A novel slag composite for the adsorption of heavy metals: Preparation, characterization and mechanisms.

The utilization of solid waste for resource recovery and production of value-added products is the theme of green chemistry. Currently, how to using solid wastes to prepare environmentally-functional materials with high performance and strength is one of the hot topics. In this research, electrolytic manganese residue (EMR) was thermally activated with calcite to prepare a silicon-based functionalized adsorbent (C-EMR) for the removal of cadmium (Cd2+, 467.14 mg/g) and lead (Pb2+, 972 mg/g). The thermodynamic results indicated that the removal process of Cd2+ and Pb2+ by C-EMR were endothermic and spontaneous. HNO3 can effectively strip the two adsorbed metals from C-EMR with the stripping efficiency of nearly 80% for Cd2+ and 99.92% for Pb2+, indicating that adsorption and ion exchange may be the main reason for the removal of the metals on C-EMR. Besides, surface precipitation was also responsible for removing some Pb2+ from the aquatic environment according to the X-ray photoelectron spectrometry (XPS) analysis. Results indicate that -SiO3- has stronger affinity with Pb2+ and Cd2+ than other groups ((-MnO2), -OH) by theoretical calculation (VASP, GGA-PBE). This study shows that this novel adsorbent (C-EMR) can be adopted as an environmentally-friendly, inexpensive and efficient adsorbent for removal of Cd2+ and Pb2+ from aquatic solution. This technique not only provides potential adsorbent for the elimination of heavy metals but also proposes an alternative route for the treatment and utilization of waste solid.