Synthesis of magnetic 4A zeolite and its performance on ammonia nitrogen adsorption in water

Fe 3 O 4 @SiO 2 /4A magnetic nanocomposites (magnetic 4A zeolite) have been synthesized by hydrothermal method which endowed 4A zeolite with magnetic separation characteristics. XRD results showed that the magnetic 4A zeolite had the characteristic diffraction peaks of both 4A zeolite and Fe 3 O 4 . The SEM images displayed the combination of 4A zeolite and Fe 3 O 4 . N 2 physical adsorption showed that magnetic 4A zeolite had a large specific surface area and can provide a large number of adsorption sites for ammonia nitrogen. The magnetic separation results showed that magnetic 4A zeolite exhibited fast response to external magnetic field, and the saturation strength measured by VSM was 5.85 emu g −1 , indicating the superparamagnetic properties of magnetic 4A zeolite. The removal rate of ammonia nitrogen by FSA-M-1 sample reached to 43.18%. After 6 rounds of repeated adsorption experiments, each sample’s magnetic recovery rate was above 95%, and the removal rate of ammonia nitrogen was higher than 36%. Graphical abstract