Valorization of granite sludge in B2O3–Bi2O3 glass: optical, chemical characteristics and impact of gamma irradiation

Abstract The study presents a sustainable approach for recycling granite sludge waste by converting it into a glass containing B 2 O 3 glass former and heavy metal Bi 2 O 3 , with potential applications in mitigating the effects of gamma radiation. Using a melt-quenching and annealing process the target glass compositions were synthesized from granite sludge, incorporating various concentrations of the heavy metal oxide Bi 2 O 3 . This method offers an innovative solution for both waste management and radiation shielding. The prepared glasses were analyzed using X-ray diffraction (XRD), which confirmed their amorphous structure. Thermal properties were assessed by measuring thermal expansion, which showed a significant reduction in both the softening temperature (T d ) and the glass transition temperature (T g ) as the concentration of Bi 2 O 3 increased. The UV-Visible absorption spectra demonstrate a significant increase in the intensity of the absorption peak at 395 nm before gamma irradiation. Following a cumulative 100 KGy gamma irradiation dose, the intensities of all the near-visible absorption bands showed a notable increase, accompanied by a slight shift in their peak wavelengths toward longer wavelengths, approximately around 425 nm. Further analysis of the optical parameters revealed a decrease in the optical bandgap values, from 2.628 to 2.327 eV and from 2.545 to 2.089 eV, before and after irradiation, respectively. In contrast, both the Urbach energy and refractive index increased with the incorporation of Bi 2 O 3 and following gamma irradiation. The chemical durability of the glasses was assessed by examining their resistance to etching in strong hydrofluoric (HF) acid. The results demonstrated that the durability of the glasses improved as the content of Bi 2 O 3 was increased. The FTIR spectra exhibit characteristic vibrational modes associated with triangular (BO₃) and tetrahedral (BO₄) groups, each within their respective wavenumber ranges. Furthermore, the enhanced intensities of certain FTIR bands indicate shared vibrations involving Si - O or Bi - O bonds at specific sites, as confirmed by the deconvoluted spectra. The enhancement of the optical and chemical properties of glass derived from recycling the granite waste indicates significant potential for its application in specialized areas. These improvements could be especially advantageous in industries requiring high optical precision, such as the potential production of optical fibers or radiation-resistant materials.