Upcycling of air pollution control residue waste into cementitious product through geopolymerization technology

This study explores the possibility of using geopolymerization technology (GT) to immobilize the potentially toxic elements (PTEs, e.g., Zn, Cu, Cr, As) in the APCr and convert it into useful cementitious product. To maximize its recycling, the amount of APCr in the designed product was increased gradually from 20% to 80% by the total solid mass. Leaching test showed that GT can effectively immobilize the PTEs in the APCr solidified samples without any health and environmental concerns. The compressive strength of samples can exceed 18 MPa at 28 days at a highest amount of 80% APCr through GT. Thermogravimetric analysis (TGA) results showed that solidified samples underwent mass loss due to evaporation of free and physically bound water at low temperatures (<200°C) and melting and evaporation of soluble salts in APCr at high temperatures (>800°C). Characterization of solidified samples conducted through the X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy-Energy dispersive analysis (SEM) revealed the formation of C-A-S-H and N-A-S-H gels in solidified bodies and verified that APCr was successfully solidified and embedded into the geopolymer network structure