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 (2 nd 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 2024. IPS-2022-02-4780 Kušić 1 1. Experimental procedure for monitoring selected PFAS PFOA (Perfluorooctanoic acid, CAS # 1763-23-1) LC-MS analytical testing of PFOA Due to the observed increase in the concentration of PFOA during the photocatalytic reactions, additional tests were conducted with the aim of establishing and eliminating analytical error. Method linearity assessment To determine the most favorable working range for PFOA concentration, linearity tests were performed across the following concentration ranges: 0.01–0.1 ppm, 0.1–1 ppm, and 1–10 ppm. The linear range should cover 0–150% of the expected analyte concentration. All standards were prepared using polypropylene laboratory dishes. Each concentration standard was aliquoted into three separate polypropylene vials. Samples were analyzed using LC-MS. The mean value for three separate injections of each concentration was extracted, and using the mean values obtained, graphs were plotted and the R² values were calculated. Linear approximation trend lines, forced through zero, were generated using Excel. IPS-2022-02-4780 Kušić 2 Table 1. Method linearity assessment. Range 0.01-0.1 ppm Range 0.1–1 ppm Range 1–10 ppm ppm Concentration /ppm Area Concentration /ppm Area Concentration /ppm Area 0.01 19765 0.1 195870 1 1251212 0.01 20245 0.1 201241 1 1237444 0.01 20257 0.1 203406 1 1254115 0.025 50434 0.25 434234 2.5 2272862 0.025 51025 0.25 434814 2.5 2295625 0.025 51539 0.25 432816 2.5 2279630 0.05 103302 0.5 757862 5 3479483 0.05 106242 0.5 776740 5 3491428 0.05 102801 0.5 772752 5 3504436 0.075 149749 0.75 1039762 7.5 4427396 0.075 151268 0.75 1038906 7.5 4403849 0.075 148651 0.75 1041326 7.5 4439002 0.1(D) 195731 1 1276566 10 5234006 0.1(D) 198229 1 1288875 10 5284153 0.1(D) 196804 1 1289611 10 ppm 5300029 R² = 0.9996 R² = 0.9925 R² = 0.9734 R² = 0.9906 / / R² = 0.9580 R² = 0.9628 Based on the R² values, the optimal concentration of PFOA for use in reactions was found to be 0.1 ppm, as the values from 0–150% of the specified concentration fall within the linear range. IPS-2022-02-4780 Kušić 3 Figure 1. Calibration curves in ranges: a) 0.01-0.1 ppm b) 0.1-1 ppm c) 0.01-1 ppm d) 1-10 ppm e) 0.1-10 ppm f) 0.01-10 ppm. y = 2E+06x R² = 0.9987 0 50000 100000 150000 200000 250000 0 0.05 0.1 0.15 Range 0.01-0.1 ppm y = 1E+06x R² = 0.9653 0 200000 400000 600000 800000 1000000 1200000 1400000 1600000 00.511.5 Range 0.1-1 ppm b y = 1E+06x R² = 0.9812 0 200000 400000 600000 800000 1000000 1200000 1400000 1600000 00.511.5 Range 0.01-1 ppm c y = 585232x R² = 0.8305 0 1000000 2000000 3000000 4000000 5000000 6000000 7000000 0 5 10 15 Range 1-10 ppm d y = 592979x R² = 0.8954 0 1000000 2000000 3000000 4000000 5000000 6000000 7000000 0 5 10 15 Range 0.1-10 ppm e y = 589662x R² = 0.9374 0 1000000 2000000 3000000 4000000 5000000 6000000 7000000 0 5 10 15 Range 0.01-10 ppm f a IPS-2022-02-4780 Kušić 4 Figure 2. PFOA chromatogram Figure 3. Count vs. Mass-to-Charge (m/z). IPS-2022-02-4780 Kušić 5 Figure 4. PFOA chromatogram with MRM transitions. Laboratory dishes and vials material (glass versus polypropylene) To asses the influence of laboratory dishes and vials material on PFOA concentartion, standard solutions were prepared in concentration range 0.01-1 ppm. All standards were prepared using laboratory glassware. Each concentration standard was aliquoted into three separate glass vials. Samples were analyzed using LC-MS. Relative standard deviation (RSD) was calculated for each concetration level and compared with the results obtained by preparation and analysis in polypropylene (PP) dishes and vials. R² value was calculated to confirm linearity. IPS-2022-02-4780 Kušić 6 Table 2. Glass versus polypropylen vials and laboratory dishes test PFOA concetration /ppm Area (glass) %RSD (glass) Area (PP) %RSD (PP) 0.01 19675 2.66067 19765 1.400551 0.01 20651 20245 0.01 19791 20257 0.025 44490 3.764212 50434 1.199321 0.025 45885 51025 0.025 47940 51539 0.05 99112 1.795025 103302 1.856021 0.05 102236 106242 0.05 99132 102801 0.075 153054 0.611772 149749 0.861178 0.075 151523 151268 0.075 153214 148651 0.1 193078 1.142443 195731 0.646826 0.1 191924 198229 0.1 196202 196804 0.25 471807 1.241469 434234 0.215311 0.25 476754 434814 0.25 483609 432816 0.5 888286 0.693361 757862 1.128998 0.5 876960 776740 0.5 878647 772752 0.75 1182711 0.187229 1039762 0.103914 0.75 1178449 1038906 0.75 1181601 1041326 1 1437207 0.542054 1276566 0.507749 1 1440559 1288875 1 1452119 1289611 R² value R² = 0.9920 R² = 0.9906 Based on the calculated RSD and R² values, it was confirmed that both glass and polypropylene dishes and vials are suitable for PFOA standard preparation and analysis. IPS-2022-02-4780 Kušić 7 Filter membrane material Three different filter membrane materials were tested: nylon, cellulose acetate (CA), and hydrophilized polytetrafluoroethylene (H-PTFE). Their influence on PFOA concentration was examined during the first use and after reuse. Filters used for the first time were tested with the initially prepared solution, while reused filters were tested with a solution that had been exposed to solar light for 60 minutes. PFOA recovery was calculated with respect to the concentration value obtained without using a filter. Table 3. First time used filters – membrane material comparison Table 4. Reused filters – membrane material comparison The cellulose filter exhibited the best properties for filtering solutions containing PFOA. Filter memb. material c(PFOA)/ppm Recovery None 0.09588 / CA 0.08969 93.54 % Nylon Not detected NA H-PTFE 0.59136 616.77 % Filter memb. material c(PFOA)/ppm Recovery None 0.09739 / CA 0.09669 99.28 % Nylon 0.00666 6.84 % H-PTFE 0.13313 136.70 % IPS-2022-02-4780 Kušić 8 Sampling position The influence of the sampling position on the detected concentration was examined. During the reaction, samples were taken simultaneously from the bottom and top of the reactor. Percentage difference was calculated. Table 5. Measured PFOA concentration in regard to sampling position Time/min Position of sampling c(PFOA)/ppm Percentage difference t= -30 Bottom 0.09269 0.31 % t= -30 Top 0.09298 t=0 Bottom 0.09492 0.63 % t=0 Top 0.09432 t=60 Bottom 0.09782 0.44 % t=60 Top 0.09739 t=180 Bottom 0.11027 0.35 % t=180 Top 0.10988 Based on the calculated percentage difference, the sampling position does not have a significant influence on the detected concentration of PFOA. IPS-2022-02-4780 Kušić 15 Effect of temperature on PFOA concentration Eighty milliliters of the prepared 0.1 ppm PFOA standard were added to a polypropylene beaker, which was then placed on a magnetic stirrer with temperature control. Initially, the temperature was set to 30°C for one hour, after which it was increased by 5°C every hour. Throughout the experiment, the solution was stirred at a constant speed of 300 rpm. The samples were analyzed using LC-MS, and the percentage difference was calculated for each step of the temperature change, as well as the total percentage difference between the first and the final sample. Table 12. Effect of gradual change in temperature on PFOA concentration Time /min Temperature /°C c(PFOA) /ppm Percentage difference t=0 28 (RT) 0.08033 / 9.79104 % t=60 30 0.08089 0.694703 % t=120 35 0.08397 3.7365 % t=240 45 0.0886 5.36594 % The results indicate that temperature significantly influences the increase in PFOA concentration. An additional experiment was conducted in which 80 milliliters of the prepared 0.1 ppm PFOA standard were added to three polypropylene beakers. Each beaker was stirred at 300 rpm and maintained at different temperatures: 30°C, 35°C, and 40°C. The samples were then analyzed using LC-MS, and the percentage differences between the PFOA concentrations in the first and final samples were calculated. IPS-2022-02-4780 Kušić 16 Table 13. Effect of temperature on PFOA concentration Time /min Temperature /°C c(PFOA) /ppm Percentage difference t=0 30 0.09248 0.04324 % t=60 30 0.09216 t=180 30 0.09220 t=240 30 0.09252 t=0 35 0.09099 2.73171 % t=60 35 0.09021 t=180 35 0.09450 t=240 35 0.09351 t=0 40 0.09013 3.44564 % t=60 40 0.09190 t=120 40 0.09329 The most significant increase in concentration was observed in the beaker maintained at 40°C. It should be noted that the solution was held at this temperature for the shortest duration. IPS-2022-02-4780 Kušić 17 Effect of reactor washing solvent The prepared 0.1 ppm PFOA standard was added to the reactor, which had been thoroughly washed with a 50:50 methanol-water solution. The standard solution was stirred in the dark for 30 minutes, after which solar light was introduced, and the solution was left exposed for 3 hours. The samples were analyzed using LC-MS, and the percentage difference between the PFOA concentrations in the first and final samples was calculated. The results were then compared with those obtained from a similar experiment conducted in a reactor that had been washed with water only. Table 14. Effect of reactor washing solvent Time /min MeOH:H20 c(PFOA)/ ppm Percentage difference H20 c(PFOA)/ ppm Percentage difference t=-30 0.08111 8.66899 % 0.09269 17.3236 % t=0 0.0798 0.09492 t=60 0.0855 0.09782 t=180 0.08846 0.11027 It was observed that the increase in PFOA concentration was significantly lower when the reactor was washed with a methanol-water solution, compared to when it was washed with water alone. To confirm the results, additional experiment was performed. The prepared 0.1 ppm PFOA standard was added to the reactor, which had been thoroughly washed with a 50:50 methanolwater solution. The standard solution was stirred in the dark for 30 minutes, after which solar light was introduced, and the solution was left exposed for 3 hours. Each time samples were taken in triplicates and analyzed using LC-MS. Percentage difference between the PFOA concentration in the first and final sample was calculated. IPS-2022-02-4780 Kušić 18 Table 15. Effect of reactor washing solvent tested with sample triplicates Time /min c(PFOA) /ppm Average c(PFOA) /ppm Percentage difference t=-30 0.10031 0.09986 9.17256 % t=-30 0.09885 t=-30 0.10043 t=0 0.0978 0.09775 t=0 0.0993 t=0 0.09615 t=90 0.10372 0.10405 t=90 0.10499 t=90 0.10345 t=180 0.10895 0.10946 t=180 0.10825 t=180 0.11117 It was confirmed that the increase in PFOA concentration is significantly lower when the reactor is washed with a methanol-water solution, compared to when it was washed with water alone. Evaporation influence on PFOA concentration The prepared 0.1 ppm PFOA standard was added to the reactor, which had been thoroughly washed with a 50:50 methanol-water solution and additionally wiped with acetone. The standard solution was stirred in the dark for 30 minutes, after which solar light was introduced, and the solution was left exposed for 4 hours. The experiment was performed twice: first, with the reactor covered with a glass plate, and second, with the reactor left open. The samples were analyzed using LC-MS, and the percentage difference between the PFOA concentrations in the first and final samples was calculated. IPS-2022-02-4780 Kušić 19 Table 16. Evaporation influence on PFOA concentration Time /min Covered (PFOA)/ ppm Percentage difference Not covered c(PFOA)/ ppm Percentage difference t=-30 0.09117 5.09861 % 0.09112 4.29553 % t=0 0.09286 0.09065 t=60 0.0944 0.0933 t=120 0.09369 0.09342 t=180 0.09522 0.09351 t=240 0.09594 0.09512 Based on the obtained results, it can be concluded that solvent evaporation does not have an impact on the increase in PFOA concentration. IPS-2022-02-4780 Kušić 20 Ultra-high-performance liquid chromatography – tandem mass spectrometry (UPLCMS/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. 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 IPS-2022-02-4780 Kušić 21 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. 1.2 PFOA by Ionic chromatography Instrument details The instrument is an Integrion (Thermo Scientific), with a conductivity detector. We use a Dionex IonPac AS11-HC column. The mobile phase is KOH, prepared with a MilliQ ultrafiltered water eluent generator. Pollutant details PFOA (Perfluorooctanoic acid, CAS # 1763-23-1) Molecular Formula: C 8 HF 15 O 2 Formula Weight: 414.07 g/mol Composition: C(23.21%) H(0.24%) F(68.82%) O(7.73%) Density: 1.745 ± 0.06 g/cm 3 Polarizability: 17.00 ± 0.5 10 -24 cm 3 Structural formula: IPS-2022-02-4780 Kušić 22 Reactor details The reactor consisted of an aluminum chassis equipped with three low-pressure Hg lamps (Actinic BL, 15W, Philips) and two small fans on the lid as well as a magnetic stirrer, hence providing a top-down height-adjustable illumination. The aliquots taken were centrifuged (11000 rpm for 2 min) to remove the solid contents and analyzed by IC described above. Photocatalytic activity was also assessed in an annular batch reactor of volume 50 mL. The same lamps were used in vertical position and the reactor was mixed using a top-down mixing rod at 300 rpm (IKA). The mixing of the system was provided by purging with O 2 or N 2 at 25 mL/min from the bottom of the cell. IPS-2022-02-4780 Kušić 23 2. Removal of PFOA by UVA/photocatalytic system using carbon-nitirde based photocatalysts Adsorption study Prior to degradation studies were conducted studies of adsorption of fluoride ions onto several comon materials found as the laboratory glassware. We conducted the experiements in glass beakers and found high degree of adsorption of fluoride ions on the glass walls. We then proceeded with experiments done in polypropylene plastic (PP) bottles due to lower adsortpion of F – onto this material. The table below shows this results. Clearly, the catalysts adsorbs quite a lot of fluoride ions, hence the final measured concentrations of F – is most probably an underestimation of the real concentration. NaF mass conc. (µg/L) Catalyst Mass conc. of catalyst [g/L] Time of adsorption t [h] F¯ ions [µg] at t = 0 F¯ ions [µg] at t = t 95 S3N2 0,5 24 97 15±5 165 S3N2 0,5 24 165 51,84 Photocatalytic testing results Two most promissing materials were tested for their photocatalytic degradation of PFOA which was monitored by following deflourination of the parent molecule. The first material was graphitic carbon nitride nanospheres calcined under N 2 atmosphere either in tubular furnace (TB) or in the microwave furnace (MW), named gCN in the table below. The second one was a nano-TiO 2 material doped with sulphur (S) and nitrogen (N), named S3N2 in the table below. The third material was activated carbon (AC). IPS-2022-02-4780 Kušić 24 In the table the first 24 experiments were done in borosilicate glassware (marked with a line) while from then on the experiments were conducted in PP plastic. Experim. Pollutant Mass conc. of pollutant Catalyst Mass conc. of catalyst [g/L] Time t [h] (incl. 1h of adsorption) F¯ ions [µg] at t = 0 F¯ ions [µg] at t = t S1 PFOA 1 μg/L S3N2 + 1% Pt 0,5 4 - - S2 PFOA 10 μg/L S3N2 + 1% Pt 0,5 4 - - S3 PFOA 50 μg/L S3N2 + 1% Pt 0,5 4 7,01 6,51 S4 PFOA 100 μg/L S3N2 + 1% Pt 0,5 4 - - S5 PFOS 1 μg/L S3N2 + 1% Pt 0,5 4 4,99 6,004 S6 PFOS 10 μg/L S3N2 + 1% Pt 0,5 4 4,99 6,5 S7 PFOS 50 μg/L S3N2 + 1% Pt 0,5 4 5,5 6,004 S8 PFOS 100 μg/L S3N2 + 1% Pt 0,5 4 4,99 5,5 S9 PFOA 100 μg/L S3N2 + 1% Pt 0,5 24 - - S10 PFOA 5 mg/L S3N2 + 1% Pt 0,5 4 3,48 7,19 S12 PFOA 5 mg/L gCN-TB-Etch 0,5 4 3,48 6,82 S13 PFOA 5 mg/L AC/PS 0,5 4 - - S14 PFOA 5 mg/L S3N2+1% Pt 0,5 24 8,79 130,96 S15 PFOA 5 mg/L gCN-TB-Etch 0,5 24 8,79 13,71 S16 PFOA 5 mg/L S3N2+1% Pt 0,5 18 - 16,16 S17 PFOA 5 mg/L gCN-TB-Etch 0,5 18 - 6,59 S18 PFOA 5 mg/L gCN-MW-Etch+1%Ag 0,5 6 - 0 S19 PFOA 5 mg/L gCN-TB-Etch+1%Ag 0,5 18 - 0 S20 PFOA 5 mg/L S3N2 0,5 22 2,3 20,86 S21 PFOA 5 mg/L S3N2+1% Pt 0,5 22 2,3 16,84 S22 PFOA 5 mg/L S3N2+1% Ag 0,5 22 1,3 10,83 S23 PFOA 5 mg/L S3N2+1% Pt 0,5 22 2,5 18,52 S24 PFOA+NaF* 5 mg/L S3N2 0,5 72 93,19 13 S25 PFOA 5 mg/L S3N2 0,5 72 0 12,52 S26 PFOA 40 mg/L S3N2+1% Pt 0,5 72 1,73 6265,97 S27** PFOA 40 mg/L S3N2+1% Pt 0,5 72 1,73 6009,61 S28 PFOA 5 mg/L S3N2 0,5 24 0,68 75,18 *NaF concentration = 95 µg/L. **Experiment carried out in a box reactor; other experiments: vertical annular reactor. IPS-2022-02-4780 Kušić 4 IPS-2022-02-4780 Kušić 1 Testing of new synthetized materials for PFOA degradation under solar irradiation Figure 6. Degradation profiles of perfluorooctanoic acid (PFOA) using different photocatalytic materials: SrTiO3 and N-SrTiO3 as well as hydrolysis and photolysis under studied conditions: solar light, natural pH (5.5), γ(catalyst)=1 g/L (where applicable) 40 50 60 70 80 90 100 -30 -10 10 30 50 70 90 Residual PFOA, % time, min hydrolysis photolysis SrTiO3 N-SrTiO3 0 10 IPS-2022-02-4780 Kušić 2 Figure 7. Degradation profiles of perfluorooctanoic acid (PFOA) using ZnSe as well as hydrolysis and photolysis under studied conditions: solar light, natural pH (5.5), γ(catalyst)=1 g/L (where applicable) 40 50 60 70 80 90 100 -30 -10 10 30 50 70 90 Residual PFOA, % time, min hydrolysis photolysis ZnSe 0 10 IPS-2022-02-4780 Kušić 3 Figure 8. Degradation profiles of perfluorooctanoic acid (PFOA) using CuGaS2 as well as hydrolysis and photolysis under studied conditions: solar light, natural pH (5.5), γ(catalyst)=1 g/L (where applicable) 40 50 60 70 80 90 100 -30 -10 10 30 50 70 90 Residual PFOA, % time, min hydrolysis photolysis CuGaS2 0 10 IPS-2022-02-4780 Kušić 4 Figure 9. Degradation profiles of perfluorooctanoic acid (PFOA) using different photocatalytic materials: Cu2O, Ag3PO4, and Ag3PO4/Cu2O as well as hydrolysis and photolysis under studied conditions: solar light, natural pH (5.5), γ(catalyst)=1 g/L (where applicable) 40 50 60 70 80 90 100 -30 -10 10 30 50 70 90 Residual PFOA, % time, min hydrolysis photolysis Ag3PO4 Cu2O Ag3PO4/Cu2O 0 10 IPS-2022-02-4780 Kušić 5 Figure 10. Degradation profiles of perfluorooctanoic acid (PFOA) using different photocatalytic materials: WO3 and ZnWO4 as well as hydrolysis and photolysis under studied conditions: solar light, natural pH (5.5), γ(catalyst)=1 g/L (where applicable) 40 50 60 70 80 90 100 -30 -10 10 30 50 70 90 Residual PFOA, % time, min hydrolysis photolysis WO3 ZnWO4 0 10