Edvani Curti Muniz’s research while affiliated with Federal University of Piauí and other places

In the present study, powders of α-Ag2WO4 (PAW) and β-Ag2MoO4 (PAM) were prepared through the coprecipitation method, while poly(vinyl alcohol) nanofibers (FPVA) and composite nanofibers of PVA/α-Ag2WO4 (FPAW) and PVA/β-Ag2MoO4 (FPAM) were prepared using the electrospinning technique. Several characterization techniques were applied to evaluate the structure of the obtained materials, as well as studies for assessing their antimicrobial properties. The antimicrobial activities of the composites against Pseudomonas aeruginosa and Staphylococcus aureus were investigated through the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). Our studies demonstrated that materials exhibit antibacterial activity against P. aeruginosa (MIC/MBC = 0.014/ND mg mL–1 for PAW; MIC/MBC = 1.43/1.43 for PAM; MIC/MBC = 1.35/1.35 mg mL–1 for FPAW; MIC/MBC = 3.68/11.03 mg mL–1 for FPAM and MIC/MBC = 8.78/ND mg mL–1 for FPVA) and S. aureus (MIC/MBC = 0.794/ND mg mL–1 for PAW; MIC/MBC = 1.43/ND for PAM; MIC/MBC = 1.35/1.35 mg mL–1 for FPAW; MIC/MBC = 3.68/3.67 mg mL–1 FPAM and MIC/MBC = 14.63/* mg mL–1 for FPVA). The cytotoxic concentrations (CC50, μg mL–1) against the VERO cells were 21.74 ± 0.04 for PAW, <15 for PAM, 103.70 ± 18.90 for FPAW, 111.22 ± 4.02 for FPAM, and >1000 for FPVA, thus indicating that the immobilization of the semiconductor to the FPVA mats decreases the cytotoxic effect of the materials studied as compared to not immobilized ones. The results suggest that powders and composite polymeric mats displayed antimicrobial action that was attributed to the production of reactive oxygen species (ROS), which are responsible for inducing high local oxidative stress, causing the death of both types of bacteria.

The air is a fundamental element for the life on Earth. Rapid urbanization and industrialization release large amounts of pollutants (harmful gases, microorganisms, and particulate matter, among others) into the atmosphere, leading to health hazards. Air filtration is still the most used and promising technique for protecting air against pollutants. The quality and efficiency of filtering process are dependent of the material used for the filter and other filter's properties. Several methods can be used for manufacturing filters, one of them uses fibrous membranes obtained mainly through electrospinning from polymeric solutions. Electrospinning is a technique that combines the application of an electrostatic field to a polymer solution that induces the fluid to move and, due to the solvent evaporation, results in the fibers formation. Electrospun membranes are constituted by fibers that the sizes spread on submicro and or nanometric scales. This review focuses on fiber membranes obtained by electrospinning for filtration of particulate matter. It is addressed the effect of solution, processing, and ambient parameters on the morphology and dimensional characteristics of fiber membranes. The basic principles of air filtration, test, and characterization of filter performance are also presented. The research progress on electrospun nanofibers as air filters in recent years is summarized and discussed. Finally, conclusion and future perspectives in electrospun fibers for air filtration are provided and discussed.

Internal curing is a process based on the addition of materials that function as water reservoirs in cementitious media. Superabsorbent hydrogels are an alternative that can be used as an internal curing agent, as they have the ability to absorb and release water in a controlled manner. In the present work, superabsorbent hydrogels based on crosslinked polyacrylamide in the presence of starch and sugarcane bagasse ash (SCBA) were developed and applied to mortars as an internal curing agent. The synthesized hydrogels were evaluated by SEM, FTIR, and swelling analysis. Cement pastes and mortars were produced using different amounts of hydrogel (0.03%, 0.06%, and 0.1% by weight). An analysis of the cement pastes and mortars revealed that hydrogel contributes to hydration, thus improving the quality of the product. Furthermore, the addition of 0.03% hydrogel by weight increased the mechanical resistance of the mortars in up to 26.8% at 28 days of curing as compared with reference (without hydrogel). To the best of our knowledge, this is the first study to use a hydrogel based on polyacrylamide crosslinked with starch and SCBA as a curing agent for mortars and cement pastes. This approach is environmentally friendly, because it uses a natural product (starch) and a byproduct from the sugarcane industry (SCBA).

Superabsorbent polymers (PSAs) have been extensively studied to act as internal curing agents in cementitious materials, as they have the characteristic of absorbing and releasing water in a controlled manner, which can contribute to the hydration process of a cementitious medium during its consolidation. Thus, hydrogels consisting of polyacrylamide (PAAm), pectin (Pec) and rice husk ash (RHA) were synthesized to be applied in cementitious matrices. In addition, the PSAs were characterized by FTIR, SEM, and XRD. For evaluating the usage of hydrogels as internal curing agents, different hydrogel contents—0.03, 0.06, and 0.1 (wt-%, relative to cementitious components)—were used for mortar preparation. The mechanical strengths of the cementitious materials were evaluated at day 7 and day 28 during the curing process. The addition of PSAs to the mortars caused an increase in mechanical resistance such that the 0.06% content presented better performance at day 7 of curing (4.07% higher) and at day 28 of curing (8.06% higher) when compared with the reference mortar (without the addition of PSAs) in the same curing periods. This work demonstrates that the addition of PSAs contributes to the hydration of a cementitious material, improving the mechanical resistance of the studied mortars.