Toxic effects of omega chrome red ME and its treatment by adsorption

Toxic effects of Omega Chrome Red ME, a popular textile dye, on the nitrogen fixing cyanobacterium Nostoc calcicola were studied. The growth of N. calcicola was found to be suppressed at 10 and 20 mg liter-1 initial concentrations of dye, whereas a low initial concentration of 5 mg liter-1 slightly favors growth. Removal of the dye was carried out by adsorption using some cheap and unconventional adsorbents like coal, fly ash, wollastonite, and china clay. It has been observed that, in all cases, the low adsorbate concentration, the low temperature, and an acidic medium favor the dye removal process. The process of uptake follows first-order adsorption rate expression and obeys Langmuir's model of adsorption. The removal process is also partially diffusion controlled. Thermodynamic and pH studies were run to explain the results.