Lílian Karla de Oliveira

Adsorption/desorption of arsenic by tropical peat: influence of organic matter, iron and aluminium

The objective of this work was to investigate the interaction of arsenic species (As(III) and As(V)) with tropical peat. Peat samples collected in Brazil were characterized using elemental analysis and 13C NMR. Adsorption experiments were performed using different concentrations of As with peat in natura and enriched with Fe or Al, at three different pH levels. Peat samples, in natura or enriched with metals, were analysed before and after adsorption processes using Fourier transform infrared spectroscopy (FTIR) spectroscopy. The adsorption kinetics was evaluated, and the data were fitted using the Langmuir and Freundlich models. The results showed that interaction between As and peat was dependent on the levels of organic matter (OM) and the metals (Fe and Al). As(III) was not adsorbed by in natura peat or Al-enriched peat, although small amounts of As(III) were adsorbed by Fe-enriched peat. Adsorption of As(V) by the different peat samples ranged from 21.3 to 52.7 μg g−1. The best fit to the results was obtained using the pseudo-second-order kinetic model, and the adsorption of As(V) could be described by the Freundlich isotherm model. The results showed that Fe-enriched peat was most effective in immobilizing As(V). FTIR analysis revealed the formation of ternary complexes involving As(V) and peat enriched with metals, suggesting that As(V) was associated with Al or Fe-OM complexes by metal bridging.

Adsorption and release of micronutrients by humin extracted from peat samples

Instituto de Quimica de Araraquara Universidade Estadual Paulista (UNESP), 14800-900 Araraquara-SP

Characterization of the interactions between endocrine disruptors and aquatic humic substances from tropical rivers

Interactions between two endocrine disruptors (ED) and aquatic humic substances (AHS) from tropical rivers were studied using an ultrafiltration system equipped with a 1 kDa cut-off cellulose membrane to separate free ED from the fraction bound in the AHS. Quantification of 17α-ethynylestradiol and bisphenol A was performed using gas chromatography-mass spectrometry (GC-MS). The times required for establishment of equilibrium between the AHS and the ED were ca. 30 min, and complexation capacities for 17α-ethynylestradiol and bisphenol A were 18.53 and 2.07 mg g-1 TOC, respectively. The greater interaction of AHS with 17α-ethynylestradiol, compared to bisphenol A, was due to the presence of hydrogen in the structure of 17α-ethynylestradiol, which could interact with ionized oxygenated groups of the AHS. The results indicate that AHS can strongly influence the transport and reactivity of endocrine disruptors in aquatic systems.

Enrichment of tropical peat with micronutrients for agricultural applications: evaluation of adsorption and desorption processes

O objetivo deste trabalho foi avaliar os processos de adsorcao e dessorcao de micronutrientes em amostras de turfas tropicais visando uma possivel aplicacao em solos. Para isso, experimentos de adsorcao foram estudados em diferentes valores de pH e a partir de solucao metalica multielementar e elementar. As capacidades de adsorcao maximas ocorreram em pH 6,0 e a ordem de afinidade observada em geral foi: Cu > Fe > Co > Ni > Zn = Mn. A liberacao dos micronutrientes foi avaliada sob diferentes valores de pH em meio aquoso, e posteriormente, em solo e planta. Os experimentos de liberacao mostraram que os micronutrientes sao liberados preferencialmente em pH 6,0 e na seguinte ordem: Fe > Zn > Mn > Co = Ni > Cu. A liberacao dos micronutrientes para o solo e acompanhada pela sorcao dos mesmos pela planta. Desta maneira, a aplicacao de turfas tropicais enriquecidas com micronutrientes pode contribuir para uma maior produtividade agricola uma vez que a liberacao dos micronutrientes mostrou-se eficiente no desenvolvimento das plantas. The objective of this work was to evaluate the adsorption and desorption of micronutrients in tropical peats, from the perspective of potential agricultural applications. Adsorption experiments were performed at different pH values, using solutions containing individual and multiple metal ions. Maximum adsorption capacity occurred at pH 6.0, and the order of affinity was Cu > Fe > Co > Ni > Zn = Mn. Release of the micronutrients was evaluated at different pH values, using an aqueous medium as well as soil and plants. Release of the micronutrients was most efficient at pH 6.0, and followed the order: Fe > Zn > Mn > Co = Ni > Cu. Micronutrient release to the soil was accompanied by uptake by the plant. The use of tropical peat enriched with micronutrients could contribute to improved agricultural productivity, since the release profile of the micronutrients can effectively stimulate plant growth.

Síntese de acetato de celulose a partir da palha de feijão utilizando N-bromossuccinimida (NBS) como catalisador

In this work, cellulose from beans straw was used to produce a more hydrophobic material (cellulose acetate) for use as oil absorbent. Acetic anhydride was used in the reactions with two catalysts, pyridine (PY) and N-bromosuccinimide (NBS). The materials produced were characterized by infrared spectroscopy, scanning electron microscopy, X-ray diffraction and elemental analysis. NBS proved more efficient than PY, with the resulting materials containing higher number of acetate groups, being more hydrophobic and with higher capacity to absorb soybean oil.

Removal of the emerging contaminant bisphenol A by an ureasil–PEO hybrid membrane: experimental study and molecular dynamic simulation

AbstractThis work reports the use of a cross-linked ureasil–PEO hybrid matrix (designated PEO800) as an efficient adsorbent to retain the emerging contaminant bisphenol A (BPA) from an aqueous medium. The in-deep experimental and theoretical results provide information about the interactions between PEO800 and BPA. The in situ UV-vis spectroscopy data and the pseudo-first order, pseudo-second order, Elovich, and Morris–Webber intraparticle diffusion models allowed us to propose a three-step mechanism for the adsorption of BPA onto PEO800. The results indicate that the pseudo-first-order kinetic model effectively describes the adsorption of BPA onto PEO800. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy confirmed the interaction of PEO800 with BPA, showing an alteration in the chemical environment of the polymer ether oxygen atoms present in the hybrid matrix. The molecular dynamic simulation provides further evidence that the BPA molecules interact preferentially with PEO. The amount of desorbed BPA depended on the pH and solvent used in the assays. This work provides new opportunities for using the hydrophilic ureasil–PEO matrix which has demonstrated its abilities in being a fast and easy alternative to successfully removing organic contaminants from aqueous mediums and therefore having potential applications in water remediation. Graphical abstract

Desenvolvimento de materiais adsorventes de óleos a partir de resíduos do beneficiamento do café e sua aplicação na ração para aves

The aim of this work was chemically modify lignocellulosic materials (processing coffee waste-parchment) in order to obtain a more hydrophobic material, test it as to its oil adsorbent capacity and use it in the formulation of poultry feed. The residues were analyzed for its chemical-bromatologic composition and subsequently acetylated with acetic anhydride using different concentrations of N-bromosuccinimide (as catalyst) for 4 hours at 120 ° C. Analysis of the parchment indicates high levels of fiber. The acetylation of this material promotes mass gain for all samples studied. An increase in the oil adsorption capacity was observed for all the modified materials, proving the hydrophobization. Acetylated material with adsorbed oil was called OSoL (solid oil) and replaced soybean oil in poultry diet. In metabolic experiments we adopted the method of forced feeding and determined the true metabolizable energy values, true metabolizable energy corrected for nitrogen, digestibility of dry matter, digestibility of crude protein and metabolizable energy coefficient of metabolizibility. The treatments were similar statistically; therefore, the inclusion of OSOL in poultry diet is viable.