Desalination Of Brackish Water Based On Thermosensitive Materials

In this thesis, we have investigated the forward-osmosis (FO) desalination with poly(ionic liquid) hydrogels as smart draw agents and the thermosensitive properties of carbon quantum dots. The main results are as following:(1) We report a simple method to prepare thermo-sensitive poly(ionic liquid) (PIL) hydrogels as smart draw agents for FO desalination. These polyelectrolyte hydrogels produce a high osmotic pressure that can draw the desalinated water from brackish water into the hydrogel through a semipermeable membrane. Due to the thermo-sensitive nature of the PIL hydrogels, the liquid water can be easily recovered and the hydrogel can be re-used by temperature cycling. Moreover, the nontoxicity of the draw agents and the negligible draw solute leakage make the recovered water suitable for drinking. Due to their unique properties, the PIL hydrogels developed here are anticipated to find applications as smart draw agents in desalination of brackish water and in purification of contaminated water.(2) Employing the high temperature to form the carbon quantum dots grafted by the sodium sulphanilate. At the same time, we also find the density of the sodium sulphanilate on the surface of the carbon quantum dots, which enable us to tune the aggregation temperature of the carbon quantum dots after ions exchange method. On the other hand, the aggregation behavior of the carbon quantum dots is not only related to the ratio of the hydrophobic to hydrophilic ionic group, but also to the concentrations of the carbon quantum dots. The separation of the carbon quantum dots from the liquid can be conducted by elevating the temperature to induce their precipitation behavior. This work shows the potential application of the ionic liquid grafted carbon quantum dots as draw agents in the forward osmosis desalination.