The characteristics of BiOCl/Plaster of Paris composites and their photocatalytic performance under visible light illumination for self-cleaning

Composites of Plaster of Paris (POP)-BiOCl (%) are prepared by adding BiOCl of 0%, 1%, 5%, 10% and 20% (by wt.) in the POP matrix. The band gap of the BiOCl powder is calculated about 3.31 eV. Resazurin (Rz) ink is used as an indicator to monitor the photocatalytic activity and self-cleaning property of POP-BiOCl (%) composites under the visible light and the resultant decolourisation of Rz ink is directly related to the photocatalytic performance of the material. Optical images of the coating of Rz ink over the surfaces of POP-BiOCl (%) composite pellets confirmed a steady color change from blue to pink within 60 min time duration. Finally, the rate of decolourisation of Rz ink was calculated by measuring the absorption at two wavelengths (581 nm and 630 nm). Digital photographic methods as well as UV–visible absorption studies are performed to examine qualitative and quantitative decolourisation of the Rz ink.