الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 154 |  |  |
| | | from | 154 | | |
Abstract
The objective of this study was directed towards the full confirming
conditions of zeolite synthesis and its environmental application on the
removal of heavy metals from wastewater and uses as soil stabilization for
road base construction to improve its engineering properties (shrinkage and
swelling).
The bentonites used were collected from the area between 29° 32` N
and 30° 52` E at Fayum area where they are found in the form of a
horizontal bed about 4-5 m thick with hematite lenses and gypsum
intercalation with thickness about 10-15 cm. This bed is mainly covered by
about 50 cm weathering surfaceand the average content of studied bentonite is
SiO2 and Al2O3 51.57 % and 20.6 % respectively with ratio 2.5 and also contains
2.6% Fe2O3& L.O. I. 17%.
The XRD chart of the natural bentonitic clay sample indicating the
presence of montmorillonite, kaolinite, illite as clay minerals and quartz as
non-clay component. Morphology of the solid sample could be seen through
the use of scanning electron microscope (SEM) appear as aggregates of
irregular or hexagonal flakes or less commonly of thin laths and confirmed
by Energy-dispersive X-ray spectroscopy (EDX).
The Mechanism of the nucleation and crystallization process is
dependent on the type and concentration of alkali, cryastallization
temperature and aging period. Experimental procedure of zeolite synthesis
was studied at different condition of aging period and crystallization
temperature using two alkali solutions [KOH-NaOH] as a basic medium
during hydrothermal treatment method.2 g of bentonite sample and 25 ml of
different concentration of NaOH (1M, 3M, 5M) solution in a sealed Teflon
reactor were stirred at 60 °C for about 12 h.Then the samples were dried at
temperature 80 °C and 100 °C as crystallization temperature for different
aging period 48 h, 7 days.
Conditions that are mentioned above were used for another
concentration of KOH (1M, 3M, 5M) solution. After the hydrothermal
process is completed the reacting solution was decanted and samples were
washed several times using distilled water until pH reach to 7-8 using
centrifuge.The sample powders were dried in oven at 60-70 °C. The
products were collected and investigated by powder X-ray diffraction
(XRD) analysis, scanning electron microscope (SEM) and Energydispersive
X-ray spectroscopy (EDX).
Zeolites are synthesized under different crystallization temperature
(80 °C &100 °C) with NaOH concentration. Na-P1, Sodalite, zeolite ZK-14
are the major crystalline phases present in the product at 80 °C while Na-P1
and Natrolite phases at crystallization temperature100 °C showing
thatsodium hydroxide concentration affected on the type of the formed
zeolite and its degree of the crystallinity.
At concentration equal 3M after aging period 48 h and 7 days
sodalite with Na-P1 minerals formed with some traces of cancrinite at
temperature 80 °C and by increasing concentration to 5M two phase formed
each of them formed after aging period 48h as sodalite minerals as a sole
phase with some traces of quartz and the other zeolite ZK-14 formed after 7
days without any quartz relics.
The conversion process of the alumino- silicates to zeolitic products
through zeolitization process occurs via many steps. It starts with the
dissolution of the silica content in the starting material to give sodium
silicates forming an amorphous gel to that spontaneously yield sodalite
which on its turn, slowly transforms to cancrinite. At higher NaOH
concentrations, the solubility of SiO2 in the alkaline solution increased and
the SiO2/Al2O3 ratio of the produced zeolites increased and yields sodalitetype
zeolite
The XRD patterns in figures reveals that the hydrothermal treatment
of bentonite in KOH solution is characterized by the dissolution of the
starting material and the formation of amorphous and crystalline aluminosilicates
phases where at temperature 80 °C showed that Chabazite-k,
Zeolite F and Kalsilite the major crystalline phases present in the product
while at temperature 100°C Chabazite-K, Zeolite N and Natrolite are the
major phases.
It’s noticed that one phase of Natrolite formed at high concentration
of KOH (5M) and at aging period (7days). Chabazite-K one phase formed at
3M KOH and aging period 48 h and with increasing the aging period at the
same concentration Chabazite-K and Natrolite are formed. This supporting
that Natrolite formed at the aging period 7 days of crystallization.
One phase zeolite Na-P1 was used in this study in soil stabilization
for road base construction and in the removal of heavy metal for water
purification the condition of zeolite Na-P1 formed at 1M NaOH at 80 °C and
7 days aging period as a sole phase without any impurities.
Based on the model experiments it’s found that Na-P1 zeolite could
be used for binding of cations in the process of ion-exchange in order to
determine the effect of contact time and temperature of synthetic solution on
removal of individual and mixed solution of studied heavy metals (Pb2+,
Cu2+, Co2+, Ni2+). Adsorption has gradually increased where the removal of
Pb2+ reached to 99.96 % at room temperature as the same at 60 °C for 30
minute as contact time and the highest removal level for Cu2+ reached to
97.5 %, Co2+ 93.6 % and Ni2+ 17.14 % by raising temperature to 60 °C.
This study also studied the effect of other metal ion on the adsorption
of each metal when various heavy metals co-exist; the adsorption of a
particular heavy metals ion was influence by the other ions.
The removal of lead (99.75 %) was always enhanced by the presence
of other ions. On the other hand, the removal efficiency of Cu2+, Co2+ and
Ni2+ decrease by (91.5 %, 36 % and 7.2 %) respectively. The tests results
using real wastewater indicated that Na-P1zeolite can be used as a cheap
adsorbent for removing lead by percentage 99.7 % on room temperature and
60 °C for 30 minute as contact time.
The other basic objective of this study is to investigate the
modification of an expansive soils using synthetic Na-P1 zeolite type on the
swelling and shrinkage properties where the stabilization techniques make
the soil workable for construction and allow them decrease both swelling
and shrinkage by pozzolanic reactions between the additives and clay
minerals.
Based on the experimental results showing that decreasing of
swelling and shrinkage of the soil (250 to 10%) and from (20 to 5%)
respectively indicating that zeolite Na-P1 is an effective in the stabilization
of soil materials under road base or under foundation.