Highly efficient and selective adsorption of In³⁺ on pristine Zn/Al layered double hydroxide (Zn/Al-LDH) from aqueous solutions

A pristine Zn/Al-layered double hydroxide (Zn/Al-LDH) showed excellent adsorption ability and selectivity towards In³⁺ ions from aqueous solutions. The adsorption behaviour as a function of the contact time, solution pH, ionic strength, and amount of adsorbent under ambient conditions revealed a strong dependency on the pH and ionic strength over In³⁺ intake. The structure and properties of Zn/Al-LDH and In³⁺ adsorbed Zn/Al-LDH (In–Zn/Al-LDH) were examined carefully by X-ray diffraction, Fourier transform infrared spectroscopy, N₂-sorption/desorption, UV–vis spectroscopy, and X-ray photoelectron spectroscopy. The adsorbent had a sufficient number of active sites that were responsible for the In³⁺ adsorption and quite stable even after the adsorption process. The selective adsorption of In³⁺ on Zn/Al-LDH was also observed even from a mixture containing competing ions, such as Mn²⁺, Co²⁺, Ni²⁺, Cd²⁺, Pb²⁺, and Cu²⁺. The adsorption experiments showed that Zn/Al-LDH is a promising material for the pre-concentration and selective removal of In³⁺ from large volumes of aqueous solutions. - Highlights: • A pristine Zn/Al-layered double hydroxide showed good selectivity for In³⁺ ions. • The material exhibited a maximum In³⁺ intake of 205 mg g⁻¹ at pH 6. • The materials showed good affinity of In³⁺ over Cu²⁺ and Pb²⁺ from ion mixtures.