Photodegradation of Methylene blue and Rhodamine B using potato starch mediated zinc oxide nanoparticles and its calcium nanocomposites: Greener approach

Abstract

Zinc oxide is considered an effective photocatalyst for degradation of several organic contaminants found in waste-water. This work reports the biological synthesis of zinc oxide nanoparticles and its calcium nanocomposites to study the photocatalytic deterioration of two dyes, viz. Rhodamine B and Methylene blue, under natural sunlight. Nanoparti-cles were synthesized using zinc acetate and starch extracted from potato at pH 7–8. Potato starch acts as both a capping agent and a reducing agent. They were characterized spectroscopically via XRD, SEM, HR-TEM, EDAX and FT-IR techniques. Bean/spherical shaped ZnO NPs were obtained in the size range of 29–49 nm whereas calcium coating on ZnO decreased the particle size, i.e., 25–35 nm. Their photocatalytic ability to degrade Rhodamine B and Methylene blue was studied under natural sunlight and monitored using UV-Vis spectrophotometer. Synthesized ZnO nanoparticles and its calcium coated ZnO nanocomposites showed promising results in degradation of these dyes. Methylene blue was completely degraded in an hour at 8 mg of the sample. Although degradation of Rhodamine dye was slow, synthesized samples were effective catalysts as compared to the ones reported in the literature.