O3; Laboratory report on solar/NSSM treatment of selected PFAS in batch reactor

IPS-2022-02-4780 Kušić University of Zagreb Faculty of Chemical Engineering and Technology Zagreb, Croatia & University of Ljubljana Faculty of Chemistry and Chemical Technology Ljubljana, Slovenia O3; Laboratory report on solar/NSSM treatment of selected PFAS in batch reactor (3 rd year) (D3.1) Project: Solar-assisted photocatalytic degradation of perfluorinated compounds in water (SoAPperF), IPS-2002-02-4780. Project leaders: Prof. Hrvoje Kušić (PhD), Croatia, and Prof. Urška Lavrenčič Štangar (PhD), Slovenia Start: 1/11/2022 End: 31/10/2025 Zagreb, November 2025. IPS-2022-02-4780 Kušić 1. Experimental procedure for monitoring selected PFAS and pharmaceuticals PFOA (Perfluorooctanoic acid, CAS # 1763-23-1) High-Performance Liquid Chromatography – tandem mass spectrometry (HPLCMS/MS) The concentration of PFOA was monitored using the ultra-high-performance liquid chromatography coupled with a triple quadripole mass spectrometry LCMS-8050 (Shimadzu, Japan). The modular system consists of LC part: controller, SCL-40, degasser, DGU-405, two pumps, LC-40Dx3, autosampler, SK-40Cx3, column thermostat, CTO-40S (all Shimadzu, Japan); the MS parts were: mass spectrometer LCMS-8050 (Shimadzu, Japan) and nitrogen generator Genius 1051 PSA (Peak Scientific, UK). All samples were filtered before analysis (Chromafil, Xtra CA, 0.45 μm, Macheray Nagel, Germany) and analysed in triplicates. Chromatographic separation of PFOA was done on a Shimpack GIST (Shimadzu, Japan) C18 column with dimensions of 150 mm x 2.1 mm, 3 μm (Shimadzu, Japan). The column was termostated on 40 °C. Ammonium acetate (20 mM) in ultrapure water (phase A) and methanol (phase B) at a flow rate of 0.4 mL min-1 in the 70:30 ratio, was used as the mobile phase for separation, analysed in isocratic mode for 10 min. Injection volume was 5 μL. The collision energy was 20 eV. Nitrogen was used as nebulizing and drying gas, while flow was 3 L min-1 and 5 L min-1 respectively. Argon was used as heating (collision) gas and flow was 15 L/min. Interface temperature was 190 °C, desolvation line temperature was 200 °C, while the heating block temperature was 300 °C. Molecular ion with a mass of 413 Da [M-H]- was recorded in the first quadrupole (Q1) in the negative operating mode, while in the second quadrupole the characteristic ions of the molecular ion fragments were recorded, while tracked multiple reaction monitoring (MRM) transitions were 413→369, 413→219 and 413→169 m/z. IPS-2022-02-4780 Kušić Figure 1. PFOA chromatogram Figure 2. Count vs. Mass-to-Charge (m/z). IPS-2022-02-4780 Kušić Figure 3. PFOA chromatogram with MRM transitions. Ion chromatography (IC) Ion chromatographic analysis was performed using a one-dimensional analytical IC system, the Dionex ICS-3000 (Thermo Fisher Scientific, USA). The entire system was controlled using the Chromeleon 7.1 software package. A hydroxide ion solution (KOH) was used as the mobile phase, with isocratic elution conducted at 30 mM KOH. The flow rate was maintained at 1 mL/min, with the column temperature set at 30 °C and the detector temperature at 35 °C. The injection loop volume was 25 μL. The stationary phase consisted of a high-capacity ionexchange column (AS11 HC) paired with a guard column (AG11 HC). Detection of PFOA was performed using a conductivity detector. Nitrogen gas of 5.0 purity was used as an inert gas to prevent vacuum formation in the mobile phase reservoirs. An ASRS 4 mm electrolytic suppressor was used to suppress the mobile phase signal, with the current set at 75 mA. The analysis time for each sample was 10 minutes. IPS-2022-02-4780 Kušić CIP (Ciprofloxacin, CAS # 85721-33-1) High-Performance Liquid Chromatography – tandem mass spectrometry (HPLCMS/MS) The degradation byproducts of CIP were analyzed on liquid chromatography connected with a triple quadrupole mass spectrometer (LCMS/MS-8045, Shimadzu, Japan). Separation was achieved using a conventional C18 column (2.1 mm i.d. × 150 mm; Shimadzu, Japan). The mobile phases consisted of 2 mM ammonium acetate in 2% methanol (mobile phase A) and 2 mM ammonium acetate in 98% methanol (mobile phase B). The gradient elution was performed at a flow rate of 0.1 mL min -1 as follows: starting with 90% A for the first 4 minutes, decreasing to 20% A over the next 4 minutes, followed by a further decrease to 5% A over 8 minutes. The system was then returned to the initial conditions and equilibrated for an additional 3 minutes. High-Performance Liquid Chromatography (HPLC) The concentrations of CIP were determined using a Shimadzu LC-20 series high-performance liquid chromatography (HPLC) system coupled with an SPD-M20AVP UV-PDA detector and a C18 column (250 mm × 4.6 mm i.d., particle size 5 μm, Macherey-Nagel Nucleosil, Duren, Germany). The mobile phases consisted of 50 mM aqueous formic acid (mobile phase A) and acetonitrile (mobile phase B), applied under isocratic elution condition. Total Organic Carbon (TOC) The extent of mineralization was assessed using a Total Organic Carbon (TOC) analyzer (TOCVCPN, Shimadzu, Japan) by quantifying the percentage of TOC removal. Chemical oxygen demand (COD) and biochemical oxygen demand (BOD₅) IPS-2022-02-4780 Kušić COD and BOD₅ were quantified by colorimetric analysis using a HACH DR2800 spectrophotometer, equipped with barcode reader. COD was determined with Hach-Lange reagent kits LCK614 and LCK1414, and BOD₅ with kit LCK554. Aquatic toxicity The aquatic toxicity of the treated samples was evaluated using standardized commercial bioassays covering different trophic levels. Bacterial toxicity was assessed via inhibition of bioluminescence emitted by Vibrio fischeri (VF), following the ISO 11348-3:2007 protocol, with measurements performed on a Biotox-Lumi 10 luminometer (Macherey-Nagel, Germany). In parallel, acute toxicity to freshwater crustaceans was determined based on the immobilization response of Daphnia magna (DM) according to ISO 6341:2012 protocol, using the Daphtoxkit F magna system (Microbiotests, Belgium). Reactor setup Photocatalytic degradation of PFOA and CIP were carried out in a custom-made, closed-batch, quartz-cover photoreactor. The reactor has cooling water circulated through the jacket to maintain a constant temperature of the reaction system, while a magnetic stirrer (at 500 rpm) was used to homogenize the reaction solution, which was placed under the solar simulator (Oriel Newport, Irvin, CA, USA), equipped with a collimator, light source, 450 W Xe lamp (Osram, Munich, Germany), and air mass filter (AM 1.5 G) for simulating solar light. In experiments with UV-A light irradiation only, a UVB/C Blocking Filter along with an FSRBG3 Colored Glass Bandpass Filter, used to narrow irradiation to the UVA region only (with maximum at 356 nm), were applied instead of an air mass filter. The closed reactor system was used to purge O 2 and to create an inert atmosphere via N 2 purging within the reactor system, thus preventing superoxide radical generation (O 2•− ). For the experiment, the reactor was filled with a 90 mL aqueous PFOA (12 μM) or CIP (50 μM) solution in which 1 g/L of photocatalyst was added. Prior to illumination, the suspension was stirred in the dark for 30 min to achieve adsorption–desorption equilibrium. During the experiment, the suspension was exposed to light (Solar or UV-A), and 0.5 mL samples were withdrawn at regular intervals. Each sample was filtered using a 0.45 μm cellulose filter (CA, Chromafil, Macherey-Nagel, Dueren, Germany) and taken for further analysis. IPS-2022-02-4780 Kušić Scheme 1. Custom-made closed batch, quartz-cover photoreactor Photocatalytic degradation of PFOA using the prepared photocatalysts was also tested in two other different reactor setups. The first reactor (Reactor A) is vertical, triangular-shaped batch reactor, fitted with six UV Blacklight Blue (UV BLB) bulbs, two positioned on each side, and cooled by a center-lined fan. The second reactor (Reactor B) is a circular metal batch reactor, fitted with an UV LED strip emitting Blacklight Blue (BLB) light along the inner wall, and cooled externally by circulating water through tubes surrounding the reactor. Both reactors were equipped with a PET cell, which was used to perform the photoatalytic tests. We moved from Reactor A to B to have a sealed PET cell and to achieve higher light intensities with dimmable LED lights. Scheme 2 shows schematics of both reactor setups and measured emission spectra of the light sources. Both systems emit light of comparable wavelength, with a maximum intensity at 365 nm. Light intensities, obtained with integration of the emission spectra, were 27.7 W/m 2 for Reactor A and 32.0 W/m 2 for Reactor B with one LED strip and 58.8 W/m 2 with two LED strips turned on. IPS-2022-02-4780 Kušić Scheme 2. Reactor schematics and the corresponding emission spectra of the light sources. Photocatalytic degradation experiments were performed using aqueous solutions of perfluorooctanoic acid (PFOA) at initial concentrations of 40 mg/L and 100 mg/L. For each experiment, 100 mL of the prepared solution was transferred to a reactor and the photocatalyst was added at a loading of 0.5 g/L. Before light irradiation, the suspension was first magnetically stirred in the dark for 1 h to achieve adsorption equilibrium. Photocatalysis was then initiated by switching on the light source. The suspension was continuously stirred to maintain a homogeneous dispersion of the photocatalyst. Aliquots (≈ 2 mL) were withdrawn at 2, 4, 6, 8, 24, and 48 hours, centrifuged at 11,000 rpm for 4 minutes to remove catalyst particles, and stored at −20 °C until analysis. The concentrations of PFOA and fluoride ions were determined using LC-MS/MS and IC, respectively. The degradation efficiency was calculated relative to the initial PFOA concentration. Chain shortening and defluorination percentages were calculated using the following equations: IPS-2022-02-4780 Kušić 𝐶ℎ𝑎𝑖𝑛 𝑠ℎ𝑜𝑟𝑡𝑒𝑛𝑖𝑛𝑔 %  󰇛1  󰇛󰇜 󰇛󰇜󰇜∗100 (1) 𝐷𝑒𝑓𝑙𝑢𝑜𝑟𝑖𝑛𝑎𝑡𝑖𝑜𝑛 %  󰇡󰇛󰇜∗󰇛  ,󰇜 ∗󰇛󰇜∗󰇛󰇜󰇢∗100 (2) where c(t) and c(0) represent concentration of PFOA at a certain time and initial PFOA concentration, respectively. In equation (2) M(F) and M(PFOA) represent the molar masses of fluorine and PFOA, and c(F−,t) represents the concentration of F− ions at a certain time. To assess catalyst reusability and investigate potential TiO₂–fluoride interactions, the photocatalyst was recovered after each reaction by centrifugation and subjected to different post-treatment procedures before reuse. The used catalyst was either (i) separated and dried without additional washing, (ii) washed with Milli-Q water, centrifuged, and dried, (iii) washed with a NaCl solution followed by centrifugation and drying to evaluate fluoride removal through ion exchange, or (iv) washed with water, dried, and calcined at 600 °C to thermally remove surface-bound organic compounds and/or fluoride species. The treated photocatalysts were subsequently characterized to investigate the TiO2-fluoride interactions and subsequently reused under identical photocatalytic conditions to evaluate any changes in activity. IPS-2022-02-4780 Kušić Analysis of possible CIP degradation products/pathways: NN HN F OH O O m/z = 332 NN H HN F OH O O NH2N F OH O O NN HN F OH O O O O NN HN OH O O NH2N OH O NN NH2OH OH O O N O NN NH2O F OH O O N F OH O O N N NN NH 2 O F OH O O OH O NN H NH2 F OH O O NN H O F OH O O Pathway 2 Pathway 1 -. O 2 /e - -F 1O2 m/z = 313 m/z = 304 m/z = 185 m/z = 216 m/z = 362 m/z = 334 m/z = 306 m/z = 291 m/z = 263 m/z = 334 m/z = 316 m/z = 350 DP1 DP2 DP6 DP7 DP3 DP4 DP5 DP8 DP9 DP10 DP11 NN HN F O m/z = 285 NN NH2 O F O m/z = 264 DP12 DP13 Pathway 3 -CO 2 -CO -CO -H 2 O •OH -CO Figure 11. Proposed degradation pathways of CIP by FeSK-0.03 photocatalyst IPS-2022-02-4780 Kušić Figure 12. Mass to charge ratios of degradation products of CIP by FeSK-0.03 photocatalyst IPS-2022-02-4780 Kušić Figure 13. Temporal evolution and degradation of major CIP by-products Figure 14. (a,b) Biodegradability, TOC, and ecotoxicity (VF and DM) changes during CIP treatment over FeSK-0.03 under solar irradiation 0.00E+00 1.00E+07 2.00E+07 3.00E+07 4.00E+07 5.00E+07 6.00E+07 7.00E+07 0 20406080100120 area of DP1 to DP5 time, min DP1 DP2 DP3 DP4 DP5 0.00E+00 1.00E+06 2.00E+06 3.00E+06 4.00E+06 5.00E+06 6.00E+06 7.00E+06 8.00E+06 9.00E+06 0 20406080100120 area of DP6 and DP7 time, min DP6 DP7 0.00E+00 2.00E+06 4.00E+06 6.00E+06 8.00E+06 1.00E+07 1.20E+07 1.40E+07 1.60E+07 0 20406080100120 area of DP8 to DP11 time, min DP8 DP9 DP10 DP11 0.00E+00 2.00E+06 4.00E+06 6.00E+06 8.00E+06 1.00E+07 1.20E+07 1.40E+07 0 20406080100120 area of DP12 and DP13 time, min DP1 2 DP1 3 0 10 20 30 40 50 60 70 80 90 100 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 -30 0 30 60 90 120 150 180 210 240 270 300 BOD 5 /COD ratio treatment time, min biodegradability mineralization partially biodegradable biodegradable non-biodegradable TOC decrease, % 0 0.5 1 1.5 2 -30 0 30 60 90 120 150 180 210 240 270 300 TU (100/EC 50 %) treatment time, min to Vibrio Fischeri to Daphnia Magna (a) (b) IPS-2022-02-4780 Kušić Table S1. Structures of identified CIP degradation products and their toxicity on Daphnids, calculated using ECOSAR Compound m/z structure LC 50 (mg/L) DP1 362 2.90 × 10 5 DP2 334 7.22 × 10 4 DP3 306 4.54 × 10 4 DP4 291 8.81 × 10 3 DP5 263 8.90 × 10 3 IPS-2022-02-4780 Kušić DP6 350 1.93 × 10 8 DP7 316 7.53 × 10 2 DP8 313 3.48 × 10 6 DP9 304 2.18 × 10 7 DP10 216 4.52 × 10 3 DP11 185 30.3 IPS-2022-02-4780 Kušić DP12 285 76.6 DP13 264 7.45 × 10 3 IPS-2022-02-4780 Kušić 3. Testing of new synthetized materials for PFOA degradation under UV-A/solar irradiation Figure 15. Initial testing of photocatalyitic degradation of PFOA (40 ppm) IPS-2022-02-4780 Kušić Figure 16. Products of photocatalyitic degradation of PFOA (40 ppm) with In 2 O 3 (1g/L) under UV-A after 24 hours IPS-2022-02-4780 Kušić 4. Testing of new synthetized materials for PFOA degradation in PC/PEC systems Table x. PFAS (perfluorinated octanoic acid) degradatinion by WO 3 deposited at FTO glass during 2 h Method Photocatalysis Photoelectrochemical process %degradation 19.5 14.7 Electrode testing before and after PFAS degradation a) b) Figure 17. Graphical representations of the linear polarization of an illuminated WO3 electrode obtained in a) photocatalytic and b) photoelectrochemical processes of PFAS degradation. IPS-2022-02-4780 Kušić Figure 18. Energy band diagram for WO 3 (sample 1) i WO 3 modified by Ga (sample 2) and Zn (sample 3)