Synthesis of Zeolite A from Aluminoborosilicate Glass Used in Glass Substrates of Liquid Crystal Display Panels and Evaluation of Its Cation Exchange Capacity

摘要

Synthesis of zeolite A from aluminoborosilicate glass used in liquid crystal display (LCD) panel glass substrate was attempted. Mixture of aluminoborosilicate glass and sodium aluminate was hydrothermally treated with sodium hydroxide solution for 10.8-345.6 ks at 368-423 K. Aluminoborosilicate glass was also acid treated with nitric acid before hydrothermal treatment. Obtained samples were characterized by X-ray diffraction and scanning electron microscope observation. Zeolite A, hydroxysodalite, and zeolite P were synthesized, and with the specific conditions of hydrothermal treatment, a single phase of zeolite A was successfully obtained. Acid treatment was effective for synthesis of a single phase of zeolite A, because the components of aluminoborosilicate other than SiO_2 preferentially eluted for acid solution and during following hydrothermal treatment SiO_2 was supposed to elute for alkaline solution. Cation-exchange capacities (CECs) were investigated for these products. It was clarified that CEC of the product with a single phase of zeolite A obtained from alu-minoborosilicae glass was 4.2 mol/kg. CEC of the product consisted of zeolite A and hydroxysodalite was 3.9 mol/kg, and the one consisted of zeolite A, hydroxysodalite, and zeolite P was 2.6 mol/kg. This results shows that aluminoborosilicate glass could be expected to be recycled in zeolite A with good CEC by the appropriate process.