Steel slag waste produced by the steel industry accumulates in open areas or is disposed of in landfills, causing harm to the environment and human health. Valorizing steel slag through comprehensive data analysis is imperative and could add value to the product with respect to energy conversion and storage applications. This study investigated the morphological, structural, and optical characteristics of a thermally annealed steel slag composite generated from iron and steel factories. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, and UV–visible spectrophotometry were subsequently used to evaluate the impact of thermal treatment on the morphology, structure, elemental composition, and optical properties. It was found that the pre-treated slag composites contained a variety of irregular grain sizes and microscale fragments, primarily composed of C (18.55%), O (50.85%), and Fe (29.41%), with lower amounts of Mg (0.31%), Si (0.44%), and Ca (0.44%), indicating the natural formation of a disordered iron composite. Thermal treatment at different temperatures (300 °C, 600 °C, and 900 °C) increased the grain density and clustering, resulting in denser two-dimensional microstructures at 900 °C. Additionally, XRD and Raman analyses of both untreated and thermally treated slag composites revealed the presence of a disordered iron oxide composite, including (Fe₃O₄), hematite (α-Fe₂O₃), and maghemite (γ-Fe₂O₃) phases. A significant increase in optical absorbance was also observed after annealing at 600 °C, highlighting the successful optimization of the elemental composition of the slag composite. A band gap energy of approximately 2.2 eV was obtained from this optimization at 600 °C. The optical conductivity of the composite reached 2.1 × 10⁶ S⁻¹ at 600 °C, which indicates an enhancement in charge transfer among the optimized chemical elements in the waste composite. These findings suggest an optimization method for novel composites derived from steel slag waste, indicating its potential as a low-cost material for energy storage systems (batteries, supercapacitors, and fuel cells) and optoelectronic devices.

Model photocatalysts composed of titanium dioxide (TiO2) nanoparticles were prepared to assess the impact of different synthesis techniques on their photocatalytic activity towards methylene blue. TiO2 nanoparticles were synthesized using three distinct methods: high-energy ball-milling (HEBM), sonication, and pulse laser ablation. The engineered photocatalysts exhibited varying morphology, crystallinity, and optical properties, as evidenced by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The synthesis techniques notably resulted in different particle sizes, with mean sizes of 121.2 nm, 25.53 nm, and 22.38 nm, and corresponding crystallite sizes of 24.86 nm, 33.5 nm, and 34.4 nm for HEBM, sonication, and pulse laser ablation, respectively. All of the synthesized TiO2 nanoparticles displayed significantly enhanced photocatalytic activity under low-intensity UV light in comparison to the TiO2 raw material. However, the choice of synthesis method had a substantial impact on photocatalytic performance. Specifically, TiO2 prepared via ultrasonication and continuous ball milling exhibited the highest photocatalytic activity among the methods. The most rapid degradation rate (K = 0.0049 min^(-1)) was observed for TiO2 produced through continuous ball milling and ultrasonication. These findings indicate that the synthesized TiO2 nanoparticles hold potential for use as catalysts for degrading various types of organic pollutants.