Synergistic effect of amino-acids and metal salts as draw solutions to enhance the performance of fertilizer-drawn forward osmosis†
In the present study, the osmotic properties of blended amino-acids–metal-salts fertilizer draw solutions, and their forward osmosis (FO) performances were investigated. Considering the different types of amino-acids–metal-salts, the blending of arginine with ZnCl2 solution in the molar ratio of 1 : 6 could lead up to 3.0 and 8.3 times higher osmotic pressure and water flux (i.e., 93.89 bar and 29.57 LMH), respectively, compared to the sum of their individual values. Furthermore, a very little reverse solute flux was noticed using ZnCl2–amino-acids draw solutions. As an effect of solute–solvent interaction, the formation of the novel structure of amino acids with metal salts could enhance the osmotic pressure, providing high water flux and low inverse diffusion of the solute. The desalination of Caspian Sea water was also successfully tested using arginine–ZnCl2 fertilizer draw solution. Therefore, the fertilizer-based draw solutions can present great potential in different applications of the FO process, due to their relatively high water flux and no need for recovery.