The efficiency of photocatalytic reactions was limited by the wide band-cap of TiO2 and the high degree of electron-hole recombination inherent in photocatalytic process. aswell as by the limited adsorption capability of photocatalysts. In order to increase the overall efficiency. the surface of nanometer size TiO2 was simply and fast modified by chemical adsorption in saturated solution of salicylic acid. A stable. light yellow surface complex was formed quickly. which has obvious absorption in the region from 320 to 420 run. Through surface modification. the adsorption efficiency of 4-nitrophenol by TiO2 was enhanced from 42 to 84%. The photocatalytic efficiency was tested on the degradation of 4-nitrophenol. The influences of catalyst and its dosage. pH value. and 4-nitlophenol concentration on the degradation were investigated. Under such photodegradation conditions as initial pH 4.0, 4-nitrophenol 5 mg l(-1), catalyst 100 mg. and irradiation time 160 min with 160 W high-pressure mercury lamp, the degradation efficiency of 4-nitrophenol by TiO2 was increased from 39.5 to 79.3% after surface modification. and furthermore. the degradation efficiency could be enhanced to 91.1% if the concentration of 4-nitrophenol was not more than 1 mg l(-1). Compared with the pure TiO2 surface modification led not only to improve the surface coverage of 4-nitrophenol. but also to increase the light utilization. Both of these factors were crucial for the photocatalytic activity of heterogeneous photocatalysis. especially for photodegradation of aromatic pollutants. (c) 2005 Elsevier B.V. All rights reserved.