Mesoporous manganese silicate composite adsorbents synthesized from high-silicon iron ore tailing

Abstract

Iron ore tailing (IOT) as a solid waste has attracted attention worldwide owing to the potential safety hazards and waste of resources. However, few studies focused on exploiting the structural characteristics of IOT. IOT is a special silicate mineral mixture composed of, for example, quartz, anorthite, microcline, and clinochlore which contain adjustable silica tetrahedron structures. In our research, Mn2+ was introduced to hydrothermally react with the adjustable silica tetrahedrons of IOT with the aid of sodium silicate, to provide IOT with reactive Mn-OH groups and high specific surface areas by constructing functional value-added mesoporous manganese silicate (MS) composites. It was found that the specific surface area (SBET) of IOT improved from 6.3 to 448.2 m2g−1 and achieved ideal pore size distributions after being transformed into MS composites. The composite obtained exhibited an excellent selective adsorption performance that could rapidly remove 100% methylene blue (MB) molecules from the mixed cationic dye solutions within 1min. The adsorption behavior was well described by pseudo second-order model and Freundlich isotherm model, indicating the chemical adsorption and multi-layer adsorption. The maximum adsorption capacity was up to 217mgg−1 (25°C, pH=7, adsorption time: 120min, MB initial concentration: 400mgL−1). Through investigation, it was found that the selective adsorptive ability is based on the hydrogen bonding and the suitable mesoporous structure for MB molecules.