Vitrification of contaminated technosoils as a remediation strategy with economic benefits

Abstract Vitrification is a powerful methodology for stabilizing different types of waste, including urban wastes, and contaminated soils. This process is particularly effective because glass can immobilize hazardous pollutants. This study assess the feasibility of ex-situ vitrification as remediation strategy for an Hyperurbic Technosol (Loamic, Calcaric, Eutric) in an urban industrial neighbourhood in Barcelona (Spain). Five different batch compositions were prepared using these Hyperurbic Technosol, incorporating different alkali additions to enhance the fluidity of the glasses, and Sb to promote glass discoloration. The final glass compositions fall within the glass-forming region of the SiO 2 -CaO-Al 2 O 3 system. Vitrification was carried out at 1350–1450 ºC, with a holding time of 2 h. X -ray fluorescence (XRF), X -ray diffraction (XRD), dilatometry, and hot stage microscopy (HSM) colorimetric spectroscopy were used to characterize the subsoil and the obtained glass. Differential thermal analysis and thermogravimetry (DTA-TG) were used to determine nucleation and crystallization temperatures to produce a glass–ceramic. The efficiency of the method for sequestering hazardous metals was tested by inductively coupled plasma–optical emission spectroscopy (ICP-OES). The transition and dilatometric temperatures ( T g and T d ) of glasses were determined by dilatometry, being 544–576 ºC and 619–636 ºC, respectively. Based on the viscosity temperatures (106 and 103 Pa·s), the workability range of the produced glasses is considered short (Δ T < 400 °C). Viscosity fixed points were measured by HSM. Glass leaching tests show effective retention of As, Cr, Cu, Pb, Ni and Zn. Overall results suggest that vitrification is a viable and promising approach for the remediation and valorization of contaminated subsoils.