Geopolymer synthesized from electrolytic manganese residue and lead-zinc smelting slag: Compressive strength and heavy metal immobilization

In order to follow the growing trend towards waste re-utilization and clean production, geopolymers were synthesized to immobilize Pb 2+ and Zn 2+ by simultaneously using electrolytic manganese residue (EMR) and lead-zinc smelting slag (LZSS) as raw aluminosilicate materials. Different contents of supplementary cementitious materials (i.e., blast furnace slag , sodium aluminate and silica-gel powder) were respectively employed to study the influences of Ca, Al and Si on compressive strengths of geopolymers. Moreover, the geopolymers can be used to immobilize heavy metals including Pb and Zn. The effects of heavy metals on compressive strength and leaching concentration were explored. Results showed that, geopolymers with 1% Pb(NO 3 ) 2 loading had a highest 7-day compressive strength of 28.5 MPa and a low heavy metal leaching concentration below the limit (total Pb < 5 mg/L, total Zn < 100 mg/L). Proved by XRD, FTIR , SEM-EDS, XPS analyses and theoretical calculation, the immobilization of Pb/Zn in EMR/LZSS based geopolymers was realized by physical encapsulation and chemical bonding. The proposed technology can be potentially used to convert Pb/Zn-containing solid wastes into less hazardous or nonhazardous solids for environmentally acceptable construction applications.