Domestic food waste chicken eggshells can produce naturally abundant protein-based eggshell membranes (ESMs), which is used as a less-explored source of sulphur to synthesize hexagonal CdS nanoparticles (NPs) under 365 nm (UVA) light irradiation. The perspective of CdS NPs synthesis in the way of UVA light irradiation soakage technique using ESM is distinctive compare to other traditional methods. Various physicochemical methods were employed to validate the formation of CdS NP using ESM assisted process. The obtained NPs exhibit an average particle size of ~5 nm as obtained from the transmission electron microscopy study. The capability of the synthesized CdS NPs was further explored in the catalysis reaction for the decomposition of KMnO4, considered as toxic Mn VII (violet) ion source at room temperature. The degradation results as monitored by UV-Vis spectrophotometry analysis confirms the CdS NPs exhibit excellent catalytic activity towards the reduction of KMnO4, toxic Mn VII (violet) ion to MnO2 as non-toxic Mn IV (brownish yellow) ion in aqueous solution (pH 7.0) at room temperature by 50 min. The KMnO4 decomposition reaction follows a pseudo-first-order reaction having the rate constant value of 1.9 x 10 -2 min -1 . This study encourages the potential use of natural waste materials for wastewater treatment.