Hydrothermal Treatment of Liquid Crystal Using a Batch Reactor

Liquid crystals, contained in Liquid Crystal Display (LCD), would cause undesirable impacts on the environment and human health if not treated properly. Converting the waste liquid crystal into harmless product has aroused worldwide attention. In the present work, hydrothermal technology was applied to treat the liquid crystal of 4-octoxy-4'-cyanobiphenyl, which is one of the most common used liquid crystals in LCDs. The experiment was carried out in a 5.7 mL stainless tube reactor and heated by an oven. The effect of reaction temperature and reaction time on degradation rate was evaluated and the analysis was conducted with High Performance Liquid Chromatography (HPLC). The degradation products in liquid phase were analyzed with Gas Chromatography/Mass Spectrometer (GC/MS). Results indicate that the degradation rate improved along with the increase of reaction temperature and reaction time. At 300 C and with the reaction time of 90 min, 99.8% of 4-octoxy-4'-cyanobiphenyl could be degraded into simple and environmental innocuous products and its environmental risks were finally eliminated.