Photochemical degradation of Congo red using magnesium doped Hydroxyapatite-Graphitic carbon nitride composite

Hydroxyapatite (HAP), Ca10(PO4)6(OH)2 is a prominent material for biomedical applications. It is used as an effective adsorbent for the removal of heavy metals and dyes from contaminated soil and water. Graphitic carbon nitride (GCN) is a two-dimensional (2D) metal-free semiconducting material with the band gap energy of 2.7 eV. The important attributes of GCN include high thermal, physical, chemical, and photochemical stability. Its ability to absorb visible light irradiation makes it an attractive photocatalyst. However, faster recombination of photo induced electrons and holes, low specific surface area are some of the issues that limit its utility. Doping, formation of composites and development of heterojunctions have been shown to be promising to improve the photocatalytic efficiency of GCN. In this perspective, the present study aims at to synthesize HAP/GCN and Mg-doped HAP/GCN composites by chemical precipitation followed by hydrothermal treatment. Scanning electron microscopy (SEM), energy dispersive X-ray (EDS) analysis, X-ray diffraction (XRD) measurement and Fourier transform infrared (FT-IR) spectroscopy were used to assess the morphological features, elemental composition, structural characteristics and nature of functional groups, respectively. The efficiency of HAP/GCN and Mg-HAP/GCN towards the degradation of Congo red dye was determined using a photoreactor under visible light irradiation. The study concludes that HAP/GCN is very effective in removing CR both by adsorption as well as by photocatalytic degradation.