Silver nanoparticles effect on Artemia salina and Allium cepa organisms: influence of test dilution solutions on toxicity and particles aggregation.

The objective of this study was to evaluate the effects of AgNPs on Artemia salina and Allium cepa, evaluating the influence of the dilution solutions on the particle behavior. The AgNPs were synthesized by chemical reduction of AgNO3 (3 and 5 mmol L-1) with sodium borohydride and stabilized with PVA (polyvinyl alcohol) and CMC (sodium carboxymethyl cellulose). The toxicity of AgNPs was evaluated in Artemia salina (mortality) using Meyer's solution as a diluent and in Allium cepa (chromosomal aberrations) using reconstituted hard water. AgNPs showed characteristic molecular absorption bands. Particles with CMC presented hydrodynamic radius between 4 and 102 nm and with PVA between 7 and 46 nm. The studied dispersions were toxic to A. salina species. Meyer's solution, used as dilution water in the test, caused precipitation of Ag+ and also caused changes in CMC-stabilized AgNPs, changing the shape of the nanoparticles by depositing precipitates on their surface. These changes make the results of toxicity difficult to interpret. AgNPs stabilized with PVA remained unchanged. AgNPs affected cell division and caused the appearance of chromosomal aberrations on A. cepa. Higher numbers of chromosomal aberrations occurred in dispersions with smaller particle diameters (AgNPs3-PVA and AgNPs5-PVA, without dilution). In the studied conditions the dispersions were toxic to the tested organisms, the concentrations of precursors and the type of stabilizer used influenced the particle size and toxicity. In the test with A. cepa, the reconstituted hard water did not cause changes in the dispersions of AgNPs, whereas for A. salina the Meyer solution promoted aggregation of the particles and precipitation, in the dispersions stabilized with CMC, thus changing the samples.

Adsorption of naturals hormones estrone, 17ß-estradiol, and estriol by rice husk: monocomponent and multicomponent kinetics and equilibrium.

In the present study, the use of the rice husk biomass as an alternative biosorbent for treating the estrone, 17 ß-estradiol, and estriol hormones in monocomponent and multicomponent systems was investigated. The high-performance liquid chromatography technique (HPLC-UV) was applied in order to quantify the hormones, validating this method according to ANVISA and INMETRO. The biosorbent presented functional groups typical of cellulose, hemicellulose, lignin, and proteins, with an amorphous, fibrous, and porous surface. The best performance was obtained with a neutral pH and at room temperature (25[Formula: see text]C). The equilibrium times in batch systems were 60 min for the estrone, and 120 min for 17 ßestradiol and estriol. The monocomponent kinetics of adsorption of estrone and estriol were adequately described by the pseudo-first-order model, whereas for the 17 ß estradiol both pseudo-first-order and pseudo-second-order models well described the experimental data. For the multicomponent system, the kinetics of adsorption was appropriately represented by the pseudo-first-order model, demonstrating that the number of active sites was the limiting factor of the process. The monocomponent adsorption isotherms were adequately fitted by the Langmuir model, reaching adsorption capacities of 2.698, 1.649, and 0.979 mg g-1 for the estrone, 17 ßestradiol, and estriol hormones, respectively. The ternary isotherm models did not represent the experimental data, indicating that there was no competition among the hormones. The reactions presented favourable and spontaneous characteristics. The rice husk biomass showed a great potential as an adsorbent when treating effluents contaminated with hormones.

Potential of the Moringa oleifera saline extract for the treatment of dairy wastewater: application of the response surface methodology.

In this work, the coagulation/flocculation/sedimentation treatment of dairy wastewater samples was investigated through serial factorial designs utilizing the saline extract obtained from Moringa oleifera (Moringa) as a coagulant. The sedimentation time (ST), pH, Moringa coagulant (MC) dose and concentration of CaCl2 have been evaluated through the response surface methodology in order to obtain the ideal turbidity removal (TR) conditions. The empirical quadratic model, in conjunction with the desirability function, demonstrated that it is possible to obtain TRs of 98.35% using a coagulant dose, concentration of CaCl2 and pH of 280 mg L-1, 0.8 mol L-1 and 9, respectively. The saline extract from Moringa presented its best efficiency at an alkaline pH, which influenced the reduction of the ST to a value of 25 min. It was verified that the increase in the solubility of the proteins in the Moringa stimulated the reduction of the coagulant content in the reaction medium, and it is related to the use of calcium chloride as an extracting agent of these proteins. The MC proved to be an excellent alternative for the dairy wastewater treatment, compared to the traditional coagulants.

Alternative adsorbents applied to the removal of natural hormones from pig farming effluents and characterization of the biofertilizer.

Pig farming has a very strong economic importance in Brazil. The residues from this activity are applied to the soil because of their excellent characteristics as biofertilizers. The present study aimed at studying the estrone, 17ß-estradiol, and estriol natural hormones, emerging contaminants present in this type of residue that are not mentioned in the current legislation. The characterization of the pig farming effluent presented high concentrations of hormones (mg L-1). The objective was to apply the biosorbents to the removal of the hormones in batch systems directly in the manure heaps without affecting the potential of the effluent as a fertilizer. It was verified that the adsorption of hormones using the rice husk biomass in natura and soybean hull in natura, abundant alternative adsorbents, presented a good capacity of removal of hormones. The presence of the organic materials (rice husk and soybean hull) caused few alterations in the biofertilizer characteristics, demonstrating that these adsorbents present a potential of application in batch treatment systems, with possible applications related to pig farming effluents containing natural hormones.

Adsorption of reactive blue BF-5G dye by soybean hulls: kinetics, equilibrium and influencing factors.

The textile industry is known for the high use of chemicals, such as dyes, and large volumes of effluent that contaminate waters, a fact that has encouraged research and improved treatment techniques. In this study, we used unprocessed soybean hulls for the removal of reactive blue BF-5G dye. The point of zero charge of soybean hulls was 6.76. Regarding the speed of agitation in the adsorption process, the resistance to mass transfer that occurs in the boundary layer was eliminated at 100 rpm. Kinetics showed an experimental amount of dye adsorbed at equilibrium of 57.473 mg g(-1) obtained under the following conditions: dye initial concentration = 400 mg L(-1); diameter of particle = 0.725 mm; dosage = 6 g L(-1); pH 2; 100 rpm; temperature = 30 °C; and duration of 24 hours. The pseudo-second order best showed the dye removal kinetics. The adsorption isotherms performed at different temperatures (20, 30, 40 and 50 °C) showed little variation in the concentration range assessed, being properly adjusted by the Langmuir isotherm model. The maximum capacity of dye adsorption was 72.427 mg g(-1) at 30 °C. Since soybean hull is a low-cost industrial byproduct, it proved to be a potential adsorbent for the removal of the textile dye assessed.