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 (0.118 g dry weight) using three different initial concentrations of phosphate (C0=5, 50, and 100 mg PO43−-P/L) as well as environmentally relevant (eutrophic lakes) concentration of 100 μg PO43−-P/L. Approximately 97% of phosphate (C0=5 mg PO43−-P/L) was removed by the beads in 360 min from an aqueous solution. In 360 min, beads removed ∼76% of phosphate from water with C0=50 PO43−-P/L and ∼46% from water with C0=100 mg PO43−-P/L. For 100 μg PO43−-P/L, 80% removal was achieved within 20 min. The second-order reaction fit well for all the concentrations with reaction rate constants (k) of 0.076 and 0.2027 L/mg/min (C0=5 mg and 100 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 81–100% 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).