Thermal defluorination behaviors of PFOS, PFOA and PFBS during regeneration of activated carbon by molten salt

Highlights

• New method of mineralizing PFCs was proposed.

• Activated carbon was regenerated while mineralizing PFCs.

• Molten NaOH has good mineralization effect on PFOS and PFBS.

Abstract

Current study proposes a green regeneration method of activated carbon (AC) laden with Perfluorochemicals (PFCs) from the perspective of environmental safety and resource regeneration. The defluorination efficiencies of AC adsorbed perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorobutanesulfonate (PFBS) using three molten sodium salts and one molten alkali were compared. Results showed that defluorination efficiencies of molten NaOH for the three PFCs were higher than the other three molten sodium salts at lower temperature. At 700°C, the defluorination efficiencies of PFOS and PFBS using molten NaOH reached to 84.2% and 79.2%, respectively, while the defluorination efficiency of PFOA was 35.3%. In addition, the temperature of molten salt, the holding time and the ratio of salt to carbon were directly proportional to the defluorination efficiency. The low defluorination efficiency of PFOA was due to the low thermal stability of PFOA, which made it difficult to be captured by molten salt.The weight loss range of PFOA was 75°C–125°C, which was much lower than PFOS and PFBS (400°C–500°C). From the perspective of gas production, fluorine-containing gases produced from molten NaOH-treated AC were significantly reduced, which means that environmental risks were significantly reduced. After molten NaOH treatment, the regenerated AC had higher adsorption capacity than that of pre-treated AC.

Graphical abstract

Keywords

PFCs / Molten sodium hydroxide / Thermal degradation / Activated carbon regeneration

References

[1] Cagnetta G, Robertson J, Huang J, Zhang K, Yu G (2016). Mechanochemical destruction of halogenated organic pollutants: A critical review. Journal of Hazardous Materials, 313: 85–102

[2] Chen J, Zhang P Y, Liu J (2007). Photodegradation of perfluorooctanoic acid by 185 nm vacuum ultraviolet light. Journal of Environmental Sciences (China), 19(4): 387–390

[3] Dai S, Zheng Y, Zhao Y, Chen Y, Niu D (2019b). Molten hydroxide for detoxification of chlorine-containing waste: Unraveling chlorine retention efficiency and chlorine salt enrichment. Journal of Environmental Sciences (China), 82: 192–202

[4] Dai S J, Zhao Y C, Niu D J, Li Q, Chen Y (2019a). Preparation and reactivation of magnetic biochar by molten salt method: Relevant performance for chlorine-containing pesticides abatement. Journal of the Air & Waste Management Association (1995), 69(1): 58–70

[5] Douvris C, Ozerov O V (2008). Hydrodefluorination of perfluoroalkyl groups using silylium-carborane catalysts. Science, 321(5893): 1188–1190

[6] Fagbayigbo B O, Opeolu B O, Fatoki O S, Akenga T A, Olatunji O S (2017). Removal of PFOA and PFOS from aqueous solutions using activated carbon produced from Vitis vinifera leaf litter. Environmental Science and Pollution Research International, 24(14): 13107–13120

[7] Flandinet L, Tedjar F, Ghetta V, Fouletier J (2012). Metals recovering from waste printed circuit boards (WPCBs) using molten salts. Journal of Hazardous Materials, 213–214: 485–490

[8] Harada K, Inoue K, Morikawa A, Yoshinaga T, Saito N, Koizumi A (2005). Renal clearance of perfluorooctane sulfonate and perfluorooctanoate in humans and their species-specific excretion. Environmental Research, 99(2): 253–261

[9] Higgins C P, McLeod P B, MacManus-Spencer L A, Luthy R G (2007). Bioaccumulation of perfluorochemicals in sediments by the aquatic oligochaete Lumbriculus variegatus. Environmental Science & Technology, 41(13): 4600–4606

[10] Hsu P C, Foster K G, Ford T D, Wallman P H, Watkins B E, Pruneda C O, Adamson M G (2000). Treatment of solid wastes with molten salt oxidation. Waste Management, 20(5–6): 363–368

[11] Khan M Y, So S, da Silva G (2020). Decomposition kinetics of perfluorinated sulfonic acids. Chemosphere, 238: 124615

[12] Krusic P J, Marchione A A, Roe D C (2005). Gas-phase NMR studies of the thermolysis of perfluorooctanoic acid. Journal of Fluorine Chemistry, 126(11–12): 1510–1516

[13] Li M, Sun F, Shang W, Zhang X, Dong W, Liu T, Pang W (2019a). Theoretical studies of perfluorochemicals (PFCs) adsorption mechanism on the carbonaceous surface. Chemosphere, 235: 606–615

[14] Li P, Zhi D, Zhang X, Zhu H, Li Z, Peng Y, He Y, Luo L, Rong X, Zhou Y (2019b). Research progress on the removal of hazardous perfluorochemicals: A review. Journal of Environmental Management, 250: 109488

[15] Lv H, Wang N, Zhu L, Zhou Y, Li W, Tang H (2018). Alumina-mediated mechanochemical method for simultaneously degrading perfluorooctanoic acid and synthesizing a polyfluoroalkene. Green Chemistry, 20(11): 2526–2533

[16] Mahieu E, Zander R, Toon G C, Vollmer M K, Reimann S, Mühle J, Bader W, Bovy B, Lejeune B, Servais C, Demoulin P, Roland G, Bernath P F, Boone C D, Walker K A, Duchatelet P (2013). Spectrometric monitoring of atmospheric carbon tetrafluoride (CF4) above the Jungfraujoch station since 1989: Evidence of continued increase but at a slowing rate. Atmospheric Measurement Techniques Discussions. 6, 7535–7563

[17] Meng P, Fang X, Maimaiti A, Yu G, Deng S (2019). Efficient removal of perfluorinated compounds from water using a regenerable magnetic activated carbon. Chemosphere, 224: 187–194

[18] Mitchell S M, Ahmad M, Teel A L, Watts R J (2014). Degradation of perfluorooctanoic acid by reactive species generated through catalyzed H₂O₂ propagation reactions. Environmental Science & Technology Letters, 1(1): 117–121

[19] Ochoa-Herrera V, Sierra-Alvarez R (2008). Removal of perfluorinated surfactants by sorption onto granular activated carbon, zeolite and sludge. Chemosphere, 72(10): 1588–1593

[20] Olsen E, Tomkute V (2013). Carbon capture in molten salts. Energy Science & Engineering, 1(3): 144–150

[21] Post G B, Cohn P D, Cooper K R (2012). Perfluorooctanoic acid (PFOA), an emerging drinking water contaminant: A critical review of recent literature. Environmental Research, 116: 93–117

[22] Rodriguez-Freire L, Balachandran R, Sierra-Alvarez R, Keswani M (2015). Effect of sound frequency and initial concentration on the sonochemical degradation of perfluorooctane sulfonate (PFOS). Journal of Hazardous Materials, 300: 662–669

[23] Sasi P C, Alinezhad A, Yao B, Kubátová A, Golovko S A, Golovko M Y, Xiao F (2021). Effect of granular activated carbon and other porous materials on thermal decomposition of per- and polyfluoroalkyl substances: Mechanisms and implications for water purification. Water Research, 200: 117271

[24] Sühnholz S, Kopinke F D, Weiner B (2018). Hydrothermal treatment for regeneration of activated carbon loaded with organic micropollutants. Science of the Total Environment, 644: 854–861

[25] Trojanowicz M, Bartosiewicz I, Bojanowska-Czajka A, Kulisa K, Szreder T, Bobrowski K, Nichipor H, Garcia-Reyes J F, Nalecz-Jawecki G, Meczynska-Wielgosz S, Kisala J (2019). Application of ionizing radiation in decomposition of perfluorooctanoate (PFOA) in waters. Chemical Engineering Journal, 357: 698–714

[26] Wang F, Lu X, Li X Y, Shih K (2015). Effectiveness and Mechanisms of defluorination of perfluorinated alkyl substances by calcium compounds during waste thermal treatment. Environmental Science & Technology, 49(9): 5672–5680

[27] Wang N, Lv H, Zhou Y, Zhu L, Hu Y, Majima T, Tang H (2019). Complete defluorination and mineralization of perfluorooctanoic acid by a mechanochemical method using alumina and persulfate. Environmental Science & Technology, 53(14): 8302–8313

[28] Wang W, Du Z, Deng S, Vakili M, Ren L, Meng P, Maimaiti A, Wang B, Huang J, Wang Y, Yu G (2018). Regeneration of PFOS loaded activated carbon by hot water and subsequent aeration enrichment of PFOS from eluent. Carbon, 134: 199–206

[29] Wu D, Li X, Zhang J, Chen W, Lu P, Tang Y, Li L (2018). Efficient PFOA degradation by persulfate-assisted photocatalytic ozonation. Separation and Purification Technology, 207: 255–261

[30] Xiao F, Sasi P C, Yao B, Kubatova A, Golovko S A, Golovko M Y, Soli D (2020). Thermal stability and decomposition of perfluoroalkyl substances on spent granular activated carbon. Environmental Science & Technology Letters, 7(5): 343–350

[31] Yao Z, Li J, Zhao X (2011). Molten salt oxidation: A versatile and promising technology for the destruction of organic-containing wastes. Chemosphere, 84(9): 1167–1174

Acknowledgements

This work was financially supported by the National Key R&D Program of China (No. 2019YFC1904400). The authors are grateful to the reviewers who help us improve the paper by many pertinent comments and suggestions.

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11783-022-1524-9 and is accessible for authorized users.

RIGHTS & PERMISSIONS

2022 Higher Education Press