Removal Of Polycyclic Aromatic Hydrocarbons Research Articles

COF-300/PVDF adsorbents with aligned microchannels for fast removal of polycyclic aromatic hydrocarbons (PAHs)

Anthropogenic release of polycyclic aromatic hydrocarbons (PAHs) in water bodies has raised global concerns due to their notorious toxicity and carcinogenicity, therating aquatic exosystems and human well-being. Adsorption processes have been proposed for PAHs remediation, but their practical applications are limited by the lack of high-performance adsorbents and effective manufacturing processes. Here, we present a facile and scalable method to produce a COF-300/PVDF composite as a high-performance adsorbent for PAHs removal. The composite comprises a porous PVDF substrate containing numerous aligned microchannels in its entire cross-section where COF-300 is fully coated. The adsorption capacities of the COF-300 powder towards two sample PAH pollutants, i.e. naphthalene and 1-naphthylamine, are 655 and 570 mg g−1, respectively, which are among the highest reported values. The composite adsorbent demonstrates better adsorption kinetics and removal efficiencies than the COF-300 powders at the same feed input of 1.44 L h-1g−1, and its superior performance has been further highlighted through a comparative study with a COF-300 pack column and COF-300/PVDF mixed matrix membranes. These results suggest that the newly developed COF-300/PVDF composite holds great potential in practical applications for PAHs removal.

Mechanism of polycyclic aromatic hydrocarbons degradation in the rhizosphere of Phragmites australis: Organic acid co-metabolism, iron-driven, and microbial response

Microbial co-metabolism is crucial for the efficient biodegradation of polycyclic aromatic hydrocarbons (PAHs); however, their intrinsic mechanisms remain unclear. To explore the co-metabolic degradation of PAHs, root organic acids (ROAs) (phenolic ROAs: caffeic acid [CA] and ferulic acid [FA]; non-phenolic ROAs: oxalic acid [OA]) were exogenously added as co-metabolic substrates under high (HFe) and low (LFe) iron levels in this study. The results demonstrated that more than 90% of PAHs were eliminated from the rhizosphere of Phragmites australis. OA can promote the enrichment of unrelated degrading bacteria and non-specific dioxygenases. FA with a monohydroxy structure can activate hydroxylase; however, it relies on phytosiderophores released by plants (such as OA) to adapt to stress. Therefore, non-specific co-metabolism occurred in these units. The best performance for PAH removal was observed in the HFe–CA unit because: (a) HFe concentrations enriched the Fe-reducing and denitrifying bacteria and promoted the rate-limiting degradation for PAHs as the enzyme cofactor; (b) CA with a dihydroxyl structure enriched the related degrading bacteria, stimulated specific dioxygenase, and activated Fe to concentrate around the rhizosphere simultaneously to perform the specific co-metabolism. Understanding the co-metabolic degradation of PAHs will help improve the efficacy of rhizosphere-mediated remediation.

Continuous fixed-bed column studies to remove polycyclic aromatic hydrocarbons by degrading enzymes immobilized on polyimide aerogels

The main sources of polycyclic aromatic hydrocarbons (PAHs), entering aquatic environments are industrial discharges, petroleum spills, combustion of fossil fuels, urban runoff, and atmospheric deposition. For the biodegradation of PAHs, the use of biocatalysts, such as enzymes, is an environmentally friendly method. Despite this, it is necessary to immobilize the enzymes to facilitate their recovery and reusability, as well as to prevent their loss. Using covalent bonding, (PAHs) degrading enzymes including naphthalene and catechol 2,3 dioxygenase enzymes were immobilized on modified polyimide aerogels. Covalent immobilization of enzymes on surface-modified polyimide aerogels resulted in around 9- and 6-fold lower enzyme leaching for naphthalene and catechol 2,3 dioxygenase enzymes compared to enzyme immobilization using adsorption. The Fourier Transform Infrared Spectrum (FT-IR) confirmed the enzyme immobilization and aerogel modification. SEM images indicated completely different textures for surface-modified aerogel attributed to the presence of functional groups after surface modification that enhanced enzyme loading. The removal capacity (∼20mganthracenegaerogel) of enzyme loaded aerogel was determined to select an appropriate range for column tests. Finally, the effects of flow rate, size of aerogels and inlet concentration of anthracene on the removal efficiency of pollutants were examined. Using the derived model as a basis for prediction, in terms of removal efficiency, the highest result was achieved to be 84.01% at a flow rate of 22 mL min−1, initial concentration of 34 mg L−1and aerogel size of 2 cm while under these conditions, the removal efficiency was experimentally measured to be 87.14 %. A fixed-bed column packed with enzyme-loaded aerogel for the removal of PAHs provides novel insight into the application of aerogel base materials for water treatment and PAH removal with possibilities of scaling up for larger applications.

Enhanced removal of phenanthrene and nutrients in wetland sediment with metallic biochar: Performance and mechanisms

Polycyclic aromatic hydrocarbon (PAHs) are persistent organic pollutants and pose high risk in aquatic environment. The utilization of biochar is a strategy for PAHs-contaminated remediation but is challenging due to the adsorption saturation and reoccurrence of PAHs desorbed back into water. In this study, iron (Fe) and manganese (Mn) were provided as electron acceptors for biochar modification to enhance anaerobic biodegradation of phenanthrene (Phe). Results revealed that, the Mn(Ⅳ) and Fe(Ⅲ) modification improved the removal of Phe by 24.2% and 31.4% than that of biochar, respectively. Additionally, nitrate removal was improved by 19.5% with Fe(Ⅲ) amendment. The Mn-and Fe-biochar decreased Phe contents by 8.7% and 17.4% in sediment, 10.3% and 13.8% in biochar than that of biochar. Much higher DOC contents were observed with Mn- and Fe-biochar, which provided bioavailable carbon source for microbes and contributed to microbial degradation of Phe. The greater degree of humification, higher proportions of humic and fulvic acid like components in metallic biochar participated in electron transport and further enhancing the degradation of PAHs. Microbial analysis proved the high abundance of Phe-degrading bacteria (e.g. PAH-RHDα, Flavobacterium and Vibrio), nitrogen removal microbes (e.g. amoA, nxrA, and nir), Fe and Mn bioreduction or oxidation (e. g. Bacillus, Thermomonas, Deferribacter) with metallic biochar. Based on the results, the Fe and Mn modification, especially Fe-modified biochar provided well performance for PAHs removal in aquatic sediment.

Rhodococcus Strains from the Specialized Collection of Alkanotrophs for Biodegradation of Aromatic Compounds

The ability to degrade aromatic hydrocarbons, including (i) benzene, toluene, o-xylene, naphthalene, anthracene, phenanthrene, benzo[a]anthracene, and benzo[a]pyrene; (ii) polar substituted derivatives of benzene, including phenol and aniline; (iii) N-heterocyclic compounds, including pyridine; 2-, 3-, and 4-picolines; 2- and 6-lutidine; 2- and 4-hydroxypyridines; (iv) derivatives of aromatic acids, including coumarin, of 133 Rhodococcus strains from the Regional Specialized Collection of Alkanotrophic Microorganisms was demonstrated. The minimal inhibitory concentrations of these aromatic compounds for Rhodococcus varied in a wide range from 0.2 up to 50.0 mM. o-Xylene and polycyclic aromatic hydrocarbons (PAHs) were the less-toxic and preferred aromatic growth substrates. Rhodococcus bacteria introduced into the PAH-contaminated model soil resulted in a 43% removal of PAHs at an initial concentration 1 g/kg within 213 days, which was three times higher than that in the control soil. As a result of the analysis of biodegradation genes, metabolic pathways for aromatic hydrocarbons, phenol, and nitrogen-containing aromatic compounds in Rhodococcus, proceeding through the formation of catechol as a key metabolite with its following ortho-cleavage or via the hydrogenation of aromatic rings, were verified.

Review on bioremediation technologies of polycyclic aromatic hydrocarbons (PAHs) from soil: Mechanisms and future perspective

Polyaromatic hydrocarbon (PAHs) are a large class of organic compounds that contain two or more fused aromatic rings form by the incomplete combustion of carbonaceous material. PAHs are ubiquitous pollutants that spread throughout the environment (atmosphere, soil, and water) and pose a serious threat to human cell and living organism. Due to its adverse effects, human PAH intakes must be continuously and consistently monitored. This review paper emphasis on successful and efficient application of bioremediation techniques (phytoremediation, rhizoremediation, genetically modified organisms, other methods) for removal of PAHs from the environment. All the removal techniques are discussed in detail along with mechanistic understanding for the degradation of the pollutants. One section is fully dedicated to the research gaps in the available literatures along with pros and cons of the bioremediation techniques associated with PAH focusing on its field scale applications. The authors have also discussed the future perspective on the basis of scientific challenges associated with these removal techniques. The aim of this review is to provide information to readers on fruitful execution of bioremediation techniques for removal of PAHs.

Removal of Naphthalene, Fluorene and Phenanthrene by Recyclable Oil Palm Leaves’ Waste Activated Carbon Supported Nano Zerovalent Iron (N-OPLAC) Composite in Wastewater

Despite keen interest in the development of efficient materials for the removal of polycyclic aromatic hydrocarbons (PAHs) in wastewater, the application of advanced composite materials is still unexplored and needs attention. Therefore, this study focused on the synthesis of the composite of oil palm leaves’ waste activated-carbon (OPLAC) and nano zerovalent iron (NZVI) at Fe:OPLAC = 1:1 (N-OPLAC-1) and 1:2 (N-OPLAC-2). The composite with enhanced surface properties was applied for removal of three PAHs including naphthalene (NAP), fluorene (FLU) and phenanthrene (PHE) in wastewater at various pH, dosages, contact time and initial concentration in batch testing. The PAHs’ removal parameters were optimized using design expert software. The PAHs’ removal efficiency was evaluated in produced water at optimized parameters. The results showed that the N-OPLAC-2 had superior surface properties compared to N-OPLAC-1. The removal of NAP, FLU and PHE was heterogenous, favorable and involved chemisorption proved by Freundlich isotherm and pseudo-second-order kinetic models using N-OPLAC-2. The optimum parameters were as follows: pH of 3, dosage and contact time of 122 mg/L and 49 min, respectively. The application of N-OPLAC-2 in produced water was favorable for removal of NAP, FLU and PHE and showed up to 90% removal efficiency, and higher stability up to 3 cycles. It can be concluded that the NZVI-OPLAC composite was successfully synthesized in this study and the materials showed good removal efficiency for three PAHs (NAP, FLU and PHE) in wastewater.

Preparation of Magnetic Graphene Photocatalytic Nano-adsorbent for the Sustainable Removal of Polycyclic Aromatic Hydrocarbons from Aqueous Solution

Magnetic graphene oxide-SiO2-TiO2 (MGST) composite was prepared for the absorption and further photodegradation of PAHs to reduce the risk of PAHs in the water environment. Magnetic graphene oxide (MGO) was obtained by introducing Fe3O4 to graphite oxide (GO). Furthermore, the suitable SiO2 layer was wrapped on the MGO for further modification with TiO2. Finally, the functional MGST composite with uniform morphology was obtained. Naphthalene, phenanthrene and pyrene were selected as models. It was found that the adsorption capacity of MGST showed the order of naphthalene (NAP) < phenanthrene (PHE) < pyrene (PYR).

Review of Techniques for the Removal of Polycyclic Aromatic Hydrocarbons from Produced Water

Polycyclic aromatic hydrocarbons (PAHs), due to their mutagenic, carcinogenic, and teratogenic potential, can lead to numerous chronic and fatal diseases. PAHs have been found in several wastewater streams, including “produced water,” which is wastewater generated during the extraction of oil and gas. The PAHs’ removal from produced water using physical, chemical, biological, and combined methods is crucial. Water is a vital ecosystem component and is extremely vulnerable to PAHs. This article reviews the current PAH situation, including their physical and chemical properties, types, characteristics, and removal methods from produced water. The mechanism of each method of removal of PAHs has been discussed. The current study results show that adsorption by nanoparticles and integrated methods are promising methods to meet the strict authoritarian limit with advanced increase potential in the direction of commercialization for the removal of PAHs and provide opportunities to use produced water as a source of water. The current study results can help the policy/decision makers in the efficient management of water resources.

Enhanced remediation of phenanthrene in water and soil by novel biochar-immobilized bacterial microspheres

Bioaugmentation is often considered a promising technology for the removal of polycyclic aromatic hydrocarbons; however, available high-efficiency microbial agents remain very limited. In this study, the green solvent polyethylene glycol 200 and Fe (NO3)3·9H2O were introduced to prepare iron-modified biochar materials by one-step pyrolysis. This material had a specific surface area of 407 m2⋅g−1 and high microbial immobilization efficiency. The addition of polyethylene glycol 200 promoted hydrolysis of iron ions, improved the surface structure and roughness of the biochar material, and promoted attachment of microorganisms on its surface. Using a polyvinyl alcohol–sodium alginate–iron-modified biochar composite, Pseudomonas aeruginosa bacteria were fixed by boric acid–CaCl2 cross-linking to remove phenanthrene from aqueous solution and soil. The results showed that the iron-modified biochar microorganism spheres could completely degrade 20 mg·L−1 of phenanthrene in solution within 12 h; degradation efficiency of 80 mg·L−1 phenanthrene was 50%. In the soil system, the modified biochar spheres had higher degradation performance compared with P. aeruginosa alone, reaching a removal efficiency of 30% in 6 d. This study provides a strategy for the effective treatment of organic pollutants in harsh environments by coupling the efficient adsorption of green materials with the biodegradability of microorganisms.

Remediation of PAH-contaminated soil using a combined process of soil washing and adsorption by nano iron oxide/granular activated carbon composite

This study investigated the application of magnetic granular activated carbon (MGAC) in soil washing process for the removal of polycyclic aromatic hydrocarbons (PAHs) from real contaminated soil. The magnetic composite was prepared using a facile-modified co-precipitation method. The presence of the synthesized magnetite (Fe3O4) nanoparticles on the composite surface was confirmed by the SEM and XRD characterization tests. The surface area and total pore volume of MGAC were determined to be 837.9 m2/g and 0.5 cm3/g, respectively, which were approximately 10% smaller than those for the bare GAC. The Langmuir model fitted the adsorption isotherm data the best; therefore, monolayer adsorption was predominant in the treatment process with MGAC. The maximum PAH adsorption capacity of MGAC was obtained at 153.5 µg/mg for the total PAHs, which was nearly 20% lower than that of bare GAC (190.3 µg/mg). The soil washing parameters were optimized, and the results demonstrated that the total PAH removal reached a maximum of 47.4% at an MGAC dose of 2% (w/w), washing time of 24 h, a liquid-to-soil ratio of 15:1, stirring speed of 100 rpm, pH of 8.3, and a temperature of 25 °C. For low molecular weight (LMW) PAHs, the removal from soil ranged from 34.6% to 57.7%, whereas the removal percentage of high molecular weight (HMW) PAHs was determined to be between 27.9 and 67.1 %. This indicated that the optimized soil washing with MGAC had a better efficiency for some HMW PAHs than the LMW PAHs. According to the thermodynamic studies, the adsorption of PAHs onto MGAC in the soil washing process was non-spontaneous (ΔG° > 0) and endothermic (ΔH° > 0) with increased randomness at the solid/solution interface of MGAC as temperature increases. The obtained results confirmed the efficiency of the magnetized activated carbon as adsorbent in soil washing to remove the hazardous PAH compounds from soil.

Effects of bioaugmentation by isolated Achromobacter xylosoxidans BP1 on PAHs degradation and microbial community in contaminated soil

Polycyclic aromatic hydrocarbons (PAHs) are a group of organic pollutants ubiquitous and persistent in soil. In order to provide a viable solution for bioremediation of PAHs-contaminated soil, a strain of Achromobacter xylosoxidans BP1 with superior PAHs degradation ability was isolated from contaminated soil at a coal chemical site in northern China. The degradation of phenanthrene (PHE) and benzo[a]pyrene (BaP) by strain BP1 was investigated in three different liquid phase cultures, and the removal rates of PHE and BaP by strain BP1 were 98.47% and 29.86% after 7 days under the conditions of PHE and BaP as the only carbon source, respectively. In the medium with the coexistence of PHE and BaP, the removal rates of BP1 were 89.44% and 9.42% after 7 days, respectively. Then, strain BP1 was investigated for its feasibility in remediating PAH-contaminated soil. Among the four PAHs-contaminated soils treated differently, the treatment inoculated with BP1 exhibited higher removal rates of PHE and BaP (p < 0.05), especially the CS-BP1 treatment (inoculation of BP1 into unsterilized PAHs-contaminated soil) showed 67.72%, 13.48% removal of PHE and BaP, respectively, over 49 days of incubation. Bioaugmentation also significantly increased the activity of dehydrogenase and catalase in the soil (p＜0.05). Furthermore, the effect of bioaugmentation on the removal of PAHs was investigated by measuring the activity of dehydrogenase (DH) and catalase (CAT) during incubation. Among them, the DH and CAT activities of CS-BP1 and SCS-BP1 (inoculation of BP1 into sterilized PAHs-contaminated soil) treatments inoculated with strain BP1 were significantly higher than those of treatments without BP1 addition during incubation (p < 0.01). The structure of the microbial community varied among treatments, but the Proteobacteria phylum showed the highest relative abundance in all treatments of the bioremediation process, and most of the bacteria with higher relative abundance at the genus level also belonged to the Proteobacteria phylum. Prediction of microbial functions in soil by FAPROTAX analysis showed that bioaugmentation enhanced microbial functions associated with the degradation of PAHs. These results demonstrate the effectiveness of Achromobacter xylosoxidans BP1 as a PAH-contaminated soil degrader for the risk control of PAHs contamination.

Buried and surface oil degradation – Evaluating bioremediation to increase PAHs removal through linear mathematical models

A bioremediation approach with tide simulation for buried and surface oil degradation was tested for removal of two, three and four rings polycyclic aromatic hydrocarbons (PAHs). Linear models depicted degradation constants of individual PAH as simple additive function of their initial concentrations (C0) in contaminated sand, hydrophobicity, sampling layer and treatment conditions. For all PAHs and treatment conditions, the degradation of oil in buried layers was faster than at the surface. Naturally-occurring microorganisms proved to be efficient for bioremediation of PAHs and were stimulated by fertilizer addition (biostimulation, BS). Bioaugmentation (BA) by addition of a slurry of a native oil-degraders pre-stimulated consortium did not show faster PAH degradation than BS. Degradation was more rapid for PAH present at low C0 and with intermediate hydrophobicity. Bioremediation of beach sand either with surface or buried crude oil is a cost-effective strategy to clean-up different hydrocarbon families, including persistent ones, such as PAHs.

Coupling of Anammox Activity and PAH Biodegradation: Current Insights and Future Directions

Anaerobic ammonium oxidation (anammox) has shown success in past years for the treatment of municipal and industrial wastewater containing inorganic nutrients (i.e., nitrogen). However, the increase in polycyclic aromatic hydrocarbon (PAH)-contaminated matrices calls for new strategies for efficient and environmentally sustainable remediation. Therefore, the present review examined the literature on the connection between the anammox process and PAHs using VOSviewer to shed light on the mechanisms involved during PAH biodegradation and the key factors affecting anammox bacteria. The scientific literature thoroughly discussed here shows that PAHs can be involved in nitrogen removal by acting as electron donors, and their presence does not adversely affect the anammox bacteria. Anammox activity can be improved by regulating the operating parameters (e.g., organic load, dissolved oxygen, carbon-to-nitrogen ratio) and external supplementation (i.e., calcium nitrate) that promote changes in the microbial community (e.g., Candidatus Jettenia), favoring PAH degradation. The onset of a synergistic dissimilatory nitrate reduction to ammonium and partial denitrification can be beneficial for PAH and nitrogen removal.

Electrochemistry-enhanced peroxymonosulfate activation by CoAl-LDH@biochar for simultaneous treatment of heavy metals and PAHs

An EC/CoAl-LDH@biochar/PMS system is proposed in this study for activation of PMS and removal of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs). In this system, over 90% of HMs and PAHs could be effectively removed after 40 min. Compared to other systems, the synergy between CoAl-LDH@biocahr and electrochemistry (EC)-peroxymonosulfate (PMS) had an excellent ability to eliminate the combined pollutants. The precise effect of the experimental parameters, including pH, CoAl-LDH@biochar dose, current density, and PMS concentration, on HMs-PAHs removal was determined, and the system was found to have a broad working pH range. The presence of EC can overcome the inhibition of anions in the degradation of PAHs due to the direct oxidation of PMS and PAHs on the cathode. The scavenging tests confirmed that the free radical and non-radical processes contributed to the degradation of PAHs. It is also revealed that EC can promote the continuous circulation of transition metals, which enhances the activation of PMS. The adsorption on the surface of CoAl-LDH@biochar and electrochemical deposition were the two main mechanisms for HMs removal. Furthermore, the electrode and CoAl-LDH@biochar possessed favorable recyclability in five consecutive cycles. This study has provided a promising and cost-effective approach for treatment of HM-PAH co-contaminated wastewater.

Effects of deodorization on the content of polycyclic aromatic hydrocarbons (PAHs), 3-monochloropropane-1,2-diol esters (3-MCPDE) and glycidyl esters (GE) in rapeseed oil using ethanol steam distillation at low temperature

High temperature is beneficial for the removal of polycyclic aromatic hydrocarbons (PAHs) from oil via steam, but leads to an increase in the content of 3-monochloropropane-1,2-diol esters (3-MCPDE) and glycidyl esters (GE). To inhibit the production of 3-MCPDE and GE during the removal of PAHs, rapeseed oil was deodorized using ethanol steam at low-temperature (140–220 °C) (L-ESD) and the content changes were studied for PAHs, 3-MCPDE and GE, and compared with conventional high-temperature water steam deodorization (H-WSD) (250 °C for 60 min). The removal rates of PAHs in L-ESD oil can be higher than those in conventional H-WSD oil, and the contents of 3-MCPDE and GE in L-ESD oil (140–180 °C for 60–100 min) ranged from 48.32 to 73.65 % and 50.49–69.90 %, respectively, in H-WSD oil due to the lower temperature of ethanol steam deodorization. These results indicate that L-ESD is beneficial in minimizing the contents of PAHs, 3-MCPDE and GE in vegetable oil.

Simultaneous removal of sediment and water contaminants in a microbial electrochemical system with embedded active electrode by in-situ utilization of electrons.

In the water environment such as lakes, there is a phenomenon that the sediment and overlying water are polluted at the same time. In this study, A microbial electrochemical system with an embedded active electrode was developed for simultaneous removal of polycyclic aromatic hydrocarbons in sediment and antibiotics in overlying water by in-situ utilization of electrons. In the closed-circuit group, the pyrene concentration in sediment decreased from 9.94 to 2.08mg/L in 96 d, and the sulfamethoxazole concentration in water decreased from 5.12 to 1.12mg/L in 168h. These values were 18.71 % and 31.21 % higher, respectively, than those of the open-circuit group. The pyrene degradation pathway may be from polycyclic aromatic substances to low-cyclic aromatic hydrocarbons via successive breakdown of benzene rings. Multiple metabolites produced by reduction verified that SMX or its intermediates were reductively degraded in water. On the active electrode, the relative abundances of Acetobacterium and Piscinibacter, which were genera related to SMX degradation, was promoted, while the electricity-producing genus Pseudomonas was inhibited. ccdA, pksS, torC, and acsE genes related to extracellular electron transport may accelerate electron transport. Electrons could be transferred to SMX under the influence of proteins involved in extracellular electron transport, and SMX could be degraded reductively as an electron acceptor by microbes. Generation of electrons and in-situ utilization for simultaneous removal of solid-liquid two-phase pollutants will provide mechanistic insight into pollutant biodegradation by microbial electrochemistry and promote the development of sustainable bioremediation strategies for surface water.

Enhanced benzofluoranthrene removal in constructed wetlands with iron- modified biochar: Mediated by dissolved organic matter and microbial response.

Polycyclic aromatic hydrocarbons (PAHs) pose a high risk to ecosystems owing to their adverse environmental effects. The use of biochar in constructed wetlands (CWs) to remove PAH has received increased interest, but is frequently challenging because of saturation adsorption. To enhance the microbial degradation, electron acceptors are provided. This study aimed to remove a representative PAH, benzofluoranthrene (BbF), using iron-modified biochar as a supplement to the CW substrate. Results revealed that iron-mediated biochar based CWs increased the removal of BbF by 20.4 % and ammonium by 25.6 %. The BbF retained in substrate with biochar (36.6 % higher content) and further removed with iron modification (40.6 % lower content). Iron-modified biochar increased dissolved organic carbon content, particularly low-aromaticity, and low-molecular-weight organic matters (25.7 % higher tryptophan-like material), which contributed to PAH degradation by microorganisms. Microbial analysis confirmed that iron-mediated biochar enriched the abundance of microbes (e.g., Cellulomonas, Actinotalea, and Sphingomonas) and key enzymes (e.g., catA, lipV, and sdhA) that are involved in PAH degradation. Higher proportion of iron-reducing bacteria (e. g., Thiobacillus, Rhodobacter) played a significant role in driving microbial iron cycle, which was beneficial for PAHs removal. Based on the results, we confirmed that the use of iron-modified biochar in CWs enhance PAH removal.

Water hyacinth derived biochar for polycyclic aromatic hydrocarbons removal and oxidative stress study

Polycyclic aromatic hydrocarbons (PAHs), highly concerned emerging contaminant, are priority persistent organic pollutants (POPs) adversely affect the ecological health of marine sediments. These pollutants have attracted widespread attention because of their potential toxicological effects on aquatic organisms and subsequent threats to human health. In this study, an advanced oxidation process for the remediation of PAH-contaminated sediments was developed by the activation of calcium peroxide (CaO2; CP) using a green catalyst prepared from water hyacinth biochar (WHBC), and the associated biochar-driven cellular oxidative stress was highlighted. The catalytic capacity of WHBC was determined at pyrolysis temperature between 300 and 900 °C. WHBC prepared 700 °C (WHBC700) and CP removed 74% of PAHs from the sediment matrix. Results of antioxidant activity evaluation after exposure to WHBC at doses between 400–4000 and 1000–4000 mg L−1 in human hepatocarcinoma cell lines (HepG2) for 24 h showed enhanced glutathione peroxidase (GPx) and catalase (CAT) activities, respectively. Increase in mRNA levels of superoxide dismutase (SOD) genes was also observed after WHBC exposure (400–4000 mg L−1), implying that the oxidative damage caused by reactive oxygen species (ROS) was inhibited by elevating the cellular antioxidant activity. This study attempted to demonstrate an effective waste-to-resource strategy for remediating PAH-polluted sediment in addition to understanding the potential environmental effects of antioxidant activity and gene expression of carbon-based catalysts on HepG2.

Surfactant-Containing Foam Effectively Enhanced the Removal of Polycyclic Aromatic Hydrocarbons from Heavily Contaminated Soil.

Surfactant remediation has an excellent record of removing polycyclic aromatic hydrocarbons (PAHs). By using simulation experiments, we investigated the properties and mechanism of a surfactant-containing foam and its effect on PAH removal. Our results suggest that the optimal conditions by foam washing are as follows: 40 mmol·L-1 of rhamnolipid and fulvic acid mixed surfactant (V: V = 3:1), with 70:3 and 20:3 foam gas-liquid ratio for naphthalene and phenanthrene, respectively (pH 6, 50°C, 2 h). Under the optimal conditions, 60.1% and 56.68% removal efficiencies were achieved against naphthalene and phenanthrene from contaminated soil, respectively. These values were lower than those from the simulated media (76.69% and 70.43% for naphthalene and phenanthrene, respectively). The strong PAH adsorption on the soil particles antagonized volatilization, the key PAH removal mechanism by foam leaching. Therefore, this research provides relevant information for using surfactant foam to remediate heavily PAH-contaminated soils.