This study describes the rejection of acid black 194 dye using a DL nanofiltration membrane. Membrane experiments were conducted in a cross-flow system. Effects of membrane pressure (5, 10, and 15 bar), feed pH (3, 7, and 10), feed temperature (25, 35, and 45 degrees C) and dye concentration in the feed solution (50, 500, and 1000 mg/L) on the membrane performance were investigated. The surface morphologies of membranes were investigated using scanning electron microscopy (SEM). The results indicate that the DL membrane has satisfactory average dye rejection (99.72 +/- 0.140%) at operating pressure of 5 bar, 1000 mg/L dye concentration, 25 degrees C feed temperature and feed pH = 7.