Removal of Ammonia From Water Using Nanoscale Zero Valent Irons Modified Fly Ash-Derived Zeolite Adsorbents

Fly ash-derived zeolite A was impregnated with different weigh ratios of nanoscale zero valent irons to produce new adsorbents (x) Fe-Z. Adsorbents were tested to remove ammonia from water solutions. Simultaneous removals of ammonia were examined via batch adsorption experiments. The new adsorbents were characterized by the X-ray diffraction (XRD), Brunauer-Emmett-Teller-N2 surface areas, pore size distributions, Transmission Electron Microscope (TEM) and Hysteresis loops in order to probe effects of the weigh percentages of NZVI impregnated. Virgin and exhausted adsorbents were examined via X-ray photoelectron spectroscopy (XPS) analyses to elucidate adsorption mechanisms. Maximum adsorption capacity of the ammonia for (50) Fe-Z adsorbent was 50.2mg/g. The maximum adsorption capacity of (50) Fe-Z is more than that of other adsorbents for ammonia removal from water. The performance was affected by the pH of aqueous solution, the initial concentration and reaction temperature. The adsorption mechanisms of ammonia on (x) Fe-Z are attributed to the ion exchange and electrostatic adsorption. Some parts of NZVI were oxidized and substituted the aluminum in the framework of zeolite A in the synthesis process of (x) Fe-Z. It made more sodium ions be exchanged with positive ions after NZVI impregnated into zeolite A. In addition, the negative surface charge of (x) Fe-Z attracted the positive ammonia ions. Furthermore, the dispersion of NZVI on the surface of (x) Fe-Z was benefit for (x) Fe-Z to be separated magnetically. Moreover, the presence of iron hydroxide promoted adsorption of ammonia on the surface of (x) Fe-Z.