Adriana Farran

Sorption kinetics of polycyclic aromatic hydrocarbons removal using granular activated carbon: Intraparticle diffusion coefficients

Granular activated carbon (GAC) was evaluated as a suitable sorbent for polycyclic aromatic hydrocarbons (PAHs) removal from aqueous solutions. For this purpose, kinetic measurements on the extraction of a family of six PAHs were taken. A morphology study was performed by means of a scanning electron microscopy (SEM) analysis of GAC samples. Analyses of the batch rate data for each PAH were carried out using two kinetic models: the homogenous particle diffusion model (HPDM) and the shell progressive model (SPM). The process was controlled by diffusion rate the solutes (PAHs) that penetrated the reacted layer at PAH concentrations in the range of 0.2-10 mg L(-1). The effective particle diffusion coefficients (D(eff)) derived from the two models were determined from the batch rate data. The Weber and Morris intraparticle diffusion model made a double contribution to the surface and pore diffusivities in the sorption process. The D(eff) values derived from both the HPMD and SPM equations varied from 1.1 x 10(-13) to 6.0 x 10(-14) m(2) s(-1). The simplest model, the pore diffusion model, was applied first for data analysis. The model of the next level of complexity, the surface diffusion model, was applied in order to gain a deeper understanding of the diffusion process. This model is able to explain the data, and the apparent surface diffusivities are in the same order of magnitude as the values for the sorption of functionalized aromatic hydrocarbons (phenols and sulphonates) that are described in the literature.

Accumulation and distribution of biogenic and pollutant hydrocarbons, pcbs and ddt in tissues of western mediterranean fishes

Abstract Data on hydrocarbons, PCBs and total DDT in muscle, liver and gonads of Mullas barbatus. Trachurus trachurus, Merluccius merluccius, Engraulis enchrasicholus and Micromesistius poutassou collected along the Catalan Coast (NW Mediterrenean) are reported for the first time. The species and the collection sites—off Barcelona to the north (Palamos) and to the south (Ehro Delta)—were selected for the assessment of the effects of coastal pollutant sources on commercially valuable organisms. Mullus barbatus reflects the influence of local sources, and is therefore a useful bioindicator for organic pollutants. Despite some scattering of the results, concentrations are in general of the same order of magnitude for juvenile and adult specimens, although the pollutants considered exhibit different biological fates. Hydrocarbons are accumulated primarily in liver, whereas organochlorinated compounds are accumulated in gonads. Liver and muscle contents could reflect acute and chronic pollutants inputs respectively. The accumulation in muscle is more important for aromatic and chlorinated hydrocarbons than for the saturated ones, which are probably metabolized in the liver.

Phenol removal from aqueous solution by adsorption and ion exchange mechanisms onto polymeric resins

The removal of phenol from aqueous solution was evaluated by using a nonfunctionalized hyper-cross-linked polymer Macronet MN200 and two ion exchange resins, Dowex XZ (strong anion exchange resin) and AuRIX 100 (weak anion exchange). Equilibrium experimental data were fitted to the Langmuir and Freundlich isotherms at different pHs. The Langmuir model describes successfully the phenol removal onto the three resins. The extent of the phenol adsorption was affected by the pH of the solution; thus, the nonfunctionalized resin reported the maximum loading adsorption under acidic conditions, where the molecular phenol form predominates. In contrast both ion exchange resins reported the maximum removal under alkaline conditions where the phenolate may be removed by a combined effect of both adsorption and ion exchange mechanisms. A theoretical model proposed in the literature was used to fit the experimental data and a double contribution was observed from the parameters obtained by the model. Kinetic experiments under different initial phenol concentrations and under the best pH conditions observed in the equilibrium experiments were performed. Two different models were used to define the controlling mechanism of the overall adsorption process: the homogeneous particle diffusion model and the shell progressive model fit the kinetic experimental data and determined the resin phase mechanism as the rate-limiting diffusion for the phenol removal. Resins charged after the kinetic experiments were further eluted by different methods. Desorption of nonfunctionalized resin was achieved by using the solution (50% v/v) of methanol/water with a recovery close to 90%. In the case of the ion exchange resins the desorption process was performed at different pHs and considering the effect of the competitive ion Cl-. The desorption processes were controlled by the ion exchange mechanism for Dowex XZ and AuRIX 100 resins; thus, no significant effect for the addition of Cl- under acidic conditions was observed, while under alkaline conditions the total recovery increased, specially for Dowex XZ resin.

Identification of organophosphorus insecticides and their hydrolysis products by liquid chromatography in combination with UV and thermospray-mass spectrometric detection

Liquid chromatography with ultraviolet detection (LC-UV) and positive and negative ion mode (PI and NI, respectively) thermospray LC-mass spectrometry (LC-MS) were used for the analysis of the organophosphorus pesticides azinphos-methyl, diazinon and parathion-methyl and their corresponding breakdown products obtained after basic hydrolysis (pH 7-11). LC analysis was performed in the reversed-phase mode using methanol-water (80:20) or methanol-water (70:30) + 0.1 M ammonium acetate for LC-UV or LC-MS, respectively. By employing NI thermospray LC-MS the identification of p-nitrophenol, showing the [2M-H]- ion as the base peak, was feasible and confirmed the LC-UV chromatogram at 220 nm. When the PI mode was used, [M + NH4]+ and [M + H]+ ions were obtained as base peaks for azinphos-methyl and diazinon, respectively. The degradation rates varied from diazinon, which showed no degradation during a period of ten days, to azinphos-methyl and parathion-methyl, for which degradation occurred rapidly when the pH was increased from 7 to 11.

Capillary electrophoretic determination of cyanide leaching solutions from automobile catalytic converters

A capillary electrophoresis (CE) method to determine metal-cyano complexes from leaching solutions of automobile catalytic converters has been developed. The separation and detection conditions have been optimized and analysis times up to 20 min and metal detection limits in the ppb range have been obtained. The CE analysis of leaching solutions from different converters allowed the determination of Fe(II)-, Cu(I)-, Ni(II)-, Pd(II)- and Pt(II)-cyano complexes and NO - 3 . On the other hand, adsorption onto activated carbon is used as a concentration process for precious metal-cyano complexes and as a process of pollutant removal. The adsorption kinetics of the compounds of interest have been studied by means of the developed CE method. The results obtained by CE have been compared with inductively coupled plasma in order to validate this newly developed method.

Determination of gold(I) and silver(I) cyanide in ores by capillary zone electrophoresis

Abstract Capillary zone electrophoresis (CZE) with on-column UV detection at 214 nm was used to detect and determine gold(I) and silver(I) cyanide complexes in alkaline cyanide solution. Under an applied voltage of 25 kV, dicyanoaurate(I) and dicyanoargentate(I) were separated in less than 6 min. Carbonate buffer was used and the separation of both anions was achieved using an anodic injection and cathodic detection scheme. The method was applied to the determination of gold and silver cyanide in ore samples. Quantitative analysis was possible and good agreement between CZE and atomic absorption spectrometric results was obtained.

Assessment of petroleum pollution in a Mexican river by molecular markers and carbon isotope ratios

Abstract Sediments sampled within bed of the Coatzacoalcos river, Veracruz, Mexico were used as geo-accumulators for the assessment of the status of petroleum pollution in the Coatzacoalcos river. Stable carbon isotope ratios and the composition of aliphatic and aromatic hydrocarbons were determined in order to evaluate the importance of the petrogenic inputs as well as to ascertain their spatial distribution. Molecular markers, namely acyclic isoprenoid hydrocarbons, steranes and hopanes were studied for source identification. As result, high levels of petroleum were found in the whole studied area, with no defined spatial trends, corresponding to an overall pollution by the same type of crude oil products.

Comparative study of high-performance liquid chromatography and micellar electrokinetic capillary chromatography applied to the analysis of different mixtures of pesticides

High-performance liquid chromatography (HPLC) and micellar electrokinetic capillary chromatography (MECC) methods for the determination of different pesticides mixtures have been developed. These mixtures include triazine, phenylurea, phenoxyalkyl acid, carbamate and organophosphorous pesticides that have been selected because their use in different combinations in commercial formulations. The best results have been obtained by using mobile phase gradients in HPLC and by working with n-alcohols as mobile phase modifiers in MECC. When the quality parameters of both methods have been compared, it was observed that they are not sensitive enough for environmental analysis. In this sense two different concentration methodologies, off-line solid extraction by using Carbopack columns and a special injection MECC method, have been studied to enhance sensitivity. Off-line solid extraction can be used for both HPLC and MECC methodologies and permits to detect low ppb levels of individual pesticides. Special injection methods applied to the MECC system provides a 200-fold sensitivity improvement for the ionic pesticides.

Accumulation and distribution of hydrocarbons, polychlorobyphenyls, and DDT in tissues of three species of anatidae from the Ebro Delta (Spain)

Five tissues (breast muscle, liver, kidney, adipose tissue and medulla) of three species of Anatidae (Netta, rufina, Anas crecca andAnas clypeata) from the Ebro Delta have been analyzed for ∑DDT, polychlorobyphenyls (PCBs) and biogenic and petrogenic hydrocarbons, with the aim of obtaining information on the biodynamics of these compounds in wildbirds.Polychlorobiphenyls and DDTs show different accumulation patterns, probably related to their different lipophilicity and the lipid composition of each tissue. Metabolic, less polar, lipids (adipose tissue) accumulate preferentially PCBs, whereas the structural ones (e.g., medulla) contain relatively more ∑DDT. The overall physiological dynamics of the species play an important role. Thus, the more zoophagous (Anas sp.) are more heavily contaminated and the liver contains relatively more PCBs than ∑DDT, contrary to the phytophagousNetta rufina. Mobilization of PCBs from the adipose tissue to the breast muscle is also related to the migratory behavior of the species (higher inAnas sp.).Petroleum hydrocarbons were below the detection limit in all species, but a large variety of biogenic components indicative of the feeding habits of the organisms were identified for the first time, particularly in the liver. Thus, algal indicators were abundant inNetta rufina, whereas insect and higher plant lipids were identified inAnas clypeata.

Steroid alcohols and ketones in coastal waters of the western Mediterranean: Sources and seasonal variability

A total of 36 sterols (stenols and stanols) and 17 sterones (stenones and stanones) were identified in the particulate organic matter (POM) of surface seawater from the western Mediterranean in the vicinity of the Ebro river mouth. Concentrations of particulate sterols ranged from 0.6 to 4.8 μg l−1 in the delta bays and from 0.07 to 1.1 μg l−1 in the open sea transects. Sterones were present at one order of magnitude lower. Both the concentrations and the compositions of steroidal components were seasonally dependent, reflecting changes in the phytoplanktonic population, in the sense that diatom biomarkers (Δ5, Δ5,22 and Δ5,24(28)-stenols, and Δ4-stenones) were the major components during marine fertile periods (spring and fall), whereas dinoflagellate markers (4α-methylstanols and 4α-methylstanones) predominated during the lowest productivity periods (summer and winter). Based on spectral data 4α-methylcholest-7-en-3β-ol, 4α,23,24-trimethylcholest-7-en-3β-ol, 4α-methyl-5β(H)-cholestan-3β-ol and 24-methylcholesta-4,24 (28)-dien-3-one were identified for the first time in seawater particles. Some of these are proposed as biomarkers of the dinoflagellate contribution to POM in seawater. In addition, the occurrence of red algae in the river bays in spring is suggested by steroidal biomarkers (i.e. cholesta-5,24(25)-dien-3β-ol). Fecal pollution was detected, according to the 5β-steroids distribution, near the Ebro river mouth and Tarragona.