A facile approach towards large-scale synthesis of pristine hematite nanoparticles with enhanced photo/catalytic properties via annealing of iron sulfate precursor in presence of treated egg shell wastes as desulfurizer

This work presents a new green perspective for the synthesis of hematite nanoparticles (HNP) via annealing the plain inorganic ferric sulfate (FS) precursor at (700–900) °C under a caked bed of the treated egg shell wastes as desulfurizer. Morphological and microstructural analyses depict the pristine phase of α-Fe2O3 crystal for the annealed samples along with exhibiting a reduced particles' size of 21 nm for FS annealed at 700 °C compared to the larger sizes of ≈29 and 50 nm for FS annealed at 800 °C and 900 °C, respectively. Moreover, FS annealed at 700 °C exhibited a unique hierarchal structure with various pores system on multi-scales, larger surface area with roughness, lower luminescence, and better uniformity over FS 800 and 900 nanoproducts. FS 700 showed a superior degradation efficiency ≈100% at 10 min with a rate constant of 11.06 × 10−2 min−1 for the pollutant Congo Red dye at room temperature in complete darkness, obeying pseudo-first-order reaction kinetics. Also, FS 700 could catalyze the production rate of biogas yields from the biodegradation of green algae (Enteromorpha) over other products. The photocatalytic study of terephthalic acid hydroxylation revealed that the induced fluorescence intensity is highest for FS 700 and is time dependent, following zero-order reaction kinetics. Accordingly, this contribution can furnish a striking piece of evidence for adopting the present methodology as a novel approach not only for the synthesis of HNP with superior features in good yields for industrial scales but also as a green alternative to the widely-used conventional organic precursors, reducing the greenhouse gases and recycling the environmental egg wastes.