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 Trifluoroacetic acid (TFA) is an ultrashort‐chain perfluoroalkyl acid characterized by high mobility, environmental persistence, and resistance to conventional treatment and natural attenuation. It is widely detected in precipitation, surface water, groundwater, and drinking water, and often dominates per‐ and polyfluoroalkyl substances (PFAS) profiles in aqueous systems. This study synthesizes available data on TFA occurrence, toxicity, and treatment to evaluate its environmental behavior and management challenges. Toxicity data indicate low intrinsic toxicity across aquatic, terrestrial, and mammalian systems, with effects observed at concentrations well above typical environmental levels. Interpretation remains limited by variability in analytical methods and gaps in long‐term and cross‐species data. Treatment technologies developed for legacy PFAS are largely ineffective for TFA. Sorption‐ and interfacial‐based processes provide negligible removal, while separation processes, such as reverse osmosis, concentrate TFA into residual streams. Many oxidative, electrochemical, and plasma‐based systems do not achieve mineralization and may generate TFA as a terminal product. Only a limited number of technologies demonstrate defluorination under controlled conditions, with hydrothermal alkaline treatment (referred to as HALT) among the few approaches achieving complete defluorination. Overall, TFA represents a practical limitation of current PFAS management strategies, with persistence through treatment systems likely leading to increasing dominance in treated waters and expansion of diffuse plumes.
ABSTRACT Vapor intrusion (VI) investigations involve the performance of environmental assessments for the potential presence of vapor‐forming chemicals in groundwater, soil, exterior and interior (sub‐slab) soil vapor, and indoor air. VI‐decision‐making is generally guided by simple comparisons of detected concentrations to media‐specific screening levels. Such investigations are often conducted in an iterative manner, wherein VI studies may proceed from groundwater to soil vapor to indoor air, depending on data reduction outcomes. This study considers seven “problematic” compounds that can often confound VI investigations. For these compounds, screening level exceedances may not necessarily be reflective of a complete VI pathway. The rationale varies, with two compounds (1,3‐butadiene and acrolein) sometimes reported in soil vapor potentially due to sampling and analytical false positives, vinyl chloride removed from shallow soil vapor via aerobic biodegradation, carbon tetrachloride present in indoor air due to outdoor sources, and three compounds (chloroform, 1,4‐dichlorobenzene, and 1,2‐dichloroethane) potentially present in indoor air due to indoor air emission sources. Accordingly, strategies and considerations are provided for VI practitioners to understand and address when these compounds are reported in VI studies.
