Green synthesis of photocatalyst hydroxyapatite doped TiO2/GO ternary nanocomposites for removal of methylene blue dye

Waste water treatment due to dyes is always a challenge. The present work focuses on nano Hydroxyapatite (nHAp) synthesis from waste oyster shells, a biogenic source composed of calcium carbonate. nHAp is used in various biomedical fields because of its bioactive and biocompatible material, as well as in the field of waste water treatment. On the other hand, semiconductor metal oxide like Titanium dioxide (TiO2) and Graphene oxide (GO) were chosen to show an effective photocatalytic performance with a synergistic effect. nHAp alone has poor adsorption for dye removal and its efficiency was increased by doping it with TiO2 and forming a composite with GO to treat Methylene Blue (MB) dye which is a common effluent. The synthesized composites were characterized by using Fourier Transform Infra Red (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDS) techniques to identify the purity and size of the composites. Ultra Violet (UV)-visible studies indicates that nHAp/TiO2/GO composites act as ternary nano photocatalyst and degrades the dye present in waste water at different time intervals from 30 mins to 360 mins. From the absorbance values, it was observed that 98% effective removal of MB dye and the first order rate constant is calculated. Highly interesting fact that prepared ternary nanocomposites compared with other individual species and metal oxides; it exhibits an increased affinity for dye removal by adsorption along with improved photocatalytic performance. The ternary composites exhibited a moderate inhibition zone, at the concentration 500 µg of strain E. coli and S. aureus which are gram negative and positive bacteria respectively.