title: Maximizing ammonium nitrogen removal from solution using different zeolites.
abstract: Zeolite minerals are ideal for removing ammonium nitrogen (NH4(+)-N) from animal wastes, leachates, and industrial effluents. The objectives of this study were to compare NH4+ removal and kinetics among several commercially available zeolites under various conditions and determine if calorimetry could provide information regarding kinetics of NH4+ removal. Ammonium sorption onto potassium (K) saturated zeolites was compared using synthetic vs. natural swine effluent and with either traditional batch-shaken system or a "tea bag" approach in which zeolites were contained in a mesh sack and suspended in a solution of swine effluent. Ammonium sorption was measured at four retention times using a flow-through system, and the resulting heat response was measured using isothermal calorimetry. Ammonium removal was not significantly different in synthetic vs. natural swine effluent. Ammonium removal was lower in batch-stirred compared to batch-shaken systems, suggesting that diffusion between particles was rate-limiting in the former system. Flow-through cells possessing contact times > 100 s displayed greater NH4+ sorption than batch systems, suggesting that maintaining high NH4+ concentration in solution, removal of exchange products, and sufficient reaction time are critical to maximizing NH4+ removal by zeolites. Within 100 s after NH4+ addition, endothermic heat responses indicated that NH4(+)-K+ exchange had peaked; this was followed by significant heat rate reduction for 50 min. This confirmed findings of an initial fast NH4(+)-K+ exchange followed by a slower one and suggests the 100-s period of rapid reaction is an indicator of the minimum flow through retention time required to optimize NH4+ sorption to zeolites used in this study.
authors.affiliation: Dep. of Plant and Soil Science, Oklahoma State Univ., 367 Agricultural Hall, Stillwater, OK, 47078-1020, USA. chad.penn@okstate.edu
authors.forename: Chad J
authors.initials: CJ
authors.lastname: Penn
authors.forename: Jason G
authors.initials: JG
authors.lastname: Warren
authors.forename: Savannah
authors.initials: S
authors.lastname: Smith
mesh_terms: D000818:Animals; D007700:Kinetics; D008372:Manure; D009584:Nitrogen / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013552:Swine; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry; D018508:Water Purification / Q000379:methods*; D017641:Zeolites / Q000737:chemistry*
chemical_list: D008372:Manure; D000644:Quaternary Ammonium Compounds; D014874:Water Pollutants, Chemical; D014867:Water; D017641:Zeolites; D009584:Nitrogen