Insights of Auric Ion Adsorption in the Presence of Ferric and Hexavalent Chromium Species on Mg/Al Layered Double Hydroxides

This study reports the synthesis of Mg/Al layered double hydroxide (LDH) by the co-precipitation technique. The produced LDH was then employed as an adsorbent for auric ion (AuCl4-) in the presence of ferric (Fe3+) and dichromate (Cr2O72-) species in an aqueous solution. An adsorption test examined the effects of single and ternary (Au/Fe/Cr) system solutions. The adsorbent underwent characterization by the utilization of FT-IR (Fourier transform infrared spectroscopy), powder XRD (X-ray diffraction), and FE-SEM (Field emission scanning electron microscopy) techniques. The experimental results revealed that the adsorption of AuCl4- without any competing species reached its maximum efficiency at a solution acidity of pH 3. The results of the kinetic investigation indicate that the adsorbent exhibited behavior consistent with a pseudo-second-order reaction. The rate constant (k) values obtained were 2.88 x 10-3 and 3.51 x 10-3 g/(mg.min) for the single and ternary solutions. Based on the Langmuir isotherm model, the adsorption capacities for single and ternary solutions were determined to be 21.75 mg g-1 and 27.78 mg g-1, respectively. The adsorbent exhibited a layered structure characterized by hexagonal platelet-type images.