Application of riverbed sand, a non-toxic substance for the removal of Cr(VI) for aqueous solutions has been investigated. Removal of Cr(VI) was dependent on initial concentration and removal increased from 43.2% to 74.3% by decreasing initial concentration from 7.5 x 10(-5) M to 1.0 x 10(-5) M at 25 degrees C, 1.0 x 10(-2) M NaClO4 ionic strength and 100 rpm. Higher removal was obtained at particles of smaller sizes of the adsorbent. Removal decreased from 74.3% to 40.7% by increasing temperature from 25 degrees C to 35 degrees C exhibiting exothermic nature of the process of removal. Thermodynamic parameters, namely change in free energy (Delta G degrees), enthalpy (Delta H degrees) and entropy (Delta S degrees), were calculated and were found to be -0.81 kcal mol(-1), -17.21 kcal mol(-1) and 56.94 cal mol(-1), respectively at 25 degrees C. pH of the solution has pronounced effect on the removal and higher removal was obtained in acidic pH ranges, maximum (74.3%) being at 2.5 pH. (C) 2007 Elsevier B.V. All rights reserved.