Batch and continuous experiments were performed for the sorption of distillery spent wash onto fly ash particles. The Freundlich and pseudo-second order equation were found to fit the equilibrium data perfectly. The Weber-Morris intraparticle diffusion isotherm equation was used to predict the sorption mechanism and the predicted equation for 10% dilution of spent wash sorption is q(t) = 11.1344(t)(0.5) + 33.304. The optimization using 2(3) factorial design of experiments provides optimal removal of color of 93% for dilution (5%), dosage of adsorbent (10g) and temperature (293 K). The actual color removal at optimal conditions was 92.24%, confirms close to the factorial design results. The complete error analysis using six non-linear error functions: Chi-square(chi(2)); sum of square errors (SSE); composite fractional error function (HYBRD); derivative of Marquardt's percent standard deviation (MPSD); average relative error (ARE); sum of absolute errors (EABS) were calculated. Free energy of adsorption at 293 K (Delta G(0) = - 1574.67J), enthalpy change (Delta H-0 = -32.5487 KJ) and entropy change (Delta S-0 = 105J/K) were calculated to predict the nature of adsorption. Adsorption studies in a packed column were evaluated using Bed depth service time model, Thomas model and Adams-Bohart model. (C) 2008 Elsevier B.V. All rights reserved.