As the most important parameters affecting the biosorption, pH and temperature were studied in this paper in order to more completely understand their effects on chlorophenols' biosorption onto anaerobic granular sludge. Sorption isotherms of 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) at various temperatures were determined; the data of 4-CP could be simulated by Langnmir model, while the data of 2,4-DCP could only be reproduced by Freudlich equation. The uptake capacity of 4-CP and 2,4-DCP could reach 1.5 mg g(-1) and 5.04 mg g(-1) when 2,4-DCP concentration was 90 mg L-1 and 4-CP concentration was 107 mg L-1, respectively. 2,4-DCP was more strongly adsorbed onto the anaerobic granular sludge than 4-CP, which might be correlated with the numbers of chlorine substitute. The Experiments studying pH effects showed that the adsorption capacity of 4-CP and 2,4-DCP was quite pH dependent and increased with decrease in pH. (c) 2006 Elsevier B.V. All rights reserved.