Maria Augusta De Luca

A characterization study of xerogel silicapropylaniline powders

Abstract Silicapropylaniline nanometric materials with varying organic content were obtained using a sol–gel synthesis. By increasing the organic load, the scanning electron microscopy technique shows a slight increase in the average size of aggregated particles. N2 isotherms and positron annihilation lifetime spectroscopy measurements show that the average pore size decreases accompanied by a surface area reduction. FTIR thermal analysis was used to estimate the thermal stability of the organic phase and also to detect the presence of trapped organic groups in closed pores. From the organic coverage and surface area measurements the surface density of the immobilized organic molecules as well as the average intermolecular distance between them could be estimated.

Sodium Ferrate (IV) and Sodium Hypochlorite in Disinfection of Biologically Treated Effluents. Ammonium Nitrogen Protection against THMs and HAAs

The work described in this paper presents an evaluation of disinfection by-products generation in four different biological treatment plant effluents, making use of sodium hypochlorite and sodium ferrate (IV) at varying concentration and reaction time. Correlations between pH, chemical oxygen demand, total organic carbon, ammonium nitrogen, combined chlorine and trihalomethanes (THMs) and haloacetic acids (HAAs) were carried out. Disinfection by-products generation presented a direct relation with concentration and sodium hypochlorite reaction time. For the highest hypochlorite concentration employed (20 mg L−1) and highest reaction time (168 h), the THMs total did not exceed 312.96 μg L−1, a value that lies below the Brazilian emission standard for treated effluents (1 mg L−1 of chloroform). The THMs presented an inverse correlation with ammonium nitrogen, when inverse (R2 = 0.646; P < 0.001) and exponential (R2 = 0.707; P < 0.001) function were used. As per HAAs this same relation was observed for logarithmic (R2 = 0.0397 P < 0.001) and exponential (R2 = 0.508; P < 0.001) functions. The more nitrified the effluent, the bigger the chlorinated disinfection by-product generation. The disinfectant sodium ferrate (IV) does not lead to halogenated by-product formation.

Síntese eletroquímica do ion ferrato(VI)

The optimization of ferrate(VI) ion generation has been studied due to its favorable characteristics for application in several fields, including environmental quality control. The paper presents the best conditions for electrolytic generation of ferrate(VI) in alkaline media. An appropriate electrolyte was NaOH, 10 mol/L. Circulation of the electrolyte solution was important to avoid acidification close to the anode surface. An anode pre-cleaning with 10% HCl was more efficient than a cathodic pre-polarization. Among the distinct anode materials tested, pig iron showed the best performance, allowing up to 20 g/L of Na2FeO4, in 10 mol/L NaOH solution to be obtained, after 7 h of reactor operation, which is a concentration higher than those found in literature for alternative processes.

Microstructural orientation of isotactic polypropylene studied by computerized scanning eletron microscopy image analysis

We evaluate the orientation of microstructural elements of isotatic polypropylene (i-PP) before and after deformation using computerized “Quantikov” software analysis of Scanning Electron Microscopy (SEM) images. We observed that before deformation through uniaxial compression, the polymeric material doesn’t exhibit any significant orientation. After deformation at 1349 MPa the material clearly showed preferential orientation that was attested by the orientation axis seen between two petals of the rose of the number of intercepts. This effect was more pronounced after deformation at 2699 MPa.

Oxidação de microcistinas-LR em águas pelo íon ferrato(VI)

Algae toxins are becoming a severe problem in the water treatment industry, especially for human and animal consumption. Traditional treatment processes have failed in complying with water supply standards. Potassium ferrate(VI) is a powerful oxidant, disinfectant and, also, a coagulant. In this paper, the results of microcystin-LR oxidation by ferrate(VI) ion are presented. Kinetic and jar tests showed a average value of 0,012 min-1 for the pseudo first order reaction rate constant, for 100 and 200 µg.L-1 concentration of MC-LR. Ferrate(VI) dosages between 1.6 and 5.0 mg.L-1 suggest that water supply standards for MC-LR can be reached, which means that the oxidant may be employed as coadjuvant in water treatment.