Sorption of polycyclic aromatic hydrocarbons from aqueous solution by hexadecyltrimethylammonium bromide modified fibric peat

BACKGROUND: Fibric peat was modified by hexadecyltrimethylammonium bromide (HTAB) to improve its performance in sorption of polycyclic aromatic hydrocarbons (PAHs). The raw fibric peat (P‐R) and surfactant modified peat (P‐HTAB) were characterized by capillary rise test to determine the effect of HTAB on surface hydrophobicity. Effect of contact time was also investigated. Batch sorption data were fitted to the Freundlich model and pseudo‐second‐order model for isotherm and kinetics study. RESULTS: P‐HTAB had a more hydrophobic surface than P‐R. After modification, the sorption coefficients (K_OC) of naphthalene, phenanthrene and pyrene on fibric peat increased from 1590, 29661 and 204171 mL g^?1 to 2006, 52410 and 358569 mL g^?1, respectively; the sorption rate constants of naphthalene, phenanthrene and pyrene increased from 0.00057, 0.00036 and 0.00051 g µg^?1 min^?1 to 0.00062, 0.00140 and 0.00155 g µg^?1 min^?1, respectively. The sorption coefficients of PAHs were positively correlated with the octane‐water partition coefficients of PAHs. CONCLUSIONS: The hydrophobicity of fibric peat was enhanced through modification by HTAB, which resulted in the improved sorption rate and sorption capacity for PAHs. The sorption performance of P‐HTAB reveals that it is an effective biosorbent for PAHs and has potential for treatment of wastewater containing hydrophobic organic contaminants. Copyright © 2010 Society of Chemical Industry     

Study on preparation and properties of PVA‐SA‐PHB‐AC composite carrier for microorganism immobilization

Polyvinyl alcohol(PVA) bead crosslinked with boric acid has been widely utilized as a microorganism immobilization carrier. However, it has some disadvantages such as drastic cell viability loss, small adsorption capacity and mass transfer limitation. To improve upon these drawbacks, a new method to prepare PVA composite pieces with the addition of activated carbon (AC) and poly‐3‐hydroxybutyrate(PHB) was explored through a combination of freezing/thawing and the boric acid method and by using Tween‐80 to improve the mass transfer performance of hydrophobic organics. m‐Cresol and pyrene were used as representative compounds with benzene ring structures to model hydrophilic and hydrophobic organics in order to test the performance of PVA pieces. The results showed that, compared with the boric acid method alone, a combination of freezing/thawing and the boric acid method led to a decrease in total organic carbon(TOC) loss from 0.315 g g^?1 to 0.033 g g^?1 and increased the oxygen uptake rate(OUR) of microorganisms from 0.03 mg L^?1·min^?1 to 0.22 mg L^?1 min^?1. The m‐cresol equilibrium adsorption amount of the PVA‐SA(sodium alginate)‐PHB‐AC piece was 2.80 times that of the PVA‐SA piece. The diffusion coefficient of pyrene in the PVA‐SA‐PHB‐AC piece increased from 0.53×10^?9 m² min^?1 to 2.30×10^?9 m² min^?1 with increasing concentrations of Tween‐80 from 1000 mg L^?1 to 5000 mg L^?1. The PVA‐SA‐PHB‐AC composite carrier demonstrated great scope for immobilizing microorganisms for practical wastewater bio‐treatment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39837.     

Sorption capacity of a new generation granular activated carbon—Bio‐Sep® bead—and its use in a suspended growth bioreactor

BACKGROUND: A new generation granular activated carbon—Bio‐Sep® beads—consist of 25% polymer (Nomex) and 75% powdered activated carbon. The porous structure and high surface area of these beads make them suitable for sorbent in adsorption columns, and for immobilization media in bioreactors. The aim of this study was to study the sorption characteristics of Bio‐Sep® beads for methyl t‐butyl ether (MTBE) and t‐butyl alcohol (TBA), and to demonstrate the advantage of their usage in a suspended growth bioreactor. RESULTS: The maximum uptake capacity of Bio‐Sep® beads for MTBE and TBA, in the studied concentration range (10–100 mg L^?1), was observed to be 9.73 and 6.23 mg g^?1, respectively. A 52 h desorption experiment resulted in 13.6–42.2% MTBE and 33–53% TBA desorption corresponding to the initial solid phase concentrations of 1.68–9.73 mg g^?1 and 1.41–6.23 mg g^?1, respectively. The sorption of TBA on the Bio‐Sep® beads was significantly hindered by the presence of MTBE. The addition of 10 g Bio‐Sep® beads (dry weight) in a suspended growth bioreactor was able to eliminate the inhibitory effect of 150 mg L^?1 MTBE. CONCLUSIONS: At an equilibrium aqueous phase concentration (C_e) of 1 mg L^?1, the solid phase concentration (q_e) on Bio‐Sep® beads were observed as 1.44 and 0.47 mg g^?1 for MTBE and TBA, respectively. The results obtained in this study indicate that Bio‐Sep® beads have reasonable sorption and desorption characteristics, which can be successfully exploited for the removal/degradation of toxic organic pollutants in high rate bioreactors. Copyright © 2007 Society of Chemical Industry     

Biosorption of phenolic compounds by the brown alga Sargassum muticum

Phenol, 2‐chlorophenol (2‐CP), and 4‐chlorophenol (4‐CP) biosorption on Sargassum muticum, an invasive macroalga in Europe, has been investigated. The efficiency of this biosorbent was studied measuring the equilibrium uptake using the batch technique. A chemical pre‐treatment with CaCl₂ has been employed in this study in order to improve the stability as well as the sorption capacity of the algal biomass. The influence of pH on the equilibrium binding and the effect of the algal dose were evaluated. The experimental data at pH = 1 have been analysed using Langmuir and Freundlich isotherms. It was found that the maximum sorption capacity of chlorophenols, q_max = 251 mg g^?1 for 4‐CP and q_max = 79 mg g^?1 for 2‐CP, as well as that of a binary mixture of both chlorophenols, q_max = 108 mg g^?1, is much higher than that of phenol, q_max = 4.6 mg g^?1. Moreover, sorption kinetics have been performed and it was observed that the equilibrium was reached in less than 10 h. Kinetic data have been fitted to the first order Lagergren model, from which the rate constant and the sorption capacity were determined. Finally, biosorption of the phenolic compounds examined in the present study on Sargassum muticum biomass was observed to be correlated with the octanol‐water partitioning coefficients of the phenols. This result allows us to postulate that hydrophobic interactions are the main responsible for the sorption equilibrium binding. Copyright © 2006 Society of Chemical Industry     

Thermophysical properties of laboratory-prepared corn/wheat dried distillers grains and dried distillers solubles dehydrated with superheated steam and hot air

The objective of this study was to dry–wet distillers grains and centrifuged solubles and to examine the effect of two different drying media, superheated steam and hot air, at different drying temperatures (110, 130, and 160°C), moisture contents (5–30% wb), and percentages of solubles’ presence (0 or 100%) on some thermophysical properties of laboratory-prepared corn/wheat dried distillers co-products, including geometric mean diameter (d_g), particle density (ρ_p), bulk density (ρ_b), bulk porosity (?_b), specific heat (C), effective thermal diffusivity (α_eff), and bulk thermal conductivity (λ_b). The values of d_g of corn/wheat dried distillers co-products ranged from 0.358 ± 0.001 to 0.449 ± 0.001 mm. Experimental values of ρ_p, ρ_b, and ?_b varied from 1171 ± 6 to 1269 ± 3 kg m^?3, from 359 ± 7 to 605 ± 5 kg m^?3, and from 0.54 ± 0.01 to 0.71 ± 0.01 kg m^?3, respectively. The values of α_eff were between 0.58 × 10^?7 and 0.93 × 10^?7 m² s^?1. The calculated values of C ranged from 1887 ± 11 to 2599 ± 19 J kg^?1 K^?1, and the values of λ_b of corn/wheat dried distillers co-products ranged from 0.06 ± 0.01 to 0.09 ± 0.01 W m^?1 K^?1. Multiple linear regression prediction models were developed to predict the changes in d_g, ρ_p, ρ_b, ?_b, C, α_eff, and λ_b of laboratory-prepared corn/wheat dried distillers co-products with different operational factors.     

Experimental review of microwave-assisted methods for synthesis of functional resins for sorption of rhenium(VII)

The microwave-assisted syntheses of anion exchange resins were carried out in the presence of selected organic solvents and amines, applying variable radiation density. The polymers were used for sorption of ReO₄^–, after which, the collected results were set together with the applied synthesis parameters. The greatest Re(VII) sorption capacity of 470 mg Re g^?1 was revealed by a resin obtained within 10 min in the presence of N,N-dimethylformamide and 2-methylimidazole at power of 160 W. The outcome of the present research constitutes a set of guides allowing to enhance the resource-efficiency of the process.     

Adsorption of cadmium and zinc from aqueous solution on natural and activated bentonite

The adsorption of cadmium and zinc ions on natural bentonite heat-treated at 110°C or at 200°C and on bentonite acid-treated with H₂SO₄ (concentrations: 0·5 mol dm^?3 and 2·5 mol dm^?3), from aqueous solution at 30°C has been studied. The adsorption isotherms corresponding to cadmium and zinc may be classified respectively as H and L types of the Giles classification which suggests the samples have respectively a high and a medium affinity for cadmium and zinc ions. The experimental data points have been fitted to the Langmuir equation in order to calcualte the adsorption capacities (X_m) and the apparent equilibrium constants (K_a) of the samples; X_m and K_a values range respectively for 4·11 mg g^?1 and 1·90 dm³ g^?1 for the sample acid-treated with 2·5 mol dm^?3 H₂SO₄ [(B)-A(2·5)] up to 16·50 mg g^?1 and 30·67 dm³ g^?1 for the natural sample heat-treated at 200°C [B-N-200], for the adsorption process of cadmium, and from 2·39 mg g^?1 and 0·07 dm³ g^?1, also for B-A(2·5), up to 4·54 mg g^?1 and 0·45 dm³ g^?1 [B-N-200], for the adsorption process of zinc. X_m and K_a values for the heat-treated natural samples were higher than those corresponding to the acid-treated ones. The removal efficiency (R) has also been calculated for every sample; R values ranging respectively from 65·9% and 8·2% [B-A(2·5)] up to 100% and 19·9% [B-N-200], for adsorption of cadmium and zinc.     

Magnetite‐loaded calcium‐alginate (MLCA) particles as potential sorbent for removal of Ni(II) from aqueous solution

This work is focused on the removal of Ni(II) from aqueous solutions by sorption onto newly developed magnetite‐loaded calcium alginate particles. The uptake of Ni(II) by these magnetite particles, with their mean geometrical diameter 84 and 508 μm, is best described by the Freundlich isotherm and the constants K_F and 1/n were found to be 3.491 mg g^?1, 0.731 and 0.793 mg g^?1 and 0.907, respectively. The mean sorption energy, as determined by Dubinin‐Radushkevich isotherm for 508‐ and 84‐μm sized particles was evaluated to be 8.9 and 8.0 kJ mol^?1, respectively, thus, suggesting the ion‐exchange mechanism for uptake process. Of the various kinetic models proposed, the kinetic Ni(II)‐uptake data were best interpreted by “Simple Elovich” and “Power function” as suggested by their higher regression values. The almost linear nature of plots of log(% sorption) versus log(time) was indicative of intraparticle diffusion. The values of intraparticle diffusion coefficients K_id were found to be 63.49 × 10^?2 and 94.35 × 10^?2 mg l^?1 min^0.5. The intraparticle diffusion was also confirmed by Bangham equation. Finally, various thermodynamic parameters were evaluated. The negative ΔG° indicated spontaneous nature of uptake process while positive ΔH° value suggested exothermic nature of the sorption process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Diffusivities of dichloromethane in poly(lactide‐co‐glycolide)

Diffusion of dichloromethane in poly(lactide‐co‐glycolide) (PLGA), the rate‐limiting step in the later stages of drying of microparticles formed in common encapsulation processes, was studied by the step‐change sorption technique in a dynamic vapor sorption apparatus. Methods were developed to create films of polymer with the appropriate thicknesses for accurate diffusion determination over a wide range of solvent composition. Mutual diffusivities were measured at 5, 25, and 35°C from 10 to 70 wt % solvent. Values range from 2 × 10^?10 m²/s at high solvent compositions to as low as 1 × 10^?13 m²/s at solvent compositions just above the glass transition of the mixture. Equilibrium sorption isotherms were measured in the same apparatus and agreed favorably with Flory‐Huggins theory using a value of χ = 0.31. The glass transition temperatures of the system were measured over the range of 0–11 wt % solvent content by modulated differential scanning calorimetry. The composition dependence was fit to the Fox equation, which estimated values of the pure polymer and the solvent T_g to be 39.3 and ?131°C, respectively. These values, along with the diffusivity data, were used to deduce the free‐volume parameters specific to PLGA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Sorption Potential of Styrene‐Divinylbenzene Copolymer Beads for the Decontamination of Lead from Aqueous Media

Abstract

The decontamination of lead ions from aqueous media has been investigated using styrene‐divinylbenzene copolymer beads (St‐DVB) as an adsorbent. Various physico‐chemical parameters such as selection of appropriate electrolyte, contact time, amount of adsorbent, concentration of adsorbate, effect of foreign ions, and temperature were optimized to simulate the best conditions which can be used to decontaminate lead from aqueous media using St‐DVB beads as an adsorbent. The atomic absorption spectrometric technique was used to determine the distribution of lead. Maximum adsorption was observed at 0.001 mol L^?1 acid solutions (HNO₃, HCl, H₂SO₄ and HClO₄) using 0.2 g of adsorbent for 4.83×10^?5 mol L^?1 lead concentration in two minutes equilibration time. The adsorption data followed the Freundlich, Langmuir, and Dubinin‐Radushkevich (D‐R) isotherms over the lead concentration range of 1.207×10^?3 to 2.413×10^?2 mol L^?1. The characteristic Freundlich constants i.e. 1/n=0.164±0.012 and A=2.345×10^?3±4.480×10^?5 mol g^?1 have been computed for the sorption system. Langmuir isotherm gave a saturated capacity of 0.971±0.011 mmol g^?1, which suggests monolayer coverage of the surface. The sorption mean free energy from D‐R isotherm was found to be 18.26±0.75 kJ mol^?1 indicating chemisorption involving chemical bonding for the adsorption process. The uptake of lead increases with the rise in temperature. Thermodynamic parameters i.e. ΔG, ΔH, and ΔS have also been calculated for the system. The sorption process was found to be exothermic. The developed procedure was successfully applied for the removal of lead ions from real battery wastewater samples.     

Potential of Rice Husk for the Decontamination of Silver Ions from Aqueous Media

The sorption behavior of silver ions on rice husk has been investigated in detail. Various physico-chemical parameters were optimized to simulate the best conditions in which this material can be used as an adsorbent. Maximum adsorption was observed at 0.001 mol L^?1 of acid solutions (HNO₃, H₂SO₄ and HClO₄) using 0.5 g of adsorbent for 9.27 × 10^?5 mol L^?1 silver concentration in fifteen minutes equilibration time. The adsorption of silver was decreased with the increase in the concentrations of all the acids used. The kinetic data indicated an intraparticle diffusion process with sorption being pseudo-second order. The determined rate constant k₂ was 14.707 ± 1.832 mol g^?1 min^?1. The adsorption data obeyed the Freundlich, Langmuir, and Dubinin-Radushkevich isotherms over the silver concentration range of 1.85 × 10^?4 to 1.16 × 10^?3 mol L^?1. The characteristic Freundlich constants, that is, 1/n = 0.38 ± 0.033 and K = 0.271 ± 0.104 m mol g^?1 whereas the Langmuir constants Q = (1.504 ± 0.054) × 10^?2 m mol g^?1 and b = (16.582 ± 2.227) × 10³ dm³ mol^?1 have been computed for the sorption system. The sorption mean free energy from the Dubinin-Radushkevich isotherm is 12.16 ± 0.82 kJ mol^?1 indicating ion-exchange mechanism of chemisorption. The uptake of silver increases with the rise in temperature (283–333 K). Thermodynamic quantities, namely, ΔG, ΔS, and ΔH have also been calculated for the system. The sorption process was found to be endothermic. The effect of other cations and anions on the adsorption of silver has also been studied.     

Sorption of copper by a highly mineralized peat in batch and packed‐bed systems

BACKGROUND: The performance of peat for copper sorption was investigated in batch and fixed‐bed experiments. The effect of pH was evaluated in batch experiments and the experimental data were fitted to an equilibrium model including pH dependence. Hydrodynamic axial dispersion was estimated by tracing experiments using LiCl as a tracer. Six fixed‐bed experiments were carried out at copper concentrations between 1 and 60 mg dm^?3 and the adsorption isotherm in dynamic mode was obtained. A mass transport model including convection–dispersion and sorption processes was applied for breakthrough curve modelling. RESULTS: Maximum uptake capacities in batch mode were 22.0, 36.4, and 43.7 mg g^?1 for pH values of 4.0, 5.0, and 6.0, respectively. Uptake capacities in continuous flow systems varied from 36.5 to 43.4 mg g^?1 for copper concentrations between 1 and 60 mg dm^?3. Dynamic and batch isotherms showed different shapes but a similar maximum uptake capacity. Sorbent regeneration was successfully performed with HCl. A potential relationship between dispersion coefficient and velocity was obtained with dispersion coefficients between 5.00 × 10^?8 and 2.95 × 10^?6 m² s^?1 for water velocities ranging between 0.56 × 10^?4 and 5.03 × 10^?4 m s^?1. The mass transport model predicted both the breakpoints and the shape of the breakthrough curves. CONCLUSIONS: High retention capacities indicate that peat can be used as an effective sorbent for the treatment of wastewater containing copper ions. Copyright © 2009 Society of Chemical Industry     

Biosorption of Strontium Ions by Magnetically Modified Yeast Cells

The sorption of Sr²⁺ ions from aqueous solutions on magnetically modified fodder yeast (Kluyveromyces fragilis) cells and their subsequent desorption were studied. The Sr²⁺ sorption increased with increasing pH and reached a plateau between pH 4.0 and 7.0. The changes of temperature slightly influenced the sorption process. The sorption values were 19.5 mg g^?1 and 53.5 mg g^?1 for 10 mg L^?1 and 40 mg L^?1 Sr²⁺ solutions respectively after 20 min incubation at a pH higher than 4. The Langmuir isotherm was successfully used to fit experimental data; the maximum adsorption capacity was 140.8 mg g^?1 under optimal conditions. The adsorbed Sr²⁺ ions can be desorbed with nitric acid (0.1 mol L^?1).     

CYPHOS IL 101 (Tetradecyl(Trihexyl)Phosphonium Chloride) Immobilized in Biopolymer Capsules for Hg(II) Recovery from HCl Solutions

Abstract

A composite polymer (made of gelatin and alginate) was used for the synthesis of Cyphos IL 101-immobilized resins. These resins (with varying size and different ionic liquid (IL) content) have been tested for the recovery of mercury from concentrated HCl solutions (0.1–5 M HCl concentrations). Prior to the study of sorption performance on resins, the reactivity of Cyphos IL 101 versus mercury was tested using solvent extraction methodology. These results showed that the extraction was hardly affected by the concentration of HCl and that an ion exchange mechanism was probably involved in metal recovery (binding of HgCl₄ ^2-). The performance of these resins for Hg(II) recovery was tested through sorption isotherms and uptake kinetics, investigating the effect of resin size, ionic liquid content, metal concentration, agitation speed, and resin state (dry state versus wet state). Sorption capacity (which was proportional to the IL content) can reached up to 150 mg Hg g^?1 in 1 M HCl; this sorption capacity was decreased by increasing chloride concentration. The kinetics were described well by the pseudo-second order equation and by the intraparticle diffusion equation (the so-called Crank's equation). The intraparticle diffusion coefficient was in the range of 10^?11–1.2 × 10^?10 m² min^?1. The kinetic profiles were controlled by the IL content, sorbent dosage, and the sorbent particle size. Drying of the resins significantly decreased diffusion rates in the resins. The presence of competitor metals did not affect sorption capacity except when stable chloro-anionic species such as in the case of Zn(II) were formed. Mercury can be desorbed using 6 M nitric acid solutions; and the sorbent can be recycled for at least six sorption/desorption cycles without significant decrease in the sorption performance.     

Development of a Green Process for the Preparation of Antioxidant and Pigment-Enriched Extracts from Winery Solid Wastes Using Response Surface Methodology and Kinetics

Red grape pomace (RGP), an abundant wine industry solid waste, was used for the recovery of polyphenols and anthocyanin pigments, using ultrasound-assisted extraction and water/glycerol mixtures as the solvent. Glycerol concentration (C_gl) and liquid-to-solid ratio (R_L/S) were first optimized by implementing Box?Behnken experimental design and the process was further studied through kinetics. The optimal conditions were found to be C_gl = 90% (w/v) and R_L/S = 90 mL g^?1, and under these conditions the extraction of total polyphenols (TP) and total pigments (TPm) obeyed first-order kinetics. Maximum diffusivity (D_e) values were 4.22 × 10^?12 and 12.59 × 10^?12 m² s^?1, for TP and TPm, respectively, and the corresponding activation energies were (E_a) 13.94 and 8.22 kJ mol^?1.     

Kinetics of leaching of tunisian phosphate ore particles in dilute phosphoric acid solutions

Van der Sluis et al.'s model was used to determine the rate of the partial dissolution of a Tunisian phosphate rock with dilute phosphoric acid (1.5 mass% P₂O₅). When the temperature rises from 25 to 90°C, for a given particle size, the mass-transfer coefficients, k_L°, vary from 3 × 10^?3 to 8 × 10^?3 m ·s^?1. The corresponding diffusion coefficients, D, lies between 6 × 10^?7 and 27 × 10^?7 m²·s^?1. Activation energy is equal to 14 kJ·mol^?1 and values of k_L°, at 25°C, are in the range of 0.28 × 10^?3 and 4 × 10^?3 m·s^?1 when the agitation speed goes from 220 to 1030 rpm, showing that the leaching process is controlled by diffusion rather than by chemical reaction.     

Zinc(II) Extraction from Hydrochloric Acid Solutions using Amberlite XAD-7 Impregnated with Cyphos IL 101 (Tetradecyl(Trihexyl)Phosphonium Chloride)

Abstract

Cyphos IL 101 (tetradecyl(trihexyl)phosphonium chloride) was immobilized on Amberlite XAD-7. The extractant impregnated resin (EIR) was very efficient at removing Zn(II) from HCl solutions (optimum found between 2 and 4 M HCl). Metal ions were removed as anionic chlorocomplexes (ZnCl₄ ^2?) by ion exchange mechanism. The sorption strongly depended on the Cyphos IL 101 concentration in the EIR. The maximum sorption capacity was close to 20 mg Zn(II) g^?1 EIR (i.e. 0.40 mol Zn(II) mol^?1 Cyphos IL 101). The uptake kinetics were controlled by intraparticle diffusion (D_e: 1.2 10^?11 ? 6 10^?11 m² min^?1). Zn(II) can be easily desorbed using a number of eluents (including water and 0.1 M solution of HNO₃, H₂SO₄, and Na₂SO₄), which maintained performance levels over 5 cycles.     

Role of unburnt carbon in adsorption of dyes on fly ash

Various fly ash samples with different unburnt carbon contents were collected, characterised and tested for adsorption of basic dyes, Methylene Blue and Crystal Violet, in aqueous solution. It was found that unburnt carbon plays a major role in dye adsorption. The mineral matter of fly ash has little adsorption capacity and most of the adsorption capacity of fly ash can be attributed to the unburnt carbon. The fly ash with higher unburnt carbon content will have higher adsorption capacity. For the carbon‐free fly ash, adsorption capacities for Methylene Blue and Crystal Violet are only 2 × 10^?6 mol g^?1 and 1.0 × 10^?6 mol g^?1, respectively, while the adsorption capacities for Methylene Blue and Crystal Violet on carbon‐enriched fly ash are 1.2 × 10^?4 mol g^?1 and 1.0 × 10^?4 mol g^?1, respectively. A two‐site Langmuir adsorption model best describes the adsorption isotherm. Copyright © 2005 Society of Chemical Industry     

ALIPHATIC,POLYCYCLIC AROMATIC HYDROCARBONS AND NITRATED-POLYCYCLIC AROMATIC HYDROCARBONS IN PM 10 IN SOUTHWESTERN MEXICO CITY

A sampling campaign of airborne particles ≤ 10 μ m (PM ₁₀ ) was carried out from February to April of 2004 at the Universidad Nacional Autónoma de México in southwestern Mexico City. The average PM ₁₀ mass concentration was 51 ± 14 μ g m^?3. Extracted organic matter was determined, with a mean of 6.5 ± 1.7 μ g m^?3, which represents 12.9% of PM ₁₀ mass concentration. The standard additions method was used on real samples at four concentration levels for 13 n-alkanes, 14 PAHs and 5 nitro-PAHs. The average concentration for the sum was 99.04 ng m^{? 3} for n-alkanes, 4.9 ng m^?3 for PAHs and 710 pg m^{? 3} for nitro-PAHs. Higher concentrations of n-alkanes > C ₂₄ were found, indicating biogenic emissions as the dominant source. Coronene, benzo[ghi]perylene, benzo[b+j+k]fluoranthenes and indeno[1,2,3-cd]pyrene were the most abundant PAHs, suggesting a strong contribution from incomplete combustion of gasoline. The PAHs considered for calculating BaPE represented 52% of the total PAHs analyzed. The presence of 9-nitroanthracene indicates direct emission from diesel combustion and heterogeneous nitrating reactions on sorbed particles, while 2-nitrofluoranthene, indicates gas-phase reactions with fluoranthene, hydroxyl (OH^?) and/or nitrate (NO ₃ ^?) radicals in the presence of nitrogen oxides (NOx).     

Study of a newly isolated thermophilic bacterium capable of Kuhemond heavy crude oil and dibenzothiophene biodesulfurization following 4S pathway at 60 °C

BACKGROUND: To meet stringent emission standards stipulated by regulatory agencies, the oil industry is required to bring down the sulfur content in fuels. As some compounds cannot be desulfurized by existing desulfurizing processes (such as hydrodesulfurization, HDS) biodesulfurization has become an interesting topic for researchers. Most of the isolated biodesulfurizing microorganisms are capable of desulfurization of refined products whose predominant sulfur species are dibenzothiophenes so biocatalyst development is still needed to desulfurize the spectrum of sulfur‐bearing compounds present in whole crude. RESULTS: The first desulfurizing bacterium active at 60 °C has been isolated, which reduces DBT concentration from 2 mmol L^?1 to 0.1 mmol L^?1 after 95 h, following the 4S pathway. Its DBT desulfurization pattern was represented by the Michaelis‐Menten equation. Various parameters such as V_max, K_m, µ_m, K_s and maximum specific DBT desulfurization rate were calculated which are 0.092 mmol L^?1 h^?1, 3.554 mmol L^?1, 0.157 h^?1, 3.722 mmol L^?1 and 0.192 mmol L^?1 DBT g^?1 DCW (dry cell weight) h^?1, respectively. It can desulfurize 50% of the sulfur content of Kuhemond heavy crude oil (KHC oil) with an initial sulfur content of 7.6%wt in 6 days. Its maximum specific desulfurization rate for KHC oil is equivalent to 0.005 g sulfur g^?1 DCW h^?1. The bacterium was isolated during a heavy crude oil biodesulfurization project initiated by PEDEC, a subsidiary of National Iranian Oil Company. CONCLUSION: The KHC oil sulfur removal efficiency of the bacterium is approximately five times that of BBRC‐9016 bacterium. It removes sulfur selectively without using sulfur‐containing compounds as its carbon source. By applying various media during its isolation, the probability of screening the correct microorganism is increased. Copyright © 2008 Society of Chemical Industry