Exploring the potential utilization of gamma-irradiated waste eggshell powder as oil sorbents in natural rubber foams

A simple, green approach was developed to enhance the oil adsorption capacity of waste eggshell (WES) powder using gamma irradiation, with varying doses (0–10 kGy). Relevant properties (chemical composition, functional group, particle size, pore characteristics, thermal stability, morphology, and oil adsorption) of both non-irradiated and gamma-irradiated WES powders were determined and reported. The results indicated that gamma irradiation did not alter most properties of the WES powder, except for the pore characteristics and oil adsorption. Specifically, the WES powders irradiated with doses of 2 kGy and 10 kGy had substantially improved adsorption capabilities for engine oil and diesel, respectively, exhibiting approximately threefold enhancements compared to the non-irradiated ones. The suitable gamma-irradiated WES powder obtained from the first part was then incorporated into natural rubber foam (NRF) samples, with varying contents of 0–9 parts per hundred rubber (phr). Their respective properties, consisting of functional group, thermal stability, morphology, density, pore characteristics, and oil adsorption, were subsequently determined. The main findings revealed that the addition of 3–6 phr of gamma-irradiated WES powder increased the densities and oil adsorption capacities of the NRF/WES samples for both engine oil and diesel in comparison to those of neat NRF, while negligibly affecting other properties. The outcomes from this work suggested that gamma-irradiated WES powder not only improved the intended oil adsorption capacity of the NRF samples but also paved the way for alternative, greener approaches to replace the harmful chemical or energy-consuming procedures typically required for the modification/synthesis of similar substances or materials through gamma irradiation.