Strontium Hexaferrite / Zinc Oxide Nanocomposites: Study on Photocatalytic Discoloration of Orange II Dye
Orange II is an azo dye widely used in textile industry. Its discharge into water bodies is harmful to the ecosystem and causes health hazard. The removal of organic pollutants from wastewater by photocatalyzed discoloration processes has been thoroughly studied. Notwithstanding, it would be interesting to support the catalyst on magnetic materials in order to facilitate its recovery. In the present work, catalytic discoloration of Orange II was performed using zinc oxide nanopowder in aqueous suspension and novel composites of zinc oxide supported on magnetic materials. We report a one-step method for the synthesis of composites, by precipitation of zinc oxide on hard strontium ferrites, that may improve catalyst remotion from water without decreasing its catalytic performance. Composites were structural and magnetically characterized. The discoloration process, scanned by spectrophotometry for six hours, followed a first order kinetics, with a reaction rate constant of 0.0142 1/min and a half-life of 49 min for strontium ferrite/zinc oxide in neutral media at 25 °C. Orange II significant adsorption on catalysts was discarded. Composites, that showed great stability in aqueous suspension and excellent photocatalytic properties compared with zinc oxide, can be easily removed from water by magnetic decantation, with a significant recovery factor (70%).