Metal Ions Removal from Contaminated Water Using Membranes Functionalized with Ionic Liquids

The present work studies the efficiency of new innovative quaternized polysulfone (PSFQ)/ionic liquid (IL) membranes in the treatment process of water containing cadmium ions (Cd(II)). The design and development of the polysulfone membranes with morphology tailored by the use of ILs (Cyphos 101 IL and Aliquat 336) was based on the rheological study of the casting solutions that dictated the optimal compositions of ILs and facilitated the preparation of the membranes for performance tests. Thus, according to the variation of the rheological functions obtained (G′, G″), it was demonstrated that Aliquat 336 has better compatibility with PSFQ, facilitating the workability of the solution and improving the final properties of the membranes relative to Cyphos 101 IL. However, the casting solutions consisting of 5 wt.% Ph-IL and 15 wt.% Am-IL content produce membranes with superior physico-chemical properties. Also, the surface chemistry and morphology analysis of the membranes obtained were investigated in order to understand the relationship between the PSFQ and ILs, as well as their surface properties, as indicators for their future applications. Additionally, the results obtained from the kinetic studies regarding Cd(II) removal from aqueous solutions and the amount of Cd(II) accumulated onto the membranes showed that the ILs enhance the filtration efficiency of the membranes studied and underlined the positive effect of IL in the structure of the quaternized polysulfone membranes. A content of 15 wt.% Aliquat 336 in PSFQ membranes shows the best properties for Cd(II) removal from aqueous solutions; the maximum amount of Cd(II) accumulated on the membrane studied was 3300 mg/m2. This behaviour was maintained for two cycles of washing/filtration, and then the efficiency decreased by 20%. The results obtained showed that the membranes functionalized with ionic liquid could be used efficiently in the treatment of water containing trace concentration of cadmium.