Thermal evaluation of the use of porous ceramic plates on ventilated façades—part II: Thermal behavior

The effects of porous ceramic plates on the thermal behavior of ventilated façades were evaluated, and the results are presented herein. Thermal behavior in a ventilated façade of specimens containing 40 wt% of lime mud and a firing temperature of 1100°C was evaluated and compared with a commercial porcelain ceramic tile, which was the reference material. An experimental apparatus was designed to evaluate the thermal performance of the studied ventilated façades. The results revealed that the ventilated façade composed of the studied porous ceramic tiles produced a greater reduction in temperature between the external environmental and the interior of a box representing a building (ΔT5) of 65.7°C, compared with the façade composed of the commercial porcelain ceramic tiles (ΔT5 = 56.0°C) and even the traditional façade (ΔT5 = 49.1°C). Thus, porous ceramic tiles based on byproducts are promising candidates for ventilated façade systems.     

Ecotoxicological analysis of glasses obtained from industrial residues using E. coli and S. aureus as bioindicators

This work deals with the study of the effect of coal ashes and industrial residues in the inertness of glasses designed for industrial uses. Five formulations with four factors (residues) and constraints were used according a mixture design. The residues were dried, sieved and mixed according to the design. The formulations were melted at 1450 °C during 2 h for stabilization using 10% wt of Na₂CO₃ (fluxing agent). The melts were cast into a refrigerated water mold and annealed at 600 °C, and thus, the glasses were analyzed regarding their ecotoxicological effect using the Agar Diffusion Test for Escherichia coli and Staphylococcus aureus as bioindicators, comparing the results with the Artemia sp. Acute Toxicity Test. The results were studied by analysis of variance in order to determine the individual influence of each residue in the inertness of the glass system. As a final result, the ecotoxicological analysis showed that the galvanic residue makes a non-inert glass due to the high iron and zinc content of this waste. The Agar Diffusion Test is a fast and accurate technique to determine the toxicity of glass systems only for high concentration samples.     

Bactericidal Low Density Polyethylene (LDPE) urinary catheters: Microbiological characterization and effectiveness

This study investigated the antimicrobial efficacy of Low Density Polyethylene (LDPE) catheters containing triclosan at 0.10 wt.%, 0.50 wt.%, 1.00 wt.% and 1.50 wt.%. The catheters were characterized with the Minimum Inhibitory Concentration (MIC) and Agar Diffusion Tests. They were evaluated in terms of incrustation, biofilm formation and the efficiency of inhibition of bacterial growth after thirty days of lab tests with artificial urine. This research demonstrated the effectiveness of triclosan for inhibiting the growth of microorganisms when incorporated into long-term catheters. The antimicrobial efficiency and genotoxicity results demonstrate that 0.5 wt.% triclosan is the optimal concentration. The genotoxicity test results indicate that triclosan did not result in any significant alterations in the cellular DNA compared to the catheter without triclosan.     

Synthesis of 4A zeolites from kaolin for obtaining 5A zeolites through ionic exchange for adsorption of arsenic

The synthesis of adsorbing zeolite materials requires fine control of the processing variables. There are distinct process variable settings for obtaining specific desired types of zeolites. The intent of this study was to obtain 4A zeolites from kaolin in order to obtain 5A zeolites through ionic exchange with the previously synthesized zeolite. This zeolite 5A was used as an adsorbent for arsenic ions. The results obtained were satisfactory.     

Effect of the Extrusion Process on the Bactericidal Performance of Biocidal Polypropylene Catheters

This work concerns polypropylene biocidal catheters that incorporate the triclosan molecule. Many studies have applied triclosan as a bactericidal agent in the polymeric matrix but without considering the effect of processing on the biocidal properties. Using the optimal temperature and shear rate during the extrusion process can promote the best microbiological response for a biocidal catheter. Catheters were processed using a linear extruder while systematically varying the triclosan content, processing temperature and screw velocity. A diffusion test in agar and an evaluation of the chemical structure of the polypropylene and triclosan using FTIR were used to characterize the bactericidal properties.     

Bactericidal polyurethane foam mattresses: Microbiological characterization and effectiveness

The antimicrobial compounds 2.4.4.″-tricloro-2″ hydroxydiphenyl ether (triclosan), 5-chloro-2-methyl-4-isothiazolin-3-one (isothiazolone) and bis(2-pyridylthio)zinc 1,1′-dioxide (zinc pyrithione) were incorporated into polyurethane foam matrixes. Concentrations of 0.20 wt.%, 0.50 wt.% and 1.00 wt.% of each biocide compound were used, and the infection reduction capacity was evaluated for different types of bacteria. The microbiological tests with polyurethane foams were performed with agar diffusion tests using the pour plate technique and analyzing the colony formation units (CFU) as a function of time. In preliminary tests, the micro-organisms Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Salmonella choleraesuis and Staphylococcus aureus were used. Tests in vitro showed that polyurethane foam containing zinc pyrithione gave the best performance. Genotoxicity tests were conducted to evaluate if the use of zinc pyrithione in the polyurethane causes harm to human users. Microbiological tests were also performed on the surfaces of mattresses that were produced with polyurethane foam to verify their antimicrobial properties. The significant decrease in the number of micro-organisms within the foam showed the effectiveness of the zinc pyrithione as an antimicrobial, while the genotoxicity tests demonstrated the absence of collateral effects for the users.     

Synthesis and ion exchange of zeolites produced from kaolin for separation of oxygen from atmospheric air

Lithium-based zeolites are the most commonly used materials in PSA (pressure swing adsorption) oxygen concentration from atmospheric air. Synthesizing these adsorbents using mineral raw materials adapts to worldwide environmental requests, as only high-purity chemical reactants such as aluminates and silicates are usually used. The present work aims to synthesize and characterize zeolites using kaolin as raw material by studying the influence of the metakaolinization temperature and SiO₂/Al₂O₃ and H₂O/Na₂O molar ratios by experimental design. Ion exchange was used to incorporate lithium into synthesized zeolites. Kaolin was treated thermically and characterized, and zeolites were synthesized by a hydrothermal reaction. After synthesis, ionic exchange of Na⁺ ions by Li⁺ was performed. The results indicated the presence of three main phases, zeolites A, X, and P. Using ANOVA, it was found that the factors that contributed significantly to the formation of zeolite X were the H₂O/Na₂O and SiO₂/Al₂O₃ molar ratios. For zeolite A, the major influence was by the metakaolinization temperature and for zeolite P none of the factors was influential. Zeolites that incorporated higher amounts of lithium showed higher N₂ adsorption potential, indicating that even without pure phases formed, it was possible to obtain similar adsorption efficiency to commercial zeolite.     

Thermal evaluation of the use of porous ceramic plates on ventilated façades – Part I: Effect of composition and firing temperature on porosity and bending strength

The effect of composition and firing temperature on porosity and bending strength of porous ceramic plates for using in ventilated façades were investigated. Two byproducts, basalt and lime mud, were used to obtain porous ceramic plates in accordance with the circular economy concept. Basalt, which is a fine powder-based byproduct generated from the processing of basaltic rock, was used to replace feldspar as the flux mineral in a ceramic composition. Lime mud, a byproduct of the pulp and paper mill process and containing a high content of calcium carbonate (CaCO₃), was incorporated in the ceramic composition to generate pores. The specimens were prepared using three different amounts of lime mud (20, 30, and 40 wt%) and three firing temperatures (900°C, 1000°C, and 1100°C), and their porosity and bending strength were determined. The highest performing specimen (5.1 ± 1.3 MPa bending strength and 42.6 ± 0.5% porosity) was obtained by using 40 wt% of lime mud and a firing temperature of 1100°C with potential for further thermal tests in a ventilated façade in comparison with a commercial porcelain ceramic tile as reference material.     

Effects of roughness parameters on slip resistance for different methods used to determine the coefficient of friction for ceramic floor tiles

This work attempts to evaluate the correlation between the roughness parameters and different standardized methodologies for determining the coefficient of friction of ceramic floor tiles. Eight different types of ceramic tiles were evaluated, and each one was characterized for their coefficient of friction/slip resistance in accordance with the standards NBR 13818, ANSI A137.1, and AS 4586. The surfaces were also characterized in relation to surface roughness by means of contact profilometry. The measured friction and roughness parameters were correlated by means of analysis of variance. The results showed a correlation tendency according to a third-degree equation for tests performed in wet conditions. The study results showed that the roughness parameters influence the coefficient of friction with a confidence level of 95%. Considering the safe values indicated for the respective standards for the evaluated methods, a Rz value of 25 μm ensures that a tested surface can be considered safe in a wet-condition test, regardless of the method used to determine the coefficient of friction.     

The influence of particle size and AgNO3 concentration in the ionic exchange process on the fungicidal action of antimicrobial glass

Antimicrobial materials have long been used as an effective means of reducing the risks posed to humans by fungi, bacteria and other microorganisms. These materials are essential in environments where cleanliness, comfort and hygiene are the predominate concerns. This work presents preliminary results for the development of a fungicidal vitreous material that is produced by the incorporation of a silver ionic specimen through ionic exchange reactions. Silver ions were incorporated into powdered glass via ionic exchange in an ionic medium containing silver species with different concentrations of AgNO₃. The fungicidal efficiency of the samples was studied as a function of the AgNO₃ concentration and the particle size of the glass using the agar diffusion test for the microbiological analysis of the fungus species Candida albicans. The samples were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The experimental results showed that the fungicidal effect was dependent on the AgNO₃ concentration in the ionic exchange medium but was not dependent on the particle size of the glass.