Cr(VI) Sorption from Aqueous Solution: A Review

Hexavalent chromium (Cr(VI)) in water systems is a major hazard for living organisms, including humans. The most popular technology currently used to remove Cr(VI) from polluted water is sorption for its effectiveness, ease of use, low cost and environmental friendliness. The electrostatic interactions between chromium species and the sorbent matrix are the main determinants of Cr(VI) sorption. The pH plays a central role in the process by affecting chromium speciation and the net charge on sorbent surface. In most cases, Cr(VI) sorption is an endothermic process whose kinetics is satisfactorily described by the pseudo second-order model. A critical survey of the recent literature, however, reveals that the thermodynamic and kinetic parameters reported for Cr(VI) sorption are often incorrect and/or erroneously interpreted

ADSORPTION OF SIMAZINE AND BOSCALID ONTO ACID-ACTIVATED NATURAL CLINOPTILOLITE

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Phospholipase C Beta1 (PI-PLCbeta1)/Cyclin D3/protein Kinase C (PKC) Alpha Signaling Modulation During Iron-Induced Oxidative Stress in Myelodysplastic Syndromes (MDS)

MDS are characterized by anemia and transfusion requirements. Transfused patients frequently show iron overload that negatively affects hematopoiesis. Iron chelation therapy can be effective in these MDS cases, but the molecular consequences of this treatment need to be further investigated. That is why we studied the molecular features of iron effect and Deferasirox therapy on PI-PLCbeta1 inositide signaling, using hematopoietic cells and MDS samples. At baseline, MDS patients showing a positive response after iron chelation therapy displayed higher levels of PI-PLCbeta1/Cyclin D3/PKCalpha expression. During treatment, these responder patients, as well as hematopoietic cells treated with FeCl(3)and Deferasirox, showed a specific reduction of PI-PLCbeta1/Cyclin D3/PKCalpha expression, indicating that this signaling pathway is targeted by Deferasirox. The treatment was also able to specifically decrease the production of ROS. This effect correlated with a reduction of IL-1A and IL-2, as well as Akt/mTOR phosphorylation. In contrast, cells exposed only to FeCl(3)and cells from MDS patients refractory to Deferasirox showed a specific increase of ROS and PI-PLCbeta1/Cyclin D3/PKCalpha expression. All in all, our data show that PI-PLCbeta1 signaling is a target for iron-induced oxidative stress and suggest that baseline PI-PLCbeta1 quantification could predict iron chelation therapy response in MDS

Foreword to the Special Issue on Sorption of Environmental Pollutants: Thermodynamic and Kinetic Aspects

Although new technologies are continuously proposed for water pollutant removal, sorption is still a very effective process used today for this purpose, largely due to its relatively low cost, tunability, and ease of use [...

Common mistakes in the analysis of thermodynamic and kinetic data appearing in the environmental adsorption literature

For decades, adsorption has attracted the attention of many researchers worldwide, resulting in the publication of a considerable number of adsorption studies, especially recently focused on the application of adsorptive removal of pollutants from aqueous solution. Here we discuss some incorrect results and statements frequently found in the scientific environmental adsorption literature. In particular, we focus on the thermodynamic and kinetic aspects of the adsorption process, including erroneous calculation of the equilibrium constant, inaccurate calculation of ΔH° and ΔS°, mismatch between selected isotherm models and isosteric heat of adsorption, misleading interpretation of the spontaneity of a process, erroneous identification of the best-fitting kinetic model [1-3]

Identification of stationary sources of air pollutants by concentration statistical analysis

The atmospheric concentrations of benzene, toluene, ethylbenzene and isomeric xylenes (BTEX) in a medium-sized town (S. Maria Capua Vetere, about 32 000 inhabitants, Southern Italy) have been determined during working days and weekends in 2006. The procedure used was 24 h passive adsorption by samplers distributed throughout the town followed by GC/MS analysis. On a yearly base, the arithmetic mean benzene concentrations were above the limit required by the 2000/69/CE European Directive. The Pearson correlation coefficients of the 24 h geometric mean BTEX concentrations were indicative of stationary sources of toluene located in a well circumscribed area of the urban territory, active only during the working days and not officially recognized. The results highlight the effectiveness of the statistical approach used in this study for the identification of pollutant sources. © 2008 Elsevier Ltd. All rights reserved.The atmospheric concentrations of benzene, toluene, ethylbenzene and isomeric xylenes (BTEX) in a medium-sized town (S. Maria Capua Vetere. about 32000 inhabitants, Southern Italy) have been determined during working days and weekends in 2006. The procedure used was 24 h passive adsorption by samplers distributed throughout the town followed by GC/MS analysis. On a yearly base, the arithmetic mean benzene concentrations were above the limit required by the 2000/69/CE European Directive. The Pearson correlation coefficients of the 24 h geometric mean BTEX concentrations were indicative of stationary sources of toluene located in a well circumscribed area of the urban territory, active only during the working days and not officially recognized. The results highlight the effectiveness of the statistical approach used in this study for the identification of pollutant sources. (C) 2008 Elsevier Ltd. All rights reserved

Catalytic effect of dissolved humic acids on the chemical degradation of phenylurea herbicides

BACKGROUND: Although biodegradation seems to be the main cause of herbicide degradation, abiotic degradation can also be important for chemicals such as phenylureas, which are subject to catalysed soil reactions. The aim of this work is to investigate the effect of dissolved humic acids (HAs), normally present in natural waters, on the hydrolysis of phenylurea herbicides, and it presents a kinetic model that takes into account the role of adsorption. RESULTS: The linearity of the adsorption isotherms indicates that phenylurea-humic acid interaction can be considered in terms of a repartition-like equilibrium of phenylurea between water and HAs. Kinetic experiments show that the degradation rates of phenylureas increase with HA concentration. CONCLUSION: The kinetic equation adopted adequately describes the experimental data trend, allowing the evaluation of the catalytic effect of HAs on the chemical degradation of phenylureas. Carboxyl groups of HAs seem to play a leading role in the catalysis. The kinetic equation derived in this work could be helpful in predicting the persistence of phenylureas and of related compounds in natural water. © 2008 Society of Chemical Industry

Background atmospheric levels of BTEX in a medium-sized city and surrounding area in Southern Italy

Background atmospheric levels of BTEX in the suburb of Caserta (41° 04′ N, 14° 20′ E), a Southern Italian city with about 75,000 inhabitants and a low level of industrialization, were measured during weekdays in 2005. The average annual concentrations (μg m-3) were 8.7 benzene, 26.0 toluene, 6.5 ethylbenzene, 14.4 (m+p)-xylene and 12.5 o-xylene, with higher values during summer. The average daily concentrations of the different BTEX hydrocarbons were strongly correlated (average correlation coefficients = 0.93). The (m+p)xylene/ethylbenzene concentration ratio was relatively low (2.2) and did not show statistically significant seasonal variations. In Naples, a densely populated city on the coast, 25 km from Caserta, the ratio was significantly higher (3.3). Intermediate ratios were recorded in sampling sites located between the two cities. The results suggest that BTEX tend to stagnate in Caserta area, producing relatively high levels with low X/E value, or, alternatively, that they are in greater part produced elsewhere, very likely in Naples, and are transported towards Caserta. To discriminate between these two hypotheses analysis of the patters of local winds is in progress