Isotherms, kinetics and break through curve for sorptive removal of chromium from wastewater by activated sludge

Abstract

In the present investigations, activated sludge is used for removal of chromium in batch and continuous mode. It was observed that the sorption process followed Langmuir isotherm better than Freundlich isotherm (R2 = 0.95). The Freudlich model with R2 value above 0.9 suggests that the sorptive removal may involve physical and chemical adsorption with some multilayer sorption. Chromium uptake followed second order kinetics. The maximum adsorption capacity qe was observed to be 208.33 mg/g. The breakeven time and exhaustion time were determined for continuous operation. The non-availability of adsorbate at low flow rates play important role in delaying the break point time. Sludge age and initial concentration also affect the removal of chromium. The data follows the Thomas model with R2 value more than 0.9.