Biopolymer Beads for Aqueous Phosphate Removal: Possible Applications in Eutrophic Lakes

Abstract

Novel iron (Fe) cross-linked alginate (FCA) beads were used for phosphate removal from synthetic water, lake water, and wastewater. Batch experiments were conducted with the beads (.118 g dry weight) using three different initial concentrations of phosphate (C=5, 5, and 1 mg PO43−-P/L) as well as environmentally relevant (eutrophic lakes) concentration of 1 μg PO43−-P/L. Approximately 97% of phosphate (C=5 mg PO43−-P/L) was removed by the beads in 36 min from an aqueous solution. In 36 min, beads removed ∼76% of phosphate from water with C=5 PO43−-P/L and ∼46% from water with C=1 mg PO43−-P/L. For 1 μg PO43−-P/L, 8% removal was achieved within 2 min. The second-order reaction fit well for all the concentrations with reaction rate constants (k) of .76 and .227 L/mg/min (C=5 mg and 1 μg PO43−-P/L, respectively). The maximum phosphate sorption capacity was found to be ∼79 mg PO43−-P/g of dry beads. No change in phosphate removal was observed in the presence of Cl−, HCO3−, SO42−, NO3−, and natural organic matter (NOM). To investigate the feasibility of using the FCA beads in a real-life situation (e.g., in eutrophic lakes), actual lake waters (11–69 μg PO43−-P/L) were used and 81–1% phosphate removal was observed in 24 h. Results presented here demonstrate the potential for the use of the FCA beads for the reclamation of eutrophic lakes (removal of excess of phosphate).