抄録
We tried to synthesize FAU zeolite from alumonoborosilicate glass used in liquid crystal displays, of which the discard volume is supposed to increase in the near future. The effect of hydrothermal process factor on the synthesis of FAU zeolite using aluminoborosilicate glass, which is poorly alkaline-soluble, was investigated. From X-ray diffraction, with increasing aging time before hydrothermal treatment, the production of FAU zeolite increased, whereas, that of zeolite P decreased. From inductively coupled plasma atomic emission spectrometry, the concentration of Si in the solution increased and that of Al decreased during aging. This indicates that aluminosilicate was generated from Si from aluminoborosilicate glass and Al from sodium aluminate. With aging time, generated aluminosilicate was aged, resulting in preferential synthesis of FAU zeolite. From scanning electron microscopy, increasing aging time resulted in a small crystal particle size of the synthesized FAU zeolite. At higher aging temperature than room temperature, the dissolution of aluminoborosilicate glass was accelerated, zeolite P increased. When NaOH concentration of aqueous solution decreased, zeolite A was synthesized. This indicates that aluminoborosilicate glass did not elute substantially, therefore low silica zeolite was generated. At higher NaOH concentration, FAU zeolite was generated because Na+ ion stabilized FAU zeolite and more Si eluted from aluminoborosilicate glass. Zeolite P which is a stable phase was generated when hydrothermal treatment temperature was high and treatment time became long. From nitrogen adsorption/desorption measurements, the microstructure of the obtained product was almost the same as the pure FAU zeolite. We clarified the potential of aluminoborosilicate glass as a starting material of FAU zeolite, widely used in catalysts, adsorbents, gas separation agents and so on.
