Occurrence of steel converter slag and its high value-added conversion for environmental restoration in China: A review

As the main co-product during the iron and steelmaking process, steel converter slag has been mainly landfilled and/or utilized as concrete aggregates for road construction in China. However, such a vast amount of steel slag emission, no more than 30% efficient use of steel slag in China, would undoubtedly cause serious environmental problems. Moreover, large amounts of CO2 could be emitted during the whole steelmaking process, accounting for approximately 15% of the total CO2 emission in China. This review first summarizes the classification, production, and utilization of iron-and steel-making slag. Then, methods to the comprehensive utilizing are examined in aspects of main characteristics, pre-treatment methods, primary utilization and high value-added conversion of steel converter slag for environmental protection in China. The critical constraints that impede the exploitation of steel converter slag are objectively discussed in light of the reinforcement for the recycling of these by-products. Thus, a systematic database on the characteristics and uses of steel slags should be also established for better utilization. Moreover, aiming for China's 2060 carbon neutrality objective for tackling global climate change, the possible conversion of converter slags close to CO2 generating source to photocatalyst (such as heteroatom doped hydroxyapatite) is proposed, up recycling a part of solid waste. Based on this, a proposal of comprehensive and circular system converting converter slag into photocatalyst for CO2 reduction and H2 production is crucial for realizing environmental and economic synergies and sustainability for future generations.