Microwave enhanced solidification/stabilization of lead slag with fly ash based geopolymer

Geopolymers have been introduced as a promising strategy for the solidification/stabilization (s/s) of heavy metals due to its sustainability and environmental friendliness. However, it usually takes a long curing time to achieve a rational mechanical strength, and the stability of heavy metals in geopolymer needs to be further enhanced to reduce possible environmental risks. Here we introduced a microwave (MW) strategy for the s/s of real lead slag with geopolymer technology. The stabilization of lead slag (LS) with different addition ratios were characterized, and the effect of microwave power as well as irradiation time were also examined to optimize the geopolymer strength and the leaching of Pb. The geopolymerization process was drastically enhanced, showing shortened polymerization period from 28 days to 15 min with an optimum compressive strength of 18.8 MPa and s/s efficiency of 98.73%. It was revealed that physical embedding was the main stabilization mechanism proved by lead speciation, X Ray Diffraction (XRD), Fourier Transform Infrared Spectrometry (FTIR), Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometry (EDS) analysis. It suggested that the combined effects of local heating and enhanced dehydration with MW irradiation would benefit the stabilization of lead slag in geopolymers. (c) 2020 Elsevier Ltd. All rights reserved.