Relevant approach to assess the performance of sawdust as adsorbent of chromium (VI) ions from aqueous solutions

The biosorption of chromium (VI) ions from aqueous solutions by two adsorbents viz. mango and neem sawdust was studied under a batch mode. An initial pH of 2.0 was most favorable for chromium (VI) removal by both the adsorbents. The results obtained for the final concentration of chromium (VI) and chromium (III) at a pH range of 2-8 indicated that a combined effect of biosorption and reduction was involved in the chromium (VI) removal specially when the pH value is lower than 3. The maximum loading capacity was calculated from adsorption isotherms by applying the Langmuir model and found to be higher for neem sawdust (58.82 mg/g). Evaluation of experimental data in terms of biosorption kinetics showed that the biosorption of chromium (VI) by neem sawdust followed pseudo second-order kinetics. Therefore, the rate limiting step may be chemical sorption or chemisorption. The efficiency of this process was examined in using tannery wastewater contaminated with chromium (VI) ions in column mode.