Fernanda Condi de Godoi

Synthesis, characterization and activity of an immobilized photocatalyst: natural porous diatomite supported titania nanoparticles

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.

Synergy of nanoconfinement and surface oxygen in recrystallization of sulfur melt in carbon nanocapsules and the related Li–S cathode properties

We studied the recrystallization behaviours of sulfur melt in oxygen-containing carbon nanocapsules (CNCs). The effects of the oxidizing degree and the nanoconfinement of CNCs on sulfur recrystallization were investigated. We performed weak oxidation on CNCs by firstly grafting >C-Cl3 groups via a Friedel-Craft reaction and successive hydrolysis of >C-Cl3; and the strong oxidation was conducted in nitric acid. It is found that the weak oxidation preserved the CNC structure while the strong oxidation damaged the CNC morphology. Electron microscopy, X-ray diffraction, Raman spectroscopy and X-ray absorption spectroscopy were combined to characterize the sulfur crystallites in pristine and oxidized CNCs. The results revealed that the smaller sulfur crystallites preferentially formed in integrated CNCs (preserved nanoscale hollow structure) regardless of oxygen content; while the stronger oxidation and destruction of hollow structures fostered the growth of larger sulfur crystals. These results suggest a possible approach to control the growth of sulfur in carbon by combining oxygen and nanoconfinement effects, and hopefully to tune the related electrochemical properties in Li–S battery cathodes.

Fluid dynamics and drying of cohesive particles of a biodegradable polymer (poly-hydroxybutyrate) in a rotating pulsed fluidized bed

This article presents the results of fluid dynamics and drying of poly-hydroxybutyrate (PHB) granules in a rotating pulsed fluidized bed (RPFB) dryer. Cohesiveness of PHB results in problems when using conventional drying techniques, such as a fluidized bed dryer. The excess surface water on the particles may form agglomerates that damage the flowability of the material inside the dryer. The drying study in RPFB consisted of adjusting mathematical models for predicting the moisture evaporation during the constant drying rate period (linear fit) and the decreasing drying rate period (analytical solution of Ficks second law). The influence of temperature, rotation frequency, and velocity of the drying air on the constant drying rate (Nc), effective diffusivity (Deff), and mass of particles elutriated (me) during drying was evaluated. Particle porosity was analyzed before and after drying and scanning electronic microscopy (SEM) was employed to verify structural changes on the PHB granules after drying. The RPFB dryer proved to be appropriate to dry the PHB granules, resulting in an excellent fluid dynamics behavior of the particles inside the bed and providing uniform drying of the solids. Temperature and velocity of the air had a significant influence on the drying process, but rotation frequency did not affect the process in the ranges analyzed. Fine particle elutriation occurred during the first 10 min of drying. After drying, the porosity changed and breakage of the particles was observed due to attrition inside the bed.

Preparation of copper nanoparticles in chitosan membranes and their application as irreversible humidity indicators

Copper nanoparticles were prepared in chitosan (CHI) membranes via reduction of CuSO4.5H2O with sodium borohydride (BH). The fabrication process was performed in two steps: (1) first adsorbing Cu(II) ions in the CHI membranes, followed by (2) a chemical reduction of the Cu(II) ions to zero-valent copper (using BH). This study used SEM, DSC, and XRD to examine the morphological, thermal and chemical properties of the CHI-copper membranes. The synthesized CHI-copper membranes were exposed to ambient humidity and characterized by digital-image analysis with RGB color standards. The results showed that the CHI-copper membranes produced were successfully able to detect ambient moisture shown by the color changes of the membranes (from dark brown to blue). These CHI-copper membranes hold great promise in the engineering field for the production of humidity indicators and sensors.

Investigation of nanovesicle liposome powder production from soy lecithin by spray drying

ABSTRACT Aiming to produce stable nanosize liposome vesicles (∼100 nm), in a powder form, this study investigated the use of combined microfluidization–spray drying processes, using lactose as a stabilizing agent for vesicles during the process of dehydration. To determine the effective amount of lactose for stabilization, the vesicles were prepared at three different ratios (1:1, 1:3, and 1:5) of lecithin:lactose. The physicochemical properties of the nanoliposome powder and its reconstituted solution with water were evaluated over a storage period of 90 days at water activity below 0.3. The results demonstrated that upon addition of appropriate amount of lactose (1:3 or 1:5 of lecithin:lactose ratio), the aggregation of nanoliposomes was prevented and their size was maintained at lower than 130 nm during storage. Peroxide values of all nanoliposome formulations during the storage period remained below 3 meq/kg and there was no change in L*, a*, b* color parameters. The X-ray photoelectron spectroscopy analysis showed over-representation of lecithin on the power particle surface as compared to the bulk composition.

Eficiência da secagem de colágeno hidrolisado bovino em leito de jorro

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.