TiO2-containing cement pastes and mortars: Measurements of the photocatalytic efficiency using a rhodamine B-based colourimetric test

In this study, two solar slurry photocatalytic reactors i.e., batch reactor (BR) and batch recycle reactor with continuous supply of inert gas (BRRwCG) were developed for comparing their performance. The performance of the photocatalytic reactors were evaluated based on the generation of hydrogen (H2) from water containing sodium sulfide (Na2S) and sodium sulfite (Na2SO3) ions. The photoreactor of capacity 300 mL was developed with UV–vis transparent walls. The catalytic powders ((CdS/ZnS)/Ag2S + (RuO2/TiO2)) were kept suspended by means of magnetic stirrer in the BR and gas bubbling and recycling of the suspension in the BRRwCG. The rate constant was found to be 120.86 (einstein−1) for the BRRwCG whereas, for the BR it was found to be only 10.92 (einstein−1). The higher rate constant was due to the fast desorption of products and suppression of e−/h+ recombination.