الفهرس 
Use of Nile Alluvium Nano-Clays for Removal of Cadmium and Copper Ions from Aqueous SolutionsOnly 14 pages are availabe for public view
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Abstract
The objectives of this study were to prepare and characterize nano-clay particles from an alluvial Nile Delta Egyptian soil and to understand and evaluate its efficacy for removal of Cd
and Cu metal ions from aqueous solutions.
Five surface soil samples (0-15 cm) of a Clay textured soil were randomly collected from Itay-Elbaroud Agricultural Experimental Station, Albuheirah Governorate and a composite
sample was made. characterization of the main chemical and physical soil properties were performed using standard methods(Clay texture, EC: 1.23 dS/m, pH: 8.36, CaCO3: 4.79%, OM: 4.38%, CEC: 57 cmolc/kg). The inorganic soil clay fraction was obtained from the
composite soil sample using free sedimentation procedure after appropriate pretreatments.
The main findings of this study can be summarized as follows.
1- characterization of nano-clay particles:
The obtained soil clay fraction (Clay) was used to prepare a nano-clay material (N-Clay) using the ball mill method. characterization of both soil clay and nano-clay were conducted using scanning electron microscope (SEM) to assure particle sizes, coupled with energy
dispersive spectroscopy (EDAX) to examine the surface morphology and elemental composition. Fourier transform infrared (FT-IR) spectroscopy analysis was carried out in the range of 400–4000 cm−1to study the compositional properties and the functional groups of
the nano-clay surface using. X-ray diffraction (XRD) was performed on an X-ray diffractometer to determine the crystal structure. Surface area of the adsorbents was determined using N2 sorption isotherms run on a surface area meter coupled with the Brunauer-Emmett-Teller (BET) method.
image of scanning electron microscope (SEM) of Clay and N-Clay particles prepared by ball milling. The image shows the platy structure and the typical surface morphology of the
N-Clay adsorbent which is a characteristic of clay minerals. The sizes of N-Clay granules were in the range of nano scale (less than 1 micron). The platy nano-clay particles also appear to stick together to form aggregates of different shapes and sizes. This configuration is
expected to create multiple interlayer spacings. Results of EDAX analysis of Clay and N-Clay adsorbents revealed that Al and Si elements are the major constituents in both the Clay and NClay structure.
The XRD patterns revealed the existence of montmorillonite, kaolinite, and quartz. These patterns of Clay and N-Clay align with those of the commercial montmorillonite indicating
the dominance of montmorillonite clay minerals in the two adsorbents. The calculated crystallinity percentage of Clay and N-Clay was 87.2% for Clay and 59.2% for N-Clay. The decrease in crystallinity N-clay particles may be attributed to the mechanical milling action which may have led to limited destruction of some mineral crystals.
The obtained FT-IR spectra showed a large similarity between Clay and N-Clay in their absorption bands which represents the main characteristic bands for identification of montmorillonite and montmorillonite reach clays.
The surface area of N-Clay was higher than that of Clay (1.11×102
and 9.01 m2g
-1 respectively). However, the mean pore diameter showed an opposite trend of the surface area (Clay > N-Clay).
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2. Factors affecting adsorption of metal ions on nano-clay particles:
Results of Cd and Cu adsorption on nano-clay particles at different pH values (4, 7 and 9) revealed that increasing the pH cause a significant increase in the adsorbed amount of the two
metals on Clay and N-Clay. This likely suggest Cd and Cu ions were strongly bound to the hydroxyl groups on the edges of the clay minerals at higher pH value.
Clay and N-Clay suspensions showed high resistance to pH changes. The pH of
suspensions after 30 min, from the start of the experiment, decreased by about one to two units from pH 9 down to 6.5-7. This can be attributed to the high buffering capacity of montmorillonite, which is a characteristic of the used clay The removal of Cd and Cu ions from the aqueous solutions increased as the doses of the Clay and Nano-clay were increased from 0.5 to 10.0 g L-1
. However, the metal ions removal
percentage did not show a significant increase at adsorbent doses higher than 2.5 g L-1. This may be due to higher probability of collision and more chances for metal ions to contact with
the adsorption sites when the adsorbent dosage was less than 2.5 g L-1.
Increasing the initial Cd and Cu concentration (10, 25, 50,100 and 150 mg L-1) led to an
increase in the amount of metal adsorbed (qe, mg Cu g-1adsorbent) by both absorbents. The slope of the qe-C0 curve was steep upwards till the initial ion concentration of 50 ppm indicating a high adsorption capacity of the two adsorbents.
Statistical analysis of the effect of contact time (5, 10, 15, 20, 30, 45 min., 1, 1.5, and 2 hrs) revealed that removal of Cd and Cu ions increased significantly with contact time up to
30 min. For a contact time greater than 30 min., no significant increase in metal ions removal was recorded. The 30 min. contact time needed to reach maximum adsorption or equilibrium
of the system may indicate the rapid nature of adsorption on the two adsorbents investigated.
Data of the effect of temperature (298, 303, 3.08 and 313 :K) on Cd and Cu removal from aqueous solutions showed that the higher the temperature, the lower the removal of both metal
ions from the aqueous medium by either Clay or N-Clay. This effect may be due to increasing the kinetic energy of metal ions, increasing the activities of the mineral’s surface, and decreasing the resistance to mass transfer.