Synthesis of efficient, reusable, biomorphic hierarchical MgAlLa mixed metal oxides for removal of fluoride ions

Abstract

As an easily available layered double hydroxides (LDHs), hydrotalcites show significant effect in the adsorption of various ions in wastewater. It is worth noting that the calcined products (LDOs) of LDHs as adsorbents have the advantages of large specific surface area, low cost, renewable and non-toxic to the environment. Herein, sustainable, efficient, biological, and hierarchical structure MgAlLa mixed metal oxides using catkins as a template (BC-LDOs) are reported. A facile synthetic approach was presented for hierarchical MgAlLa layered double hydroxides via the simple coprecipitation method followed by a subsequent calcination at 550 C for 3 h. BC-LDOs were characterized with IR, XRD, SEM, TEM, and BET and were studied for their adsorption performance of fluoride. The results showed that high-specific surface area of BC-LDOs is 118.02 m 2 /g, which is 10 times higher than that of MgAlLa mixed metal oxides without template (MgAlLa-LDOs). BC-LDOs had the best adsorption effect at pH 4-5 and the removal efficiency could reach more than 98%. In the experimental results involved in the study, the maximum adsorption capacity is 33.15 mg/g. In addition, the adsorption process of fluoride ions conformed to the pseudo-second-order model and the Freundlich model. Furthermore, the synthesized BC-LDOs were recyclable and still exhibited good adsorption effect after 5 times of regeneration. The innovation of this study lies in the introduction of multi-fiber catkins. There is no report on the introduction of catkins into LDHs in relevant studies.Hence, BC-LDOs have a broad application prospect in the treatment and adsorption of fluoride-containing wastewater.