Hydrophobic Polycyclic Aromatic Hydrocarbons Research Articles

Fluorescent Probes for the Supramolecular Interactions responsible for Binding of Polycyclic Aromatic Hydrocarbons to Hyperbranched Polyelectrolytes in Aqueous Media

AbstractCationic poly(amidoamine) (PAMAM) dendrimers are known as good supramolecular hosts for a variety of smaller water‐soluble guests. We expanded their binding scope to the uptake of very hydrophobic guests such as polycyclic aromatic hydrocarbons (PAH) in neutral aqueous solution. We used anthracene and pyrene as representatives of this family of hydrocarbons, and as capable fluorescent emitters to probe mode and location of interaction for these hydrocarbons with polycationic amine‐terminated PAMAM dendrimers. We used steady‐state and time‐resolved fluorescence emission spectroscopy, as well as fluorescence anisotropy measurements and selective quenching experiments, to establish the mode and location of these binding interactions, demonstrating that, although these probes may look relatively similar, their interaction with PAMAM dendrimers is nevertheless significantly different. The results presented here provide insight into the attractive forces at play in the uptake of featureless hydrophobic PAH guests by hydrophilic PAMAM dendrimer hosts, whose applications span practical challenges including chemical separations, analytical discrimination, solubility and bioavailability enhancement of hydrophobic compounds.

Effects of supergene geochemical processes on desorption and bioavailability of polycyclic aromatic hydrocarbons in soil of karst area

ABSTRACT Supergene geochemical processes (SGPs) occur ubiquitously in the Earth´s surface, but their effects on the fate and bioavailability of polycyclic aromatic hydrocarbons (PAHs) in soil remain unclear. Study selected phenanthrene and pyrene as representative PAHs and yellow soil (YS) and limestone soil (LS) of karst area in southwest China, to investigate the effects of SGPs on the desorption and bioavailability of PAHs. Two soils were subjected to repeated freeze-thawing and long-term storage for SGPs. The hysteresis index values of pollutants increased with increase cycles of freeze-thawing and storage time. Under the SGPs, the phenanthrene fast desorption fraction of YS and LS decreased by 22.01% and 24.79%, respectively, and that of pyrene were by 23.81% and 28.12%, respectively. The desorption fraction of 24 hours was a better proxy of the fraction of bioavailability than that of 6 hours. The desorption rate of PAHs was negatively correlated with the hydrophobicity of PAHs.

Mesoporous silica hybridized by ordered mesoporous carbon for in‐tube solid‐phase microextraction

To enhance the extraction performance, a mesoporous silica was modified with ordered mesoporous carbon for solid-phase microextraction. Three stainless-steel wires coated with the mesoporous material were placed in a polyetheretherketone tube for getting an extraction tube. The tube was coupled to high-performance liquid chromatography with diode array detector, and the online analysis system was constructed. Then its extraction performance was evaluated using hydrophobic polycyclic aromatic hydrocarbons, phthalates, and hydrophilic neonicotinoids. The best selectivity was presented for polycyclic aromatic hydrocarbons. Several main conditions were optimized such as sampling volume, sampling rate, methanol concentration in the sample, and desorption time, a rapid and sensitive analytical method was established toward polycyclic aromatic hydrocarbons. The analytical method exhibited wide linear range from 0.017 to 15 µg/L with acceptable correlation coefficients more than 0.9990, limits of detection in 0.005-0.020 µg/L, limits of quantification ranging from 0.017 to 0.066 µg/L as well as large enrichment factors of 377-2314. It was successfully applied to detect trace polycyclic aromatic hydrocarbons in some real water samples including tap water, snow water, and domestic sewage.

Removal of polycyclic aromatic hydrocarbons from aqueous media using modified clinoptilolite

Carcinogenic polycyclic aromatic hydrocarbons (PAHs) are widespread in the environment. In this study, the removal of PAHs from aqueous media was assessed using samples of clinoptilolite, a natural zeolite, pre-treated with 1 mol/L of NaCl, (Na pre-treated clinoptilolite, NC). Samples (10 g) of NC were separately modified with 5, 2, 2, and 20-mmol/L solutions of cetylpyridinium chloride (CPC), didodecyldimethyl ammonium bromide (DDAB), hexadecyltrimethylammonium bromide (HDTMA), and tetramethyl ammonium chloride (TMA) surfactants as potential cost-effective adsorbents. The kinetics, optimal sorbent dosage, and competitive effects were evaluated through batch adsorption tests using deionised water spiked with five PAHs (anthracene (50 μg/L), fluoranthene (100 μg/L), fluorene (100 μg/L), phenanthrene (100 μg/L), and pyrene (100 μg/L)). The surfactant non-modified (NC) and TMA-MC (modified clinoptilolite) exhibited PAH removal of <66% from the spiked concentration in aqueous solution, while CPC-MC, DDAB-MC, and HDTMA-MC achieved removal rates of >93% for the five PAHs after 24 h at a solid:liquid ratio of 1:100. The remaining concentrations of anthracene and fluoranthene were below 3 μg/L, and that of fluorene was <6 μg/L, lower than the water quality criteria of British Columbia, Canada, for protecting aquatic life. However, HDTMA-MC retained >83% of the fluorene. Over 80% of all PAHs were absorbed within 15 min for the CPC-MC and DDAB-MC, and the maximum adsorption was reached in <2 h. Three kinetic models were applied assuming pseudo-first-order, pseudo-second-order, and intra-particle equations, and the results were well-represented by the pseudo-second-order equation. The PAH sorption results indicated that the adsorption mechanism is based on PAH hydrophobicity, and π-π electron-donor-acceptor interaction with surfactant. CPC and DDAB with two long chain hydrocarbons had more PAH adsorption than HDTMA with one, and TMA with no long chain hydrocarbons (DDAB-MC > CPC-MC > HDTMA-MC ≫ TMA-MC > NC). With a solid:liquid ratio of 1:200, over 90%, 80%, and 70% of the anthracene, fluoranthene, and pyrene were adsorbed by the CPC-MC, DDAB-MC, and HDTMA-MC, respectively.

Detection of polycyclic aromatic hydrocarbons by surface enhanced Raman scattering on colloidal silver substrates

The present work reports on the possibility of polycyclic aromatic hydrocarbons (PAHs) detection by surface enhanced Raman scattering (SERS) on substrates coated with colloidal silver stabilized with cetyltrimethylammonium bromide (CTAB). It was shown that cetyltrimethylammonium bromide acts not only as a stabilizer of metal nanoparticles, but also as modifying agent that promotes the concentration of hydrophobic PAH molecules near the amplified electromagnetic field of plasmon silver nanoparticles. Anthracene and pyrene were used as model analytes. To determine the sensitivity of the prepared SERS active coating, ethanol solutions of the analyzed substances with concentrations in the range of 2·10-4 — 10-6 mol/L were used. The lowest concentrations of solutions for which anthracene and pyrene are found on the tested substrates were equal to 2.5·10-6 M and 5·10-5 M, respectively. These results indicate that substrates are more sensitive to anthracene than to pyrene. The work also shows that various PAH molecules can be detected by characteristic peaks in a complex mixture without preliminary separation of the components.

Melting scenario affects the dynamics of polycyclic aromatic hydrocarbons released from snowpack

Melting snowpack can release semi-volatile organic contaminants (SVOCs) to both terrestrial and aquatic ecosystems, resulting in high ecological risk. The dynamics of polycyclic aromatic hydrocarbon (PAH) released from snowpack under controlled laboratory (intense melting) and field (melt/freeze melyting) snowmelt experiments was investigated in this study. In the laboratory: dissolved organic carbon (DOC) controlled the first flush of dissolved PAHs released from snowpack, except for napthelene, which is also affected by its solubility. The particles released early from snowpack usually contained high PAH concentrations (more than 100 μg g−1) and those released at the end contained low PAH concentrations (<20 μg g−1). The total PAH release pattern was determined by composition of all PAHs, including type 2 enrichment with a final peak and type 4 enrichment with double-peak. In field melting: all dissolved PAHs were released constantly, except naphthalene, which also showed a first flush but to a lesser extent. DOC controlled the release pattern of all detected dissolved PAHs from snowpack. High PAH concentrations were observed in particles released from snowpack at both the beginning and the end of the melting event. Concentrations of both total PAHs and PAH compositions in meltwater showed an increasing trend with melting time (from 1.3 to 4.0 μg l−1 and from 1.7 to 5.3 μg l−1 in meltwater from each of the two snowpacks), which coincided with Type 3 enrichment. Overall, our results suggest intense melting of snowpack results in the shift of some hydrophobic PAH compositions from Type 2 to Type 4 enrichment, depending on their partition coefficients. In contrast, melting with melt/freeze cycles may cause the shift of PAHs from Type 2 to Type 3 enrichment. Our study indicates changes of the melting scenarios due to global warming could affect dynamics of SVOCs released from snowpack, which is useful for risk management for water and soil quality.

Iron Plaque Prevents Partitioning of Polycyclic Aromatic Hydrocarbons on Rice (Oryza sativa) Root Surface.

Adsorption of polycyclic aromatic hydrocarbons (PAHs) on root surfaces has essential impacts on PAH phytoremediation. An Fe plaque is commonly formed on the root surface of aquatic plants. Therefore, it is worth investigating the impact of the Fe plaque on PAH adsorption on rice root surfaces. Using Bayesian linear water-methanol cosolvent models, we estimated accurate water-biosorbent partition coefficient values for phenanthrene, pyrene, and benzo[a]pyrene between water and rice root biosorbent fractions, including rice root materials with Fe plaque, removed Fe plaque, and removed Fe plaque and lipids. Our results showed that Fe plaque inhibited the adsorption of PAHs on rice root surface; the inhibition impacts increased with hydrophobicity of PAHs. This result highlights the need for considering the impact of Fe plaque on PAH adsorption during phytoremediation. Integr Environ Assess Manag 2020;16:392-399. © 2020 SETAC.

Joint effect of nanoplastics and humic acid on the uptake of PAHs for Daphnia magna: A model study

Nanoplastics (NPs) are emerging pollutants which can adsorb large amounts of hydrophobic organic compounds (HOCs) and be ingested by aquatic organisms. NPs interact with dissolved organic matter (DOM) and result in significant impacts on the bioaccumulation of HOCs in the actual environment. For the first time, the joint effects of two complex matrices on the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) to Daphnia magna (D. magna) were studied by modeling calculation. The complex matrices, nano-sized polystyrene (PS) and/or humic acid (HA), were under environmentally realistic concentrations. A biodynamic model was modified and the uptake fluxes from all exposure pathways were quantified using the experimental data. A flux estimation showed that the bioaccumulation amounts at equilibrium were mostly dependent on dermal uptake (≥99.3 % of the total). The PS matrix would retard the intestinal uptake process in D. magna, especially for the less hydrophobic PAHs; while the HA or the HA-PS matrix would facilitate the mass transfer of PAHs from the matrix to lipids in the gut. Moreover, the biota matrix accumulation factor (BMAF) were calculated to verify the biodynamic model. This work is helpful to clarify the bioaccumulation effects of PAHs in complex environmental systems.

Carbonized silk fibers for in-tube solid-phase microextraction to detect polycyclic aromatic hydrocarbons in water samples.

Silk fibers were carbonized to develop a biomass carbon material as an adsorbent for solid-phase microextraction. The surface structure of the carbonized silk fibers was characterized by scanning electron microscopy, and the graphitization degree was determined by Raman spectrometry. After carbonization under high temperature, the orderliness and structural regularity of carbon atoms on silk fibers were promoted. Extraction tube packed with carbonized silk fibers was prepared for in-tube solid-phase microextraction. Coupled with high performance liquid chromatography, it exhibited good extraction performance for hydrophobic polycyclic aromatic hydrocarbons. Main parameters including sampling volume, sampling rate, methanol content in sample, and desorption time were systematically investigated. Under the optimum conditions, the analysis method was established and it exhibited wide linear range (0.016-20 μg/L) with good linearity (correlation coefficient ≥ 0.9947), low limits of detection (0.005-0.050 μg/L), and high enrichment factors (1189-2775). Relative standard deviations (n=3) for intraday (≤3.3%) and interday (≤9.6%) tests indicated that the extraction material had satisfactory repeatability. Finally, the analytical method was successfully applied to detect trace polycyclic aromatic hydrocarbons in real water samples, demonstrating its satisfactory practicability.

Polystyrene-Supported Core-Shell Beads with Aluminium MOF Coating for Extraction of Organic Pollutants.

Aluminium-based metal-organic framework (MOF) coatings on polystyrene bead surfaces were easily synthesized by reacting an intermediate metal hydroxide coating with an organic linker. Several different sizes of polystyrene beads were coated with aluminium metal hydroxide to construct Al@PS core-shell bead materials. The activated Al@PS core-shell beads were involved to make a homogenous MOF-based layer in the presence of the organic linker. By using different sizes of the PS support the size of MOFs on the PS composites could be fine-tuned under specific reaction conditions. MOF-coated core-shell bead materials (Al-1,4-NDC@PS and MIL-53(Al)@PS) were characterized using various analytical techniques. Al-1,4-NDC@PS and MIL-53(Al)@PS were evaluated for solid-phase microextraction (SPME) of hydrophobic polycyclic aromatic hydrocarbons (PAHs) and hydrophilic non-steroidal anti-inflammatory drugs (NSAIDs), respectively. Al-1,4-NDC@PS-1000 displayed high extraction recoveries ranging from 79.2 % to 99.8 % in the SPME of PAHs. Meanwhile, MIL-53(Al)@PS-1000 showed 85.9-99.0 % extraction recoveries in the SPME of NSAIDs. These results show that the proposed approach holds potential to extract organic analytes on an industrial scale.

Ozone-encapsulated colloidal gas aphrons for in situ and targeting remediation of phenanthrene-contaminated sediment-aquifer

The hydrophobic polycyclic aromatic hydrocarbons (PAHs) are apt to adhere tightly to the sediments in aquifer and thus pose great threats to the aquatic environment of groundwater and surface water as well as human health. The present study constructed functionalized microbubbles, named colloidal ozone aphrons (COAs), by dissolving ozone-contained air into the nonionic surfactant (Tween-20) solution at the pressure of 300 kPa for the in situ remediation of phenanthrene (PHE)-contaminated sediments. The COA system aimed at improving the PHE elimination in terms of (i) enhancing the migration and transportation ability of the bubble system in the contaminated aquifer matrix, (ii) accurately desorbing the target hydrophobic contaminants from sediments, and (iii) reinforcing the in situ oxidation degradation immediately after or simultaneously when the PAHs are desorbed into the aqueous phase. Experimental results demonstrated that the COAs exhibited similar characteristics as the classical colloidal gas aphrons (CGAs), including the high stability (half-life time > 200 s), typical morphology and average bubble size (114–162 μm); higher air hold-up of COAs was achieved (i. e. > 20%) compared with the air-microbubbles (1–2%) obtained under the same generation conditions. Although the encapsulated ozone could oxidize the surfactant-layers, the properties and behaviors of COAs were not greatly affected. The surfactant multi-layers endowed the COAs with strong hydrophobic attraction with PHE, great migration capacity and enlarged oxidation area in the sediment matrix. Approximately 96.9% of PHE was removed from the sediments and 84.9% of the overall PHE was oxidized at the high ozone concentration of 0.6 mg/L when the initial PHE concentration was 240.0 μg/kg. The COA-involved remediation technology provided the insight of combining the processes of washing and oxidizing through adopting the particularly conceived microbubbles. The in situ and selective removal of hydrophobic organic contaminants from sediments in aquifer was well achieved in this study.

Interaction of pulmonary surfactant with silica and polycyclic aromatic hydrocarbons: Implications for respiratory health

Understanding the interaction between pulmonary surfactant (PS) and inhalable pollutants is vital for risk assessment of respiratory health. Here, PS extracted from porcine lung (EPS) was used to investigate the interaction of PS with nano-silica particles and polycyclic aromatic hydrocarbons (PAHs). Our results demonstrated that silica significantly affected the phase behavior and foaming ability of EPS; EPS and its major components (dipalmitoyl phosphatidylcholine, DPPC; bovine serum albumin, BSA) exhibited great enhancing effect on PAHs solubility, which follows the order: EPS > DPPC > BSA, and it was positively correlated with the hydrophobicity of PAHs. Further experiments demonstrated that mixed phospholipids of EPS were largely responsible for the solubilization of EPS on PAHs. In the presence of EPS, DPPC or BSA, adsorption of PAHs by silica was notably inhibited, indicating competitive adsorption between PAHs and PS components on silica. These findings provide evidence for the surface chemistry by which PS facilitates the solubilization of PAHs and reducing the adsorption of PAHs on silica, which may be helpful for deeply understanding the effects of particulate matter and PAHs on lung health.

The accumulation of metals, PAHs and alkyl PAHs in the roots of Echinacea purpurea.

We examined the accumulation of polycyclic aromatic hydrocarbons (PAHs), alkyl PAHs, and toxic metals in soils by the roots of Echinacea purpurea (L.) Moench, in a 20-week greenhouse study and a 2-year field study. In the greenhouse study, inoculation by arbuscular mycorrhizal fungus (AMF), Rhizoglomus intraradices (N.C. Schenck & G.S. Sm.). increased the first order accumulation rates (k1) for PAHs by 10-fold, though had no effect on the bioaccumulation rates of toxic metals. In the greenhouse study, PAHs concentrations in soil increased over time with AMF inoculation, suggesting AMF promote ‘solvent depletion’ in soils by enhancing absorption of minerals and carbon by roots, concentrating the more hydrophobic PAHs in the residual soil. Under field conditions, contaminant concentrations in soils remained unchanged over the 2-year duration of the study. Despite this, all contaminants in E. purpurea roots increased significantly, as a result of a long term extraction of contaminants by plants from soil and a reduction in soil volume as a result of plant growth. First order accumulation rates by roots were inversely correlated to log Kow for the PAHs and alkyl PAHs, indicating that accumulation is inversely related to the compound’s hydrophobicity. This study is the first to our knowledge to assess the accumulation of alkyl PAHs by roots, with implications for soil bioremediation by plants because alkyl PAHs are a major source of petrogenic contamination in soils.

Linking the contents of hydrophobic PAHs with the canopy water storage capacity of coniferous trees

The canopy water storage capacity (S) is an important parameter for the hydrological cycle in forests. One factor which influences the S is leaf texture, which in turn is thought to be affected by the contents of polycyclic aromatic hydrocarbons (PAHs). In order to improve our understanding of S we simulated rainfall and measured the S of coniferous species growing under various conditions. The contents of 18 PAHs were measured in the needles. The species chosen were: Scots pine (Pinus sylvestris L), Norway spruce (Picea abies (L.) H. Karst) and silver fir (Abies Alba Mill.). Sample branches were collected in 3 locations: A - forest; B - housing estate; C - city center. We found that PAHs have a significant impact on the S of tree crowns. The increase in the total content of all of polycyclic aromatic hydrocarbons (SUM.PAH) translates into an increase of S for all species. The S is the highest for the P. abies species, followed by P. sylvestris and A. alba at all locations. Within the same species, an increase in the value of S is associated with an increase in the PAH content in needles measured by gas chromatography. For A.alba, the average S increased from 11.54% of the total amount of simulated rain (ml g−1) at location A, to 17.10% at location B, and 21.02% at location C. Similarly for P. abies the S was 21.78%, 29.06% and 34.36% at locations A, B and C respectively.The study extends the knowledge of the mechanisms of plant surface adhesion and the anthropogenic factors that may modify this process as well as foliage properties.

Application of Klebsiella oxytoca Biomass in the Biosorptive Treatment of PAH-Bearing Wastewater: Effect of PAH Hydrophobicity and Implications for Prediction

Biosorption has been widely recognized as a promising method to treat wastewater. However, few studies have investigated the impact of pollutants’ properties on wastewater treatment, as well as the underlying mechanisms and future predictions. In this study, the effects of pollutants’ hydrophobicity on the biosorptive removal of polycyclic aromatic hydrocarbons (PAHs) were evaluated. The results showed that the inactive biomass of Klebsiella oxytoca effectively removes PAHs from aqueous solutions with a high biosorption capacity, high biosorption affinity, and short equilibrium time. The biosorption of seven PAHs achieved equilibrium rapidly (less than 2 h) and fitted well to the pseudo-second-order kinetic model. Sorption occurred with a predominantly linear partition process to the biomaterial with Kd values of 363.11, 1719.5, 2515.5, 7343.3, 6353.4, 22,806, and 19,541 L·kg−1 for naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, pyrene, and fluoranthene, respectively. An increase in temperature led to a decrease in the biosorption affinity, and the bacterial biosorption of PAHs was spontaneous and exothermic. Furthermore, a positive correlation was observed between the sorption affinity and the octanol partition coefficient (Kow) (logKd = 1.011logKow − 0.7369), indicating that hydrophobicity is the main factor influencing the biosorption efficiency. These results suggest that biosorption is an efficient and predictable treatment for micropollutant-bearing wastewater.

Determination of the partition coefficient between dissolved organic carbon and seawater using differential equilibrium kinetics

Because the freely dissolved fraction of highly hydrophobic organic chemicals is bioavailable, knowing the partition coefficient between dissolved organic carbon and water (KDOCw) is crucial to estimate the freely dissolved fraction from the total concentration. A kinetic method was developed to obtain KDOCw that required a shorter experimental time than equilibrium methods. The equilibrium partition coefficients of four polychlorinated biphenyls (PCBs) (2,4,4′-trichlorobiphenyl (PCB 28), 2,2′,3,5′-tetrachlorobiphenyl (PCB 44), 2,2′,4,5,5′-pentachlorobiphenyl (PCB 101), and 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153)) between dissolved organic carbon and seawater (KDOCsw) were determined using seawater samples from the Korean coast. The log KDOCsw values of PCB 28 were measured by equilibrating PCB 28, the least hydrophobic congener, with seawater samples, and the values ranged from 6.60 to 7.20. For the more hydrophobic PCBs (PCB 44, PCB 101, and PCB 153), kinetic experiments were conducted to determine the sorption rate constants (k2) and their log KDOCsw values were obtained by comparing their k2 with that of PCB 28. The calculated log KDOCsw values were 6.57–7.35 for PCB 44, 6.23–7.44 for PCB 101, and 6.35–7.73 for PCB 153. The validity of the proposed method was further confirmed using three less hydrophobic polycyclic aromatic hydrocarbons. This kinetic method shortened the experimental time to obtain the KDOCsw values of the more hydrophobic PCBs, which did not reach phase equilibrium.

Polycyclic Aromatic Hydrocarbons Adsorption onto Graphene: A DFT and AIMD Study.

Density functional theory (DFT) calculations and ab-initio molecular dynamics (AIMD) simulations were performed to understand graphene and its interaction with polycyclic aromatic hydrocarbons (PAHs) molecules. The adsorption energy was predicted to increase with the number of aromatic rings in the adsorbates, and linearly correlate with the hydrophobicity of PAHs. Additionally, the analysis of the electronic properties showed that PAHs behave as mild n-dopants and introduce electrons into graphene; but do not remarkably modify the band gap of graphene, indicating that the interaction between PAHs and graphene is physisorption. We have also discovered highly sensitive strain dependence on the adsorption strength of PAHs onto graphene surface. The AIMD simulation indicated that a sensitive and fast adsorption process of PAHs can be achieved by choosing graphene as the adsorbent. These findings are anticipated to shed light on the future development of graphene-based materials with potential applications in the capture and removal of persistent aromatic pollutants.

Metal-Organic Framework-Derived Hollow Carbon Nanocubes for Fast Solid-Phase Microextraction of Polycyclic Aromatic Hydrocarbons.

Developing novel coating materials for fast and sensitive solid-phase microextraction (SPME) is highly desired but few are achieved. In this work, a new material of metal-organic framework (MOF)-derived hollow carbon nanocubes (HCNCs) was prepared as a fiber coating material for SPME. The HCNC-coated fiber (denoted as HCNCs-F) exhibited a better enrichment performance than solid carbon nanocube (SCNC)-coated fiber (denoted as SCNCs-F) and commercial fibers based on the abundant active sites of the hollow structure, hydrophobic interactions, and π-π interactions. Moreover, because of the reduced mass-transport lengths of the hollow mesoporous structure, the HCNCs-F demonstrated a faster mass transfer compared with the SCNCs-F. The HCNCs-F was used to determine the six hydrophobic polycyclic aromatic hydrocarbons (PAHs) with wide linear ranges (10-2000 ng L-1 for naphthalene and 5-2000 ng L-1 for the other five analytes), good reproducibility (relative standard deviation < 8.8%), and low detection limits (0.03-0.70 ng L-1). Finally, the HCNCs-F was successfully applied for the determination of PAHs from the real water samples. It can be concluded from the results that MOF-derived hollow carbon materials are promising candidates for the fast SPME and can be used for practical applications in analytical chemistry.

Enhanced dehydration performance of hybrid membranes by incorporating fillers with hydrophilic-hydrophobic regions

In this study, sulfonated pitch (SP), composed of hydrophilic sulfonate groups and hydrophobic polycyclic aromatic hydrocarbons, was incorporated into sodium alginate (SA) membranes for ethanol dehydration via pervaporation. The morphologies and structures of the SP and hybrid membranes were confirmed by transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), positron annihilation lifetime spectroscopy (PALS) and water contact angle measurement. Hydrophilic sulfonate groups in SP formed hydrophilic regions which can bind water molecules, ensuring sufficient water occupancy in the membranes, while the hydrophobic polycyclic aromatic hydrocarbons provided continuous transport “highways” for the water molecules. Meanwhile, the introduction of SP created more polymer-filler interface cavities, rendering the membrane with suitable free volume property for separation. Consequently, the membrane demonstrated a maximum permeation flux of 1879 ± 80 g/m2 h coupled with an optimal separation factor of 1913 ± 69 in separating 90 wt% ethanol aqueous solution. These resulted in an increase over the SA control membrane of 1.5-fold and 4-fold respectively. Moreover, the hybrid membranes exhibited good operation stability. The results suggested that incorporating fillers with hydrophilic-hydrophobic regions in the membranes can be an effective strategy to improve the performance of water-permselective membranes.

Mobility of PAHs, PCBs and TPHs from Fresh and Aged Dredged Sediments

The management of dredged sediments on land is an environmental concern worldwide since they may be overloaded with a wide range of pollutants. In this study, percolation tests were carried out to provide insight about the emission of selected polycyclic aromatic hydrocarbons (PAHs), Polychlorinated Biphenyls (PCBs), total petroleum hydrocarbons (TPHs) in five fresh and matured (1.5 years) dredged contaminated sediments. Although the studied sediments were heavily contaminated, less than 1% of the contaminants were emitted in column tests with an L S−1 ratio of 10 L kg−1. Emissions of hydrophobic organic compounds were facilitated (by a factor of 30 to 1000 times) by colloids. The dissolved organic matter was identified as vector for the transfer of contaminants in leachates: PAH concentrations were correlated with humic acids and hydrophobic neutral organic carbon (HON) concentrations, and PCB concentrations with HON concentrations. Maturation of the sediments (moderate drying/rewetting cycles under oxidizing conditions for 1.5 years) dramatically reduced the emissions (TPH ≥60%, less hydrophobic PAHs ≥50%, PAHs with log Kow >5.1 and PCBs = 100%, <LOQ).