Sunlight-driven photocatalytic degradation of methylene blue using ZnO nanowires prepared through ultrasonication-assisted biological process using aqueous extract of Anabaena doliolum

Abstract

Abstract Zinc oxide nanowires (NWs) were prepared by the ultrasonication-assisted biological method using an aqueous extract of cyanobacterium Anabaena doliolum. The peculiar properties of prepared NWs were investigated with UV-VIS spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectroscopy. Further, the ZnO NWs were evaluated for the kinetics of adsorption and sunlight-driven photocatalytic degradation of methylene blue (MB). Ultrasonication of reaction mixture considerably trimmed-down the time inevitably required for the synthesis and minimized the formation of particle clusters. Synthesized material displayed loosely aggregated and anisotropic NWs with a hexagonal crystalline structure matching with corundum phase of ZnO. The prepared ZnO NWs showed 3.20 eV bandgap energy and crystal size as 27.71 nm and 14.20 nm as determined by the Schere method and Williamson-Hall method, respectively. A complete (100%) photocatalytic degradation of MB (10 mg L1) was achieved in 72 h under sunlight irradiation without external source of UV irradiation. The adsorption on prepared ZnO NWs and subsequent photocatalytic degradation of MB followed the pseudo-first-order rate kinetics. The prepared ZnO NWs could find application in the removal of organic dyes from polluted water bodies under natural sunlight without the requirement of an external source of UV radiation.