Identification of chromate binding mechanisms in Friedel’s salt

The Friedel’s salt was found to be a major hydration product of NaCl and blast furnace slag and its ability and mechanism for solidification/stabilization of Cr was investigated. The metal-fixing capacity, mineral phases and its vibration bands in matrices were characterized by toxic characteristic leaching procedure (TCLP), X-ray diffraction (XRD), scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR), respectively. The Tessier’s five-step sequential extraction procedure was used to analyze the chemical speciation of Cr. To study the binding mechanisms of the Friedel’s salt on Cr, solid solutions between Friedel’s salt and Cr-Friedel’s salt were synthesized and characterized by XRD, FTIR, inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and ionic chromatography (IC). The results indicated that the Friedel’s salt can incorporate Cr effectively by physical encapsulation, isomorphous substitution and adsorption.