DL-mandelic acid intercalated Zn-Al layered double hydroxide: A novel antimicrobial layered material.

DL-mandelic acid (MA) has been intercalated into Zn-Al layered double hydroxide (LDH) by an anion-exchange reaction. After intercalation of MA anions, the basal spacing of the LDH increased from 0.75 to 1.46 nm, suggesting that the MA anions were successfully intercalated into the interlayer galleries of the LDH. The structure and the thermal stability of the samples were characterized by XRD, FT-IR, TG-DTA. Studies of MA release from ZnAl-MA-LDH in hydrochloric solution (pH = 4) imply that ZnAl-MA-LDH is a better controlled release system than pure MA. Meanwhile, the mechanisms of slow release were assessed by using four commonly kinetic models. Finally, the antimicrobial activity of ZnAl-MA-LDH was tested against two kinds of bacteria and a fungus. The study confirms that the mandelic ions intercalated LDHs have the potential application as a slow release preservative in the future.