ISSN:
1435-0661
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
+ 4 adsorption and desorption were investigated on the natural zeolite clinoptilolite to ascertain its ability to adsorb and release the important plant nutrient N in its NH+ 4 form at various pH values and initial NH+ 4 concentrations. Kinetics of NH+ 4 adsorption were evaluated on the samples using solutions containing 140.1, 280.2, 560.4, and 840.6 mg L-1 of NH+ 4 -N at pH 4, 5, 6, and 7, equilibrated for 5, 10, 15, 20, 30, 45, 60, 75, 90, and 120 min. Samples for NH+ 4 desorption were equilibrated with 70.1, 280.2, 560.4, and 1401 mg L-1 NH+ 4-N solution at pH 4, 5, 6, and 7 for 2.5 h, and adsorbed NH+ 4 extracted with 2 M KCl for 5, 10, 20, 30, 45, 60, 90, 120, 150, 180, and 300 min. Equilibrium time for NH+ 4 adsorption ranged from 60 min for 140.1 mg L-1 initial NH+ 4-N concentration at pH 4 to 120 min for 840.6 mg L-1 initial NH+ 4-N concentration at pH 7. Desorption was nearly complete in 150 min for low initial NH+ 4 concentrations and 200 min for high initial NH+ 4 concentrations. Amounts of NH+ 4 sorbed increased with increasing pH and initial NH+ 4 concentrations. Models evaluated included the first-order kinetics, modified Freundlich, parabolic diffusion, Elovich, and heterogeneous diffusion. All the models adequately described the NH+ 4 adsorption process, with r2 values ranging from 0.955 to 0.999. With the exception of first-order kinetics, they also described the desorption process well, with r2 values ranging from 0.897 to 0.999, for all pH and initial NH+ 4 concentrations. Reaction rate coefficients (k) were calculated from the modified Freundlich model and ranged from 0.134 to 0.193 min-1 for the adsorption process, and 0.129 to 0.226 min-1 for the desorption process. The models indicated that NH+ 4 adsorption and desorption by the zeolite was controlled. Data from this study indicated the potential use the tested natural zeolite as an NH+ 4 adsorbent and a controlled-release NH+ 4 ferrtilizer.
Type of Medium:
Electronic Resource
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