Blast furnace slag (BFS) is generated as a by-product in the ironmaking process, and hence, the development of a recycling system for BFS waste is important. In this study, the calcium component of BFS obtained from a steel company in Japan was successfully used as raw material of the synthesis of metaettringite. Metaettringite has been recently considered for as an adsorbent for boron, which is toxic to humans and animals. The BFS used was amorphous, and mainly consisted of CaO, SiO2, Al2O3, and MgO; in particular, it contained 42.82 mass % CaO. The X-ray diffraction pattern and Fourier transform infrared spectrum of the synthesized sample indicated the formation of metaettringite. Field-emission scanning electron microscopy observations revealed its needle-like morphology. The synthesized metaettringite adsorbed 1.189 mg-B/g-adsorbent in 240 min, which was approximately 25 times greater than that achieved using the parent BFS. The metaettringite can reduce the boron concentration to below the uniform effluent standard in industrial wastewater in Japan (16 mg/L).
Keywords: Adsorbent; Blast furnace slag; Boron; Metaettringite; Recycle; Water treatment.