ABSTRACT There is significant confusion regarding the validity and applicability of various analytical techniques for assessing per‐ and polyfluoroalkyl substances (PFAS) in consumer products. Specifically, the type and scope of information provided by commonly used PFAS‐related analytical assays, both individually and in combination, have not been thoroughly evaluated using consumer product examples. Although reviews of these methodologies exist, no study has translated their theoretical capabilities into practical applications using real‐world products. TRC, in partnership with Pace® Analytical Services, performed a study that aimed to quantify PFAS and fluorine content in three distinct consumer products using total fluorine, total inorganic fluoride, solvent extraction, and leachate analyses to assess PFAS presence and potential PFAS release or migration under the tested conditions. To maximize public relevance and the likelihood of detecting measurable PFAS concentrations, we selected consumer products that have been alleged in recent media reports for potential PFAS content. By comparing results across these assays, we summarize the strengths and limitations of each method and assess how data interpretation varies depending on the analytical approach used. Leachate analyses were used to evaluate arguments surrounding what remains bound in a matrix versus what may be potentially available for exposure; these analyses can allow the user to evaluate if PFAS detection necessarily indicates PFAS exposure or risks to human health. Understanding the results of this study will be critical as PFAS‐related litigation on consumer products continues to escalate. Given the ongoing debate over which PFAS testing methods are legally and scientifically defensible, this paper may inform interpretation of analytical evidence in regulatory and legal contexts and includes a well‐documented understanding of method limitations and analytical challenges of consumer products and why a multi‐method approach may be necessary for risk assessment in some contexts.
ABSTRACT Petroleum hydrocarbon contamination of aquatic environments in the Niger Delta region of Nigeria requires remediation approaches that combine effectiveness, simplicity, and the utilization of renewable materials. This study investigated the application of unmodified lignin isolated from sandbox ( Hura crepitans ) seed capsules for the remediation of aged crude‐oil–contaminated surface water from Okerenkoko creeks in Delta State, Southern Nigeria. Lignin was isolated by alkaline extraction, followed by acid precipitation, and characterized using UV–Visible spectroscopy, Fourier‐transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface‐area analysis, and Thermogravimetric/differential thermogravimetric (TGA/DTG) analysis. Batch remediation experiments were conducted by varying the adsorbent dosage, pH, temperature, and agitation rate, whereas total petroleum hydrocarbon (TPH) removal kinetics were evaluated using pseudo‐first‐order, pseudo‐second‐order, Elovich, intraparticle‐diffusion, zero‐order, first‐order, and second‐order models. The alkaline extraction yielded 46.20% lignin. The isolated lignin showed a BET surface area of 4.4 m 2 g −1 , pore volume of 0.015 cm 3 g −1 , and an average pore diameter of 8.7 nm. FTIR analysis revealed characteristic lignin functional groups, whereas SEM showed an irregular and heterogeneous surface morphology. TGA/DTG analysis indicated the thermal stability and multistage decomposition behavior of the lignin. Optimum treatment conditions were achieved at an adsorbent dosage of 0.8 g, pH 5, a temperature of 25°C, and an agitation rate of 300 rpm. Under these conditions, the maximum observed TPH removal at 180 min was 68.82%, corresponding to an adsorption capacity of 23.53 mg g −1 . The pseudo‐second‐order model provided the best kinetic description of TPH removal, with a high coefficient of determination ( R 2 = 0.981), indicating that the adsorption process was predominantly controlled by interactions between the lignin surface and petroleum hydrocarbon constituents. The intraparticle‐diffusion model showed a non‐zero intercept, indicating that intraparticle diffusion was not the sole rate‐controlling mechanism. The findings demonstrate that unmodified H. crepitans lignin can serve as a renewable and effective bio‐based adsorbent for the treatment of aged crude‐oil–contaminated creek water under near‐ambient conditions. Its availability, simple preparation, and measurable TPH‐removal performance highlight its potential as a low‐cost and environmentally compatible material for petroleum hydrocarbon remediation in the Niger Delta region of Nigeria.
ABSTRACT Granular activated carbon (GAC) is widely recognized as a best available technology (BAT) for the removal of per‐ and polyfluoroalkyl substances (PFAS) from both drinking water and wastewater—capable of achieving the low nanogram per liter (ng/L) effluent concentrations required for regulatory compliance. PFAS removal is achieved through adsorption within the extensive internal pore structure of the GAC. Once the GAC reaches its adsorption capacity for PFAS—otherwise denoted as spent GAC—standard practice is to return the spent GAC to a thermal reactivation facility. Thermal reactivation is a high‐temperature process that removes adsorbed contaminants from GAC and restores internal pore structure for subsequent reuse. As PFAS regulatory requirements continue to become more stringent, there is an increasing need for transparency regarding the fate of PFAS during thermal reactivation of spent GAC, including consideration of greenhouse gas emissions and the potential formation of products of incomplete combustion and products of incomplete destruction (PICs/PIDs). A comprehensive testing plan was conducted at a full‐scale facility treating PFAS‐laden spent carbon from industrial treatment sources to demonstrate both the degree of PFAS destruction and to test for the presence of PICs/PIDs in process emissions. The study utilized U.S. Environmental Protection Agency (U.S. EPA) OTM‐45, U.S. EPA OTM‐50, and U.S. EPA Method 0010/8270 with inclusion of fluorinated PICs/PIDs to fully characterize vapor‐phase emissions from the reactivation process. Reactivated carbon samples were below the limits of detection for 72 PFAS analytes. The process achieved both destruction and removal efficiency (DRE) and destruction efficiency (DE) of > 99.999% for total analyzed PFAS with > 99.9999% DRE observed for individual PFAS. Stack emissions were below the detection limits of U.S. EPA OTM‐50 and U.S. EPA Methods 0010/8270 demonstrating the absence of select PICs/PIDs in emissions at standard operating conditions. Together, these findings demonstrate that full‐scale thermal reactivation can reliably achieve high levels of PFAS destruction while processing highly loaded spent GAC without the release of undesirable byproducts.
ABSTRACT Biochar‐supported zero‐valent iron (ZVI‐biochar) is a promising material for groundwater remediation, and carbothermal reduction offers a simple, potentially scalable route for its production. However, this method requires high temperatures and typically results in low Fe(0) formation. This study demonstrates that introducing CO 2 during pyrolysis markedly enhances in situ Fe(0) formation at lower temperatures while simultaneously improving material reactivity and stability. Beech wood‐derived ZVI‐biochar prepared under a CO 2 :N 2 (1:9, v/v) atmosphere at 900°C exhibited a 1.7‐fold higher trichloroethylene (TCE) removal rate and a sixfold higher Fe‐normalized TCE dechlorination rate compared to that produced without CO 2 addition. The improved TCE reactivity (removal extent and rate) was primarily attributed to enhanced reductive transformation, driven by both increased Fe(0) formation and CO 2 ‐induced changes in the biochar matrix. The resulting ZVI‐biochar exhibited lower corrosion rates than other reported ZVI reactants and maintained high TCE reactivity even after prolonged exposure to air or water. It also achieved complete removal of other chlorinated ethylenes, including cis‐dichloroethylene and vinyl chloride, from contaminated groundwater. These findings demonstrate that CO 2 ‐assisted carbothermal treatment offers a simple and potentially scalable route for producing stable and reactive ZVI‐biochar composites for groundwater remediation, while avoiding the need for multi‐step syntheses using chemical reductants.
ABSTRACT There is a critical need to understand if synthetic precipitation leaching procedure (SPLP) or equivalent tests are sufficiently representative for the purpose of estimating soil‐to‐groundwater mass discharge of per‐ and polyfluoroalkyl substances (PFAS). A mass balance approach was derived to define the complex relationship between SPLP leachate and in situ porewater concentrations. Differences in SPLP leachate and porewater are expected to occur due to PFAS adsorption to air–water interfaces and the large liquid‐to‐liquid dilution factor (LLDF) associated with SPLP tests. This study analyzed 24 PFAS analyte results for co‐located soil, SPLP, and porewater samples collected at 15 lysimeters at Ellsworth Air Force Base, an aqueous film‐forming foam (AFFF)‐impacted site. SPLP tests overestimated perfluorooctanesulfonic acid concentrations in porewater by up to an order of magnitude because SPLP does not account for adsorption to the air–water interface. SPLP also underestimated short‐chain PFAS concentrations in porewater by up to two to three orders of magnitude due to the large LLDF associated with SPLP tests. Porewater concentrations calculated based on SPLP leachate concentrations, and accounting for the LLDF and estimated air–water interface partitioning, differ from observed porewater concentrations by up to an order of magnitude. Visualization of PFAS using radial diagrams and stacked bar maps was effective for demonstrating these trends on a single figure, and for showing that the PFAS composition in SPLP leachate samples was different than the composition in porewater samples. Differences observed in PFAS concentration between SPLP leachate and porewater concentrations may occur at a wide range of other AFFF‐impacted sites. Based on the results of this study, caution should be employed when considering the use of SPLP leachate concentrations for estimating PFAS mass discharge or soil screening levels in the vadose zone. Porewater sampling is the most direct and authoritative metric for estimating PFAS mass discharge in the vadose zone at sites such as Ellsworth AFB.
