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Ammonium Nitrate Occlusion vs. Nitrate Ion Exchange in Natural Zeolites
Author(s) -
Park Man,
Komarneni Sridhar
Publication year - 1998
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1998.03615995006200050044x
Subject(s) - chemistry , ammonium , zeolite , salt (chemistry) , ion exchange , nitrate , inorganic chemistry , kinetics , cation exchange capacity , molten salt , ion , catalysis , soil water , organic chemistry , physics , environmental science , quantum mechanics , soil science
Several salts, such as NH 4 NO 3 and KNO 3 , can be occluded in natural zeolites through molten salt treatments, which increase the capacity of zeolites to store nutrients in addition to exchangeable cations. Zeolites occluded with NH 4 NO 3 are potential candidates as slow‐release fertilizers. This study focuses on determining the rates of NH 4 NO 3 uptake by natural zeolites from molten salt and on evaluating kinetics of ion release from NH 4 NO 3 ‐occluded zeolites. The kinetics of ion release from NH 4 NO 3 ‐occluded zeolites were compared with those of NH + 4 ‐saturated zeolites. NH 4 NO 3 ‐occluded zeolites were prepared by treatment in molten NH 4 NO 3 at 185°C for different time periods, or at 250°C for 4 h. Uptake of molten NH 4 NO 3 by erionite apparently reached equilibrium after 8 h of treatment at 185°C. The total N uptake by NH 4 NO 3 ‐occluded zeolites was not related to cation‐exchange capacity but depended on the structural type of the zeolite. Approximately a twofold increase in total N loading capacities of zeolites was achieved through salt occlusion compared with NH + 4 exchange from solution. For example, phillipsite exhibited a N loading capacity of 76 g N kg ‐1 when treated with molten NH 4 NO 3 , but showed a capacity of only 46 g N kg ‐1 through NH + 4 exchange. A simulated soil solution was used to examine the kinetics of ion release from both NH 4 NO 3 ‐occluded and NH + 4 ‐saturated zeolites. Occluded NH + 4 and NO ‐ 3 were released slowly and steadily as in the case of exchanged NH + 4 alone from zeolites during 30‐d treatment in a simulated soil solution. It is evident from this study that salt‐occluded zeolites are potential candidates as slow‐release fertilizers.