Pervaporation performance of crosslinked composite membranes of clinoptilolite (Clt) and sodium alginate (NaAlg) has been studied for the separation of dimethylformamide (DMF)/water mixtures. The effects of feed composition (0-100 wt. %) and operating temperature (20-50 degrees C) on the permeation rates and the separation factors were investigated. The observed flux values of composite membranes were much higher whereas the selectivities were lower than the plain NaAlg membranes. The highest permeation rate of 2.3 kg/m(2)h and selectivity of 23 was exhibited by the composite membranes depending on the operating conditions and Clt loading. In addition sorption-diffusion properties of the composite membranes were investigated at the operating temperatures and the feed compositions. It was found that the sorption selectivity was dominant factor for the separating of DMF/water mixtures for both types of membranes. The membranes were characterized by Fourier transform infrared spectrometry (FTIR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM).