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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. |