Regeneration of biochars (pristine and modified/engineered) and economic analysis of their use in the removal of per- and polyfluoroalkyl substances (PFAS) from water/wastewater

doi:10.1007/s11783-025-1940-8

2025, Vol. 19

Issue (2) : 20 https://doi.org/10.1007/s11783-025-1940-8

Regeneration of biochars (pristine and modified/engineered) and economic analysis of their use in the removal of per- and polyfluoroalkyl substances (PFAS) from water/wastewater

Shahryar Jafarinejad¹, Jianzhou He², Dengjun Wang³(

)

¹. Department of Chemical Engineering, College of Engineering, Tuskegee University, Tuskegee, AL 36088, USA
². Department of Biochemistry, Chemistry & Physics, Georgia Southern University, Savannah, GA 31419, USA
³. Department of Agricultural and Biological Engineering, University of Florida, Gainesville, FL 32611, USA

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Abstract

Currently, there is an increasing interest in developing efficient and cost-effective treatment technologies to remediate per- and polyfluoroalkyl substances (PFAS) in water. Biochars (pristine and modified/engineered) can be a good candidate among porous pyrogenic carbonaceous materials for the sorptive removal of PFAS from water/wastewater. There is a need to focus on developing efficient, environmentally friendly, and cost-effective techniques for desorbing PFAS from spent biochars (pristine and modified/engineered) to enable potential reuse or suitable disposal of these adsorbents, facilitating their future full-scale application in the water sector. This review article briefly compiles the state-of-the-art knowledge on the: (i) application of pristine and modified/engineered biochars for the sorptive removal of PFAS from aqueous samples; (ii) regeneration/reuse techniques for the spent biochars; and (iii) economic analysis of their use in PFAS removal from water/wastewater. Further investigations on (i) better modifying/engineering biochars to remove specially short-chain PFAS species in real environmental water samples due to challenging nature of their removal using conventional treatment technologies; (ii) feasible low-energy, environmentally friendly, and cost-effective strategies for regeneration/reuse of the spent biochars (pristine and modified/engineered) and management of their end-of-life; and (iii) large-scale and continuous column sorption operation for the real water/wastewater samples are still desirable to apply biochars for PFAS removal at full-scale in the future.

Keywords Per- and polyfluoroalkyl substances Biochar Sorption Water Reuse Cost

Corresponding Author(s): Dengjun Wang

Issue Date: 21 November 2024

Cite this article:

Shahryar Jafarinejad,Jianzhou He,Dengjun Wang. Regeneration of biochars (pristine and modified/engineered) and economic analysis of their use in the removal of per- and polyfluoroalkyl substances (PFAS) from water/wastewater[J]. Front. Environ. Sci. Eng., 2025, 19(2): 20.

URL:

https://academic.hep.com.cn/fese/EN/10.1007/s11783-025-1940-8
https://academic.hep.com.cn/fese/EN/Y2025/V19/I2/20

Guideline/Standard	Year updated	Type	Promulgated rule	PFOA (ng/L)	PFOS (ng/L)
US EPA, Maximum contaminant level*	2024*	DW*	Yes*	4*	4*
US EPA, Maximum contaminant level goal*	2024*	DW*	No*	0*	0*
US EPA, Interim lifetime health advisory	2022	DW	No	0.004	0.02
US EPA, Regional screening level	2023	DW/GW	No	60	40
Alaska, Groundwater cleanup level	2016	GW	Yes	400	400
Alaska, Action level	2018	DW/GW/SW	No	70	70
California, Notification level	2022	DW	No	5	7
California, Reporting level	2022	DW	Yes	10	40
California, Public health goal	2024	DW	No	0.007	1
Colorado, Site-specific groundwater quality standard	2018	GW	Yes	70	70
Colorado, Translation levels	2020	GW/SW	Yes	70	70
Connecticut, Action level	2023	DW/GW	No	16	10
Connecticut, Additional polluting substance groundwater protection criteria	2018	GW	No	70	70
Delaware, Reporting level	2016	GW	No	70	70
Delaware, Screening level	2023	GW	Yes	6	4
Florida, Provisional groundwater target cleanup level	2020	GW	Other	70	70
Florida, Screening level	2020	SW	Other	500	10
Hawaii, Environmental action level	2021	GW	Other	40	40
Illinois, Health-based guidance level	2021	DW/GW	Other	2	14
Iowa, Statewide standards	2016	Protected GW	Yes	70	70
Maine, Remedial action guideline	2023	GW-Residential	Other	60	40
Maine, Interim DW standard	2021	DW	Other	20	20
Massachusetts, Drinking water values	2018/2019	DW	Other	20	20
Massachusetts, GW-1	2019	GW	Yes	20	20
Massachusetts, Maximum contaminant level	2020	DW	Yes	20	20
Michigan, Human noncancer value for surface drinking water	2023	SW	Yes	66	11
Michigan, Screening levels	2019	DW	No	9	8
Michigan, Maximum contaminant level/Generic cleanup criteria	2021	DW/GW	Yes	8	16
Minnesota, Health risk limit - subchronic, chronic	2023	DW/GW	Yes	35	300
Minnesota, Health-based value–subchronic, chronic	2024	DW/GW	No	0.24	2.3
Minnesota, Health-based value–cancer	2024	DW/GW	No	0.0079	7.6
Minnesota, Water quality standard	2023	SW-lake	Yes/No	25	0.05
Montana, Water quality standard	2019	GW	Yes	70	70
Nevada, Basic comparison level	2023	DW	No	100	70
New Hampshire, Ambient groundwater quality standard	2019	GW	Yes	12	15
New Hampshire, Maximum contaminant level	2020	DW	Yes	12	15
New Jersey, Maximum contaminant level	2020	DW	Yes	14	13
New Mexico, Preliminary screening levels	2022	DW	No	60.2	60
New York, Maximum contaminant level	2020	DW	Yes	10	10
Ohio, Action level	2022	DW	Other	70	70
Oregon, Health advisory level	2021	DW	No	30	30
Pennsylvania, Medium-specific concentration	2021	GW	Other	14	18
Pennsylvania, Maximum contaminant level	2023	DW	Yes	14	18
Rhode Island, Groundwater quality standard	2023	DW/GW	Yes	20	20
Rhode Island, Maximum contaminant level	2022	DW	Yes	20	20
Rhode Island, Action level	2023	SW	Yes	70	70
Texas, Tier 1 protective concentration level	2023	GW	Yes	290	560
Vermont, Maximum contaminant level	2020	DW/GW	Yes	20	20
Vermont, Lifetime health advisory	2018	DW/GW	Yes	20	20
Vermont, Groundwater enforcement standard	2019	GW	Yes	20	20
Vermont, Preventive action level	2019	GW	Yes	2	2
Washington, State action level	2022	GW	Yes	10	15
Washington, State action level	2022	DW	Yes	10	15
Wisconsin, Maximum contaminant level	2022	DW	Other	70	70

Tab.1 The guideline values for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in groundwater (GW), drinking water (DW), and surface water (SW)/effluent in the United Sates

Adsorbent	Target PFAS	Water matrix	Experimental mode	Major findings (sorption performance/capacity)	Reference
Biochar without biofilm	PFBS, PFHxS, PFOS, FOSA, PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, and PFDoDA	Synthetic solution	Column	The removal efficiency (20%–60%) and sorption capacity (0–88 ng ∑PFAS/g biochar) for short-chain PFCAs (C₃–C₆) and PFSA (C₄)The removal efficiency (90%–99%) and the sorption capacity (73–168 ng ∑PFAS/g biochar) for C₇–C₁₁ PFCAs, C₆, C₈ PFSAs, and FOSA	Dalahmeh et al. (2019)
Hardwood (oak)-based biochar	PFOS and PFOA	Synthetic solution	Column	Up to 89% PFOA removal and up to 99% PFOS removal	Liu et al. (2019)
Magnesium chloride-treated biochar	PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoA, PFTeDA, PFHxDA, PFOcDA, PFBS, PFHxS, PFOS, FOSA, and FTSAs	Synthetic solution	Batch	PFAS sorption to magnesium chloride-treated biochar was 17–25-fold higher than to sand	Sörengård et al. (2020)
Hardwood (oak)-based biochar	PFOA, PFHpA, PFHxA, PFPeA, PFBA, PFOS, PFHpS, PFHxS, and PFBS	Synthetic solution	Batch	About 60% removal of PFOA, 94% removal of PFOS, 17% removal of PFHpA, 60%–70% removal of PFHpS, 30%–40% removal of PFHxS, and 20% removal of PFBS by the mixture of zero-valent iron and biochar (ZVI + BC)	Liu et al. (2020)
Softwood-derived biochar	PFOA, PFOS, PFBA, and PFBS	Synthetic solution	Batch	The maximum Langmuir sorption capacity for PFOA (52.08 ± 14.8?µmol/g), PFOS (70.42 ± 21.5 µmol/g), PFBA (48.31 ± 12.2 µmol/g), and PFBS (23.36 ± 7.4 µmol/g)	Zhang et al. (2021)
Activated spent coffee grounds biochar or SCGKOH (produced from a 1:1 mass ratio of pyrolyzed spent coffee grounds and potassium hydroxide)	PFOS	Synthetic solution	Batch	Sorption capacity of 43.4 mg/g	Steigerwald and Ray (2021)
Reed straw-derived biochar	PFBA, PFBS, PFHxA, PFHxS, PFOA, and PFOS	Synthetic solution and PFAS-spiked groundwater	Batch and column	Batch: 92%–96% removal efficiency for three short-chain PFAS (i.e., PFBA, PFBS, and PFHxA) Column: effective removal using reed straw-derived biochar-packed filter with the flow rate up to 45 mL/min	Liu et al. (2021)
Commercial Douglas fir biochar (BC) and Fe₃O₄-containing BC (Fe₃O₄/BC)	PFOS and PFOA	Synthetic solution	Batch	Sorption capacities of PFOS were 7–14.6 mg/g BC and 6.2–10.7 mg/g Fe₃O₄/BCSorption capacities of PFOA were 3.9–9 mg/g BC and 5.4–652 mg/g Fe₃O₄/BC	Rodrigo et al. (2022)
Sugarcane biochar	19 PFAS including 11 PFCAs (C₃–C₁₃) and 8 PFSAs (C₄–C₁₂)	PFAS-spiked Milli-Q water and aqueous film-forming foams-impacted groundwater	Column	1.3-fold higher sorption of PFSAs by biochar compared to PFCAs	Vo et al. (2022)
Non-modified biochars and engineered biochars using different feedstocks (switchgrass, water oak, and biosolid) and additives (FeCl₃ and carbon nanotube)	PFOA	Synthetic solution	Batch	Sorption capacity of PFOA in the range of 39.54–469.65 μmol/g Better sorption capacities for PFOA using biosolid biochar and Fe-impregnated biochar	Wu et al. (2022)
Two halophyte biochars and cow bone biochar	PFOA, PFOS, and PFHxS	Brackish groundwater	Batch	All PFOS and PFHxS removal and 86% removal of PFOA by one of the halophyte biochars (at a dose of 1000 mg/L)	Papes (2022)
Commercial biochar and biochars from corn, Douglas fir, eucalyptus, poplar, and switchgrass	PFOS	Synthetic solution	Batch	Over 95% PFOS removal using Douglas fir biochar, poplar biochar, and commercial biochar	Krebsbach et al. (2023a)
Unmodified biochar and modified biochars (post-pyrolysis air oxidation-treated biochar and poly(dimethyldiallylammonium) chloride (pDADMAC)-coated biochar)	GenX, PFBA, PFPeA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFBS, PFHxS, and PFOS	Synthetic solution	Batch	Coating with pDADMAC enhanced PFAS sorption by a factor of 10–3000	Wang et al. (2023a)
Commercial biochar (CB) and biosolids biochar (BB)	PFOA, PFOS, and PFHxS	Synthetic solution	Batch	CB outperformed BB with 88.06%–100% and 59.09–100% PFAS sorption in the single and multiple PFAS adsorption experiments, respectively	Nguyen et al. (2023)
Biochar and biochar-polymer composite (BC-P(SB-co-AM))	PFOS, PFOA, PFBA, and PFBS	Synthetic solution	Batch	The maximum sorption capacities of PFOS, PFOA, PFBS, and PFBA were 634, 536, 301, and 264 mg/g, respectively for BC-P(SB-co-AM)	Deng et al. (2023)
Polypyrrole/biochar (PPy/BC) composites	PFOS, PFOA, PFBA, and PFBS	Synthetic solution and river surface water	Batch	Sorption capacities of PFBA, PFBS, PFOA, and PFOS were 3.89, 1.53, 2.55, and 1.22 mmol/g, respectively.Above 95% removal of multiple PFAS from actual PFAS-contaminated surface water	Yu et al. (2023)
Biochar-alginate composite beads	PFOS and PFBS	Synthetic solution	Batch	Up to 99% removal efficiency of PFOS using 1.5 g/L of biochar-alginate composite beads in less than16 h	Militao et al. (2023)
Modified biochars prepared from different biomass materials (straw, wood chips, sludge, and chicken manure) and modification methods (e.g., acid (hydrochloric acid), alkali (sodium hydroxide), and oxidant (potassium permanganate) modifications)	PFOS and PFOA	Synthetic solution	Batch	Theoretical maximum sorption capacities of PFOS and PFOA were 72.17 and 45.88 mg/g, respectively for the acid-modified, 300 °C pyrolyzed, sludge-derived biochar	Zhang et al. (2023)
Raw softwood (mixed species) or hardwood (maple)-derived biochars and post-pyrolysis air oxidation (PPAO)-treated biochars	PFBA, PFPeA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFBS, PFHxS, PFOS, and GenX	Synthetic solution	Batch	PPAO treatment can significantly enhance the sorption potential of biochars	Wang et al. (2023b)
Construction and demolition debris-wood-derived biochar	92 PFAS	Landfill leachate	Batch and column	Batch: achieving a maximum of 29% PFAS reduction compared to controlsColumn: Producing leachates with PFAS concentrations 50%–80% higher than those in control columns	Cerlanek et al. (2024)

Tab.2 Recent studies on the application of pristine and modified/engineered biochars for the sorptive remediation of PFAS from aqueous samples

Adsorbents	Target PFAS	Regeneration technique	Regeneration results	Reference
Biochar (BC) and Fe₃O₄-containing BC (Fe₃O₄/BC)	PFOS and PFOA	Chemical regeneration using methanol	Better cyclic sorption-desorption for PFOS compared to PFOASimilar results in cyclic uptake-recovery tests with PFOS for BC and Fe₃O₄/BC despite slight capacity differences in desorptionBC and Fe₃O₄/BC can be utilized for several sorption cycles	Rodrigo et al. (2022)
Spent coffee grounds biochar (“SCGKOH”) and molecularly imprinted polymer coated SCGKOH biochar	PFOS, PFOA, and PFBS	Chemical regeneration using a 70% methanol, 1% sodium chloride solution	Successful regeneration of spent adsorbents	Steigerwald (2022)
Polypyrrole/biochar (PPy/BC) composites	PFOS, PFOA, PFBA, and PFBS	Chemical regeneration using different solvents (e.g., methanol, acetonitrile, methanol solution containing 1 mol/L sodium hydroxide, 70% methanol solution containing 1 mol/L sodium hydroxide, and single 1 mol/L sodium hydroxide solution)	Methanol as the optimal regeneration agentSuitable regeneration/reuse of spent PPy/BC composites at least five times	Yu et al. (2023)
Biochar and biochar-polymer composite (BC-P(SB-co-AM))	PFOS, PFOA, PFBA, and PFBS	Chemical regeneration using sodium chloride, sodium iodide, sodium hydroxide, and ethanol	Sorption efficiency following regeneration using sodium chloride, sodium iodide, sodium hydroxide, and ethanol were 1.3%–3.6%, 1.1%–2.2%, 3.8%–20.6%, and 11.2%–26.9%, respectively	Deng et al. (2023)
Biochar and biochar-polymer composite (BC-P(SB-co-AM))	PFOS, PFOA, PFBA, and PFBS	Vacuum-ultraviolet (VUV)/sulfite reduction system	Removal efficiency of PFOS (80.8%), PFOA (90.4%), PFBS (58.8%), and PFBA (70.6%) after the first regenerationRemoval efficiency of PFOS (56.2%), PFOA (55.7%), PFBS (29.6%), and PFBA (45.1%) after the third regenerationRemoval efficiency of PFOS (33.8%), PFOA (40.2%), PFBS (23.4%), and PFBA (31.8%) after the fourth regeneration	Deng et al. (2023)
Biochar and biochar-polymer composite (BC-P(SB-co-AM))	PFOS, PFOA, PFBA, and PFBS	Heat treatment (heating saturated adsorbent with PFAS in a regeneration solution at 50 °C for 12 h)	The removal efficiencies of PFOS, PFOA, PFBS, and PFBA were 78.3%, 82.2%, 65.8%, and 60.8%, respectively for the regenerated adsorbentThe removal efficiency of long-chain PFAS was greater than 60% after five cyclesThe removal efficiencies of PFOS, PFOA, PFBS, and PFBA were 96.2%, 94.3%, 90.8%, and 85.8%, respectively after first regeneration using heat treatment combined with sodium iodide and sodium hydroxide solution. Also, the removal efficiency was greater than 70% after five cycles	Deng et al. (2023)
Softwood (pyrolyzed at 600 °C)-post-pyrolysis air oxidation (PPAO)-treated biochar	PFBA, PFPeA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFBS, PFHxS, PFOS, and GenX	Thermal treatment at 500 °C in air	Reactivated softwood (pyrolyzed at 600 °C)-PPAO-treated biochar showed greater PFAS K_D values compared to that of the original	Wang et al. (2023b)

Tab.3 Recent regeneration studies on pristine and modified/engineered biochars

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