Removal of CR (III) from model solutions by isolated Aspergillus niger and Aspergillus oryzae living microorganisms: Equilibrium and kinetic studies

Biosorption by fungi is a efficient method for removal of heavy metals which have been recently used by many researchers. The aim of the present work was the seeking and the isolation of sustainable microorganisms and their application for the removal of Cr (III) from simulated and real solutions. To isolate sustainable microorganisms, soil samples were taken from rawhide, tannery tanks and effluents discharged environment. Aspergillus niger and Aspergillus oryzae were the two types of isolated fungi from tanning factory environment. Fungal growth and chromium removal efficiency were studied as a function of maximum fungal tolerance to Cr (III) concentration, pH, temperature, contact time, agitation speed and nutrients addition. The optimal conditions for fungal growth were 30 h at pH 5.2, an agitation speed of 150 rpm and 30 degrees C in a medium containing yeast powder and di-hydrogen ammonium phosphate as nutrients. Maximum biomass concentration increased from 0.8 to 4 g/L for both fungi in the above mentioned conditions. Maximum fungal tolerance and chromium removal were found to be 600 mg/L and 95-98% of Cr (III). Equilibrium data were found to follow a Langmuir isotherm model and maximum sorption capacities were 185 and 208 mg/g for A. niger and A. oryzae, respectively. Experimental data was accurately fitted onto pseudo-second order kinetic model. Promissing results were also recorded on a real effluent, since in the above optimal conditions, chromium removal yields were 72 and 67% for A. niger and A. oryzae, respectively. However and owing to the high variability of the effluent, subsequent work is needed to confirm these positive results irrespective of the characteristics of the inlet effluent. (C) 2011 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.