Fabrication of nanostructured ZnNiBi-NO3 layered double hydroxides for speciation and preconcentration/separation of chromium ions prior to MIS-FAAS determination

Abstract

Nanostructured ZnNiBi-NO3-Layered Double Hydroxides (LDHs) was synthesised, followed by the simple co-precipitation method using Zn(NO3)(2).6 H2O, Ni(NO3)(2).6 H2O and Bi(NO3)(3) as the precursors. Synthesised LDHs was characterised by various techniques such as infrared (IR) spectroscopy, x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray (EDX) and thermal gravimetric analysis (TGA). ZnNiBi-NO3 LDHs were applied as efficient adsorbents for speciation analysis and preconcentration/separation of Cr(VI)/Cr(III) ions in aqueous samples prior to their trace determinations by microsample injection system-coupled flame atomic absorption spectrometry (MIS-FAAS). ZnNiBi-NO3 LDHs worked well for speciation and preconcentration/separation of Cr(VI)/Cr(III) ions at an optimum of pH 3.0 and adsorbent dosage of 400 mg. LOD and LOQ of Cr(VI) ions were calculated to be 0.03 and 0.10 mu g L-1, respectively with a preconcentration factor of 400. The total saturation capacity of ZnNiBi-NO3 LDHs for Cr(VI) ions was investigated and found to be 46.0 mg g(-1). The mthod was reproduced with RSD <= 1.4% of five replicates. The accuracy of method was evaluated by analysing 10-100 mu g L-1 Cr(VI) ions standard solutions, and Cr(VI) ions were recovered >= 96.9% with RSD <= 2.4%. The developed method worked well on wastewater samples.