Iodide recovery from thin film transistor liquid crystal display plants by using potassium hydroxide - driven forward osmosis

Abstract

For the first time, KOH in the waste stream of a thin film transistor liquid crystal displays (TFT-LCD) plant was utilized as a draw solution to recover iodide in the waste stream through forward osmosis (FO). In long-term operation, the pressure-retarded osmosis mode provided concentration efficiency greater than that of the FO mode. The maximum water flux achieved 11.7 LMH at pH 11 of KOH draw solution, and the iodide concentration reached 6.9% for reuse in TFT-LCD plant from the initial iodide concentration of 0.6% after 120h. Analysis of scanning electron microscopy and energy dispersive X-ray spectroscopy images revealed a thin fouling cake layer of KI on the support layer of the membrane. The overall performance of the proposed FO system with KOH as the draw solution indicated that the FO system is promising for concentrating iodide for reuse in TFT-LCD plants. The proposed FO system offers excellent benefits: (1) the liquid discharge is minimal and (2) the cost of the FO system is extremely low because draw solution recovery is not required.