Thermostable asymmetric ultrafiltration (UF) membranes were prepared from poly(phthalazinone ether amide) (PPEA), a novel polymer with excellent thermal stability. The effects of polymer concentration, the type and amount of additive, evaporation time, the temperature of the coagulant bath on the morphology and performance of the membranes were studied in detail. Ultrafiltration membranes with rejection capacity in the range of PEG2000-PEG20000 and with pure water flux of 43-695 L m(-2) h(-1) were obtained, when tested at 25 degrees C, 0.1 MPa. PPEA UF membrane was applied in the desalination-concentration experiment for the raw products of four newly synthesized dyes. The flux increased obviously as the operation pressure or temperature enhanced, while the rejection for dyes was kept over 99.7% at the same time. The dye purification experiment was effectively accomplished at 0.3 MPa, 80 degrees C. Only after three rounds of experiment, about 210 min, the salt mixed in dye solutions was fully removed. During five rounds of experiment at 80 degrees C, the rejection for dyes was constant and kept over 99.7%. The initial flux of the fifth round was about 260 L m(-2) h(-1), which was only 10 L m(-2) h(-1) lower than that of the first round. (c) 2008 Elsevier B.V. All rights reserved.