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Kinetics of Fixation of Iron and Zinc Applied as FeEDTA, FeHDDHA and ZnEDTA in the Soil
Author(s) -
Lahav N.,
Hochberg M.
Publication year - 1975
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/sssaj1975.03615995003900010017x
Subject(s) - adsorption , chemistry , zinc , analytical chemistry (journal) , reaction rate constant , kinetics , effluent , fixation (population genetics) , nuclear chemistry , chromatography , physics , environmental engineering , biochemistry , organic chemistry , quantum mechanics , engineering , gene
The disappearance of zinc and iron from soil solution after their addition as soluble metal chelates is attributed to adsorption and fixation. The value of the adsorption coefficient, K d , was estimated from a batch experiment but because of the inaccuracy involved they were evaluated from the breakthrough curves of column experiments using Rehovot sand. FeEDDHA was neither adsorbed nor was its iron fixed by the soil to any significant extent. The fixation of iron applied as FeEDTA was found to be a first order reaction. Assuming that the fixation reaction kinetics is similar in both the solution and the solid phase, then the reaction rate constant can be expressed as k = ( k 1 θ + k 2 ρ K d )/(θ + ρ K d ), where k 1 and k 2 are the reaction rate constants in the liquid and solid phases, respectively. θ is the volumetric water content and ρ is the bulk density. By using 5 different soil/water ratios, the values of k 1 and k 2 were found to be 0.0096 h ‐1 and 0.087 h ‐1 , respectively. The value of k was also estimated from the breakthrough curve in a column experiment by using the relative effluent concentration under steady state condition ( C/C o ) s . The adsorption of ZnEDTA was negligible under the present experimental conditions. Thus k = k 1 and is independent of the water content and bulk density. This was shown by comparing the results of the two experimental techniques. The value of k 1 thus found was 0.084 h ‐1 . The first order model of the fixation reaction of zinc applied as ZnEDTA is applicable for time periods up to 8 to 10 hours.