No abstract

A B S T R A C TEndocrine disrupting determination at low concentration levels comprises one of the most important targets in environmental analytical chemistry. In spite of inherent high sensitivities obtained for HPLC, these techniques have some limitations depending on the contaminants. As a result, interest in preconcentration using solid-phase extraction (SPE) still continues increasingly for endocrine disrupting determinations by HPLC due to the high accuracy of this method. In this work, we evaluated three different adsorbents in preconcentration of endocrine disruptors in three different categories: pharmaceuticals (sulphamethoxazole, trimethoprim and diclofenac), hormones (estrone, 17β-estradiolacetate and 17β-estradiol) and plastic materials (bisphenol A) in multicomponent aqueous solution using the combination SPE -HPLC. The adsorbents investigated were such as modified silica (octadecylsilane)-DSC-18 (Supelco) and two polymers, a divinylbenzene-N-vinilpirolidona -Oasis ® HLB (Waters) and a styrene-divinylbenzene modified with butyrolactone-Strata-X™ (Phenomenex). The parameters selected to evaluate the best adsorbent were sample loaded, breakthrough volume, recovery and adsorption capacity. The results showed that the polymeric sorbents Oasis and Strata presented good separation and selective ability, then the most efficient sorbent for the described test was applied to the determination of endocrine disruptor (ED) in a wastewater real sample. Almost all endocrine disruptors studied in the present work were found and quantified in the effluent sample, suggesting the selected cartridge could be useful for preconcentration technique of endocrine disruptors in environmental analytical applications. Correlation analysis identified the adsorption parameters which had the most influence in efficiency of SPE adsorbents, such as initial ED concentration, breakthrough volume and recovery.

No abstract

-Batch adsorption experiments were carried out in order to evaluate the maximum adsorption conditions of pharmaceutical Trimethoprim from real wastewater on pillared clay using a full factorial design. The five factors were temperature, the initial pH of the solution, initial concentration, agitation and dosage of adsorbent. The optimization of the factors to obtain maximum adsorption was carried out by incorporating effect plots, normal probability plots, interaction plots, analysis of variance (ANOVA), Pareto charts, surface plots, and contour plots. The statistical design experiments, designed to reduce the total number of experiments required, indicated that, within the selected conditions, all the parameters influenced at a significance level of 5%. In addition, some of the possible interactions between these parameters also influenced the adsorption process, especially those that were of first order. A regression model was suggested and fitted the experimental data very well.

-SnO 2 pillared montmorillonite clay was prepared and examined as adsorbent in the adsorption of endocrine disruptors compounds (EDCs) and compared with its starting material. The pillared samples showed a considerable increase in EDCs adsorption capacity in comparison to the natural clay mineral. This effect can be related to the textural and structural changes produced during the pillaring process. Consequently, Tin pillared clays could be the new material to be used in studied environmental process. Kinetics studies indicated that the multicomponent adsorption equilibrium was reached within 1 h and followed pseudo-second-order kinetics. The Langmuir, Freundlich, Redlich-Peterson and Temkin models were used to evaluate the EDCs adsorption capacity by pillared clay. The Freundlich model was found to be suitable for all compounds in a multicomponent system.