Resumo: Neste estudo a celulose obtida da palha de feijão foi utilizada para produzir um material hidrofóbico (acetato de celulose) para ser avaliado como absorvente de óleo. Nas reações de acetilação foram utilizados anidrido acético e dois catalisadores, a piridina (PY) e N-bromossuccinimida (NBS). Os materiais produzidos foram caracterizados por espectroscopia na região do infravermelho médio, microscopia eletrônica de varredura, difratometria de raios-X e análise elementar. O NBS mostrou-se mais eficiente que a PY e, seu uso resultou em materiais com maiores quantidades de grupos acetatos, mais hidrofóbicos e com maiores capacidades de absorção de óleo de soja. Palavras-chave: Acetato de celulose, N-bromosuccinimida, acetilação, absorção de óleo.Abstract: 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.

This work reports on the preparation of cross-linked amine-alcohol-silicate hybrid matrixes with tunable hydrophilic/hydrophobic domains from end-group functionalized polyetheramines (PEO and PPO) and 3glycidoxypropyl-trimethoxysilane (GPMS) by the sol-gel route as efficient adsorbents for retaining anionic species; the resulting hybrid matrixes were designated as PEO500-GPMS and PPO400-GPMS, respectively. This work also discusses how the nature and swelling properties of the polyethers PEO and PPO, investigated by small-angle X-ray scattering (SAXS) and in situ SAXS measurements, affect the way PEO500-GPMS and PPO400-GPMS interact with the anionic dye, Rose Bengal (RB). The use of polyetheramines of different polyether nature afforded hybrid matrixes with distinct capacity and mechanisms of anionic species adsorption. Compared with the literature and PPO400-GPMS, PEO500-GPMS had higher RB adsorption capacity, which indicated that the latter matrix is a highly efficient adsorbent and good candidate in the field of anion binding for applications in water treatment. The in situ UV-vis spectroscopy results and the pseudo-first order, pseudo-second order, and Morris-Weber intraparticle diffusion models allowed us to propose a three-step mechanism for RB adsorption onto PEO500-GPMS. The first step is short-range diffusion of RB molecules to the external surface of PEO500-GPMS, followed by water uptake (hydrogel behavior) by the matrix which accelerated the adsorption and diffusion process, and finally a dynamic equilibrium stage leading to the higher adsorption capacity. The thermodynamic studies provided information about the inherent energetic changes taking place in PEO500-GPMS and PPO400-GPMS during RB adsorption. The use of a distribution coefficient (D) helped to define the strength of the interaction between the hybrid matrixes and the dye in water. Comparative DSC studies showed that the presence of RB in the hybrid matrixes increased the rigidity of the polymeric backbone. We demonstrated that hybrid xerogels efficiently remove a series of anionic dyes such as Congo Red, Ponceau S, Indigo Carmine, Eosin Y, Brilliant Green and Fluorescein. The excellent water uptake, swelling behavior and the impressive anionic binding ability of PEO500-GPMS make it a highly efficient adsorbent for water purification and treatment. ; Fax: +55 16 37118961; Tel: +55 16 37118961 † Electronic supplementary information (ESI) available: In situ UV-vis additional spectra, adsorption isotherms, and thermodynamic analysis. See Scheme 2 Chemical structure of the (a) PEO500-GPMS and (b) PPO400-GPMS hybrids with the possible interaction sites: ether-type oxygen (blue), amine (red), oxygen-type alcohol (green), and (c) molecular structure of Rose Bengal dye. J. Mater. Chem. A This journal is

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.

Humic acids (HAs) are ubiquitous macromolecules in the environment. Due to their high contents of oxygenated functional groups, they can interact with contaminants present in the natural environment and therefore influence the behavior of pollutants. However, a pH of 2 or lower is required to maintain HAs in the solid form. To increase the stability of HAs and their capacity to bind to contaminants, this work proposes the development of new hybrid materials based on alkoxysilanes and HAs for environmental applications such as dye adsorption. Three different materials with new functional groups were prepared by employing the following alkoxysilanes: tetraethyl orthosilicate, (3-aminopropyl)triethoxysilane, and N-[3-(trimethoxylsilyl)propyl]ethylenediamine. The final materials were denoted HWA, HOA, and HTA, respectively, and they were characterized by elemental analysis, diffuse reflectance Fourier-transform infrared spectroscopy (DRIFT), small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and N2 gas-volumetric adsorption. The point of zero charge (pzc) and stability of these materials were also determined. Their selectivity was evaluated in adsorption experiments performed with two different charged dyes in aqueous medium, namely anionic rose bengal (RB) and cationic methylene blue (MB). The elemental, DRIFT, SAXS, SEM, and textural analyses confirmed the presence of a combination of the features of HAs and alkoxysilanes. The pzc results showed that the new materials displayed different characteristics and affinities. All the materials were stable in aqueous solution up to pH 10. For MB, the percentage removal values obtained by using HWA, HOA, and HTA were 98, 85, and 67%, respectively. As for RB, the percentage removal values were 19, 18, and 44% for HWA, HOA, and HTA, respectively. These hybrid materials have potential use as adsorbents for the removal of cationic or anionic species and could be viable alternatives to remove various substances present as contaminants in natural environments.

The mobility and bioavailability of arsenic (As) are strongly controlled by adsorption/precipitation processes involving metal oxides. However, the organic matter present in the environment, in combination with these oxides, can also play an important role in the cycle of arsenic. This work concerns the interaction between As and two samples of aquatic humic substances (AHS) from tropical rivers. The AHS were extracted as proposed by IHSS, and were characterized by (13)C NMR. The experiments were conducted with the AHS in natura and enriched with metal cations, with different concentrations of As, and complexation capacity was evaluated at three different pH levels (5.0, 7.0, and 9.0). The AHS samples showed similar chemical compositions. The results suggested that there was no interaction between As(III) and AHS in natura or enriched with Al. Low concentrations of As(V) were bound to AHS in natura. For As(III), the complexation capacity of the AHS enriched with Fe was approximately 48 μmol per g of C, while the values for As(V) were in the range 69-80 μmol per grams of C. Fluorescence spectra showed that changes in Eh affected the complexation reactions of As(V) species with AHS.