Two different forms of sawdust, viz., acid-activated sawdust in powder form (ASDP) and surface-modified sawdust in bead form (SDCCB) were prepared and used as adsorbents for the removal of chromium(VI) from aqueous solution. Batch experiments were carried out to investigate the potential efficiency of the two forms of sawdust to remove Cr(VI) ions from aqueous solution as a function of the initial Cr(VI) concentration, pH, contact time, agitation speed and temperature. Based on Langmuir isotherms, the maximum adsorption capacity was found to be 45.5 mg/g for ASDP and 125 mg/g for SDCCB. Equilibrium was found to be attained at about 120 min and 150 min respectively for ASDP and SDCCB. Various isotherms and kinetic models were fitted to describe the solid–solute interaction and the activation parameters were evaluated in both the cases. Based on the results, it has been suggested that the sorption of Cr(VI) on surface of both sawdust adsorbents is an endothermic, a spontaneous and a nonspecific-chemisorption process.
Sawdust, Adsorption capacity, Adsorption isotherms, Kinetics, Thermodynamic parameters