Ammonium continuous removal by zeolite P synthesized using fly ash combined with bacteria in aqueous solution

The new composite product synthesized by zeolite P and bacteria consisting of nitrobacteria and denitrobacteria can efficiently and continuously remove ammonium in solution through zeolite adsorption and bacteria degradation. In this study, we used fly ash to prepared zeolite P, and then combined bacteria to synthesize the composite product. The adsorption efficiency and mechanism of products for ammonium were further studied by batch and dynamic experiments, and adsorption model. The zeolite P with a relative crystallinity of 84.7% was synthesized using fly ash by an alkali fusion-hydrothermal method. The synthetic zeolite P could combine with bacteria to be prepared an integral adsorption composite that had hierarchical pore structure including macropores, mesopores, and micropores, and its maximum compressive strength reached 106.2 N. The zeolite P could remove ammonium from solution, and Freundlich, Temkin, and Dubinin-Radushkevich models as well as thermodynamic models all showed that the ammonium adsorption by zeolite was mainly physical adsorption. Thus, the adsorbed ammonium was easy to be desorbed and became the nitrogen source for bacteria in composites. By batch experiments, the ammonium adsorption rate of composite product was significantly improved (P < 0.05) compared with zeolite P due to zeolite adsorption and the bacteria degradation. Through dynamic experiments, the composite product could efficiently and continuously remove ammonium from solution than zeolite P and bacteria alone. Therefore, the composite product could form a stable system for the adsorption, desorption, and degradation of ammonium in solution.