RESUMO
Physical and thermal treatment was used to inactivate Trametes sp. SC-10 fungus. The resulting biomass was named BTV, characterized by analytical techniques such as SEM, EDX, FTIR, BET, and Barrett-Joyner-Halenda (BJH) model. pH, kinetic, and equilibrium adsorption studies with the Acid Blue 161 (AB-161) dye were investigated at 303.15 K. The kinetics of the biosorption process were examined at 600.00 and 1300 mg L-1, using pseudo-first-order, pseudo-second-order, and Avrami fractional-order models. The maximum biosorption capacity of BTV for AB-161 dye was 221.6 mg g-1. Considering the biosorption data and the functional groups of BTV, it can be inferred that the sorption mechanism of AB-161 is regulated by electrostatic interactions between ionized dye molecules and negative charges on BTV in an aqueous solution. Finally, the BTV was tested with a simulated effluent with 89.47% efficiency, presenting the BTV as a biosorbent for real effluents polluted with dyes.
Assuntos
Biomassa , Corantes/isolamento & purificação , Complexos de Coordenação/isolamento & purificação , Naftalenossulfonatos/isolamento & purificação , Trametes , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Concentração de Íons de Hidrogênio , CinéticaRESUMO
An approach to understand vines (Vitis vinifera) defense mechanism against heavy metal stress by isolation and determination of Hg-phytochelatins (PCs) complexes was performed. PCs are important molecules involved in the control of metal concentration in plants. PCs complex toxic metals through -SH groups and stores them inside cells vacuole avoiding any toxic effect of free metals in the cytosol. The Hg-PCs identification was achieved by determination of Hg and S as hetero-tagged atoms. A method involving two-dimensional chromatographic analysis coupled to atomic spectrometry and confirmation by tandem mass spectrometry is proposed. An approach involving size exclusion chromatography coupled to inductively coupled plasma mass spectrometry on roots, stems, and leaves extracts describing Hg distribution according to molecular weight and sulfur associations is proposed for the first time. Medium-low molecular weight Hg-S associations of 29-100 kDa were found, suggesting PCs presence. A second approach employing reversed-phase chromatography coupled to atomic fluorescence spectrometry analysis allowed the determination of Hg-PCs complexes within the mentioned fractions. Chromatograms showed Hg-PC2, Hg-PC3 and Hg-PC4 presence only in roots. Hg-PCs presence in roots was confirmed by ESI-MS/MS analysis.
Assuntos
Complexos de Coordenação/metabolismo , Mercúrio/metabolismo , Fitoquelatinas/metabolismo , Vitis/metabolismo , Adaptação Fisiológica , Cromatografia Líquida de Alta Pressão , Cromatografia de Fase Reversa , Complexos de Coordenação/isolamento & purificação , Mercúrio/isolamento & purificação , Fitoquelatinas/isolamento & purificação , Folhas de Planta/metabolismo , Raízes de Plantas/metabolismo , Caules de Planta/metabolismo , Estresse FisiológicoRESUMO
The synthesis, crystal structure and solution characterization of the cubane-type [Mo(3)(FeCl)S(4)(dmpe)(3)Cl(3)] (1) (dmpe = 1,2-bis(dimethylphophane-ethane)) cluster are reported and the ligand substitution processes of chloride by thiophenolate investigated. The kinetics and the intimate mechanism of these substitutions reveal that compound 1 undergoes a number of Fe and Mo site specific ligand substitution reactions in acetonitrile solutions. In particular, PhS(-) coordination at the tetrahedral Fe site proceeds in a single resolved kinetic step whereas such substitutions at the Mo sites proceed more slowly. The effect of the presence of acids in the reaction media is also investigated and reveals that an acid excess hinders substitution reactions both at the Fe and Mo sites; however, an acid-promoted solvolysis of the Fe-Cl bonds is observed. Electrospray ionization (ESI) and tandem (ESI-MS/MS) mass spectrometry allow the identification of all the reaction intermediates proposed on the basis of stopped-flow measurements. The distinctive site specific reactivity made it possible to isolate two new clusters of the Mo(3)FeS(4)(4+) family featuring mixed chlorine/thiophenolate ligands, namely Mo(3)S(4)(FeSPh)(dmpe)(3)Cl(3) (2) and [Mo(3)S(4)(FeSPh)(dmpe)(3)(SPh)(3)] (3). A detailed computational study has also been carried out to understand the details of the mechanism of substitution at the M-Cl (M = Mo and Fe) bonds as well as the solvolysis at the Fe-Cl sites, with particular emphasis on the role of acids on the substitution process. The results of the calculations are in agreement with the experimental observations, thus justifying the non-existence of an accelerating effect of acids on the thiophenolate substitution reaction, which differs from previous proposals for the Fe(4)S(4) and MoFe(3)S(4) clusters and some related compounds.