ABSTRACT
This paper reports the synthesis, characterization, and application of TiO2 and TiO2/Ag nanoparticles for use in photocatalysis, employing the herbicide methylviologen (MV) as a substrate for photocatalytic activity testing. At suitable metal to oxide ratios, increases in silver surface coating on TiO2 enhanced the efficiency of heterogeneous photocatalysis by increasing the electron transfer constant. The sol-gel method was used for TiO2 synthesis. P25 TiO2 was the control material. Both oxides were subjected to the same silver incorporation process. The materials were characterized by conventional spectroscopy, SEM micrography, X-ray diffraction, calculation of surface area per mass of catalyst, and thermogravimetry. Also, electron transfers between TiO2 or TiO2/Ag and MV in the absence and presence of sodium formate were investigated using laser flash photolysis. Oxides synthesized with 2.0 % silver exhibited superior photocatalytic activity for MV degradation.
Subject(s)
Paraquat/chemistry , Photolysis , Silver/chemistry , Titanium/chemistry , Water Purification , Catalysis , Coloring Agents , Kinetics , Light , Metals , Nanoparticles/chemistry , Oxides , X-Ray DiffractionABSTRACT
O objetivo deste trabalho foi avaliar os efeitos do espaçamento entre plantas na linha e da aplicação ou não de cama-de-frango em cobertura no solo, na atividade antioxidante, teor total de fenóis e flavonóides em extrato etanólico e extrato aquoso quente de folhas de rosela (Hibiscus sabdariffa L.). Os tratamentos consistiram de cinco espaçamentos entre plantas (0,30; 0,35; 0,40; 0,45 e 0,50m) e do uso ou não de cama-de-frango em cobertura do solo, na dose de 10t ha-1, arranjados como fatorial 5x2, no delineamento blocos casualizados, com quatro repetições. Os teores de flavonóides e fenóis totais aumentaram no extrato etanólico (18 por cento e 11 por cento, respectivamente) e no extrato aquoso quente (16 por cento e 11 por cento, respectivamente) entre a aplicação ou não de cama-de-frango em cobertura no solo. A atividade antioxidante foi influenciada significativamente pelo método de obtenção dos extratos, sendo no extrato etanólico 263 por cento maior que o resultado obtido para o extrato aquoso quente.
The purpose of this paper was to analyze the effects of plant spacing within rows by means of applying or not applying chicken-manure to the soil cover in the antioxidant activity, total phenolic and flavonoids in ethanolic leaves extract and hot aqueous extract of roselle. The treatments consisted of five different spaces between plants (0.30, 0.35, 0.40, 0.45 and 0.50m) and the use or non-use of chicken litter broadcasted on soil surface at 10 ton ha-1, in a 5x2 factorial arrangement in a randomized block design with four replications. The flavonoids levels and total phenolic increased on ethanolic leaves extract (18 percent and 11 percent, respectively) and hot aqueous extract (16 percent and 11 percent, respectively) between applying or not applying chicken-manure to the soil cover. Antioxidant activity was significantly influenced by the way of obtaining extracts, being the ethanolic extract 263 percent higher than the results obtained by the hot aqueous extract.
