Recovery of Chromium(VI) Ions Using a Nickel-Aluminum-Zirconium Complex Hydroxide Based on Adsorption and Desorption Treatment.

In this study, we evaluate the desorption or recovery capacity of chromium(VI) ions using desorption solutions containing sodium hydroxide (NaOH) or sodium sulfate (NaSO). A complex hydroxide of nickel-aluminum-zirconium (NAZ) was prepared as the adsorbent for the removal of chromium(VI) ions. The results from repeated adsorption/desorption experiments on chromium(VI) ions using NAZ complex hydroxide were evaluated. The desorption percentage of chromium(VI) ions increased with the increase in the concentration of NaOH or NaSO in the desorption solution. The determined optimal concentration of NaOH or NaSO in the desorption solution was 10 mmol/L under the used experimental conditions. After three adsorption-desorption cycles, the recovery percentages of chromium(VI) ions using NaOH and NaSO were 60% (total amounts adsorbed and desorbed were 102 and 61 mg/g, respectively) and 75% (total amounts adsorbed and desorbed were 96 and 72 mg/g, respectively), respectively. Additionally, we confirmed the existence of chromium on the surface of the NAZ complex hydroxide. After three adsorption/desorption cycles, the crystal structure of the NAZ complex hydroxide was maintained. These results indicated the potential of the NAZ complex hydroxide using a desorption solution containing NaOH or NaSO for the recovery of chromium(VI) ions.