تحضيرمواد حيوية – طين كمادة مازة فعالة لبعض الايونات المعدنية السامة من المحاليل المائية

Preparation of Iraqi Clay- Biomaterials as an Efficient Adsorbent for Some Toxic Metal Ions from Aqueous Solution

Abstract
This thesis investigated the use of Iraqi clay Ca-bentonite and modified clay
(Ca-bentonite-chitosan) as cheap and environmentally friendly adsorbent surfaces
for removal of pb (II) and Cr(III) ions from aqueous solutions. The influence of clay
amount, temperature, equilibrium time, and solution pH on adsorb of pb(II) and Cr
(III) ions onto Ca-bentonite and Ca-bentonite-chitosan clays from their synthetic
solutions in mono-system were studied by batch method. The results showed that
the removal efficiency and the maximum capacity of adsorption of pb(II), Cr (III)
ions on the modified clay higher than natural clay. The contact times were 50 and 45
min. for adsorption pb(II) ion on natural and modified clay respectively, but when
adsorption Cr(III), the contact times were 35 and 15 min. The optimum dosages of
natural and modified clay were 0.1 and 0.07 g for pb(II) ion adsorption, but when
adsorption Cr(III) ion, the optimum dosages were 0.3 and 0.1g for natural and
modified clay respectively. pH had a major effect upon adsorption of pb(II) and
Cr(III) ions in both systems, with the best adsorption of two ions occurred at pH = 5.
The experimental results for adsorption of pb(II) and Cr (III) ions onto natural
clay were achieved with Freundlich isotherms at three temperatures (298, 308 and
318) K. The adsorption process results of pb(II) were agreed with the Langmuir and
Freundlich isotherm models on modified clay ,but the Cr (III) ion on modified clay,
which is fitted to the Langmuir isotherm model only. Thermodynamic functions, for
instance, (ΔG, ΔH, and ΔS) were calculated from Van’t Hoff equations for
adsorption of pb (II) and Cr (III) ions on natural and modified clays. The values of
(ΔG) of both ions adsorption on two surfaces were negative, suggesting a
spontaneous adsorption process. The enthalpy values (ΔH) of pb(II) and Cr (III) ions
adsorption on natural and modified clays were positive, suggesting an endothermic
adsorption process. The entropy values (ΔS) of pb(II) and Cr (III) ions adsorption on
two surfaces were positive, suggesting an increase in randomness.