Volume No. 2 Issue No.: 4 Page No.: 505-512 April-June 2008

 

ADSORPTIVE REMOVAL OF As(V) FROM AQUEOUS SOLUTION USING NATURAL MORDENITE AND MODIFIED FORMS AS MEDIA

 

Pratap Chutia, Shigeru Kato, Toshinori Kojima and Shigeo Satokawa*

Department of Materials and Life Science, Faculty of Science and Technology, Seikei University, Tokyo (Japan)

 

Received on : September 06, 2007

 

ABSTRACT

 

Natural mordenite (NM) produced in Japan and its modified forms were investigated with respect to their sorption efficiency for arsenate ions (As(V)) from water. Two modified natural mordenite examined were aluminum treated natural mordenite (Al-NM) and acid treated natural mordenite (AT-NM). The adsorption experiments were performed by batch equilibrium technique. Effects of equilibrium time, initial arsenic concentration (in the 5-100 mgL-1 range) and pHs (in the range 3-12) were investigated. The Al-NM was superior to NM and AT-NM. This could be the fact that concentration of terminal Al-OH groups took the key role in ion-exchange taking place during adsorption. The concentration of this aluminol group in Al-NM is higher than the other two due the externally loaded Al-sites. Moreover, surface area of NM increased remarkably on Al3+-loading which enhances the adsorption process. The obtained results indicated that maximum As(V) uptake of 52.06, 67.04 and 74.91 % were observed at 24, 36, 48 h by NM, Al-NM and AT-NM respectively. After the equilibrium time, no adsorption observed due to saturation of adsorbent active sites. With the increase of initial As(V) concentration, metal uptake decreases for all the adsorbents up to a certain value after which it again became saturated. The maximum uptake was recorded at pH near respective pHPZC of the adsorbents. The arsenic removal by zeolite followed the first order kinetics indicating the adsorption is dependent on the concentration of metal only. The experimental data were fitted with Freundlich isotherm model.

 

Keywords : Natural mordenite, Zeolite modification, Arsenate, Point of zero charge, Ion-exchange, Adsorption, Isotherm models

 

 

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