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 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.

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.

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