The capacity and mechanism with which nonviable Aspergillus niger removed the textile dye, C.I. Direct Blue 199, from aqueous solution was investigated using different parameters, such as initial dye concentration, pH and temperature. In batch experiments, the biosorption capacity increased with decrease in pH, and the maximum dye uptake capacity of the biosorbent was 29.96 mg g(-1) at 400 mg L-1 dye concentration and 45 degrees C. The Langmuir and Freundlich models were able to describe the biosorption equilibrium of C.I. Direct Blue 199 onto the fungal biomass. Biosorption followed a pseudo-second order kinetic model with high correlation coefficients (r(2) > 0.99). Thermodynamic studies revealed that the biosorption process was successful, spontaneous and endothermic in nature. (C) 2009 Elsevier B.V. All rights reserved.