Sorption of distillery spent wash onto fly ash: Kinetics and mass transfer studies

Adsorption studies for sorption of distillery spent wash onto fly ash particles were studied in both batch and packed column. Equilibrium data were fitted to the Sips, Elvoich and Dubinin–Radushkevich, Redlich–Peterson, Langmuir four types and Ho's four types of pseudo-second-order kinetic models. The complete error analysis was done to determine the best isotherm model using six different non-linear error functions: chi-square (χ2), sum of square errors (SSEs), composite fractional error function (HYBRD), derivative of Marquardt's percent standard deviation (MPSD), average relative error (ARE), sum of absolute errors (EABS) and linear regression correlation coefficient (r2). The Biot number was determined using internal mass transfer coefficient and the external mass transfer coefficient estimated using Mathews and Weber model and Furusawa and Smith model. The Biot number estimated provides that external film transfer controls the mechanism of sorption of spent wash onto fly ash. Packed column adsorption was analyzed using Thomas model and Adams–Bohart model for different flow rates of studies.