Batch Cr(VI) removal by polyacrylamide-grafted sawdust: Kinetics and thermodynamics

Batch sorption studies have been carried out to determine the effect of adsorbent dose, initial sorbate concentration and pH on the adsorption of Cr(VI) on polymer-grafted sawdust. The process was found to be pH, temperature and concentration dependent. An empirical relationship has been obtained to predict the percentage Cr(VI) removal at any time for known values of sorbent and initial sorbate concentration under observed test conditions. The effect of diverse ions has been studied and it is found that there is very little effect on the sorption of Cr(VI). The process was found to be exothermic with a maximum adsorption of 91.0% at 30°C for an initial concentration of 100 mg l−1 at pH 3. The process follows first-order kinetics and the data fits the Freundlich adsorption isotherm. Thermodynamic parameters were also evaluated. Desorption studies confirmed that adsorbent can be effectively regenerated using 0.2 M NaOH and 0.5 M NaCl and can then be reused.