. The nitriding process utilized a gas mixture of NH₃ and N₂ in a 1:2 ratio, flowing at 30 L h⁻¹, under controlled conditions of 500 °C and 0.5 bar for 3 h [12,13]. For comparative purposes, nZVI was employed as a control sample, and all experiments and applications were conducted on both nFeN and nZVI. Throughout the manuscript, the term "nanoparticles (NPs)" refers to both nZVI and nFeN collectively.

Due to their pyrophoric nature, both types of NPs were stored in a dry state within sealable metal containers under a protective nitrogen atmosphere at room temperature. Both NPs have been extensively documented and characterized in terms of morphology, phase composition,

crystallographic structure, and surface properties in our previous study [16]. For this study, we briefly summarize the most relevant physicochemical properties of the NPs in Table 1.

### 2.2. Field application

To investigate NPs interactions under natural conditions, we employed an innovative in situ approach using 3.5 kDa dialysis bags (Spectrum™ Spectra/Por™ 7). This setup enabled selective exchange with DOM while preventing NPs loss, minimizing potential environmental release risks. The chosen membrane size was optimal for humic and fulvic acids (0.5 to 5 kDa) [25], allowing extended field exposure without overloading the system with high-molecular-weight DOM. Each dialysis bag was filled with 25 mL of a NPs suspension at 5 g L⁻¹, securely sealed, clamped, and enclosed in a protective safety net before deployment. The selected dose of 125 mg of NPs per bag was chosen to ensure the minimum amount of material required for subsequent solid state analysis, and is consistent with previous migration and remediation studies [16,26].

NPs were applied in April 2022 at two distinct field sites: the La Guette peatland, representing a pristine environment monitored by the French National Observation Service for Peatlands (SNO Tourbières), and the Egoutier watershed, a contaminated suburban area included in the French National Observation Service for Urban Watersheds (SNO Observil) since 2020. The instrumented La Guette peatland (150 m a.s.l., 47°19′N, 2°16′E, 23 ha), represent an acidic (pH ~4.5), low-conductivity (<80 µS cm⁻¹) transitional poor fen located in the Sologne forest (Neuvy-sur-Barangeon, Cher, France), characterized by peat up to 180 cm thick (mean depth ~50 cm) and minimal human impact [27]. The Egoutier catchment is a small watershed in the Loire River basin near Orléans (Loiret, France), covering an area of 27 km². It collects water from rainfall and sewage water effluents from a Central Army Pharmacy and psychiatric hospital. This study focuses on the 8 km² upstream section of the catchment, specifically evaluating the effects of NPs application in the area where effluents from sewage networks are released [28,29] (Figs. 1, S1).

Depending on the locality, the dialysis bags were deployed either directly into the river, piezometer, or borehole, or placed inside the sediment trap to ensure stable positioning and controlled exposure. At La Guette peatland, the dialysis bags were placed in piezometers located downstream at application points LG1 and LG2, to study NPs behavior in subsurface water flow. Each piezometer held two identical bags: nFeN in LG1 and nZVI in LG2. For interactions with subsurface peat material, two dialysis bags either with nFeN or nZVI were inserted directly into a borehole at a depth of approximately 30 cm at application point LG3 (Figs. 1, S1, Table S1). The experimental setup at Egoutier watershed involved deploying dialysis bags containing NPs downstream of the psychiatric hospital's wastewater treatment plant discharge, targeting two hydrodynamic environments: a dynamic fluvial system at application point EG1 and a calmer lacustrine system near Beulie pond at the application point EG2. Notably, EG1 and EG2 correspond to long-term water quality monitoring stations EG23-12 and EG23-15 in the SNO Observil, respectively (Table S1). The dialysis bags were strategically placed within the sediment traps GEACOS (Granulometric Passive Capture of Dissolved Organic Matter & Sediment) [30]. GEACOS consists of up to six modular PVC cylinders (98 mm Ø × 200 mm length) separated by synthetic sieves with progressively smaller mesh sizes: 1 mm, 250 µm, 60 µm, 20 µm, 5 µm, and 0.45 µm (Fig. S2). One dialysis bag with nZVI and one with nFeN were placed in sections 1 (1 mm–250 µm) and 4 (20 µm–5 µm), to minimize membrane damage and pore clogging, and to examine the influence of colloid size on NPs interactions. This setup limited contact with larger suspended particles. In addition to GEACOS at the EG2, dialysis bags were secured to two wooden stakes, each holding one bag with nFeN and one with nZVI, and positioned approximately 30 cm below the water surface to ensure full submersion (Figs. 1, S1, Table S1). Three weeks post-application in May
<table><caption>**Table 1**

Characteristics of concentrated suspensions of nFeN and nZVI (250 g L⁻¹) in a ratio 1:4 (S/L = 5 g/20 mL).</caption><thead><tr><th rowspan="2">Method</th><th rowspan="2"></th><th colspan="5">XRD</th><th>BET</th><th>TEM</th><th colspan="2">DLS</th></tr><tr><th>α-Fe</th><th>Fe<sub>3</sub>O<sub>4</sub><sup>a</sup></th><th>FeO<sup>a</sup></th><th>γ'-Fe<sub>4</sub>N</th><th>ε-Fe<sub>3</sub>N</th><th>SSA (m<sup>2</sup> g<sup>-1</sup>)</th><th>Size ± RSD (nm)</th><th>Z-ave<sup>b</sup> (μm)</th><th>ζ<sup>b</sup> (mV)</th></tr></thead><tbody><tr><td rowspan="2">nFeN</td><td>RA (wt%)</td><td>2.3</td><td>n.d.</td><td>n.d.</td><td>96.9</td><td>0.8</td><td rowspan="2">19</td><td rowspan="2">67 ± 18</td><td rowspan="2">13.6</td><td rowspan="2">-0.13</td></tr><tr><td>MCL (nm)</td><td>68</td><td>n.d.</td><td>n.d.</td><td>42</td><td>46</td></tr><tr><td rowspan="2">nZVI</td><td>RA (wt%)</td><td>92.1</td><td>6.2</td><td>1.7</td><td>n.d.</td><td>n.d.</td><td rowspan="2">21</td><td rowspan="2">49 ± 13</td><td rowspan="2">97.3</td><td rowspan="2">-1.39</td></tr><tr><td>MCL (nm)</td><td>44</td><td>43</td><td>33</td><td>n.d.</td><td>n.d.</td></tr></tbody></table>

XRD: phase composition measured on wet samples, relative abundance of crystalline phases (RA), mean X-ray coherence length (MCL); BET: specific surface area (SSA); TEM: average size and relative standard deviation (RSD); DLS: intensity-weighted harmonic mean diameter size of a collection of particles (Z-Ave) and zeta potential (ζ).

n.d. = not detected.

a Unreduced residues of iron oxides from the preparation of nZVI.

b 10 times diluted.

<figure><img src="image_4.png" /><figcaption>**Fig. 1.** On-site implementation of nFeN and nZVI in dialysis bags at the Egoutier watershed (a, b) and La Guette peatland (c). Applications were conducted within the GEACOS at EG1 and EG2, with direct deployment in the accumulation pond at EG2, as well as in piezometers (LG1, LG2) and a borehole (LG3). GEACOS and pond setups are shown before and after immersion, while the borehole photo was taken just before backfilling.</figcaption></figure>

2022, the dialysis bags were retrieved, and the NPs suspension were transferred into a glass tube and subsequently passed through a 0.45 µm nylon filter in the laboratory for further analysis. Collected water samples were stored and analyzed for phase/chemical composition and physicochemical parameters (Table 2, Table S1).

## 2.3. Post-field application characteristics

### 2.3.1. Solid state characterization

The changes in phase composition of the NPs during the aging process within field applications were identified on dry-powder samples using X-ray Powder Diffraction (XRD) (Fig. S3). The samples were

measured employing Aeris diffractometer (Malvern PANalytical, Netherland) in parafocusing Bragg-Brentano geometry using iron filtered Co Kα radiation source and PixCell detector. The powder samples were prepared on zero-background Si slide and the diffraction patterns were captured in 2θ range from 5 to 105° (with step size 0.022° 2θ with total counting time 64 min for each pattern). Commercially available standards SRM640 (Si) and SRM660 (LaB₆) were used for evaluation of line positions, and instrumental line broadening, respectively. The data processing and Rietveld refinements were performed using HighScore Plus software (Malvern PANalytical, Netherland) in conjunction with PDF-5+ and ICSD databases.

Although crystalline phase quantification was performed using
<table><caption>**Table 2**

Environmental conditions in the waters at the studied localities on the day of NPs application (April 2022) and recovery (May 2022).</caption><thead><tr><th rowspan="3"></th><th colspan="4">La Guette peatland</th><th colspan="4">Egoutier watershed</th></tr><tr><th colspan="2">LG1</th><th colspan="2">LG2</th><th colspan="2">EG1</th><th colspan="2">EG2</th></tr><tr><th>Application</th><th>Recovery</th><th>Application</th><th>Recovery</th><th>Application</th><th>Recovery</th><th>Application</th><th>Recovery</th></tr></thead><tbody><tr><td>pH</td><td>4.4</td><td>5</td><td>4.5</td><td>5.8</td><td>7.6</td><td>7.7</td><td>7.2</td><td>8.1</td></tr><tr><td>σ (µS cm<sup>-1</sup>)</td><td>54.7</td><td>45</td><td>58</td><td>74</td><td>1427</td><td>1287</td><td>782</td><td>1448</td></tr><tr><td>O<sub>2</sub> (mg L<sup>-1</sup>)</td><td>3.5</td><td>6.0</td><td>7.4</td><td>5.8</td><td>6.8</td><td>/</td><td>5.6</td><td>3.3</td></tr><tr><td>T (°C)</td><td>21.6</td><td>20</td><td>15</td><td>18.3</td><td>12.6</td><td>21</td><td>13.6</td><td>25</td></tr><tr><td>redox (mV)<sup>a</sup></td><td>467</td><td>490</td><td>408</td><td>229</td><td>446</td><td>428</td><td>419</td><td>460</td></tr><tr><td>DOC (mg L<sup>-1</sup>)</td><td>/</td><td>26.8</td><td>/</td><td>16.9</td><td>/</td><td>10.3</td><td>/</td><td>7.1</td></tr><tr><td>TN (mg L<sup>-1</sup>)</td><td>/</td><td>1.0</td><td>/</td><td>&lt;LOD</td><td>/</td><td>16.7</td><td>/</td><td>1.7</td></tr><tr><td>PPs (charge)<sup>b</sup> (ng L<sup>-1</sup>)</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Diclofenac (−)</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>35</td><td>28</td><td>2</td><td>4</td></tr><tr><td>Ketoprofen (−)</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>17.7</td><td>9.8</td><td>&lt;LOD</td><td>&lt;LOD</td></tr><tr><td>Carbamazepine (0)</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>470</td><td>253</td><td>88</td><td>187</td></tr><tr><td>Diazepam (0)</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>120</td><td>171</td><td>92</td><td>225</td></tr><tr><td>Oxazepam (0)</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>432</td><td>522</td><td>104</td><td>275</td></tr><tr><td>Paracetamol (0)</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>5</td><td>2</td><td>2</td><td>2</td></tr><tr><td>Metoprolol (+)</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>4</td><td>3</td><td>3</td><td>2</td></tr><tr><td>Tramadol (+)</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>60</td><td>38</td><td>8</td><td>19</td></tr><tr><td>Venlafaxine (+)</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>61</td><td>45</td><td>6</td><td>10</td></tr></tbody></table>

<LOD = below limit of detection.

a Corrected from temperature.

b The symbols (−), (0), and (+) denote negative, neutral, and positive charge, respectively.

Rietveld refinement for all identified phases (Table S2), for clarity, the manuscript presents values normalized to iron-containing phases (Tables S2, S3). This normalization was calculated using the following equation:

$$RAN_i(\%) = \frac{RA_i(\%)}{\sum RA_j(\%)} \times 100, \quad (1)$$

where $RAN_i(\%)$ is the normalized relative abundance (in %) of the iron-containing phase $i$, $RA_i(\%)$ is the relative abundance (in %) obtained by Rietveld analysis from the quantification of all crystalline phases, and $\sum RA_j(\%)$ is the sum of relative abundances (in %) of all iron-containing phases obtained by Rietveld analysis.

Scanning electron microscopy (SEM; ThermoFisher Scientific, USA) coupled with energy-dispersive X-ray spectroscopy (EDX; ThermoFisher Scientific, USA) was employed to analyze the surface morphology and qualitative elemental composition of specific aging by-products of the NPs. The samples were analyzed by scanning electron microscopy using a SCIOS 2 instrument (ThermoFisher Scientific, USA) with an accelerating voltage of 5 kV. For these analyses, a powder was placed on an aluminum holder covered with carbon tape. Energy-dispersive X-ray spectroscopy (EDS) was performed using a Scios 2 DualBeam (ThermoFisher Scientific, USA) with an UltraDry silicon drift X-ray detector at an accelerating voltage of 15 kV.

The elemental composition of the NPs' surfaces was further characterized using X-ray photoelectron spectroscopy. The powder samples were fixed to a sample holder by double-sided tape (SCOTCH). The XPS measurements were carried out with the Nexsa G2 XPS system (Thermo Fisher Scientific) with monochromatic Al-Kα source and photon energy of 1486.7 eV. All the spectra were measured in the vacuum of $1.2 \times 10^{-7}$ Pa and at the room temperature of 20 °C. The analyzed area on each sample was spot of 400 µm in diameter. The survey spectra were measured with pass energy of 150.00 eV and electronvolt step of 1.0 eV while for the high-resolution spectra were used pass energy of 50.00 eV and electronvolt step of 0.1 eV. Charge compensation was used for all measurements. The spectra were evaluated with the Avantage 6.5.1 (Thermo Fisher Scientific) software.

### 2.3.2. Analysis of PPs

Mixture of nine PPs of interest were analyzed, in both the dissolved phase and the NPs-bound fraction after field application of NPs. PPs represent a range of diverse contaminants with a varied chemical

properties and therapeutic applications, including representatives of antihypertensives (metoprolol), analgesics (tramadol, paracetamol, diclofenac and ketoprofen), antidepressants (venlafaxine, oxazepam), anticonvulsants (carbamazepine) and anxiolytics (diazepam, oxazepam) which are present in waters collected at the studied localities (Table 2). Separation and quantification of the targeted PPs were performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Before PPs extraction, 50 ng of isotopically labeled internal standards (ILISs) were added to each sample and incubated overnight at 4 °C. Liquid samples (~4 mL) were dried at 70 °C under a gentle nitrogen flow and reconstituted in 350 µL of methanol (VWR). For solid phase, the NPs were sonicated in 1 mL of methanol, centrifuged at 5000 rpm for 10 min, and the supernatant was transferred to an injection vial, before drying under nitrogen flow and further reconstitution in 350 µL of methanol. All extracts were transferred to 2 mL amber glass vials and stored at -18 °C until analysis. Subsequently, a 10 µL aliquot was injected into an Agilent ULTIVO triple quadrupole mass spectrometer equipped with a Zorbax Eclipse Plus C18 column (2.1 mm × 150 mm, 3.5 µm; Agilent). Chromatographic separation was achieved at 40 °C, using a mobile phase consisting of 0.1 % v/v formic acid (99 % purity, Sigma-Aldrich) in ultrapure water (Pure Lab Chorus water purification system Veolia Water) and 0.1 % v/v formic acid in acetonitrile (VWR), with data acquisition and processing performed using Agilent Mass Hunter software. The analytical method was validated using spiked samples from LG samples, with recovery ratios determined for each pharmaceutical relative to its ILIS (detailed in Table S4). Quantification was performed using a 7-point calibration curve of standard solutions in MeOH, ranging from 1 to 500 µg L$^{-1}$. The distribution coefficient (Kd in L kg$^{-1}$) was determined as,

$$\log K_d = \log \left( \frac{c_{\text{solid}}}{c_{\text{aqueous}}} \right), \quad (2)$$

where $c_{\text{solid}}$ (ng kg$^{-1}$) and $c_{\text{aqueous}}$ (ng L$^{-1}$) represent the concentration of the PPs adsorbed onto the solid phase and remaining in solution within dialysis bag, respectively.

### 2.4. Laboratory evaluation of NPs interactions with DOM

As a complementary approach to the field application, kinetic batch experiments were conducted to evaluate the interaction between NPs and DOM. These experiments used a purified and well-characterized
humic acid (leonardite, IHSS) at initial DOC concentrations of 1, 5, 10, 20, and 50 mg L⁻¹, with NPs suspended at 1 g L⁻¹. Prior experiment, leonardite was dissolved at pH 9–10 by adding 1 mol L⁻¹ NaOH [31]. NPs were introduced at 1 g L⁻¹, as lower concentrations enhance DOM adsorption, improving stability and reducing aggregation [22], with a total suspension volume of 10 mL. The experiments were performed without pH control, under ambient laboratory conditions, with continuous agitation at 150 rpm using a multi-rotator (PTR-60, Grant Bio). Samples were collected at regular time intervals over month (20 min, 40 min, 1 h, 2 h, 1 day, and 1 month), filtered through 0.45 µm membranes, and analyzed for aggregate size, zeta potential, and pH. Dissolved organic carbon (DOC) was measured at the 2-day and 1-month sampling events using a carbon analyzer (TOC-L, Shimadzu). Prior to DOC measurements, all samples were filtered through 0.45 µm membranes and acidified with H₃PO₄.

## 3. Results

### 3.1. Aging of nFeN in diverse environmental contexts

Crystalline-phase quantification was normalized exclusively to Fe-bearing phases. Trace non-iron phases (quartz, kaolinite) observed in some dialysis bags most likely reflect ingress of suspended particulate matter from the bulk water due to minor membrane damage during retrieval, and CaCO₃ may also have precipitated under high-pH

conditions given the availability of Ca.

Thus, the in-situ aging of NPs under field conditions resulted in three primary by-products forming across all study sites: Fe oxides, Fe oxyhydroxides, and carbonates. The most prevalent phases identified were magnetite (Fe₃O₄), akaganeite (β-FeO(OH)), and chukanovite (Fe₂(CO₃)(OH)₂), while traces of metastable amakinite (Fe(OH)₂) were found exclusively in the La Guette peatland (Figs. 2, S3). In this study, the behavior of nFeN is the primary focus and will be consistently compared with nZVI to highlight their differences in oxidation resistance and by-products transitions. Overall, nFeN demonstrated superior oxidation resistance compared to nZVI, with higher γ'-Fe₄N retention across all application sites. In the La Guette peatland, γ'-Fe₄N was well-preserved, with 79 wt% retention in piezometer samples and 64 wt% in borehole samples. The dominant by-product was chukanovite, forming in amounts between 12 wt% and 47 wt%, while akaganeite remained below 7 wt%. In contrast, nZVI showed significantly lower stability, retaining only 33–46 wt% of unoxidized α-Fe. Its aging resulted in the formation of magnetite (26–36 wt%), chukanovite (20–23 wt%), and akaganeite (7 wt%). In the Egoutier watershed, Fe₄N retention varied depending on way of application. In the GEACOS, Fe₄N oxidation was more pronounced in section 1, where higher water flow led to 48–55 wt % retention of Fe₄N, while in section 4, lower water dynamics allowed for greater stability, with 82–83 wt% Fe₄N preserved (Figs. 2, S2). At EG2, 30 cm below the water surface, Fe₄N retention was the highest, ranging from 82 wt% to 97 wt%. In contrast, nZVI exhibited smaller

<figure><img src="image_5.png" /><figcaption>**Fig. 2.** Quantification of crystalline iron phases in the aged nFeN and nZVI in La Guette peatland (a), in GEACOS located at EG1 and EG2 (b), and in 30 cm below the water surface at EG2 (c). For nZVI, initial magnetite from production is included. Data at EG1 and EG2 are normalized to the relative abundance of Fe-containing phases. Sample labels with _1 and _2 indicate duplicates for LG1, LG2, and EG2.</figcaption></figure>
variations in residual α-Fe across sites, with retention ranging from 49 to 70 wt% in section 1, 70–79 wt% in section 4, and 70–74 wt% at EG2.

The oxidation by-products of nFeN and nZVI followed similar trends at EG1 and EG2, with magnetite and akaganeite as the dominant phases. The most significant oxidation for both NPs was observed in section 1 of GEACOS. For nFeN, magnetite accounted for 28–31 wt% and akaganeite for 17–21 wt%, whereas in section 4, their concentrations were both below 9 wt%. nZVI exhibited a comparable oxidation pattern, with magnetite decreasing from 21 to 31 wt% in section 1 to 17–22 wt% in section 4. Akaganeite reached up to 14 wt% in section 1 and 6 wt% in section 4. Unlike nFeN, nZVI occasionally produced chukanovite, which appeared in some dialysis bags at concentrations up to 6 wt%.

## 3.2. Interaction of nFeN with PPs – field application

The NPs aging by-products and their interactions with PPs was evaluated in the contaminated Egoutier watershed, with a focus on GEACOS compartments at EG1 and 30 cm below the water surface at EG2. Damage to the dialysis bags in GEACOS at EG2 led to the loss of essential data on dissolved material, limiting the analysis to retained pollutants. In general, the Egoutier water stream, heavily influenced by the discharge from a nearby psychiatric hospital, exhibited the highest concentrations of neutral PPs (oxazepam, diazepam, and carbamazepine), followed by cationic PPs (venlafaxine and tramadol) (Fig. S4, Table 2). Furthermore, sampling location EG1, closest to the PPs source, displayed higher PPs concentrations than downstream point EG2 (Fig. 1). Removal of PPs was quantified by evaluating their partitioning and retention within dialysis bags under pseudo-equilibrium conditions (Figs. 3, S4). Notably, retention patterns varied between nFeN and nZVI, with significant differences observed across the GEACOS compartments at EG1. Here, nFeN exhibited the highest uptake for a broader range of PPs in section 1. Here it showed the highest retention for venlafaxine (96 ng g⁻¹), followed by oxazepam (83.3 ng g⁻¹), carbamazepine (50.6 ng g⁻¹), diazepam (44.2 ng g⁻¹), and tramadol (13.4 ng g⁻¹). The nFeN also efficiently retained hydrophilic paracetamol (16.5 ng g⁻¹) and metoprolol (16.7 ng g⁻¹), whereas nZVI showed only minimal interactions. In contrast, nZVI exhibited the highest affinity for PPs in GEACOS section 4, with retention following the trend diazepam (38.1 ng g⁻¹), venlafaxine (24.9 ng g⁻¹), carbamazepine (24.3 ng g⁻¹) tramadol (10 ng g⁻¹) and paracetamol (5.4 ng g⁻¹) (Fig. 3). At EG2, where PPs concentrations were approximately twofold lower than at EG1, tramadol uptake was threefold greater with nFeN compared to nZVI, and carbamazepine exhibited more than twice the retention on nFeN than on nZVI. Similarly, venlafaxine and diazepam exhibited higher loadings on nFeN (76.13 ng g⁻¹ and 100.94 ng g⁻¹, respectively) than on nZVI (55.00 ng g⁻¹ and 96.30 ng g⁻¹, respectively). The lower uptake of metoprolol on nFeN (<LOD) compared to nZVI (1.42 ng g⁻¹) represents an exception, indicating compound-specific variability.

## 3.3. Interaction of NPs with DOC-batch experiments

Laboratory kinetic batch experiments using purified humic acid demonstrated that DOC actively interacts with NPs in suspension. The concentration of DOC significantly influences the temporal evolution of NPs aggregate size and zeta potential of the suspension. Although nFeN and nZVI exhibit slightly different trends in aggregate size reduction over time, both NPs ultimately form small aggregates (1–3 µm) after one month (Fig. 4). While a high DOC concentration initially promotes faster aggregate size reduction, its influence diminishes over time and becomes negligible. The zeta potential of the suspension is governed by the negative surface charges of both NPs and DOC, dominated by the deprotonation of acidic functional groups at humic acid concentration up to 10 mg L⁻¹ [32]. It primarily decreases with increasing DOC concentration. Over time, a slight increase in zeta potential is observed at low DOC concentrations, whereas higher DOC levels lead to a further decrease in zeta potential for both types of NPs. This trend is evident up

<figure><img src="image_6.png" /><figcaption>Fig. 3. PPs distribution expressed as solid-phase loadings (ng g⁻¹) and corresponding log Kd values for nFeN and nZVI at application sites. For EG2, the data refer to EG2-nFeN_2 and EG2-nZVI_2. The symbols (-), (0), and (+) following each PPs name indicate its charge: negative, neutral, and positive, respectively.</figcaption></figure>

to a DOC concentration of 1 mg L⁻¹ for nFeN and 5 mg L⁻¹ for nZVI. Evolution of zeta potential is also linked to changes in the suspension’s pH over time. Initially, the diluted suspensions of nFeN and nZVI exhibited alkaline pH values of 10.5 and 9.5, respectively, while the DOC solution (derived from leonardite) had a pH of 8.3 (Table S5). The initial pH of the suspensions was further influenced by the concentration of DOC used during batch experiment. Kinetic measurements showed that within the first hour, the pH of nFeN suspensions decreased, with a more pronounced drop observed at lower DOC concentrations (1–5 mg L⁻¹) compared to higher concentrations (10–50 mg L⁻¹). The pH values ranged from 7.3 at 1 mg L⁻¹ to 9.4 at 50 mg L⁻¹. In the case of nZVI, the starting pH was strongly influenced by the relative volume of added DOC solution. The pH variation within the first hour was more distinct, yet remained relatively stable across the DOC concentration range— from 7.2 at 1 mg L⁻¹ to 7.3 at 50 mg L⁻¹—indicating the inherently lower alkalinity of nZVI suspensions compared to nFeN.

Over time, both systems exhibited progressive acidification. After one month, the pH had decreased to approximately 6.7 for nFeN and 6.4 for nZVI (see Fig. S5 and Table S5). These findings highlight the importance of considering not only the DOC concentration and its chemical nature for field application but also the dynamic pH conditions when assessing DOC-nanoparticle interactions and their role in PPs removal.
<figure><img src="image_7.png" /><figcaption>Fig. 4. Size of aggregates and the zeta potential of nFeN (a, c) and nZVI (b, d) in solution over time at different DOC concentrations ranging from 0 to 50 mg L⁻¹.</figcaption></figure>

## 4. Discussion

### 4.1. Field performance of nFeN in relation to aging, interactions with PPs and DOC dynamics

Real-world application of nFeN revealed its improved reactivity and stability in situ, confirming its potential as a promising advanced nanomaterial for mitigating PPs contamination under environmentally relevant conditions. Compared with conventional nZVI, nFeN exhibited higher oxidative stability, persisting in a non-corroded state for days to weeks [13]. Even so, XRD and Fe 2p XPS spectra revealed pronounced aging over time, with loss of Fe⁰ and growth of Fe(II)/(III) oxides/oxy-hydroxides on the surface (Table S6). Likewise, nFeN performed better, showing broader and more consistent reductions in the concentrations of both neutral and cationic PPs. This superior performance was evident

even under lower contamination levels at EG2, where nFeN out-performed nZVI in removing venlafaxine, carbamazepine, tramadol and diazepam. However, nFeN reactivity varied across sites, demonstrating a strong dependence on local hydrodynamics and geochemical settings, which also governed its aging pathways (Table S7). In GEACOS section 1, higher flow rates led to greater oxidation of nFeN, yet coincided with enhanced PPs removal likely driven by increased oxygen exposure and shear-induced activation of fresh reactive surfaces [33–35]. This contrasts with nZVI, which performed better under slower flow conditions in GEACOS section 4, where it was less affected by rapid surface passivation or oxidative stress. This interplay between hydrodynamics and oxidative transformation underscores the need to evaluate NPs in realistic, site-specific scenarios.

Transformation by-products of both nFeN and nZVI reflected the local water typology (Fig. S6, Table S7). At the EG site with sodium
chloride-dominated water typology, abiotic oxidation favored the formation of akaganeite and magnetite [36,37]. Meanwhile, at the organic-rich La Guette peatland, characterized by acidic, poorly mineralized groundwater with negligible $HCO_3^-$ content, biotic processes supported the formation of chukanovite (Fig. S7). Although chukanovite is traditionally associated with alkaline, anoxic, and $HCO_3^-$-rich conditions [15,38], these results demonstrate that local dissimilatory iron-reducing bacteria such as Geobacter spp. and Anaeromyxobacter spp., as well as humic substances can facilitate its formation in mildly acidic peatlands. Since microbial communities contribute to the bioreduction of Fe(III)-rich akaganeite into Fe(II)-bearing magnetite and chukanovite, humic substances act as microbial electron shuttles [39,40]. This transformation pattern, supported by in situ evidence, demonstrates that nFeN and nZVI behavior is shaped by the biotic and geochemical interplay unique to each environment.

A central factor influencing transformation of NPs is the quality and availability of DOC in the field. Based on the origin of DOC, river-derived DOC is likely dominated by fulvic acids, while peat-derived DOC is expected to contain a higher proportion of humic acids [41], which may differentially influence NPs aging and interaction with PPs. Fulvic acids, being smaller and more reactive (with roughly twice the number of carboxyl groups as humic acids), could enhance or inhibit NPs-PPs interactions depending on environmental pH and contaminant load. In systems such as EG, where fulvic acids are likely to dominate, DOC concentrations inside the dialysis bags reached up to 63 mg L⁻¹ for nFeN, which is substantially higher than the surrounding river water (Table 2, Table S8). This indicates strong interactions of NPs with smaller, mobile fulvic acids associated with contamination sources [41]. Low molecular weight fulvic acids can diffuse through the dialysis membrane, accumulate inside the bags, and interact with both NPs and PPs, which may influence the removal efficiency of nFeN. Their high reactivity, resulting from a greater number of carboxyl groups compared to humic acids, makes them particularly effective under acidic to neutral pH conditions observed in EG 1 and EG2 (Table 2) [42]. At the La Guette as a peat-dominated wetland system, the ratio humic acids/fulvic acids could vary from 41 to 0.23 between peat and DOC-rich pond [43,44]. Here, DOC is likely rich in humic acids, which have larger molecular size and stronger binding capacity due to their content of lignin phenols, nitrogen-containing compounds, and straight-chain aliphatics [41]. Thus, the lower DOC levels inside the dialysis bags at La Guette compared to the surrounding groundwater may be explained by limited diffusion through the membrane.

To clarify the key mechanisms behind NPs-PPs interactions, measured log Kd values were compared to model-based log Koc and log Kow, estimated from the molecular structures of PPs (Fig. S8). This comparison showed that hydrophobicity alone does not explain the observed affinities, especially for ionizable PPs, where electrostatic interactions likely play a significant role. In particular, cationic PPs exhibited log Kd values that consistently exceeded predicted log Koc, which is calculated assuming neutral molecules and does not account for ionization. This suggests that ion exchange between cationic PPs and negatively charged surfaces of NPs and NOM is a significant retention mechanism [45,46]. Ion exchange is often more favorable than purely hydrophobic interactions, especially in systems rich in reactive functional groups [47]. Survey and high-resolution XPS confirm that solution-derived ions are present on the NPs surfaces (Table S6). Although inorganic cations such as $Ca^{2+}$ and $Na^+$ can compete for surface sites, PPs still preferentially associate with the particles due to their charge state and hydrophobic/polar characteristics [48]. Notably, carbon-supported nZVI composites can remove antibiotics through multiple mechanisms, including chemisorption, hydrogen bonding, redox reactions, $π-π$ interactions, and Fenton-like catalysis [49–51]. Anionic compounds were excluded from the analysis due to their concentrations being below detection limits. Furthermore, weak correlations between log Kd and log Kow further underscore the limited utility of hydrophobicity-based models when predicting the sorption behavior

of ionizable or charged PPs [52,53].

While their retention appears to be favored at lower DOC concentrations (Fig. 5), cationic compounds are also the most affected by increasing DOC levels. This may be explained by competitive effects, steric hindrance, or enhanced interactions between organic matter and cationic PPs. As the Kd values of neutral molecules show little variation across the observed DOC concentration range, reversing the added value of NP for cationic PP sorption for low DOC concentrations. It seems that cationic PPs favors interaction with polar NPs rather than hydrophobic OM interacting with NPs, as highlighted by other studies [54,55].

## 4.2. Implementation of NPs and impact on PPs distribution in the Egoutier catchment: advancing water quality

In hydrological systems affected by contaminant fluxes and dynamic environmental conditions like Egoutier watershed, NPs offer a promising low-tech solution for mitigating the bioavailability of PPs and their associated ecological risks. Strategically deploying NPs in key locations within a watershed could help intercept contaminants before they accumulate in downstream zones, particularly during high-flow events like flash floods. In redox-sensitive accumulation areas, where fluctuating conditions may accelerate organic matter degradation and remobilize bound contaminants [56], NPs may contribute to stabilizing pollutants and reducing their mobility.

Long-term monitoring of the Egoutier watershed has revealed that the particulate matter in the Egoutier stream is notably low in clay content (less than 1 %) and enriched in organic carbon (up to 18 %), favoring non-specific adsorption of neutral PPs, with higher discharge rates, persistence, and hydrophobicity [28]. Resembling, based on their negative charge, both NPs can be effective in capturing neutral or positively charged PPs within the suspended materials carried by water in a catchment area, effectively reducing their concentration in the water as it flows. Moreover, the interaction between site-specific DOC and NPs may enhance the retention of PPs, serving as a natural vector that facilitates their immobilization in soils and sediments.

The retention of PPs on NPs could significantly aid in the spatial distribution of these contaminants within the Egoutier catchment. Suspended particulate matter responsible for contaminants transport in the catchment, as collected by the GEACOS system, has a coarse texture with majority particle sizes ranging from 250 to 1800 µm. These larger particles are not effective at long-term retention of PPs, which have relatively low total concentrations not exceeding $64 ng g^{-1}$. On the contrary, PPs in Egoutier catchment have a tendency to be deposited in bed load sediments in specific accumulation zones with higher TOC (up to 11 %)

<figure><img src="image_8.png" /><figcaption>Fig. 5. Log Kd of PPs as a function of DOC for nFeN and nZVI at application sites. For EG2, the data refer to EG2-nFeN_2 and EG2-nZVI_2. The symbols (-), (0), and (+) following each PPs name indicate its charge: negative, neutral, and positive, respectively.</figcaption></figure>
and silts grain sizes (2–63 µm) particles (up to 46 %) [28]. This feature corresponds to specific sedimentary dynamics with low transportation and strong accumulation zones in the upstream part of the catchment, where NPs have been situated. Monitoring in GEACOS revealed lower removal efficiency of NPs for PPs in the accumulation pond at EG2. The lacustrine nature of this system likely led to water dilution and reduced contaminant input, thereby limiting the exposure of NPs to PPs. Both nFeN and nZVI showed a sufficient affinity for neutral or positively charged PPs in the larger fraction, bound predominantly to magnetite and akaganeite. Similarly, to EG1, nZVI exhibited the highest affinity for diazepam, venlafaxine, and carbamazepine, whereas nFeN showed the highest affinity for carbamazepine and paracetamol. PPs concentrations in liquid phase were smaller than those at EG1, but following the same observation about the predominance of neutral PPs in solution.

Although nFeN displays enhanced resistance to oxidation compared to nZVI, its removal performance is governed not only by its intrinsic properties but also by the interplay of suspended solids, dissolved substances, and local biogeochemical conditions within the accumulation pond. Moreover, when evaluating NPs behavior in complex water matrices, it is essential to consider multifunctional mechanisms, including redox transformations, microbial interactions, and adsorption/complexation processes. The oxidative degradation of PPs has been demonstrated to occur in the presence of ferrous ions and hydrogen peroxide (H₂O₂), facilitating classic Fenton reactions [57,58]. In the absence of externally added H₂O₂, the formation of hydroxyl radicals capable of degrading PPs is attributed to bio-Fenton processes, as reported for magnetite-mediated systems [59,60]. However, an important observation in this study is the quenching effect of NOM on oxidation processes. Given the relatively low concentrations of PPs compared to NOM, oxidative degradation is not expected to be the dominant removal pathway under the studied conditions. The potential synergistic effects between NPs and microbial communities further emphasize the dynamic nature of contaminant attenuation in real-world systems. From a remediation perspective, it is essential to distinguish between adsorption and biodegradation pathways to select the most appropriate pollutant removal approach. The effectiveness of nanoparticle-based strategies also depends on tailoring them to specific site conditions. Thus, in engineered systems like water treatment plants, removing suspended solids before applying nanoparticles could enhance treatment outcomes, especially when aligned with the requirements of downstream processes.

## 5. Conclusions

This study provides direct in situ evidence of nFeN transformation and reactivity in complex aquatic environments, emphasizing its interactions with NOM and emerging PPs pollutants. The innovative use of 3.5 kDa dialysis bags enabled controlled exposure to low-molecular-weight DOM, allowing for safe, realistic assessment of NPs behavior in the field. To complement these findings and bound residual risk, we flag targeted ecotoxicity testing under site-relevant conditions as a priority for future work. nFeN exhibited stronger interactions with PPs, particularly venlafaxine and oxazepam, under high-flow conditions, where enhanced Fe:N oxidation should promote reactivity. In contrast, benchmark nZVI was more effective for venlafaxine and diazepam in low-flow environments, benefiting from slower surface passivation. Beyond abiotic oxidation, transformation of nFeN may be driven by biotic processes in DOC-rich environments. DOC composition and concentration influenced NPs surface charge, colloidal stability, and competition with PPs. Elevated log Kd values over log Koc and log Kow highlight possible electrostatic interactions and ion exchange, rather than hydrophobicity, as key drivers of cationic PPs retention. To summarize, nFeN's structural stability and responsiveness to environmental conditions make it well-suited for potential field applications, including integration into advanced composites. Its scalability for emerging contaminant removal depends on tailoring to specific geochemical and

hydrological site conditions.

### CRediT authorship contribution statement

**Veronika Veselská:** Writing – original draft, Project administration, Investigation, Funding acquisition, Data curation, Conceptualization, Formal analysis, Resources, Supervision, Writing – review & editing.
**Josef Kaslík:** Writing – review & editing, Visualization, Methodology, Data curation, Formal analysis, Investigation, Validation. **Diego Baragaño:** Writing – review & editing, Investigation, Data curation.
**Anaëlle Simonneau:** Visualization, Validation, Supervision, Methodology. **Thomas Thiebault:** Writing – review & editing, Methodology, Investigation. **Martin Petr:** Data curation, Investigation, Methodology.
**Jan Filip:** Formal analysis, Writing – review & editing. **Jean-Sébastien Moquet:** Investigation, Data curation. **Gildas Ratiė:** Writing – original draft, Methodology, Investigation, Funding acquisition, Data curation, Conceptualization, Supervision, Writing – review & editing.

### Declaration of Generative AI and AI-assisted technologies in the writing process

During the preparation of this work the authors used ChatGPT 4 to improve language and readability of the manuscript. After using this tool, the authors reviewed and edited the content as needed and take full responsibility for the content of the publication.

### Funding sources

The research was supported from ERDF/ESF project TECHSCALE (No. CZ.02.01.01/00/22_008/0004587). This study was also funded by the Barrande Mobility Project Nr. 8J22FR015 funded by the Ministry of Education Youth and Sports of the Czech Republic, Ministry for Europe and Foreign Affairs (MEAE) and the Ministry of Higher Education and Research (MESR) in France. This work was supported by the LabEx VOLTAIRE project (10-LABX-0100), funded by the French Ministry of Higher Education and Research. Diego Baragaño would like to thank to the Government of the Principality of Asturias (ID/2024/000749). The authors also acknowledge the assistance provided by the Research Infrastructure NanoEnviCz, supported by the Ministry of Education, Youth and Sports of the Czech Republic under Project No. LM2023066.

### Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

### Acknowledgements

The authors would like to thank Amélie Humbrecht, Nicolas Freslon, Léo Chevrier and Marielle Hatton for their valuable contributions and support during the course of this research. Special thanks are extended to Ivo Medrín, Erik Mikeska, Petr Zajíček, and Viktorie Víchová for their expertise and assistance in the synthesis and characterization of the solid (nano)materials. We thank Jiří Hošek for SEM analysis support and Veronika Šedajová for the XPS analysis discussion. Fabrice Alliot is acknowledged for his help during the quantification of PPs. The data supporting this study are available in the ZENODO repository.

## Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.cej.2025.168285.
# Data availability

The data supporting this study are available in the ZENODO repository.

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