Fluid dynamic and drying of the poly-hydroxybutyrate (PHB) in rotating-pulsed fluidized bed

Orientadores: Sandra Cristina dos Santos Rocha, Nadia Rosa PereiraDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuimicaResumo: Polihidroxibutirato (PHB) é um poliéster completamente biodegradável e biocompatível. O interesse no desenvolvimento, produção e comercialização do PHB vem crescendo por ser um produto biodegradável e de produção integrada à cadeia de açúcar e álcool. A secagem é uma importante etapa do processo de produção do PHB, pois para o adequado pósprocessamento desse material deve-se garantir um teor de umidade limite de 0,5%. Neste contexto, este trabalho teve como objetivo estudar uma tecnologia de secagem, em um produto inovador e de importância na preservação ambiental. Foi realizado um estudo da fluidodinâmica e dos mecanismos de secagem do PHB em um leito fluidizado pulsado rotativo (LFPR). A escolha do equipamento baseou-se no fato de que o PHB úmido é coesivo e não apresenta fluidização convencional de qualidade. O secador de LFPR utiliza a pulsação do ar para desfazer os aglomerados de PHB melhorando a circulação das partículas dentro do leito. O presente estudo também incluiu a caracterização física do material antes e após a secagem. Para os ensaios de caracterização em que os equipamentos não trabalham em presença de umidade, a liofilização do PHB foi a alternativa encontrada para se caracterizar o material antes da secagem. O PHB apresentou um excelente comportamento fluidodinâmico em LFPR. A frequência de pulsação de 10 Hz foi a que apresentou comportamento mais favorável, com queda de pressão moderada e patamares de estabilidade. Por meio dos ensaios fluidodinâmicos foi possível determinar a velocidade de mínima fluidização vigorosa pulsada (VMV), parâmetro que ajudou a estabelecer a velocidade empregada para os experimentos de secagem. Durante a secagem do PHB foi avaliada a influência que a temperatura, velocidade e frequência de pulsação do ar exercem na cinética de secagem. Verificou-se excelente contato entre as partículas de PHB e o ar aquecido, com elutriação somente nos primeiros 10 minutos de secagem. As curvas de secagem do PHB indicaram períodos de taxa de secagem constante e decrescente. A temperatura e a velocidade do ar influenciaram positivamente o processo. Além disso, foi detectada a existência de um outro solvente além da água nas amostras de PHB, por meio da comparação entre as curvas de secagem obtidas com medidas de umidade feitas em estufa e em Karl Fischer. A análise termogravimétrica (TGA) também ajudou a detectar a presença de outro solvente além da água nas amostras de PHB. Os ensaios de caracterização física mostraram que as condições operacionais de secagem testadas não provocaram a degradação das partículas de PHB. Sob as condições consideradas ótimas de secagem, temperatura de 90 ºC, frequência de 7 Hz e velocidade do ar 0,40 m/s, foi atingida umidade igual a 0,56%, demonstrando a viabilidade do secador LFPR.Abstract: Poly-hydroxybutyrate (PHB) is polyester, completely biodegradable and biocompatible. The interest on its development, production and commercialization has arisen due to its biodegradability and production integrated to the sugar and alcohol chain. Drying is an important step of the PHB production because an adequate post-processing is achieved only at moisture contents less than 0.5%. The goal of this work was to study a drying technology for this innovative product of relevant importance for the environmental preservation. The fluid-dynamic and drying mechanisms analyses were made in a rotating-pulsed fluidized bed (RPFB). The equipment was chosen based on the fact that the wet PHB is cohesive and doesn't work properly in a conventional fluid bed. The RPFB dryer uses the air pulsation to undo the PHB agglomerate improving the circulation of the particles inside the bed. This study also included the physical characterization of the material before and after the drying. For the characterization tests that wouldn't work with moisture presence, the liophilization was the best alternative to characterize the material before the drying process. The PHBshowed an excellent dynamic behavior in RPFB. The pulsation frequency of 10 Hz presented the most favorable fluid dynamic conditions, resulting in moderate pressure drop and regime stability. Based on the fluid-dynamic study it was possible to determine the minimum vigorous fluidizing air flow (MVF), an important parameter to set the air velocity range for the drying experiments. An excellent contact between the PHB particles and the hot air was obtained during the drying runs, with particles elutriation only during the first 10 minutes. The influence of the temperature, velocity and frequency of air pulsation was evaluated on the drying kinetics. The PHB drying kinetics presented constant and decreasing-rate drying periods. The drying process was positively influenced by the air temperature and velocity. Furthermore, the presence of another solvent additionally to the water was detected in the PHB samples through the comparison between the drying curves obtained with moisture measurements made in an oven and in Karl Fischer equipment. The thermo gravimetric analysis also helped to detect the presence of another solvent in the PHB samples. The physical characterization tests showed that the drying operating conditions didn't cause degradation on PHB particles. The RPFB dryer showed to be a viable technique to dry PHB, as moisture content of 0.56% was reached at optimal operating conditions of air temperature of 90oC, air velocity of 0,40 m/s and frequency of pulsation of 7 Hz.MestradoEngenharia de ProcessosMestre em Engenharia Químic

Enhanced photocatalytic properties of reusable TiO2-loaded natural porous minerals in dye wastewater purification

Diatomite-based recyclable photocatalysts containing single lanthanide doped TiO nanoparticles (NPs) were synthesized by using simple sol–gel method. Photocatalytic activities of the prepared Ce- or La- single doped TiO/diatomite catalysts were estimated by the degradation of Rhodamine B (RhB) under simulated sunlight irradiation. The XRD and Raman spectra shown only anatase phase of TiO for the un-doped and Ce-doped samples. The TEM images revealed uniform distribution of TiO NPs on the matrix, indicating that diatomite played an important role to prevent the agglomeration of TiO NPs. Ce-TiO/diatomite showed a red shift in UV–visible light absorption edge with enhanced absorption intensity than un-doped sample, whereas La-TiO/diatomite showed a blue shift. The bandgap energy of 1.5%-Ce doped sample is as low as 2.75 eV. The XPS spectra showed the presence of both Ce and Ce oxidation states for Ce dopant. The photoluminescence spectra of the Ce-doped samples showed first decrease in the recombination centers with the maximum decrease for 1.5%-Ce doped sample and then started increase with the increasing Ce in the samples. As compared to the La-doped samples, a desired behavior was observed for the Ce-doped hybrid due to the redox Ce/Ce pairs acting as electron scavengers and localized unoccupied Ce 4f level narrowing the band gap. The incorporation with diatomite as support of TiO nanoparticles is contributed for the improved reusability and also gives a promising strategy to enable the application of nano-photocatalysts in a real wastewater remediation treatment

Chitosan membrane containing copper nanoparticles : characterization and possible applications

Orientador: Marisa Masumi BeppuTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuímicaResumo: Dentre os biopolímeros que têm maior capacidade em formar complexos metálicos, a quitosana (QUI) ocupa posição de destaque. Os materiais feitos de quitosana-metal podem ter aplicações em diferentes campos, tais como: na engenharia ambiental, na medicina, na catálise e até no desenvolvimento de biosensores. A quitosana pode atuar como um agente redutor e estabilizante de nanopartículas metálicas. O presente estudo aborda o tema que envolve o estudo de nanopartículas metálicas tendo como suporte quitosana. Escolheu-se como metal o cobre, pois a adsorção deste pela quitosana já é bem conhecida pela comunidade científica. Neste contexto, objetivou-se: (1) Sintetizar e caracterizar membrana QUI contendo nanopartículas de cobre; (2) avaliar o comportamento higroscópico e a (3) influência da presença de nanopartículas de cobre na adsorção de Cr(VI) e V(V) em membrana QUI. As nanopartículas de cobre foram sintetizadas pela reação de oxi-redução entre os cátions Cu(II), adsorvidos previamente à membrana de quitosana, e o agente redutor NaBH4. Verificou-se, por meio da técnica Espectroscopia de Absorção de Raios X Dispersiva (DXAS), que ao final do processo de redução as espécies de cobre eram compostas por 63% de Cu(0) e 37% de Cu(I). O comportamento higroscópico das membranas de quitosana com e sem cobre foi avaliado por curvas isotérmicas (25 °C) de sorção de água em equipamento DVS. As curvas foram analisadas pelo Modelo GAB e pela teoria de Zimm-Lundberg. De acordo com a segunda teoria, a formação de "clusters" de água ocorre para umidade relativa > 60% na estrutura das membranas testadas. A obtenção da curva isotérmica sob atmosfera de ar sintético mostrou que a quitosana previne ou retarda a oxidação do cobre. Além disso, avaliou-se o efeito do cobre na adsorção de Cr(VI) e V(V) em membrana de quitosana, por meio de curvas cinéticas e isotérmicas (pHs 4 e 6) e ensaios de caracterização (XPS, FTIR, EDX, ESEM e TEM). Diferentemente do Cr(VI), o comportamento cinético para o V(V) foi caracterizado pelo período de difusão interna. Para as membranas com cobre, observou-se existência de dois sítios de adsorção associados a: (1) reações de oxi-reduções entre os pares Cr(VI)/Cu(I) ou Cu(0) e V(V)/Cu(I) ou Cu(0) e (2) atração eletrostática entre os ânions cromato/vanadato e a quitosana. Nas melhores condições testadas (pH=4), a membrana com cobre apresentou capacidade máxima de adsorção igual a 4,36 e 12,2 mmol g-1 para a adsorção de Cr(VI) e V(V), respectivamente, segundo o modelo de Langmuir Duplo-sítio. A membrana de quitosana com nanopartículas de cobre mostrou-se um produto com promissora aplicação como adsorvente em soluções de Cr(VI) e V(V)Abstract: Among the biopolymers that have better capacity to form metal complexes, chitosan (CHI) occupies a prominent position. Materials made from chitosan-metal may have applications in different fields such as: engineering environment, medicine, catalysis and even the development of biosensors. Chitosan can act as a reducing agent and stabilizer for metal nanoparticles. The present study reports about the study of metal nanoparticles supported by chitosan. The objectives can be summarized as follows: (1) to synthesize and characterize membrane CHI containing copper nanoparticles, (2) to explore the hygroscopic behavior and (3) the influence of the presence of copper nanoparticles in the adsorption of Cr(VI) and V(V) on CHI membrane. Copper nanoparticles were synthesized by oxidation-reduction reaction between Cu(II), previously adsorbed on CHI membrane and the reducing agent NaBH4. It was found, by DXAS technique, that the copper species were composed of 63% Cu(0) and 37% Cu(I) after the reduction process. The hygroscopic behavior of CHI membrane, with and without copper, was evaluated by isotherms (25 ° C) of water sorption in DVS equipment. The curves were analyzed by the GAB model and the theory of Zimm-Lundberg. According to the second theory, the formation of water clusters occurs at relative humidity > 60%. The attainment of isothermal curve under synthetic air atmosphere showed that chitosan prevents or delays the oxidation of copper. In addition, we evaluated the effect of copper on the adsorption of Cr(VI) and V(V) on CHI membrane by means of kinetic/isothermal (pH 4 to 6) curves and laboratory characterization (XPS, FTIR, EDX , ESEM and TEM). Differently of Cr(VI), the kinetic behavior for V(V) was characterized by internal diffusion. For membranes with copper it was observed the existence of two adsorption sites that were associated with: (1) redox reactions between pairs Cr(VI)/Cu(I) or Cu(0) and V(V)/Cu(I) or Cu(0) and (2) electrostatic attraction between the anions chromate/vanadate and chitosan. Under the best conditions tested (pH = 4), the membrane with copper showed maximum adsorption capacity equal to 4.36 and 12.2 mmol g-1 for the adsorption of Cr(VI) and V(V), respectively, according to the Bi-site Langmuir model. The CHI membrane with copper nanoparticles can be a promising product with application as an adsorbent for Cr(VI) and V(V) metallic solutionsDoutoradoEngenharia de ProcessosDoutora em Engenharia Quimic

An XPS study of chromate and vanadate sorption mechanism by chitosan membrane containing copper nanoparticles

Chitosan (CHI) membrane containing copper nanoparticles (Cu-NPs) is a potential sorbent for chromate and vanadate removal from aquatic environment. X-ray photo-electron spectroscopy (XPS) was employed to investigate the influence of Cu-NPs on Cr(VI) and V(V) sorption processes. XPS is a powerful technique to understand the mechanisms involved in metal binding to the polymer. X-ray Diffraction (XRD) and Transmission electron microscopy (TEM) confirmed the Cu-NPs presence inside CHI membrane. XPS spectra obtained after sorption showed that Cr(VI) and V(V) ions interact differently with CHI membrane containing Cu-NPs, although both species have similar reduction potentials: Cr(VI)/Cr(III), E=+1.33V and V(V)/V(IV), E=+1.00V against Cu(II)/Cu(I), E=+0.16V. Cr(VI) was reduced to Cr(III) while Cu(I) was oxidized to Cu(II). On the other side, in the case of vanadate sorption, the interactions between vanadate species and CHI amine groups were more significant than the redox reactions involving copper

Spouted bed drying efficiency of bovine hydrolyzed collagen

Summary Bovine hydrolyzed collagen (BHC) is an important food supplement normally consumed in the form of capsules or powder in order to stimulate the synthesis of collagen, promote health and assist in esthetics. The transformation of liquid foods into powders by drying is a difficult operation due to the complex physical and chemical changes resulting from the use of high temperatures, which may result in low drying efficiency and unwanted physicochemical and nutritional characteristics in the final product. In this work, a process engineering approach was used aiming to maximize the drying efficiency and investigate the potential of using a spouted bed on the drying performance of BHC. The effects of feed mode, type of inert material and use of an adjuvant on powder production efficiency were analyzed using a 23 factorial experimental design. A statistical analysis showed significant effects of all the independent variables on drying performance. The maximum powder production efficiencies were achieved using polypropylene as the inert material and atomization as the feed mode. Under the optimal process conditions, up to 85% efficiency was obtained, demonstrating that the spouted bed is a technically viable equipment for drying BHC

Implementazione dei SIC marini della Regione Veneto: Ambienti di Transizione ed aree costiere.

Diatomite, a porous non-metal mineral, was used as support to prepare TiO2/diatomite composites by a modified sol–gel method. The as-prepared composites were calcined at temperatures ranging from 450 to 950 _C. The characterization tests included X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with an energy-dispersive X-ray spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption/desorption measurements. The XRD analysis indicated that the binary mixtures of anatase and rutile exist in the composites. The morphology analysis confirmed the TiO2 particles were uniformly immobilized on the surface of diatom with a strong interfacial anchoring strength, which leads to few drain of photocatalytic components during practical applications. In further XPS studies of hybrid catalyst, we found the evidence of the presence of Ti–O–Si bond and increased percentage of surface hydroxyl. In addition, the adsorption capacity and photocatalytic activity of synthesized TiO2/diatomite composites were evaluated by studying the degradation kinetics of aqueous Rhodamine B under UV-light irradiation. The photocatalytic degradation was found to follow pseudo-first order kinetics according to the Langmuir–Hinshelwood model. The preferable removal efficiency was observed in composites by 750 _C calcination, which is attributed to a relatively appropriate anatase/rutile mixing ratio of 90/10

Equilibrium isotherms of a biodegradable polymer polyhydroxybutyrate (PHB): heat of desorption determination 661

Polyhydroxybutyrate (PHB) belongs to a group of bacterial polyesters that may be considered as "green plastics", because of their biodegradable nature. The knowledge of the relationship between moisture content and water activity is essential for drying and storage. The thermodynamic equilibrium is characterized by equilibrium isotherms, and its determination is essential for better understanding of mechanisms in drying operations. Results on desorption isotherms of PHB are not available in the literature. Thus, the aim of this study was to analyze the equilibrium isotherms of PHB using GAB (Guggenhein-Anderson-de Boer) and GDW (generalized D́Arcy and Watt) models, and to determine the heat of desorption using Clausius-Clapeyron equation. The moisture equilibrium data for desorption isotherms of PHB were investigated at 40, 50 and 60 °C using the gravimetric static method. The monolayer moisture contents (from 0.16 to 0.23 % d.b.) decreased with increasing temperature. The Clausius-Clapeyron equation was considered adequate to forecast the heat of desorption, which was estimated as a function of the moisture content