An Overview of Precious Metal Recovery from Steel Industry Slag: Recovery Strategy and Utilization

Abstract

Steel slag is a solid waste of the steel industry, produced during steel production. Three types of slag, namely electric arc furnace (EAF), basic oxygen furnace (BOF), and Linz-Donawitz processed slag (LD-slag) are the steel industry byproducts. That slag comprises precious elements including zinc (Zn), chromium (Cr), iron (Fe), nickel (Ni), silicon (Si) , aluminum (Al), and vanadium (V) and is considered a secondary source of many metals. These metal constituents can be recovered from slags by employing mineral processing techniques like crushing, grinding, magnetic separation, eddy current separation, flotation, leaching, and/or roasting. Metal extraction from steelmaking slag and slag utilization is essential not only for conserving metal supplies but also for environmental protection. This review article evaluated and summarized various extraction methods including magnetic separation, roasting, pyrometallurgical method, hydrometallurgical and bio hydrometallurgical technique to recover precious metal constituents from obtained slag. The state-of-the-art of metal recovery from slag using the aforementioned methodologies and the merits, and demerits of each procedure have been illustrated comprehensively. Suggestions have been made to overcome the shortfall and or lacuna of the technology for better performance and efficiency. The opportunities and difficulties portion of this article paints a vivid picture of turning such a beneficial technology into a more adaptable procedure with some additions that may motivate and lead future research in new directions. The essence of this survey indicates that extracted metal and treated slag might be reutilized in various fields ranging from biomedical to fertilizer applications.

Leaching Vanadium from the Spent Denitration Catalyst in the Sulfuric Acid/Oxalic Acid Combined Solvent

“…The effect of leaching time (3–9 h) on the V leaching rate was depicted under the following conditions: L/S ratio of 20 mL·g –1 , 20 wt % sulfuric acid, and 0.3·mol L –1 oxalic acid at 140 °C (Figure ). The leaching rate of V increased continuously from 83.04 to 95.65% as the leaching time increased from 3 to 7 h and stabilized after 7 h. It indicated that enough leaching time promoted the reactions between the acid solvent and spent denitration catalyst, resulting in a higher leaching rate of V. This case might be possible because sufficient time should be spent on completely released V from the spent denitration catalyst since the V-bearing lattice structure was very stable and hard to break down. , Therefore, a leaching time of 7 h was selected by considering the maximum leaching rate of 95.65%.…”

“…The difficulty of releasing V from the spent denitration catalyst was determined by the interaction intensity between the leaching solvent and the mineral phases of the spent denitration catalyst. 24 In the sulfuric acid/oxalic acid combined leaching system, the crystal lattice structure of the V-bearing mineral phase was disrupted by hydrogen ions which were provided by combined acids. 20,27 In this work, the maximum concentration of hydrogen ions reached 1.99 mol•L −1 , which could strongly enhance the interaction between the combined acid and the mineral phase.…”

“…Compared with sulfuric acid, oxalic acid has better environmental adaptability but a higher price . Moreover, the acidity of oxalic acid is weaker than that of sulfuric acid at the same concentration . To efficiently leach metals and achieve the economic and environmental goals of the industry, an inorganic acid and organic acid mixture was used as a leaching solvent .…”

“…23 Moreover, the acidity of oxalic acid is weaker than that of sulfuric acid at the same concentration. 24 To efficiently leach metals and achieve the economic and environmental goals of the industry, an inorganic acid and organic acid mixture was used as a leaching solvent. 25 For instance, Wang and Yang.…”

Enhancing Bioethanol Yield from Ravenna Grass (Saccharum ravennae): Optimization of Pretreatment Strategies and Surfactant-Assisted Enzymatic Hydrolysis for Maximum Sugar Yield

“…In our earlier investigations, highly pure alkaline lignin was successfully extracted from RGB. Such a product can be utilized in specialized aromatic chemical development, packaging, heavy metal removal, and thermal combustion. ,,, To summarize, alkaline pretreatment followed by nonionic surfactant-mediated enzymatic hydrolysis with fermentation by genetically modified microorganisms can enhance the ethanol yield and utilization of pretreatment byproducts. Thereby, such interventions can enable bioethanol production on a cost-competitive basis.…”