Solidification/stabilization of lead-zinc smelting slag in composite based geopolymer

Lead-zinc smelting slag (LZSS) is a hazardous waste due to the presence of heavy metals (Pb, Zn, Cu and Cr) and its improper disposal has serious consequences on ecosystem. The solidification/stabilization of hazardous waste through geopolymer binders is a promising technique to overcome these consequences. Hence, LZSS was solidified through composite based geopolymer (Pulverized Fuel Ash (PFA) and Blast Furnace Slag (BFS)). The experiment was carried out in to two steps i.e. strength development and solidification. Effect of various factors on compressive strength was evaluated through single-factor and orthogonal experiments. While, solidification/stabilization efficiency of composite based geopolymer was analyzed through compressive strength and leaching concentration of heavy metals in two extractants. The results showed that highest compressive strength (47.39 MPa) was achieved through optimization of each factor. The LZSS was solidified in composite based geopolymer sample having highest compressive strength. While, the compressive strength was decreased to 15 MPa with 80% addition of LZSS. According to leaching tests, this strength was satisfactory for landfill disposal and construction purposes because Pb, Zn, Cu and Cr had not exceeded the critical limits. The heavy metals were solidified through physical and chemical means which was proved by X-ray diffraction (XRD) analysis, Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectrometry (FTIR) analysis.