Abstract
The present work aims to evaluate the activity of semiconductor oxides (TiO 2 , Nb 2 O 5 and ZnO) supported on NaA and NaY zeolites, as well as their synergistic effect on Reactive Blue Dye (RB250) photodegradation process. Prior to deposition, TiO 2 particles size was reduced by ultrasonic scattering followed by filtration. The particles on the filtrate were used to conduct the experiments. The semiconductors were immobilized in concentrations of 2.5, 5 and 10% (w w -1 ) and the photocatalytic tests were performed at catalyst concentrations of 1 and 2 g L -1 . Moreover, supported catalysts were characterized by XRD, textural analysis, zero point of charge and temperature programmed desorption of NH 3 . A comparison between the supported catalysts showed high activity for the ones supported with ZnO and TiO 2 . Zeolite NaY has broader opened channels than NaA, which reduces the dye molecules blockage, and, as a result, increased the catalyst activity. A higher concentration of supported catalysts (2 g L -1 ) provides greater photocatalytic activity, while higher concentration of semiconductors immobilized on supports does not present significant differences.
Highlights
According to the United Nations EducationalWorld, Scientific and Cultural Organization (Unesco, 2015), the water consumption increases two times faster than the population
The chemicals used were: oxalic acid (Nuclear 0.5 mol); zinc nitrate; niobic acid (HY-340 CBMM with 76.2% Nb2O5); titanium dioxide (Kronos 100% Anatase); NaOH (Vetec); HNO3 (Vetec), reactive blue dye (RB250 - Donated by Sintex dyeing) and Zeolites NaA and NaY
For ZnO catalysts, the precursor salt used was an aqueous solution of zinc nitrate
Summary
Scientific and Cultural Organization (Unesco, 2015), the water consumption increases two times faster than the population. The reactive ones are detectable at concentrations above 5 μg L-1 (Brites-Nóbrega, Santana, & Fernandes-Machado, 2011). Even though the concentration is low, it could block the light penetration, unbalancing the aquatic ecosystem and exhibiting a high BOD and COD load (Smith, 2003). Adsorption and coagulation processes have good efficiency in removing pollutants from water, just like filtration. Those techniques generate secondary pollutants, which needs post treatments or specific destinations (Gaya & Abdullah, 2008), increasing the time operation and the process cost
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