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In this study, the potential of fungi Aspergillus niger to remove cadmium, copper, lead and nickel ions from an aqueous solution was evaluated. Several pretreatment alternatives were investigated for enhancing metal removal capacity of live A. niger biomass. Cadmium, copper and lead biosorption capacity increased by more than 240% in comparison with live A. niger biomass upon sodium hydroxide, formaldehyde, detergent and dimethyl sulphoxide pretreatment. Nickel biosorption was reduced by all the pretreatment alternatives tested and live biomass exhibited highest nickel removal capacity. The reduction in nickel biosorption by sodium hydroxide pretreatment in comparison with live cells was approximately 45%, while improvements in cadmium, lead, and copper by sodium hydroxide pretreatment in comparison with live biomass was more than 240%. Therefore, it was decided to conduct further metal biosorption studies using sodium hydroxide pretreated biomass. The pH of the solution was found to strongly affect the degree of biosorption of cadmium, copper, lead and nickel ions on pretreated biomass. Biosorption of metal ions was inhibited at pH 3.0 or less, and sharply increased when pH of the solution was increased to 4.0. Biosorption of heavy metals further improved when pH increased from 4.0 to 6.0. Biosorption of heavy metals on pretreated biomass followed the Freundlich and the Langmuir adsorption models except at pH 4.0 for lead, cadmium and copper, and at pH 5.0 for nickel (at these pH values biosorption was unfavorable). Biosorption of lead, cadmium and copper on live biomass could not be described by the Freundlich and the Langmuir adsorption models, and in the case of nickel, both the models were applicable (based on the statistical significance of the model parameters estimated). The removal of cadmium, copper and lead ions by pretreated A. niger biomass was higher than the removals obtained using granular activated carbon (F-400). The pretreated fungal biomass was immobilized in a polymer polysulfone in the form of spherical beads and used in a fixed bed reactor to study the removal of heavy metal ions. The beads had an effective size of 0.718 mm and a surface area of 3.4 usd\rm m\sp2/g.usd These beads had a porous structure. Continuous column experiments indicated that these beads were able to remove cadmium, copper, lead and nickel ions from aqueous solution. (Abstract shortened by UMI.)
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