Recycling of typical difficult-to-treat e-waste: Synthesize zeolites from waste cathode-ray-tube funnel glass

The disposal of waste cathode ray-tubes (CRTs) from old televisions and discarded computer monitors has become a major environmental concern worldwide. In this work, an open-loop recycling method was developed to synthesize zeolites using CRT funnel glass as the raw material. The effects of hydrothermal temperatures and pressure, n(SiO2/Al2O3) molar ratios and hydrothermal time on the resulting products were investigated. The results indicated that hydrothermal temperatures and pressure played critical roles in zeolite synthesis. Amorphous phases were detected at lower temperatures (80-100 °C) and pressure (0.47-1.01 bar) with n(SiO2/Al2O3) = 2.0. At the temperature of 110 °C (pressure 1.43 bar), NaA formed with a mixture of NaP1 and Faujasite. With further increase in the temperature and pressure, the unstable NaA and Faujasite disappeared, and Hydroxysodalite developed. The influence of n(SiO2/Al2O3) ratios on resulting products revealed a single phase of NaA was formed at the ratio of 1.5 and a mixture of NaA and Faujasite at the ratio of 2.0. Prolonging hydrothermal time, however, could promote zeolite crystallization, and NaA gradually developed with an increase in the time from 2 to 6 h at n(SiO2/Al2O3) = 1.5. By comparison, crystallization phases were observed only when the time was longer than 8 h at n(SiO2/Al2O3) = 2.0.