A cationic surfactant (dodecyl dimethyl benzyl ammonium bromide) modified spent mushroom (Tricholoma lobayense) was tested as a potential adsorbent for Cr (VI) removal from wastewater. The results showed that surface modification markedly improved the adsorption capacity. The monolayer maximum adsorption capacity calculated from Langmuir isotherm model was up to 43.86 mg/g at 25 degrees C. which was comparatively higher than that of most low cost sorbents. In batch studies, the combined effect of initial solution pH, initial Cr (VI) concentration and biomass dosage was investigated using response surface methodology (RSM). It was found that initial pH and adsorbent dosage exerted stronger influence on Cr (VI) removal than that of initial metal concentration. Furthermore, the results of ionic strength and desorption experiments indicated that the reversible electrostatic attraction played an important role in Cr (VI) uptake and the adsorption followed the anionic adsorption mechanism, which was evidenced by X-ray photoelectron spectroscopy (XPS) analysis in the study. (C) 2010 Elsevier B.V. All rights reserved.