Highly Selective and Efficient Removal of Cr(VI) and Cu(II) by the Chromotropic Acid-Intercalated Zn-Al Layered Double Hydroxides

A chromotropic acid (CTA) intercalated layered double hydroxide (LDH) supramolecular assembly with the molecular formula Zn0.79Al0.21(OH)(2)(CTA)(0.11)center dot 0.79H(2)O (denoted as Zn4Al-CTA-LDH) has been prepared using separate nucleation and aging steps. The adsorption behavior of Zn4Al-CTA-LDH for a number of metal ions was investigated. The results showed that Zn4Al-CTA-LDH is highly selective and efficient for the adsorption of both Cr(VI) and Cu(II), and the sorption kinetic curves could be well fitted with the pseudo-second-order model. With the concentration of Cr(VI) or Cu(II) increasing from 200 to 10000 ppm, the maximum absorption capacity of Zn4Al-CTA-LDH toward Cr(VI) is similar to 782mg/g, and that toward Cu(II) is similar to 450 mg/g, respectively. As such, Zn4Al-CTA-LDH provides a potential remedy for Cr(VI) and Cu(II) in contaminated water.