Defluoridation of Water by Schwertmannite

In the present study Schwertmannite (an iron oxide hydroxide) is selected as an adsorbent for defluoridation of water. The adsorbent was prepared by wet chemical process and was characterized by SEM, XRD and BET. The fluoride adsorption efficiency of the prepared adsorbent was determined with respect to contact time, initial fluoride concentration, adsorbent dose and pH of the solution. The batch adsorption data revealed that the fluoride adsorption efficiency was highly influenced by the studied factors. Equilibrium was attained within one hour of contact time indicating fast kinetics and the adsorption data followed pseudo second order kinetic model. Equilibrium isotherm data fitted to both Langmuir and Freundlich isotherm models for a concentration range of 5-30 mg/L. The adsorption system followed Langmuir isotherm model with maximum adsorption capacity of 11.3 mg/g. The high adsorption capacity of Schwertmannite points towards the potential of this adsorbent for fluoride removal from aqueous medium.

Authors:

• Aparajita Goswami
• Mihir K Purkait

Keywords:

• Adsorption
• fluoride
• isotherm study
• kinetics
• schwertmannite.

References:

[1] Meenakshi and R.C. Maheshwari, "Fluoride in drinking water and its
removal," J. Hazard. Mater, 2006, vol 37, pp. 456.
[2] W.H.O. (World Health Organisation), Guidelines for drinking water
quality, Vol. 2. Health criteria and other supporting information, 2nd ed,
World Health Organisation, Geneva, 1996, pp. 231-237.
[3] WHO, Guidelines for drinking-water quality, 3rd edition, incorporating
first and second addenda. 2006, vol. 1.
[4] N. Viswanathan and S. Meenakshi, "Role of metal ion incorporation in
ion exchange resin on the selectivity of fluoride," J. Hazard. Mater,
2009, vol. 162, pp. 920-930.
[5] A. Goswami and M.K. Purkait, "Kinetic and Equilibrium Study for the
Fluoride Adsorption using Pyrophyllite," Sep. Sci. Tech., 2011, vol. 46,
pp. 1-11.
[6] P. Sehn, "Fluoride removal with extra low energy reverse osmosis
membranes: three years of large scale field experience in Finland,"
Desalination, 2008, vol. 223, pp.73-84.
[7] A. Goswami and M.K. Purkait, "The defluoridation of water by acidic
alumina," Chem Eng Res Des, in press.
[8] A. Tor, N. Danaoglu, G. Arslan, and Y. Cengeloglu, "Removal of
fluoride from water by using granular red mud: Batch and column
studies," J. Hazard. Mater, 2009, vol. 164, pp. 271- 278.
[9] S. Kagne, S. Jagtap, P. Dhawade, S. P. Kamble, S. Devotta, and S. S.
Rayalu, "Hydrated cement: A promising adsorbent for the removal of
fluoride from aqueous solution," J. Hazard. Mater, 2008, vol. 154, pp.
88-95.
[10] S. Mandal and S. Mayadevi, "Cellulose supported layered double
hydroxides for the adsorption of fluoride from aqueous solution,"
Chemosphere, 2008, vol. 72, pp. 995-998.
[11] G. Lee, C. Chen, S. T. Yang, and W. S. Ahn, "Enhanced adsorptive
removal of fluoride using mesoporous alumina," Microp. Meso. Mat,
2010, vol. 127, pp. 152-156.
[12] A. Eskandarpour, M. S. Onyango, A. Ochieng, and S. Asai, "Removal of
fluoride ions from aqueous solution at low pH using schwertmannite," J.
Hazard. Mater, 2008, vol. 152, pp. 571-579.
[13] S. Lagergren, S., "Zur theorie der sogenannten adsorption gelöster
stoffe, Kungliga Svenska Vetenskapsakademiens," Handlingar, 1898,
vol. 24, pp. 1-39.
[14] G. Blanchard, M. Maunaye, G. Martin, "Removal of heavy metals from
waters by means of natural zeolites," Water Res, 1984, vol. 18, pp. 1501.
[15] I. Langmuir, I. "The adsorption of gases on plane surfaces of glass, mica
and platinum," J. Am. Chem. Soc, 1918, vol. 40, pp. 1361-1403.
[16] H. Freundlich, "Uber die Adsorption in Lösungen," Z. Physik. Chem,
1907, vol. 57, pp. 385-470.