Desalination Of The Solutions By Forward Osmosis

Forward osmosis is a novel water treatment process that potentially can be used as an alternative for both traditional desalination and brine disposal technologies due to its less energy requirement and high recovery. Its applications have been developed in various fields, such as wastewater treatment, pharmaceutical and juice concentration, and seawater desalination, and even for water recycle use in spacecraft. In a FO process, a solution of considerably high concentration (known as draw solution) is utilized to generate a hydrostatic osmotic pressure gradient across a semi-permeable membrane to extract freshwater from a feed solution, which is on the other side of the membrane. The FO process is based on the osmotic pressure as a driving force. As a result, it can operate without high pressures and high temperatures. Similar to the RO process, the semi-permeable membrane as the barrier plays an important role on the realization of FO. The desired characteristics of membranes for FO would be high density of the active layer for high solute rejection; a thin membrane with minimum porosity of the support layer for low internal concentration polarization. Therefore, it was a prime solution to search for an appropriate semi-permeable membrane for the FO progress.Ionic liquids, as new novel green solvents, have many unique properties in comparison with traditional organic reagents, especially its application in the polymer. In this paper, the ionic liquids were used to treat the RO membranes. The results show that the membranes treated with 95% [BMIM]C1 lead to an increase in permeation flux in RO. The treated membranes were tested by SEM, AFM, contact angle and zeta potential.In this paper, in order to minimize the effect of the internal concentration polarization in FO, the fabric layers of the treated membranes are removed. Comparison of the membrane performance in the FO process were carried out for the untreated membrane, the membrane treated with ILs, untreated membrane without fabric layer and treated membrane without fabric layer. The results of the experiment demonstrate that the treated membrane without fabric layer achieves a water flux from an initial value 3.43 L/m2h to 8.42 L/m2h. In addition, the influence factors of the FO process with different semi-permeable membranes were also studied and discussed.