Boroaluminosilicate glasses as ion exchange materials

Sodium boroaluminosilicate glasses, (Na ₂O) _0.22(K ₂O) _0.029(B ₂O ₃) _0.05(SiO ₂) _0.69(Al ₂O ₃) _0.011 and (Na ₂O) _0.05(K ₂O) _0.029(B ₂O ₃) _0.22(SiO ₂) _0.69(Al ₂O ₃) _0.011 having different B ₂O ₃ to Na ₂O mole ratio of 0.23 and 4.4 respectively were investigated for their uptake characteristics of cationic dyes, namely Rhodamine 6G and methylene blue, from aqueous solutions. Both the glasses have been found to adsorb these dyes. However, the glass with B ₂O ₃ to Na ₂O ratio of 0.23 is found to have more uptake capacity with 2.5 and 1.8 mmol of Rhodamine 6G and methylene blue respectively per gram of the glass sample. For Rhodamine 6G dye, the amount of uptake by glass is found to be significantly higher than that of conventionally used activated charcoal (0.1 mmol/g). Based on ²⁹Si and ¹¹B magic angle spinning nuclear magnetic resonance technique, it is confirmed that the increased concentration of Si-O ^- Na ⁺ and BO ₄ ^- Na ⁺ linkages present in the glass with B ₂O ₃ to Na ₂O mole ratio of 0.23 is responsible for the increase in its uptake of the dye compared to the glass sample with B ₂O ₃ to Na ₂O mole ratio of 4.4. From fluorescence studies, incorporation of the dye molecules in the glass matrix is confirmed. The present study is quite relevant for the removal of dye molecules present in untreated aqueous solutions generated from the textile industry.