Double Layer Graphene Oxide Loaded With Propylammonium Nitrate for Selective Adsorption of Inorganic Salts

Due to freshwater scarcity, desalination process gains more importance. Developing a green and environmentally friendly solution for extraction of the salts from the seawater becomes a major challenge nowadays. Among all desalination processes, membrane desalination is widely used. About 80 % of total desalination plants are based on reverse osmosis (RO) worldwide. However, RO desalination is considered to be costly owing to the short lifetime of the membranes and high replacement costs. Membrane fouling is one of the main causes of this limitation. Membrane inorganic fouling can be easily affected by calcium and magnesium inorganic salts. Hence, it is important to develop an efficient adsorbent used in RO pretreatment processes to address the problem of inorganic fouling. The great advantages offered by nanomaterials and green solvents allow the creation of new functional materials for inorganic salt adsorption. Ionic liquids (ILs) comprising of an organic cation and an organic or inorganic anion, exhibit superior characteristics and are used widely for different applications, including separation and extraction processes of salts and of several heavy metals in the seawater. However, ILs which have good solubility of inorganic salts are mostly hydrophilic. Therefore, cross-contamination of the pre-treatment water during the extraction process can occur. However, if ILs are supported on carbon nanostructures (CNS), as graphene oxide (GO) or other types of CNS, this can be avoided. As a result, this will reduce the operational costs of the plants by decreasing the amount of inorganic fouling in the membranes. Experimental findings showed that GO modified with IL can successfully adsorb CaCl₂, MgCl₂ and NaCl salts. Physical functionalization has been confirmed using thermal gravimetric analysis (TGA) and Raman Spectroscopy analysis. Moreover, leaching of IL from GO has been studied using Total Organic Carbon (TOC).