Removal of Congo Red from an aqueous solution by fungus Aspergillus niger

Biosorption is becoming a promising alternative to replace or supplement the present dye removal processes from dye wastewater. In this study, removal of an anionic disazo direct dye, Congo Red, from an aqueous solution by biosorption on dead fungus, Aspergillus niger, was investigated. Pretreatment with NaHCO3 was found to be the most effective with a biosorption capacity of 14.72 mg/g compared with 12.10 mg/g of living biomass for Congo Red. Batch pH, kinetic and isotherm studies were conducted to evaluate the biosorption capacity of NaHCO3 pretreated biomass. The initial pH of the dye solution strongly affected the chemistry of both the dye molecules and fungal biomass in an aqueous solution. The effective pH was 6.0. Kinetic studies showed that the biosorption of Congo Red on fungal biomass was a gradual process. Equilibrium was reached in 42 h. The kinetic studies indicated that Lagergren first order and Ho et al. pseudo second order rate equations were able to provide a realistic description of biosorption kinetics of Congo Red. Isotherm studies indicated that biosorption of Congo Red on A. niger biomass did not follow the Langmuir, Freundlich and BET models, but followed the Radke-Prausnitz model. The adsorption capacities for granular activated carbon and powdered activated carbon were 13.80 and 16.81 mg/g, respectively, compared with an adsorption capacity of 14.16 mg/g for fungal biomass. This study showed that it is possible to develop systems for dye removal using A. niger biomass which occurs as a byproduct in waste streams of fermentation industries. (C) 2002 Elsevier Science Ltd. All rights reserved.