Removal of Ammonia Nitrogen from Water by Modified Bentonites

Nitrogen removal is important to control eutrophication and adsorption is an efficient treatment process. In this paper, three modified bentonites, hydroxy-aluminum pillared bentonite (Al-Bent), hydroxy-iron pillared bentonite (Fe-Bent), and cetyl trimethylammonium exchanged organo-bentonite (CTMAB-Bent) were prepared, characterized, and its adsorption properties for ammonia nitrogen were evaluated in batch experiments. The results showed that the ability of ammonia nitrogen adsorption of modified bentonites was far more than that of raw bentonite. The adsorption capacity followed the order: Al-Bent > Fe-Bent > CTMAB-Bent > raw bentonite. The adsorptive rate of ammonia nitrogen on the adsorbents fitted pseudo-second order kinetic models well (R² > 0.90). The Freundlich model and the Langmuir model were both described the adsorption isotherm data well. These results indicate that the modified bentonites are potential adsorbents for ammonia nitrogen removal from water.