Experimental and Mathematical Modelling of Breakthrough Curves of Fe (II) on Immobilized Biomass in a Packed Column

Metal contamination of aquatic ecosystem in and around the Witwatersrand basin has been exacerbated by an overflow of acid mine drainage from spent mines.  Physical and chemical treatments are conventional methods widely used in heavy metal removal, however biological methods have proven to be more efficient, cost effective and environmentally conscious. The present work studies the use of fresh-water green microalgae Desmodesmus sp. immobilized in a calcium alginate matrix for heavy metal removal.  The adsorption performance of immobilized algae beads (IAB) in a continuous flow from aqueous solution was investigated in a packed column.  The packed column experiments were carried out as a function of bed height of IAB and alginate beads without algae (ABWA).  The total adsorbed quantities, equilibrium uptakes and total removal percentages of Fe (II) ions were determined by evaluating the breakthrough curves obtained at different bed heights.  The steepness of the breakthrough curve determined the extent to which the capacity of the adsorbent bed can be used.  The total quantity of Fe(II) ions adsorbed in the column as calculated from trapezoidal numerical integration was found to be 1.6 mg; 33.6 mg and 116.1 mg for ABWA (height 26 mm), IAB (height 26 mm) and IAB (height 82 mm), respectively.  It was found therefore, that the amount of Fe (II) ions adsorbed in the column was affected by the presence of algae in alginate beads and the increase in bed height of IAB. Thomas; Yoon-Nelson and Adams-Bohart models were used to analyse the experimental data and model parameters were evaluated.  Correlation of the experimental breakthrough curves with model predictions was observed.  The root mean square error (RMSE) model will be used to measure accuracy of the results.