الفهرس 
Material and methodsOnly 14 pages are availabe for public view
 |  | from | 127 |  |  |
| | | from | 127 | | |
Abstract
The present investigation was carried out to (1) study the adsorption of
P on different-soil materials represented by the natural soils (calcareous,
alluvial and sandy), clay minerals (altapulgite, kaolinite and montmorillonite)
and oolitic limestone fractions via using Langmuir, Van-Huay and Freundlich
isotherms. (2) test the fitness of the adsorption data obtained over a wide
range of equilihrium concentrations (represented by the whole curve) and that
of different destinct regions through this range corresponding to two or three
linear portions of the whole curve with the above mentioned isotherms, (3)
evaluate the effect of the successive water extractions on P release from the
treated materials, and (4) throw further light on the adsorption and desorption
of Zn and Cu on the alluvial and calcareous soils.
To fulfill these objectives, laboratory experiments were conducted on P ,.
sorption and desorption where a wide range of P concentrations (0-100 Jlg
mL-l) were equilibriated with the different” adsorbents and the relation
between equilibrium concentrations ”c” and c/x/m was established for each
material; the obtained curve has been observed carefully and devided to two or
three linear portions. The fitness of the adsorption data for the whole curve
and each portion was tested again through the corresponding ranges (regions)
of equilibrium P concentrations, using Langmuir, Van-Huay and Freundlich
isothem IS.
Sorbed P was extracted by distilled water seven successive extractions.
100
A greenhouse experiment was conducted on the natural five soils and
Zea mays L. plant was selected as an indicator plant. Phosphorus was applied
at 0.10” 20.40 and 100 mg kg-I soil and the plants were harvested after 45
days.
The retention and release of Cu and Zn were studied on the alluvial.
and calcareous soils.
The obtained results can be summarized as follows:
1- Phosphorus sorption:
1- Phosphorus sorption on the natural soils:
I- The adsorption data for the whole curve fitted to Van-Huay and
Freundlich isotherms. However a slightly decrease in fitness was observed
with Langmair isotherm. Resolving the whole curve into two or three portions
and investigating data of corresponding P concentrations through each portion
(region) increased the fitness of all isotherms to that data, particularly in
region (I) of equilibrium P concentrations not exceeding 11 mg P t-t.
2- The obtained Pmax values calculated according to Langmuir for the
natural soils over a wide range of P concentrations ranged from 1261.45 to
3757.56 mg P kg-1 and the affinity constant ranged from 0.007 to 0.035 mg-I.
3- The empirical values of Pmax of Van -Huay isotherm ranged from
411.5 to 1770 mg kg-I, the higher Pmax value was recorded for the alluvial
soil which contains high clay content (58.7%)