Evaluation of butyl rubber as sorbent material for the removal of oil and polycyclic aromatic hydrocarbons from seawater.

Ecological disasters resulting from oil spills have created a great need to find more efficient materials for oil spill cleanup. This research highlights the use of a novel macroporous polymeric material based on butyl rubber (BR) as a sorbent in an oil spill cleanup. The sorption capacity of BR for crude oil and petroleum products is 15-23 g g(-1) as compared to the value of 10-16 g g(-1) obtained using a nonwoven polypropylene (PP), a widely used commercial oil sorbent. BR sorbent is reusable after simple squeezing and its continuous sorption capacity for crude oil is 7.6 g g(-1) in each cycle, about 3 times the capacity of the PP sorbent BR sorbents also remove efficiently polycyclic aromatic hydrocarbons (PAHs) such as acenaphthene and pyrene from seawaters. The results suggest that the rubber sorbents are a better alternative to the widely used PP sorbents by improving the efficiency of oil sorption and the reusability of the sorbent.

Comparison of thin-film microextraction and stir bar sorptive extraction for the analysis of polycyclic aromatic hydrocarbons in aqueous samples with controlled agitation conditions.

The characterization of a poly(dimethylsiloxane) (PDMS) thin film for active extraction of some polycyclic aromatic hydrocarbons was investigated in both a 1-L aqueous solution and a flow-through system. The thin film was attached to an electric bench-drill at a constant rotation speed for constant agitation and fast extraction. The performance of a PDMS-coated stir bar at a constant stirring speed was also investigated. The comparison showed that the extraction rate was much higher when using the thin film than the stir bar, and that the equilibration time was greatly shortened due to the larger surface area/volume ratio of the thin film. The extraction rate was roughly proportional to surface area of the extraction phase during the initial stage of the extraction process; the amount of analyte extracted was proportional to the ratio of the extraction phase between the thin film and the stir bar. Different agitation and stirring rates of the thin film and stir bar were applied for extraction, revealing that extraction efficiency can be improved by increasing rotation rate. The application of rotated thin film in the field proved it is a valid and easily operated method for the determination of polycyclic aromatic hydrocarbons (PAHs) in a campus river. However, the stir bar is not as convenient as a thin film in field sampling.

Macroporous molecularly imprinted polymer/cryogel composite systems for the removal of endocrine disrupting trace contaminants.

A new concept for the preparation of selective sorbents with high flow path properties is presented by embedding molecularly imprinted polymers (MIPs) into various macroporous gels (MGs). A MIP was first synthetized with 17beta-estradiol (E2) as template for the selective adsorption of this endocrine disrupter. The composite macroporous gel/MIP (MG/MIP) monoliths were then prepared at subzero temperatures. Complete recovery of E2 from a 2 microg/L aqueous solution was achieved using the polyvinyl alcohol (PVA) MG/MIP monoliths whereas only 49-74% was removed with non-imprinted polymers (when no template was used). The PVA MG/MIP monolith columns were operated at almost 10 times higher flow rate (50 mL/min) compared to the MIP columns with operation flow rate of 1-5 mL/min. The possibility for processing the particulate containing wastewater effluents at high flow rates with selectivity on E2 removal, as well as the easy preparation of the monoliths, make the macroporous MG/MIP systems attractive and robust sorbents for the clean up of water from endocrine disrupting trace contaminants.

Multiple dual-mode centrifugal partition chromatography, a semi-continuous development mode for routine laboratory-scale purifications.

Nowadays, centrifugal partition chromatography (CPC) separations can be routinely achieved at the laboratory scale. The solvent system selection has been made easy, as generic sets of solvent systems are described in publications and books. This approach, however, generally reduces the scope of optimization strategies for two important parameters: selectivity and sample solubility. This can be very limiting for the preparative separation of structurally similar compounds. Multiple dual-mode (MDM) CPC has been developed to provide an easy-to-use alternative technique to circumvent this problem. A MDM separation consists of a succession of dual-mode runs (i.e. multiple inversion of stationary and mobile phase) that can only be achieved because both chromatographic phases are liquids. This original elution mode is thus a semi-continuous process with a classical sample injection and which only requires a single CPC column. Underlying mechanisms of MDM were studied using a model mixture of acenaphthylene and naphthalene. A mixture of two synthetic pairs of diastereomers was then successfully submitted to MDM CPC, in the framework of the synthesis of biologically active compounds.

High-performance liquid chromatographic stationary phases based on polysiloxanes with different chain lengths thermally immobilized on silica supports.

Reversed phases for high-performance liquid chromatography (RP-HPLC) were obtained by thermal immobilization of polysiloxanes having different length chains (C1, C8 and C14) onto HPLC silica particles. The importance both of percent loading of the stationary phase promoted by each immobilization procedure and of the length of the lateral chain of the polymer on the chromatographic performances of the phases obtained is compared and discussed.

occupational exposure to aromatic hydrocarbons at a coke plant: Part II. Exposure assessment of volatile organic compounds.

The objective of the study is to assess the external and internal exposures to aromatic hydrocarbons in the tar and oil naphthalene distillation processes at a coke plant. 69 workers engaged as operators in tar and oil naphthalene distillation processes and 25 non-exposed subjects were examined. Personal analyses of the benzene, toluene, xylene isomers, ethylbenzene, naphthalene, indan, indene and acenaphthene in the breathing zone air allowed us to determine the time weighted average exposure levels to the aromatic hydrocarbons listed above. The internal exposure was investigated by measurement of the urinary excretion of naphthols, 2-methylphenol and dimethylphenol isomers by means of gas chromatography with a flame ionization detection (GC/FID). Urine metabolites were extracted after enzymatic hydrolysis by solid-phase extraction with styrene-divinylbenzene resin. The time-weighted average concentrations of the hydrocarbons detected in the breathing zone air shows that the exposure levels of the workers are relatively low in comparison to the exposure limits. Statistically significant differences between average concentrations of aromatic hydrocarbons (benzene, toluene, xylene isomers) determined at the workplaces in the tar distillation department have been found. Concentrations of the naphthalene and acenaphthene detected in workers from the oil distillation department are higher that those from the tar distillation department. Concentrations of naphthols, 2-methoxyphenol and dimethylphenol isomers in the urine of occupationally exposed workers were significantly higher than those of non-exposed subjects. Concentrations of the 2-methoxyphenol and dimethylphenol isomers in urine were significantly higher for the tar distillation workers, whereas concentrations of naphthols were higher for the oil naphthalene distillation workers. Operators at the tar and naphthalene oil distillation processes are simultaneously exposed to a mixture of different hydrocarbons, mainly benzene and naphthalene homologues.