Recovery of valuables from steel mill oily magnetic filtration waste and their application in coke plant wastewater treatment.

Cold-rolled magnetic sludge, typically regarded as industrial waste, contains substantial amounts of valuable components such as magnetic iron oxide and residual oil. Conventional disposal methods, including landfilling and incineration, impose significant environmental challenges. This study explores resource recovery from magnetic sludge using a magnetic field-assisted solvent extraction technique. Several organic solvents-ethyl acetate, acetone, and N-methyl-2-pyrrolidone-were assessed for oil extraction efficiency, followed by solvent regeneration through distillation to achieve a zero-waste process. The recovered iron oxide was comprehensively characterized using scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), along with evaluations of its magnetic and semiconducting properties. Additionally, the extracted iron oxide demonstrated catalytic activity in an advanced electro-oxidation process for coke plant wastewater treatment, achieving up to 95% colour removal and reductions of 87% in cyanide and 93% in chemical oxygen demand (COD). The recovered oil was analyzed for moisture content, calorific value, and ferrography to determine its suitability as a reusable fuel. Overall, the findings highlight the potential of magnetic sludge as a source of value-added materials for steel plant operations, supporting sustainable waste management and circular economy initiatives.