Research progress on iron-rich industrial waste as environmentally functional material

Iron-rich industrial waste (steel slag, red mud, nickel slag, copper slag, and iron ore tailings) is characterized by high yield, low utilization, and rich iron content (≥29%). Their utilization as resources can be valuable in creating a circular economy. This paper reviewed the sources, basic properties, and applications of five iron-rich industrial waste products as environmentally functional materials (adsorbents, gas absorbent materials, catalysts, soil amendment materials, oxygen carriers, functional ceramics, flocculants, and ceramisite) and discussed their environmental risks. Steel slag and red mud can be used to develop various types of environmentally functional materials due to the presence of reactive metal oxide phases, such as Fe₂O₃ and CaO. However, nickel slag, copper slag, and iron ore tailings contain large amounts of inert phases, such as Fe₂SiO₄ and SiO₂, limiting their activity and reducing their application potential for environmental pollution control. The environmental risks include the leaching and accumulation of toxic and hazardous elements in the waste slag, such as Cu, Zn, As, Ni, Cr, and Mn, into water bodies and soil, as well as the generation of new waste products, such as Fe₃O₄ agglomerates and gypsum. This review aimed to provide new insights for expanding and maximizing the comprehensive utilization of iron-rich industrial waste products as a resource.