Separation of dimethylformamide/water mixtures using sodium alginate, sodium alginate/poli(vinil alkol), sodium alginate/zeolite and sodium alginate/poly(vinyl alcohol)/zeolite membranes

In this study, separation of dimethylformamide (DMF)-water mixtures was investigated using pervaporation (PV), evapomeation (EV) and temperature difference evapomeation (TDEV) methods. Sodium alginate (NaAlg) based membranes were used in the separation. NaAlg was modified using poly (vinyl alcohol) and zeolite. Membranes prepared were characterized using Fourier transform infrared spectrometry (FTIR), differantial scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM).Experimental studies were majored on the effect of membrane thickness, operating temperature, membrane surrounding temperature and the feed composition on the permeation rate (flux) and the separation factor (selectivity).Experimental studies were carried out in three parts. In the first part; DMF-water mixtures were separated using NaAlg membranes by pervaporation. The optimum operating temperature and membrane thickness were determined as 40 oC and 60 ? m for %20 DMF (v/v) solutions.In the second part; NaAlg/PVA blend membranes were prepared. Using PV technique, optimum NaAlg/PVA ratio was determined as 80/20 (m/m) for 20 wt% DMF mixtures at 40 oC.In the third part of the study; NaAlg/zeolite and NaAlg/PVA/zeolite composite membranes were prepared and the membranes prepared were used for DMF-water separation by three different methods (PV, VP and TDVP). It was determined that the permeation rate increased, the separation factor decreased by using NaAlg/zeolite and NaAlg/PVA/zeolite composite membranes.It was concluded that the permeation rates and separation factors change depending on the method used for four different membranes. The highest separation factors were attained in the TDEV method. Whereas the flux values obtained in PV was found to be higher than in VP and TDVP methods.