Synthesis and characterization of CdCr-NO3 layered double hydroxides nanostructures for Cr(VI) ions adsorption: factorial design and statistical analysis for multivariate sorption optimization

In present study, nitrate anion containing CdCr layered double hydroxides (LDH) was synthesized, and characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis-differential scanning calorimetry (TGA-DSC) and energy-dispersive X-ray-scanning electron microscopy techniques (EDX-SEM). The characteristic diffraction peaks in the XRD pattern of CdCr-NO3 LDH at 2. values of 15.10 and 26.02 degrees correspond to (003) and (006) planes (hkl), respectively of crystal system of the LDH, revealing layered structure of material with basal (d) spacing of d(003): 0.59 nm and d(006): 0.34 nm, containing intercalated water and nitrate anions. Stretching vibrations in FT-IR spectrum of the LDH at 3,378.01 and 1,355.51 cm(-1) confirmed the intercalation of water and nitrate ions, respectively, in between hydrotalcite-like layers. EDX study confirmed that CdCr-NO3 LDH contained 20.07%, 72.75% and 7.18% of O, Cd(II) and Cr(III), respectively. SEM image revealed that nanostructured material is porous and layered in nature. TGA-DSC confirmed the thermal stability of material at below 509.44 degrees C. CdCr-NO3 LDH was investigated as an efficient adsorbent for capturing of Cr(VI) ions form industrial effluents. The adsorption was optimized by factorial design approach. Maximum response of CdCr-NO3 LDH for capturing/adsorption of Cr(VI) ions was achieved at optimum concentration of Cr(VI) ions: 10 mg L-1, pH: 4.0, adsorbent amount: 40 mg and shaking time: 30 min at 25 degrees C. Method worked well on real wastewater samples.