Ammonium Ion Removal with a Natural Zeolite in Monodispersed and Segregated Fluidized Beds

This study focuses on the dynamic behavior of ammonium ion uptake during continuous operation with respect to liquid by means of ion exchange with a natural zeolite in fluidized and segregated fluidized beds. The major operating variables affecting the performance in both types of fluidized beds are particle size, bed expansion, and flow rate. Use of particles of about 300 mu m size in monodispersed fluidized beds resulted in breakthrough capacities of about 0.5 meq/g or higher, with contact times in the order of 0.7-5.5 min. The column efficiencies in terms of breakthrough capacity/total capacity were in the order of 0.42-0.61. The segregated fluidized bed, as achieved by using two nonmixing particle size fractions, is a hybrid fluidized bed consisting of an expanded bed with reduced mixing which is topped by a regular fluidized bed. Segregation increased the column efficiency to 0.69 when a combination of 250-300 and 500-600 mu m sized particles were fluidized with a contact time of 1 min. The breakthrough capacities for the segregated fluidized beds with the finer particle size combination were 0.60-0.89 meq/g. A new representation of the breakthrough curves in terms of C/C(0) versus a dimensionless time t/t(f) suggests that these plots are a valuable tool for comparing performances for a wide variety of experimental conditions. The results of this study indicate that fluidization can well be applied to ion exchange operations to accommodate high influent flow rates.