Photocatalytic degradation of textile dyes using phycosynthesised ZnO nanoparticles

Abstract

Phycosynthesis of ZnO nanoparticles (ZnO NPs) using a single-step process, from biomolecules present in the cyanobacterial extracts of Anabaena variabilis ARM 441 was carried out and analysed for photocatalytic degradation of textile dyes. Bioactive components of algal extracts identified by GC–MS and NMR (13C and 1H NMR) spectroscopy, reveals 21 different compounds, among which n-hexadecanoic acid and 13 tetradecenal had properties of reducing and capping agent required in the synthesis of ZnO NPs. Microscopic investigation of particle size and zeta potential confirmed the formation of hexagonal ZnO NPs with an average size of 33.31 nm. The EDX and XPS analyses established the chemical composition and high purity of ZnO NPs. The rietveld refinement studies of X-ray diffraction studies elucidated crystalline and wurtzite phase of ZnO NPs. Pore size (11.551 nm), surface area (38.718 m2/g) and pore volume (0.1633 cc/g) were studied by BET analysis. The photocatalytic degradation of brilliant green (BG) and indigo carmine (IC) dyes in aqueous solution by ZnO NPs was 98.07% and 80.8% for BG and IC, respectively, which followed first-order kinetics, suggesting that ZnO NPs are capable of degrading harmful and toxic chemical dyes that persists in the environment.