Mechanism, application, influencing factors and environmental benefit assessment of steel slag in removing pollutants from water: A review

Steel slag refers to solid waste with high specific surface area and large porosity that is discharged from the crude steel smelting process in steel mills. The concentration of heavy metal ions leached from the steel slag fulfils many industry criteria and is extremely safe, suggesting that it may be employed as a new form of low-cost adsorbent for removing pollutants from water. This paper reviews the potential of steel slag as an adsorbent for removing pollutants in water; the results demonstrate that steel slag can be used for removing inorganic non-metallic ions (e.g., phosphate, nitrogen, etc.), heavy metal ions, organic dyes and other pollutants from wastewater. In addition, the effect of modified steel slag and reconstituted steel slag in removing pollutants were explored to address problems such as limited adsorption efficiency owing to the limitations of steel slag characteristics. To better clarify the relationship between the use of steel slag in removing pollutants from water, the removal mechanism and influencing factors were analyzed; the results demonstrated that factors such as solution pH, temperature, and steel slag characteristics affect the pollutant removal efficiency. Analyzed from the perspective of economic benefits, environmental benefits, and safety applications, the use of steel slag for removing pollutants in water not only utilizes solid waste resources safely but also treats wastewater, thereby indicating future large-scale applications of steel slag in water treatment engineering.