NiFe based synthetic LDH, study of chromate adsorption mechanisms

Layered Double Hydroxides (LDH) have proven to be extremely versatile compounds, suitable for multiple uses in different fields of technology. In this work, a NiFe–NO3 LDH was synthesized, and its structure was confirmed by means of X-Ray Powder Diffraction (XRPD), FT-InfraRed Spectroscopy (FT-IR) and Field Emission Scanning Electron Microscopy (FE-SEM). The compound efficiency as adsorber of Cr(VI) in water solution was studied, planning the adsorption experiments through the use of the experimental design techniques (Design of Experiment – DOE). For the purpose to find a reuse of the LDH, after the chromium remediation process, according with the circular economy statements, the chromate capture mechanism was investigated. The results demonstrate that the chromate adsorption capacity is influenced mainly by the ratio LDH mass/solution volume and the initial concentrations of Cr(VI). As the adsorption mechanism, it consists of two different processes, the interlayer exchange and an entrapment of the chromate into the external octahedral sites of the layers.