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 (σ _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 (A _m) in units of mmol m⁻² increases with the increase of the σ _S,T value of the LDHs samples. The release rate of naproxen from the naproxen/LDHs nanohybrids decreases with the increase of the σ _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 6~11.5, the uptake amount (A _eq) of naproxen on the LDHs decreases with the increase of pH value. The A _m values of LDHs(Cl⁻) are much higher than that of \( {\text{LDHs}}{\left( {{\text{CO}}^{{2 - }}_{3} } \right)} \), which may contribute to that LDHs(Cl⁻), which has a stronger anion exchange ability than \( {\text{LDHs}}{\left( {{\text{CO}}^{{2 - }}_{3} } \right)} \). 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.