Adsorption of two pesticides on a clay surface: a theoretical study

The contamination of water resources with many organic xenobiotic compounds poses a challenge to environmental sciences and technologies [1]. Although in many cases these contaminants are present only in small concentrations, the large variety of such compounds (some of which are classified as priority pollutants) is a matter of concern. Adsorption, alone or as part of a more complex water or wastewater treatment process, has been seen as playing a very important role in the removal of many of these pollutants [2]. In this regard, the choice of adsorbent materials is crucial, which requires an understanding of the details involved in the adsorption of more or less complex organic molecules by a variety of surfaces of different types. In addition to laboratory studies, computational studies may be valuable in this study [3]. MCPA (2-methyl-4-chlorophenoxyacetic acid, a herbicide) and Clofibric acid (2-(4-chlorophenoxy)-2-methylpropanoic, the metabolite of a pharmaceutical, clofibrate, and also a herbicide) are two phenoxy acids that differ only slightly in their structures. However, a quite distinct behavior in adsorption phenomena on clay materials has been observed in past studies [4]. By relating those differences with the molecules' structural features through atomistic computational studies, some insight may be gained into the respective adsorption processes of this type of compounds. In the present work quantum chemical calculations at density functional theory level have been performed to study the adsorption of MCPA and Clofibric acid by a clay surface model. Since hydration plays an important role for the adsorption process of these species, solvent effects were considered by inclusion of water molecules explicitly into the quantum chemical calculations. The deprotonated negatively charged species were found to strongly interact with the surface and the distinct behavior of both species upon adsorption was compared with experimental evidences

In Vitro Methods for Specific IgE Detection on Cow’s Milk Allergy

Background: A new method for determining serum specific IgE (IMMULITE“ 2000 3gAllergy) has recently become available. Objective: To evaluate the clinical performance of IMMULITE 2000 in the diagnosis of cow’s milk allergy compared with that of UniCAP“. Additionally, we verified the behavior of both methods at two diagnostic decision points proposed by other authors. Methods: The study population consisted of 31 children with cow’s milk allergy (group A) and a control group of 19 atopic children without food allergy(group B). A blood sample from each child was tested using both methods and the results were compared. Results: In group A, the values for cow’s milk IgE ranged from 0.35 kU/L (the lowest common detection limit) to above 100 kU/L. In group B, the values were less than 1.1 kU/L for IMMULITE 2000 and less than 1.6 kU/L for UniCAP. An agreement of 90 % in IgE classes was obtained. Both methods demonstrated exactly the same diagnostic performance(sensitivity: 100 %; specificity: 78.9 %; negative predictive value: 100%; positive predictive value: 84.6%;efficiency: 90.2 %). The evaluation of the two methods at the two different decision points proposed in the literature showed a better positive predictive value with UniCAP, but we obtained equivalent performance with IMMULITE 2000 by choosing higher cutoff values. Conclusions: We conclude that IMMULITE 2000 is as effective as UniCAP in the diagnosis of cow’s milk allergy. Both methods can be used to obtain site-specific decision points that are population, age and disease dependent

Caracterização ambiental dos componentes estruturais de duas regiões do bioma Mata Atlântica no Estado do Paraná.

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Conjugated linoleic acid reduces permeability and fluidity of adipose plasma membranes from obese Zucker rats

NOTICE: this is the author’s version of a work that was accepted for publication in Biochemical and Biophysical Research Communications. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Biochemical and Biophysical Research Communications. July 2010; 398 (2): 199-204.Conjugated linoleic acid (CLA) is a dietary fatty acid frequently used as a body fat reducing agent whose effects upon cell membranes and cellular function remain unknown. Obese Zucker rats were fed atherogenic diets containing saturated fats of vegetable or animal origin with or without 1% CLA, as a mixture of cis(c)9,trans(t)11 and t10,c12 isomers. Plasma membrane vesicles obtained from visceral adi- pose tissue were used to assess the effectiveness of dietary fat and CLA membrane incorporation and its outcome on fluidity and permeability to water and glycerol. A significant decrease in adipose membrane fluidity was correlated with the changes observed in permeability, which seem to be caused by the incor- poration of the t10,c12 CLA isomer into membrane phospholipids. These results indicate that CLA supple- mentation in obese Zucker rats fed saturated and cholesterol rich diets reduces the fluidity and permeability of adipose membranes, therefore not supporting CLA as a body fat reducing agent through membrane fluidification in obese fat consumers

A DFT study on the adsorption of benzodiazepines to vermiculite surfaces

Widespread use of pharmaceuticals such as benzodiazepines has been resulting over the last decades in the dissemination of residues of these compounds in the environment, and such fact has been raising increasing concern. The generally low efficiencies of conventional wastewater treatment processes for the removal of this type of pollutants demands for the development of alternative or complementary water and wastewater treatment technologies, among which adsorption processes have been gaining popularity, provided that cheap efficient adsorbents are found. Clay materials have been one of the popular choices in this regard. In the present study, quantumchemical calculations have been performed by periodic DFT using the projector augmented-wave (PAW) method to characterize the interactions of two benzodiazepine molecules, alprazolam and diazepam, with a surface of clay mineral, vermiculite. It was observed that both molecules interact strongly with the vermiculite surface, both through a water-bridge binding and by cation-bridge provided by the exchangeable Mg2+ cations of the vermiculite surface. The results point to an interesting potential of vermiculite to be used efficiently as filter medium to remove these pollutants from water and wastewater

A DFT Study on the Adsorption of Benzodiazepines to Clay Surfaces

Benzodiazepines (BDZ) belong to the group of psychiatric substances which act on the central nervous system, having anxiolytic, sedative and hypnotic effects and is one of the most prescribed groups of pharmaceuticals throughout the world. These compounds are not exclusively used for human therapeutics, their prescription is also common in veterinary treatments for anxiolytic and appetite stimulation effects. Nowadays, there are several benzodiazepines under international control for therapeutic use. The widespread use of these compounds doesn’t come without a cost and trace levels of it can now be found disseminated on the environment, what is a matter of ecological concern. In fact, over the last decade, there has been a significant number of studies reporting the occurrence of BDZ in environmental matrices, namely in wastewater treatment plants influents and effluents, surface waters and drinking waters . Some of the more frequently detected BDZ include alprazolam, diazepam, lorazepam and oxazepam . The main reason for the ubiquitous presence of BDZ in the environment is associated not only with the large use but also the generally low efficiency of conventional biological wastewater treatment to remove these pharmaceutical residues. It has been suggested that this inefficiency is due to the halogenated structure of these compounds that significantly reduces their susceptibility to biodegradation . Adsorption processes are the most promising and cheap alternative for removal of these kind of organic xenobiotic from wastewaters. In recent years, inexpensive widely available materials have been investigated for the selection of efficient adsorbents that can make adsorption processes an attractive solution at reasonable costs. Among some of the adsorbents studied, clay-based materials have received some attention due to their interesting properties such as the high cation exchange capacity, swelling properties and high specific surface areas. In particular for the treatment of wastewaters, these materials can overcome the limitations of biological processes, as used in conventional wastewater treatment. A better understanding of the interactions of these organic molecules with clay minerals may thus allow a more judicious selection of materials for water/wastewater treatment filters that present significant enhancements in the removal of BDZ. In this work, electronic structure calculations based on the density functional theory (DFT) are presented on the interaction of two BDZ molecules (diazepam and alprazolam) with a periodic model surface of the vermiculite mineral. Geometry changes of the molecules upon adsorption were compared and the interaction energies with the surfaces were determined for a few different molecular orientations in order to understand the way these molecules interact with the clay surface and the essential factor governing the adsorption processes

Removal of the Antibiotic Sulfamethoxazole by “Green” Clay Sorbents

Contamination of water resources with pharmaceuticals has been one of the top concerns of environmental sciences in the latest years [1, 2], the matter having received very significant media coverage recently [2, 3]. Antibiotics in particular have been gathering considerable attention and are amongst the most serious worries due to the development of antibiotic resistant bacteria as result of prolonged exposure [1, 2, 3]. In particular, antimicrobials and their metabolites are being detected in significant amounts in water supplies, and although no evidence exists that human health is affected by minute doses of antibiotics over long periods of time, changes have been observed in ecosystem functions [3,4]. In addition to antimicrobial resistance, other effects have been observed such as a delay in cell growth of bacteria, limited denitrification, and shifts in community composition [5]. Sulfamethoxazole (SMX), a broad-spectrum biostatic sulfanilamide, has become a point of interest because of its prevalence in contaminated wastewaters at concentrations correlated to bacterial resistance and genetic mutations in organisms [3,4,5]. Taking into account the widespread use of sulfonamides and their potential environmental effects, there is importance in developing new technologies for removing SMX and similar compounds from points of discharge. In fact, most wastewater treatment plants are inefficient for the removal of most micropollutants, especially hardly biodegradable organic xenobiotics which are present in wastewaters at low concentrations, as these conventional systems were only designed for removing bulk pollutants. Several advanced technologies have been evaluated as options to treat these contaminants, e.g. advanced oxidative processes or membrane filtration, but despite the sometimes high removal efficiencies attained, these technologies are too expensive to be considered as viable solutions on a large scale. Adsorption, alone or as part of a more complex water or wastewater treatment process, has been seen as playing a very important role in the removal of many organic xenobiotic pollutants [6, 7]. In this regard, the choice of adsorbent materials is crucial. However, pollutants removal efficiency is not the sole selection criterion, as the cost of the materials may provide or preclude economic viability of the water/wastewater treatment system. Therefore, the quest for efficient adsorbents that are widely available, and do not require expensive processing in order to be used (thereby allowing lower production costs) is a very important aspect of research aimed to manage this environmental problem. In this work we present the study of sorption properties of clay materials (LECA and vermiculite) for the removal of SMX from water. The dependence of removal efficiencies on the antibiotic initial concentrations, contact time with the adsorbents and other system/environment conditions was assessed. The two clay materials were compared in terms of their more balanced performance towards the removal of the pharmaceutical tested and the materials are suggested as a useful component of a water or wastewater treatment system designed for the removal of this contaminant (and others of similar type). Vermiculite was shown to be more efficient than LECA in the adsorption of the pharmaceutical and the one with faster kinetics. In other to gain a deeper insight into the characteristics that favor the removal of this compound by mineral surfaces, quantum chemical theoretical calculations were performed to illustrate the type of interactions that are responsible for the preferable adsorption of the compound to the vermiculite surface