Photo-Fenton Process Using Fe(III) Ions from Modified Sugarcane Bagasse for Reactive Black 5 Dye (RB5) Removal

Brazil is one of the largest generators the sugarcane bagasse, this kind of biomass has already shown efficiency related to its in natura adsorption potential (when physically or chemically activated), it can also be used to remove contaminants from water in methods such as advanced oxidative processes. In this study, chemical modifications were carried out in sugarcane bagasse to enable its application in photo-Fenton processes for the degradation of reactive black 5 dye. The materials were chemically activated through immersion in Fe(III) solution for different periods of time: 3, 6, 9, 12, 24, 48 and 96 h; and were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), zeta potential analysis, internal surface area and leached metal quantification. The results showed the cellulose structure, which is predominant in the sugarcane bagasse it was not considerably modified after activation with FeCl3 and evidence of the presence of Fe(III) ions on the surface of the studied material. The degradation efficiency (after 5 min and using 11.5 mg L-1 hydrogen peroxide) for the activated materials was respectively: 55.85%, 49.44%, 71.22%, 92.87%, 88.16% and 98.02%, considering the decrease of the band related to the chromophore group (598 nm). DOI: http://dx.doi.org/10.17807/orbital.v13i2.148

Effect of pH Variation on Synthesis and Photocatalytic Activity of Bi2Fe4O9

The Pechini synthesis method, presents chemical homogeneity as its main advantage, enabling the desired phase to be obtained. This synthesis usually occurs at pH 7. In this study, Bi2Fe4O9 was synthesized using the Pechini method at different pHs (pH= 3, 5, 7, 8, 10 and 12) to verify if the pH conditions can influence in its photocatalytic activity. The materials obtained at different conditions were characterized by using X rays diffraction (XRD), UV/Vis diffuse reflectance and scanning electron microscopy by field emission (MEV/FEG).It was possible to synthesize the material under conditions already mentioned, but it was not observed significant differences in the chemical structure of the obtained materials from the characterization techniques. However, they presented a small variation in the band gap values, morphological aspects and photocatalytic activities. All the materials proved to be a good semiconductor, maintaining high degradation rates. The photocatalyst synthesized at pH 3 (BFO - 1) presented a degradation rate of approximately 95% for the group chromophore and 93% for the aromatic group of the structure of the tartrazine yellow dye, proving to be a promising photocatalyst for industrial applications. This result is particularly important because BFO – 1 showed higher catalyst activity since the chromophore of the aromatic group was degraded. The highlights of this study is the synthesis of Bi2Fe4O9 performed at pH=3, since it reduces the quantity of reagents comparing to the conventional Pechini method and presented high photocatalytic activity. DOI: http://dx.doi.org/10.17807/orbital.v13i2.148

Oxido de niobio enxertado sobre a superficie da silica gel : preparação e utilização na construção de eletrodos modificados

Orientador : Yoshitaka GushikemTese (doutorado) - Universidade Estadual de Campinas, Instituto de QuimicaDoutorad

Estudo eletroquimico de corantes organicos com propriedades redox imobilizados sobre o fosfato de zirconio

Orientador: Yoshitaka GushikemDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de QuimicaMestrad

Carbon ceramic electrodes: preparation parameters, properties and application as electrochemical sensors

The electrodes based on carbon ceramic (CCE) preparation has been improved during last decades, increasing the potential for application of electrodes and electrochemical sensors. The interest on these materials are principally related to their features such as renewable surface, high thermal stability and mechanical strength. This review sets out some of the key aspects related to CCEs, such as the preparation parameters, which directly influence in their electrochemical properties, besides some applications such as electrochemical sensors. Among the preparation factors stand out the precursor characteristic, carbon material type, precursor proportion, catalyst and carbon material. The CCE modification with electron mediator species can broaden the application as electrochemical sensors as increasing the selectivity and sensitivity

SIMULTANEOUS DETERMINATION OF SULFAMETHOXAZOLE AND TRIMETHOPRIM IN PHARMACEUTICAL FORMULATIONS BY SQUARE WAVE VOLTAMMETRY

Objective: To develop a simple, fast and low-cost square wave voltammetric (SWV) method for simultaneous determination of sulfamethoxazole (SMX) and trimethoprim (TMP) using a glassy carbon electrode (GCE).Methods: The SWV parameters were optimized by 2Results: Two well defined oxidation peaks were obtained at 0.96V (SMX) and 1.12V (TMP) in Britton–Robinson buffer (pH 6.0). Under optimized conditions, SWV measurements showed excellent linear response, ranging from 5.5x10-5 to 3.95x10-4 mol L-1 (R=0.9971) and 1.05x10-5 to 1.04x10-4 mol L-1 (R=0.9974) for SMX and TMP, respectively. The detection limits were found to be 8.52x10-6 mol L-1 for SMX and 9.31x10-7 mol L-1 for TMP.Conclusion: The proposed method was successfully applied to the determination of these antibiotics in commercial pharmaceutical formulations (tablets, oral suspension and injection), without any sample pretreatment. The obtained results are in good agreement with that obtained by the standard HPLC method at a 95% confidence level.Â

Eletrodos de carbono cerâmico: parâmetros de preparação, propriedades e aplicações como sensores eletroquímicos.

A preparação de eletrodos a base de carbono cerâmico (ECC) tem sido aprimorada durante as últimas décadas, aumentando o potencial de aplicação desses eletrodos como sensores eletroquímicos. O interesse nestes materiais está principalmente relacionado às suas características tais como superfície renovável, alta estabilidade térmica e resistência mecânica. Nessa revisão apresentam-se alguns dos principais aspectos relacionados aos ECCs, tais como os fatores de preparação os quais influenciam diretamente nas propriedades eletroquímicas dos mesmos e algumas aplicações como sensores eletroquímicos. Dentre os fatores de preparação destacam-se a característica do precursor, o tipo de material de carbono além da proporção entre precursor, catalisador e material de carbono. A modificação do ECC com espécies mediadoras de elétrons pode ampliar a gama de aplicações como sensores eletroquímicos já que estes aumentam a seletividade e a sensibilidade