Adsorption of cefixime and lamotrigine on HKUST-1/ZIF-8 nanocomposite: isotherms, kinetics models and mechanism

Water pollution is one of the biggest problems in world today, which is directly related to the progress and development of the countries. Using the adsorbents of porous nanostructures, called metal-organic frameworks (MOFs), for the removal of pharmaceutical pollutants is a novel technology. HKUST-1/ZIF-8 nanocomposite was synthesized using a facile and green ultrasonic method and characterized to establish selective adsorption properties of a wide range of drug contaminants and higher water stability than HKUST-1 in water. Moreover, the adsorption of cefixime (CFX) and lamotrigine (LTG) on ZIF-8, HKUST-1, Fe3O4/HKUST-1, Fe3O4/ZIF-8, HKUST-1/ZIF-8, and activated carbon was compared. Regarding acid-base interactions, the adsorption capacity of drugs with the amine group on ZIF-8 and drugs with an acidic functional group on HKUST-1 was very low. The nanocomposite could remove drugs with amine groups and acidic functional groups with appropriate adsorption capacity and water stability from aqueous media. At 25 degrees C, pH 7, and a contact time of 240 min, the maximum adsorption capacity of CFX on HKUST-1/ZIF-8 composite was 110 mg/g, which was three times (38 mg/g) greater than that of HKUST-1. The maximum adsorption capacity of LTG on HKUST-1/ZIF-8 composite was 139 mg/g which was 1.5 times (101 mg/g) as large as that of ZIF-8. Hydrogen bonding, electrostatic interaction, and acid-base interaction might be responsible for the adsorption of drugs. By adding Fe3O4 to MOFs, the synthesized materials become superparamagnetic and could be easily separated from the water using a magnetic field. Nevertheless, magnetic ZIF-8 could be used for 5 cycles with the removal efficiency of around 90% post-recycling, while magnetic HKUST-1 could be applied for 3 cycles because of its low stability. Based on correlation coefficient (R-2), Langmuir isothermal model and pseudo-second-order model were chosen for the adsorption of CFX and LTG, respectively. [GRAPHICS] .