The effect of montmorillonite clay in alginate gel beads for polychlorinated biphenyl adsorption: Isothermal and kinetic studies

Beads of alginate montmorillonite have been used as sorbent for polychlorinated biphenyls from aqueous solutions.The structure and the differences between the different beads were established by IR spectroscopy (FT-IR). The adsorption at 25 °C has been studied in a batch system, following its kinetics and assessing adsorbent dose, initial PCB concentrations, and pH effects. The results show that increasing the initial concentration of the PCBs and the adsorption time favored the adsorption. Adsorption isotherm data were modeled using Chapman, Freundlich and Langmuir adsorption isotherms and the appropriate parameters were calculated.Adsorption of trichlorobiphenyls on alginate–montmorillonite beads followed a Freundlich isotherm type model, while adsorption of tetra-, penta-, and hexachlorobiphenyls displayed a sigmoid-shaped (S-type) isotherm fitting the Chapman sigmoidal equation with the highest non-linear R2 values among the three tested models. By comparing the percentage adsorptions using the same number of beads (same volumes), best removals were obtained by using alginate montmorillonite beads.Adsorption of trichlorobiphenyls on alginate–montmorillonite beads followed a Freundlich isotherm type model, while adsorption of tetra-, penta-, and hexachlorobiphenyls displayed a sigmoid-shaped (S-type) isotherm fitting the Chapman sigmoidal equation with the highest non-linear R2 values among the three tested models. By comparing the percentage adsorptions using the same number of beads (same volumes), best removals were obtained by using alginate montmorillonite beads.Adsorption of trichlorobiphenyls on alginate–montmorillonite beads followed a Freundlich isotherm type model, while adsorption of tetra-, penta-, and hexachlorobiphenyls displayed a sigmoid-shaped (S-type) isotherm fitting the Chapman sigmoidal equation with the highest non-linear R2 values among the three tested models. By comparing the percentage adsorptions using the same number of beads (same volumes), best removals were obtained by using alginate montmorillonite beads.Adsorption of trichlorobiphenyls on alginate–montmorillonite beads followed a Freundlich isotherm type model, while adsorption of tetra-, penta-, and hexachlorobiphenyls displayed a sigmoid-shaped (S-type) isotherm fitting the Chapman sigmoidal equation with the highest non-linear R2 values among the three tested models. By comparing the percentage adsorptions using the same number of beads (same volumes), best removals were obtained by using alginate montmorillonite beads. Kinetic models were investigated to determine the mechanism of adsorption showing a best fit for the pseudo second order model (R2 from 0.998 to 0.982. Moreover, to underline the effect of montmorillonite in alginate gel beads, we have compared the isothermal adsorption curves between alginate montmorillonite and alginate beads

Photochemical sample treatment for extracts clean up in PCB analysis from sediments

Sample purification can be considered the most polluting step of the whole analytical process for PCBs determination in sediment samples. The use of photochemical sample treatment represents an alternative methodology for extracts clean up allowing for a reduction of the used amount of organic solvents. The first application of a photochemical sample treatment for the selective removal or reduction of organic substances interfering with PCBs analyses in sediments is reported. The method's efficiency and robustness were compared with currently used chromatographic purification. Quality parameters such as recovery, linearity and reproducibility were studied. The entire procedure was validated by four replicate analysis of certified reference sediment. The quantification limits (LOQ) obtained by us ranged from 1 to 3.1 ng g(-1). The RSD for each congener was below 15\% and recoveries were in the range 40-130\%. Results based on the analysis of real and certified samples showed similar or improved detection thresholds and pointed out the advantages of the photochemical methodology in terms of costs and environmental friendly conditions. (C) 2012 Elsevier B.V. All rights reserved

Formaldehyde and total aldehydes in indoor air of public environments by voltammetry

The proposed method involves active sampling, where a sampling pump is used to pull air through a solution and voltammetric analysis of the obtained solutions. No interferences have been observed. In addition, very little sample preparation is required. Analyses were performed in 19 indoor stations and one in outdoor. Measurements were carried out on University environments: Museum of Chemistry, Zoological Museum, libraries, laboratories, corridors, meeting rooms, photocopying room, machine shop and terrace. Formaldehyde concentrations in analyzed samples ranged from 2.6 to 85 μg m-3 (median = 32 μg m-3), while the sum of others aldehydes ranged from 2 to 25 μg m-3 (median =2.4 μg m-3). In the sample Zoological Museum 2, the sum of other aldehydes was very high (400 μg m-3). The results demonstrated that artificial ventilation is an efficient system to control indoor air pollution caused by aldehydes emissions

Detection of human enteric viruses in water and shellfish samples collected in Sicily

Historical flora and/or vegetation surveys highlight how the small islands of the Ionian coast of Sicily (Bella, Ciclopi islands, Vendicari, Capo Passero), currently protected as Nature Reserves and/or part of the Natura 2000 network have undergone major landscape changes following alterations in anthropogenic pressure. Landscape changes have been more prominent for the islands located in the northern part of the Ionian coast, with the consequence of increasing populations of invasive alien species. In contrast, landscape changes have decreased in the southernmost islands as indicated by the recovery of natural wood vegetation.peer-reviewe