Development of membranes for purification of liquid effluents from stainless steel pickling

Este trabalho foi desenvolvido no âmbito de um projecto europeu intitulado: “Operational demonstration of innovative and sustainable nitrate elimination in stainless steel pickling by higher power biological denitrification technique” Projecto RESP-CT-2007-00047, tendo em vista o desenvolvimento de membranas para o tratamento de efluente resultante da decapagem do aço inox. Numa fase inicial foram desenvolvidas membranas compostas assimétricas pelo método de polimerização interfacial. Estas membranas foram produzidas utilizando uma membrana comercial de suporte em polietersulfona e os filmes selectivos de poliamiada foram formados por reacção entre 1,3,5-tri(clorocarboni)benzeno (TMC) e várias dinaminas: piperazina (PIP), N-(2-aminoetil)-piperazina (EAP), 1,4-bis(3-aminopropil)-piperazina (DAPP), 6-metil-1,3,5 triazina-2,4 diamina (MTC), Isoforodiamina (IPD) e Dietilenetriamina (DET). A elaboração de membranas de TFC (thin film composite) tinha como objectivo a retenção de sais do efluente resultante da decapagem do aço inox. No entanto, chegou-se a conclusão de que o principal problema do efluente não era a retenção dos sais, mas sim a retenção da matéria orgânica. Assim, já não era necessa´ria a produção de membranas compostas, mas apenas uma membrana suporte simples de microfiltração. Numa segunda fase procedeu-se a preparação da membrana suporte pelo método da inversão de fase, tendo-se testado vários tipos de polímeros: PVC (polyvinyl chloride), PEI (Polyetherimide) e um polímero termoplástico geral. A membrana seleccionada foi a de PEI, com base na sua permeabilidade à água destilada e ao efluente resultante das águas residuais da decapagem do aço inox. Todas as membranas elaboradas durante a realização deste trabalho foram testadas na célula de Berghof a uma pressão de 4bar e com agitação. O principal prâmetro estudado foi a permeabilidade da membrana.

Rearranjos 3-aza-cope de N-alil-N-sililoxi enaminas

O rearranjo [3,3]-sigmatrópico térmico (180ºC) de diferentes N-alil-N-sililoxi enaminas foi estudado. Os respectivos produtos de rearranjo (éteres de óxima) foram obtidos com rendimentos elevados (80%). A regiosselectividade, [3,3] vs [1,3], e a diastereosselectividade do processo foram elevadas, superior a 99% e aproximadamente 80%, respectivamente. Foi demonstrada a importância do grupo sililoxilo na promoção do rearranjo face a substratos sem este tipo de substituição. Posteriormente, foi estudada a possibilidade de aceleração aniónica deste tipo de rearranjo por formação de oxianião ligado ao átomo de azoto. A estratégia seguida para a formação do mesmo, consistiu na O-dessililação de diferentes N-alil-N-sililoxi enaminas tendo-se obtido as nitronas correspondentes ou produtos de ciclização. Num exemplo envolvendo um derivado de isoxazole-5-(2H)-ona foi observado um aumento de velocidade do rearranjo por reacção com ião etoxilo. Este aumento de velocidade foi atribuído à abertura de anel do N-O éster cíclico para o N-oxianião, seguida de rearranjo e posterior fecho. Métodos alternativos de aceleração do rearranjo por geração de carga positiva, parcial ou completa, no átomo de azoto levaram apenas à dessililação das N-alil-N-sililoxi enaminas. ABSTRACT - [3,3]-sigmatropic rearrangement of a variety of N-allyl-N-silyloxy enamines was studied. The corresponding rearrangement products (oxime-ethers) were obtained in high yields (80%). High regioselectivity, [3,3] vs [1,3] (> 99%) and in appropriate cases, diastereoselectivity (80%) were observed. The importance of the silyloxy group in promoting the rearrangement, in relation to substrates lacking this functionality, is underlined. The possible anionic acceleration of the rearrangements was next examined by O-desilylation the N-silyloxy group bonded to the nitrogen. Attempted generation of these species however, was found to lead either to the corresponding nitrones or to cyclization products. In one particular example involving an isoxazol-5-(2H)-one derivative rate enhancement of rearrangement was indeed observed with ethoxide ion. It is tentatively attributed to ring opening of the cyclic N-O ester to the N-oxyanion ethyl ester followed by rearrangement and subsequent reclosure. Alternative methods to accelerate the process by generating a partial or complete positive charge on the nitrogen atom led only to desilylation.

Development of a biosensor for urea assay based on amidase inhibition, using an ion-selective electrode

A biosensor for urea has been developed based on the observation that urea is a powerful active-site inhibitor of amidase, which catalyzes the hydrolysis of amides such as acetamide to produce ammonia and the corresponding organic acid. Cell-free extract from Pseudomonas aeruginosa was the source of amidase (acylamide hydrolase, EC 3.5.1.4) which was immobilized on a polyethersulfone membrane in the presence of glutaraldehyde; anion-selective electrode for ammonium ions was used for biosensor development. Analysis of variance was used for optimization of the biosensorresponse and showed that 30 mu L of cell-free extract containing 7.47 mg protein mL(-1), 2 mu L of glutaraldehyde (5%, v/v) and 10 mu L of gelatin (15%, w/v) exhibited the highest response. Optimization of other parameters showed that pH 7.2 and 30 min incubation time were optimum for incubation ofmembranes in urea. The biosensor exhibited a linear response in the range of 4.0-10.0 mu M urea, a detection limit of 2.0 mu M for urea, a response timeof 20 s, a sensitivity of 58.245 % per mu M urea and a storage stability of over 4 months. It was successfully used for quantification of urea in samples such as wine and milk; recovery experiments were carried out which revealed an average substrate recovery of 94.9%. The urea analogs hydroxyurea, methylurea and thiourea inhibited amidase activity by about 90%, 10% and 0%, respectively, compared with urea inhibition.

Study of Pt/MCM-22 based catalysts in the transformation of n-hexane: effect of rare earth elements and mode of platinum introduction

The bifunctional transformation of n-hexane was carried out over Pt/MCM-22 based catalysts. MCM-22 was synthesized and submitted to ion exchange with rare earth nitrate solutions of La, Nd and Yb, followed by Pt introduction. Three different methods were used to introduce about 1 wt% of Pt in the zeolite: ion exchange, incipient wetness impregnation and mechanical mixture with Pt/Al(2)O(3). The bifunctional catalysts were characterized by transmission electron microscopy and by the model reaction of toluene hydrogenation. These experiments showed that, in the ion exchanged sample, Pt is located both within the inner micropores and on the outer surface, whereas in the impregnated one, the metal is essentially located on the outer surface under the form of large particles. The presence of RE elements increases the hydrogenating activity of Pt/MCM-22 since the location of these species at the vicinity of metal particles causes modification on its electronic properties. Whatever the mode of Pt introduction, a fast initial decrease in conversion is observed for n-hexane transformation, followed by a plateau related to the occurrence of the catalytic transformations at the hemicages located at the outer surface of the crystals. The effect of rare earth elements on the hydrogenating function leads to a lower selectivity in dibranched isomers and increased amounts of light products.

Production of hydroxamic acids by immobilized Pseudomonas aeruginosa cells Kinetic analysis in reverse micelles

Intact cells from Pseudomonas aeruginosa strain L10 containing amidase were used as biocatalysts both free and immobilized in a reverse micellar system. The apparent kinetic constants for the transamidation reaction in hydroxamic acids synthesis, were determined using substrates such as aliphatic, amino acid and aromatic amides and esters, in both media. In reverse micelles, K-m values decreased 2-7 fold relatively to the free biocatalyst using as substrates acetamide, acrylamide, propionamide and glycinamide ethyl ester. We have concluded that overall the affinity of the biocatalyst to each substrate increases when reactions are performed in the reversed micellar system as opposed to the buffer system. The immobilized biocatalyst in general, exhibits higher stability and faster rates of reactions at lower substrates concentration relatively to the free form, which is advantageous. Additionally, the immobilization revealed to be suitable for obtaining the highest yields of hydroxamic acids derivatives, in some cases higher than 80%. (C) 2013 Elsevier B.V. All rights reserved.

Biodiesel production over lithium modified lime catalysts: activity and deactivation

Biodiesel production by methanolysis of semi-refined rapeseed oil was studied over lime based catalysts. In order to improve the catalysts basicity a commercial CaO material was impregnated with aqueous solution of lithium nitrate (Li/Ca = 03 atomic ratio). The catalysts were calcined at 575 degrees C and 800 degrees C, for 5 h, to remove nitrate ions before reaction. The XRD patterns of the fresh catalysts, including the bare CaO, showed lines ascribable to CaO and Ca(OH)(2). The absence of XRD lines belonging to Li phases confirms the efficient dispersion of Li over CaO. In the tested condition (W-cat/W-oil = 5%; CH3OH/oil = 12 molar ratio) all the fresh catalysts provided similar biodiesel yields (FAME >93% after 4 h) but the bare CaO catalyst was more stable. The activity decay of the Li modified samples can be related to the enhanced, by the higher basicity, calcium diglyceroxide formation during methanolysis which promotes calcium leaching. The calcination temperature for Li modified catalysts plays an important role since encourages the crystals sinterization which appears to improve the catalyst stability. (C) 2013 Elsevier B.V. All rights reserved.

Microwave-assisted and solvent-free peroxidative oxidation of 1-phenylethanol to acetophenone with a CuII-TEMPO catalytic system

The water-soluble copper(II) complex [Cu(H2R)(HL)]center dot H2O (1) was prepared by reaction of copper(II) nitrate hydrate with (E)-2-(((1-hydroxynaphthalen-2-yl)methylene)amino) benzenesulfonic acid (H2L) and diethanolamine (H3R). It was characterized by IR and ESI-MS spectroscopies, elemental and X-ray crystal structural analyses. 1 shows a high catalytic activity for the solvent-free microwave (MW) assisted oxidation of 1-phenylethanol with tert-butylhydroperoxide, leading, in the presence of TEMPO, to yields up to 85% (TON = 850) in a remarkably short reaction time (15 min, with the corresponding TOE value of 3.40 x 10(3) h(-1)) under low power (25W) MW irradiation. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.

Synthesis and characterization of COPPER(II) 4´-phenyl-terpyridine compounds and catalytic application for aerobic oxidation of benzylic alcohols

The reactions between 4'-phenyl-terpyridine (L) and nitrate, acetate or chloride Cu(II) salts led to the formation of [Cu(NO3)(2)L] (1), [Cu(OCOCH3)(2)L]center dot CH2Cl2 (2 center dot CH2Cl2)and [CuCl2L]center dot[Cu(Cl)(mu-Cl)L](2) (3), respectively. Upon dissolving 1 in mixtures of DMSO-MeOH or EtOH-DMF the compounds [Cu(H2O){OS(CH3)(2)}L]-(NO3)(2) (4) and [Cu(HO)(CH3CH2OH)L](NO3) (5) were obtained, in this order. Reaction of 3 with AgSO3CF3 led to [CuCl(OSO2CF3)L] (6). The compounds were characterized by ESI-MS, IR, elemental analysis, electrochemical techniques and, for 2-6, also by single crystal X-ray diffraction. They undergo, by cyclic voltammetry, two single-electron irreversible reductions assigned to Cu(II) -> Cu(I)and Cu(I) -> Cu(0) and, for those of the same structural type, the reduction potential appears to correlate with the summation of the values of the Lever electrochemical EL ligand parameter, which is reported for the first time for copper complexes. Complexes 1-6 in combination with TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxyl radical) can exhibit a high catalytic activity, under mild conditions and in alkaline aqueous solution, for the aerobic oxidation of benzylic alcohols. Molar yields up to 94% (based on the alcohol) with TON values up to 320 were achieved after 22 h.

Is it possible to remove polymeric nanoparticles from aqueous paints during the activated sludge treatment?

The market for emulsion polymers (latexes) is large and growing at the expense of other manufacturing processes that emit higher amounts of volatile organic solvents. The paint industry is not an exception and solvent-borne paints have been gradually substituted by aqueous paints. In their life-cycle, much of the aqueous paint used for architectural or decorative purposes will eventually be discharged into wastewater treatment facilities, where its polymeric nanoparticles (mainly acrylic and styrene-acrylic) can work as xenobiotics to the microbial communities present in activated sludge. It is well established that these materials are biocompatible at macroscopic scale. But is their behaviour the same at nanoscale? What happens to the polymeric nanoparticles during the activated sludge process? Do nanoparticles agregate and are discharged together with the sludge or remain in emulsion? How do microorganisms interact with these nanoparticles? Are nanoparticles degradated by them? Are they adsorbed? Are these nanoparticles toxic to the microbial community? To study the influence of these xenobiotics in the activated sludge process, an emulsion of cross-linked poly(butyl methacrylate) nanoparticles of ca. 50 nm diameter was produced and used as model compound. Activated sludge from a wastewater treatment plant was tested by the OCDE’s respiration inhibition test using several concentrations of PBMA nanoparticles. Particle aggregation was followed by Dynamic Light Scattering and microorganism surfaces were observed by Atomic Force Microscopy. Using sequential batch reactors (SBRs) and continuous reactors, both inoculated with activated sludge, the consumption of carbon, ammonia, nitrite and nitrate was monitored and compared, in the presence and absence of nanoparticles. No particles were detected in all treated waters by Dynamic Light Scattering. This can either mean that microorganisms can efficiently remove all polymer nanoparticles or that nanoparticles tend to aggregate and be naturally removed by precipitation. Nevertheless respiration inhibition tests demonstrated that microorganisms consume more oxygen in the presence of nanoparticles, which suggests a stress situation. It was also observed a slight decrease in the efficiency of nitrification in the presence of nanoparticles. AFM images showed that while the morphology of some organisms remained the same both in the presence and absence of nanoparticles, others assumed a rough surface with hilly like shapes of ca. 50 nm when exposed to nanoparticles. Nanoparticles are thus likely to be either incorporated or adsorbed at the surface of some organisms, increasing the overall respiration rate and decreasing nitrification efficiency. Thus, despite its biocompatibility at macroscopic scale, PBMA is likely to be no longer innocuous at nanoscale.

Silver coordination polymers with tri- and hexacyanoethyl-functionalized macrocyclic ligands

Tri-and hexa-cyanoethyl functionalized 17-(L-1) and 42-membered (L-2) macrocyclic compounds were obtained by [1 + 1] (for L-1) or [2 + 2] (for L-2) cyclocondensation of the corresponding dialdehyde and diethylenetriamine, followed by hydrogenation by KBH4 and subsequent cyano-functionalization with acrylonitrile. They react with silver nitrate, leading to the formation of [AgL1](NO3) (1) and of the metalorganic coordination polymers [Ag-2(NO3)(2)L-1](n) (2) and {[Ag2L2](NO3)(2)}(n) (3). The complexes were characterized by elemental analysis, H-1 NMR, C-13 NMR, IR spectroscopies, and ESI-MS; moreover, L-2, 1, 2 and 3 were also characterized by single crystal X-ray diffraction. The metal cation in 1 is pentacoordinated with a N3O2 coordination environment; in 2, the metal cations display N4O2 octahedral and N2O3 square-pyramid coordination and in 3 they are in square-planar N-4 sites. In 1, the ligand acts as a pentadentate chelator, and in the other two cases, the ligands behave as octadentate chelators in a 1 kappa N-3:kappa O-2,2 kappa N,3 kappa N,4 kappa N (in 2) or 1 kappa N-3,2 kappa N-3,3 kappa N,4 kappa N fashion (in 3). The cyanoethyl strands of the ligands are directly involved in the formation of the 2D frameworks of 2 and 3, which in the former polymer can be viewed as a net composed of hexametallic 36-membered macrocyclic rings and in the latter generates extra hexametallic 58-membered cyclic sets that form zig-zag layers. The thermal analytical and electrochemical properties of these silver complexes were also studied.

Y Trinuclear Cu-II structural isomers coordination, magnetism, electrochemistry and catalytic activity towards the oxidation of alkanes

The reaction of the Schiff base (3,5-di-tert-butyl-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H3L) with copper(II) nitrate, acetate or metaborate has led to the isomeric complexes [Cu-3(L)(2)(MeOH)(4)] (1), [Cu-3(L)(2)(MeOH)(2)]2MeOH (2) and [Cu-3(L)(2)(MeOH)(4)] (3), respectively, in which the ligand L exhibits dianionic (HL2-, in 1) or trianionic (L3-, in 2 and 3) pentadentate 1O,O,N:2N,O chelation modes. Complexes 1-3 were characterized by elemental analysis, IR spectroscopy, single-crystal X-ray crystallography, electrochemical methods and variable-temperature magnetic susceptibility measurements, which indicated that the intratrimer antiferromagnetic coupling is strong in the three complexes and that there exists very weak ferromagnetic intermolecular interactions in 1 but weak antiferromagnetic intermolecular interactions in both 2 and 3. Electrochemical experiments showed that in complexes 1-3 the Cu-II ions can be reduced, in distinct steps, to Cu-I and Cu-0. All the complexes act as efficient catalyst precursors under mild conditions for the peroxidative oxidation of cyclohexane to cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone, leading to overall yields (based on the alkane) of up to 31% (TON = 1.55x10(3)) after 6 h in the presence of pyrazinecarboxylic acid.

Desenvolvimento de métodos de análise físico-química em águas usando um analisador multiparamétrico AQUAKEM

Trabalho Final de mestrado para obtenção do grau de Mestre em Engenharia Química e Biológica

Fabrication of electrochemically reduced graphene oxide/cobalt oxide composite for charge storage electrodes

Electrochemically-reduced graphene oxide (Er-GO) and cobalt oxides (CoOx) were co-electrodeposited by cyclic voltammetry, from an electrolyte containing graphene oxide and cobalt nitrate, directly onto a stainless steel substrate to produce composite electrodes presenting high charge storage capacity. The electrochemical response of the composite films was optimized by studying the parameters applied during the electrodeposition process, namely the number of cycles, scan rate and ratio between GO/Co(NO3)(2) concentrations in the electrolyte. It is shown that, if the appropriate conditions are selected, it is possible to produced binder-free composite electrodes with improved electrochemical properties using a low-cost, facile and scalable technique. The optimized Er-GO/CoOx developed in this work exhibits a specific capacitance of 608 F g(-1) at a current density of 1 A g(-1) and increased reversibility when compared to single CoOx. (C) 2015 Elsevier B.V. All rights reserved.