Sheila Cristina Canobre

Use of pyrolyzed paper as disposable substrates for voltammetric determination of trace metals

The possibility of using pyrolyzed paper as disposable working electrodes for trace metals determination is reported for the first time. A small piece of pyrolyzed paper (0.7×0.7cm) was positioned at the bottom side of the electrochemical cell using a rubber O-ring, which defined the electrode area (0.48cm; 0.18cm2). A large number of electrodes can be obtained from a single piece of standard dimensions (2.5cm×7.5cm) of paper, therefore minimizing the cost per unit. The electrochemical performance of the pyrolyzed paper was demonstrated by cyclic voltammetry, electrochemical impedance spectroscopy and by the determination of Zn, Cd, and Pb by square-wave anodic stripping voltammetry. The unmodified pyrolyzed paper showed excellent performance for Pb and Cd detection (LOD =0.19 and 0.16 ppb, respectively). In the presence of Bi3+(in-situ film formation), the simultaneous determination of Zn, Cd and Pb was also possible (LOD=0.26, 0.25, and 0.39 ppb, respectively).

Influence of different fuel agents on the combustion synthesis of the nanostructured Li1.05Mn2O4 oxide

In this work nanostructured Li1.05Mn2O4 oxide was obtained by Solution Combustion Synthesis (SCS) using three different fuel agents in order to obtain a unique phase with a crystalline cubic structure belonging to the Fd3m spatial group. The phase of interest could be obtained, following the order: glycine (at 600 °C for 2 h) < urea (at 750 °C for 2 h) < maleic anhydride (at 750 °C for 4 h), with crystallite size in the range from 4.6 to 9.7 nm (nanometric character) and the unit cell parameter of the calcined samples at 750 °C for 2 h were similar to the JCPDS 35-0782 with cubic structure (a = 8.247 A). Charge and discharge tests from the samples obtained by glycine fuel (at 750 °C for 4 h) presented the highest experimental specific capacities of 115 mA h g-1 and 92% of retention after 10 cycles.

Synthesis of Co-Al-Cl LDH by cathodic material reprocessing from cellular phone batteries

The aim of this paper was the recovering of the cathodic material from discarded lithium ion batteries for obtainment of the lamellar double hydroxides (LDHs) by the co-precipitation method at variable pH in HCl and H2O2 1:1 (v/v) acid solution containing Co and Al (extracted from cathodic material composed of LiCoO2 and aluminum foil). These metals were precipitated in LiOH at pH 9 or 11, or NH4OH at pH 9 and submitted to the hydrothermal treatment (HT) to improve the structural organization of the LDHs lamellae. After precipitation, the resulting solids were structurally characterized by XRD for phase identification and calculation of the unit cell parameter, thermally by TGA for the identification of the mass loss and morphologically by SEM. The sample obtained by precipitation with LiOH at pH 11 / hydrothermal treatment showed diffraction peaks similar to hydrotalcite, morphological and thermal characteristics similar to the pattern Co-Al-Cl LDH obtained by co-precipitation at constant pH 8.

Utilização de hemiceluloses catiônicas, obtidas a partir do aproveitamento da palha de milho, associadas com tanino para o tratamento de efluentes de lavanderia industrial

Elaine Angélica Mundim Ribeiroa, Fúlvio Rafael Bento de Souzaa, Fábio Augusto do Amarala, Guimes Rodrigues Filhoa,*,#, Raquel Maria Ferreira de Sousaa, Júlia Graciele Vieiraa, Talita Ferreira de Rezende Costaa, José Pedro Thompson Juniora, Rosana Maria Nascimento de Assunçãob e Sheila Cristina Canobrea Instituto de Química, Universidade Federal de Uberlândia, Campus Santa Mônica, 38.400-902, Uberlândia – MG, Brasil Faculdade de Ciências Integradas do Pontal, Universidade Federal de Uberlândia, Campus do Pontal, 38302-000, Ituiutaba – MG, Brasil

Pechini Synthesis of Nanostructured Li1.05M0.02Mn1.98O4 (M = Al3+ or Ga3+)

Doped Li1.05M0.02Mn1.98O4 (M = Ga3+ or Al3+) were prepared by Pechini synthesis using lithium and manganese acetates, citric acid, ethylene glycol, and the respective oxide or acetate of the doping ions in molar ratios of 2.00 (Mn1.98 + M0.02) to 1.05 Li. The TGA/DTA of the precursor gels showed weight loss/energy relative to crystallization below 450 oC. From the XRD, a single cubic phase (Fd3m) was identified for the all-doped or undoped oxides after only 2 h calcination. The unit cell parameters a for both aluminum- and gallium-doped oxides calcined at 750 °C for 2 h (8.212 A and 8.210 A, respectively) were higher than that for the undoped oxide (8.199 A). The crystallite sizes ranged from ~ 20 nm to 70 nm, conferring nanometric character. The specific capacities decreased in order: Cdischarge (Li1.05Mn2O4) >Cdischarge (Li1.05Ga0.02Mn1.98O4) >Cdischarge (Li1.05Al0.02Mn1.98O4), but with increasing capacity retention for the doped samples.