Abstract
Forward osmosis (FO) is the engineered term of the natural process of osmosis, where water transfers naturally across a semi-permeable membrane from a low salinity solution, called feed water (FW), towards a high salinity solution, called draw solution (DS). An important potential application of FO is the dilution of the concentrated rejects of reverse osmosis (RO) processes by the low salinity industrial or municipal wastewaters. However, this transfer of freshwater from the FW to the DS is accompanied with another mutual transfer of multiple organic and inorganic ions. The ions transfer may affect the quality of the produced water and exceed the required limits of specifications. Currently, there is lack of information in the literature describing multiple ions transfer in actual FO processes utilizing real solutions. Most of the literature published so far discusses transport phenomena using specific binary system solutions. This study aims to provide an informative assessment of the transfer of ions between the FO membrane sides using the reject of an RO desalination process as DS, and a mixed wastewater obtained from an industrial mining site as FW. The experiments were conducted at a constant temperature of similar to 24 degrees C and using a purpose made bench-scale osmotic cell. A symmetric cellulosic membrane, having a molecular weight cut-off of 3,500 Da, equivalent to a membrane mean pore diameter of about 2.8 nm, was utilized. The results show that the tested ions transferred at different rates across the membrane depending on their nature and concentration differences.