Cristian Berto da Silveira

LZSA glass ceramic foams prepared by replication process

Abstract In this study the replication process was applied to produce porous glass ceramic foams. Polyurethane (PU) sponges were impregnated by immersion in aqueous slurry of a parent glass (mean particle size around 3 μm) from the system Li2O–ZrO2–SiO2–Al2O3 and submitted to heat treatment. From TGA and IR analyses, two main paths of thermal decomposition of PU sponges were observed at 312 and 393°C, which were associated with the decomposition products CO2, CO, NH3 and isocyanide. According to linear thermal shrinkage and DTA measurements, sintering starts at around 570°C and is completed below 700°C, when crystallisation takes place. The main crystalline phases identified by XRD analysis were zirconium silicate, lithium metasilicate and β-spodumene. The morphology and properties of the glass ceramic foams obtained from PU sponges were quite similar for all samples tested. From XCT measurements, a mean cell diameter of around 260 μm and mean strut thickness of 185 μm were calculated, corresponding to a porosity of 75–78%. Compressive strength values under 500 kPa and permeability coefficient in air of about 1000 Darcy were also measured for the samples tested. LZSA glass ceramic foams can be a very interesting alternative to ceramic gas filters, owing to low temperature processing, and to superior properties such as corrosion and thermal shock resistance.

Composição química de um resíduo alcalino da indústria de papel e celulose (DREGS)

Dregs is an alkaline solid by-product generated in the cellulose manufacturing industry that could be used to correct soil acidity. The present study aimed to evaluate the chemical composition of this product and some of its properties. The dregs presented 354 g kg-1 of calcium, neutralization capacity of 80.3%, and pH 10.7, besides low concentration of sodium (10.2 g kg-1), lead (62.9 mg kg-1) and cadmium (5.6 mg kg-1). Thus, it is a product that can safely be used to increase the soil pH.

Decomposição térmica de espumas de poliuretano para fabricação de vitrocerâmica celular de Li2O-ZrO2-SiO2-Al2O3 (LZSA)

Characterization of the thermal decomposition of polyurethane (PUR) foams was performed by Fourier-transformed infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). Three main weight loss paths were observed by TGA, the residue being lower than 3 wt.% for 3 different PUR foams analyzed. FT-IR spectra indicated CO2, CO, NH3 and isocyanides as main decomposition products. PUR foams of different cell sizes were immersed in a slurry of the parent glass ceramic of composition Li2O-ZrO2-SiO2-Al 2O3 (LZSA) and submitted to heat treatment. The LZSA cellular glass ceramics obtained after sintering and crystallization resembled the original morphology of the PUR foams.

Low-cost approach to increase the analysis throughput of bar adsorptive microextraction (BAµE) combined with environmentally-friendly renewable sorbent phase of recycled diatomaceous earth

In this study, a novel apparatus for bar adsorptive microextraction (BAµE) using a voltage regulator was proposed as an alternative tool to improve the analysis throughput. In addition, recycled diatomaceous earth obtained as a brewery residue was employed as a biosorbent coating for the determination of methyl paraben, ethyl paraben, benzophenone and triclocarban in water samples by high-performance liquid chromatography-diode array detection (HPLC-DAD). The use of the extraction devices, comprised of floating adsorptive bars of 7.5mm length, in the extractions with magnetic stirrers linked to a voltage regulator enabled the analysis of multiple samples, simultaneously. The method optimization was carried out by univariate and multivariate analyses. The optimal conditions for the method were sample solution at pH 5, extraction time of 90min and liquid desorption in 100µL of acetonitrile:methanol (50:50, v/v) for 15min. The total sample preparation time was 17.5min per sample for a simultaneous batch of six extractions. The R2 values for the calibration curves obtained were higher than 0.9985. The limits of detection (LODs) varied from 0.19 to 2μgL-1 and the limits of quantification (LOQs) ranged from 0.63 to 6.9μgL-1. The method was applied to freshwater samples collected from Peri Lagoon (Florianópolis, SC, Brazil) and the relative recoveries ranged from 63% to 124% with relative standard deviations (RSDs) of < 20% (n = 2). The RSD values for the reproducibility of the performance of the magnetic stirrers and inter-device extraction efficiency were lower than 14% (n = 3) and 11% (n = 3), respectively.

Metodologias para reutilização do resíduo de terra diatomácea, proveniente da filtração e clarificação da cerveja

METHODOLOGY FOR THE REUSED OF THE DIATOMITE EARTH RESIDUE, ORIGINATING FROM THE FILTRATION AND CLARIFICATION OF THE BEER. The earth diatomite is a material used by the industries in the filtration process and clarification of the beer. This material presents a reduced useful life due to the blockages of their pores during the filtration process. The objective of this work was to reactivate the properties of filtration of the earth diatomite, saturated with organic matter during the filtration stage, starting from a controlled thermal treatment. The obtained results demonstrated that the earth diatomite saturated with organic matter submitted to a controlled thermal treatment has their filtration properties reactivated, could be reused in the beer production process.

Potassium ions release from polysaccharide films

In plant growth media of low negative charge, potassium (K) is leached out easily with adverse consequences on its availability to plants and on the environment, since all K fertilizers are completely soluble. The objective of this study was to prepare films based on sodium carboxymethylcellulose (CMC), sodium alginate (SA) and a 1:1 (v/v) CMC:SA mixture to incorporate K and investigate its subsequent release. The film properties were evaluated considering miscibility, glass transition temperature, morphology and permeation of potassium. The absence of strong interactions, the small variation in the glass transition temperature and the roughness detected in the cross-section micrographs of the 1:1 CMC:SA mixtures, indicated a partial miscibility among the components. As a consequence of the above-mentioned characteristics, film release of potassium was highest for the 1:1 CMC:SA mixture and lowest for SA. The release mechanism of K from the 1:1 CMC:SA mixture was controlled by a diffusion process, however, associated effects due to swelling and erosion of the matrix films, were observed for the pure CMC and SA systems. Films of CMC, SA and their 1:1 mixture were able to delay the K release, which can bring considerable benefits in terms of plant growth when media with low negative charges are used.

Adsorção de Cu e Zn num Latossolo Vermelho tratado com dejetos suínos

Cu and Zn adsorption in an Oxisol treated with pig slurry Cooper and zinc derived from pig slurry can accumulate in the soil, posing risks to human and animal health. The objective of this study was to determine the adsorption capacity and the competition of Cu and Zn in Oxisols that received continued applications of 200 m 3 ha -1 year -1 of pig slurry for seven years and to compare with soil under natural conditions. To evaluate the adsorption, Cu and Zn solutions were applied to the soil at concentrations of 0, 25, 50, 100, 150, 200, 400, 1.200 μmol L -1 ; soil:solution ratio of 1:100.Merck Certipur standard solution 1.000 mg L -1 was utilized to construct the levels of Zn and Cu. The adsorption of Cu showed a sigmoid behavior (S-type isotherm) in soil with no slurry application and linear behavior (C-type isotherm) in soil with pig slurry . The maximum adsorption of Cu in soil without pig slurry was 3,021 mg kg -1 . For Zn, all the isotherms showed linear behavior. The maximum adsorption capacity of Cu and Zn was not reached in soil with slurry. These results show that the studied Oxisol has a high capacity to retain Zn and Cu from pig slurry .