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 Zn 0.79 Al 0.21 (OH) 2 (CTA) 0.11 ·0.79H 2 O (denoted as Zn 4 Al–CTA–LDH) has been prepared using separate nucleation and aging steps. The adsorption behavior of Zn 4 Al–CTA–LDH for a number of metal ions was investigated. The results showed that Zn 4 Al–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 Zn 4 Al–CTA–LDH toward Cr(VI) is ∼782 mg/g, and that toward Cu(II) is ∼450 mg/g, respectively. As such, Zn 4 Al–CTA–LDH provides a potential remedy for Cr(VI) and Cu(II) in contaminated water.