Inorganic layered double hydroxides as ascorbic acid (vitamin C) delivery system--intercalation and their controlled release properties.

ZnFe- and MgFe-LDHs were prepared by the anion exchange method, with the aim of adsorption of the ascorbic acid from the aqueous solutions by ion exchange process between anionic derivatives in LDH (Cl) and the anionic vitamin. This leads to successful intercalation of the vitamin into gallery space of LDH that offers a new route to safe preservation of bioactivity as well as controlled release. The prepared LDHs were characterized by XRD, TG-DTA and FT-IR spectroscopy. Adsorption of the ascorbic acid by the LDH under investigation was studied in terms of pH value, amount of LDH, contact time, VC (ascorbate) concentration and chemical composition of the host materials. The results indicate the relatively fast adsorption of the anionic vitamin by ZnFe-LDH-Cl and MgFe-Cl-LDH; reaches the equilibrium in 60 min. The shapes of the adsorption isotherms suggest specific interaction and high affinity. The batch kinetics of ascorbic acid adsorption onto ZnFe-Cl and MgFe-Cl-LDHs were studied. Furthermore, their release behaviors are also examined by spontaneous deintercalation with carbonate anion.