BIOLOGICAL REMOVAL. OF CHROMIUM FROM TANNERY WASTEWATER

Abstract

The removal of chromium(VI), a highly toxic metal causing environmental pollution to wastewater, was studied in the present work. The two low cost biosorbents which were prepared using bengal gram husk and wheat husk, are used for the removal of chromium(VI). All the experiments were carried out in batch process with chromium(VI) synthetic wastewater and tannery wastewater. The whole thesis work was divided into two parts, in the first part, the chromium(VI) removal from synthetic wastewater was carried out under various treatment conditions of pH, biosorbent dosage, contact time and effect of temperature. In the second part, the optimum conditions of synthetic wastewater was applied to tannery wastewater to remove chromium(VI). Approximately, 98% of chromium(VI) was removed at pH 2 within 5 hours, temperature 30±1°C, and dosage of 3 g, bengal gram husk and initial chromium concentration of 20 mg/L. Using wheat husk 74% chromium(VI) removal was possible with initial chromium concentration of 20 mg/L, at pH 2, temperature 30±1°C and biosorbent dosage of 2 g. At _optimum conditions' of tannery wastewater, 57.94% of chromium was removed using bengal gram husk and 33.72% chromium was,. removed by wheat husk. Bengal gram husk and Wheat husk were characterized by Field Emission Scanning Electron Microscopy (FE-SEM), Thermogravimetric Analysis(TGA) and• Fourier Transform Infrared Spectroscopy (FTIR). The biosorption data were fitted well the Langmuir model with a higher R2 value (0.98) compared to that of the Freundlich model (0.95) describes Cr(VI) biosorption onto bengal gram husk better. But on wheat husk the R2 (0.98) value are- high therefore the wheat husk follows the Freundlich model.. On the basis of present study, it can be concluded that bengal 'gram husk and wheat husk have higher chromium biosorption- capacities.