Construction of Waste Chalk Powder into mpg-C₃N₄-CaSO₄ as an Efficient Photocatalyst for Dye Degradation under UV–Vis Light and Sunlight

In this article, we present the synthesis of calcium sulfate nanoparticles (CaSO 4 NPs) from waste chalk powder by the calcination method. These CaSO 4 NPs were utilized for the construction of a mesoporous graphitic carbon nitride-calcium sulfate (mpg-C 3 N 4 -CaSO 4 ) photocatalyst. Synthesized materials were confirmed by several characterization techniques. The photocatalytic performance of the synthesized samples was tested by the degradation of methylene blue (MB) in the presence of both UV–vis light and sunlight. The efficiency of photocatalytic degradation of MB dye using the optimized mpg-C 3 N 4 -CaSO 4 -2 composite reached 91% within 90 min in the presence of UV–vis light with superb photostability and recyclability after five runs compared to individual mpg-C 3 N 4 and CaSO 4 NPs and reached 95% within 120 min under sunlight. Histotoxicological studies on fish liver and ovary indicated that the dye containing the solution damaged the structure of the liver and ovary tissues, whereas the photodegraded solution of MB was found to be less toxic and caused negligible alterations in their typical structure similar to the control group.