Synthesis and characterization of Naproxen intercalated Zn-Al layered double hydroxides

In this paper, naproxen was intercalated into Zn-Al layered double hydroxides (LDHs) by ion exchange method to obtain naproxen/LDHs nanohybrids. The effects of the contact time, the composition, and the structural charge density (sigma(S,T)) and the specific surface area of LDHs, and pH value on the uptake of naproxen on LDHs, and the release of naproxen from the naproxen/LDHs nanohybrids were investigated. The adsorption isotherm curves of naproxen on the LDHs obey the Langmuir equation, and apparent monolayer capacity (Am) in units of mmol m(-2) increases with the increase of the sigma(S,T) value of the LDHs samples. The release rate of naproxen from the naproxen/LDHs nanohybrids decreases with the increase of the sigma(S,T) value of the LDHs samples and is much lower than that of naproxen troche, indicating that the naproxen/LDHs nanohybrid is an efficient drug-controlled release system. In the pH range of 6 similar to 11.5, the uptake amount (A(eq)) of naproxen on the LDHs decreases with the increase of pH value. The Am values of LDHs(Cl-) are much higher than that of LDHs (CO32-)which may contribute to that LDHs( Cl-), which has a stronger anion exchange ability than LDHs (CO32). The naproxen molecules are possibly adsorbed on each surface of the basal layer of LDHs. In other words, a bilayer is formed in the gallery of LDHs.