Adsorption Of Pyrene Research Articles

Adsorption of Polycyclic Aromatic Hydrocarbons by Graphene and Graphene Oxide Nanosheets

The adsorption of naphthalene, phenanthrene, and pyrene onto graphene (GNS) and graphene oxide (GO) nanosheets was investigated to probe the potential adsorptive sites and molecular mechanisms. The microstructure and morphology of GNS and GO were characterized by elemental analysis, XPS, FTIR, Raman, SEM, and TEM. Graphene displayed high affinity to the polycyclic aromatic hydrocarbons (PAHs), whereas GO adsorption was significantly reduced after oxygen-containing groups were attached to GNS surfaces. An unexpected peak was found in the curve of adsorption coefficients (Kd) with the PAH equilibrium concentrations. The hydrophobic properties and molecular sizes of the PAHs affected the adsorption of G and GO. The high affinities of the PAHs to GNS are dominated by π-π interactions to the flat surface and the sieving effect of the powerful groove regions formed by wrinkles on GNS surfaces. In contrast, the adsorptive sites of GO changed to the carboxyl groups attaching to the edges of GO because the groove regions disappeared and the polar nanosheet surfaces limited the π-π interactions. The TEM and SEM images initially revealed that after loading with PAH, the conformation and aggregation of GNS and GO nanosheets dramatically changed, which explained the observations that the potential adsorption sites of GNS and GO were unusually altered during the adsorption process.

カーボンナノチューブへのピレン吸着：エナジェティクスとダイナミクス

カーボンナノチューブへのピレン吸着：エナジェティクスとダイナミクス

Synthesis and characterization of cubic mesoporous bridged polysilsesquioxane for removing organic pollutants from water

Hexane, octane, phenyl, and biphenyl-bridged bis(triethoxysilyl) precursors were used in synthesizing cubic mesoporous bridged polysilsesquioxane (BPS) copolymers. Structural characterization was carried out by FTIR, small angle XRD, Brunauer–Emmett–Teller-N2 sorption, 1H NMR, and TEM. We successfully synthesized both “rigid” and “soft” 3D cubic mesoporous BPS with high surface area and pore volume, as attested by the comprehensive characterization data. Adsorption of pyrene, phenanthrene, nitrobenzene, and 2,4-dichlorophenol on BPS was greatly affected by adsorbate properties, i.e., Kow, solvation properties and molecular size. Hydrophobic interaction dominantly controlled organic pollutants’ sorption on BPS. Other interactions, e.g., π–π and H-bond interactions, also have effects on sorption as indicated by Kow normalized sorption isotherms. Rigid aromatic BPS (phenyl and biphenyl) showed a higher sorption capacity than soft aliphatic BPS (hexane and octane). A conceptual model was proposed to further explain the phenomena. This study suggests a promising application of cubic mesoporous BPS in wastewater treatment.

Molecular dynamics simulation of adsorption of pyrene–polyethylene glycol onto graphene

The nonvalent interaction between amphiphilic polymers and graphenes is important to provide the surface functionalization of graphene. Herein, molecular dynamics simulations were carried out to investigate the interaction of pyrene–polyethylene glycol (Py–PEG) with graphene. The dynamic adsorption process and self-assembly morphology of Py–PEG onto nanoscale graphene surface have been demonstrated. The effects of the graphene size and the length of polymer chain were explored. It was shown that Py–PEG could spontaneously adsorb onto graphene surface. The Py–PEG polymer generally exhibits a coil structure with the hydrophobic pyrene surrounded by the PEG chain. However, once the Py–PEG molecule approaches the graphene surface, the PEG chain can unfold its structure on the graphene surface and the pyrene group can display a flat binding mode with the surface. Comparatively, the water solvent has an obvious impeding effect on the surface adsorption due to the hydrogen bonding interaction between PEG chain and water molecules. The thermodynamic free energy shows that the interaction between pyrene and carbon surface provides the main interaction contribution to the adsorption performance.

Batch equilibrium and kinetic studies of naphthalene and pyrene adsorption onto coconut shell as low-cost adsorbent

This study investigated the use of coconut shell as a non-conventional and low-cost adsorbent for the removal of naphthalene and pyrene from synthetic waste water. Coconut shells were used to adsorb naphthalene and pyrene at varying initial naphthalene and pyrene concentrations, adsorbent dosage, particle size and agitation time. The results of the batch equilibrium adsorption studies revealed that adsorption capacity decreased with increase in particle size and increased with increase in adsorbent dosage. The equilibrium adsorption data were analysed by two-parameter models of Langmuir and Freundlich and three-parameter models of Redlich-Peterson, Sips and Toth isotherms. The results showed that the equilibrium adsorption data for naphthalene and pyrene sorbent systems fitted well with all the tested adsorption isotherm models which can adequately describe the adsorption behaviour of naphthalene and pyrene onto coconut shell. The adsorption kinetic data obtained at 100 mg/l initial naphthalene and pyrene concentrations were analysed using Lagergren pseudo-first order, Elovich and intraparticle diffusion rate equations. The rate equations fitting showed that the adsorption kinetic data generally fit the three rate equations tested from which the rate constants and diffusion rate constants were estimated. However, the Lagergren pseudo first-order rate equation gave the best fit and, thus the process followed the first-order rate kinetics. Therefore, coconut shells being an agricultural waste product have the potential to be used as a low-cost adsorbent for the removal of organic pollutant from waste water.

Adsorption of Naphthalene, Phenanthrene and Pyrene from Aqueous Solution Using Low-Cost Activated Carbon Derived from Agricultural Wastes

In this work, the adsorption of polycyclic aromatic hydrocarbons (PAHs) from aqueous solution by rice husk activated carbon (RHAC) was compared with adsorption using conventional, powdered activated carbon as the adsorbent. The adsorbent capacity of RHAC was found to be higher than all other agricultural and industrial adsorbents evaluated. The kinetics of PAHs was similar even after 24 hours. The removal of PAH occurred in the following order: naphthalene < phenanthrene < pyrene. Our study results show that molecular weight and solubility play vital roles in the adsorption of PAH on RHAC. The study results pointed to the occurrence of an intra-particle mechanism in all cases. The isotherm models that best represented the data obtained were Freundlich for naphthalene, Redlich-Peterson for phenanthrene, and Langmuir for pyrene. The results of this study were compared with previous studies.

Phytoremediation of Pyrene Contaminated Soils by Different Plant Species

AbstractPolycyclic aromatic hydrocarbons (PAHs) present serious problems in the environment because they may affect negatively human health and alter native ecological communities. Phytoremediation has long been recognized as an efficient method of eliminating PAH pollutants from soil. A pot experiment was conducted in greenhouse conditions to investigate the capability of three plant species, Medicago sativa, Brassica napus, and Lolium perenne, to promote the degradation of pyrene by measuring their growth on pyrene‐contaminated soils. After 90 days, pyrene concentration in soils declined by 32, 30, and 28%, respectively, with M. sativa, B. napus, and L. perenne, whereas it decreased only by 18% in the control soil without plants. These results indicated that pyrene was successfully removed by plants used. In particular, M. sativa showed the highest capacity for pyrene dissipation in soil, whereas L. perenne was more efficient in limiting adverse effects of pyrene contamination. In addition, the contaminant pyrene was undetectable in shoots and roots of the three species, likely because plant roots can stimulate soil microbial biomass and oxygen transport to the rhizosphere, thus facilitating indirectly the degradation process of pyrene. Further studies are in progress to evaluate the possible adsorption of pyrene to soil organic matter.

Adsorption of naphthalene and pyrene from isooctane solutions on commercial activated carbons

The adsorption of naphthalene and pyrene on two different types of commercial activated carbons was stud- ied by batch and column experiments. Adsorption equilib- rium was measured at three different temperatures. Heats of adsorption were estimated from the equilibrium results and compared to other previous reports. From the column experiments, using parameters obtained from the batch ex- periments and literature correlations, effective surface diffu- sivities were estimated for naphthalene and pyrene on both adsorbents in different feed concentrations. The corrected diffusivities, using Darken equation, appear to be almost constant for naphthalene (ca. 1.3 · 10 −8 cm 2 /min), and for pyrene (ca. 2.3 · 10 −10 cm 2 /min), in both activated carbons.

Study of Pyrene Adsorption on Two Brazilian Soils

This study investigated pyrene adsorption on two contrasting Brazilian soils: a Kandiudult and a Vertisol. It was found that the time taken to reach thermodynamic equilibrium depended on the soil type. The curves for different pyrene-to-soil mass ratios for Vertisol soil showed significant differences. This is probably related to the presence of 2:1 clays that may increase the adsorption of pyrene due to the resulting interlamellar space. The adsorption of pyrene on the Kandiudult showed, in general, good agreement with the Langmuir isotherm. In the case of the Vertisol, there was good agreement with the linear isotherm. The kinetic model that best explains the adsorption in Kandiudult was the pseudo second-order model. For the Vertisol, the Morris Weber model best explains the behavior of pyrene.

Studies on the adsorption of naphthalene and pyrene from aqueous medium using ripe orange peels as adsorbent

The effectiveness of dried ground orange peels in adsorbing naphthalene and pyrene from an aqueous stream has been investigated in terms of variation in concentration, adsorbent dosage, agitation time and particle size. Experimental batch data was correlated by Freundlich and Langmuir isotherm models. The Freundlich isotherm best described the adsorption process as the adsorption data fitted well into the model. The adsorption capacity and energy of adsorption were obtained as 7.519mg/g and 0.0863mg-1, and 3.8168mg/g and 0.0334mg-1 for naphthalene and pyrene respectively. The adsorption from the aqueous solution was observed to be time dependent while equilibrium time was found to be 100 and 120 minutes for naphthalene and pyrene respectively. Adsorption increased with increase in adsorbent dosage and was maximum at between 5 to 7g for naphthalene and 6 to 8g for pyrene. The maximum adsorption was observed using a particle size of 2.0mm. The rate of adsorption using the first order rate expression by Lagergren for naphthalene and pyrene were 0.007 and 0.006 min-1 respectively. These results therefore suggest that naphthalene is more selectively adsorbed than pyrene using ripe orange peel as adsorbent.KEY WORDS: Naphthalene, Pyrene, Adsorption, Adsorbent, Ripe orange peels.

Effect of short-chain organic acids and pH on the behaviors of pyrene in soil–water system

The effects of five short-chain organic acids (SCOAs) on the behaviors of pyrene in soil–water system were investigated. The influences of the quantity and species of organic acids, pH, and soil dissolved organic matter were considered. The results showed the presence of SCOAs inhibited the adsorption and promoted the desorption of pyrene in the following order: citric acid > oxalic acid > tartaric acid > lactic acid > acetic acid. The decreased extents of pyrene adsorption performance enhanced with increasing SCOA concentrations, while the decreasing rate became less pronounced at high SCOA concentrations. In the presence of organic acids, the adsorption ability of pyrene decreased with increasing pH. However, there was a slight increase of pyrene adsorption with the addition of oxalic acid, tartaric acid and citric acid above pH 8. The capacity for pyrene retention differentiated significantly between the soils with and without dissolved organic matter. The presence of SCOAs was also favorable for the decrease of pyrene adsorption on soil without dissolved organic matter. The results of this study have important implications for the remediation of persistent organic pollutants in soil and groundwater.

Effect of organic carbon and mineral surface on the pyrene sorption and distribution in Yangtze River sediments

The effect of organic carbon (OC) and mineral surface on the sorption of polycyclic aromatic hydrocarbon (PAH) pyrene molecule to four Yangtze River sediments was investigated by sorption batch techniques using fluorescence spectroscopy. Pyrene sorption to the mineral fraction was estimated with model sorbent illite, the main clay mineral in Yangtze sediment. The Freundlich model fitted sorption to illite and to sediments was normalized to the specific surface area (SSA). Comparison of the SSA-normalized sorption capacities of illite and sediments suggests a negligible contribution of the pyrene sorption to the mineral fraction. In addition, composite models, such as the linear Langmuir model (LLM) and the linear Polanyi–Dubinin–Manes model (LPDMM) were applied for fitting the sorption of pyrene to the pristine sediments. The application of composite models allows assessing the partition of pyrene into amorphous organic carbon (AOC) and the adsorption in the porous structure of black carbon (BC). The modelling results indicate that the pyrene adsorption to the minor BC components (<0.2%) is more effective than the partition to AOC (0.5–1.3%). Besides the pristine sediments, sediments preheated at 375 °C were also studied, in which the AOC fraction was removed during the preheating treatment. The modelling results with LPDMM and Polanyi–Dubinin–Manes model (PDMM) indicate a similar adsorption capacity of BC in pristine and preheated sediments, respectively. The low AOC concentrations in sediments do not diminish the BC micropore filling with pyrene. Simulation of pyrene distribution in the investigated Yangtze River sediments support the importance of the BC fraction in the PAH immobilization under environmental conditions.

Adsorption and Desorption Kinetics of Naphthalene, Anthracene, and Pyrene in Soil Matrix

The adsorption and desorption kinetics of naphthalene, anthracene, and pyrene in a soil slurry reactor at ambient conditions have been investigated to ascertain the mechanisms controlling the retention and release rates of these compounds in the soil matrix. A stirred-flow method was employed to perform the experiments. The extent of partitioning for the polycyclic aromatic hydrocarbons (PAHs) tested was found to be dependent on their solubility and diffusivity in the aqueous phase. Apparent adsorption and desorption rate coefficients were determined using the Langmuir and Freundlich isotherm models. Equilibrium adsorption and desorption at the external surface and in the internal pore of the soil particle obeyed the Freundlich isotherm equation. The pseudo-equilibrium condition established at the minimum contact time suggests that equilibrium adsorption attained for the contaminant PAHs was not instantaneous but rather time dependent.

Surface functionalized mesoporous silicas as adsorbents for aromatic contaminants in aqueous solution

A hexagonal mesoporous silica (HMS) and its postfunctionalized counterparts with propyl (P-HMS) and aminopropyl (AMP-HMS) were prepared and characterized by elemental analysis, N2 adsorption, powder x-ray diffraction, Fourier-transform infrared, and surface charge measurements. Batch experiments were further performed to systematically investigate adsorption properties of these materials toward two nonpolar aromatic compounds (pyrene and pentachlorobenzene) and three phenolic compounds (2,4-dichlorophenol, pentachlorophenol, and 4-methyl-2,6-dinitrophenol) in aqueous solutions. The adsorption isotherms were well described by the Freundlich model and varied in adsorption linearity. For HMS and P-HMS, the adsorption of pyrene and pentachlorobenzene was much stronger than that of pentachlorophenol at pH slightly greater than 6. Alternatively, for AMP-HMS, pentachlorophenol and 4-methyl-2,6-dinitrophenol showed comparable or stronger adsorption affinity than the other target compounds did, suggesting that a major role is played by electrostatic interactions of the two phenols. Furthermore, adsorption decreased with increasing pH for all adsorbate-adsorbent combinations except that of pentachlorophenol and 4-methyl-2,6-dinitrophenol on AMP-HMS, which showed bell-shaped curves with the maximum adsorption at pH close to the pK(a). The advantages of reversible adsorption and fast adsorption/desorption kinetics (<15 min), as compared to commercial microporous activated carbons, make AMP-HMS a promising candidate to remove selected phenolic compounds in water treatment.

Effects of cetyltrimethylammonium chloride on uptake of pyrene by fish gills

Laboratory experiments were carried out to study the effects of cationic surfactant cetyltrimethylammonium chloride (CTAC) on the uptake of pyrene by fish gills. The uptake (including adsorption) of pyrene by gills of the color carp (C.carpio var. color) exposed to 20–100 μg/L pyrene in the presence or absence of 0.2–1.0 mg/L CTAC were determined. The sorption of pyrene by mucus was preliminary studied using a four-step sequential extraction procedure. Fish gills were extracted with H2O, 0.01 M CaCl2, CH3OH and a mixture of 1:1 n-C6H14/CH2Cl2 in sequence. Results showed that pyrene mostly accumulated in mucus and on the surface of gills tissue; the cationic surfactant CTAC significantly enhanced these accumulation or adsorption on the fish gills (not in gills). CTAC could affect the bioavailability of pyrene in aquatic systems.

Effects of sodium dodecylbenzenesulfonate on uptake of pyrene by fish gills

Laboratory experiments were carried out to study the effects of anionic surfactant sodium dodecylbenzenesulfonate (SDBS) on the uptake of pyrene by fish gills. The uptake (including adsorption) of pyrene by gills of the color carp (C. carpio var. color) exposed to 20–100 μg/L pyrene in the presence or absence of 0.2–6.0 mg/L SDBS were determined. The sorption of pyrene by mucus was preliminary studied using a four-step sequential extraction procedure. Fish gills were extracted with H2O, 0.01 M CaCl2, CH3OH and a mixture of 1:1 n-C6H14/CH2Cl2 in sequence. Results showed that SDBS significantly affected these accumulation or adsorption on the fish gills (not in gills). SDBS could affect the bioavailability of pyrene in aquatic systems.

Adsorption of Polycyclic Aromatic Hydrocarbons onto Activated Carbon from Non‐Aqueous Media: 1. The Influence of the Organic Solvent Polarity

Polycyclic aromatic hydrocarbons (PAHs) can be formed easily during the refinery processes of crude petroleum. Their accumulation poses serious operating problems and their removal is of great importance. In this investigation we tested the ability of activated carbon to remove a number of the PAHs compounds from mixtures of organics solvents, with different chemicals structures and polarities. Batch adsorption tests were used to investigate the effect of chemical structures and polarities of solvents on the adsorption of naphthalene, anthracene, and pyrene on activated carbon. Our investigation revealed that aromatic solvents have high affinity for activated carbon and therefore, inhibit PAHs adsorption, while polar solvents have low affinity for activated carbon and consequently the adsorbent sites are more available for the PAHs molecules. This behavior can be explained by the fact that the PAHs and benzene molecules are able to form π–π complex between π‐ electrons of benzene rings and active sites on an activated carbon surface. An increase in the molecular weight of aliphatic solvents such as hexane and heptane has little effect on adsorption of PAHs to activated carbon. However, cyclic hydrocarbon solvents such as cyclohexane increase the adsorption of small PAHs and decrease the adsorption of heavier PAHs molecules, probably as a result of differences in solubilities.

Superior performance in deep saturation of bulky aromatic pyrene over acidic mesoporous Beta zeolite-supported palladium catalyst

Palladium species were loaded into mesoporous Beta zeolite (Beta-H), and transmission electron microscopy images showed that the Pd particles are located in both mesopores and micropores. As a model reaction, the deep hydrogenation of bulky aromatic pyrene showed that the Pd/Beta-H catalyst exhibits higher activity than Pd/Beta, Pd/Al-MCM-41, and Pd/ γ-Al 2O 3 catalysts. The superior performance of the Pd/Beta-H catalyst is attributed to its unique porous structure and acidity. The mesoporous volume in Beta-H (0.17 cm 3/g) is greater than that of Beta (0.06 cm 3/g), which is advantageous for adsorption and mass transport of pyrene over Pd/Beta-H catalyst. The amount of acidic sites is greater on Beta-H (480 μmol/g) than on Al-MCM-41 (280 μmol/g) and γ-Al 2O 3 (220 μmol/g), which also favors improved catalytic activity in hydrogenation of pyrene over Pd/Beta-H catalyst.

Adsorption of Polycyclic Aromatic Hydrocarbons by Carbon Nanomaterials

Carbon nanomaterials are novel manufactured materials, having widespread potential applications. Adsorption of hydrophobic organic compounds (HOCs) by carbon nanomaterials may enhance their toxicity and affect the fate, transformation, and transport of HOCs in the environment. In this research, adsorption of naphthalene, phenanthrene, and pyrene onto six carbon nanomaterials, including fullerenes, single-walled carbon nanotubes, and multiwalled carbon nanotubes was investigated, which is the first systematic study on polycyclic aromatic hydrocarbons (PAHs) sorption by various carbon nanomaterials. All adsorption isotherms were nonlinear and were fitted well by the Polanyi-Manes model (PMM). Through both isotherm modeling and constructing "characteristic curve", Polanyi theory was useful to describe the adsorption process of PAHs by the carbon nanomaterials. The three fitted parameters (Q0, a, and b) of PMM depended on both PAH properties and the nature of carbon nanomaterials. For different PAHs, adsorption seems to relate with their molecular size, i.e., the larger the molecular size, the lower the adsorbed volume capacity (Q0), but higher a and b values. For different carbon nanomaterials, adsorption seems to relate with their surface area, micropore volume, and the volume ratios of mesopore to micropore. Quantitative relationships between these sorbent properties and the estimated parameters of PMM were obtained. These relationships may represent a first fundamental step toward establishing empirical equations for quantitative prediction of PAH adsorption by carbon nanomaterials and possibly other forms of carbonaceous (geo-) sorbents, and for evaluating their environmental impact. In addition, high adsorption capacity of PAHs by carbon nanotubes may add to their high environmental risks once released to the environment, and result in potential alteration of PAHs fate and bioavailability in the environment.

C18-Modified Metal-Colloid Substrates for Surface-Enhanced Raman Detection of Trace-Level Polycyclic Aromatic Hydrocarbons in Aqueous Solution

Metal colloids immobilized on a glass support substrate are modified with a self-assembled alkylsilane (C18) layer to promote adsorption of polycyclic aromatic hydrocarbons from aqueous solutions. Detection of these compounds from low concentration solutions is accomplished by using surface-enhanced Raman scattering (SERS). SERS spectra of pyrene adsorbed to C18-modified immobilized silver colloids are dominated by Raman bands that are not consistent with pyrene and indicate that pyrene undergoes a chemical reaction at the surface. The origins of this surface product are investigated, and it is determined that silver and oxygen are required to form the product, whose Raman spectrum is consistent with oxidation to a quinone. When a C18-modified gold-colloid substrate is used, Raman scattering consistent with unreacted pyrene is observed. The adsorption and detection of pyrene adsorbed from low (2 ppb) concentration aqueous solutions onto C18-modified gold-colloid substrates is reported; naphthalene and phenanthrene are detected at approximately 5 ppb. Adsorption kinetics are rapid (<5 min), and the concentration-dependent SERS response is consistent with a Langmuir isotherm.