Adsorption for rhodamine b dye and biological activity of nano-porous chitosan from shrimp shells.

The present work aims to evaluate the removal capacity of Rhodamine B dye (RhB) using nano-porous chitosan (NC) from shrimp shells. NC was characterized by XRD, SEM-EDS, N2 porosimetry, zeta potential (ZP), FTIR, DLS, and zero charge point (pHZCP). Compound central rotational design (CCRD) was used to determine the ideal condition and antimicrobial activity was evaluated against different strains. NC showed characteristic of semi-crystalline material with negative charge surface (around - 21.13 mV), and SBET = 1.12 m2 g-1, Vp = 0.0064 cm3 g-1, Dp = 32.09 nm and pHZCP ≈ 7.98. Kinetic adsorption showed the pseudo first-order model had the best fit, with adsorption capacity (q1) between 3.78 and 64.43 mg g-1 and pseudo first-order kinetic constant (k1) between 0.066 and 0.052 min-1. Sips model best described the equilibrium data, with a maximum adsorption capacity of 505.131 mg g-1. Antimicrobial activity was observed at 0.25 mg mL-1 for different strains. Therefore, NC has potential application in the removal of the dye, combining sustainable development associated with nanotechnology.

Silver nanoparticles from residual biomass: Biosynthesis, characterization and antimicrobial activity.

The industrial effluent contaminated with organic pollutants has been causing an increase in the toxicity of the ecosystem, causing a great environmental impact. Thus, the present work aims the green synthesis of silver nanoparticles (AgNPs) from Aloe vera, its characterization and antimicrobial activity against Pseudomonas aeruginosa (ATCC 27853) and Staphylococcus aureus (ATCC 25923). AgNPs were characterized by X-ray diffraction (XRD), Scanning Electronic Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), Zeta Potential (ZP) and N2 porosimetry (BET/BJH method). Antimicrobial activity were carried out by Minimal Inhibitory Concentration (MIC) method. The XRD demonstrated characteristic peaks of AgNPs at 38.29°; 44.55° and 64.81°, and SEM-EDS micrographs showed that AgNPs produced by biomolecules of Aloe vera extract resulted in a weight concentration around 92.59% silver, 7.15% oxygen and 0.26% chlorine. Regarding zeta potential, all samples showed negative electric charge (around -35.3 mV), while N2 porosimetry resulted in a surface specific area of 6.09 m2 g-1, with a volume and diameter pore of 0.032 cm³ g-1 and 33.47, respectively. Antimicrobial activity was observed at 15.62 µg mL-1 and 31.25 µg mL-1 for P. aeruginosa and S. aureus, respectively. Thus, AgNPs can be considered a promising nanoparticle for degradation of organic pollutants in aqueous solution as well as an adjuvant for treatment of microbial infections.

Iron oxide nanocatalyst with titanium and silver nanoparticles: Synthesis, characterization and photocatalytic activity on the degradation of Rhodamine B dye.

Nowadays, there is a growing concern about the environmental impacts of colored wastewater. Thus, the present work aims the synthesis, characterization and determination of photocatalytic activity of iron oxide (Fe2O3) nanocatalyst, evaluating the effect of hybridization with titanium (TiNPs-Fe2O3) and silver (AgNPs-Fe2O3) nanoparticles, on the degradation of Rhodamine B dye (RhB). Nanocatalysts were characterized by XRD, SEM, TEM, FTIR, N2 porosimetry (BET/BJH method), zeta potential and DRS. Photocatalytic tests were performed in a slurry reactor, with the nanocatalyst in suspension, using RhB as a target molecule, under ultraviolet (UV) and visible radiation. Therefore, the photocatalytic activity of the nanocatalysts (non-doped and hybridized) was evaluated in these ideal conditions, where the AgNPs-Fe2O3 sample showed the best photocatalytic activity with a degradation of 94.1% (k = 0.0222 min-1, under UV) and 58.36% (k = 0.007 min-1, under visible), while under the same conditions, the TiO2-P25 commercial catalyst showed a degradation of 61.5% (k = 0.0078 min-1) and 44.5% (k = 0.0044 min-1), respectively. According with the ideal conditions determined, reusability of the AgNPs-Fe2O3 nanocatalyst was measured, showing a short reduction (about 8%) of its photocatalytic activity after 5 cycles. Thus, the Fe2O3 nanocatalyst can be considered a promising catalyst in the heterogeneous photocatalysis for application in the degradation of organic dyes in aqueous solution.