Influence of PVP surfactant on the morphology and properties of ZnO micro/nanoflowers for dye mixtures and textile wastewater degradation

• Published in: Materials chemistry and physics 2018-06, Vol.212, p.35-43
• Main Authors: Lam, Sze-Mun, Kee, Ming-Wei, Sin, Jin-Chung
• Format: Article
• Language: English
• Subjects: Ammonia; Biochemical oxygen demand; Chemical oxygen demand; Chemical synthesis; Crystal growth; Crystal structure; Dye; Dyes; Energy transmission; Field emission microscopy; Fourier transforms; Morphology; Nanostructure; Nanostructured materials; Nitrogen; Organic chemistry; Photocatalysis; Photodegradation; Photoluminescence; Polyvinylpyrrolidone; Process parameters; PVP; Scanning electron microscopy; Solid suspensions; Surfactants; Textile wastewater; Transmission electron microscopy; Turbidity; X-ray diffraction; Zinc oxides; ZnO
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2018.03.002

Flower-like ZnO micro/nanostructures were successfully prepared using a polyvinylpyrrolidone (PVP)-assisted co-precipitation route and characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), fourier transform infrared (FTIR) and photoluminescence (PL) spectroscopy. Smaller sizes of ZnO micro/nanoflowers were synthesized with different amounts of PVP as surfactant. Possible morphology evolution and formation mechanism of the flower-like micro/nanostructures were postulated. Concentrations of PVP in the reaction mixtures served as key role for morphology-controlled synthesis of ZnO as PVP can assist the oriented crystal growth during the synthesis. The as-synthesized ZnO samples prepared at 12.5 mg/mL PVP displayed higher photoactivity for the simultaneous degradation of methyl orange and methyl green mixtures. The photocatalytic tests also indicated that process parameters such as the initial dye concentration and solution pH exerted their individual influences on the dye mixtures degradation. Under determined experimental conditions, 94.1% chemical oxygen demand (COD) removal of dye mixtures was attained after 240 min of reaction. The ZnO photocatalytic degradation of real textile wastewater was then evaluated and a lower COD removal efficiency (∼75%) was observed at similar treatment duration. Other real textile wastewater quality parameters of biochemical oxygen demand (BOD5), turbidity, total suspended solid (TSS), colour, ammoniacal nitrogen (NH3-N) and pH were also investigated. •PVP was used as surfactant in synthesizing ZnO micro/nanoflowers.•ZnO micro/nanoflowers properties were pivotally affected by the synthesis method.•Growth mechanism of flower-like ZnO micro/nanostructures was suggested.•Excellent photodegradation of dye mixtures and textile wastewater were evidenced.