Sergio Pérez-Sicairos

Effect of Nd3+ doping on structure, microstructure, lattice distortion and electronic properties of TiO2 nanoparticles

Abstract Doped and undoped TiO2 nanoparticles were prepared by Stober method and thermally treated at 600 °C. The effect of Nd3+ ion on the structure and microstructure of anatase-phase TiO2 nanocrystals was studied by Rietveld refinement method using X-ray powder diffraction data. Bond lengths, bond angles, and edges distances were analyzed. The phase formation was confirmed by high-resolution transmission electron microscopy. The adjustment of Ti-O bond length induced by the addition of Nd3+ ions, reduced the octahedral distortion and altered the octahedral array in the anatase-phase TiO2 nanocrystal. The changes of structure and microstructure were mainly observed for TiO2 nanoparticles doped with 0.1 at.% of Nd3+ ions and attributed to the cationic substitution of Ti4+ ions which promoted changes in the density of states and gap band of TiO2. The dopant insertion resulted in a better structural stability of the nanocrystals that enhanced their charge transference and photocatalytic efficiency.

PHOTOCHEMICAL DEGRADATION OF NITROBENZENE BY S2O8 -2 IONS AND UV RADIATION

In this work nitrobenzene (NB) degradation was studied through an advanced oxidation process (AOP) by using a photochemical reactor and two kinds of oxidizing reagent: potassium persulfate (K 2 S 2 O 8 ) and sodium persulfate (Na 2 S 2 O 8 ), to promote generation of HO • radicals. It was determined the effect of different parameters on nitrobenzene degradation, such as: wavelength of UV lamps, concentration of oxidizing reagent, type of oxidizing reagent and number of UV lamps in the reactor. By using UV lamps with radiation wavelength of 254 nm, NB degradation reached almost 100 % meanwhile, irradiating at 350 nm resulted in < 35 % degradation. For experiments using UV lamps of 254 nm, the reaction rate increased with the radiant energy, being higher by using four UV lamps than two UV lamps for a reaction time of 60 min. The specific energy consumption for two UV lamps showed the lowest value being of 2626.0 KW.h/Kg of NB degraded.

New method of synthesis of sulfonated polyethersulfone (SPES) and effect of pH on synthetic gray water filtration performance by negatively charged SPES/PS UF membranes

AbstractAll polymeric membrane-based water purification systems suffer serious membrane fouling problem due to protein adsorption and bacteria attachment. Increasing the negative surface charge density of the membrane will increase its hydrophilicity; this would hinder the colloidal and bacteria attachments. This can be achieved through inclusion of sulfonated group () as part of the moiety of the polymer that made up of the membrane. In this work, a new method of synthesis of sulfonated polyethersulfone (SPES) is reported. In this method, concentrated sulfuric acid was used as the solvent for polyethersulfone (PES) and also as the source of SO3(g) when the PES/H2SO4 solution was heated to 90°C. The degree of sulfonation of the polyethersulfone polymer was assessed by ATR-FTIR spectra and ion-exchange capacity determination. Nine polysulfone membranes, containing various amounts of SPES, were fabricated via phase inversion process with a continuous membrane casting machine. The membranes were also charact...

Wastewater treatment via electrochemically generated ferrate and commercial ferrate

AbstractThis paper presents the results of wastewater treatment using electrochemically generated ferrate and commercial potassium ferrate (supplied by Sigma–Aldrich). Two electrolytes were used for the electrochemical generation of ferrate; NaOH at 8.0, 10.0, and 12.0 M and KOH at 12.0 M, the ferrate solutions produced were used for the treatment of wastewater samples from a wastewater treatment plant. The experimental results of removal of organic matter in wastewater by electrochemically generated and by commercial ferrates were measured. In this work, the pH, chemical oxygen demand, and turbidity were determined for the treatment of wastewater using ferrate from different source. Experimental results revealed that the treatment with electrochemically generated ferrate was more efficient than the treatment with commercial ferrate. The commercial ferrate was found to be chemically unstable when dissolved in water prior to its application on wastewater treatment. The concentrations of potassium and sodiu...