Sodium borosilicate glass produced from coal fly ash upon vitrification in an induction-melting furnace

Sodium borosilicate glasses were produced from coal fly ash and their properties were investigated. Fly ash could be vitrified completely by induction heating at 1500 C for 30 min with Na2O or B2O3 additions of more than 10 wt.%. The induction furnace incorporated a new method, namely, induction susceptor heating and employed a cyrindrical graphite rod as the susceptor that could efficiently capture the electromagnetic energy. The alkali borosilicate glasses produced had Vickers microhardness of 3000-4000 MPa, bending strength of 30-40 MPa and indentation fracture toughness of 0.7-1.1 MPa. m(1/2). With suitable Na2O and B2O3 addition, their melting points decreased down form 1500 degrees C to less than 1200 degrees C. Finally, their chemical resistances against acid leaching indicated that heavy metals were immobilized well under environmental regulation. Therefore, alkali borosilicate fly ash glasses should be recycled as materials with good chemical resistance.