The prominent water pollutants, Safranin (SF) and Eriochrome Black T (EBT) dye extensively used in plastic, leather, complexometric titrations, and textile industries, cause severe toxic impacts on the environment and human health. So, for their elimination, a cost-effective and sustainable hybrid of calcium oxide with reduced graphene oxide (rGO@CaO) was employed, synthesized using waste egg shells (precursor of calcium oxide), and thermal reduction of graphene oxide produced via modified Hummer's method. The sharp PXRD peaks confirmed the crystalline nature of the nanocomposite's pure and deformed spherical nanoparticles (20–40 nm). The removal of dyes was subsequently studied using the rGO@CaO nanocomposite (5–25 mg) at specific reaction conditions investigated (pollutant: 10–50 mgL-1, pH: 3–11, dark–sunlight). Under UV irradiation, the rGO@CaO nanocomposite demonstrated maximal degradation (SF: 97 % and EBT: 93 %) with 10 mg of catalytic dose at the initial dye concentration (10 mgL-1). The efficient photocatalytic efficacy of the rGO@CaO nanocomposite was supported by its small size, large surface area (48.06 m2g−1), higher negative zeta potential (-31.5 mV), and smaller bandgap (2.0 eV). Scavenger analysis revealed that holes, O2, and OH radicals play a crucial role in breaking the complex structure of SF and EBT. After degradation, safer metabolites developed, which was verified by LC-MS analysis. In conclusion, hybrid rGO@CaO nanocomposite is an efficient catalyst for industrial applications with broad potential due to its stability, higher charge separation, cost-effectiveness, and increased reusability (n = 8).