Waste to wealth: Recovery of value-added products from steel slag

Steel slag, a by-product generated during steel production poses a solid waste disposal challenge. The same slag contains valuables such as titanium, nickel, vanadium, iron, aluminum, silica among others. The extracted components can cause productive value addition in diverse realms like wastewater treatment to semiconductor devices. A paradigm shift is required towards waste valorization for developing profitable extraction methods for these constituent elements. In this review, an attempt was made to assimilate such technologies into one concrete and concise compendium. The pros and cons of each method were weighed comparatively with respect to applicability and innovation. An effort was attempted for assessing key design aspects and scale-up potential vis-à-vis the economic analysis for the valorization techniques. It was seen that the leaching technique was the most widely used in the resource recovery domain followed by other techniques like fusion, hydrothermal treatment. Techniques that dominate the exploration of some of the metals from their lean ores or respective mineral slags might also be explored for their recovery from steel slag. Some technologies like slag filter development for phosphate removal has already been tested in real-life conditions while others are in the nascent stages of development. Special focus can be directed towards the simultaneous extraction of multiple components or direct in-situ product formation and its subsequent separation. This paper reviews various technologies for steel slag valorization to guide researchers working in the field of slag resource recovery and sustainable waste utilization.