The study of CRT funnel glass recycling by SiO₂ coating-stabilization process

Traditional cathode ray tube (CRT) monitor contains hazardous components, such as lead (Pb), which is harmful to environment. If CRT is not properly disposed, the heavy metal can be released into the environment under acid condition, such as acid rain. Therefore, the Pb-contained glasses cannot be recycled as conventional non-hazardous glass, such as container glass. One way to treat CRT glass is to prevent the release of heavy metal. This work proposed a method to prepare SiO₂ protected waste funnel glasses via sol-gel process to prevent the release of Pb heavy metal. Thus protected Pb-contained glass can have the potential for further applications. The SiO₂ sols were first prepared by the hydrolysis and condensation of Si precursor, tetraethyl orthosilicate (TEOS) in ethanol with ammonia water as the catalyst. The generated SiO₂ particle samples were characterized by scanning electron microscopy (SEM) for surface morphology, and electron spectroscopy of chemical analysis (ESCA) and total reflection X-ray fluorescence(TXRF) for surface element identification, and atomic absorption spectrometry (AAS) for acid leaching. The correlation between the preparation conditions and the size of sol-gel synthesized silica (SiO₂) was discussed. It was found that the waste funnel glass was entirely covered by SiO₂ particles after repeated sol-gel coating process. Examination of SiO₂-covered waste funnel glass by ESCA showed completely decay of Pb signal at the surface region, indicating successful stabilization of waste funnel glass via SiO₂ protecting layer. After stabilization, the waste funnel glasses can be used in water permeable brick. This treatment process can solve the waste problem. Even become a building material that have high economic value and practicability.