Innovative treatment of toxic oily petroleum wastewater with magnetic sludge under UVA light

The primary objective of the present study is to address the critical issue of managing the large volumes of toxic oil sludge and oil waste generated in various industrial processes. This environmental challenge poses significant risks to ecosystems and human health, necessitating effective remediation strategies. In this research, we make a pioneering attempt to synthesize a novel photocatalyst, specifically Char/Fe₃O₄/TiO₂-based magnetic waxy diesel sludge, aimed at reducing the complex and hazardous compounds present in toxic oily petroleum wastewater when exposed to ultraviolet light. The synthesis of the Char/Fe₃O₄/TiO₂ photocatalyst involved an innovative approach where titanium dioxide (TiO₂) was meticulously coated onto specially prepared synthetic magnetic activated carbon. A comprehensive array of analytical techniques was employed to substantiate the successful synthesis of the photocatalyst. These analyses included Fourier-transform infrared spectroscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, thermogravimetric analysis combined with differential thermogravimetry, CHNOS analysis, X-ray fluorescence, Raman spectroscopy, diffuse reflectance spectroscopy, and vibrating sample magnetometer techniques. The utilization of these diverse analytical methods provides robust evidence of the structural and functional integrity of the synthesized photocatalyst. The experimental work was conducted in a controlled batch system to evaluate the effectiveness of the photocatalyst under varying conditions. The results obtained from the analyses confirmed the successful incorporation of iron and titanium dioxide within the synthesized magnetic char, thereby validating the synthesis of the photocatalyst. To further optimize the wastewater treatment process, Response Surface Methodology was employed to systematically investigate the influence of various operational parameters. The optimal conditions for the treatment of toxic oily petroleum wastewater were determined to be at a pH of 6.5, with a photocatalyst dosage of 300 mg, a temperature of 35 °C, and an exposure time of 35 min under UVA_6W irradiation. Under these ideal conditions, the photocatalytic system demonstrated remarkable efficacy in removing hazardous compounds, achieving removal rates of 98.136% for Chemical Oxygen Demand, 95.194% for Biochemical Oxygen Demand, 92.66% for Total Kjeldahl Nitrogen, 95.99% for Total Dissolved Solids, and 91.99% for Total Suspended Solids. Kinetic and isotherm studies further elucidated the behavior of the photocatalytic process, revealing that the removal of toxic oily wastewater with Char/Fe₃O₄/TiO₂ adhered closely to pseudo-first-order kinetic models, as well as the Freundlich and Henderson isotherm models. The negative standard enthalpy of activation (ΔH^o) indicated that the adsorption process is exothermic, suggesting that heat is released during the removal process. Conversely, the increasing value of the standard Gibbs free energy of activation (ΔG^o) with temperature signified that the adsorption is a nonspontaneous process, while the negative value of the standard entropy of activation (ΔS^o) implied a reduction in the degree of freedom of the reactants as they evolve into the activated complex. In conclusion, the development and deployment of a well-designed, innovative photocatalyst from the magnetic sludge (represent a cost-effective strategy for the remediation of petroleum wastewater. This approach not only holds promise for industrial manufacturers seeking to mitigate their environmental footprint but also serves as a significant step toward improving environmental quality and sustainability.