Removal of heavy metals from aqueous solutions using immobilized fungal biomass in continuous mode

Fungal microorganisms are being increasingly studied for the removal of heavy metal ions from aqueous solutions. The fungal biomass in powdered form is commonly used in metal adsorption studies. The use of powdered biomass can pose problems in its application in batch and continuous (column) type reactors treating wastewaters because fungal biomass becomes soft in contact with water, has low density, is difficult to separate from treated wastewater and fixed bed reactors using it can easily clog. Immobilization of fungal biomass in a solid polymer matrix will facilitate their application in industrial systems treating heavy metal bearing wastewater. In this study, A. niger biomass was immobilized in a polysulfone matrix. For this purpose an immobilizing unit was fabricated to produce an immobilized biomass matrix of spherical shape. The beads were found to have a porous structure. Majority of the beads had particle sizes in the range of 2.00 to 0.841 mm. The biomass beads packed in a column were able to remove metal ions such as cadmium, copper, lead and nickel. The breakthrough data obtained for cadmium, copper, lead and nickel was adequately described by the Thomas adsorption model. The amounts of metal adsorbed per unit weight of beads for cadmium, copper, lead and nickel were 3.60, 2.89, 10.05, and 1.08 mg/g respectively. The adsorbed metal ions were easily eluted from the column using 0.05N nitric acid. These beads may be easier to use in industrial wastewater treatment systems in comparison with the fungal biomass powder.