biosorption of cr (vi) ions from aqueous solution by the dead fungal biomass aspergillus niger

chromium is one of the major causes of environmental pollution. to remove heavy metal ions from water, microorganisms can be used. in this study, dead fungal biomass of aspergillus niger is used. the biomass was boiled in 0.5 n naoh solutions to increase the metal removal capacity of a.niger and was applied when the ph of wash solution was in the normal range. the optimum adsorption ph value observed for chromium (vi) ions was 2. in these experiments, the influence of contact time, ph, cr (vi) concentration, temperature, stirring speed, and different concentrations of biomass were evaluated. the results show that the experimental points fit both freundlich and langmuir models. meanwhile, the curves of both of them were drawn. in langmuir model, r2=0.9544 and in freundlich model, r2=0.992. the cr (vi) removal rate increases with the increase in temperature; that is, they are positively related. the removal rate of total chromium after 24 hours was %74.6. the results revealed that boiling biomass in naoh had a better effect on biosorption of chromium so that adsorption would increase by many times. during the study, the amount of toxicity decreased as cr (vi) was reduced to cr (iii). part of cr (vi) was also removed through surface adsorption.