The recovery of new materials from industrial waste is the target of many scientists and researchers all over the world. Zinc and aluminum sludge powders came from big iron and aluminum sheets industry were used as starting materials for zinc aluminate fabrication. The collected sludge powders were characterized by using XRF, XRD and DTA investigations, hydrozincite (Zn5(CO3)2(OH)6) and gibbsite (Al(OH)3) are the main phases of zinc and aluminum sludges, respectively. Solid-state reaction (SSR) and molten salt synthesis (MSS) were carried out at 1100°C for 5 h by 3°C/min, using the collected sludge without any primary sophisticated chemical treatments. SSR and MSS samples were characterized by using XRD, FTIR, XPS, SEM and TEM investigations. Pure phase zinc aluminate nanoparticles were achieved by SSR and MSS with 17.4 and 12.7 nm, respectively. The microstructure of SSR sample was characterized by a high degree of particles aggregation, whereas the structure's homogeneity was modified by MSS. Optical properties of SSR and MSS samples were studied by using UV-visible and PL spectroscopy, the band gab energies were found to be 2.78 and 2.48 eV for SSR and MSS samples, respectively. MSS sample was distinguished by higher absorbance efficiency and lower recombination rate than SSR sample. The small band gab energy and the high absorbance efficiency evaluate this material for photocatalytic application as like as, organic dyes degradation in waste water treatments.