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Effect of modifiers on the ion exchange properties of borosilicate glasses

Jayshree Ramkumar ,  Vv Sudarsan ,  Rk Mishra ,  Aweshkumar Tyagi ,  Tulsi Mukherjee 


Borosilicate glasses with barium oxide modifier BBS [(Na2O)0.143(B2O3)0.268(SiO2)0.473(BaO)0.116] and without modifier SBS [(Na2O)0.162(B2O3)0.303(SiO2)0.535] were used for the uptake of uranyl ion. The amount of metal ion taken up is expressed in terms of Kd which is a ratio of concentraiton of metal ion in solid to that left behing in solution. variation of Kd value with metal ion concentration for both SBS and BBS glass samples shows that the presence of BaO modifier (in BBS sample) improves the efficiency of metal ion uptake to a great extent. The variation of equilibration time at a fixed uranyl ion concentration showed that the Kd values increased to a maximum value after 24 h Therefore, all equilibrations were carried out for 24 h. It is seen that for uranyl ion, the Kd value increases a maximum at a concentration of 0.01 M (2380 ppm) and then decreases, This could be due to the fact that with increase in the sorbate concentration in solution, there is an increase in the amount left behind in solution after equilibration and this factor affects the value of Kd. The difference in ion exchange behaviour between the two glass samples could be due to the difference in the number of non-bridging oxygen atoms present as revealed by 11B and  29 Si MAS NMR studies. 29 Si MAS NMR patterns revealed the addition of BaO as modifier (BBS) results in the increase in the concentration of the Q3 structural units containing more non-bridging oxygen atoms. 11B MAS NMR patterns revealed that BBS contain only one sharp peak around –22 ppm, characteristic of the tetrahedrally coordinated boron (BO4)- structural units whereas for SBS, in addition to the sharp peak at –22ppm, a broad peak characteristic of trigonally coordinated boron (BO3) structural units is observed. The (BO4) structure is charge neutralized by Na+ ion. From 11B and 29Si MAS NMR studies, it is established that increase in the Si-O--Na+ and B-O- Na+ results in the higher exchange capacity of BBS.


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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium G, by Jayshree Ramkumar
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-04-26 13:35
Revised:   2009-06-07 00:44