Microwave-assisted preparation of SO42- intercalated hydrotalcites for ammonia-nitrogen removal

The intercalation of SO42- into MgAl hydrotalcites was investigated under microwave irradiation, and the structural and physiochemical properties of the SO42- intercalated hydrotalcites were determined using XRD, FTIR, SEM/EDS, BET and BJH techniques. Microwave irradiation contributed to the intercalation of SO42- anions, which brought about high amounts of SO42- into the interlayer spaces and high crystallinity. The intercalation of SO42- enhanced the acidic sites that cooperated with alkaline sites to activate the NH4+ molecules simultaneously leading to a significant increase in the removal of ammonia-nitrogen in synthetic wastewater. Kinetics and thermodynamics of the SO42- intercalation under microwave irradiation revealed that Langmuir isotherm fitted the experimental results well, and the kinetics were more accurately represented by a pseudo second-order model. The intercalation-reconstruction process was chemisorption nature mainly through hydrogen bond forces, followed the exchange of interlayer -OH anions and SO42-.