Study on Modified Zeolite Synthesized from Coal Fly Ash in Adsorption and Desorption of Ammonia Nitrogen

Abstract

The “Twelfth Five-Year” plan of China starts at the emission reduction task in controlling the total amount of ammonia nitrogen. Therefore, the method of how to remove ammonia nitrogen quickly and effectively will be the key point of wastewater treatment. In the current paper, One zeolite synthesized from coal fly ash (P-type zeolite, ZP) was prepared and then modified using lanthanum. The structure of the zeolite was characterized by means of SEM, X-ray, TG-DSC, and the like. The characteristics of ZP and lanthanum-modified ZP (LaZP) in the adsorption and desorption of ammonia nitrogen were simultaneously studied, wherein the results show that ZP and LaZP are featured with obvious crystal characteristics, lots of gap structures, and a strong characteristic peak of P-type zeolite shown in the XRD atlas. For the LaZP, the adsorption equilibrium can be carried out in 30 min. The data for the adsorption dynamics to the ammonia nitrogen are in line with the pseudo-second order kinetics equation, and the adsorption isotherme is well fitted to the Langmuir model. The regeneration test shows that the desorption rate of ammonia nitrogen is proportional to the concentration of NaCl when the pH is about 7. The desorption rate of LaZP to the ammonia nitrogen can reach 90% when the concentration of NaCl is 0.4 mol/l, and the desorption rate of ZP is 70%. Compared with ZP, the desorption speed of the LaZP is quicker, the adsorption equilibrium can be carried out in 6 h, and the adsorption equilibrium of ZP can be slowly carried out in 10 h. Moreover, the adsorption and desorption properties of the LaZP are greatly improved.