Development of green silicone rubber/waste sludge composites with Bi2O3 extracted from olive leaves for radiation shielding application

New fixable composite materials were developed based on silicone rubber reinforced with brine sludge as the main filler, and enhanced with bismuth oxide (Bi₂O₃) prepared from olive leaves as a natural and sustainable resource. For clarity, the samples are coded from SBB0 to SBB5, since (SBB) refers to Silicone Rubber + Brine Sludge + Bi₂O₃, starting with the reference sample (SBB0) without bismuth and going up to (SBB5) with the highest content (35% wt). The shielding properties of these composites were evaluated by measuring the attenuation coefficients such as Linear attenuation coefficient (LAC) and radiation shielding efficiency (RSE%) using photons from a wide range of energies, including low-energy X-rays (15-50 keV) as well as gamma rays (²⁴¹Am at 59.5 keV, ¹³³Ba at 81 and 356 keV, and ¹³⁷Cs at 661.7 keV). The results showed that increasing the Bi₂O₃ content significantly improved the performance of the samples, with SBB4 and SBB5 achieving shielding efficiencies of nearly 100% against X-rays up to 50 keV and over 95% against low-energy gamma rays at only 1 cm thick. This study also showed that increasing the thickness to 5 cm increased the efficiency at high energies, with the SBB5 efficiency reaching approximately 57% at 661.7 keV, compared to less than 10% for the reference sample (SBB0) with a thickness of 1 cm. These results demonstrate that these new composites, made from recycled and environmentally friendly materials, are good and safe compounds for radiation shielding applications in the medical and industrial fields.